旱作农田绿肥填闲种植系统中的生态权衡问题

Ecological trade-offs in dryland cover cropping systems

绿肥填闲种植作为旱作农业区一种优良的传统轮作模式,如何在保证产量稳定提高的基础上,充分发挥其减施增益功能是个值得深入探讨的学术命题。该文从生态权衡视角出发,分析了该系统中存在的填闲作物与粮食作物水分竞争利用、填闲作物氮供应-氮固持、农田生态系统碳收支,三种关键权衡的生态学形成过程与生物学控制机理,并进一步探讨了基于“减施、稳产、增益”目标的权衡正向调控途径,提出未来研究应集中在明晰填闲作物生物量-作物生产力、填闲作物质量(碳氮比)-系统碳收支-生态环境效益之间的定量关系,揭示填闲种植系统生产力与环境效益在不同气候变化情景下的演变规律,以及开展填闲种植系统生态系统服务价值综合评估等领域,为绿肥填闲种植在我国西北旱作农业区的恢复与推广提供科学依据。

Introducing cover crop into cash cropping systems has been adopted world widely in the last decades,due to its multifunctionalities of soil fertility improvements,erosion and weed control,leaching reduction,etc.However,three key ecological trade-offs,including soil water pre-emptive competition between cover crops and cash crops,N supply and N retention of cover crop,and C emission and sequestration at the agroecosystem level,have limited the crop production and ecological benefits in cover cropping system especially in dryland areas.In this study,the ecological processes,biological mechanisms and regulation measures of three key trade-offs in cover cropping systems were summarized systematically aiming to maintain crop yield and improve ecological benefits.The future researches should focus on the relationships between cover crop biomass and crop yield,and among cover crop residue quality(C:N ratio),C budget and ecological benefits.More concerns should also be given in the evolution crop production and ecological benefits under climate change scenarios,and the assessments of cover crop ecosystem services.These knowledges will promote the reconstruction and extension of cover cropping in the dryland agriculture especially in the Northwest China.