Tirtha soil final

SOIL
MANAGEMENT,
CONSERVATION
AND
ENVIRONMENTAL
SCIENCE
HANDOUTS FOR
I. Sc Ag 2nd
Year
Prepared By:-
Tirtha Raj Paudel
Suraj Bharati

SOIL MANAGEMENT, CONSERVATION AND ENVIRONMENTAL SCIENCE]
Prepared By:-
Tirtha Raj Paudel & Suraj Bharati
1
ACKNOWLEDGEMENT
“A complete hand note on Soil Management, Conservation and Environmental Science” is written for
the CTEVT students of ISC. Ag, 2nd
year, which is strictly based on CTEVT syllabus. I try to make this
note as thinking that this note will be very helpful to you for the preparation of exam. This note covers
all contents present in syllabus .This is short and rationally made so that it will be ease to understand
and can learn quickly. . The pictures and tables included here make you more comfortable, which is easy
to memorize.
This lecture note is synthesized from different soil books of different Universities of the world and
B.Sc.Ag notes.
We would like to express my deep sense of gratitude and sincere appreciation to my parents Krishna
Prasad Paudel and Hum Kumari Sharma and my beloved wife Mina Devi Dhakal(paudel)and Brother
Pradip Phuyal and Subash Dhakal under their coordination and inspiration, this note is on your hand.
I would also like to thanks to all the friends Kusum Dhakal(Phuyal), Suraj Bharati,Saroj Bhandari,
Saroj Dahal ,Bikash Khanal,Jagdish Chandra Dhami, Kusal Paudel and all IAAS friends who had
helped me directly or indirectly during this period.
I have tried to minimize the mistakes. If encountered any mistake I will be very sorry for that. I sincerely
acknowledge various authors and publisher, to whom I have referred to in the text. However sole
responsibility goes to me for any errors.
Feedbacks and suggestions are highly appreciated at Prakashtirtha@gmail.com
Prepared

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SYLLABUS
Credit hours: 3+ hours/week Full Marks: 100
Total hours: 160 hours
Theory: 96 hours Practical: 64 hours
Course: Soil Management, Conservation and Environmental Science
Unit 1: Introduction to Soil Theory Hours : 5
Define soil, Definition, concept and uses of soil, Soil as a natural dynamic body and medium for plant
growth and Soil- plant relations
Unit 2: Rock and Minerals Theory Hours : 5
Rock and minerals, weathering of rocks, Physiographic units of Nepal in relation to soil and Evolution
of earth
Unit 3: Soil Properties Theory Hours: 22
Physical, Soil texture, Soil structure, Bulk density, particle density, porosity and soil color
Chemical, Soil reaction: soil pH, soil acidity and liming, Saline-sodic soils and their management
Soil colloids: Organic and inorganic, Cation and anion exchange
Biological ,Organic matters and their importance ,Soil flora and fauna, Organic manures and their
properties ,Preparation of organic manures (FYM, compost, green manure) ,Bio-fertilizers and biogas
Unit 4: Plant nutrition Theory Hours: 20
Essential plant nutrients: Primary, Secondary and Micronutrients
Sources of nutrients, Functions and deficiency symptoms and Soil fertility evaluation
Visual symptoms, Plant tissue analysis, Biological methods
Soil tests
Unit 5: Fertilizers Theory Hours: 12
Composition, uses and behavior in soil
Nitrogenous fertilizers, Phosphatic fertilizers, Potassic fertilizers
Integrated nutrient management, Concept and relevance, Components and Management options
Soil fertility problems in Nepal and their management

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Unit 6: Soil conservation Theory Hours: 16
Definition of soil erosion and its causes
Types of soil erosion by water, Consequences of soil erosion in Nepal, Fertility loss and land
degradation
Flood, landslide and natural hazards: On-site and off-site effects, Socio-economic effects
Soil erosion control measures
Agricultural Land: Conservation tillage, Mulching, Terrace cropping, Contour farming, Strip or cover
cropping
Forest and rangeland: Afforestation, Controlled grazing, Bio-engineering, Engineering
Use different Equipments and Machineries, Power Tiller and Cultivator
Unit 7: Nature of environmental studies Theory Hours: 8
Definition, Scope and Importance, From Unsustainable to Sustainable development, Organic farming
Need for public awareness and Forest Resources: Use and over-exploitation, deforestation
Water resources: Use and over-utilization of surface and ground water, floods, drought.
Land resources: Land as a resource, land degradation, man induced landslides, soil erosion and
desertification.
Role of an Individual in Natural Resource Conservation.
Equitable use of resources for sustainable development
Unit: 8 Environmental Pollution Theory Hours: 8
Definition, Types (Major)
Cause, effects and control measures of: Air pollution, Water pollution, Soil pollution
Solid waste Management: Causes, effects and control measures of urban and industrial wastes.
Role of an individual in prevention of pollution.
Water conservation, Rain water harvesting, Watershed management
Climate change, Global warming, Acid rain, Ozone layer depletion.

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UNIT: 1
Definition, Concept and uses of soil
Soil as a natural dynamic body
Soil as a medium for plant growth, Soil- plant relations.
Soil science: It is the study of soil as a natural resource on earth surface including: soil
formation, classification & mapping; physical, chemical, biological, &fertility properties of soils;
&these properties in relation to use & management of soils.
Branches of soil science:
i. Pedology: It deals with soil formation, chemistry, morphology &classification of soil and study of
soil in its natural setting.
ii. Edaphology: It deals with the study of influence of soil on organisms and study soil in relation to
plants.
SOIL
The term soil is derived from the Latin word 'Solum' meaning floor. Soil is a dynamic natural body
on the surface of the earth with different composition and quantities of inorganic and organic matters
having different physical, chemical and biological activities and medium for plant growth.
SOIL
S=surface of earth
O= organic matter
I=inorganic matter
L=living beings
Soil is a dynamic natural body on the surface of the earth in which plant grow, composed of mineral
and organic materials and living forms.
Soil is defined as the unconsolidated/loose surface of the earth formed by the process of weathering
of rocks and minerals.
NOTE: Father of soil science: Russian Scientist V.V. Dokuchaev.
Factors of Soil formation
Soil = f (Cl, O, R, P, T)
• Climate (Cl), Organisms (biotic activities), Topography/ Relief, Parent materials, and Time are
factors of soil formation.
CONCEPT OF SOIL:
Concept depends on purpose of its use that a person have.
 Construction engineer considers soils as earthen material which support foundations of road,
bridges and other physical infrastructures.
 Ecologist: habitat of living being and part of the ecosystem and conserved as was in nature.
 Farmer considers soil as field material in which they can grow crops. It is a medium for their
food, cloth and shelter. Bases of life.
 Gardener- dark, crumbly material to prepare seedbed.

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 Mining engineer- Soil as means of oil formation and storage.
USES OF SOIL:
 Construction materials
 Place to construct building, road
 Reservoir of plant nutrient and water
 Habitat for all living beings
 Decomposition of waste
 Detoxification of Harmful chemicals
 Storehouse of natural gas and natural oil.
 Natural filter for water
SOIL AS A NATURAL DYNAMIC BODY:
Soil form by disintegration, decomposition & re-cementation of rocks, minerals & OM
Soil as natural body can be justified based on its components. All components are derived from
natural processes by action of Natural forces on natural body.
 SOM is derived from plants, animals & MOs-grow in nature.
Most of the plants and some microbes are autotrophic and grow
in the nature synthesizing their food in the presence of light.
Animals and microbes derive their food from plants. Plants,
animals and microbes grow in the nature.
 Soil air and soil water occupy half volume of soil are also
natural gifts.
 Soil mineral formed by weathering of rocks & minerals (natural bodies) under influence of
natural forces (climate, topography, biological activities & time).Soil a tremendous biological
laboratory as different organisms & MOs inhabit in soil.
Thus, soil as a whole is a natural creation or itself is a natural body.
Soil as Dynamic body
It can also be justified on the basis of soil components.
 Soil Organic Matter
Green plants & some microbes are autotrophic (grow in soil & synthesize their food using soil,
atmospheric air & sunlight).Animal derive food from plants & some microbes (heterotrophic) derive
their food from dead animals & plants. All these are components of soil OM. Amount & forms of
Organic matter is changing over time.
 Soil air
Composition of soil air varies with season, moisture & climatic conditions, composition & amounts
of OM present in that soil, soil microbial population & activities for e.g. Increase in OM increase soil
microbial activities, increase CO2 content atm. with depletion in O2 content.
 Soil moisture:
It varies with season. Under prolonged draught, soil water level reduces in pores which are occupied
by air. After irrigation/rain, soil water occupies more than the soil air.

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 Soil inorganic matter
It is formed by weathering of rocks & minerals. Weathering not only changes nature & properties of
rocks, minerals but also releases nutrients to soil. Weathering brings physical, chemical & biological
changes in soil inorganic matters. Thus, soil inorganic matter is also dynamic.
Thus, soil is dynamic body.
MEDIUM FOR PLANT GROWTH:
Soil is the heterogeneous mixture of air, water, organic, inorganic matters and living beings found on
the surface of the earth. It is the place of plant establishment and source of plant nutrients for their
growth and development.
 Soil is the habitat of microbes and releases nutrients to the plants
Soil is the habitat for different microorganism like Rhizobium, Nitrosomonas, Nitrobacteria and
other useful and harmful microorganism. Rhizobium and some other symbiotic free living bacteria
are capable to assimilate atmospheric nitrogen to the plant and soil by biological means. Some soil
microorganisms are responsible in organic matter decomposition and release different nutrients from
organic matter.
 Soil is the source of nutrient element to the Plants
Decomposition of organic matters release nutrients like N, P, S,K and weathering of rock and
minerals releases nutrients elements like Fe, Mn, Zn, Cu, Mo, B, Cl etc.
 Soil is the store house to retain and release water.
Soil water is required to dissolve nutrients present in the soil and oxygen is required for root and
microbial respiration. Below critical level of oxygen present in the soil air, there will be reduced crop
growth or death of plants. Soil water and soil air are important for growth and development.
 Soil detoxifies chemicals applied and reduces their negative effect.
Soil microbes and microbial secretions decompose toxic chemicals applied to the soil like herbicides,
pesticides and change their properties to non- toxic forms with different Physio-chemical and
enzymatic changes
 Soil controls temperature fluctuations
Soil water, soil air and organic matters are responsible to control temperature extremes. Evaporation
of soil water reduces soil temperature and protects crops from high temperature injuries. At high
temperature, soil air become hot and hot air being lighter come out from the soil and cold air pass
into the empty space. Decomposition of soil organic matter release heat to the soil and soil
temperature increase.
 Soil provides physical support to the plant
Plant roots hold soil mass and make the plant able to stand in its upright position. Thus soil provides
physical support to the plant by anchoring the root system.
SOIL AND PLANT RELATIONSHIP
How soil support pants and how plant support to soil. Soils have unique relation with plant, which
make soil as medium for plant growth.

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• The supports provided by soil to the plants include
1. Physical support to the plant:
It provides physical support & anchorage to the root system so that the plant doesn‘t fall down.
Roots penetrate the soil & spread vertically & horizontally, holding the plant upright & extracting
nutrients & water.
2. Reservoir of nutrient elements
Soil is the storehouse of the plant nutrients
• C, H, O, N, P, K, Ca, Mg, S are required in the largest quantity (Macronutrients).
• C, H & O constitute 95-99% of plant-structural elements.
• N, P, K are required in relatively larger quantity i.e. primary nutrients.
• Ca, Mg & S are secondary nutrients
3. Reservoir of water/ water retention
Soils also hold water in the pores that the plants can use .Aeration/ root respiration
Plant roots need oxygen & if the soil is water logged for too long, most plants will suffer from O2
deficiency. Thus, the balance between the amount of air & the amount of water in the soil is
essential to plant health.
4. Temperature moderation
Soil moderates temperature fluctuations. The insulating properties of soil protect the deeper portion
of root system from the extremes of hot and cold that often occur at the soil surface.
5. Protection from toxins
A good soil protects the plants from toxic conc. of such by ventilating gases, decomposing or
adsorbing organic toxins, or by suppressing toxin producing organisms
What services do plants provides to soil???
• OM
• Inhabitants for the soil organisms
• Root exudates
• Soil formation processes
• Others
i. Roots bind soil particles…….prevents soil erosion
ii. Nitrogen fixation
iii. Makes soil porous
iv. Provides OM-source of plant nutrients
v. Recycles plant nutrients
vi. Weathering of rocks and minerals
Note. Some common terminology used in soil science
Pedological approach
The ‗Pedology‘ derived from a Greek word ―pedon‖-mean soil or earth. It is the study of a pedon. It
is the Science, which consider soil as natural body and studies its origin, formation, classification &
description. It does not focus primarily on soils immediate practical use. Pedological findings may be
useful to highway & construction engineers as to/than farmers.
Edaphological approach
It is derived from Greek word ―Edaphos‖ -means soil or ground and consider soil as medium for
plant growth and studies soil properties relation to plant production & soil productivity. So it concern
soil as a habitat for plants

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Soil fertility
It is the capacity of soil to provide all essential elements for specific crop production in an easily
available form and in proper proportion. All fertile soil may not be productive soil because it is
affected by soil pH, structure, texture and water content.
Soil productivity
It is the capacity of soil to produce maximum yield of a specified plant/crop or a sequence of crop
under specified system of management.
Differences between soil fertility and soil productivity
Soil fertility Soil productivity
It is the capacity of soil to provide all essential
elements for specific crop production in an
easily available form & in proper proportion.
It is the capacity of soil to produce maximum
yield of a specified plant/crop or sequence of
crops under specified system of management.
It deals with nutrient status of the soil only.
It is combined effect of all production factors.
All fertile soils may not be productive due to
draught, water logging, pH, microorganisms etc
All productive soils must be fertile.
It can be evaluated by soil test in the laboratory.
It cannot be evaluated by soil test in the
laboratory.
SOIL PROFILE
The vertical section of soil showing the various layers from the surface to the unaffected parent
material is known as soil profile.
The soil profile develops over time as the result of the weathering of minerals and deposition of
organic matter. The soil profile extends from the soil surface to the parent rock material.
IMPORTANCE OF SOIL PROFILE:
1. The soil profile is an important tool in nutrient management, crop selection etc.
2. By examining a soil profile, we can gain valuable insight into soil fertility.
3. Soil profile provides us the information through which we can begin to predict how a soil
performs under certain nutrient management conditions.
SOIL HORIZON
A horizontal layer of soil or soil material which is parallel to the land surface having different
properties such as color, structure, texture, consistence, and chemical, biological, and mineralogical
composition that makes it differs from adjacent layers.
There are five master horizons and they are:
1. O horizon
It is organic horizon which is formed at the top above the mineral soil. It is composed of organic
materials (dead plants & animal residues) in different stages of decomposition. O horizon is
predominantly found in forested regions (Forest Floor); generally absent in grass land.

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2. A horizon
It is upper most mineral horizon found below o horizon. It contains enough partially decomposed
(humified) OM to give the soil a color darker than that of the lower horizons.
3. E horizon
It is the maximum leaching or eluviation horizon. It is lighter in color than adjacent horizons.
4. B horizon
It is the Horizon below O, A and E horizon. B horizons are the layers of maximum accumulation of
Fe and Al oxides.
5. C horizon
Horizon consist unconsolidated materials underlying the soil solum (A & B horizon) and less
weathered horizon.
Differences between Surface and Sub -surface soils
S.N SURFACE SOIL SUB-SURFACE SOIL
1. Soil up to a depth 30cm Soil layers beyond 30cm depth
2. Physically loose and granular Comparatively compact
3. More porosity Less porosity
4. More organic matter content Less organic matter content
5. Biological activity is more Microbial activity is less
6. Mostly manipulated zone Relatively un manipulated
7. Root activity is more Comparatively less excepting in cases of long
duration / perennial crops
8. It is completely weathered It is partially weathered
9. most of the essential nutrients are
present in available form
Less content of essential nutrients in available
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Unit: 2 Rock and minerals. Weathering of rocks; Physiographic units of Nepal in
relation to soil. Evolution of earth
ROCK AND MINERALS
Rocks are the in organic materials that form the essential part of the Earth’s solid crust. Rocks
are hard mass of mineral matter comprising one or more rock forming minerals”.. The study of
rocks is called Petrology.
In general, Earth crust is composed by 74% of sedimentary rock, 18% igneous rock and 8% metamorphic
rock.
Types of ROCK.
1. Igneous rock.
They are formed by cooling of molten magma. These are first formed in the earth crust due to the
solidification of molten magma.
Classification of Igneous rock
A. Based on the mode of formation.
 Extrusive rocks or volcanic rocks
These rocks are formed due to the consolidation of magma on the surface of the
Earth. e.g. Basalt.
 Intrusive rocks or plutonic rocks
These rocks are produced due to solidification of magma below the surface of the earth.e.g.
Granite, diorite,
B. Based on the chemical composition
 Acidic igneous rock : >65% SiO2 e.g. granite
 Basic igneous rock: 56 to 65% SiO2. Eg. Basalt and Gabro
 Neutral igneous rock: 40 to 55% e.g. Diorire
2. Sedimentary Rock:
These rocks are formed from the consolidation of sediments accumulated through wind or water
action at the surface of the earth. Many are deposited in layer or formed through chemical
reactions as precipitates from aqueous solutions. Weathering of rocks by several process as
physical, chemical and biological forms sediments and transportion of these sediments takes
place by wind, water and gravitational pull.
Eg. Sandstone, Shale, Gypsum, limestone
3. Metamorphic rock:
These are formed by metamorphism or transformations of igneous and sedimentary rock under the
influence of chemically active liquid, gases, heat and pressure. e.g. Sand stone: Quartzite formed
from Sandstone
Slate/Mica formed from Shale
Marble formed from Limestone
Granite gneiss formed from Granite
Minerals are naturally occurring homogeneous inorganic substance with definite crystal structure,
chemical composition and physical properties.
a) Primary Minerals: Minerals that are original components of rocks are called primary minerals. Eg.
(Feldspar, mica, Quartz, muscovite orthoclase biotite etc.)

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b) Secondary minerals: Minerals that are formed from changes in primary minerals and rocks are
called secondary minerals (Hematite, calcite, gypsum, clay minerals).
c) Accessory minerals those which are present in small quantities, whose presence or absence will not
alter the properties of rocks, are called accessory minerals. (Tourmaline, magnetite etc).
 Physical properties of minerals
 Color: Denotes the natural color of the mineral
 Fracture/ cleavage: It is the physical property of a mineral which shows the manner of breaking.
 Hardness: It is the relative easiness to scratch a mineral.
 Luster: It is the property of mineral by virtue of which it becomes capable to reflect light.
 Crystal form: Crystal structure is the result of regular grouping of atoms that are homogeneous. A
crystal is a polyhedral form, which means it is a geometric solid.
 Specific gravity: It is the ratio between the weights of mineral to the weight of equal volume of
water displaced by it.
Weathering of rocks
Weathering
A process of disintegration and decomposition of rocks and minerals which are brought about by physical
agents and chemical processes, leading to the formation of soil on the earth’s surface or above the solid
rocks.
 Types of weathering:
A. Physical weathering
It is the process of disintegration of rock and minerals into smaller particles. The rocks are
disintegrated and are broken down to comparatively smaller pieces, without producing any new
substances.
a) Action of Temperature
The variations in temperature exert great influence on the disintegration of rocks.
During day time, the rocks get heated up by the sun and expand. At night, the Temperature falls and
the rocks get cooled and contract. This alternate expansion and contraction weakens the surface of
the rock and crumbles it because the rocks do not conduct heat easily.
The differential expansion of minerals in a rock surface generates stress between the heated surface
and cooled un- expanded parts resulting in fragmentation of rocks.
b) Action of Water:
Water acts as a disintegrating, transporting and depositing agent.
i) Fragmentation and transport
Water beats over the surface of the rock when the rain occurs and starts flowing towards the ocean
 Moving water has the great cutting and carrying force.
 It forms gullies and ravines and carries with the suspended soil material of variable sizes.
 Transporting power of water varies.
It is estimated that the transporting power of stream varies as the sixth power of its velocity i.e the
greater the speed of water, more is the transporting power and carrying capacity.
ii) Action of freezing
Frost is much more effective than heat in producing physical weathering

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 In cold regions, the water in the cracks and crevices freezes into ice and the volume increases to one
tenth
 As the freezing starts from the top there is no possibility of its upward expansion. Hence,
 the increase in volume creates enormous out ward pressure which breaks apart the rocks.
4. Action of wind
Wind has an erosive and transporting effect. Often when the wind is laden with fine material viz.,
fine sand, silt or clay particles, it has a serious abrasive effect and the sand laden winds itch the rocks
and ultimately breaks down under its force.
B. CHEMICAL WEATHERING:
Decomposition of rocks and minerals by various chemical processes is called chemical Weathering.
It is the most important process for soil formation.
1. Hydration
Chemical combination of water molecules with a particular substance or mineral leading to a change
in structure. Soil forming minerals in rocks do not contain any water and they undergo hydration
when exposed to humid conditions. Up on hydration there is swelling and increase in
volume of minerals. The minerals loose their luster and become soft. It is one of the most
common processes in nature and works with secondary minerals, such as aluminium oxide and iron
oxide minerals and gypsum.
Example:
a) 2Fe2O3+ 3HOH 2Fe2O3.3H2O
(Haematite) (red) (Limonite) (yellow)
b) Al2O3+ 3HOH Al2O3.3H2O
(Bauxite) (Hyd. aluminium Oxide)
c) CaSO4+ 2H2O CaSO4.2H2O
(Anhydrite) (Gypsum)
2. Hydrolysis
Most important process in chemical weathering. It is due to the dissociation of H2O into H+
and OH-
ions which chemically combine with minerals and bring about changes, such as Exchange,
decomposition of crystalline structure and formation of new compounds. Water acts as weak acid on
silicate minerals.
KAlSi3O8+ H2O HAlSi3O8+ KOH
(Orthoclase) (Acid silt clay)
HAlSi3O8+ 8HOH Al2O3.3H2O + 6 H2SiO3
(Recombination) (Hyd. Alum. Oxide) (Silicic acid)
This reaction

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3. Solution
Some substances present in the rocks are directly soluble in water. The soluble substances are
removed by the continuous action of water and the rock no longer remains solid and form holes, rills
or rough surface and ultimately falls into pieces or decomposes. The action is considerably increased
when the water is acidified by the dissolution of organic and inorganic acids. (e.g.) NaCl
NaCl + H2O Na+
, Cl-
, H2O (dissolved ions with water)
4. Carbonation:
Carbon di oxide when dissolved in water it forms carbonic acid.
2H2O + CO2 H2CO3
This carbonic acid attacks many rocks and minerals and brings them into solution. The carbonated
water has an etching effect up on some rocks, especially lime stone. The removal of cement that
holds sand particles together leads to their disintegration
CaCO3+ H2CO3 Ca (HCO3)2
(Calcite) (Ca bi carbonate) slightly soluble readily soluble
5. Oxidation
The process of addition and combination of oxygen to minerals. The absorption is usually from
O2dissolved in soil water and that present in atmosphere. The oxidation is more active in the
presence of moisture and results in hydrated oxides. (e.g.) minerals containing Fe and Mg.
4FeO (Ferrous oxide) + O2 2F2O3 (Ferric oxide)
4Fe3O4
(Magnetite) + O2 6Fe2O3 (Hematite)
2Fe2O3
(Hematite) + 3H2O 2Fe2O3.3H2O (Limonite)
Reduction
The process of removal of oxygen and is the reverse of oxidation and is equally important in
changing soil color to grey, blue or green as ferric iron is converted to ferrous iron compounds.
Under the conditions of excess water or water logged condition (less or no oxygen), reduction takes
place.
2Fe2O3 (Hematite) - O2 4FeO (Ferrous oxide) - reduced form
C. Biological Weathering
Unlike physical and chemical weathering, the biological or living agents are responsible for both
decomposition and disintegration of rocks and minerals. The biological life is mainly controlled
largely by the prevailing environment.
1. Man and Animals
The action of man in disintegration of rocks is well known as he cuts rocks to build dams, channels
and construct roads and buildings. All these activities result in increasing the surface area of the
rocks for attack of chemical agents and accelerate the process of rock decomposition.
A large number of animals, birds, insects and worms, by their activities they make holes in them and
thus aid for weathering.
2. Higher Plants and Roots
The roots of trees and other plants penetrate into the joints and crevices of the rocks. As they grew,
they exert a great disruptive force and the hard rock may broke apart. (e.g.) pipal tree growing on
walls/ rocks.

