Does crop rotation yield more in China? A meta-analysis

Crop rotation has been widely used to mitigate weed, insect, and pathogen pressure, as well as to increase plant diversity. However, the magnitude of and variability in crop yield with rotation in China remain uncertain. We conducted a meta-analysis on 45 studies with 214 comparisons to examine the effects of crop rotation on yield and to explore the importance of environmental factors and field management in determining yield variability. Rotation increased crop yields by 20% on average when compared with continuous monoculture practices. Effects of rotation on crop yield were more pronounced in southwestern China (+ 38%) than in eastern China (+10%) and were notably less reliable and generally smaller in regions with moderate annual rainfall (400-550 mm). Rotation had greater yield benefits in soils with coarse or medium soil textures, intermediate levels of initial soil organic carbon (7-10 g kg(-1)), and lower total nitrogen (<= 1.2 g kg (-1))( ). Effect of rotation on crop yield also depends on the type of previously cultivated crops (hereinafter, pre-crops), ranging from 2% for Triticeae pre-crops to 27% for grain leguminous pre-crops. Yield increase under legume-based rotations was 14% higher than that without legumes. The mean yield response of the crop subsequent to rotation ranged from 6% (cereals, except for Triticeae crops) to 34% (root crops). The legacy benefit of rotation on subsequent crop yield persisted for 2-3 years, decreasing from +31% in the second year to +8% in the third year. Effect of rotation on crop yield under conventional tillage was greater than that under conservation tillage. The yield benefit of rotation on subsequent crops was much higher with a lower nitrogen fertilization rate (<= 120 kg ha(-1)), indicating that fertilization can be reduced and an acceptable yield maintained with crop rotation. In conclusion, crop rotation largely increases agricultural production without extra inputs, although its design may need to consider diverse climates, soils, crops, and management practices to maximize its agronomic and environmental benefits.