Effect of water deficit and different nitrogen rates on growth and development stages, yield and yield component of maize (Zea mays L.)

Plants are exposed to environmental stresses. Water and nitrogen availability are two major factors for crop production under different conditions. In order to determine the effects of water deficit and different nitrogen rates on growth and developmental stages, yield and yield components of corn, two field experiments were conducted using a randomized complete block design in 2001 growing seasons. Two corn hybrids (KSC 108 and KSC 301) were used under water and nitrogen stresses at vegetative and reproductive growth stages in two locations (Hamedan and Karaj). The result indicated that phenological stages delayed under water and nitrogen stresses in different treatments. Leaf area index decreased as availability of water and nitrogen decreased. Significant differences were observed between two hybrids for biological yield, grain yield and yield components. The lowest biomass and grain yield were produced in water stressed plants at both vegetative and reproductive stages. The different rates of nitrogen utilization shown significant effect on grain yield. Water deficit at vegetative and reproductive growth stages decreased the grain yield by 15% and 20%, respectively in comparison with controls. Relative water content reduced by 15-18% under water and nitrogen stresses. There were no significant differences in harvest index, but stress index (SI) was different between stressed treatments. The maximum stress index (SI) belonged to KSC 301 under water stress at the vegetative and reproductive growth stages.