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2. Micro- organisms
In, the lower forms of plants and animals like, mosses, bacteria and fungi and actinomycetes play an
important role in early stages of mineral decomposition and soil formation .They extract nutrients
from the rock and produce organic acid during organic decomposition which aid in mineral
decomposition.
Physiographic units of Nepal in relation to soil
Nepal is mountainous land locked country having subtropical to tundra climates. Generally there are
five physiographic divisions in this country. Each division has distinct bed rock, climate and
hydrological characteristics.
1. Terai
 This region occupies 211,000 ha or 14.4% of the country and formed by alluvial deposits which is
predominately loamy textured, slightly acidic and stone free.
 This region consist of gently sloping and elevation of this region ranges from 60 -330 masl with
slope gradient of 0.2 -0.1%.
 Land of this zone is flat to almost flat with the exception of minor local relief caused by river action.
 As year round growing season, good soils, availability of irrigation water, a relatively well developed
infrastructure and easy access to market allows intensive agriculture development in Terai.
 Major crop grown include rice, maize, wheat, mustard and pulses. This region also called as bread
basket of the country.
 Hardwood forest is found in this region.
 Major soil types dominant in this region are Ustorchrepts, Haplustolls, Haplaquepts, Haplustalfs,
Ustifluvents and Ustorthents.
2. Siwalik
 This region occupies 187,900 ha or 12.7% of the land area of Nepal with subtropical climate.
 The relief of Siwalik ranges from 300- 1000 masl with moderate to steeply and very steep rugged
lands
 The soils of Siwaliks are composed of sandstone, mudstone, siltstone, shale and conglomerates.
 This region has five major land system i.e.
a) Active and recent alluvial plains
b) Fans, apron and ancient river terrain (Tar)
c) Depositional basins (Duns)
d) Moderately to steep sloping hilly and mountain terrains
e) Steeply to very steeply sloping hill and mountains
E.g. dun valley like Surkhet, Dang, Deukhuri, Chitwan, kamala valley to bedrock controlled
mountainous land system with pronounced natural slope instability.
 The dun valleys are extremely cultivated because of their fertile soils. The major crops grown are
rice, maize, wheat, mustard, millet and pulses.
 Major soil types dominant in this region are Ustorthents, Psamments, Haplustolls, Haplaquepts,
Haplustalfs, Ustifluvents, Lithic and Ustochrepts.

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3. Middle Mountain
 This region occupies 4,350,300 ha or 29.5% of land area of Nepal with subtropical to warm
temperate climate.
 The relief of middle mountain ranges from 1,000 -2,000 masl.
 It comprises of 600 million years old rocks phyllites, quartzite, mica, schist with islands of granite
and limestones.
 The middle mountain region has been the homeland for most people in Nepal. Middle Mountains are
found in old terraces, valley and tars.
 Climate supports all the year round agriculture production and temperature is never extreme and hill
slopes are suitable for terracing.
 This region has been divided into four land forms which are, a. alluvial plains b. ancient lake and
river terrain c. moderately to steeply sloping mountainous terrains and steeply to very steeply sloping
mountains. E.g. Kathmandu valley is located in middle mountain range.
 Extensive cultivation occurs on gentle slopes of 10-30% low lying areas grow rice and wheat, maize,
millet, soybean and other crops are grown on terraces.
 Major soil types dominant in this region are Psamments, Ustochrepts, Haplustalfs, Ustifluvents,
Lithic and Ustochrepts.
4. High Mountain
 This region occupies 2,899,500 ha or 19.7% of land area of Nepal with warm temperate to alpine
climate.
 The relief of this region is 2,000 -3,000 Masl.
 It is composed of phyllites, quartzite, mica, schist, limestone and other more metamorphosed
sedimentary rocks.
 All the valleys are glaciated and weathering is quite limited in this region because of cooler and
drier climate.
 Rice is grown in alluvium material, whereas millet, potato, wheat and barley is grown up to 3000
masl on terraces, blue pines are found in slopes.
 This region has been divided in to three land system which are,
a) alluvial plains and fans
b) post glaciated mountain terrain below upper altitudinal limit of arable agriculture,
c) Post glaciated mountain terrain above upper limit of arable agriculture.
 Major soil types dominant in this region are Ustifluvents, Eutrochrepts, Dystrochrepts, Anthropic
and typic Eutrochrepts.
5. High Himalayan region
 This region occupies 3447,500 ha 23.7% of the land area of Nepal with alpine to arctic climatic
region so there are active glacier system.
 Elevation ranges from 3000 m to 8848 masl.
 Land is very steep and rugged so there are a few pockets of arable lands such as in Solokhumbu,
Manang, Mustang and Dolpa.
 Over 86% of this region has bedrock at or near the surface on very steeply sloping terranin. Bedrock
includes gneiss, schists and Tethys sediments of which limestone and shale predominates.

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 Being frozen and snow bound above 5000m for 6-12 months, the climate in this region don‘t support
arable agriculture except in a few isolated areas.
 About 12% of this region is suited to mountain grazing and potatoes, naked barley and millets are
grown in the lower terraces.
 Physical weathering predominates so soil is very stony
 Major soil types dominant in this region are Cryumbrepts, Cryorthents, Lithic cryumbrepts and
rocks.
 This region has been divided in to two major physiographic units i.e.
a. Alluvial ,colluvial and moraine depositional surface
b. Steep to very steep mountainous terrain.
EVOLUTION OF EARTH
Earth is one of the 8 planets orbiting the SUN in the Solar System. Our solar system consists of 9
planets and 31 satellites, a belt of asteroids. Various theories have been proposed about the origin of
earth which is
1. Nebular Hypothesis ( Kant and Laplace hypothesis)
 The earliest hypothesis developed by Kant (1755) and Laplace (1796) about the origin of the Earth
was known as Nebular hypothesis.
 According to them, there was a large, hot and rotating cloud of dust and gas called Nebula in the
space.
 Gradual cooling of this nebula resulted contraction in shape and size and become relatively smaller.
Due to decrease in size, the rotating speed about its axis was increased. The huge equatorial mass of
this nebula was bulged out by increasing centrifugal force caused by highly increased rotating speed
in equatorial region.
 The bulged gaseous mass of the nebula was separated into gaseous ring and gaseous ring was
coalesced into processes, ten masses were formed.
 Nine of them were called planets and one mass was further disintegrated into other smaller masses
called planetoids. The central remaining hot gaseous body was called sun.
 The newly formed planets were cooler down from gaseous state to liquid and finally to solid state.
A large hot and gaseous nebula was rotating in the space
Cooling of nebula resulted contraction in size and increased the revolving speed in its own
axis
Equatorial zone of nebula was bulged out due to increasing centrifugal force
Gaseous ring was formed around the nebula and the ring was separated out from the
nebula
The separated ring was coalesced in the form of globe and continued to revolve round the
nebula

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Fig: schematic flow diagram of Nebular hypothesis for the origin of Earth.
Demerits of Nebular hypothesis
a. It doesn‘t satisfy the principle of conservation of angular momentum in the solar system.
b. After detachment of huge mass from nebula, the speed of the nebula would further increases and
there should be formation of other astronomical masses thereafter.
c. The method of coalescence isn‘t explained clearly in this hypothesis.
d. It doesn‘t explain adequately the origin of the solar system.
2. Planetesimal Hypothesis ( Chamberlain and Moulton hypothesis)
 It was proposed by Chamberlin and Moulton in 1904 about the origin of earth and was called as
Chamberlain and Moulton hypothesis.
 This hypothesis states that the planets were originated as a result of mutual interaction between the
sun and another star. According to this hypothesis, Sun and another large star came nearer to each
other and a large tidal force was produced on the surface of the sun.
 Due to this large tidal force, the surface of the sun was disrupted and a large numbers of gaseous
bolts of sun mass were shot forth from the sun in the space. Cooling of these gaseous bolts formed
small masses called Planetesimal.
 This Planetesimal were rotating round the sun and collision of Planetesimal formed planets and
planetoids.
Fig: the schematic presentation of the Planetesimal Hypothesis about origin of Earth.
3. Gaseous Tidal Hypothesis ( Jeans and Jeffrey hypothesis)
Similar ways 10 rings were formed and converted to 10 globe like masses
From 9 rings, 9 planets were formed and one ring was further broken down to planetoids.
Sun and another large star came nearer to each other
Increase tidal force on the surface of the sun
Disruption of the mass of the sun was taken place
Numbers of gaseous bolts were shot forth in the space
Cooling of gaseous bolts formed small solid masses called Planetesimal
Planetesimals rotated round the sun and formed planets by collision of Planetesimal

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 Jeans and Jeffrey (1925) proposed a hypothesis about the origin of the Earth and planetary system
and was called Jeans and Jeffrey hypothesis.
 This is the most popular and wide accepted hypothesis about the origin of the earth.
 According to this hypothesis, in ancient time, a large star came nearer to the sun. A great tidal pull
was developed on the surface of the Earth.
 When star came in the nearest distance to the sun a huge mass of sun surface was detached from the
sun and star moved gradually away from the sun but the detached mass started to rotate around the
sun.
 Detached mass from the sun was highly unstable and was immediately broken down into ten
fragments. Nine of them were called planets and next one was further broken down to smaller
masses and was called planetoids. They revolve round the sun in their own axis and gradually cooled
down to liquid and solid state.
NOTE:
 Geology: It is science of earth or the study of earth, its surface feature and history.
 Branch of geology:
 Physical geology (it deals with study of which are in operation in moulding the surface of earth. Eg.
Blowing of wind)
 Structural geology (it is the study and interpretation of rock masses and deals with the configuration
of rocks in the earth‘s crust.
 Mineralogy (it is the study of minerals, the constituents of rock which constitute the earth crust.)
 Petrology( it is the science of rocks)
 Paleontology (it deals with the mode of preservation of remains of plants and animals with the rock
beds and their proper utilization in the past history of the Earth.)
 Geomorphology (it deals with the study of landforms)
 Economic geology (it deals with the study of economically important mineral deposits, mode of
formation, occurrence and distribution.
Unit: 3 Soil properties
A. Physical properties
Physical properties (mechanical behavior) of a soil greatly influence its use and behavior towards
plant growth. The plant support, root penetration, drainage, aeration, retention of moisture, and plant
nutrients are linked with the physical condition of the soil. Physical properties also influence the
chemical and biological behavior of soil. The physical properties of a soil depend on the amount,
size, shape, arrangement and mineral composition of its particles, organic matter content and pore
spaces.
Important physical properties of soils.
1. Soil texture, 2. Soil structure 3. Soil density (bulk and particle density)
4. Soil porosity, 5.Soil color, 6.Soil consistence, 7. Plasticity, adhesion and cohesion.

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1. Soil texture
Soil texture is a relative proportion of soil separates/soil particles in a given soil mass or it is the
relative percentage by weight of the three soil separates viz., sand, silt and clay particles.
The proportion of each size group in a given soil (the texture) cannot be easily altered and it is
considered as a basic property of a soil.
Soil separates are defined as the soil particles smaller than 2mm diameter.
• It indicates the coarseness & fineness of a soil.
• It affects physical, chemical & biological properties of a soil.
• It necessary to know sizes & behavior of soil separates to understand use of soil texture
 Classification of Soil particles according to their size
Soil particles USDA system ( diameter) ISSS system (diameter)
Sand 0.05 – 2mm 0.02- 2mm
Silt 0.002-0.05mm 0.002-0.02mm
Clay < 0.002mm < 0.002mm
 Soil separate
Soil separates are defined as the soil particles smaller than 2mm diameter formed by weathering of
rocks. The soil separates are of three types which are:
a. Sand(course type)
 Soil particles are larger, round or irregular in shape with sizes ranges from 0.05 to 2mm (USDA) or
0.02- 2mm (ISSS).
 Usually consists of quartz but may also contain fragments of feldspar, mica.
 They aren‘t plastic, low water holding capacity and good for drainage and aeration and high porosity.
b. Silt
 Particle size intermediate between sand and clay ranges from 0.002 – 0.055 mm (USDA) or 0.002 –
0.02 mm (ISSS system).
 Since the size is smaller, the surface area is more
 They are micro-sand particles and dominant by quartz and contain significant amount of feldspars
and mica.
 It shows properties intermediate between sand and clay.
c. Clay
 Clay particles are the smallest of the soil separates having particle size less than 0.002 mm in
diameter.
 They are plate like or needle like to round in shape.
 They are colloidal in nature and has high surface area.
 It has high swelling and shrining properties, high cohesion and absorption a, high water holding
capacity, poor drainage and aeration and negatively charged particle
 Some properties of soil separate
S.N. Properties Sand Silt Clay
1. Water holding capacity Low Medium to high High

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2. Aeration Good medium Poor
3. Drainage rate high Slow to medium Very slow
4. Soil organic matter low Medium to high High to medium
5. Decomposition of organic matter rapid moderate Slow
6. Nutrient availability Low Medium High
7. Shrinkage and swell potential Very low Low Moderate to high
 Soil textural classes :
Textural classification of soil is done by using the textural triangle after determining the quantity of
sand, silt, and clay present in soil.
Broadly soils are classified into four group based on soil texture and textural properties which are:
sandy soil, loamy soil, silty soil and clay soils. There are twelve textural classes.
Fig. Triangle of textural classes
a. Sandy( coarse- textured) soil / light soil
Sandy soils are coarse textured soil with higher proportion of sand which includes all soils of which
sand separates make up ≥70% & contains <15% clay particles by weight.
 The properties of such soils are
 Loose, friable, well drained & are easy to till.
 Low WHC but a more water is available for plant growth
 good aeration and tend to be droughty & need
 More frequent irrigation.
 High infiltration and percolation
 Low in nutrient status.
 Wind erosion a serious problem when land is bare.
 Due to loose & friable nature, sandy soils require light
 Drawbar pull & as such, they are called light soils.
 Two specific classes are recognized i.e. sand and loamy sand.

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b. Loamy (medium-textured) soils
Loam soil is medium textured soil and lies in between clayey and sandy soils by properties. An ideal
loam a mixture of sand, silt & clay particles in about equal proportions which contains 7-27% clay,
28-50% silt and less than 52% sand. This exhibits light & heavy properties. According to dominance
of soil separates, loamy soils are classified as (7) Sandy loam, Loam, Silt loam, silt, Sandy clay
loam, silt clay loam & clay loam. It is best suited soils for the prod of most agricultural crops. It has
better water, nutrient holding capacity, good aeration, easier for tillage operations therefor it is
considered as best soil for crop growth.
c. Clayey ( fine textured soil)
Clay is fine textured soil. Clayey soils have three classes as sandy clay, silty clay, and clay soils.
A clay soi1 must contain at least 35% of the clay separate and in most cases not less than 40%. In
such soils the characteristics of the clay separates are distinctly dominant. The characteristics of
clayey soils are
o have high water & nutrient holding capacity
o Infiltration rate slow & poorly drainage
o Have high plasticity & cohesion & are difficult to cultivate.
o Require a heavy drawbar pull to plow-heavy soils.
o These soils must be worked when moisture is just right so it is also called as 24-hour soil.
d. Silty soils
Soils containing higher proportions of silt are known as silty soils.
Its composition is >80% silt and not more than 12% clay.
Naturally the properties of this group are dominated by those of silt. Only one textural class is
included in this group as silt. Nutrient and water holding capacity of silty soil is always less than clay
and loam soils.
NOTE:
12 Soil textural classes
Common name Textural properties Textural classes
Sandy soils Course Sand
Loamy sand
Loamy soils
Moderately coarse Sandy loam
Medium Silt loam
loam
Moderately fine Clay loam
Silt clay loam
Sandy clay loam
Silty soils Medium textured Silt
Clayey soils Fine textured Sandy clay
Clay
Silty clay
Importance of soil texture:
a) Soil texture is important in taxonomical classification of soil
b) It inherits soil fertility & is important in soil fertility evaluation.

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c) It influences soil porosity which has significant role in root respiration, water holding capacity and
microbial activities.
d) It is one of the important factors which affect physical properties of soil such as WHC, drainage,
infiltration etc. E.g. Sandy soil has poor WHC, high infiltration & better drainage whereas clayey
soil higher WHC, low infiltration, & poor drainage.
e) It Influences chemical properties like Cation exchange capacity. E.g. Clay particles have higher -ve
charge, held more water & cations.
f) Soil textural classes help in determination of surface area, which affects chemical properties of the
soil such as CEC, nutrient HC, nutrient availability & microbial activity.
g) It is useful in selecting crops suitability to an area e.g. rice in heavy soils.
h) It affects tillage requirements for land preparation.
i) It affects root penetration and growth which directly affects plant health and nutrient uptake.
2. Soil structure
Soil structure is defined as the grouping, combination or arrangement of primary soil particles like
sand, silt and clay into secondary soil particles or soil aggregates which are separated by the surface
of weakness. It is the mutual orientation, arrangement and organization of particles in the soil. Soil
structure influences pore size and pore patterns which affect on water movement, heat transfer,
aeration, tillage, liming and manuring.
NOTE:
Ped: naturally occurring soil aggregate
Clod: artificially formed soil aggregate
Structured soil: soils having observable aggregation or definite and orderly arrangement of lines of
weakness.
Structure less soil: soils have no observable aggregation or definite arrangement of lines of
weakness.
 Types of soil structure :
There are four principle types of soil structures
a. Spheroidal
Peds with spheroidal shape of sizes ranges <1mm to > 10mm are called spheroidal structures.
In this structure, the horizontal and vertical axes of Peds are more or less equal in shape with not
exceeding an inch in diameter. They are loosely arranged & readily separated; Water/air circulates
very easily through such soils. It is the most desirable type of soil structure for growing plants
because of presence of high pore space. They are common in grassland soils and soil that have been
worked by earthworm. It characteristics of many surface soils (usually A horizon), particularly those
high in OM.
They are of two types:
I. Granular: Relatively non porous or less porous spheroidal aggregates.
II. Crumb: Very porous spheroidal aggregates-crumb.
b. Platy structure
Peds are plate like and aggregates arrange in relatively thin horizontal plates where horizontal axis of
the peds are much larger than vertical axis. They are most noticeable in surface layers of virgin
soils/forest but may be present in subsoil (E horizon), clay pan soil.
Plates develops as a result of soil forming processes, inherited from soil Parent material, compaction
of clayey soils by heavy machinery can create plate structures.

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c. Blocky structures
Aggregates are irregular & roughly cube like blocks with size range from about 5 to 50 mm across.
Blocks are irregularly six faced with their three dimensions more or less equal that means vertical
and horizontal axes are almost equal. They are confined to B horizon (sub soil) that promotes soil
drainage, aeration & root penetration and relatively large blocks resists penetration & movement of
water.
They are of two types,
I. Angular blocky: faces are flat and edges are sharp
II. Sub angular blocky: faces and edges are rounded.
d. Prism shaped structures
The soil structures have prism like/pillar like vertically oriented aggregates or pillars with sizes
ranges from 15 cm or more. The aggregates have larger vertical axes than horizontal axes. They are
commonly found in subsoil horizons in arid and semi-arid regions. They have poor water
circulation and poor drainage.
They are of two types,
I. Columnar structure: pillars like ped structure with flat top.
II. Prismatic structure: pillars like structure with relatively angular and rounded top.
 Importance of soil structures in Agriculture
 It influences soil aeration so the more the aggregates formation, the more air in functions.
 It influences infiltration. In granular & crumb soils, there is high infiltration; In blocky structured
soils, poor infiltration due to compactness of blocky aggregates.
 It resists soil erosion due to formation of soil aggregates.
 Good seed bed preparation: In spheroidal soils, better growth of plant due to better root penetration
especially for potato, sugar beet, maize etc.
 Well aggregated soil has nutrients and water holding required for plant growth.
 Soil aggregation is useful for better microbial growth and activities.
3. Bulk Density (Db)
It is defined as the mass or weight of dry soil per unit bulk volume of soil or it is the mass or weight
of unit volume of dry soil including both solid and pore space. It indicates the compactness of the
substance. It is expressed in Mg/m3 or gm/cm3 [Mg = 106
gm. = 1 ton].
Bulk density of the agriculture soils commonly ranges 1.2 -1.4 gm/cm3 with an average value of
1.33 gm/cm3. Db of organic soil commonly ranges from 0.1-0.6 gm/cm3. It is measured by Core
sampler.
Mathematically, it is expressed as,
Mass of dry soil
Bulk Density (Db) =
Bulk volume of soil (Volume of soil solid + volume of pore space)
Db = Ws (gm/cm3)
Vt

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Where,
Db = bulk density of soil (in gm/cm3)
Ws = weight or mass of oven dry soil at 1050C (in gm)
Vt = Vs + Vp = bulk volume of soil
Vs = volume occupied by soil solid (cm3)
Vp = volume occupied by pore (cm3)
 Factors affecting the bulk density of soil
It is determined by quantity of pore spaces as well as soil solids, therefore loose & porous soils will
have low weights per unit volume (Db) & more compact will have high Db values.
a. Soil texture
A fine textured/clayey soil has more pore space due to better aggregation, hence lower Db than
coarse textured/sandy soil in which particles lie in close contact.
The lesser the pore spaces, the higher the (Db), so clay soil have less (Db) than sandy soil.
b. Humus/organic matter
Surface soil having high OM have lower Db because humus bind primary particles to form soil
aggregates so, wt. of unit volume of soil decreases.
c. Soil depth
Db of surface soil is usually lower than that of sub-soil because surface soil contains more OM than
sub-surface and plants roots of surface soil bind soil particles & form soil aggregation.
d. Nature of crops
Db. of soil decreases if grasses are grown because grass roots bind soil particles to form soil
aggregates.
e. Animal trampling/use of heavy machinery
Animal trampling during rainy season by large number of animals in small pastureland increases
soil compactness and decreases pore volume; So, Db increases
4. Particle Density:
It is defined as the mass or weight of soil solid per unit volume of soil solid when dried.
This volume includes only solid volume. It is expressed in unit of Mg/m3 or g/cm3 & ranges from
2.6 to 2.7 gm/cm3 with an average value of 2.65 gm/cm3. Most of cultivated soil has Dp of 2.4 to
2.7 gm/cm3. It is measured by pycnometer.
It is mathematically expressed as,
Particle Density (Dp) = weight of dry soil
Volume of soil solid
Dp = Ws gm/cm3
Vs
Whereas,
Dp = particle density of soil (in gm/cm3)
Ws = weight or mass of oven dry soil at 1050C (in gm)
Vs = volume occupied by soil solid (cm3)
 Factors affecting particle density of soil
Dp depends on chemical composition & crystal structure of mineral particles.
a. Soil minerals
Soils having higher content of mineral particles are high in Dp. Dp varies depending on the nature of
mineral particles. If soil is rich in heavy minerals like magnetite, hornblende, tourmaline, the Dp will
be higher (>2.75 gm/cm3).

