基于WNMM模型的玉米/马铃薯间作氮素淋失研究

Intercropping, as a planting model, have been widely spread and applied in agricultural production. Previous studies on intercropping concentrated primarily on the yield, economic benefits, interspecies relations and control of pests and diseases in intercropping system; little information was available to show environmental impacts of intercropping, like nitrogen leaching. Based on sole cropping of maize and potato, and intercropping of maize/potato, this research will focus mainly on: 1) revealing the effect of maize/potato intercropping on soil nitrogen leaching and its mechanism compared with sole cropping; 2) exploring the response of nitrogen leaching to fertilizer N application in maize/potato intercropping and the differences of response between cropping systems; 3) revising water and nitrogen management model to simulate crop growth and transport of water and nitrogen, thus forecasting the optimal application rate of N fertilizer in maize/potato intercropping, which synthesizes the crops yield and nitrogen leaching risk. The studies in the project, thereafter, can provide theoretical and decision-making basis for the environmental risk assessment and control of nitrogen leaching in intercropping system.

间作种植模式在农业生产上得到大面积地推广和应用。当前人们对间作的研究主要集中在间作条件下作物产量、经济效益、种间关系以及间作对作物病虫害的控制作用等；较少地关注间作条件下诸如氮淋失等环境风险。本项目基于玉米单作、马铃薯单作和玉米/马铃薯间作三种种植模式，主要研究以下内容：1）相比于玉米、马铃薯单作系统，玉米/马铃薯间作对土壤氮淋失的影响及其机制；2）玉米/马铃薯间作的氮淋失对氮肥施用的响应及其与单作系统氮淋失响应的差异；3）对WNMM模型进行修订以模拟玉米/马铃薯间作的作物生长和水氮迁移，并预测该种植模式下综合产量和氮淋失风险的最佳氮肥用量。本项目研究可以为间作环境风险评价、氮淋失控制提供理论基础和决策依据。

间作的产量优势、资源利用、种间关系和病虫害控制方面的研究和认识已较为深入。而间作条件下诸如氮淋失风险等环境影响较少被关注，使间作环境效应评估缺乏理论支撑。本项目选取种植面积较大的玉米马铃薯间作，以玉米单作、马铃薯单作为对照，分别设置不施氮（N0）、低氮（1/2常规N，N1）、常规氮（N2）和高氮（3/2常规N，N3）4个施氮水平，评估间作对土壤剖面硝态氮累积的影响及其对氮投入的响应，并进行WNMM模型的修订和验证。. 研究结果表明：（1）由于间作的产量优势，单位产量深层土壤（60～75 cm）硝态氮累积比单作加权平均降低14.7～53.9%。不施氮、低氮时，间作对单位面积土壤剖面硝态氮累积无影响，在常规氮和高氮水平时比单作加权平均减少17.0%和28.3%。（2）间作深层土壤剖面硝态氮累积对施氮量的响应低于马铃薯单作和玉米单作。（3）与单作相比，间作对土壤剖面硝态氮累积的影响与作物氮素吸收、土壤氮素转化和其他氮素损失有关。（4）从水分、氮吸收和光资源利用对WNMM修订后，模型可较好地模拟间作下土壤剖面硝态氮累积。项目研究为玉米马铃薯间作硝态氮淋失风险评价和利用间作控制硝态氮淋失提供了理论支撑，促进了间作的氮淋失风险模型模拟。