Does Mixing Trees and Crops Enhance Soil Organic Carbon Content in China? Evidence From Integrating Field Experiments With a Meta-Analysis

Abstract

Mixing trees and crops (MTC) practices are emerging as a viable strategy for promoting sustainable agriculture in developing countries, such as China. While many studies have reported data on the relationship between soil organic carbon (SOC) and MTC practices, a comprehensive quantitative analysis of their effects on SOC content nationwide in China is still lacking. In the present study, we integrated field experiments with a national-scale meta-analysis to quantitatively analyze the effects of MTC practices on SOC content in China. The findings of the field experiments and subsequent meta-analysis provide evidence indicating that MTC practices significantly enhance SOC content in China. In contrast to single-cropping crop practices, MTC practices in China significantly increased the SOC content by 26.6% overall. In contrast to single-cropping tree practices, MTC practices in China increased the SOC content by 20.0% overall. Nevertheless, it is necessary to acknowledge that there was high variability in the effects of MTC practices on SOC content across different regions of China. Additionally, the effects of MTC practices on SOC content could be affected by climatic conditions, tree age, tree species, crop species, and soil depths. Among them, crop species, tree age, and tree species were the most important factors affecting SOC. Overall, from the perspective of enhancing SOC in China, MTC may be a more preferable sustainable practice than single cropping. However, factors such as economic benefits, food security, and other ecological values should also be considered when formulating sustainable agricultural management strategies.