氮肥减量及秸秆替代过量氮肥下冬小麦/夏玉米轮作体系氮素淋失风险研究

EFFECTS OF REDUCING NITROGEN APPLICATION AND REPLACING PART OF NITROGEN FERTILIZER BY CROP RESIDUE ON NITROGEN LEACHING IN WINTER WHEAT -SUMMER CORN SYSTEM

关键词:  冬小麦 夏玉米 氮平衡 硝态氮累积 产量 淋洗风险

Key words:  winter wheat  summer corn  nitrogen balance  nitrate nitrogen accumulation  yield  N leaching risk

摘要:

针对过量施用氮肥和地下水硝酸盐超标的现状，探索减量施氮、秸秆替代过量氮肥下土壤氮素的淋失风险，以期为降低氮素淋失风险提供科学依据。通过在河北省徐水县进行连续4年的冬小麦—夏玉米轮作体系田间定位试验，分析耕作（少耕和常规耕作）、施氮量（无机氮0、200和300 kg/hm2）和秸秆（还田、不还田）等措施对作物收获后土壤无机氮累积、土壤—作物体系氮平衡状况以及冬小麦和夏玉米产量的影响。结果表明，小麦收获后，过量施氮处理0～100 cm土壤硝态氮累积量显著高于其它处理，高达221 kg/hm2，过高的土壤残留硝态氮增加玉米高温多雨季氮素淋洗风险。3年氮平衡累积量比较显示，过量施氮、少耕/常规耕作减量施氮秸秆还田3处理的氮平衡值无显著性差异，以少耕减量施氮秸秆还田最低，为236 kg/hm2，过量施氮处理最高，为281 kg/hm2，三者均显著高于少耕/常规耕作减量施氮秸秆不还田处理。冬小麦—夏玉米轮作体系氮平衡值与0～100 cm土层的土壤无机氮、土壤硝态氮累积量呈显著正相关，说明氮素大量盈余会导致0～100 cm土壤剖面无机氮大量累积，尤其是硝态氮大量累积。少耕和常规耕作减量施氮秸秆还田处理的冬小麦、夏玉米产量与过量施氮无显著差异。综合考虑土壤无机氮累积量、氮平衡值和作物产量，少耕或者常规耕作下，可以利用秸秆氮替代过量无机氮，降低氮素淋洗风险。

Abstract:

There is a growing concern about excessive nitrogen and excessive level of nitrate in groundwater in China. A four-year study in Xushui, Hebei, China was conducted in a winter wheat and summer corn cropping system to compare the effects of soil tillage (minimum tillage without ploughing, full tillage), application of cornstalk residue (none -R, turning back +R) and three N rates (0, 200 and 300 kg N /hm2 as mineral nitrogen) applied to winter wheat on the yield of wheat and subsequent corn, the N balance and the inorganic N accumulation, and then to investigate the possibility of the residue replacing some rate of mineral N in case of N leaching . Moreover, the same rate of mineral N (100 kg/hm2) was applied to all plots for the corn. The results showed that the soil nitrate nitrogen accumulation (221 kg/hm2) in full tillage with 300 kg N /hm2 (FT N300 -R) after wheat harvest was significantly higher than that in the other treatments, the excess nitrogen may increase the risk of nitrogen leaching. The three-year nitrogen balance value in the millage tillage or full tillage with 200 kg N /hm2 and residue turning back (MT N200 +R, FT N200 +R) were not significant.Furthermore, there was significantly positive relationship between nitrogen balance value and nitrate nitrogen accumulated in 0-100cm soil profile, itmeant the greater the N balance value, the more the amount of nitrate nitrogen accumulated. In addition, the yields of wheat and corn in MT N200 +R and FT N200 +R were not significantly different with those in FT N300 -R. It indicatedthat using residue nitrogen as part of mineral nitrogen in the treatment of reducing the rate of nitrogen (200 kg N /hm2) could not only maintain the crop yield and reduce N balance value, but also significantly reduce nitrate nitrogen accumulation after wheat harvest, and hence reduce the risk of N leaching.