Evaluating Yield Variations of Corn (single cross 260) at Different Water Regimes and Nitrogen Rates by Using of Growth Indices

To evaluate the effects of different irrigation and nitrogen levels on variations of growth indices and corn (Single cross 260) seed yield, an experiment was conducted in a semi-arid area in Fars Province, Iran, during 2011 and 2012 growing seasons. The experiment was split-plot, based on a complete randomized block design with four replications. The main plots consisted of four moisture levels: (20% FC), (40% FC), (60% FC) and (80%FC) and sub-plot of four rates of nitrogen fertilizer applications: 150, 200, 250 and 300 kg.ha-1. Results showed that with increasing nitrogen fertilizer levels, LAI, NAR, SLA and RGR were also increased, but under lower moisture regimes they were decreased. The lowest and highest growth indices belonged to 80% and 20% water depletion, respectively. The lowest CGR index was obtained at 80% water depletion and 150 and 300 kg nitrogen ha-1. LAR increased at the intial growth period and then decreased. Positive relationships between seed yield and growth indices were also observed. At FC 20% and 300 kg N ha-1 treatment highest grain yield was obtained and growth indices were also in the highest values. In general, nitrogen application increased all traits. However, there were not significant differences between 250 and 300 kg N ha-1on the traits under study. It seems that nitrogen fertilizer mitigates the negative effects of water deficiency. Application of 250 kg of nitrogen fertilizer had the highest effect on all levels of moisture content.