PAU DWELLS UPON USE OF POOR QUALITY IRRIGATION WATER

LUDHIANA, JULY 21:-----



In about 40% of the total area of Punjab, the underground tubewell waters contain high concentration of salts and their sustained use adversely affects soil health and agricultural production, said the experts of Punjab Agricultural University (PAU). They divulged that these waters are saline (containing chlorides and sulphates of sodium) or sodic (containing carbonates and bicarbonates of sodium). Providing useful guidelines to the farmers for the judicious use of poor quality irrigation water, the scientists emphasised on getting the underground tubewell waters tested from soil and water testing laboratory (SWTL) and told that irrigation with waters having very high concentration of salts is not recommended.



The farm experts said that in areas receiving poor quality irrigation waters, leaching of excess soluble salts and water from the root zone depth of the soil has to be ensured so as to maintain a favorable salt and water balance. Stressing that provision of proper drainage is, therefore, a pre-requisite when poor quality waters are to be use for irrigation, the scientists informed the farmers that surface drains are cheaper than the sub-surface drains. For uniform distribution of irrigation water in the field, the land should be properly leveled as it ensures uniform leaching of soluble salts and waters from the soil. Farmers were also advised to use the poor quality waters on light textured soils.



Impressing upon the farmers to make proper crop selection, the PAU experts said that it is always preferable to grow crops and varieties, capable of producing high yields when irrigated with saline or sodic waters. Only salt tolerant and semi-tolerant crops like barley, wheat, mustard, spinach, turnip, raya, millets, etc., should be grown. Telling the farmers that cotton can be grown if proper germination is ensured by pre-sowing irrigation with good quality water, the experts advised the that the crops having high water requirements such as rice, sugarcane and berseem should preferably not be grown, particularly when drainage is poor. Water in village ponds contains essential plant nutrients like nitrogen, potassium and phosphorus. However, it may also contain salts such as carbonates, bicarbonates and chlorides of calcium, told they, saying that this water should be got tested from SWTL and may be used for irrigation as per recommendation.



The experts told the farmers that the adverse effects of high soil sodium saturation can be offset by gypsum application. Application of gypsum is recommended when RSC of irrigation water exceeds 2.5 me/I. For each me/I of RSC, the quantity of gypsum (70% purity) works out to be 1.50 q/acre for four irrigations of 7.5 cm each, added they. Gypsum should be applied on cumulative basis (calculated on the basis of number of irrigations) in one dose after the harvest of previous crop, said the experts and told that if soil has already deteriorated, gypsum should be applied on soil test basis. After mixing gypsum in the surface (0-10 cm) soil, heavy irrigation should be given to leach down soluble salts before sowing of the next crop. The PAU scientists elaborated that the alternate furrow irrigation with poor quality tube well water also results in saving of irrigation water and checks deterioration of soil health. Pointing to the use of organic amendments, they suggested the farmers, "In calcareous soils with more than 2% calcium carbonate, use organic manures viz. farmyard manure @ 8 tones/acre or green manure or wheat straw @ 2.5 tons/acre/year for reducing harmful effects of sodic irrigation water."



The farming community was also asked to use poor and good quality waters together, either alternatively or by mixing with each other. It is also advisable to use good quality waters in early stages of crop growth and poor quality waters during later stages when the crop can tolerate higher salinity/sodicity levels, said the PAU experts.
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