EFFECT OF DIFFERENT IRRIGATION SCHEDULES ON WATER USE AND YIELD OF WHEAT

Abstract

The research was conducted on clay loam soil of NWFP Agricultural University Farm during Rabi, 1997-98 to study the effect of different irrigation schedules on water u se and yield of wheat. Experiments were conducted with one wheat variety, four irrigation intervals i.e. three weeks (W 3), four weeks (W 4), five weeks (W 5) and six weeks (W 6) and two pan levels i.e. equal to pan evaporation (P 1) and half of the pan evaporation (P 2) using randomized complete block design. Soil mois ture content was determined by gravimetric method. Actual evapotranspiration (ETa) was calculated by water balance method. The crop coefficients were determined from the rati o of actual evapotranspiration to potential evapotr anspiration. The average seasonal evapotranspiration of wheat were 5 18, 439, 496 and 478 mm and crop coefficients were 1.02, 0.87, 0.96 and 0.94, for W 3, W4, W 5 and W 6, respectively. Results of yield and its component s indicated that there was significant effect of irrigation intervals on grain yield, numb er of grain per spike, grain weight per spike, numb er of tillers per plant and visual lodging percentage. There was no difference in yield and yield components when the crop was irr igated according to the full evaporation (P 1) and half pan evaporation (P 2). Maximum yield was obtained when plots were irrigated after five weeks interval. Same was the case with number of grains per spike and grain weight per spike. But in c ase of number of tillers and lodging percentage, the result showed t hat more moisture favours greater number of tillers and lodging percentage. The highest water use efficiency (8.01 kg ha -1 mm -1 ) was obtained when crop was irrigated after five w eeks interval. It is concluded that for maximum yield of wheat the crop may be irrigated after five weeks i nterval. Excessive and earlier than five weeks irrigation interval can be harmful for the optimum yield of wheat if seasonal rainfall is � 330 mm.