Effects of Biochar Application on Soil Organic Carbon Content in Farmland: A Meta-analysis

Objective The aims were to explore the effects of biochar application under different production conditions on soil organic carbon (SOC) in farmland of China, in order to provide a theoretical reference for scientific application of biochar and effective improvement of soil carbon storage in farmland.

Method Based on the published literature on the effect of biochar application on SOC content in farmland in China, this study took no biochar application as the control group and biochar application as the experimental group. Meta-analysis was used to quantitatively analyze the effects of biochar application on SOC content in farmland under different natural conditions, soil properties and farmland management measures.

Result The results showed that the application of biochar could significantly increase SOC content by 33.98% (P < 0.05) in average. The SOC was significant increased by 48.05% (P < 0.05) while the mean annual temperature was 10-15℃, and showed the highly significant (P < 0.01) difference among different mean annual temperatures. The mean annual precipitation also had a significant effect on the effect of biochar on SOC (P < 0.05). Applying biochar on loam soil could significantly increase the SOC content by 26.66% (P < 0.01) compared with other texture soils. The increase effects on SOC content was increased with the biochar pH increase, and significant increased by 49.20% (P < 0.05) in average with biochar pH > 10. Compared with continuous cropping, the crop rotation could highly significant increased SOC by 28.42% (P < 0.01) in average under biochar application. The SOC content not significant increased with the nitrogen fertilizer rate, but significant increased with the biochar application rate. In addition, the soil pH of experimental farmland type, source of biochar preparation, and C/N ratio of biochar also have different effects on the SOC content under biochar application.

Conclusion Notably, biochar application could significant increase SOC content based suitable cropping system (rotation), soil types (loam), mean annual temperature (10-15℃) and high biochar pH ( > 10) can enhance the SOC sequestration potential of farmland.