Screen for sustainable cropping systems in the rain-fed area on the Loess Plateau of China

A challenge for dryland crop production in China is closing the yield gap while propelling the sustainable development of agriculture when the natural resources are limited. A 4-year fixed field experiment was conducted to analyse the effect of introducing leguminous green manure (LGM) to different cropping systems on soil water, residual nitrate, soil quality and economic benefits to compare their sustainability using a comprehensive scoring system. The main treatments of the experiment were different cropping systems, leguminous green manure-winter wheat (LGM-WW) and leguminous green manure-spring maize-winter wheat (LGM-SM-WW) with summer fallow-winter wheat (SF-WW) as control. LGM late incorporation, early mulch and early incorporation were sub-treatments for LGM-WW while stalk mulch, incorporation and move-away were the sub-treatments for LGM-SM-WW to study the effects of different LGM managements. Compared with SF-WW, LGM-WW decreased average soil water storage before wheat seeding by 11% and increased residual nitrate storage after wheat harvest by 77% while they were not significantly changed for LGM-SM-WW. The soil organic carbon (SOC) content of LGM-WW and LGM-SM-WW in the 0-20-cm layer significantly increased when using legume as mulch. The economic benefits of LGM-SM-WW were 2 times greater than those of the other 2 cropping systems. The scoring system indicates that the total score of LGM-WW ranged from 11.85 to 12.78, which was even lower than that of SF-WW (13.07). On the contrary, the total score of LGM-SM-WW ranged from 16.46 to 18.49. In conclusion, the scoring system determined that the optimum cropping system for sustainable dryland agriculture is leguminous green manure-spring maize-winter wheat with legume stalk mulch.