Soil sciences
- 1. Soil Sciences Prepared by Gamar Suleymanova.
- 2. There will be presented: • Formation and evolution of soil. • Characteristics and classification of soils. • Regularity and environmental features of soil distribution on Earth. • Location of the soil in the biosphere. • Morphological signs of soil profile. • Structure of soil profile. • Granulometric composition. • Soil composition: properties and modes. • General physical properties of soil.
- 3. • Soil is the thin layer of material covering the earth’s surface and is formed from the weathering of rocks. It is made up mainly of mineral particles, organic materials, air, water and living organisms—all of which interact slowly yet constantly.
- 5. The soil profile • As soils develop over time, layers (or horizons) form a soil profile. • Most soil profiles cover the earth as 2 main layers—topsoil and subsoil. A horizon—humus-rich topsoil where nutrient, organic matter and biological activity are highest (i.e. most plant roots, earthworms, insects and micro-organisms are active). The A horizon is usually darker than other horizons because of the organic materials. B horizon—clay-rich subsoil. This horizon is often less fertile than the topsoil but holds more moisture. It generally has a lighter color and less biological activity than the A horizon. Texture may be heavier than the A horizon too. C horizon—underlying weathered rock (from which the A and B horizons form).
- 6. Factors affecting soil formation
- 8. Soil forms continuously, but slowly, from the gradual breakdown of rocks through weathering. Weathering can be a physical, chemical or biological process:
- 9. Physical Weathering Breakdown of rocks from the result of a mechanical action. Temperature changes, abrasion (when rocks collide with each other) or frost can all cause rocks to break down.
- 10. Chemical weathering Breakdown of rocks through a change in their chemical makeup. This can happen when the minerals within rocks react with water, air or other chemicals.
- 11. The breakdown of rocks by living things. Burrowing animals help water and air get into rock, and plant roots can grow into cracks in the rock, making it split.
- 16. ORGANISMS Soil formation is influenced by organisms (such as plants), micro-organisms (such as bacteria or fungi), burrowing insects, animals and humans. As soil forms, plants begin to grow in it. The plants mature, die and new ones take their place. Their leaves and roots are added to the soil. Animals eat plants and their wastes and eventually their bodies are added to the soil. This begins to change the soil. Bacteria, fungi, worms and other burrowers break down plant litter and animal wastes and remains, to eventually become organic matter. This may take the form of peat, humus or charcoal.
- 17. Climate Temperature affects the rate of weathering and organic decomposition. With a colder and drier climate, these processes can be slow but, with heat and moisture, they are relatively rapid. Rainfall dissolves some of the soil materials and holds others in suspension. The water carries or leaches these materials down through the soil. Over time this process can change the soil, making it less fertile.
- 20. Time • Soil properties may vary depending on how long the soil has been weathered. • Minerals from rocks are further weathered to form materials such as clays and oxides of iron and aluminum. • Queensland (and Australia) is a very old weathered landscape with many ancient soils. Soil sodicity in Queensland
- 21. Location of the soil in the biosphere Although soil has many uses, it is really just a layer of dirt between the atmosphere and the bedrock in the tectonic plates. The top layer of the planet is called the lithosphere. Soil is the loose stuff on the surface of the lithosphere. We have talked about plate tectonics and swirling clouds in the atmosphere. In the same way those conditions change, the soil changes. It changes very slowly but very definitely. It's a very complex system that supports all of the life on land.
- 22. Morphological signs of soil profile Soil morphology is the field observable attributes of the soil within the various soil horizons and the description of the kind and arrangement of the horizons.
- 23. Structure of soil profile
- 24. Granulometric composition Soil sample view Dry soil condition Wet soil condition morphology of the wet sample when rolling the cord Sand sand grains loose, i.e. particles e are bound fluid mass ("quicksand") does not roll Sandpit sand particles prevail, few lumps lumps break up easily when squeezed unplastic mass easily rolls into a ball, but the cord does not form. he soil breaks up and individual small fragments. Stoop lumps of various sizes prevail effort is required to break lumps in the hand weak to good ductility with a decrease in the proportion of sand particles, the plasticity of the soil increases. light loam - when rolling, a cord is formed that easily breaks into segments: Loam medium loam - when rolling, a continuous cord is formed, which when folded into a ring breaks up heavy loam - when rolling, a cord is easily formed, which coils into a ring, but gives cracks Clay homogeneous mass without sand particles very strong solid lumps, not destroyed by the effort of the hand very elastic, sticky, spreading mass the cord formed during rolling easily coils into a ring, does not crack
- 25. Soil Composition • Every type of soil has unique properties. Using these unique properties, forensic investigators are able to analyze soil embedded in a criminal's sneakers or footprints and determine where it came from and thus, where the criminal was. • There are three primary types of soils: sand, silt and clay. Other types of soil come from the mixture of these primary types and have characteristics intermediate of these natural types.
