Effect of Supplemental Irrigation and Nitrogen on Mean Grain Weight, Test Weight and Grain Yield of Wheat under Dryland Conditions

To investigate the effect of supplemental irrigation and nitrogen fertilizer on kernel weight, test weight and wheat grain yield under dryland conditions, a two-year field experiment was conducted in the research farm of College of Agriculture, Shiraz University during 2004-2005. Five irrigation regime including dryland conditions, irrigation at stem elongation, booting, flowering and grain filling constituted the main plots and two cultivars of Agosta and Fin-15 formed the subplots and while three levels of nitrogen including zero, 40 and 80 kgha-1 making the sub sub plots. The results indicated that in either of the years, the highest grain weight and test weight were obtained from irrigation at grain filling stage. Also the highest mean grain weight as well as test weight were obtained from 80 Kgha-1 nitrogen treatments. The results of this research also showed a strong correlation of mean grain weight and test weight with the amounts of nitrogen and water applied at supplemental irrigation treatments. The highest grain yield in both years was obtained from supplemental irrigation at stem elongation stage. The supplemental irrigations in 2004 and 2005 lead to an increase in the grain yield by 200 and 221 percent respectively. Also the highest grain yield was harvested from 80 Kgha-1 nitrogen treatment at all supplemental irrigation treatments. Thus, it can be concluded that supplemental irrigation at sensitive growth stages could significantly affect grain yield in rain-fed wheat, and a supply of adequate water and nitrogen at the appropriate growth stages could improve grain quality and increase yield in rain-fed wheat.