Nitrogen nutrition and water stress effects on growth, yield and water use efficiency of wheat (Triticum aestivum L.)

Field experiments were conducted on a sandy loam soil in 2002-03 and 2003-04 growing seasons to determine the effect of nitrogen nutrition on growth, yield and water use efficiency of wheat under adequate and limited water supply conditions. The treatments comprised of four levels of irrigation (I1, one irrigation at tillering stage; I2, two irrigations, each at tillering and anthesis stages; I3, three irrigations, each at tillering, anthesis and grain development stages and I4, four irrigations, each at tillering, stem elongation, anthesis and grain development stages) in main plots and four N levels (0, 50, 100 and 150 kg N ha- 1) in sub-plots of a split plot design and were replicated three times. Increase in number of irrigations from 1 to 4 and nitrogen levels from 0 to 150 kg N ha-1, significantly (p less than or equal to 0.05) increased the average leaf area index (LAI), crop growth rate (CGR), yield attributes, and grain yield over the control (l0 and N0), in both the seasons. The maximum LAI and CGR were commensurate with highest levels of irrigation as well as nitrogen observed on an average during the 73-88 days after sowing (DAS) period of growth. The regression analysis revealed that LAI estimates with biological yield were 92% and 38% during the year 2002-03 and 2003-04, respectively. Mean grain yield in four, three and two irrigation treatments compared with that in one irrigation treatment increased by 47, 23 and 9 % during 2002-03 and by 91, 84 and 23 % in 2003-04, respectively. Water deficit reduced spikes m-2. In both years, the average reduction in spikes m-2 at maximum irrigation deficit (one irrigation) at all N levels was 24%. Similar reduction occurred in grain spike-1 where water deficit decreased this component on an average of 36 %. Mean water use efficiency (WUE) at all nitrogen levels was 41% higher in one irrigation treatment compared with four irrigations treatment. Significantly hi g her WUE was observed with 150 kg N ha-1 at all irrigation treatments. The water uses efficiency (WUE), decreased with increasing number of irrigations, whereas nitrogen application significantly improved WUE.