Stability of biochar in five soils: Effects from soil property

The stability of biochar in soil was an important property influencing biochar environmental effects, most studies attributed biochar stability to its intrinsic molecular structure, but few realized that biochar stability mainly depended on soil environmental factors. In this study, biochar was applied into five soils with distinct properties, and CO2 release was detected during a 28-days incubation, double-exponential model was used to fit CO2 cumulative release. Correlation analysis between basic properties of five soils and parameters of double-exponential model was conducted to screen out crucial soil factors affecting biochar stability. Argi-Udic Ferrosols soil, showing best performance among five soils on protecting biochar stability, was selected to simulate paddy-upland rotation, exploring the influence of abrupt increase of soil moisture on biochar stability. Results showed that CO2 release from biochar had negative correlation with clay and Fe content of soil (correlation coefficient was −0.68 ~ −0.61 and −0.60 ~ −0.26), whereas had positive correlation with pH and Ca content of soil (correlation coefficient was 0.29 ~ 0.69 and 0.74 ~ 0.91). Abrupt increase of moisture resulted in labile-C loss from biochar increased by 1.4 times. It implied that biochar stability was an ecological property, and acid soil, rich in clay and Fe contents and less in Ca content, was more favorable to maintain biochar stability. Results in this study were helpful to understand environmental chemistry behavior of biochar and better perform its soil environmental effects.