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Abstract Biochar application to cropland has been recommended as a strategy to reduce increasing atmospheric 2 concentrations and mitigate climate change. However, the direction and magnitude of responses of greenhouse gas (GHG) fluxes to biochar application to cropland remain unclear. Our meta‐analysis of 296 observations across 61 studies for the first time quantitatively estimated the effects of biochar amendment on fluxes of three s 2 , N 2 O, and 4 . The results showed that biochar application led to a significant change in soil s emissions: in general, 19% for 2 , −16% for N 2 O ( P < 0.05), but no pronounced change in 4 emissions; in paddy, −5% for 2 , −20% for N 2 O, but +19% for 4 ( P < 0.05); in upland, −18% for N 2 O, +12% for 2 , and high uncertainty for 4 . The responses of soil fluxes to biochar application were regulated mainly by experiment length, biochar application rate, biochar properties, providing a new perspective for more comprehensive understanding on biochar. The biochar derived from husk was recommended to apply to cropland with an application rate of 20–30 t·ha −1 .
Song et al. (Mon,) studied this question.