Effects of different farmland utilization types on soil organic carbon in China: A meta-analysis

Exploring the relationship between soil organic carbon (SOC) and different farmland utilization types can contribute to achieving carbon neutrality in agriculture. Over the past few decades, numerous researchers have conducted a multitude of studies on the effects of farmland utilization types on SOC in China, and these studies have yielded a wealth of data from field experiments. However, these experiments are limited in that they lack sufficient quantitative analyses of studies conducted on regional or national scales. In this study, we analyzed the three most common farmland utilization types (paddy field [PF], dry land [DL], and vegetable field [VF]) in China using a national-scale meta-analysis and included data from 108 observations from 28 studies in the field. In this meta-analysis, we conducted three comparisons (control vs. treatment): (a) PF versus DL, (b) PF versus VF, and (c) DL versus VF. The results showed that in comparison (a), DL had a significantly lower SOC than PF (ln R++ = -0.463, 95% confidence intervals [CIs] = -0.580 similar to -0.345), with DL showing 37.1% lower SOC than PF. In comparison (b), although there was no statistically significant difference between PF and VF (ln R++ = -0.078, 95% CIs = -0.167 similar to 0.011), VF had 7.5% lower SOC than PF. In comparison (c), VF had significantly higher SOC than DL (ln R++= 0.227, 95% CIs = 0.147 similar to 0.307), with VF showing 25.5% higher SOC than DL. It should be noted that the effects of farmland utilization types on SOC content observed in China varied depending on different factors such as the regions, climatic conditions, and cropping systems. In conclusion, SOC content could be affected by farmland utilization types. Therefore, in order to promote the development of low-carbon agriculture in China, it is important to consider farmland utilization types in agricultural production, as well as to consider carbon budgets, food security, and field practices to maximize agronomic and environmental benefits.