Hermiston Agricultural Research and Extension Center, Oregon State University, Hermiston, Oregon, USA.
Columbia Basin Agricultural Research Center, Oregon State University, Adams, Oregon, USA.
Glob Chang Biol. 2022 Aug;28(15):4736-4749. doi: 10.1111/gcb.16269. Epub 2022 Jun 8.
The global increases in the surface and groundwater nitrate (NO ) concentrations due to synthetic fertilizer input have emerged as major sustainability threats to terrestrial and aquatic ecosystems. Cover crops can reportedly reduce nitrate leaching from croplands. However, the underlying mechanisms and the effectiveness of cover crops in reducing nitrate leaching across species, soil types, agronomic management, and climates remain elusive. We conducted a global meta-analysis to evaluate the effects of cover crops on nitrate leaching and water drainage. A random-effects analysis was established to investigate seven moderating variables in 41 articles. Results showed that globally, cover crops reduced nitrate leaching by 69% compared with fallow while demonstrating no effect on water drainage. Overall, cover crops from Brassicaceae and Poaceae families showed the greatest effect with 75% and 52% reduction in nitrate leaching, respectively. Cover cropping on Ultisols, Histosols, and Inceptisols resulted in the greatest reduction in nitrate leaching (77%, 78%, and 77%, respectively). Greater efficacy of cover crops at reducing nitrate leaching was evident with increasing soil sand content. In general, cover crops appeared to perform better to reduce nitrate leaching in vegetable systems compared to field crops. Cover cropping on conventional tillage resulted in a 63% reduction in nitrate leaching compared with no-tillage (50%) and reduced tillage (38%) systems. The impact of cover crops on water drainage was nonsignificant which implies that nitrate leaching control by cover crops is unlikely exerted through reducing water drainage. This study brings further insight into the intrinsic factors affecting cover crop efficacy and management practices that enhance cover crop potential in reducing nitrate leaching from agricultural systems.
由于合成肥料的投入，全球地表水和地下水中的硝酸盐（NO3-N）浓度增加，这对陆地和水生生态系统构成了重大的可持续性威胁。覆盖作物据称可以减少农田中的硝酸盐淋失。然而，覆盖作物在减少不同物种、土壤类型、农艺管理和气候条件下硝酸盐淋失的潜在机制和效果仍不清楚。我们进行了一项全球元分析，以评估覆盖作物对硝酸盐淋失和排水量的影响。采用随机效应分析方法，对 41 篇文章中的 7 个调节变量进行了研究。结果表明，与休耕相比，全球范围内覆盖作物可减少 69%的硝酸盐淋失，但对排水量没有影响。总体而言，来自十字花科和禾本科的覆盖作物的硝酸盐淋失减少效果最大，分别减少了 75%和 52%。在腐殖土、弱育土和始成土上种植覆盖作物可最大程度地减少硝酸盐淋失（分别为 77%、78%和 77%）。随着土壤砂含量的增加，覆盖作物减少硝酸盐淋失的效果更为明显。一般来说，与大田作物相比，覆盖作物在减少蔬菜系统中的硝酸盐淋失方面似乎效果更好。与免耕（50%）和少耕（38%）系统相比，常规耕作下种植覆盖作物可使硝酸盐淋失减少 63%。覆盖作物对排水量的影响不显著，这意味着覆盖作物对硝酸盐淋失的控制作用不是通过减少排水量来实现的。本研究进一步深入了解了影响覆盖作物效果的内在因素以及增强覆盖作物在减少农业系统中硝酸盐淋失潜力的管理实践。