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b. Organic matter
The greater the OM in a soil, the lesser the particle density. OM weighs much less than an equal
volume of mineral solids having a Dp of 1.1 to 1.4 gm/cm3.
5. Porosity
It is defined as the portion of soil that is occupied by air and water. Soil porosity (f) is the ratio of
pore volume (Vf) to total soil volume (Vt). Amount of these pore space is determined largely by the
arrangement of the solid particles. Porosity is generally between 30-60%.
Mathematically,
f = Vf / Vt
porosity of soil = (1 – Db) X100
Dp
 Relation between Bulk Density (Db), Particle Density (Dp) and Porosity
Let
Ws= Wt of oven dry soil (solid)
Vs = Volume of oven dry soil (solid)
Vp = Volume of pores
Vs+ Vp = Total soil volume
As we kow,
Bulk Density (Db) = Ws (i)
Vs + Vp
And,
Particle Density ( Dp) = Ws….. (ii)
Vs
Dividing equation (i) by equation (ii)
Db = Vs or Vs
Dp Vs + Vp Vt
or, Db X 100% = Vs X 100% = % solid space.
Dp Vt
We know that,
% pore space + % solid space = 100
% pore space = 100 - % solid space
% pore space = 100 – Db X 100
Dp
Porosity of soil = (1 – Db) X100
Dp
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Importance of Bulk density, Particle density and porosity
 Porosity influences soil aeration that affects root growth and microbial respiration.
 Soil aeration and water retention can be estimated by calculating bulk density of that soil.
 Bulk density of soil gives idea of that particular soil about plant penetration, microbial respiration.
 Bulk density helps in the study of soil compactness.
 Crop suitability of soil can be selected by knowing soil bulk density and porosity.
6. Soil color
It is an important characteristic of the soil which is easily observable and most noticeable.
It is influenced by the amount of organic matter content and chemical state of iron and other mineral
(silica, mica etc.) fraction of the soil.
Kinds of soil color
i. Lithochromic: soil color is inherited from its Parent materials E.g. Red soil developed from red
sandstone.
ii. Acquired/pedochromic: Soil color develops during soil formation (reactions).
 Soil color depends upon following factors.
a. Organic Matter content of the soil
Organic matter in soil decomposes into the black Humus. Humus is dark colored materials that coat
the soil particles and gives black color to soil. About 5% OM in a soil is sufficient to make the soil
black. In surface soils, where OM contents are higher are brown, dark brown or grey brown to black
in color.
b. Mineral content of the soil
Mineral plays a prime role in coloring the soil. Most of the minerals natural color is white or light
grey. The most reactive elements in soil are Fe and Mn which impart red, brown or dark brown color
to the soil. Calcium and Magnesium carbonates dominated soils are white in color.
Minerals Chemical formula Color
Ferric Oxide/ Hematite Fe2O3 Red( well aerated soil)
Hydrated Ferric Oxide / limonite Fe2O3.nH2O Yellowish brown (semi-aerated soil)
Ferrous Oxide/goethite FeO Bluish grey( Submerged land)
Maganic Oxide MnO2 Blakish brown
Calcium/ Magnesium Carbonate CaCO3/MgCO3 White color ( in arid region)
c. Drainage
 In poor drainage, Organic matter is accumulated in the surface layer giving very dark color.
 In intermediate drainage, soil color is yellow due to hydrated Fe and Mn oxides.
 In Good drainage, Iron present in the soil gives red color to the soil due to oxidizes of iron into iron
oxide.
d. Climate
 In cool temperate climate, soil color of surface soil is grayish brown to blackish
 In arid region, soils are mostly grayish brown or reddish brown color.

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NOTE:
Determination of soil color: Soil color can be determined by using Munsell color charts
Composed of three measurable variables i.e. Hue, Value and Chroma
 Hue: It represents the dominat spectoral color (red, yellow and green) in mineral soils. They are
arranged by pages
 Value: It indicates degree of lightness or darkness of color. They are arranged vertically
 Chroma: It indicates the purity of color or strength of the spectoral color and increases with
decreasing grayness of the same value.
 Importance of soil color
 It indicates the fertility status / organic matter content of the soil.
 It shows the Fe and Mn content of the soil.
 It provides the information to human being about soil property and fertility status.
 It is useful to know the drainage condition.
7. consistency
It is the resistance of the soil to mechanical stresses or manipulation at various moisture contents. It
describes the action of the physical forces of cohesion and adhesion in soils at different moisture
condition.
8. Soil plasticity
It is the property of wet soil to change its shape under the influence of the applied force and retain its
new shape after removal of the applied force.
9. Adhesion and Cohesion
Adhesion is the attraction between the soil particles and water molecules.
Cohesion is the attraction between the different molecules of soil particles.
B. CHEMICAL PROPERTIES
Soil Chemistry is a branch of soil science, which deals with the chemical composition of soil,
chemical properties of soil and describes the chemical processes taking place in the soil. The
chemical properties of soils indicate different reaction taking place in a soil. The important chemical
properties are,
1. Soil reaction
a. soil pH
b. soil acidity and liming
c. Saline-sodic soils and their management
2. Soil colloids:
a. organic and inorganic
b. Cation and anion exchange
 Soil Reaction:
Soil reaction is the outstanding character of soil indicates whether the soil is acidic, alkaline or
neutral based on H+ ion activity. It denotes degree of acidity/alkalinity in soil that influences plant &
microbial growth, usually expressed as a pH value. It includes,

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Soil pH
It is defined as the negative logarithm of hydrogen ion concentration or inverse log of the hydrogen
ion concentration in a soil solution.
pH = -log [H+]
The scale of acidity or alkalinity is called pH scale and the unit of this scale is called pH value. This
scale runs from 0 to 14 pH values in which at pH 7 is the neutral point. All values above pH 7.0
denotes alkalinity and all values below 7.0 denotes acidity.
Acid soils have amounts of H+
and alkaline soils have more number of basic ions as OH-
.
The pH of soil solution controls the solubility of many plant nutrients which has direct impact on
nutrients availability and uptake by plants. e.g. Solubility of iron increases with decrease in soil pH
whereas the solubility of Mn increase with increasing pH. Most agricultural soils have pH ranges
from 4-9 pH but suitable ranges from 6-7.5 pH. The degree of acidity and alkalinity of a soil can be
determined by Litmus paper or pH meter or color indicator.
1. Soil Acidity
Soil having soil pH less than 7.0 is called acid soil / soil acidity. It is common in all regions of
moderate to heavy rainfall (e.g. eastern Terai of Nepal) where precipitation is sufficient to leach
appreciable amount of exchangeable non-acid cations like Na+, K+, Mg2+, Ca2+. Predominant acid
causing cations are H+, Al3+. As basic cations are removed, soil tends to become acidic in reaction.
When there is base saturation is <80%, soil becomes acidic. It means soil acidity is result of H+ &
Al3+ activity.
 Classification or Types or pool of Soil acidity
There are three types of soil acidity:
a. Active Acidity:
It is caused by activities of H+
and Al 3+
present in a soil solution at any given period of time.
This pool is very small as compared to reserve & residual acidity where the activities of plant roots
and microbes are prominent.
b. Reserve acidity/exchangeable acidity/Salt replaceable acidity:
It is caused by associated with aluminum and hydrogen ions present in exchangeable sites of the soil
colloids. It is conc. of H+ & Al3+ ions adsorbed to negatively charged clay particles and Organic
matter. These ions released into soil sol by CE with an unbuffered salt such as KCl. It is measured as
buffer pH.
c. Residual Acidity
It is caused by Al3+ and H+ bound in non-exchangeable forms in the soil micelle by organic matter
and silicate clays. It is associated with H+ & Al3+ ions that are bound in the nonexchangeable forms
by OM & clay. It can be neutralized by limestone/other alkaline materials.
d. Potential acidity
It is caused by Acid sulfate soil contains reduced Sulfur compounds such as pyrite (FeS4).
 

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Division/Types of acidic soils
a. Strongly acidic
Soil having pH less than 5.0.In this soil, Most H+ and Al+ remain in soluble forms and adsorbed H+
comes to soil solution.
Al3+
+ H2O Al (OH) 2+
+ H+
b. Moderately acidic
Soil having pH 5 to 6.5. In this soil Al3+
can no longer exist in soil solution. It changes to charge less
Al(OH)3 .
c. Neutral to Slightly acidic soils
Soil having pH 6.5 to 7.5. In this soil Al3+
is found in insoluble forms.
 Causes of Soil Acidity/Sources of Soil acidity or H+
The major causes of soil acidity are
1. Characteristics of parent materials (PM)
Soils formed from the rocks having acidic ions are acidic e.g. Granite/Quartz. Soils formed from
rocks having basic ions are basic eg. Basalt. Clay minerals such as Kaolinite, Fe and Al are acidic in
nature.
2. Accumulation of OM & their decomposition
OM contains numerous acid functional groups from which H+ ions can dissociate.
During decomposition, many (in) organic acids are released.
R-COOH ↔ R-COO-
+ H+
3. High rainfall & low evapotranspiration
Basic cations are more soluble than acidic cations so under high precipitation, basic cations (Ca2+,
Mg2+, K+, Na+) leach out but the acid cations such as Al3+ & H+
tends to retained in the soil surface therefor surface soil becomes acidic & consequently the
subsurface soil is basic.
4. Acid rain
Rain with pH value less than 5 is called acid rain which formed when SO2, CO2,CO and NO2 from
industry, automobiles and other polluted sources dissolved with atmospheric water and fall to the soil
as acid rain results acidic soil.
5. Plant residues and microbial respiration
Root respiration/OM decomposition by MOs produce high level of CO2 that combines with water
and makes carbonic acid.

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6. Oxidation of nitrogen (nitrification) or application of ammonical fertilizers
High application of ammonical fertilizers as ammonium sulphate and urea to soil reduces soil pH and
cause acidity. Nitrification of ammonical N yields H+ to the soil solution and causes soil acidity.
CO (NH2)2 + 2H+
+ 2H2O 2NH4+
+ H2CO3
NH4+
+ 2O2 → NO3-
+ 2H+
+ H2O
7. Plant uptake of basic cations/ Crop removal of basic cations
Plants especially legumes uptake more of basic certain cations (e.g. K+, NH4+ and Ca2+) and results
in the addition of H+ ions to the soil solution.
8. H+ ions (Root exudates)
Some H+ ions excreted by plants are exchanged for nutritive cations such as Ca2+ and process called
contact Cation exchange.
 Management or Reclamation of Acid Soils.
1. liming of acidic soil
The addition of alkaline materials likes carbonates, oxides or hydroxides of
Ca and Mg to the acidic soil to improve soil pH called liming. Addition of alkaline materials likes
carbonates, oxides or hydroxides of Ca and Mg gradually increases soil pH and reduce acidity.
Agriculture Liming materials are found in three major forms.
I. Oxide form:
Calcium oxide is a white lime powder also called burnt lime or quick lime. E.g. CaO (unslaked,
burned, quick lime). CaO is more effective than all other liming materials. It is produced by heating
of calcite CaCO3
CaCO3 → CaO + CO2
II. Carbonate form:
Calcite (CaCO3), dolomite Ca.Mg. (CO3)2 are important liming materials found in carbonate forms.
III. Hydroxide form:
The hydroxide form of lime is called as slaked or hydrated lime e.g. Ca (OH) 2 (slaked, hydrated
lime).
2. Reactions of Limes in Soil
When liming materials are added to a soil, the Ca and Mg compounds react with carbon dioxide &
with soil colloidal complex.
a. Reaction with carbon dioxide
When liming material is applied to an acid soil, all liming materials react with CO2 and water to
yield the bicarbonate form. Bicarbonates are easily soluble & thus dissociate Ca2+ or Mg2+.
b. Reaction with soil colloids/exchangeable complex/micelle
Ca and Mg replace hydrogen & aluminum on the colloidal complex.
2H+
+ Ca (OH)2 Ca++
+ 2H2OMicelleMicelle

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3. Use of Basic Fertilizer:
Use of basic fertilizers like sodium nitrate, basic slag etc. reduces the acidity in soils.
4. Growing of Acid Tolerant Crops:
In acid soils, acid tolerant crops should be grown, e.g. (a) Highly acid tolerant crops: Rice, potato,
sweet potato, oat, castor, Echinochloa, Paspalum etc. (b)Moderately acid tolerant crops: Barley,
wheat, maize, turnip, brinjal, cow pea, mung beans, pigeon peas, pea nuts etc.(c) Slightly acid
tolerant crops: Tomato, carrot, red clover etc.
5. Soil and water Management:
Proper soil and water management checks leaching of bases and enhances decomposition of organic
matter.
 Role / Benefits of Liming
Liming in acid soil improves soil bio-chemical activities.
a. Liming acid soils reduce toxicities of Al3+, Fe2+ and Mn4+ ions by decreasing their solubility.
b. Improve soil microbial activities: Liming of acidic soils improves activities of beneficial soil micro-
organisms.
c. Increase availability of Ca and Mg: Liming improves availability of Ca and Mg to the crops.
d. Increase Phosphorus availability: Most of the P is available at pH ranges 6.5 to 7.5. At low pH, P is
fixed by Al, Fe, and Mn as ALPO4, MnPO4 and FePO4. Liming changes soluble forms of Al, Mn
and Fe to insoluble salts and P-fixation is reduced.
e. Micronutrient availability:
Mo availability is improved by liming.
f. Nitrification/mineralization
It is improved by liming at pH 6.5 because most of Micro-organism are active for nitrification
(NH4 +
-N to NO3-
-N).
g. Nitrogen fixation
Both symbiotic and non-symbiotic atm. N2 fix is favored by liming because activity of
Rhizobium is greatly increased at pH around 6.5.
h. Liming helps to control diseases
Liming helps to reduce club root diseases of Cole crops (inhibit spore germination)
I. Improve Soil structure
Addition of Ca2+ and Mg2+ through liming enhances flocculation/granulation and cementation of fine
textured soils.
2.Soil Alkalinity/Alkaline soil
Soil having soil pH more than 7.0 is called alkaline soil or soil alkalinity. It is a problem of arid and
semi-arid regions where evapotranspiration exceeds precipitation and soluble salts-formed by
weathering are not sufficiently leached out of soil and accumulated in the form of alkali crust on in
surface layer. Presences of high degree of base forming cations as Ca2+, Na+, Mg2+ and their salts
in a exchangeable sites of soil solution make soil alkaline.
CaCO3 + HOH HCO3
-
+ OH-
Na2CO3 + H2O 2 Na+
+ HCO3
-
+ OH-

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 Types of Alkaline soils
a. Saline soils / White alkali soils (Salinization)
Soil containing higher concentration of dissolved/soluble salts (ions) of Ca, Mg, K and Na that is
sufficient to seriously interfere the growth of most plants is called Saline soils. Saline soil contains
chlorides and sulphate of Ca and Mg salts and exchange complex is dominated by Ca and Mg.
Characteristics of saline soils are
i. It has soil pH less than 8.3.
ii. The exchangeable sodium percentage (ESP) of saline soil is less than 15%.
iii. The sodium adsorption ratio (SAR) of saline soil is less than 13.
iv. The electrical conductivity (EC) of saline soil is more than 4.0 dsm-1
.
It is measured as
I. Total dissolved solids( TDS)
It is a measure of the total content of all organic or inorganic substances contained in a sample of
water. TDS is expressed as mg/liter of water.
II. Electrical conductivity (EC)
It is the ability of soil to conduct electrical current. It is expressed as millimhos/cm; decisiemens/m
or ds/m.
b. Saline-Sodic ( Saline- Alkali soils)
Soil Contains appreciable amount of neutral soluble salts of Ca and Mg and enough Na+ to seriously
affect most plants is called Saline-Sodic soils. It has following characteristics
I. Soil pH ranges from 8.3 to 8.5.
II. EC of Saline-Sodic soil is more than 4 ds/m
III. ESP of Saline-Sodic soil is more than 15%
IV. SAR of Saline-Sodic is more than 13.
c. Alkali (Sodic) soils/ Non saline alkali soils
Soil containing more soluble salts of Na than salts of Ca and Mg to sufficiently affect most plants
called Alkali or sodic soil.
It causes the soil dispersion results loss of soil structure, low hydraulic conductivity and water
logged. It has following characteristics
I. Soil pH more than 8.5.
II. ESP of sodic soil is more than 15%
III. SAR of sodic soil is more than 13.
It is measured as
I. Exchangeable sodium percentage (ESP)
It is defined as degree to which CEC is occupied with sodium.
ESP = exchangeable Na(Meq/100gm soil) * 100
CEC (Meq/100 gm soil)
• ESP level more than 15, Soil become sodic soil.
II. Sodium absorption ratio (SAR)
It is a ratio of Na (bad flocculate) to combination of Ca & Mg
(Good flocculate) which effects on soil dispersibility.
• SAR is mathematically expressed as
SAR = [Na+ ] x 100
√ [Ca2++ Mg2+]/2
It is expressed in mmoles/L
SAR more than 13, Soil becomes sodic soils.

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 Characterization of Saline, Sodic and Saline-Sodic soils
S.N. Characteristics Saline soils Saline-sodic Sodic
1. Other names White alkali or
solonchhak soils
Usar soil Alkali soils or Black
alkali
2. Exchangeable ions Ca and Mg Ca, Mg and Na Na
3. ESP <15% >15% >15%
4. SAR <13 >13 >13
5. EC >4 ds/m >4 ds/m <4 dS/m
6. pH <8.5 <8.5 >8.5
7. Presence of Salts Chloride and
sulphate
Carbonates and
Bicarbonates
variables
8. Physical condition of
soils
Flocculated Deflocculated Both Flocculated
and deflocculated
 Causes of salinity, sodicity and sodic-saline soil
a. Arid and Semiarid climate:
Saline and alkaline soils are formed in arid and semi-arid an region which have very low rainfall and
high evaporation and finally causes low leaching and accumulation of salt in the surface soil.
b. Poor drainage of soil
In poor drainage soil, salts are leached during rainfall from upper layer and accumulate in lower
layers.
c. High water table
If the water table is high, large amount of water containing salt move to the surface by capillary
action and are evaporated leaving soluble salts on the surface.
d. Irrigation of salt containing water
Irrigation of salt containing water to the field causes salinity.
e. Saline nature of parent materials
If soils develop from saline nature of parent rock materials, soil would be saline.
f. Excessive use of basic fertilizers
Use of alkaline fertilizer like sodium nitrate, basic slag etc, may develop alkalinity in soil.
 Harmful effects of salinity, sodic soils on plant growth
a. Reduction of water and nutrient absorption
Excessive salted in the soil solution increases the osmotic pressure of soil solution in comparison to
cell sap which prevents absorption of moisture and nutrients by roots.
b. Increase salt toxicity:
The presence of excessive amounts of chlorides in the soil solution produces toxic affect to plants
c. Dispersion of soil particles
Salt of sodium presence in soil solution causes dispersion of soil particles.
d. Poor physical properties of the soil
Excessive sodicity causes low aeration, low infiltration rate, low nutrient and water holding capacity
of the soils.
e. Availability of plant nutrient is reduced
The availability of plant nutrients likes Zn, P, K to the crop plant is reduced due to antagonistic effect
of Na +
salt.
f. Alkaline solution in soil has corrosive action on root and stems.

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 Management / Reclamation of Saline, Sodic soils
The restoration of soil physical and chemical properties conducive to high productivity is called soil
reclamation.
Saline or Sodic soils are managed by following methods
1. Mechanical Methods
a. Flooding and leaching down of the soluble salts
The leaching of soluble salts can be done by flooding the land by clean water and allowing in
standing which results leach down the soluble salt below the root zone.
b. Scarping of the surface soil
Scarping helps to remove salts that accumulate on the soil surface.
2. Cultural Methods
a. Providing proper drainage
Proper drainage providing surface and sub-surface help to wash out the salts.
b. Use of salt free irrigation water
Salt free good quality of irrigation water should be used.
c. Planting or sowing of seeds in the furrow.
Excessive salt are accumulated in the surface soils than sub surface so seed or seedlings are planted
inside the furrow to escape the zone of maximum salt concentration.
d. Proper ploughing and leveling of the land
Ploughing and leveling of the land increase the infiltration and percolation rate thus salts leach down
to the lower levels.
e. Retardation of water evaporation from soil surface
Frequent light irrigation and mulching reduce the rate of evaporation from soil thus, salts may
remain in the lower level with water.
f. Use of Acidic fertilizer
Acidic nature of fertilizers should be used in saline soils.
g. Growing of salt tolerant crops
Highly salt tolerant crops likes Barley, Sorghum, Sweet potato and alfalfa must be grown.
3. Chemical methods
a. Use of gypsum
When gypsum (CaSO4.2H2O) is added to Na+
affected soils, Ca2+ replaces the Na+ from the
exchangeable complex; the Na2SO4 thus formed then can be leached out with irrigation. Replacing
sodium with calcium before leaching will stabilize soil structure.
NaHCO3 +CaSO4 CaCO3 + Na2CO3 + CO2
Na2HCO3 + CaSO4 CaCO3 + Na2SO4
b. Use of elemental sulfur
Elemental Sulfur(S) & sulfuric acids can be used to advantage of sodic soils, especially where
sodium bicarbonate abounds. Sulfur, upon biological oxidation, yield sulfuric acid, which not only
changes the sodium bicarbonate to the less harmful & more leachable sodium sulfate but also
decrease the pH.
2S + 3O2 + 2H2O 2H2SO4
2NaHCO3 + H2SO4 Na2SO4 + H2O + CO2
Na2CO3 + H2SO4 Na2SO4 + H2O + CO2

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4. Soil colloids
Soil colloids are soil particles of less than 0.002mm diameter which are insoluble in water,remain
suspended in water.
 General Characteristics of Soil colloids
a. Size: They are extremely small in size less than 0.002 mm in diameter.
b. Surface area: They have very high surface area.
c. Surface charges: Both external and internal surface of colloidal soil carry dominant negative charge.
d. They have adsorption capacity of cation and anions
e. They have dispersion and flocculation property
f. They have swelling and shrinkage properties.
g. They have adhesion and cohesion capacity.
 Types of soil colloids
Soil colloids are generally classified in to two types on the basis of composition, structure and
properties.
1. Inorganic soil colloids
It is further classified into three groups
a. Crystalline silicate clays
Crystalline silicate clays are crystalline layer like structures in which horizontal oriented sheets of Si,
Al, Mg and Fe atoms surrounded and held together by O2 and OH-
group. These are the dominating
type in most soils. E.g. Kaolinite, Smectite.
b. Non Crystalline clay
They are aluminosilicate minerals which have amorphous structures. They are commonly found in
volcanic soils, e.g. Allophone
c. Iron and Aluminium clay
These clays are dominant in highly weathered soils of tropics and subtropics. They consist mainly of
either iron or aluminium atoms coordinated with oxygen atoms, e.g. Gibbsite, Goethite.
2. Organic soil colloids or Humus
A complex and resistant mixture of brown and dark brown amorphous and colloidal organic
substances which is formed due to microbial activity. They are not crystalline but they have C, H, O
rather than Si, Al, Fe.
5. Ion Exchange in soils
It is a reversible process by which one type of cation or anion held on the solid phase is exchanged
with another kind of cation or anion in the liquid surface.
a. cation exchange
It is a phenomenon of exchange or interchange of cations between a cation in solution and another
cation on the surface of clay or organic matter.
Cation exchange capacity (CEC) is the capacity of the soil to hold and exchange of cations. CEC is
defined as the sum of total of the exchangeable cations that a soil can adsorbed.
It takes place between soil colloid and soil solution, contact surface of soil clays and organic matters
and root hairs of the plants and soil solution.
It is expressed in terms of moles of positive charges adsorbed per unit mass i.e. centimoles of
positive charge per kilogram of soil (cmol/Kg dry soil).
The higher the CEC, the higher the negative charge and more cation that can be held.
It is mainly affected by amount and nature of organic matter and clay.

