CONSUMPTIVE USE OF WATER FOR WHEAT IN SOUTHERN N.W.F.P.

Field research experiments on wheat (C.V. Sonalika) were conducted on a silty clay loam soil with pH 8.2 under tubewell irrigation water of marginal quality at the Arid Zone Research Sub-Station, Dera Ismail Khan during the Rabi seasons of 1982-83 and 1983-84. Four moisture stress levels (50, 65, 80 and 95 percent depletion) were tested under two fertilizer levels of 75-50-30 and 150-75-30 (NPK) kg/ha in a randomised complete block design. The average consumptive use of water (CUW) values for the four(4) moisture stress levels were computed to be 430, 402, 372 and 349mm of water. The moisture stress-yield function data for both the seasons indicated that the optimum grain yield of 3146.8 kg/ha was obtained when the crop was irrigated at 50% soil moisture depletion level under high ( 150-75-30 (NPK) kg/ha ) fertilizer level. It was further indicated that increased fertilizer use compensated for increased moisture stress. The highest water use efficiency of 7.32 kg/mm/ha was obtained when the crop was irrigated at 50 percent soil moisture depiction.