The effect of released nitrogen from different crop residues on yield and yield components in wheat

Crop residues could be considered as nitrogen supply resources. To study the effects of diffrenet crop residues on soil mineral nitrogen a four replicated experiment with six treatments as a RCB desing was conducted. Four crop residues (including cotton، corn، wheat and alfalfa)، urea and check were treatments were used. Crop residues were sliced to <5mm and were incorporated with soil. Nitrate and ammonia were analyzed during different phonological stages of wheat. Results revealed that nitrate + ammonia values in soil were not different significantly. The highest and leas values (75. 3 and 62. 77 kg ha-1) belonged to urea and check treatments respectively. The highest value among residues was seen in alfalfa treatment. Yield and yield components also were affected significantly، as the highest and least grain yield (8695 and 6962 kg ha-1) were obtained in alfalfa and urea treatment، respectively. Results indicated that nitrogen changes interpretation without considering two directional path of nitrogen releasing in soil and its uptake by plants is impossible. Non significant difference between residue and urea treatment with check treatment in respect to nitrate + ammonia revealed that this variety (N8019) is a high-demanding variety with high uptake rate. Also، results revealed that residues are advisable، at least because of reducing fertilizers application even if no yield reduction occurs.