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 Importance of Cation Exchange Capacity in Agriculture
It is an important chemical property of a soil which plays vital role in soil chemical property and
nutrients supply to the crop plants.
 Exchangeable cation are available to higher plant e.g. The exchangeable K is a major source of K for
the crop plant and exchangeable Mg is a major source of Mg for the crop plant
 Soil reclamation: An acid soil having more CEC requires more lime than acid soils having lower
CEC to reclaim acid soils.
 Change in pH or buffering: Soil having high CEC has high buffering capacity and there will be slow
change in soil pH.
 Cation charges change a soil physical property that alters water and nutrient availability.
 Weathering and soil development: CEC has important role in the process weathering and soil
development.
 Cation exchange sites hold Ca, Mg, K, NH4 and Na ions and slow the losses by leaching.
b. Anion exchange
It is a phenomenon of exchange of anions like Cl-
, NO3-
, and PO4-
etc between exchange sites of
clay/humus and soil solution.
Anion Exchange Capacity is the capacity of soil to hold and exchange anion. It is defined as the sum
of total of the exchangeable anions that a soil can adsorb.
The anions like Cl-
, NO3-
, PO4-
and some extent HS-
and HCO3
-
and CO3
-
adsorb mainly by anion
exchange. It is measured in miliequivalent per 100 gm of soil(Meq/100gm).
 Importance of anion exchange capacity
 Helping in soil development(leaching and adsorption)
 Availability of nutrients in anionic form e.g. Cl-
, NO3-
, PO4-
, BO3- MoO40-
 Fixation of nutrients e.g. phosphate ions fixation
C. Soil Biological Properties:
1. Soil Organic matter:
Soil Organic matters are one of the solid components of soil which constitutes 5% of the soil
components. Soil organic matter includes all partially decomposed and disintegrated non-living
materials present in the soil obtained from plant or animal origin and other organic compounds
synthesized by soil organisms during the process of the decay. Organic matter is important
constituent of the agricultural soil. It is necessary for most of the soil organisms and it is an
important source of the nitrogen required for the plants. Soil containing more than 20% organic
matter is called Organic soil.
Importance of Organic matter:
Organic matter improves physical, chemical and biological properties of the soil. Organic matter
improves soil health and healthy soil is the fundamental requirement of healthy crops and which in
turn affects the human health.

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 Organic matter is source of many nutrients like N, P, and S which is essential for the plant growth.
 Organic matter provides food and environment for the many beneficial soil microorganisms.
 Organic matter binds with soil particles and improves water holding capacity.
 Organic matter helps in formation of better soil structure, improves aeration and growth.
2. Soil Organisms (Soil flora and Soil fauna):
Soil houses a number of organisms. Soil is also termed as tremendous biological laboratory as soil
and its inhabitants produce different types of biologically important substances. The residents of soil
that are related to plants like algae, bacteria, fungi etc. comes under soil flora whereas animal related
soil residents like protozoa, nematode etc. are called soil fauna.
a. Soil flora
All the plants, fungi and algae in a given soil environment is called soil flora.
It is classified as
I. Macro flora: Large sized plants present on soil are soil macro flora. e.g. Moss, Plants roots
II. Micro flora: Small sized plants and microscopic organism that inhibiting in soil are micro flora. e.g.
Algae, fungi, Bacteria and actinomycetes.
b. Soil Fauna
All the animals that inhibit in a soil in particular time is called soil fauna. It is classified as
I. Macro fauna: Large sized animals present on soil are soil macro fauna. e.g. Earthworm, Rodents, ant,
insects
II. Meso fauna: Nematode, mites
III. Micro fauna: protozoa
These soil macro fauna have important role in decomposition, aeration of soil, nutrient cycling, etc.
in association with macro fauna like roots of higher plants, and other macroscopic plants.Soil micro
flora and micro fauna play important role in mineralization and nutrient cycling.
Beneficial roles of the soil microorganisms
a. Physical disintegration and of the organic residues, decomposition,
b. Solubilization of the nutrients,
c. Atmospheric nitrogen fixation, and
d. Detoxification of the soil.
The negative roles of the some soil microorganisms include the Denitrification and
immobilization.
Some terms:
Nitrification: The process of conversion of the ammonium into plant absorbable form of nitrate
(NO3
-
) is called nitrification. It involves two step process in which firstly, mineralized nitrogen in the
form of Ammonia is converted to Nitrite ions by Nitrobacter and then to nitrate form by
Nitrosomonas bacteria.

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Denitrification: The conversion of the nitrate to nitrogen gas under anaerobic condition is called
denitrification. It is carried out by denitrifying bacteria like Thiobacillus denitrificans, Pseudomonas
denitrificans, etc.
Immobilization: The process of conversion of the nutrients in soil from inorganic form to an organic
form in living tissues of microbes is called Immobilization.
3. Organic Manures: Organic manures are those complex materials, which are organic in origin, bulky
and concentrated in nature and capable of supplying plant nutrients and improving physical,
chemical and biological environment of the soil. They have no definite chemical composition and
low analytical value prepared from animal, plant and other organic wastes and byproducts.
Advantage/ Function of organic manure
 They provide essential elements to the plant and have the direct effect on plant growth like any other
commercial fertilizers. They contain very small quantity of plant nutrients, therefore large quantity of
them need to be applied per unit area to obtain better yield.
 They supply organic matter to the soil and hence improve the physical properties of the soil like soil
structure, aeration, water holding capacity, soil temperature, bulk density etc.
 They provide food for soil micro-organisms and stimulate them, which are responsible for various
activities in the soil.
 Organic manure increases the biochemical process like cation and anion exchange capacity and
provides a buffering action in soil reaction and also influences the solubility of soil minerals as well
as mineral nutrients in soil.
 They prevent loss of nutrients by leaching or erosion.
 They also regulate the thermal regimes of the soil.
 Carbon dioxide released during organic matter decomposition acts CO2 as fertilizer for plant roots.
Classification of organic manures
Organic manures are of different types i.e. bulky and concentrated in nature. These are classified as
under.
1. Bulky organic manures
Bulky organic manures contain little amount of plant nutrients and are bulky in nature as compared
to concentrated organic manures. These are FYM, Compost, green manures eg. dhaincha, and other
leguminous crops, night soil (excreta of human), sewage ,Sludge (semi solid part of sewage or open
toilet) and Sullage (liquid of kitchen, bath room and urine etc).
3. Concentrated organic manures
The concentrated organic manures are mainly derived from raw materials of animal or plant origin
which are less bulky and those containing higher percentage of major plant nutrients than bulky
organic manures. These are oil cakes e.g. mustard oil cake, ground nut oil cake etc.and blood meal,
meat meal, bone meal etc.

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 Preparation of FYM, Compost and Green manure
1. Farmyard Manure(FYM):
FYM refers to the well-decomposed mixture of dung, urine, farm litter (bedding materials) and left
over materials from roughages and fodder fed to the cattle. The FYM collected daily from the cattle
shed consisting of raw dung and part of the urine absorbed in the refuse. On an average well-rotted
FYM contains 0.5%, 0.25% and 0.5% N, P and K respectively.
 factors affecting composition of FYM
 kind of animal, age and condition of animal,
 animal feed, kind and amount of litter used,
 digestibility of the feed consumed or function of animal,
 Handling and storage procedure of manure etc.
 Method of FYM preparation
a. Traditional Method
It is the common method of preparation of FYM is done by digging a pit and putting the material in
it. Daily addition of materials is done onto it until the field is ready for its application. The manure
pit is left open unprotected from the sun, air and rainfall. When the field is ready to receive the
manure, it is carried onto the land and left on the field in small heaps, scattered for several days
before it is plowed in. This method leads to loss of nutrients due to volatilization and leaching.
b. Improved methods of FYM preparation:
Losses of the nutrients from the FYM are minimized by careful preparation, handling and storage of
the manure. This requires use of good beddings to absorb urine, protection from sun to minimize
volatilization loss, protection from rain to minimize the leaching loss. So it must be prepared in the
pits and applied on land plowed immediately.
I. Manure pits with no turning:
Steps:
 A pit of 5m long, 3 m wide and 1m deep should be constructed in the land with proper drainage near
to the shed of animals.
 The pit should be divided into 2 parts and the first half part should be filled daily with the mixed
dung and beddings soaked with the urine until it is full about 50 cm or more above the ground.
 The heap should be plastered with cow dung- earth slurry.
 Second half of pit should be filled in similar way and when the second half is full, the rotted manure
from the first half of the pit can be taken and refilled.
This method takes about 5-6 months to produce well decomposed manure.

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II. One month turning method:
This is quicker method and takes about the 3 months to make good quality manure. The size of the
pits depends upon the amount of materials available.
Steps:
 Dig a series of three pits with only a small wall (50-60 cm) between each pit so that materials can
be moved from one pit to another. Size of pits can be 2m*2m* 1m.
 Fill the first pit with manure until about 50 cm or more above ground surface. Plaster the heap.
 After one month turn the material into second pit and refill the first pit and plaster both pits.
 After another one month turn the materials from second pits into third and from first to second and
refill the first pit and plaster all of them.
 After one month then, materials from the third pit can be removed and applied to the land and other
pits can be filled and plastered.
While turning if the manure is dry then water should be added to provide sufficient amount of the
moisture for keeping it properly rotting.
2. Compost
Compost is the product of organic residues (straw, chaff, leaves, paddy and ground nut husk,
sugarcane trash, weeds, and other agricultural as well as industrial and habitation waste) and soil that
have been piled, moistened and allowed to undergo biological decomposition. The quick breakdown
of organic materials by micro-organisms needs a warm, moist and aerated environment.
Farm compost can be made from almost any plant materials such as cereal straws, crop stubbles,
leaves, stems, farm weeds, grasses, forest litters, animal beddings, dung as well as household garbage
etc. As a source of plant nutrient the value of compost will depend on the composition of the plant
materials used in composting.
 Preparing farm compost:
 Selecting composting materials
The plant materials having low C: N ratios are chosen, e.g. maize stalk, rice straw, green material
from legumes.
 Selection of a compost site
Composting site should be located near the fields or source of material and should be on a raised and
well-drained place to prevent from direct sunlight and heavy rainfall.
a. Heap Method:
During monsoon a heap method of composting is preferred because the pits are easily water logged. It
is made in wet climate region.
Step:
 Construction of a compost heap
The size of the heap should be determined by the amount of
materials available for composting. Construction of compost
heaps which measure 1.5 m high, 2 m wide as like roof-type of
structure that helps to drain off any rainwater and thus prevent
water logging especially in wet climate.
 Prepare organic matter such as leaves, cut grass, and corn
stalks by cutting or shredding them into small pieces.

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 Pile the compost materials on the top of wood, old branches or rocks to ensure good aeration up to a
height of about 30 cm.
 Apply a thin layer (about 5 cm thick) of organic materials and spread a layer of fresh cow- dung,
slurry, single super phosphate, lime and effective micro-organism or urea etc. on it.
 Repeat this step until several layers of organic materials have been formed with the height of heap
1.5 m and insert bamboo poles along the heap to serve as air vents and then enclose the heap with a
thin cow- dung mud plaster.
 Remove poles after 1 to 2 days when the plaster has hardened, seal the holes after 4-5 days when
temperature in the heap is risen 60-700
C.
 After about 2 weeks, open the heap, turn and reseal.
 Finally the compost is ready for use after 3 month.
b. Pit method
 Dig a pit of dimension 2*2*1 m. The size of pit may vary according to the amount of compost to be
made.
 Fill the pit about 30 cm deep with plant materials. The plant materials, if dry, wet them so that it
contains about 50-70% moisture.
 Components such as animal manure, beddings and urine (or 1 part livestock manure to 10 part water)
along with a few handful of lime and some surface soil or previously prepared compost should also
be added and mixed. The mixture should be applied in thin layers every 30 cm.
 Repeat the steps 2 and 3 until the pit is filled 50 cm or more above the surface of the soil.
 Plaster the rounded heap and cow dung slurry.
 After 3 months remove the materials from the pit and place it in the heap and re-plaster as above.
 After 1 or 2 months the compost will be ready to use in the field. Principally, the more farmer turns
his compost from the pit, sooner the farmer gets the compost to use in the field. The one month
turning method as in FYM can be used for compost preparation.
3. Vermicompost
Compost that is prepared with the help of earthworms (Pheretima posthuma) is called vermin
compost. Earthworms consume large quantities of organic matter and excreted soil as casts. The
weight of the material passing through the body each day is almost equal to the weight of the
earthworm. The casts of earthworm have several enzymes and are rich in plant nutrients, beneficial
bacteria and mycorrhizhae. On an average vermicompost contains 3%, 1% and 1.5% N, P2O5 and
K2O respectively.
4. Green Manures
Green undecomposed plant materials used as manure into the soil for the purpose of improving soil
physical, chemical and biological environments is called green manure and the process is called
green manuring. Annual leguminous crops as well as green leaves, twigs or succulent stems of non-
leguminous perennial trees or shrubs are used for green manuring.
Kinds of green manuring
1. Green manuring in situ method
2. Green leaf manuring or Cut and carry method

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1. In situ green manuring
It can be defined as a system by which green manure crops are grown and incorporated into the soil
of the same field that is to be green manured, either as a pure crop or an intercrop with the main crop.
In this system, green manuring plants, especially legume species are grown in the field and they are
slashed and incorporated in the same field where they were grown. Dhaincha (Sesbania spp,
Sesbania rostrata), sunhemp (crotolaria juncea), guar (Cyamopsts tetragonoloba) are the most
commonly used green manure species in Nepal.
2. Green leaf manuring
Green leaves and twigs are collected from the forest areas and leguminous trees which are grown on
the boarder of the fields and other vacant places of the farm and provided green leaf and twigs of
trees or shrubs and herbs to the field for manuring purpose is known as green leaf manuring.
Leguminous trees such as ipil-ipil, neem (Azadiracta indica), Gliricidia
Advantages of Green manuring
 It helps to add organic matter in the soil.
 Return the nutrients on the upper soil layer from the lower surface of soil.
 Improve the physical properties (aeration, structures, water holding capacity etc) of soil.
 It decreases the soil erosion, runoff and help to penetrate the rain water.
 Green manuring crops hold nutrients (macro and micro) that would otherwise be lost by leaching.
Disadvantages of green manuring
 Green manuring needs sufficient water during incorporation for proper decomposition.
 Green manuring crops (in situ) causes loss of one crop.
 The cost of green manuring may be more than the cost of commercial N fertilizer.
 It may increases the problems of diseases, insects, pest and nematodes.
List of indigenous green manuring species commonly used in Nepal and their nutritive values:
Local name Scientific name
Nutrient concentration (%)
N P2O5 K2O
Asuro Adhatada vascia 4.3 0.88 4.49
Titepati Artemisia vulgaris 2.4 0.41 4.90
Bakaino Melia azedarach 3.24 0.19 1.76
Kalo Siris Albizia lebbek 2.89 0.65 2.59
Sajeeban Jatropha curcas 2.76 0.32 2.27
Chelaune Brugmansia suaveolens 1.68 0.09 0.37
Seto Banmara E. adenophorum 1.34 0.17 2.75
Dhaincha Sesbania aculeata 2.87 0.22 1.07

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4. Bio-fertilizers:
Bio-fertilizers are defined as preparations containing live or latent cells of efficient strains of
nitrogen fixing and phosphate solubilizing micro-organism used for inoculation of seed, and
application of soil or composting areas with the objectives of increasing the population of such
beneficial micro-organisms and accelerate certain microbial processes to augment the extent of the
availability of nutrients in a form which can be easily assimilated by plants.
Bio-fertilizer is a carrier-based product in which live cells of efficient microorganism are mixed in
maximum number to increase soil fertility and availability of nutrients to plant through seed
treatment or soil application. There are various types of bio-fertilizers like Rhizobium, Azotobacter
and Azospirillum , Blue green algae (cyanobacteria), Azolla etc which can fix N and acts as a bio-
fertilizer augmenting N in the soil.
Advantages of bio-fertilizers. (Why bio-fertilizer??)
 Cheap source of nutrient
It can be called poor man technology. The amount of nutrient supply by bio-fertilizer is cheaper than
chemical fertilizers.
 Supply of micronutrient
 It isn't only supply major nutrients (N, P, K ) but also supply micro nutrient (B,Zn,Cu).
 Supply of organic matter
 Bio-fertilizers like BGA, Azolla produce on an average 8-10 tons of biomass per hacter which adds
to the organic matter to the soil.
 Counteracting negative impact of chemical fertilizer
The negative impacts caused by chemical fertilizers like, environmental pollution and human health
hazards are reduced by using bio-fertilizers because they are eco-friendly, non-toxic and cheaper
natural resources.
 Secretion of growth hormone
They synthesize growth hormone like vitamin B and indol acetic acid which help in seed
germination.
 They help in providing plant nutrients and increase the fertility status of the soil also.
 They enhance bio-mass production and grain yields by 10-20%.
 Algal bio-fertilizer can be used for reclamation of sodic saline soil also.
 They are suitable in organic farming.

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 Types of Bio-fertilizers
Based on the function of bio-fertilizers, they are classified as under:
A Nitrogen fixing bio-fertilizers
1. Symbiotic bacteria containing bio-fertilizer
i) Rhizobium
The most widely used bio-fertilizer is Rhizobium, which colonizes the roots of specific legumes to
form tumor like growth, called root nodules. These nodules act as factories of ammonia production.
The Rhizobium legume association can fix up to 100-300 kg N per hectare in one crop season and in
certain situation can leave behind substantial nitrogen for following crops. Important strains of R.
bacteria are R. japonicum (better for soybean inoculation), R. meliloti (alfalfa), R. leguminosarum
(peas), R. phaseoli (beans).
ii) Azolla
Azolla is free- floating water fern commonly seen in low land fields and shallow fresh water bodies.
Azolla forms a green mat over water. This fern harbors a blue green algae (Anabaena azollae). The
Azolla anabaena association is a live floating nitrogen factory using energy from photosynthesis to
fix atmospheric N amounting to 100-150 kg /ha N from about 40-60 tonnes of bio-mass. Important
strains of bacteria are A. caroliniana, A. nilotica, A. mexicana and A. pinnata.
ii) Azospirillum
Azospirillum lipoferum has associative symbiosis with higher plant system. They donot produce any
visible nodules on the root tissues. The crops, which respond to Azospirillium inoculation are maize,
barley, oats sorghum, pearl millet and forage crops. Its application increases grain productivity of
cereals by 5 -20% and fodders by over 50%.
2. Non-symbiotic
i) Azotobacter
The beneficial effects of Azotobacter bio-fertilizer on cereals, millets, vegetables, cotton and
sugarcane under both irrigated and rainfed field condition have been substantiated and documented.
Application of Azotobacter has been found to increase the yield of wheat, rice, maize, pearl millet
and sorghum upto 30% over control. Apart from N, this organism is also capable of producing
antibacterial and antifungal compounds, hormones and siderophores.
ii) Blue green algae (BGA)
BGA are referred to as paddy organism because of their abundance in the paddy fields. BGA
anabaena Azolla also occurs in symbiotic relation with the aquatic fern Azolla. The utilization of
BGA as a bio-fertilizer for rice is very promising. Blue green algae have contributed greatly to the
enrichment and maintenance of soil fertility in rice fields. On the farm level the algae can contribute
to about 25-30 kg N/ha.

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B. Phosphate mobilizing bio fertilizer
a) Phosphate absorber
i) Mycorrhizae or Vesicular Arbuscular Mycorrhiza (VAM)
Mycorrhiza is a fungal bio-fertilizer. It is a symbiotic association of fungi with roots of vascular
plants. The main advantages of Mycorrhizae to the host plants lies in the extension of the penetration
zone of the root fungus system in the soil, facilitating and increase phosphorus uptake.. Endotrophic
Mycorrhizae have been sown to be present in a wide range of horticultural species including Apple,
Walnut, Almond, Citrus, Avocado, Strawberry and Grape. Mycorrhizal fungi's assists the uptake of
phosphate and trace metals and possibly influence water and nutrient.
b) Phosphate solubilizers
A group of heterotopic microorganisms are known to have the ability to solubilize P from insoluble
sources. Phosphate solubilizers are Pseudomonas spp, Bacillus megatherium, Aspergillus awamori,
Pencillium digitum, Trichoderma spp etc., which are responsible to solubilize the phosphates in the
soil.
C. Organic matter decomposer
Saprophytes
Saprophytes are those microorganisms that feed by absorbing dead organic matter. Most saprophytes
are bacteria and fungi. The term saprobe is frequently used to indicate saprophytic fungi.
Saprophytes are important in food chains as they bring about decay and release nutrients for plant
growth.
5. Bio gas: The gas produced from cow dung and the water as a result of the anaerobic fermentation is
called biogas. Bio gas contains methane (50%-65%) as most useful components and the remaining
part mostly being carbon dioxide
Figure: A bio gas plant
The digested slurry overflows from the top of the well through an outlet pipe and collects over the
pit. The slurry can be removed periodically and added to manure pit. The bio gas digestion increases
the nutrient recovery rate of the dung. The biogas manure has relatively high nitrogen content than
the FYM.

