Effect of different irrigation schedules on water use and yield of wheat

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 use and yield of wheat. Experiments were conducted with one wheat variety, four irrigation intervals i.e. three weeks (W3), four weeks (W4), five weeks (W5) and six weeks (W6) and two pan levels i.e. equal to pan evaporation (P1) and half of the pan evaporation (P2) using randomized complete block design. Soil moisture content was determined by gravimetric method. Actual evapotranspiration (ETa) was calculated by water balance method. The crop coefficients were determined from the ratio of actual evapotranspiration to potential evapotranspiration. The average seasonal evapotranspiration of wheat were 518, 439, 496 and 478 mm and crop coefficients were 1.02, 0.87, 0.96 and 0.94, for W3, W4, W5 and W6, respectively. Results of yield and its components indicated that there was significant effect of irrigation intervals on grain yield, number of grain per spike, grain weight per spike, number of tillers per plant and visual lodging percentage. There was no difference in yield and yield components when the crop was irrigated according to the full evaporation (P1) and half pan evaporation (P2). 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 case of number of tillers and lodging percentage, the result showed that more moisture favours greater number of tillers and lodging percentage. The highest water use efficiency (8.01kg per hamm-1) was obtained when crop was irrigated after five weeks interval. It is concluded that for maximum yield of wheat the crop may be irrigated after five weeks interval. Excessive and earlier than five weeks irrigation interval can be harmful for the optimum yield of wheat if seasonal rainfall is greater than or equal to 330 mm.