Intensive irrigated rice-wheat crop systems have caused serious soil
depletion and nitrogen loss in China. A possible solution is the incorporation of legumes in rice, but little is known on the impact of
legumes on rotation, soil fertility, and nitrogen loss. This study considered the effect of five rice-based rotations on soil nitrogen,
rice yield, and runoff loss. Results
show that replacing 9.5–21.4 % of nitrogen fertilizer by
rape, vetch or bean residues maintained rice yields, and using legumes
as a winter crop in rice-bean and rice-vetch combinations increased
rice grain yield 5 % while decreasing nitrogen runoff 30–60 %.