assignment on Quality of irrigation water
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The document discusses the principles and practices of irrigation water management, focusing on the quality of irrigation water and the management of saline water. It highlights the importance of assessing water quality based on salinity, sodium levels, and the presence of harmful ions, along with strategies to improve crop yields despite saline irrigation water. Various management practices such as gypsum application, crop selection, and irrigation methods are recommended to mitigate the adverse effects of poor quality water on crops.
assignment on Quality of irrigation water
- 1. Assignment On QUALITY OF IRRIGATION WATER AND MANAGEMENT OF SALINE WATER FOR IRRIGATION SUB.- PRINCIPLES AND PRACTICES OF WATER MANAGEMENT MANAGEMENT Submitted To – Ms. NISHA SAPRE Assistant Professor Department of Agronomy J.N. Krishi Vishwa Vidyalaya, CollegeofAgriculture,Jabalpur Submitted By – GOVARDHAN LODHA Enroll. No. (160111017) Department of Agronomy M.Sc. (Ag) Agronomy 2nd semester M.Sc. (Ag.) Previous 2nd semester
- 2. QUALITY OF IRRIGATION WATER AND MANAGEMENT OF SALINE WATER FOR IRRIGATION INTRODUCTION The suitability of irrigation water is mainly depends on the amounts and type of salts present in water. The main soluble constituents are calcium, magnesium, sodium as cations and chloride, sulphate, biocarbonate as anions. The other ions are present in minute quantities are boron, selenium, molybdenum and fluorine which are harmful to animals fed on plants grown with excess concentration of these ions All irrigation waters are not pure and may contain some soluble salts. In arid and semi-arid regions successful crop production without supplemental irrigation is not possible. Irrigation water is usually drawn from surface or ground water sources, which typically contain salts in the range of 200 to 2000 ppm (= 200 to 2000 g/m3 ). Irrigation water contains 10 – 100 times more salt than rain water. Thus, each irrigation event adds salts to the soil. Crop removes water from the soil to meet its water needs (ETc) leaving behind most of the salts to concentrate in the shrinking volume of soil water (Fig. 26.1). This is a continuous process. Application of saline water may hinder the crop growth directly and may also cause soil degradation. Beyond its effect on crop and soil, irrigation water of low quality can also affect environment by introducing potentially harmful substances in to surface and ground water sources. Therefore, a salt balance in the soil has to be maintained through proper water management practices for continuous and successful cultivation of crops.
- 3. Salinity buildup process in irrigated soils CRITERIA TO DETERMINE THE QUALITY OF IRRIGATION WATER The criteria for judging the quality of irrigation water are: Total salt concentration as measured by electrical conductivity, relative proportion of sodium to other cations as expressed by sodium adsorption ratio, bicarbonate content, boron concentration and soluble sodium percentage. Total soluble salts Salinity of water refers to concentration of total soluble salts in it. It is the most important single criterion of irrigation water quality. The harmful effects increase with increase in total salt concentration. The concentration of soluble salts in water is indirectly measured by its electrical conductivity (ECw). The quality of saline waters has been divided into five classes as per USDA classification given in Table. Salinity classes of irrigation water Salinity class Electrical conductivity Micro mhos/cm Milli mhos/cm C1 – Low < 250 < 0.25 C2 – Medium 25– 750 0.25 – 0.75 C3 – Medium to high 750– 2250 0.75 – 2.25 C4 – High 2250 – 5000 2.25 – 5.00 C5 – Very high > 5000 > 5.00 Adverse effects of saline water include salt accumulation, increase in osmotic potential, decreased water availability to plants, poor germination, patchy crop stand, stunted growth with smaller, thicker and dark green leaves, leaf necrosis & leaf drop, root death, wilting of plants, nutrient deficiency symptoms and poor crop yields. Sodium Adsorption Ratio (SAR) SAR of water indicates the relative proportion of sodium to other cations. It indicates sodium or alkali hazard.
