曲周县小麦-玉米轮作体系氮收支特征及氮管理对策研究

Nitrogen Flow Characteristics and Management of Wheat-Maize System in Quzhou

氮是制约农业可持续发展的重要元素之一,合理的氮管理标准是提高农业可持续生产的基础。然而,在不同的历史时期,我国农田氮管理标准及其对农业生产系统全链条可持续生产的贡献尚不清楚。以河北省曲周县农业生产系统为研究对象,利用物质流方法系统地定量研究了曲周县1983年和2010年小麦-玉米体系氮流动特征,并通过对长期定位试验结果数据的整合,明确了实现曲周小麦-玉米栽培体系可持续生产的氮管理标准,同时利用生命周期评价法(LCA)分析了氮管理标准对农业生产系统全链条可持续性的作用。与1980年相比,2010年曲周县氮输入和收获物氮输出分别增加了2.5和1.3倍,氮输入增加的速度远大于籽粒氮输出,使氮肥利用效率从51%降低到了37%。长期定位试验结果表明,小麦-玉米体系合理的氮投入为108.3~185.8 kg hm^(-2),而当前农田化肥氮投入为298.3 kg hm^(-2),超出阈值0.6~1.8倍。与曲周县当前氮投入相比,在阈值范围内氮投入,可使小麦-玉米体系的氮肥偏生产力提高1.1倍,单位粮食生产的环境代价降低68.4%;采用综合管理技术,将曲周县小麦-玉米体系中的氮投入降低到185.8 kg hm^(-2),能够使收获物中氮输出量增加27.4%、氮盈余量减少98.3%且氮肥利用效率达到70%。这些结果表明合理的氮管理标准是实现农业生产系统氮高效利用的关键,意味着实施合理的氮管理标准是提高农业生产系统可持续性的有效措施之一,这为未来的农业可持续发展转型提供了方向。

Nitrogen(N) is one of the most important elements that limit the sustainable development of agriculture.Rational N management standards are the basis for improving sustainability of crop production. However, N management standards for high-yield crop production and its contribution to the whole chain of crop production in the North China Plain were not fully understood. N flow of wheat-maize system in 1980 s and 2010 s in Quzhou, a typical agriculture county in the North China Plain, was quantified. N management standards for sustainable crop production in Quzhou was established by integration of long-term field experiments, and its contribution to sustainable crop production was evaluated. The results showed that: compared with 1980 s, N input and output of wheat-maize system in Quzhou in the 2010 s wereincreased by 5.1 and 1.2 times, respectively. This resulted in N use efficiency(NUE)wasreduced from 55% to 32% in the 2010 s. The optimal N input in the high-yield wheat-maize system in Quzhou was 108.3-185.8 kg hm^(-2) based on the integration of long-term field experiments.N input in the wheat-maize cropping system in Quzhou was 298.3 kg hm^(-2), which was 0.6-1.8 times higher than that in the long-term field experiments. Partial factor productivity of N(PFP-N) in the wheat-maize cropping system wasincreased by 1.1 times by reducing N input to the optimal level with the integrated nutrient management technologies. And hence, global warming potential of grain production was reduced by 68.4%. In the whole farming system, N output was increased by 27.4%, N surplus was decreased by 98.3%, and N use efficiency reachedhigher than 70%. The results indicated that optimal N management standard is the key for high NUE in high-yield wheat-maize cropping system.It means that integrated N management technology is one of the effective approaches to improve the sustainability of high-yield cropping system, which provides a potential approach to transform agriculture towards sustainable intensification.