Objectives Appropriate nitrapyrin-urea application amount was studied for the less soil N2O emission and high profit in summer maize and winter wheat production system.
Methods Nitrapyrin was sprayed on urea in ratio of 1.1‰ to make nitrapyrin-urea. Four application rates were designed in summer maize and winter wheat in field plot experiments. For maize, the nitrapyrin-urea N rates were 0, 180, 270 and 360 kg/hm2,for wheat were 0, 150, 225 and 300 kg/hm2. Yield and nitrogen fertilizer profits were investigated; soil N2O emission was determined using the static chamber method.
Results The results showed that soil N2O emission peaks appeared after the basal or topdressing fertilization of nitrapyrin-urea. With the increase of N fertilization rates, the soil N2O emission, N apparent loss, N2O emission intensity were increased. Compared with the N0, the yields of the crops were significantly increased by 27.9%-48.9%, 28.3%-51.7% and 28.1%-48.9% in maize, wheat and the rotation system. There was no significant difference in maize yields between the N rates of 270 and 360 kg/hm2, and the net incomes of these two treatments were 5208.0 and 5425.4 yuan/hm2, respectively. The wheat yield and net income were both the maximum in the nitrapyrin-N fertilization rate of 225 kg/hm2. For the whole rotation system, the yields of grain were increased with nitrapyrin-N fertilization rates, compared to the treatments of nitrapyrin-N rates of 360 and 300 kg/hm2 in maize and wheat, the yields of the treatments of nitrapyrin-N rates of 270 and 225 kg/hm2 in maize and wheat were similar, while the soil N2O emission was decreased by 1.51 kg/hm2 and the N apparent loss in soil was decreased by 39.4 kg/hm2, and the N fertilization amount reduced by 165 kg/hm2, net income increased by 405.3 yuan/hm2.
Conclusions Under the experimental condition, the appropriate nitrapyrin-N fertilization rates are 270 kg/hm2 for maize and 225 kg/hm2 for wheat.
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