effect of crop residue and nitrogen fertilizer on nitrogen use efficiency in corn (zea mays l.) production

nitrogen is one of the most limiting nutrients for cereal production in many parts of iran. the effects of crop residue incorporation [0 (control), 25 and 50% of wheat (triticum aestivum l.)] and nitrogen (n) levels (0, 150, and 300 kg ha-1) on corn (zea mays l.) grain yield and nitrogen use efficiency were investigated at agricultural research station, shiraz university, shiraz, iran for two years (2009-2010). the experiments were carried out as a split plot based on randomized complete blocks design with three replications. the results showed that with increasing nitrogen fertilizer (from 150 to 300 kg ha-1) and crop residues (from 25 to 50%), rne (recovery n efficiency) and ane (agronomic n efficiency) were reduced. application of nitrogen more than 150 kg ha-1 increased the amount of nitrogen loss from 69 to 121 kg ha-1. there was a liner relationship between the amounts of nitrogen higher than 150 kg ha-1, and the nhi (nitrogen harvest index), but adding more than 50 percent of crop residues caused no significant difference in the nhi. the maximum grain yield was obtained in plants treated with 300 kg n ha-1 and 25 percent of crop residues incorporation. according to results, the use of 25% of crop residue and 150 kg n ha-1 due to acceptable yield, reduce nitrogen loss and increase the efficiency of nitrogen better than other treatments.