Improving the sustainability of cropping systems via diversified planting in arid irrigation areas

The development of productively viable cropping systems with lower environmental footprints to maintain sustainable agriculture in arid areas is urgently needed. Increasing crop diversity usually improves system productivity; however, the effects of crop diversification on the carbon footprint and the sustainability of a cropping system remain unclear. A 3-year field experiment (2018–2020) was conducted in northwestern China to determine the carbon footprint and productivity of five cropping systems, including spring wheat-common vetch/maize double relay cropping (three crops a year), wheat-maize intercropping (two crops a year) wheat-common vetch multiple cropping (two crops a year), monoculture maize (one crop a year), and monoculture wheat (one crop a year). The grain yield for wheat-common vetch/maize double relay cropping (the former) was higher by 8.7% in 2020 as compared to wheat-maize intercropping (the latter). For the same two cropping systems, the energy yield of the former was higher by 9.5–25.1% over 3 years. The carbon footprints of the former system were respectively 5.3%, 14.3%, 16.4%, and 7.4% lower than that of the latter in terms of unit area, kg grain yield, unit energy yield, and unit of economic output. Four carbon footprints of the former system were lower by 12.2%, 27.9%, 37.6%, and 29.6% compared with monoculture maize. The highest sustainability index was observed for a three crops per year system (0.94), due to higher productivity and a lower carbon footprint. This is the first demonstration that increased diversity via double relay cropping on the same plot annually maintained productivity without increasing the carbon footprint in arid irrigation areas. The results partly confirm the positive effect of diversified cropping systems by integrating multiple cropping green manure into an intercropping system. Adopting a diversified strategy exemplified by spring wheat-common vetch/maize double relay cropping contributes to improvements in sustainable crop production in arid, irrigated areas.