氮肥与氮转化调控剂配施降低夏玉米-冬小麦农田N2O排放

针对农业生产中氮肥施用不合理导致氮肥利用率低、N_2O排放增加及经济效益下降等问题,采用田间试验法研究了不同氮肥与氮转化调控剂配施模式的夏玉米-冬小麦一年两作农田N_2O排放特征及经济效益。结果表明:与农民施氮肥处理(FN)相比,各推荐施氮处理在夏玉米季和冬小麦季的N_2O平均排放通量分别降低29.2%~65.4%(P0.05)和26.9%~74.9%(P0.05),N_2O排放总量分别降低1.05~2.72(P0.05)和1.10~2.47(P0.05)kg/hm~2;整个轮作季纯收益增加967.5~3 887.0元/hm~2。同等施氮量条件下,与推荐施氮处理(RN)相比,夏玉米季推荐施氮配施双氰胺处理(RN+DCD)和推荐施氮配施吡啶处理(RN+CP)分别使N_2O平均排放通量降低41.5%(P0.05)和31.2%(P0.05);而在冬小麦季则分别下降63.0%(P0.05)和65.7%(P0.05);整个轮作季RN+DCD和RN+CP处理N_2O排放总量分别降低了52.5%(P0.05)和49.0%(P0.05),纯收益分别增加312.6和708.9元/hm~2。夏玉米季,土壤N_2O阶段排放峰值出现在三叶期-拔节期和大喇叭口期-抽雄期;而冬小麦季土壤N_2O阶段排放峰值出现在播种-冬前苗期和返青-拔节期。考虑作物产量、N_2O排放以及经济效益,RN+DCD和RN+CP处理经济效益较高,N_2O排放总量较少,是兼顾作物产量、农民收入及大气环境的推荐氮肥管理措施。

Nitrogen fertilizers application combined with N conversion control additives reducing N2O emissions under summer maize-winter wheat cropping system

Nitrous oxide (N2O) is a major greenhouse gas (GHG) product of intensive agriculture. The application of nitrogen fertilizer can increase the N2O emissions, and the amount of N2O from fertilizers accounted for 25%-82% of the total soil N2O emissions. Therefore, in order to addressing the serious problems in the agricultural production, such as lower nitrogen fertilizer utilization ratio, increased N2O emissions and declined economic benefit caused by unreasonable nitrogen fertilizer application, a field experiment were conducted to study the effect of different nitrogen fertilizer application patterns on characteristics of N2O emissions and the economic benefit in a summer maize-winter wheat field. The 7 patterns of nitrogen application in the summer maize and winter wheat seasons were control (CK), farmer's nitrogen fertilization pattern (FN), recommended nitrogen fertilization pattern (RN), recommended N rate with dicyandiamide (RN+DCD), recommended N rate with nitrapyrin (RN+CP), recommended N rate with controlled-release fertilizer (RN+CR), recommended N rate with nanocarbon (RN+NC). The CK was without applications of nitrogen fertilizer. During summer maize and winter wheat seasons, the nitrogen fertilizer of FN treatment was 392 and 285 kg/hm2, and the nitrogen fertilizer of the recommended nitrogen treatments (RN, RN+DCD, RN+CP, RN+CR and RN+NC) were 300 and 225 kg/hm2 respectively. The N2O emission from soil was collected by static chamber method and the gas samples were determined by gas chromatography with Agilent7890.The total income obtained from the crop grain minus the cost of the fertilizer and other field management costs was recognized as net income. The results showed that, compared to the treatment of FN, theaverage N2O emission flux of recommended nitrogen treatments (RN, RN+DCD, RN+CP, RN+CR and RN+NC) were reduced by 29.2%-65.4% (P<0.05) and 26.9%-74.9% (P<0.05) during summer maize and winter wheat seasons respectively, and the total N2O emissions were decreased by 1.05-2.72 kg/hm2 (P<0.05) and 1.10-2.47 kg/hm2 (P<0.05), respectively. In the rotation season, the net income increased by 967.5-3887.0 Yuan/hm2 compared to that of FN treatment. Compared to the treatment of RN, the average N2O emission flux of the treatments of RN+DCD, RN+CP and RN+CR were decreased by 41.5% (P<0.05), 31.2% (P<0.05) and 5.8% respectively during the summer maize season, and those were decreased by 63.0% (P<0.05), 65.7% (P<0.05) and 25.4%respectively during the winter wheat season. In the rotation season, the total N2O emissions of RN+CP and RN+DCD were decreased by 52.5% (P<0.05) and 49.0% (P<0.05) respectively, and the net incomes of the two treatments were increased by 312.6 and 708.9 Yuan/hm2, respectively. The soil N2O phase emission of peak during the summer maize season appears in the three leaves period to jointing stage and huge bellbottom period to tasseling stage, but during the winter wheat season the soil N2O phase emission of peak appears during the stages of sowing time to seedling stage and the returning green stage to jointing stage. Considering the integrated effects of crop yields, N2O emissions and economic benefit, RN+DCD and RN+CP were recommended for nitrogen management practices which can gain rational crop yield, reasonable income and less negative climatic and environmental impacts.