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Unit4: Plant nutrition
 Essential elements
The elements which are essential for growth, development and reproduction of plants is called
essential plant nutrient. Sixteen elements have been identified more essential for plant growth. Plants
have the ability to build up organic tissues directly from inorganic materials. They live, grow and
reproduce by taking up water and mineral substances from the soil, carbon dioxide from the air,
energy from the sun to form plant tissues
 Criteria for essentiality of plant nutrients
Arnon's criteria of essentiality of elements in plant nutrition. A plant nutrient to be essential, it
should fulfill the following three criteria as proposed by Arnon and Stout (1938).
a. The plant cannot grow or complete its life cycle in absence of the element.
b. The element is very specific and cannot be replaced by other elements.
c. The element plays a direct role in metabolism. The element must be shown to be directly involved in
the nutrition of plant, that is, to be a constituent of an essential metabolite or at least required for the
action of essential enzymes.
 Classification of plant nutrients:
Plant nutrient can be classified into three groups
1. Basic Nutrients (structural nutrient)
The basic nutrients viz. carbon, hydrogen and oxygen constitute 94% of total dry matter
of plants. Among them carbon constitute 45%, hydrogen (6%) and oxygen (43%).
2. Macronutrients
Elements which are required by plants in considerable concentrations (greater than 1 ppm) are called
macronutrients. Macronutrients are needed in large amounts and large quantities have to be applied if
the soil is deficient in one or more of them. E.g. N (1-3%), P (0.005-1%), K (0.3-6%), S (0.05-1.5%),
Ca (0.1-4%), Mg (0.004-1%). Soils may be naturally low in nutrients, or may become deficient due
to nutrient removal by crops over the years, or high yielding varieties (HYV) are grown which are
more demanding in nutrient requirements than local varieties.
a. Primary elements: The elements that plant utilized greater quantities from soil and these to be
replaced in greater quantities. E.g. N, P, K
b. Secondary elements: The macro-elements that plant utilized in lesser quantities from soil compared
to primary nutrients. E.g. Ca, Mg, S.
3. Micronutrients
Elements, which are required by plants in minute quantities (0.001-1000 ppm) or plants also take
them up in considerable amounts are termed micronutrient or trace elements e.g. Mn, Cu, Zn, B, Mo,
Cl, and Fe. They are the part of the key substances in plant growth and are comparable with the
vitamin in human nutrition. Their plant availability depends primarily on the soil reaction.
Beneficial elements: Essential for particular crop, but not for all crop. They are: Na (in sugar beet),
Cobalt (legumes), Silicon (paddy), Vanadium (asparagus), Nickel and Selenium.

A HANDNOTE OF
Soil Management, Conservation and Environmental Science
@TIRTHA RAJ PAUDEL & SURAJ BHARATI @ 2075
44
Table: Essential plant nutrients and their forms absorbed by plants.
Elements Form absorbed Concentration in
plants
Soil pH
availability
Primary sources
Structural nutrients
Carbon(C) CO2 45% - Carbon dioxide in
air
Hydrogen (H) H2o 6% - Water
Oxygen (O) CO2 , O2, H2o 43% - Water , air
Primary nutrients
Nitrogen (N) NO3
-
, NH4
+
1-6% 6-8 Organic matter,
atmosphere
Phosphorus (P) H2PO4
-
, HPO4
2-
0.05-1.0% 6.5-7.5 &
8.5-10
Soil minerals ,
organic matter
Potassium (K) K+
0.3-6% 6-10 Soil minerals
Secondary nutrients
Calcium (Ca) Ca2+
0.1-3% 7-10 Soil minerals,
limestone
Magnesium
(Mg)
Mg2+
0.05-1.5% 7-10 Soil minerals,
limestone
Sulfur (S) So4
2-
0.05-1.5% 6-10 Organic matter,
rain water
Micronutrients
Iron (Fe) Fe2+
, fe3+
100-1000 Ppm Less than 6 Soil minerals
Manganese (Mn) Mn2+
5-500 Ppm Less than
6.5
Soil minerals
Copper(Cu) Cu2+
2-75 Ppm 5-7 Soil minerals ,
organic matter
Zinc (Zn) Zn2+
5-1000 Ppm 5-7 Soil minerals,
organic matter
Boron (B) H3Bo3 2-75 Ppm 5-7 Organic matter ,
tourmaline
Molybdenum
(Mo)
MoO4
2-
0.01-10 Ppm 7-10 Soil minerals,
organic matter
Chlorine (Cl) Cl-
0.05-3% - Rain water

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 Functions and deficiency symptoms of macro and micro nutrients in crops
NOTE:
 Mobile nutrients in Plant: N, P, K, Mg, Cl, Mo
 Immobile nutrients in Plant: Ca, B, Fe, Mn, Cu, Zn, S
Mo and S are also regarded as semi-mobile element by some soil scientists. P becomes semi-mobile in
cold season.
A. Structural nutrients
Functions of carbon, hydrogen, oxygen in plants
Carbon, hydrogen and oxygen are obtained by plants from air and water. C and H absorbed in
combined form, oxygen partly taken from molecular form. These 3 elements for all life form about
95% of the dry weight of plants.
Functions
 They are major constituents of all organic chemical compounds of which the plant is made and they
are concerned with different metabolic reactions vital for plant growth and development.
 They provide structure to and give shape to plants.
 O2 is required for photosynthesis.
 They play key role in providing energy required for growth and metabolism of the plant.
The bulk of energy required for these processes is derived from oxidative breakdown of
carbohydrates, fats, and proteins during cellular respiration.
B. Macronutrients
1. Nitrogen:- Nitrogen is foremost important element which limits crop production. Plants normally
contain between 1-5% by weight. It is absorbed by plants in the forms of NO3
-
(nitrate) and NH4
+
(ammonium) and also in amide form (from urea). In moist, warm and well-aerated soils, NO3
-
form is
dominant.
Sources: Organic matter(5%), Inorganic fertilizer (urea:46%,DAP: 18% and ammonium
sulphate:21%) , atmosphere, Lightening and biological fixation.
Function:
 It imparts vegetative growth vigorously and dark green color to the plants.
 It is part of DNA molecule thus helps in cell division and reproduction.
 It is constituent of metabolically active compounds like amino acids, protein, nucleic acids, purines,
enzymes and co-enzymes and alkaloids.
 It increases crop yields.
 It is the integral part of chlorophyll, which is primary absorber of light energy needed for
photosynthesis. The basic elemental unit of chlorophyll structure is porphyrin ring system; composed
of four pyrole rings each containing one N and four carbons.
Deficiency of N
Nitrogen is a mobile element in the plant. Thus, shows deficiency symptoms first in older parts of
plants or on matured leaves. However symptoms spread rapidly to young leaves. When plants deficit
in N.

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a) Plants become stunted and dwarf.
b) Nitrogen deficient plants mature early and crop quality and yield are reduced.
c) Chlorosis of lower leaves, stunted and slow growth and necrosis of older leaves.
d) In severe N-deficiency, the leaves will turn brown and die. In corn, the lower leaves usually fire or
turn brown beginning at the leaf tip and progressing along the mid-rib until the entire leaf is dead and
appears 'v' shape.
e) Fig: N
deficiency in barley. Top leaves are N deficient, bottom leaves are normal.
f) Rapid crop yield decline.
g) Flowering and fruit setting are adversely affected hence; size and quality of the fruit are poor.
h) Few tillers, slender stalks, short heads and grains with low protein content in cereals.
i) Leaf curling and small tubers in potato.
 Excess of N
• High N produces succulence in plants & enhances their sensitivity to water & temperature stress.
• .High N-plants also become susceptible to lodging, pathogen & pests attack.
2. Phosphorus
It is also categorized into major nutrient. It occurs in most of the plants in concentration of 0.1-0.5%
and plants absorb P in the form of H2PO4
-
or HPO4
2-
. H2PO4
-
is most abundant over the range in soil
pH value. Absorption of H2PO4
-
is greatest at low pH value whereas uptake of HPO4
2-
is at higher pH
value.
Available forms of phosphorus for plants are:
 H2PO4
-
is dominant at pH < 7.
 HPO4
2-
is dominant at pH > 7.
 H2PO4
-
= HPO4
2-
at pH 7.
Functions:
a) Stimulate early vegetative growth and increase root growth.
b) Stimulates seedling development and root formation.
c) Increase quality of certain fruits, forage, and vegetable and grain crops and increases disease
resistance.
d) Help in early maturity of grain crops and promote seed production.

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47
e) It is involved in energy storage and transfer in metabolic reactions of the cells.
f) It is the constituent of nucleic acids, phytin and phospholipids in plants and also ATP, protein, RNA,
DNA and enzymes.
g) It is involved in cell division and the transfer of heredity character by chromosomes.
h) Helps in greater strength of cereal straw, it increases tolerance to root-rot disease in small grain crops.
Deficiency
Phosphorus is a mobile in plant system. However it becomes semi-mobile during winter season in
both soil and plant. Symptoms appear on older leaves and P redirected to young leaves.
 Plants turn dark green and appear stunted.
 Older leaves affected first and may acquire a purplish discoloration due to accumulation of sugars in
P deficient plants which favors anthocyanin synthesis in some cases, leaf tips brown and die.
 Plants become weak and maturity is delayed
 Leaf expansion and leaf surface area inhibited causing leaves to curl and be small.
 Wheat and small grains with P deficiency tend to be stressed and predisposed to root rot diseases.
 Weak straw of cereals.
 Purple leaves of corn at seedling stage and purpling of guava.
 Appearance of purple/bluish green interveinal blotches on mature leaves.
 Poor quality fruits, forage, vegetables and grain crops.

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48
Potassium (K)
Its concentration in plant cell varies or ranges from 1 to 5%. It is absorbed from soil solution on the
K+
ion. Plant requirement for this element is quite high. Potassium does not combine with other
elements to form such plant compounds as protoplasm fats and cellulose. It exists in mobile ionic
form and its functions appear to be catalytic in nature, thus called chemical policeman.
Functions:
 It is essential for translocation of sugars and formation of starch.
 It is required in the stomatal movement i.e. opening and closing of stomata.
 It promotes root growth, produces larger, more uniformly distributed xylem vessels throughout the
root system.
 It increases plant resistance to diseases.
 It increase size and quality of fruits, nuts and vegetables and improves winter hardiness of perennials.
 Plays a catalytic role by activating a number of enzymes and coenzymes catalyzing the incorporation
of amino acids in protein synthesis.
 Enhances the synthesis and translocation of carbohydrate (CHO) thereby encouraging cell wall
thickness and stalk strength.
 K provides much of osmotic "pull" that draw water into plant roots.
 Increases the sugar content of sugarcane and sugar beet.
 Helps in organic acid neutralization.
 Helps in photosynthate transport and deposition, photorespiration and phosphorylation.
Deficiency of K
It is mobile element so deficiency symptoms first occur on older leaves. K deficiency does not
immediately result in visual symptoms (hidden hunger). Initially there is only reduction in growth
rate.
a) Chlorotic symptoms typically begin on the leaf tip, but unlike ‗V‘ affect caused N-deficiency, K-
deficient Chlorosis will advance along leaf margins towards the base, usually leaving the midrib alive
and green. As the deficiency progresses, the entire leaf turns yellow.
b) Small white or yellow necrotic spots may also develop, beginning along leaf margins.
c) Reduces straw or stalk strength in small grains and corn, resulting in lodging problems, reduced
disease resistance and reduced winter hardiness of perennial crops.
d) Produced grains will be low in protein.
e) White spots on alfa-alfa leaf edges.
f) Small tubers in potato due to low sugar accumulation.
g) Lack of K in wetland rice increases the severity of foliar diseases such as sheath blight, brown leaf
spots etc.
h) Poor opening of cotton bolls.

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4. Calcium (Ca)
It is absorbed in the form of Ca2+
and is abundant in leaves. Its normal concentrations range from 0.2
to 1.0% it exists as deposits of calcium oxalate, carbonate and phosphate in cells vacuoles. Calcium
pectate is one of the components of the middle lamella of cell wall.
Function:
 It is essential part in cell wall and membranes and is required for the formation of new cells.
 It improves the permeability of cell membranes.
 It enhances the uptake of nitrate-N and thus it is interrelated with N-concentration in plants.
 Directly involved in chromosome stability and is the constituent of chromosome structure.
 It affects carbohydrate translocation in plants.
 It improves root growth as well as microbial activity.
 It increases Molybdenum availability to plants and uptake of other nutrients.
 Promotes early root formation and growth.
 Neutralizes poisons produced in plants.
 Deficiency symptoms of Ca
It is considered to an immobile element in plants. There is a poor supply of Ca to fruits and storage
organs. The deficiency symptoms of calcium in plants are:
 Failure of the terminal buds and root tips of plants to develop.
 An empty peanut shell because of failure to develop. Help in pegging while peanut folded new
leaves, the tips of emerging leaves are almost colorless and are covered with sticky gelatinous
substances, which causes them to adhere to one another.
 Collapse of new petioles in young cotton and soybeans.
 Soft nose in mange, blossom end rot of tomato, cavity spot in carrots, black heart of celery, internal
tip burn of cabbage, bitter pit in apple, Jonathan spot in apple.
 Tobacco leaves are starchy, thick soft and papery when Ca is deficient in midrib.
5. Magnesium (Mg)
It is absorbed in the form of the Mg2+
ion. Its concentration in plant varies from 0.1 to 0.4%. Mg is
the only mineral constituent of chlorophyll.
Functions:
 Essential constituent of chlorophyll structure which is located at the center of the porphyrin ring.
 Activator of many plant enzymes which are involved in energy transfer, glycolysis, respiration, and
sulfate reduction.
 Balances high use of potassium from fertilizers and manures.
 Major constituent of chromosome which is bearer of hereditary character.
 An essential constituent of polyribosome concerned in protein synthesis.
 Helps in the synthesis of oil in plants. It increases oil content of several crops.
 Helps in metabolism of CHO and synthesis of protein.
 Neutralizes organic acids in plants.
Deficiency of magnesium:

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50
It is mobile element and is readily translocate from older leaves to younger plant part in the early
time of a deficiency.
Deficiency symptoms are
 Interveinal Chlorosis and leaf margins bearing yellow or reddish purple while the midribs remain
green.
 In wheat, distinct mottling as yellowish green patches occur
 Leaves of sugar beets and potatoes become stiff can brittle, veins are twisted.
 Lower leaves of cotton may develop reddish purple color, which gradually turns brown and finally
necrosis occurs.
 Weak stalk with branched roots.
 Grass tetany: low Mg content of forage crops, particularly grass forages, can be a problem in some
areas. Cattle consuming low-Mg forages may suffer from hypomagnesaemia (grass tetany). General
symptoms of grass tetany include grazing of cattle away from herd, muscular twitching, irritability,
wide eyed staring, and convulsions and ultimately death occurs.
6. Sulphur (S)
Sulphur is absorbed by plants roots as sulphate ion (SO4
2-
). The concentration of sulfur in plants
range from 0.1 to 0.4%.
Functions
 Is required for the synthesis of sulfur containing amino acids (cystine, cysteine, methionine), which
are essential compounds of proteins. It is required in high quantity especially by crucifereae family.
 Activates certain enzyme systems and is component of some vitamin (vit. A).
 Found in mustard oil glycosides, which imparts characteristic odour and flavor to mustard, onions
and garlic.
 Is part of ferrodoxins, a type of iron Sulphur containing protein occurring in the chloroplast.
 Helps in the synthesis of chlorophyll.
 Enhance the oil formation in crops such as flax, mustard and soybean.
 Essential for nodule formation in legumes.
 Needed for synthesis of metabolites, co-enzyme-A, biotin, thiamin, vit B-12 and glutamine.
Deficiency symptoms of S
Sulfur is immobile element in plant. Leaf becomes uniformly yellow as the chlorophyll content
declines.
Deficiency symptoms are:
 Younger leaves initially turn light green to yellow (Chlorosis), later the entire plant turns yellow.
 Retarding effect on plant growth, stunted and stemmed and spiny plants.
 Accumulation of NO3
-
in plant and a reduction of protein due to S deficiency.
 Uniformly Chlorotic symptoms due to S-deficiency resemble to N. However, N deficiency symptoms
appear on matured leaves while S –deficiency occurs on young leaves.
 Reduction in oil content of oil seed crops such as mustard, rapeseed, peanut etc.

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51
 Development of reddish color on underside of leaves of cabbage and rapeseed. As deficiency
progressed, in cabbage there is a reddening and purpling of both surfaces of leaves.
C. MICRO NUTRIENTS
7. Boron (B)
It is only non-metal nutrient. Its concentration in monocot varies between 6 and 18 ppm while in
dicot varies between 20 and 60 ppm. It is absorbed by plants in the form of boric acid (H3BO3).
Functions of Boron:
 Plays an essential role in development and growth of new cells in plant meristems.
 Involved in regulating metabolism of carbohydrate in plants.
 Effective in increasing pollen viability thus contributing to increase fruit set.
 Help in translocation of sugar, starch, nitrogen and phosphorus.
 Play role in the synthesis of amino acids and proteins for formation of plant hormones.
 Help in nodule formation in legumes.
 Regulates the metabolism of carbohydrates.
Boron deficiency
Boron is immobile element in plant; consequently deficiency symptoms of B first appear on young
parts of plants (leaves) when become uniformly yellowing or Chlorosis (decline chlorophyll).
Specific deficiencies are
 Youngest leaves become yellow, losing more color at base than at tip of leaves.
 Rotting of roots, tubers and fruits.
 Chlorotic young leaves and death of main growing point (terminal bud).
 Leaves may develop dark brown, irregular lesions that will progress to leaf necrosis in severe cases.
 Leaves and stem become brittle and distorted and leaf tips tend to thicken and curl.
 Corky apple, uneven thickness of peel of citrus, lumpy and gummy fruits is caused by B deficiency.
 Darken (black heart) in root crops such as radish turnip, potato etc.
 In cauliflower and broccoli, leaves rolling and deformed buds, hollow stem, browning of curds
caused dead heart in cauliflower.
 Poor-pollination in corn leads to small-undeveloped cobs in one stalk, barren cobs, barren stalks.

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52
8. Iron (Fe)
It is expressed as percentage of Fe2O3.The suffering range of iron on plants normally between 50 and
250 ppm iron can reach plant roots as Fe2+
, Fe3+
and as organically complexed chealeted iron.
Functions of iron:
 Structural compound/component of porphyrin molecules, cytochrome, hormatin, ferrochrome,
leghaemoglobin.
 Activator of biochemical process such as respiration and photosynthesis.
 Structural component of ferrodoxin that are stable Fe-S protein.
 Found in enzyme system, cytochrome oxidase, catalase and perioxidase.
 Helpful for the formation of chlorophyll and hence for photosynthesis.
 Required for heme protein formation in legumes.
 Need for respiration and energy transfer in plant.
Deficiency of iron
Iron is immobile element in plant system. It does not move out of old leaves even under deficiency.
Chlorosis of young leaves is an early symptom of Fe deficiency.
Deficiency symptoms in plants are:
 Reduction in chlorophyll production and is characterized by interveinal chlorosis with a sharp
distinction between veins and chlorotic areas in young leaves.
 Fig: Interveinal chlorosis due to Fe-deficiency
 As the deficiency develops, the entire leaf becomes whitish yellow and progress to necrosis.
 Stalks are short and slender.
 Deficiency symptoms of iron are most frequently seen in crops growing in calcareous or alkaline soils
(blenching of rice seedlings in calcareous soil).
 Yield of citrus, soybean, corn and vegetable crops is suffers from iron deficiency.

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53
9. Manganese (Mn)
Normal concentration of this element in plants from 20-50 ppm. It is absorbed by plants as the
manganous ion (Mn2+
).
Functions of Mn:
 Essential constituent of nitrate reductase and hydroxylamine reductase.
 The metabolism of N and electron transfer in photosynthesis II.
 Activation of enzymes participating in the Kelvin cycle.
 Acceleration of germination and maturity.
 Assists in chlorophyll production.
Mn deficiency:
Like iron, manganese is a relatively immobile element. The deficiency symptoms of this element
usually are showing first in the young leaves.
Mn deficiency symptoms in plants
 Interveinal Chlorosis in young leaves however, unlike Fe there is no sharp distinction between veins
and Chlorotic areas.
 Mn deficiency of several crops has been described by terms as grey speck of oats, speckled
yellowing of sugar beets (all in leaves).
 Chlorosis extends between the lateral veins towards the midrib.
 Reduced lignifications of stem wood have been observed in trees causing lateral branches to weep.
 Plants are injured by excessive amounts of Mn. Crinkle leaf of cotton is Mn toxicity in highly acid
red and yellow soils.
10. Copper (Cu)
Properties of copper that make it essential to plant nutrition are somewhat similar those of iron. Its
normal concentration in plant tissue varies from 5 to 20 ppm. It is absorbed by plant in cupric ion
(Cu2+
). Copper salts and complexes are also absorbed through leaves.
Functions of Copper:
 Indirect effect on nodule formation.
 Transport of photosynthetic electron mediated by plastocyanin.
 It is activator of several enzymes such as oxidase, tyrosine, lactase and ascorbic acid oxidase.
 Improves the flavor of fruits and vegetables.
 Terminal oxidation by cytochrome oxidase.
 Increase sugar content of citrus.
 Intensification of color in apples, carrots, spinach and wheat.
 Needed for chlorophyll production, respiration etc.

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54
Deficiency of Cu
It is an immobile element so deficiency symptoms occur on younger leaves.
Deficiency symptoms are
 Chlorosis in younger leaves, stunted growth, delayed maturity, lodging and in some cases melanosis
(brown discoloration) occurs.
 In cereal, grain production and fill is often poor, and under severe deficiency, grain heads may not
even form.
 Cu-deficient plants are prone to disease severity, specifically to ergot (a fungus causing reduced yield
and grain quality)
 In advance stage of Cu deficiency, Poor pigmentation of fruit.
 In corn youngest leaves, it becomes yellow and stunted pale and the older leaves die back.
 Crops most susceptible to Cu deficiency are: wheat, barley, oats, onion, carrot, spinach, corn and fruit
trees.
11. Zinc (Zn)
The normal concentration of zinc in plant tissue ranges from 25 to 250 ppm. Plant roots absorb Zn as
the ion Zn2+
.
Functions of Zinc:
a) Regulation of auxin concentration in plants.
b) Promotion of synthesis of cytochrome – C.
c) Transportation of carbohydrate and regulation of consumption of sugar in plant.
d) Help in photosynthesis and N- metabolism.
e) Constituent of number of enzymes such as dehydrogenase, phosphodiesterase, carbonic anhydrase.
Deficiency symptoms of zinc in plants
Deficiency symptoms first appear on expanding leaves. Zinc deficiency symptoms are:
a) Zn deficient trees are stunted and leaves are small and crowded (resetting and clustering of leaves at
the top of fruit trees, shortened internodes, leaf size decreased, leaf tip and interveinal patches of
tissue may become necrotic or whiter areas between the veins of leaves, early loose of foliage).
b) In corn and sorghum, zinc deficiency is called white bud, in cotton, it is known as little leaves,
molted leaves in citrus and grasses, Khaira disease in rice.
c) Browning of nut trees, yellows of walnut, rosette of apple and dead spot on tobacco leaf.
d) Malformation of fruit often with little or no yield.
Crops classified as being very sensitive to zinc deficiency are grapes, onion, pine, soybean, cotton,
potato, sugar beet, tomato etc.

