the effect of nitrogen fertilization management on grain yield and nitrogen efficiency indices in corn

among crop plants, corn (zea mays l.) need a great amount of nitrogen during its growth period. an increase in the efficiency of nitrogen application not only decrease environmental pollutions, but also it,s economical. this study was conducted to determine the effect of nitrogen fertilization management on the yield and nitrogen efficiency in corn during 2006-2009 at safi-abad dezful agriculture research center. the experiment was arranged as factorial in a randomized complete block design with three replications. the first factor consisted of four nitrogen levels (0,100,150 and 200 kg n ha-1) and the second factor consisted of five time of application levels (as 1/3+1/3 at sowing and 6- 8 leaves , as 2/3 at 6- 8 leaves, as 1/2 +1/2 at sowing and 6-8 leaves, as 1/3 + 1/3 + 1/3at sowing, 6– 8 leaves and tassel appearance, and 1/4 +1/4+1/4+1/4 at sowing, 6-8 leaves, tassel appearance and flowering). the result showed that nitrogen levels and time of application on grain yield and 1000 grain weight were significant. nitrogen levels on nitrogen efficiency indices and residual nitrate were significant. time of nitrogen application on nitrogen utilization efficiency was only significant. increasing in the amount of nitrogen application led to significant decrease the efficiency of nitrogen use, nitrogen uptake and nitrogen utilization, although, grain yield significantly increased. according to the result of this study, application of 150 kg n ha-1 with grain yield, 1000 grain weight and use efficiency of 7.96 t ha-1, 346 g and 44 kg kg-1 is recommended, respectively.