Investigate the effect of different levels of irrigation, nitrogen and weeds competition on growth indices and grain yield of maize (SC. 704 Hybrid)

This experiment was conducted in split split plots arrangement in a randomized complete blocks design with three replications at the field of Shahid Salemi Ahvaz in 2014. In this experiment the effect of three levels of irrigation after 60 (desirable), 100 and 140 millimeter evaporation from evaporation pan and three levels of pure nitrogen 120, 180 and 240 kilogram per hectare and two levels of the presence and absence of weeds were compared. Different levels of irrigation and nitrogen in main plots and sub plots, respectively; and weeds treatment in the sub sub plots were maintained. The results indicated that effect of different levels of irrigation on leaf area index, total dry matter, crop growth rate, net assimilation rate and grain yield of maize was significant. The growth indices and grain yield were decreased with increasing duration of irrigation. The treatment of 140 millimeter evaporation from evaporation pan led to decrease the leaf area index and grain yield by the amount of 37.7 and 35.6 percent as compared to treatment of 60 millimeter evaporation from evaporation pan. Increasing nitrogen level from 120 to 240 kilogram per hectare significantly increased the leaf area index, total dry matter, crop growth rate and maize grain yield by 9.6, 9.7, 14.4 and 13.6 percent. Also, leaf area index, total dry matter, crop growth rate and grain yield in the conditions of presence of weed in comparison with the absence of weed significantly reduced. Results of present study showed that irrigation levels as compared to nitrogen and weed competition is more effective factor on growth indices and grain yield of maize. Therefore, in areas with limited water resources, increasing application of nitrogen is not necessary. It seems that irrigation levels through the impact on leaf area index, affect other the physiological indices and ultimately leads to a reduction on maize grain yield.