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55
12. Molybdenum (Mo)
Molybdenum content of plant material is less than 1 ppm. It is available to plant as MoO4
2-
form.
Functions of molybdenum:
 Essential component of enzyme nitrate reductase in plants.
 Structural component of nitrogenase, which is actively involved in N – fixation by root nodule
bacteria of leguminous crops.
 Essential role in iron absorption and translocation in plants.
 Involved in conversion of inorganic P to organic form in plants.
Mo deficiency
The deficiency symptoms of Mo resemble the early symptoms of N deficiency but unlike the N
deficiency, Mo deficiency first appears in young leaves.
Deficiency symptoms of Mo are:
 Mo deficiency inhibits nitrate reductase in ordinary plants and N- fixation in legumes. Mo is an
essential constituent of key enzymes in both processes. Plants cannot convert NO3
-
into amino acids.
 Leaves are pale green and have rolled or curved (cupped) margins. Leaves of cauliflower become
narrow and called whiptail.
 Yellow spot of citrus leaves.
13. Chlorine (Cl)
It is absorbed by plants as the chloride (Cl-
) ions through both roots and aerial parts.
Functions of Chlorine:
 Involved in oxygen evolution in primary photosynthetic reaction.
 The counter ion during rapid K fluxes, thus contributing to turgor of leaves and other plant parts. It is
an active osmotic agent.
 Required for growth and sugar synthesis in sugar beets.
 Involved in photochemical reaction in photosynthesis.
 Need for the depression of root rot infection in wheat wheat and stalk rot in corn.
Deficiency of chlorine
Chlorosis of the younger leaves and overall wilting of plants are the two most common symptoms of
chlorine deficiency. Chorine deficiency seldom occurs because of the presence of Cl-
ion in rain
water. Deficiency symptoms are:
 Partial wilting and loose of leaf turgor in plants.
 Necrosis, leaf bronzing, reduction in root growth, failure to fruit and stunted growth.
BENEFICIAL ELEMENTS

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56
 Cobalt (Co)= legumes
 Sodium (Na)= sugarbeet
 Silicon (Si)= cereal
 Vanadium (Va)= asparagus
Table of some important function and deficiency of essential nutrient
Nutrient specific function specific deficiency
N cell division and
multiplication
cholorosis, older leaves
affected first
P Early maturity, increase
root growth and cell
division and transfer of
hereditary material
delayed maturity,
Reddening or purpling of
lower leaves
K Help in different
metabolism, provide
osmotic pull and tuber
growth
Cholorosis in leaf, small
sized tuber
Ca Improve cell membrane
permeability, Enhance
uptake of nitrate N,
Neutralize poison produce
in plants
Dieback of terminal bud,
young leaves distorted,
blossome end rot in tomato
Mg neutralize organic acid in
plants, increase oil contents
of oil crops
Yellow discoloration
between veins in older
leaves
S Impart in taste and smell of
plants, Synthesis of oil
leaves including veins turn
pala green in younger leaves
B Help in nodulation in
legumes, Helps in
pollination in wheat and
fruit set
Witches broom, hollow
heart in peanut, Black heart
in root crops and dead heart
in cauliflower
Fe Require hame protein
formation in legumes
interveinal chlorosis, mottle
leaf and yield reduced
Mn accelerate germination and
maturity
Grey speak of oat,
Cu improve the flavor of fruit
and vegetables, increase
sugar content and
intensification of color
Bunchy top of alfalfa, white
tip of cereal and exanthema
in citrus
Zn Regulate auxin
concentration, helps in
synthesis of cytochrome-c
White bud in maize, sickle
leaf in groundnut and
Khaira disease of rice
Mo helps in N fixation in
legume
Whip tail in
cauliflower,interveinal
chlorotic
 SOIL FERTILITY EVALUATION

A HANDNOTE OF
57
Soil fertility evaluation is the process of evaluation or determination of level of nutrient status and its
productivity in given soil. It is necessary to maximize production with better management of land
resource. Successful farmers should know the level of fertility of their farm lands and the nutrient
requirements of the crops to be grown. It is necessary to know the amounts and kinds of fertilizers to
use because unnecessary fertilizer is expensive and the worng fertilizer may also be harmful.
Soil fertility
It is the capacity of soil to provide all essential elements for specific crop production in an easily
available form and in proper proportion. All fertile soil may not be productive soil because it is
affected by soil pH, structure, texture and water content.
Soil productivity
It is the capacity of soil to produce maximum yield of a specified plant/crop or a sequence of crop
under specified system of management.
Differences between soil fertility and soil productivity
Soil fertility Soil productivity
It is the capacity of soil to provide all
essential elements for specific crop
production in an easily available form & in
proper proportion.
It is the capacity of soil to produce
maximum yield of a specified plant/crop or
sequence of crops under specified system of
management.
It deals with nutrient status of the soil only. It is combined effect of all production
factors.
All fertile soils may not be productive due to
draught, water logging, pH,
microorganisms etc
All productive soils must be fertile.
It can be evaluated by soil test in the
laboratory
It cannot be evaluated by soil test in the
laboratory
It is an inherent property of soil It isn't inherent property of soil
It depends upon physical, chemical and
biological factor of soil
It depends upon location fertility and
physical condition
Most frequently used soil evaluation methods are
1. Visual symptoms analysis
2. Plant tissue analysis
3. Fertilizer trails in field
4. Green house trials
5. Microbiological test
I. Mitscherlich's test
II. Aspergilius niger test
III.Azotobactor plaque test
6. Soil testing

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58
1. Visual symptoms analysis ( Nutrient deficiencies)
It is easy, quick and most used method of evaluation based on each nutrient has characteristic
symptoms which can usually be detected by trained soil scientist/agronomist. Some plants are better
indicators o nutrient deficiencies than others and some nutrient deficiency symptoms are easy to
identify than others.
Problems of visual symptom evaluation
 Expression of particular mineral deficiency may differ from one type of crop to another
 When multiple deficiencies are present, identification becomes difficult
 Damage done by insect, disease and mechanical injury can produce symptoms that may be mistaken
for nutrient deficiency
 Toxic effect of certain elements or damages done by herbicide may mistake for nutrient deficiency.
 Expertise knowledge is necessary to identify typical nutrient deficiency in the field
 This test may not be adopted in hidden huger condition(Indicate only severe deficiency after yield
potential has already reduced)
e.g.
N= Plant become stunted and leaf Chlorosis
P= Appearance of purplation on mature leaves
K= poorly opening of cotton balls, weaking of straw in grain crops
Ca= empty cell of groundnut, Blossomed end rot in tomato
B= Black heart of cauliflower
Zn= Khaira disease in rice
Mn= Whip tail of cauliflower
2. Plant tissue analysis
It is also called Rapid plant tissue test. It is quick test or spot test method performed in the standing
crops in fields to appropriate the amount of nutrients present in fresh plant tissue.It usually involves
simple chemical test which produce color that reflects quantitatively the amount of a particular
nutrient present in the plant sap. Generally, by adding authentic reagents on plants tissue or plant sap,
the intensity of develop color is measured or compared. The intensity of color is directly proportional
to amount of nutrient present in plant sap.

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59
Nutrient Reagent Develop color level of nutrient available
Nitrogen 1% DPR( Diphenylamine
in conc H2SO4)
Dark blue
Light blue
No color
Sufficient
Moderately sufficient
Highly deficiency
Phosphorus Ammonium Dark blue
Light blue
No color
sufficient P2O5
Moderately sufficient
Highly deficiency
Potassium sodium cobalt nitrate high turbidity
Slightly turbidity
No turbidity
sufficient K
moderately deficient
deficient K
3. Fertilizer trials in field
Field trials are conducted both at the farmer's field and experimental stations to test the yield
responses of crops due to the application of various fertilizer materials. This allows measuring the
crop nutrient needs under the actual field conditions and the crop response data obtained from at least
three cropping seasons would be helpful in the formulation of general recommendations of fertilizer.
4. Green house trials
This is carried out to studying plant response to nutrient applications made under greenhouse
condition.
 Advantages
 Less time is required than field trail
 It can be done at any time of the year
 Disadvantage
 The environment is an artificial
 Results may have little direct relevance to crop grown in the field
5. Microbiological method
It is usually rapid, simple and requires little space. In this method, the growth of or nutrient uptake by
micro-organisms is measured.
a. Aspergilus Niger test
A little amount of soil is added in suitable flasks in which sufficient amount of nutrient solution is
being kept earlier. The flask is kept at suitable temperature for four days. With the help of weight of
fungus, net assessment of the deficiency of P and K in soil is done.

A HANDNOTE OF
60
b. Azotobacter plaque test
Azotobacter show special behavior in the deficiency of P ,K and Ca . Their number is proportional to
the amount of available nutrients. Thus, soil fertility level can be assessed.
6. Soil testing
It is a standard method for determining the amount and supplying capacity of plant nutrients in the
soil. It is done before crop sowing and due to that this is very useful to apply the nutrient based on
need of crop and status of soil. It is done by
 Quick test (Soil testing Kit): used to estimates qualitatively the nutrient availability in farmer field by
using soil Kit
 Precise Laboratory analysis of soils: Used to estimate exact and precise amount of nutrient present in
soil
Unit: 5. Fertilizers
Fertilizers may be defined as industrially manufactured chemicals containing plant nutrients more
than in organic manures which are able to release nutrients immediately just after application.
Any natural or manufacture substance which supplies one or more of the nutrient elements essential
for the growth and development of the plant is called fertilizer.
They have definite chemical composition with higher analytical value and capable of supplying plant
nutrients in available form.
 CLASSIFICATION OF FERTILIZER
1. Nitrogenous fertilizers
Those fertilizers which are sold in the market for their nitrogen content. They are classified into four
classes on the basis of N present.
a. Nitrate (NO3
-
) containing nitrogenous fertilizers:
 Nitrogen present in these fertilizers is in nitrate form, NO3
-
which are rapidly dissociated to release
NO3
-
ions and readily absorbed by the plants.
 Nitrate ions highly reactive and mobile which are susceptible to losses due to leaching and under
water-logged conditions by denitrification.
 They are alkaline in their residual effect in soil.
E.g. Sodium nitrate (NaNO3) = 16%N
Calcium nitrate Ca (NO3) 2=15.5%

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61
2. Ammonium (NH4
+
) containing nitrogenous fertilizers:
 Nitrogen is present in the ammonium form (NH4
+
).
 Readily soluble in water and absorbed on the soil colloids and thus protected from being washed
away by run off or by leaching.
 Ammonia fertilizers are preferred by the rice crop in the early stage.
 They are acidic in their residual effect in soil.
o These are more resistant to loss by leaching e.g. Ammonium sulphate (NH4)2 SO4 (20%N),
ammonium chloride (NH4Cl) (24-26%N, anhydrous ammonia (NH3) 82% N.
3. Both ammonium and nitrate containing fertilizers:
 These fertilizers contain nitrogen in both nitrate (NO3
-
) and ammonium forms (NH4
+
).
 The nitrate nitrogen is readily available to plants for immediate need, whereas ammonium nitrogen
becomes available to plants at a later stage, when it is transformed by microbiological process to
nitrate.
 They are soluble in water and suitable for most of the crops and soils.
 They are acidic in its residual effect.
 Leaching losses are less.
E.g. Ammonium nitrate (NH4NO3) (33-34% N), Calcium ammonium nitrate (CAN) (20% N).
4. Amide fertilizers:
These fertilizers contains nitrogen in organic compounds as amideNH2 or CN 2
These are organic form of N containing fertilizers which are readily soluble in water
They are not directly available to plants, but easily decomposed and quickly changed into ammonical
and nitrate form by soil microbes
soil microbes
Urea CO (NH2) 2 NH2 NH4
+
or NO3
-
E.g. Urea CO (NH2)2 (46%N), Calcium Cyanamid (CaCN2) (21%N).
B) Phosphatic fertilizers
The fertilizer containing phosphorus is called phosphatic fertilizers. The phosphate content in such
fertilizers is expressed in terms of phosphorus pentaoxide (P2O5), which is readily dissolved in water
and produces salts of phosphoric acid (H2PO4, HPO4). They are classified according to solubility and
availability to crops:
a) Water soluble or monocalcium phosphate (Ca (H2PO4)2):
These fertilizers are available in the form of monocalcium phosphate of ammonium phosphate. Water
soluble phosphates can be absorbed quickly by plants. They should be used on neutral to alkaline
soils, e.g. single super phosphate (SSP) (16% P2O5),Double super phosphate(DSP)(32%), Triple
super phosphate(TSP) (46-48% P2O5), Ammonium phosphate (20% P2O5).
c) Citric acid soluble or dicalcium phosphate {Ca2H2(PO4)2}:

A HANDNOTE OF
62
Citrate soluble phosphates are soluble in acid soils where they convert into soluble phosphates and
there are less chances of fixation.
e.g Basic slag (14-18% P2O5), Dicalcium phosphate (34-39% P2O5).
d) Water and citrate insoluble phosphatic fertilizers/tricalcium phosphate/ Ca3 (PO4)2 Insoluble
It is also known as tricalcium phosphate. These mineral fertilizers contain phosphorus, which is
insoluble in water as well as in citric acid. These fertilizers are suitable in strongly acidic or organic
soils. The phosphorus is very slowly released by microbes at action and remains in soil for long time.
These are suitable for plantation crops like tea, coffee, rubber etc, e.g. Rock phosphate (20-40%
P2O5), and raw bone meal (20-25% P2O5).
C) Potassic Fertilizers
The fertilizer material which contains potassium is called potassic fertilizer. Potassic fertilizer are
grouped in to two i.e. chloride form and non- chloride form
a) Chloride form:
Chloride form of K fertilizers is used extensively in all crops. Potassium chloride is the most common
and cheap fertilizer among potassic fertilizer. e.g. Muriate of potash/ potassium chloride (KCl) (58-
60% K2O).
b) Non- chloride form:
Non chloride forms of K fertilizers are in demand by cultivators growing special crops such as
tobacco, potato and tomato to obtain better quality. e.g. sulphate of potash (48% K2O).
 Composition of inorganic fertilizers
Fertilizer N% P205% K20
1. Nitrogenous fertilizer
Sodium nitrate (NaNO3)
16%
Calcium nitrate Ca(NO3) 2
15.5%
Ammonium Sulphate –(NH4)2SO4
20.6%N
Ammonium Chloride –NH4CL
25%N
Ammonium phosphate---NH4 (H2PO4)
20%
Anhydrous ammonia --NH3
82%
Ammonium nitrate---NH4NO3
33 to 34%
Calcium Ammonium Nitrate (CAN)
Ca(No3) 2NH4NO3
25%
Urea CO(NH2) 2
46%
Calcium Cyanamide CaCN2
21%
2.Phosphotic fertilizer

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63
Single Superphosphate (SSP)
16% P2O5
Double superphosphate (DSP)
32% P2O5
Triple superphosphate (TSP)
46 to 48% P2O5
Ammonium phosphate
20%
Rock Phosphate Ca3 (PO4)2CaF2
20 to 30%
Basic slag
14-18%
Muriate of potash(KCl)
60%
Potassium sulphate(K2SO4)
48-50%
 USES AND BEHAVIOR OF FERTILIZER IN SOIL
1. Nitrogenous fertilizer
a. Urea
Advantages of urea
 High analysis fertilizer (46% N) (≥30% active ingredient)
 Manufacture cost is low
 Low cost per unit of nitrogen
 Reduced handling, storage and transportation cost
 It creates least pollution during its manufacture
 No explosion, no fire hazards during storage
 It is suitable for application either as solid material, solution form or foliar spray
 Use of urea
 It is the ingredient in the manufacture of paints, glues, plastics, paper, textiles, and feeds, weed
control. Urea is high analysis fertilizer since high N (46%N).
 Easy to handle and distribute in field.
 Neither explosion nor fire hazard.

A HANDNOTE OF
64
 Behavior of urea is soil
Urease is a soil enzyme that greatly affects the fate and performance of urea fertilizer. Urea when
apply to soil, rapidly undergoes hydrolysis to produce NH4 and CO2 with the subsequent increase in
pH 7-9. At high pH, ammonia is lost through volatilization (when used at surface and high
temperature). Leaching when apply just prior to heavy rainfall especially in coarse textured soil.
Urease
CO (NH2)2 + H2O (NH4)2CO3.H2O
Urea Hydrolysis (ammonium carbonate)
(NH4)2CO3.H2O + 2H+
2NH4
+
+ CO2 + H2O
Alkaline
NH4 + OH-
NH4OH NH3 + H2O
(Volatilization)
Nitrification
2NH4
+
+ 3O2 2NO2
-
+ H2O + 4H+
(increases acidity)
2NO2
-
+ O2 2NO3
-
Because of H+
ion, soil becomes acidic i.e. 2 moles of H+
for every mol of ammonium nitrogen that
undergoes nitrification to nitrates, thus use of ammonium fertilizers increases soil acidity.
Volatilization
Just after adding urea, it consumes 2H+
, thus increases pH upto 7 to 9. Thus 75% of urea is lost
through ammonia gas volatilization when soil is already in alkaline condition. In case of acidic soil,
pH rises but has lower NH3 loss (40-70%).
b. Phosphatic fertilizer
Use of rock phosphate
 80% rock is used as manufacture of superphosphate and phosphoric acid.
 About 8% is used as fertilizer directly as phosphate rock.
 Few % is poultry and livestock feed.
 Rock phosphate has 30-40% P2O5; hardly 3% used by plants.
Behavior of Phosphatic fertilizers in soil
Leaching
Denitrification
Used by crops, microbes

A HANDNOTE OF
65
Ca 2+
K+
K+
When Phosphatic fertilizers are applied to soils and are dissolved by soil water, reaction occur among
the phosphates, soil constituents and nonphosphatic fertilizer compounds which remove P from the
solution phase and render the phosphates less soluble. This phenomenon is called P- fixation or
retention.
 The granule just been added to the soil and start to absorb water from the soil.
 In the moistened granule, phosphoric acid is formed by the following reactions:
Ca (H2PO4)2. H2O + H2O Ca H (PO4)2. 2H2O + H3PO4
 H3PO4 begin to move out into the soil as more water is being absorbed
 The H3PO4 solution moves into the soil dissolving and displacing Fe, Al or Mn and
leaving insoluble Ca H (PO4)2. 2H2O in the granule.
 The Fe, Al or Mn ions reacts with the phosphates to form insoluble compounds and
residues of Ca H (PO4)2. 2H2O are the primary reaction product remained at the granule.
Behavior of MOP in Soil
It is easily soluble in soil solution upon application. It ionizes to K+
and Cl-
ions. K+
is adsorbed on
exchange complex while Cl-
ion remains in solution or combines with Ca to yield CaCl2 or it may be
leached. Under acidic condition, Cl-
replaces the OH-
ions associated with free iron oxides, therefore
in acidic soil MOP gives better result than K2SO4. It is beneficial since OH-
goes to soil solution and
help to increase pH. Besides, Cl-
ions are less strongly adsorbed on soil colloids than SO4
- -
ions. MOP
can be safely used where the Cl-
ions will not accumulate very much. As explained under soil
organisms, however, muriate of potash is harmful to certain beneficial bacteria.
In alkaline soils, the accumulation of the Cl-
ions are toxic to crops. So in such soils, KCl should be
used along with organic matter.
Application of KCl entails considerable Cl-
ions losses from the soils which in turn causes losses of
equivalent amounts of Ca, although this does not lead to significant decrease in soil pH.
 Integrated nutrient management (INM)
Integrated Nutrient Management refers to the maintenance of soil fertility and of plant nutrient
supply at an optimum level for sustaining the desired productivity through optimization of the
benefits from all possible sources of organic, inorganic and biological component in an integrated
manner
INM involving a mix of organics, biological nitrogen fixation, phosphate solubilizing microbes
and need based chemical fertilizer would be crucial for the sustainability of production and soil as
resource base for it.
 Components of INM
A. Inorganic/ chemical nutrient sources.

A HANDNOTE OF
66
B. Organic nutrient sources.
 Organic manure.
 Green manure.
 Crop residue.
C. Biofertilizers.
 Rhizobium spp.
 PSB.
 PGPR.
 VAM.
Goals of INM
 To maintain soil productivity.
 To ensure productive and sustainable agriculture.
 To reduce expenditure on costs of purchased in puts by using farm manure and crop residue etc.
 To utilize the potential benefits of green manures, leguminous crops and bio fertilizers.
 To prevent degradation of the environment.
 To meet the social and economic aspirations of the farmers without harming the natural resource base
of the agricultural production
Objectives of INM Objectives INM
•To reduce the inorganic fertilizer requirement.
•To restore organic matter in soil.
•To enhance nutrient use efficiency.
•To maintain soil quality in terms of physical, chemical and biological properties.
•To maintain or enhance soil productivity through balanced use of mineral fertilizers combined with
organic and biological sources of plant nutrients.
•To improve the stock of plant nutrients in the soil.
•To improve the efficiency of plant nutrients, thus limiting losses to the environment.
 Soil fertility problems in Nepal
In Nepalese context, we are facing various problem regarding to soil fertility, its condition at present
and it's unsustainability to the future generation. Major challenging problems of soil fertility in Nepal
a. Loss of top soil due to erosion and landslide
Increasing population, intensive cultivation, deforestration and over natural resource utilization lead
the soil erosion and landslide that results loss of nutrient from top soil,
b. Depletion of organic matter
The organic matter content of the Nepalese soil is very low. Low organic matter content of the soil is
due to the loss of organic manure in the field, heavy use of the chemical fertilizer in the accessible
area.
c. Unavailability of chemical fertilizer in time:
Nepal doesn't produce any chemical fertilizer and is fully dependent in foreign country like India. The
import of the insufficient amount of fertilizer and untimely available to the farmer are the main
problem in nutrient management in Nepal.
d. Unbalance and over/ under use of chemical fertilizer:
Improper timing and excess application of chemical fertilizer can causes degradation of soil. Nepali
farmers use blindly chemical fertilizer in the field that degrades soil properties.
e. Mono-cropping
The use of the single crop or no inclusion of legume in the crop rotation is the major problem of soil
fertility in Nepal.
 Management technique of the existing problem of soil fertility:

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The rational management techniques of soil fertility problem to increase crop productivity to meet
the present demand of food without degradation of soil are
a. crop management
Proper crop rotation with legume crop should be followed in order to increase the nitrogen in soil.
b. Use of equipment in proper way
Over use of the heavy machine like tractor should be avoided. Adopt the minimum and zero tillage
practices to conserve the soil fertility.
c. Sustainable agriculture practice
The agriculture practice should be socially acceptable, economically viable, and ecologically sound.
Organic farming as well as use of the compost, vermi-compost should be adopted by the farmer.
d. Optimum use of chemical fertilizer at right time
e. Use of chemical based on soil test and crop needed
f. Adopt integrated nutrient management.
Unit 6: Soil conservation
 Soil erosion:
It is defined as the detachment, transport and deposition of soil particle from one place to
another place by the action of water, wind and animals etc. It is the Loss or depletion of soil both
in relation to quality as well as quantity due to the impact of erosive forces such as rainfall,
runoff, wind etc.
In soil erosion, there are three steps are involved
a. Detachment: Detaching agents are falling raindrop, water and wind flow
b. Transport: Transport agents are flowing water, rain splash and wind
c. Deposition
Causes of soil erosion
a. Desertification
b. over cultivation
c. overgrazing due to livestock pressure
d. deforestation;
e. Natural hazards
• Land topography (steep slopes)
• Climatic factors (intense rain, high velocity wind, strong leaching in humid regions & drought
conditions in dry regions.)

