Water-use efficiency of irrigated winter maize under cool weather conditions of India

Field experiments were conducted during 1993/94 and 1994/95 in the sub-humid tropic environment of northern India to identify suitable irrigation schedule(s) for winter maize (December to May). Based on plant growth stages, viz. knee-high, tasselling, flowering, silking, grain-filling and dough, which occurred, respectively, at 55, 75, 95, 105, 125 and 145 days after planting, the crop was subjected to six irrigation treatments, which were: no irrigation (I0); irrigation given at all the growth stages (I1); irrigation missed at knee-high (I2); at knee-high and dough (I3); at knee-high, flowering and grain-filling (I4); and at knee-high, flowering, silking and dough stages (I5). The change in profile soil water content, deltaW (depletion) of the entire crop-growing season was found to be in the order I0 > I5 > I4 > I3 > I2 > I1. Of the total net water use (NWU), about 87% was evapotranspiration and 13% deep percolation losses. The NWU was highest (472 and 431 mm) under I1 and lowest (223 and 240 mm) under the I0 treatment during the two cropping seasons. Compared to I1, NWU in I3 decreased by 23% and 12.3% and in I4 by 33.8% and 24.2% in the two cropping seasons. However, there was no statistically significant difference (at LSD, P=0.05) between yields of the I1 to I4 treatments during either year. The NWU was found to be in the order I1 > I2 > I3 > I4 > I5 > I0, whereas the water-use efficiency (WUE) based on NWU was found to be in the reverse order: I5 > I4 > I3 > I0 > I2 > I1. Maximum yield (5.14 t ha(-1)) with WUE of 1.39 kg m(-3) was obtained under the I3 treatment. However, optimum yield (4.91 t ha(-1)) with high WUE of 1.54 kg m(-3) was under I4. Accordingly, irrigation applications greater than 240 mm did not provide additional yield of winter maize. Frequent irrigations (I1) proved detrimental to grain yield of winter maize in the northern Indian plains, especially under cool weather conditions, where minimum temperature (6 degrees C) can be accompanied by occasional frost.