- 27. • Type of Soil: Sand • Water Absorption: Absorbs water easily but does not retain it for long periods of time. Not ideal for planting or growing any vegetation. • Texture: Dry and gritty to the touch. • Particle Size: Made up of relatively small particles. • Where are they found? Sand can be found on a variety of relief forms from beaches to deserts, but also mountains, quarries, dunes along sea shores, sometimes also the side of the road.
- 28. • Type of Soil: Silt • Water Absorption: Retains water longer than sand, but it can't hold on to as much nutrients. Out of all types of soil, silt is considered to be among the most fertile of soils. • Texture: Soft and smooth when dry. Soapy slick when moistened. • Particle Size: Made up of fine particles, with individual pieces close together. • Where are they found? Silt is often found in river estuaries, because the fine particles are washed downstream and deposited when the water flows more slowly.
- 29. • Type of Soil: Clay • Water Absorption: When clay particles come together they form a heavy mass that makes it difficult for air, water and plant roots to move through the soil when wet. • Texture: Sticky to touch when wet, but smooth when dry. • Particle Size: Made of extremely fine particles. • Where are they found? Clay is often used for pottery. People are likely to encounter clay in its rock-hard state in archaeological sites where people in the past have deposited clay bowls and other appliances. In nature, you can find clay in lakes, ponds or at the seashore.
- 30. • Type of Soil: Loam • Water Absorption: Holds plenty of moisture but also drains well so that sufficient air can reach the roots. • Texture: Soft, dry, and crumbly in your hands. • Particle Size: A mixture of clay, silt and sand. • Where are they found? This type of soil is often used to garden and grow crops.
- 31. • Type of Soil: Gravel • Water Absorption: Unable to retain moisture. • Texture: Hard and rough texture. • Particle Size: Wide range of size for particles. • Where are they found? Many roadways are surfaced with gravel, especially in rural areas where there is little traffic.
- 32. General Observation Sandy Loamy Clay
- 34. • Soil “horizons” are discrete layers that make up a soil profile. They are typically parallel with the ground surface. In some soils, they show evidence of the actions of the soil forming processes.
- 35. • Sand-Large Particles • Silt-Medium Particles • Clay-Small Particles
- 36. • Soil color is influenced primarily by soil mineralogy – telling us what is in a specific soil. Soils high in iron are deep orange-brown to yellowish-brown. Those soils that are high in organic matter are dark brown or black. Color can also tell us how a soil “behaves” – a soil that drains well is brightly colored and one that is often wet and soggy will have a mottled pattern of grays, reds, and yellows.
- 37. Soil Structure Type Description Granular Rounded surfaces Crumb Rounded surfaces but larger than granular Subangular blocky Cube-like with flattened surfaces and rounded corners Blocky Cube-like with flattened surfaces and sharp corners Prismatic Rectangular with a long vertical dimension and flattened top Columnar Rectangular with a long vertical dimension and rounded top Platy Rectangular with a long horizontal dimension Single grain No aggregation of course particles when dry Structureless No aggregation of fine particles when dry Aggregates are described by their shape, size and stability. Aggregate types are used most frequently when discussing structure
- 38. Particle Density • A soil particle has no pore space, and is nothing more than a very small piece of rock. • The weight of an individual soil particle per unit volume is called particle density. • Unit: grams per cubic centimeter (g/cm3). • An average value for particle density is 2.66 g/cm3. • In comparison, water has a density of 1 g/cm3, and organic matter has a density of 0.8 g/cm3.
- 39. Bulk Density • Bulk density is defined as the dry weight of soil per unit volume of soil. Bulk density considers both the solids and the pore space; whereas, particle density considers only the mineral solids.
- 40. Porosity • Porosity or pore space refers to the volume of soil voids that can be filled by water and/or air. It is inversely related to bulk density. Porosity is calculated as a percentage of the soil volume: Bulk density x 100 = % solid space 100% – % Solid Space = Percent Pore Space