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f. Unsuitable land use & inappropriate land management practices.
g. unbalanced fertilizer use and non-adoption of soil conservation management practices
h. Road construction
 Factors affecting soil erosion
There are various factors responsible causing soil erosion which are
a. Rainfall
Rainfall causes both detachment and transportation of soil particles. Amount, intensity, duration and
distribution of rainfall influence runoff and erosion. High intensity of rainfall of long duration causes
severe erosion.
b. Wind velocity
Wind velocity is directly related with the soil erosion. High wind velocity has more energy to carry
soil particles and thus causes higher wind erosion.
c. Vegetation
The impact of raindrop is reduced by vegetation so it prevent breakdown of soil aggregates. The plant
root bind soil particles thus reduce soil erosion.
d. Soil type
Generally, fine texture (clay soil) soil is subjected to more runoff although low detachments thus
increase soil loss. Sandy and sandy loam soils are easier to detach but difficult to transport as the
particles are heavy.
e. Human activity
Human activities like cultivation on sloppy land, deforestation, over grazing, mining etc disturb soil
aggregate which increases soil erosion
 Types of soil erosion
1. Water erosion
It is the process of detachment, transport and deposition of soil particles from one place to another
place by the action of water.
 Mechanics or Process of Soil erosion by Water
a. Detachment
Impacts of the raindrops are detaching soil particles; destroy soil granulation and splash soil particles.
Raindrops loosen & detach soil granules into pieces, disperse it.
b. Transportation
The flow of water transports the detached soil particles. The ability of the moving water to transport
soil varies as the fifth power of its velocity.
c. Deposition
The deposition is the end of the erosion process. As the runoff speed subside, particles deposits in
reservoirs, riverbeds, flood plains, level lands.
 Types or forms of water erosion/ erosion by water
a. Splash Erosion/raindrop erosion
b. Sheet Erosion
c. Rill erosion
d. Gully Erosion
e. Stream bank Erosion

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a. Splash erosion or raindrop erosion
The scattering of detached soil particles by the raindrop impact on bare soil is called splash erosion. It
is the first step of water erosion results from the direct impact of rain drops on bare soil. Raindrop
acts as a miniature bomb that detaches & splashes soil particles 2m horizontally as well as 20 cm
vertically. It is affected by vegetative cover and mulches, rainfall characteristics and topography.
b. Sheet erosion
It is defined as the uniform removable of soil in the thin layers from surface of soil. It caused by
shallow/thin sheet of water moving over the soil surface with gentle slope
It occurs at slow rate and goes unnoticed/uncared.
c. Rill erosion
It is the advance stage of sheet erosion that lead to form tiny channels of few inch deep in all over
field. It start simultaneously with sheet erosion when channels are large enough to visible. It removes
top soil i.e. organic soil, productive soil and fertile soils.
d. Gully erosion
It is the advance form of rill erosion which developed into large channel with increase in depth and
wide of channel. It is highly visible form of soil erosion
If gully is once formed, it can‘t be smoothed by normal tillage operations .It requires costly structures
& practices to control further advancement.
Stages of Gulley development
 Stage 1: Formation Stage: Begins by downward scour of the topsoil.
 Stage 2: Development Stage: Upstream movement of the gully head
& simultaneous enlargement of width & depth take place.
 Stage 3: Healing Stage: Vegetation begins to grow in the channel and further erosion ceases.
 Stage 4: Stabilization Stage: The gully bed & sides reach a stable slope, sufficient vegetation grows to
anchor the
Slide 1
5. Stream Channel Erosion
Stream water removes bank (bank erosion) and bed (scour erosion). It occurs during periods of high
stream flow. It is very serious problem as the river gets widened every year results destroying huge
cultivated land, settlements, structures. Costly protection measures are required to prevent this
erosion.
NOTE:
Erodibility: It is inherent susceptibility of the soil to accelerate movement.
Erosivity: It is the potential ability of the rain to cause erosion.
The Factors affecting erodivity of rainfall are Intensity, Velocity, Duration, Drop size
Mechanism of transportation of soil by run-off water
2. Wind erosion
The detachment, transport and deposition of soil particles from one place to another place by the
action of wind.
Mechanism of wind erosion
a. Detachment
b. Transportation
c. Deposition

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Mechanism of transportation
I. Surface creep: soil particles roll & slide on the surface.
II. Saltation: Turbulence forces lift soil particles & move them along by a series of steps or jumps.
IV. Suspension: When upward velocity in flow exceeds settling velocity of detached particles then
transportation by suspension occur (Long distance transport)
 Factors affecting Wind erosion are Moisture, Wind turbulence, Soil properties Roughness, Wind
velocity, Vegetation
 Effect / Result or Consequences of soil erosion in Nepal.
The major consequences of soil erosion in Nepal are:
a. Fertility loss and land degradation
This is the direct & primary effect of soil erosion in which soil and nutrient loss resulting in
reduction of land fertility/productivity. It causes the loss of top most fertile soil and left only unfertile
sandy soil that decrease soil fertility and productivity. In Nepal, every year 20 ton/ha of soil is lost
that reduce 300 kg of organic matter, 15 kg N, 20 kg P and 40 kg K.
b. Reduction in crop quality
Crops produced under nutrient deficient soil are of inferior quality as they deficient in essential
nutrients for human & animal growth & development.
c. Flood, landslide and natural hazards
Due to the effect of deforestation, natural disaster and intensive cultivation leads to flood, landslide
and natural hazards and finally become soil erosion. Soil erosion reduces the soil‘s infiltration
capacity, so downstream flooding occurs. During heavy rains, water runs off on surface soil that
causing floods & landslide
d. Pollution
Soil erosion transports the sediments which are greatest source of water pollutant which cause
excessive turbidity in waters, deposition in the Water Rivers and reservoirs, affect on k fish by
clogging gills, Eutrophication (N & P) and carry pesticides, pathogenic bacteria from plant & animal
wastes to agriculture land.
e. Sedimentation on River, agriculture land and reservoir
When soil erosion occurs by water, soil flows with water and finally deposited in reservoir,
agriculture land and river. Sedimentation on reservoirs reduced their life span and capacity. Silt
deposition on irrigation canal that increasing cost of operation and makes river/stream water
cloudy/turbid which prevents sun light from penetration water and reduces photosynthesis and
survival of submerged aquatic vegetation and fish habitat. Sediment on agriculture field destroys the
land/crops and reduces the potentiality for crop production.
f. On-site effects
The effect of soil erosion in that region where it arises is called on-site consequences. The on-site
consequences are
 Removes top soil that reduces the soil fertility and productivity.
 Reduce soil physical, chemical and biological properties.
 Newly planted seeds & seedlings may be washed downhill, trees may be uprooted and small
plant may be buried in sediment.
 Spread pathogens from soil to foliage, from high lying field to low lying field.
 Reduced crop quality.
 Formation of Gulley that is difficulty tillage operation
 fruits and foliage may be damaged by the sandblasting effect of blowing soil

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g. Off-site effects
The effect of soil erosion in that region which is far away from its arises is called off-site
consequences. The major off-site effects are on pollution, water quality, sedimentation, flooding.
 Moves sediments and nutrients off the land,
 Water pollution and sediment deposition in lake , river and agriculture land.
 Eutrophication, contamination with toxic metal & organic compounds, such as pesticides.
 Sediments make water turbid that impact on photosynthesis and survival of the submerged aquatic
vegetation degrades fish habitat.
 Sediments fill up dams, reservoirs & irrigation canals.
 Buildup of bottom sediments can raise level of river, so that flooding becomes more frequent & more
severe.
 Sandblasting effect of wind borne soil particles damage the fruits/foliage.
 Dust storms and air pollutions cause discomforts to people, eye and respiratory infection in cattle and
other livestock.
h. Socio-economic effects
Poor soil causes Poor production that causes poor people.
Soil erosion reduces the soil fertility & productivity (poor soil) and loss of all major nutrient that
results decrease in crop production which is related to economic condition and living standard of
people. Soil loss and poverty are reciprocal in terms of cause & effect. The reduced fertility resulted
from soil erosion reduces the production and income.
 Soil erosion control measures
1. Soil erosion control in Agriculture land
2. Soil erosion control in Forest and rangeland
3. Bio-engineering
4. Engineering method
5. Use of different equipment and machineries (Power tiller and Cultivar)
1. Soil erosion control in Agriculture land
The major soil erosion control measures in Agriculture land are
a. Conservation tillage
Conservation tillage involves the left of crop residue in the field that reduce the intensity and
frequency of tillage. It provides the less exposed of soil to erosive factor and reduce the speed of
run-off and improve the soil fertility and soil structure. It is done by Minimum tillage, zero tillage,
contour farming.
b. Cover cropping
The growing of crops which are used to cover the soil for preventing soil erosion called cover
cropping. The cover crops are dense foliage plants grown to cover surface and used as living mulch.
It reduces raindrop impacts and reduces splash effect and speed of run off. It provides organic matter
and increases infiltration, reducing run off resulting minimizing erosion, e.g. Kudzu, Lentil, Centro,
mungbean, desmodium, dhaincha, stylo, black-gram.
c. Mulching
Practice of spreading grasses, crop residues or other materials (like plastic) over ground between
crops rows/around tree trunk is called mulching. It prevents and reduces raindrop impact, minimize
crusting, improves infiltration rate and reduce runoff loss. It improves soil structure and provides
organic manure and protective cover to soil that minimize soil erosion.

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d. Contour farming
The practice of ploughing, harrowing, furrowing and planting of crops along the contour of the land.
Contour line is sketch against slop in hilly area that minimizes velocity and quantity of surface runoff.
e. Strip cropping
Strip cropping is the growing erosion permitting row crops in alternate strips with erosion checking
close growing crops (leguminous crops) and grasses. It serves as vegetative barriers to erosion and
slows down flow of run-off water, increases the Infiltration rate and ultimately reduces erosion.
f. Terrace cropping
It is growing of crops by constructing horizontal strip of land or broad channel, usually constructed
on or nearby on a contour /across the slope for erosion control is called terrace cropping.
It slows down the velocity and volume of surface runoff and enhance infiltration which minimize soil
erosion.
g. Manuring and fertilizer application,
Balance supply of manures & fertilizer enhance vigorous plant growth and ground cover, strong root
system which improves soil physical conditions such
Infiltration and water holding capacity and finally minimize soil erosion.
2. Soil erosion control in Forest and rangeland
Increase of deforestation, Overgrazing, fire of forest etc causes Soil erosion in forest. The most used
measures to control soil erosion in forest are
a. Afforestation
Afforestation increases the forest plant population that improves soil properties and slows down the
velocity and amount of surface runoff.
b. Controlled grazing
Rational grazing of livestock on range land and forest maintain vegetation on forest that slows the
surface run off and minimize the soil erosion
c. Proper forest management
Introduction of leguminous fodder crops and trees improve the soil structure that minimizes the soil
erosion.
d. Adoption of agro-forest system
Agro-forest practices reduce deforestation and improve soil structure and acts vegetation barrier to
soil erosion.
e. Adoption Bio-engineering system
Bio-engineering system is acts as living barrier to soil erosion and reduce the velocity of surface
runoff and minimize soil erosion.
3. Bio-engineering
It is an integrated technology that uses sound engineering practices in conjunction with ecological
principles to design and construct vegetative living system to prevent erosion, stabilize shallow areas
of soil instability, protect and enhance healthy system. It uses live plant materials and flexible
engineering techniques to eliminate environmental problems.
Construction of engineering structures are expensive, alternative cheap option so in our cases there is
a need of alternative conservation methods which can be adopted with less expenditure, use locally
available materials and environmentally friendly. e.g. To control the surface erosion on fill slope,
napier was grown in Shivapuri Watershed road erosion control program. Many landslides affected
areas like Krishna Bhir are rehabilitated by the uses of bioengineering measures.
Advantages:
 Low cost and lower long term maintenance cost.
 Low maintenance of live plants after establishment.
 Environmental benefit of wildlife habitat.
 Water quality improvement.

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 Compatibility with environmentally sensitive sites.
Application of Bioengineering
 Steep slopes
 Cut and fill slopes along roadways
 Landfill covers
 Stream banks
Methods or Techniques of bio-engineering
a. Brush layering
Brush layer is a layer of plant material intercepted between layers of soil on cut slopes or fill slopes.
b. Hedgerow planting
Establishment of dense vegetation in a linear design for natural resource conservation using woody
plants or perennial grasses.
c. Palisade
Palisade is a wall consisting of living uniform stakes driven into the ground close to each cropland to
prevent wind, water erosion.
d. Grass waterways
grass) to control
soil erosion.
e. Fascine:
A fascine is a rough bundle of brushwood or other material used for strengthening an earthen
structure, or making a path across uneven or wet terrain.
f. Jute netting
This is a net made of jute that is laid and anchored over straw or other mulch to protect the mulch
from wind and water damage
g. Rip rap
Stone pitching is done with vegetation interplanted between stones usually gully floor.
4. Engineering method
It involve the construction of physical structures (dams, walls,terrace etc.) to prevent the soil erosion.
These techniques are employed whenever the greater volume of runoff flow is to be managed.
I. Check dams: It uses to stabilize slope and prevent erosion control
II. Retaining walls: Structures designed to restrain (hold back) soil to unnatural slopes.
III. Water ways: Constructed on natural drainage line which receive and carry the runoff.
V. Embankment: Raised structure (of earth or gravel) used especially to hold back water or to carry
a roadways
VI. Spurs: Structure constructed on the side of the river bank which prevents the out flow of water
from the river and also helps the water to flow in its own pathway.
VII. Spillways: A passage for the disposal of surplus water from the headwater pool or entrance
channel
5. Use different equipment and machineries (Power Tiller and Cultivator )
Use of different equipment and machines that promote the increase in infiltration rate in soil that
results minimize the soil erosion.
a. Power tiller
It is also called as walking tractor powered by 10-15 hp power. It is suited for smaller farmer and
small land. It cuts and pulverizes the soil by the means of number of rotating tines. It is used for well
puddling, weeds control, mixing organic matter and crop residues in soil shallow tillage operation and
pulverized the soil thus preventing soil erosion.

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b. Cultivator
It is the farm implement used for secondary tillage operation. It is used to make pulverized soil either
before planting to aerate the soil and prepare a smooth, loose seed bed or after the crop planted to kill
the weeds and loose the top soils. It prevents surface evaporation, increase infiltration rate of the soil
and thus preventing soil erosion.
Unit: 7 natures of environmental studies
The environment is the sum of the total of the elements, factors and conditions in the surroundings
which may have an impact on the development, action or survival of an organism or group of
organisms, such as, we human beings.
Environment study
Environmental studies are the scientific study of the environmental system and the status of its
inherent or induced changes on organisms. It includes not only the study of physical and biological
characters of the environment but also the social and cultural factors and the impact of man on
environment.
It is the broad field of study that include natural environment, artificial environment and the set of
relationship between them. It involves understanding the change in environment, how human use and
affected in a positive or negative way on environment.
 Principles of Environmental Studies:
 Creating the awareness about environmental problems among people.
 Imparting basic knowledge about the environment and its allied problems
 Developing an attitude of concern for environment
 Motivating public to participate in environment protection and environment improvement
 Acquiring skills to help the concerned individuals in identifying and solving environmental problems.
 Striving to attain harmony with nature.
 Importance of Environmental study
The environment makes us aware about the importance of conservation of nature and aware about
environmental issues and its impact to human beings.
 Environmental issues like global warming, ozone layer depletion, pollution, acid rain etc being global
issues hence it provides solution and maintain ecological balance.
 To clarify modern environmental concept to conserve biodiversity.
 To achieve the sustainable development and understand relationship between environment and
development.
 To use natural resources more efficiently and effectively.
 To know the interrelationship between organisms in populations and communities
 To aware and educate people regarding environmental issues and problems at local, natural and
international levels.

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 Scope of Environment studies
The scope of environmental studies is very wide and deals with many areas like conservation of
natural resources, ecological aspect and impact of human population on environment. The scope of
environment studies can be studied as
a. Environmental science
It deals with the scientific study of environmental system (air,water,soil and land), the inherent or
induced changes on organisms and the environmental damages incurred as a result of human
interaction with environment.
b. Environmental Engineering
It deals with the study of technical processes involved in the protection of environment from the
potentially deleterious effect of human activity and improving the environmental quality for the
health and well beings of humans.
c. Environmental management
It deals with the study of physical, social and economic environment of the enterprise or projects. It
encourages planned investment at the start of the production. It covers the area of objective, scope
and structure of the environment, interaction of nature and pollution management.
 Need of public awareness about environment
It is essential to be familiar with different environmental problems. Environmental protection is
beyond the capacity of one individual, one institution or one government.
In present world, Due to industrialization and increasing population, over exploiting the natural
resource, our environment is being increasingly degraded by human activities, so we need to protect
the environment by active participation. Public participation is equally important with regard to
environmental protection.
It sensitizes the society about environmental issues and challenges interested individuals to develop
skills and expertise thereby providing appropriate solutions.
The public awareness can be increased by environmental education, mass media, internet, organizing
seminar and conference and awareness raising campaign.
 Forest resources: Use and over-exploitation
A forest represents a biotic community with the pre-dominance of woody trees, shrubs and of
vegetation. It is the natural habitat for the wild life. In Nepal forest and shrub land covers about 5.83
million ha (39.41%) of total area.
Uses
 Wood is used as source of energy for the cooking purpose
 Wood is used for making furniture, window and boat etc.
 Forest provide shelter for the various wild life
 It provides fodder and forage for livestock
 It provides major source of medicine, insecticide, gums etc
 It helps in conservation of soil
 It play major role in maintaining ecological balance.
 It is the source of organic matter that maintains soil fertility.

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 Over uses
Increase the population, industrialization, Urbanization leads the deforestation of forest to meet
the present increased demand of timber and forest product and forest land is changed into
agriculture land and human settlement. Over exploitation of forest product leads the
environmental degradation and ecological imbalance that threat to human being existence.
 Deforestation
It is the process of cutting down of the forest tress for human benefit. Due to increase in population of
both human and livestock, the demand for food and natural resource has increased that lead
deforestation. It causes several environmental hazard, imbalance of ecological, desertification and
global warming.
Effect
 Soil erosion become intense and wide spread
 Decrease soil productivity and fertility
 Loss of bio-diversity of wild plants and animals
 Loss of habitat of wild life animals
 Causes desertification
 causes global warming
 Land resource
Land is one of the natural resources in which farming practices carried out. In Nepal, about 65.6%
people are involved in agriculture which totally depend on land resources. In Nepal, the net cultivated
land covers 21% and uncultivated cultivable land covers 7% of total land area. Land provides the
habitat for all the living being. Human carry out the various activities in land by using land resources.
 Land degradation:
It is any change in biological and economical capacity of the land which reduces its productive
potentiality. Land degradation is a process in which the value of the biophysical environment is
affected by a combination of human-induced processes acting upon the land. It includes soil erosion,
soil fertility loss, soil pollution etc.
 Causes of land degradation
a. Deforestation
The increasing population leads to deforestation to meet their present demand of food, clothes and
shelter that results degradation of land.
b. Intensive cultivation
The high intensity of mono-cropping with high use of chemical fertilizer, pesticides and herbicides
results the loss of fertility and productivity of soil.
c. Over grazing
Increasing the livestock to meet the demand of livestock product to increased population leads over
grazing which results loss of vegetation, soil erosion.
d. Industrialization
Development of industries for the economic development of country leads to the deforestation and
degradation of land.
e. Desertification
It is the process by which fertile land becomes desert typically as a result of drought, deforestation,
inappropriate agriculture practices,

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 Management of land degradation
a. Rational grazing
b. Afforestation
c. conservation tillage
d. Crop rotation
e. Judicious use of chemical fertilizer
f. Adopt integrated nutrient management system
g. Promote organic farming
h. Adopt Bio-engineering system
i. adopt soil erosion management practices
 Water resources
Water resources the major source of water that are potentially useful. Water covers 70% of the global
water in the form of ocean, river and lakes. Nepal is water rich country and has second position in
water resource in the world. There are tremendous capacity to efficient utilize the water resource for
different propose for economic development of nation.
Uses
 Use in agriculture production
 Use in industrial production
 Use in hydro –electricity production
 Use in household activities
 Use in recreational activities
Source of water resource
a. Ground water
It refers the water that occurs below the ground surface. About 95% of the ground water uses for
drinking and other propose.
b. Surface water
It refers the water that occurs in surface of earth i.e. river, pond, ocean and stream etc.
 Over exploitation of surface and ground water
Over explosion of population on one side and decrease the water source due to deforestation,
urbanization and industrialization on other sides leads to over exploitation of available surface and
ground water source to meet water demand of increased population for various propose.
Effect
 The increase of extraction of ground water in excess amount leads to decrease ground water level
 Over utilization of ground water leads to drying of well and tap
 Severe scarcity of drinking water in summer
 It leads to introduction of salt water from the sea thus making unsafe for the drinking and agriculture
purpose.
 Increase the cost of construction of well , hand pump and tap.
 Role of an individual in conservation of natural resources.
The individual person would contribute some extent in natural resource conservation by following
ways
a. Planting the plant around the home and agriculture land
b. Participate in the afforestation program
c. Promote the organic farming in own community
d. Increase the awareness in own community about importance of natural resource conservation and
adoption its management practices

