1. Lecture 34 Leaching requirements - irrigation and drainage water quality recycling of drainage water for irrigation

2. Extensive areas of land in the arid and semi arid regions of India have gone out of cultivation due to the rise of water table and accumulation of salt. Excessive irrigation and poor water management are the chief causes of water logging and salt build-up. An accumulation of salts in soils leads to unfavorable soil-water- air relationships and decreases crop production. Gradually, the land goes out of cultivation, unless remedial measures are under taken.

3. LEACHING Leaching is the process of removal of soluble material by the passage of water through soil. LEACHING REQUIREMENT It is the minimum amount of irrigation water that must be drained through the crop root zone to control the soil salinity at the given specific level.

4. LEACHING METHODS By ponding an appreciable depth of water on the soil surface by means of dikes or ridges Rectangular checks and level borders are used when the land is flat. Contour checks can be used when the land slope is considerable. The effectiveness of leaching by furrows is limited. Sprinkling is an effective method for leaching, especially when soils are cracked or are highly permeable. Intermittent ponding is superior to continuous ponding for effective leaching.

5. The efficiency of leaching depends on 1.The amount of water applied, 2.Uniformity of water distribution, and 3.The adequacy of drainage

8. For surface irrigation method including sprinkler Where, ECw = Electrical conductivity of the irrigation water, dS/m ECe = Electrical conductivity of the soil saturation extract for a given crop proportional to the tolerable degree of yield loss

9. For drip irrigation method Where, ECw = Electrical conductivity of the irrigation water, dS/m Max.ECe =Maximum tolerable Electrical conductivity of the soil saturation extract for a given crop

10. Salinity management techniques 1.Frequent irrigation 2.Crop selection 3.Preplanting irrigation 4.Higher Seed rate 5.Blending with good quality irrigation water 6.Irrigation rotation with good and poor water 7.Land grading 8.Deep ploughing and subsoiling 9.Drainage 10.Rain water management

11. Drainage water use 1.Used for irrigation by mixing with canal water 2.Dispose off the water by gravity/ by lift irrigation 3.Evaporation tanks 4.Bio-drainage 5.Brackish water fish culture

12. HE WHO PROVIDES WATER DESERVES TWO NOBEL PRIZES ONE FOR PEACE AND THE OTHER FOR SCIENCE - John F. Kennedy -

13. LET US WORK TOGETHER TO MANAGE AVAILABLE WATER

14. Water is precious… conserve it…