ADVERSE EFFECTS OF SALINE TUBE WELLS WATER IRRIGATION ON SOIL AND CROP IN LACHI VALLEY OF DISTRICT KOHAT IN NWFP

Abstract

Salinity has plagued crop production in irrigated regions of the world since the beginning of recorded history. It is particularly common in arid and semi-arid areas where evapo-transpiration exceeds annual precipitation and where irrigation is necessary to meet crop water needs, In the past, soil salinity was mainly associated with high ground water tables, which salts into the root zone through the capillary rise. But now-a-days, increasing exploitation of ground water for irrigation purposes has led to decline the ground water tables, and a threat of sodification and salinisation due to use of poor quality ground water. Same is the case in Lachi valley, where ground water is mined, and as a result salts are added to the root zone because a high proportion of irrigation water is derived from pumped ground water of poor quality. Farmers of the area are facing a situation in which they have to deal with salt volumes that are harmful for water uptake of crops. They are also facing the problems of sodicity, which has an adverse effect on the physical structure of the soil. From the analysis of soil samples, it was found that about 47% of the area is non-saline, 25% is saline, and 28% is sodic-saline. The area where once all type of crops was grown is now restricted to only a few crops due to land degradation caused by deteriorating water quality. Sugarcane, an important cash crop, has ceased to be grown while yields of maize and wheat have decreased drastically. The areas where tubewells water is normal, there the production is high for both the wheat and maize (3.5 and 6.5tons/ha respectively, but in the areas, where soil has been deteriorated due to application of saline tubewells water, there the yield of both the crops have been seriously affected (2.2 and zero tons/ha respectively).