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e. Follow the act and policy of government of Nepal on natural resource management
f. Conduct the campaign about management practices of natural resource
g. Judicious use of natural resource efficiently and effectively
h. Make the valuable product from waste product ( plant residue to compost )
i. Adopt effective method of waste disposal
j. Make positive attitude towards natural resource conservation
 Equitable use of resources for sustainable development
Sustainable development is development which meets the needs of the present without compromising
the ability of future generations to meet their own needs. Sustainable development is that
development which meets the needs of the present generation without compromising the ability of
future generations to meet their own needs. It is the judicious utilization of the available limited
resources to meet the needs of present and future generation with least possible degradation on the
environment. The development should be economical viable, socially justice and environmentally
friendly.
The rational, efficient, systematic, effective and equitable use of available both renewable and non-
renewable resource leads to sustainable development.
Unit: 8 Environmental Pollution
Pollution:
It is defined as the undesirable change in the physical, chemical and biological characteristics of the
environment which adversely affects the biotic community (plants, animals and human).
Any undesirable material added in the environment (soil, air and water) due to human activities is
called pollution. Any undesirable physical, chemical and biological material that release in
environment and causes pollution is called pollutants.e.g. CO, CO2, NO2, lead, smoke, dust, plastic,
chemical pesticides, fertilizer and insecticides etc.
Types of pollution:
a. Air pollution
Any undesirable and unwanted material present in air that degrades the quality of air and adversely
effects on biotic community. It is one of the most dangerous and common environmental pollution
caused by industrial revolution and increasing human influence. Air pollutants are SO2, CO, lead,
CO2, Smoke, NO, CFC and NO2 etc.
Sources of Air pollution
The major sources of air pollutant
 Automobile ( cars, motors etc)
 Burning of fuel like wood, coal and petroleum,
 Electric power plant(Thermal power station)
 Industries (Paper making, chemical plants, brick etc)
 Deforestation
 Mining activity

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Effects
 It affects in respiratory system of living organism and causes various disease like asthama, lung
cancer, bronchitis's etc.
 It enhance the global warming that results continue increase of temperature of earth
 The SO2 and CO2 causes the acid rain
 Smoke and dust causes the poor visual of city and effect on vegetation
 Lead causes damages to liver, kidney and gastro-intestine
 It causes irritation of eye, coughing and headache
Control
 Use of alternative source of energy such as solar energy, electric energy etc. in place of fire wood,
coal and oil etc.
 Planation of crop and increased afforestation around home
 Industrial pollution should be controlled employing environmental friendly industrial process
 Chimneys height should be increased
 Standard for automobiles should be implemented (replace or repair the old automobile)
 Public awareness program about the effect of air pollution must be implemented
b. Water pollution
Any undesirable and unwanted substance present in water that alter the quality of water and effects on
biotic community is called water pollution. The major water pollutants are inorganic and organic
effluents, domestic waste and sewage, chemical pesticide, fertilizer and insecticide, nitrates and
phosphates etc.
Source
The major sources of water pollution are
o Industrial source ( inorganic and organic effluents, poisons etc)
o Domestic source( Sewage, detergents etc)
o Agriculture source (pesticides, Insecticides, chemical fertilizers)
Effects
 It is major source of water born disease e.g. Diarrheoa
 It causes the death of aquatic animals
 Disruption of the food chain: Pesticides and chemical fertilizer used in agriculture that mixed into
water bodies and accumulated up to the upper trophic level
 Heavy metal like zinc, arsenic in water causes several health problems like skin cancer
 Increasing water pollution creates more turbid water that reduce light penetration results reduction in
photosynthesis by aquatic plants.
 It causes eutrophication( accumulation of nitrate and phosphate in water bodies )

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Control
 Recycling of water should be used after treatment.
 Cleaning and treatment of waste water before release them into water bodies.
 The use of chemical fertilizer and pesticide should be minimized
 Soil conservation strategies to reduce surface runoff from agricultural field should be adopted.
 Don‘t dispose domestic waste, industrial waste near the water resources.
 Various legistive measure should be employed to control water pollution
c. Land pollution( soil pollution)
Any unwanted material addition to land that reduces its quality and effect on bio-community is called
land pollution. The major land pollutants are inorganic and organic effluents, domestic waste and
sewage, chemical pesticide, fertilizer and insecticide etc.
Source
 Industrial source: inorganic and organic effluents, poison, heavy metals, plastic etc.
 Domestic source: plastic bags, rubber material etc.
 Agriculture source: Chemical fertilizer, pesticides, insecticide, fungicides etc.
 Poor farming practices: Lack of intercropping, crop rotation, excessive use of chemical fertilizer and
pesticides etc.
 Over grazing and deforestation
Effects
 The excessive uses of chemical pesticide kill the both harmful and beneficial micro-organisms
 It causes poor soil physical characteristics like surface compaction; reduce water holding capacity anf
low infiltration of soil.
 It effects on chemical and biological properties of soil like nutrient availability and reduced soil
fertility
 It reduces the crop productivity
 Accumulation of heavy metals in soil causes heavy metal toxicity.
 Over grazing and deforestation causes desertification and low fertility
Control
 The use of chemical pesticides and fertilizer should be minimized.
 Various types of degradable solid wastes should be recycled or converted into compost manure and
non- degradable solid waste should be recycled.
 Agriculture land should not be used as damping places
 Soil erosion should be controlled
 Water logging in the field should be prevented
 Integrated nutrient management approach should be focused.

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d. Noise pollution
The unwanted and unpleasant noisy sound that effect on bio-community is called noise pollution.
Source
 Music from disco
 Automobile and Airplane sound
 Industrial production noise
 people noisy sound
Effects
 It causes loss of hearing capacity.
 It causes irritation to human and causes uncomfortable
 It effects on communication between two person
 Effect on wildlife
Control:
 Vegetation along road and residential area
 Repair and replace automobiles that produce more noise
 Noise producing industries, airport etc must be far from residential area.
 Solid waste Management:
Solid wastes are discarded or useless or unwanted substances generated from the human activities
that effect on bio-community. It is the serious problems due to the increasing population,
industrialization, urbanization and inappropriate agriculture practices.
Causes:
 Refuse from kitchen
 Medical and industrial hazardous waste
 Market wastes
 Street sweeping and other institutional waste
Effects
 It causes environmental pollution (Air, water and Land pollution)
 It causes widespread of disease
 It reduces creational value of resident
 Improper disposal of municipal solid waste can create unsanitary conditions
 It effects on human, animal and plant health
 It also induces the climate change
 Control measures of urban and industrial wastes.
Solid waste management is a systematic process of collecting and treating solid wastes and reduces
its negative impact on living organism including human by either converting valuable product like
compost, manure or reuse and recycling.
a. Separation of solid waste and their respective use
Solid waste should be separate into bio-degradable and non-bio-degradable waste. Bio-degradable
waste should be used to prepare compost and manure and non-degradable waste should be reuse and
recycling.

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b. Develop separate disposal site of urban and industrial waste
c. Industrial waste should be treated before disposal
d. Increase public awareness about proper solid waste disposal
 Role of an individual in prevention of pollution.
Individual play vital role in prevention of pollution
 Reuse, recycle and recreation of non-biodegradable waste
 Make the compost, manure by using biodegradable waste
 Rational use of chemical pesticide and fertilizers
 Don‘t bath and washing clothes near water source.
 Make positive attitude towards pollution control
 Take participate in pollution control campaign
 Planting trees around house and agriculture land
 Follow the rule and acts of pollution control
 Making awareness to the people about impact and measures population.
Water conservation
Water conservation is the process that involves all the policies, strategies and activities
to sustainably manage the natural resource of fresh water to protect the hydrosphere, and to meet the
current and future human water demand.
Water Harvesting
It is the collection and storage of precipitation and run-off resulting from rainfall for industrial,
domestic and farm.
Due to rapid urbanization, population explosion and industrialization, there is increasing pressure on
water resource. The demand for this limited resource is rapidly increasing for agriculture, industrial
and domestic uses cause the scarcity of ground water as well as surface water. There for water
harvesting is necessary to fulfill water demand.
Method of rain fall water harvesting
The water storage may be done in tanks, reservoirs or in the field
 Collection of water for human or livestock use is usually done with ground covers of concrete, tank
etc
 Water for crop production is normally collected in field
a) Water harvesting in small tank:
The 4m x 3mx 2m sized tanks are getting popularity for water harvesting now days. The collected
water can be used for irrigation purpose.
b) Level bench terraces:
Water can be harvested by construction of level bench terraces with slopping run-off contributing
areas above the benches.

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c. Small basin or Micro- catchments
Rain fall water can be harvested by building small basins or micro- catchments to concentrate rain-
fall for individual plot or plants.
Watershed:
It is hydrological boundary area from which the entire surface runoff drains toward the a single point
or outlet.
It can be defined as the land area from which the surface run-off water drains to a single outlet or to
common point. It includes forest, agriculture land, river valley, hills and mountains and village and
community people.
Watershed management
It is the utilization and conservation of land, water and the forest resources at farm household and
community or given watershed level for continuously improved livelihood and overall human
development.
Or
It is the process of formulation and carrying out of course of action involving manipulation of natural,
agricultural and human resources on a watershed to provide resources that are desired by society
without adversely effect on soil and water resources.
Objectives of watershed management
 To protect, conserve and improve the land of watershed for more efficient production
 To improve and increase the production of the timber, fodder and wildlife resource
 To check soil erosion and reduce the effect of sedimentation on the watershed
 To provide standard quality of water around the watershed area
 To reduce occurrence of flood in watershed area
Method of watershed conservation
 Cover cropping
 Mulching
 Conservation tillage
 Strip planting
 Contour farming
 Afforestation
 Rational grazing
 Bio-engineering
 Terrace farming
 Building check dam and other engineering structure in soil erosion areas
 Make the policy of watershed management and implemented effectively.

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Climate change:
Weather: It is a state of environmental condition in short period of time of given small location.
Climate: It is the summation of average weather in a long period of time of given larger area.
Climate change is the any change on climate overtime, whether due to natural variability or as a result
of human activities persisting for an extended period (decades or longer).
Climate change is a statistically significant variation in either the mean state of the climate or in its
variability, which may be due to natural process or external forcing or to persistent anthropogenic
changes in the composition of the atmosphere (IPCC: Intergovernmental Panel on climate Change,
2007) The average temperature of the Earth‘s surface has risen by 0.74 °C.
Causes of climate change
There are mainly two factors that causes of climate change which are
A. Natural causes :
 Volcanoes
 Ocean currents
 Earth tilt‘s
 Intensity of Solar radiation
B. Anthropogenic causes
 Chemical fertilizer
 Emission of GHS
 Deforestation
 Urbanization
 Faulty Agriculture practices.
Global warming is the increase of Earth average surface temperature due to build of greenhouse
gases in atmosphere. It is the evidence of climate change.

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Greenhouse Gases (GHG) are the environmental gases like water vapor,CO,CO2,CH4 CFC, O3 etc
that trap the heat from the sunlight.
The sun sends short wave length of infrared radiation as a heat and light. This energy comes to our
earth during the day time. Some of the sun rays get trapped in the atmosphere by greenhouse gases
(CO2, H2O, O3, CH4, and N2O). And some of them get reflected back into space. The ones get
trapped warm the earth up but if too much heat is trapped, our planet will warm up and climate will
change.
Impacts of climate change on agriculture.
Climate change can effect on agriculture through their direct and indirect effects on agriculture
component like crops, soil, livestock and pests.
The major effects are
a. Decreased crop yield:
 Change in crop physiology.
 Effects on nutrient mineralization in soil
 Decrease fertilizer use efficiency
b. Decreased biodiversity in natural ecosystem,
c. Increase in soil water deficits and causes drought
d. Shifts in Agro ecological zone: Range of current crop will move northward.
e. Change crop-weed competition dynamics
f. Increase the range changes of pest and pathogen
g. Increase biotic stress on crop and livestock
h. Effects on the livestock production and decrease the quality of livestock product

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 AGRICULTURE PRACTICES TO COPE WITH CLIMATE CHANGE
a. Introducing drought tolerant varieties in drought facing areas
b. Following the pattern of crop rotation
c. Zero tillage and mulching
d. Introducing insect, pest and weed resistant varieties
e. Adopt organic agriculture practices
f. Adopt agroforestry practices
g. Adopt climate smart agriculture technique
h. Adopt integrated nutrient management
Acid Rain
Rain with pH value less than 5 is called acid rain which formed when SO2, CO2, CO and NO2
from industry, automobiles and other polluted sources dissolved with atmospheric water and fall
to the soil as acid rain results acidic soil.
It is the process of deposition of acid gases (SO2, CO2, CO etc) from the atmosphere on the land
in the form of rain.
SO2 + ½ O2 +H2O H2SO4 (sulfuric acid)
CO2 + H20 H2CO3 ( Carbonic acid)
Effects
 It effects on biogeochemical cycle
 It causes soil acidity that reduce soil fertility and productivity
 It effects on aquatic and terrestrial flora and fauna
 It causes health hazards to human and animals
 It causes corrugation of building, statues and bridges etc.
Ozone layer depletion
It is the process of destruction of ozone in the stratosphere by different pollutants making the
ozone layer thinner. It is the serious global issues of the earth. Ozone layer forms a very
protective covering around the earth's atmosphere that prevents the UV rays reaching into our
atmosphere, thus saving us from the extremely damaging effect of UV rays.
Causes
Different harmful pollutants like CFCs, SO2, CO2, CO produce from industries,
automobiles, domestic waste and combustion of fossil fuel.
Effects:
a. Effect on human
If ozone layer is depleted, harmful UV radiation may causes skin cancer, eye problem and
damage of immune system.
b. Reduce crop productivity:
UV radiation reduces the photosynthesis and causes necrosis and leaf drop which ultimately
decrease the productivity of the crop
c. Effect on aquatic life
UV radiation decreases number of phytoplankton and zooplanktons thus harm fish and other
aquatic life
d. Environment change
Due to UV rays entering the earth atmosphere causes the increase in temperature and other
climate change.

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NOTE:
Factors influencing soil Formation
V.V .Dokochaev states that soil formation is the function of five different factors that are represented
in equation as
S= f{ Cl,O,R,O,P,T}
Where,
Cl= climate
O= Organism
R=Relief/ topography
P= Parent material
T= Time period
These are the five major factors that controls the formation of soil
a. Climate
It is one of the most important factors that can shape the formation of soil. Primarily, effective
precipitation and temperature play a major role. Precipitation determines the chemical and biological
reactions. Surplus water percolating through the soil, transport soluble and suspended materials from
the upper to lower layers, thus stimulating weathering reactions as well as more vegetation.
Temperature plays vital role in weathering of rock and mineral.
b. Organism
Various micro-organisms stimulate organic matter decomposition, biochemical weathering, and
nutrient cycling in the soil. It affects chemical exchanges between roots and soil.
c. Relief/ Topography
It determines the rate of precipitation or run off and rate of formation or erosion of surface soil. e.g.
The southern faced hills receive maximum sunlight and rainfall that is required for soil formation
whereas northern faced hills receive high wind that enough for soil formation.
d. Parent material
It refers the rock, mineral or organic matter from which soil is formed. Soil will carry the
characteristics of its parent material such as color, texture, structure and mineral composition etc.
e. Time period
Soil formation takes many years to form soil from their parent materials. Different factors govern the
rate of formation and time period taking for formation.

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QUESTION BANK
1. REGULAR/BACK EXAM — 2074
Attempt Questions
1. Define soil. Explain soil as a natural dynamic body.
2 Write any three physical and three chemical properties.
3. Define compost. Write down the method of compost preparation
by pit method.
4. Write down the functions and deficiency symptoms of nitrogen
and phosphorous in plant.
5. Define soil erosion. Write down the measures of soil erosion.
6. Define environmental pollution. Write the causes and effect of
air pollution.
7. What is soil acidity? Write the causes of soil acidity and it
control measures.
8. In Urea or ammonium sulphate. Which one causes more soil
acidity? What different reactions occur on soil when phosphoric
fertilizers are applied? Describe it.
9. Differentiate between. (Any Three)
a. Chemical fertilizer and organic fertilizer
b. Contour farming and alley cropping
c. Bulk density and piratical density
d. Soil productivity and soil fertilizer
10. Write short notes on: (Any Five)
a. Physical weathering of rock
b. Soil pH
c. Organic farming
d. Acid rain
e. Bio-engineering
f. Soil texture

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2. Regular 2073
Attempt all question
1. Define soil. Explain soil -plant relationship.
2. Define organic matter. Explain physical properties of soil.
3. Enlist all essential plant nutrition. Describe different methods of
soil fertility evaluation.
4. Enlist nitrogenous fertilizers. Describe soil fertility problems and
their management methods in Nepal.
5. Define soil erosion. Describe different types of soil erosion by
water.
6. What is soil alkalinity? Write the cause and control measures of
soil alkalinity.
7. Describe the causes, effects and control measures of air
pollution.
8. Describe the concept and components of integrated nutrient
management.
9. Differentiate between (Any Three)
a. Soil productivity and soil fertility
b. Chemical fertilizer and organic fertilizer
c. Bulk density and partial density
d. Acidic soil and alkaline soil
10. Write short note on: (Any Five)
a. Soil color
b. Green manure
c. Global warming
d. Chemical weathering
e. Bio- engineering

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3. Exercise paper
Attempt all question
1. Explain the concept of soil. Write the physical and chemical
properties of soil.
2. Define rock and mention its classification.
3. What is soil erosion? Mention the types of soil erosion briefly.
4. What is the cause of soil erosion and also explain the
consequence of soil erosion.
5. Define the soil conservation. Explain the methods of soil
conservation.
6. What is contour cropping or farming? Write the benefits of it.
7. What are essential plant nutrients. Describe briefly about it
primary and secondary elements.
8. Define organic manure and classify the organic manure.
9. Define green manure. Write the advantages and disadvantages of
green manure.
10. Define fertilizer. Explain brief about nitrogenous fertilizer.
11. Explain the brief about urea and phosphatic fertilizer.
12. Differentiate between manure and fertilizer
13. Write short notes on:
a. Farm Yard Manure
b. Potassium
c. Green manure
d. Primary nutrients
e. Cover crop

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CHAPTER WISE POSSIBLE QUESTION:
Unit: 1. Introduction of soil
1. Define soil. Briefly explain the soil is dynamic body.
2. Justify the Soil is natural dynamic body with suitable examples.
3. Define soil horizon. Describe the use and importance of soil in agriculture.
4. Define soil profile. Explain the factors influencing the soil forming process.
5. Define Pedological approach. Describe soil and plant relationship.
6. Define Edaphological approach. Justify the soil is medium for plant growth.
Unit: 2. Rock and Minerals
1. Define rocks and explain its types briefly.
2. Differentiate between rock and mineral. Explain the igneous rock with suitable example.
3. Define weathering. Enlist the weathering process and describe briefly about chemical
weathering.
4. Define chemical weathering and describe its process in detail.
5. Classification of weathering process. Explain physical weathering process.
6. Explain how plants play important role in weathering process.
7. Differentiate between physical and chemical weathering process.
Unit: 3. Soil properties
1. Define soil texture. Explain the importance of soil texture in agriculture.
2. Define soil separate. Explain textural classification of soil briefly.
3. Define soil structure. Explain its importance in agriculture production.
4. Differentiate between soil structure and soil texture.
5. Define bulk density. Explain the classification of the soil texture.
6. Differentiate between particle and bulk density.
7. Derive the relationship between particle density, bulk density and porosity.
8. Define porosity. Explain the factors affecting the bulk density.
9. Define soil color. Explain factors affecting of the soil color.
10. Enlist the importance physical properties of the soil. Explain the importance of bulk
density and soil color in agriculture production.
11. Define soil acidity. Explain its causes and management practices.
12. Define liming. Describe how limes reclaim the soil acidity.
13. Define soil Ph. Differentiate between soil acidity and soil alkalinity.
14. Enlist liming material. Explain the pools/ types of soil acidity.
15. Define black alkali soils. Explain the causes and management of soil alkalinity.
16. Write the importance of liming in agriculture production.
17. Define soil alkalinity. Classify the soil alkalinity.
18. Differentiate between sodic soils and saline soils.
19. Write the effects of sodic, saline and saline sodic soils in agriculture.

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20. Enlist importance chemical properties of soil. Explain how gypsum application reclaims
the soil alkalinity.
21. Enlist the biological characters of soil. Explain soil micro-organism with their
importance.
22. Define organic matter. Write its importance in agriculture.
23. Define organic manure and classify it.
24. Define compost. Explain heap method of compost preparation.
25. Give reason of advantage of heap method over pit method of composting. Explain
procedure of pit method of compost preparation.
26. Define bio- fertilizer and explain its importance over chemical fertilizers.
27. Classify the bio-fertilizer. Explain the importance of green manuring in agriculture.
28. Enlist nitrogen fixation bio-fertilizer and Explain importance of bio-gas in Nepal.
Unit: 4. Plant nutrition
1. Define plant nutrition. Describe Arnon's criteria of essential plant nutrient.
2. Enlist the all essential plant nutrient with their available form to plant.
3. Differentiate between macro and micro nutrients.
4. Define essential plant nutrient and classify it.
5. Write the function and deficiency Nitrogen and Zinc.
6. Enlist micro nutrient. Explain function and deficiency of Mo and Mn.
7. Enlist of beneficial micro nutrient. Differentiate between symptom N and K.
8. Define mobile element and Explain function and deficiency of Ca and B.
9. Define soil fertility evaluation. Explain its method briefly.
10. Enlist the method of soil fertility evaluation. Describe about plant analysis.
11. Define hidden hunger. Explain merit and demerit of Visual symptom analysis.
12. Describe biological test analysis and write the importance of soil fertility evaluation in
agriculture.
Unit: 5. Fertilizers
1. Define Fertilizer. Explain the behavior of urea in a soil.
2. Enlist the nitrogenous fertilizers. Explain the fate of nitrogenous fertilizers in a soil and
plant.
3. Define phosphorous fertilizers and explain the behavior of phosphoric fertilizers in soil.
4. Explain the nitrogenous fertilizers with suitable example.
5. Classify the phosphoric fertilizer and potassium fertilizer.
6. Define the INM and write its component and importance.
7. Conceptualize the INM with their objectives and components.
8. Write the major soil fertility problems of Nepal and their management.

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Unit: 6. Soil conservation
1. Define soil erosion. Write its types briefly.
2. What is water erosion and describe the types of water erosion
3. What is soil conservation and write the consequence of soil erosion.
4. Write the soil erosion control method in agriculture land.
5. Define bio-engineering .Why it is suitable for Nepal?
6. How you conserve soil erosion by agriculture practices?
Unit: 7. Nature of environmental studies
1. Define environment studies. Write its importance and scope briefly.
2. Write role of an individual in conservation of natural resources.
3. What is land resources and write consequences of it's over utilization.
4. Write water resource and its sustainable management practices.
Unit: 8. Environmental Pollution
1. Define environmental pollution and causes of it.
2. Define air pollution and its causes, consequence and control method.
3. Define water pollution and describe its causes, consequence and control method.
4. Define land pollution and its causes and management practices.
5. Justify modern agriculture is a source of land pollutant.
6. Define water harvesting and write of rainfall water harvesting method.
7. Define solid waste and write its Causes, effects and control measures of urban and
industrial wastes.
8. Write role of an individual in prevention of pollution.
9. Define watershed and its objectives and importance.
10. Define watershed management and method of sustainable watershed management.
11. Define climate change and write its cause and its effect in agriculture.
12. Differentiate climate change and global warming and write management strategy for
climate change.
13. Define acid rain and its causes and effect and management practices.
14. Define ozone layer depletion and its causes and effects on bio-community.

Tirtha soil final

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