Response of soil organic carbon content to crop rotation and its controls: A global synthesis

Determining the effect of crop rotation (CR) on soil organic carbon (SOC) and its controls is vital for improving the potential benefits of CR in agroecosystems to achieve carbon neutrality. However, there has been no comprehensive and systematic evaluation of the response of SOC content to CR and its underlying drivers on the global level. Using 513 pairwise data from 167 studies, we conducted a global-scale meta-analysis to illuminate the changes in SOC content induced by CR and to explore the roles of climatic, edaphic, and agronomic factors in driving such changes. Results revealed that CR overall enhanced SOC content by 6.6% relative to continuous crop monoculture. SOC content under CR increased more in regions with intermediate mean annual temperature (MAT, 8–15°C) and precipitation (MAP, 600–1000 mm) than in regions with other climate types. CR had greater SOC content benefits in neutral (pH = 6–8) soils with loamy texture and medium levels of initial SOC (15–20 g kg–1) and total nitrogen (1.00–1.50 g kg–1). Also, CR performed better in the soybean-based cropping systems with more rotation cycles, longer rotation length, medium nitrogen fertilization input rate (100–200 kg N ha–1 yr–1), and the applications of no-till, straw retention, and organic fertilizers. Furthermore, the variance partitioning analysis revealed that soil (31%) and climate variables (18%) accounted for the major variations in SOC content response. Moreover, the random forest model demonstrated that soil texture, climatic factors (i.e., MAT and MAP), and initial SOC content were the predominant drivers of the response of SOC content. Overall, our findings highlight that CR is a critical practice to increase SOC content in global croplands, whereas the variations in response are governed by specific climatic, edaphic, and agronomic factors. This study helps to establish and manage site-specific CR systems that could enhance SOC in agroecosystems, ultimately facilitating carbon neutrality.