- 4. The ion concentration is expressed as meq per litre. Increase in SAR of water increases the exchangeable sodium percentage (ESP) of soil. There is a linear relationship between SAR and ESP of the soil: Sodicity classes of water Sodium class SAR value S1 – Low < 10 S2 – Moderate 10 – 18 S3 – High 18 – 26 S4 – Very high > 26 Harmful effects of sodic water include destruction of soil structure, crust formation, poor seedling emergence, reduction in availability of N, Zn and Fe due to increased soil pH, Na toxicity and toxicity of B & Mo due to their excessive solubility. Residual sodium carbonate Bicarbonate is important primarly in its relation to Ca and Mg. There is a tendency for Ca to react with bicarbonates and precipitate as calcium carbonate. As Ca and Mg are lost from water, the proportion of sodium is increased leading to sodium hazard. This hazard is evaluated in terms of Residual Sodium Carbonate (RSC) as given below : RSC is expressed in meq per litre. Water with RSC more than 2.5 meq/L is not suitable for irrigation. Water with 1.25 to 2.5 meq/L is marginally suitable and water with less than 1.25 meq/L is safe for use. Boron content
- 5. Though boron is an essential micronutrient for plant growth, its presence in excess in irrigation water affects metabolic activities of the plant. For normal crop growth the safe limits of boron content are given in Table Table . Permissible limts of boron content in irrigation for crops Boron (ppm) Quality rating < 3 Normal 3 – 4 Low 4 – 5 Medium 5 – 10 High More than 10 Very high Leaching requirement Leaching requirement (LR) is that fraction of total crop water requirement which must be leached down below the crop root zone depth to control salts within the tolerance level (ECe) of the crop. Where: ECw = Salinity of applied water in dS/m ECe = Threshold level soil salinity of the crop in dS/m MANAGEMENT PRACTICES FOR USING POOR QUALITY WATER Whenever, it is inevitable to use water of poor quality water for crop production appropriate management practices helps to obtain reasonable yield of crops. Some of the important management practices are as follows:
- 6. a) Application of gypsum: Chemical amendments such as gypsum, when added to water will increase the calcium concentration in the water, thus reducing the sodium to calcium ratio and the SAR, thus improving the infiltration rate. Gypsum requirement is calculated based on relative concentration of Na, Mg & Ca ions in irrigation water and the solubility of gypsum. To add 1 meq/L of calcium, 860 kg of gypsum of 100% purity per ha m of water is necessary. b) Alternate irrigation strategy: Some crops are susceptible to salinity at germination & establishment stage, but tolerant at later stage. If susceptible stages are ensured with good quality water, subsequent tolerant stages can be irrigated with poor quality saline water. c) Fertilizer application: Fertilizers, manures, and soil amendments include many soluble salts in high concentrations. If placed too close to the germinating seedling or to the growing plant, the fertilizer may cause or aggravate a salinity or toxicity problem. Care, therefore, should be taken in placement as well as timing of fertilization. Application of fertilizers in small doses and frequently improve uptake and reduce damage to the crop plants. In addition, the lower the salt index of fertilizer, the less danger there is of salt burn and damage to seedlings or young plants. d) Methods of irrigation: The method of irrigation directly affects both the efficiency of water use and the way salts accumulate. Poor quality irrigation water is not suitable for use in sprinkler method of irrigation. Crops sprinkled with waters having excess quantities of specific ions such as Na and Cl cause leaf burn. High frequency irrigation in small amounts as in drip irrigation improves water availability and uptake due to microleaching effect in the wetted zone. e) Crop tolerance: The crops differ in their tolerance to poor quality waters. Growing tolerant crops when poor quality water is used for irrigation helps to obtain reasonable crops yields. Relative salt tolerance of crops is given in Table Method of sowing: Salinity reduces or slows germination and it is often difficult to obtain a satisfactory stand. Suitable planting practices, bed shapes, and irrigation management can greatly enhance salt control during the critical germination period. Seeds have to be placed in the area where salt concentration is less. Salt accumulation is less on the slope of the ridge and bottom of the ridge. Therefore, placing the seed on the slope of the ridge, several cm below the crown, is recommended for successful crop establishment g) Drainage:
- 7. Provide adequate internal drainage. Meet the nece ssary leaching requirement depending on crop and EC of water. This is necessary to av oid build of salt in the soil solution to leve ls that will limit crop yields. Leaching requ irement can be calculated from water test results and tolerance levels of specific crops. . Relative salt tolerance of crops Field crops: Cotton, Safflower, Sugarbeet & Barley Tolerant Fruit crops: Date palm & Guava Vegeta bles: Turnip & Spinach Forage crops: Berseem & Rhodes grass Field crops: Sorghum, Maize, Sunflower, Bajra, M ustard, Rice & Wheat Semi tolerant Fruit crops: Fig, Grape & Mango Vegeta bles: Tomato, Cabbage, Cauliflower, Cucu mber, Carrot & Potato Forage crops: Senji & Oats Field crops: Chick pea, Linseed, Beans, Greengram & Blackgram Sensitive Fruit c rops: Apple, Orange, Almond, Peach, Strawberry, Lemon & Plum Vegeta bles: Radish, Peas & Lady’s finger Salinity control with sloping beds h) Other management practices
- 8. ♦ Over aged seedlings in rice: Transplanting of rice with over age d seedlings at a closer spacing results in better establishment in salt effected soils than normal aged seedlings. In case of other crops like finger millet, pearl millet etc., transplanting is better method than direct sowing of these crops for proper establishment. ♦ Mulching: Mulching wit h locally available plant material help i n reducing salt problems by reducing evaporation and by increasing infiltration. ♦ Soil management: All so il management practices that improve infiltration rate and maintain favourable soil structure reduces salinity hazard. Crop rotation: Inclusion of crops such as rice in the rotation reduces salinity References : Books;- Panda SC. 2003. Principles and Practices of Water Management. Agrobios. Michael AM. 1978. Irrigation Theory and Practice. Vikas Publ. Paliwal KV. 1972. Irrigation with Saline Water. IARI Monograph, New Delhi. Lenka D. 1999. Irrigation and Drainage. Kalyani Web pages:- http://site.iugaza.edu.ps/halnajar/files/2010/03/L8-Irrigation- Water-Quality.pdf http://www.agriinfo.in/?page=topic&superid=1&topicid=30 http://www.fao.org/docrep/x5871e/x5871e07.htm http://agritech.tnau.ac.in/agriculture/agri_irrigationmgt_suitabilit yofwater.html Articles /research papers;- http://www.ajer.org/papers/v2(3)/I0235968.pdf https://www.researchgate.net/publication/266506192_Irrigation_ water_quality_and_its_effects_upon_soil Article Irrigation WaterQuality for Leafy Crops:APerspective of Risks and PotentialSolutions Ana Allende 1 and James Monaghan 2,*
- 9. Ms. Nisha Sapre Govardhan Lodha Course Instructor Student