Hydrophobic- and fat-dissolved rice straw-C induced equivalent amount of CO2 emission and soil net C balance

Abstract

Understanding the influences of hydrophobic- and fat-dissolved straw substrates on CO2 emission and soil net C balance is necessary for quantifying soil C storage after the straw return. The straw-driven increase in CO2 emission could dangerously strengthen climate change, and the accompanying uncertainty in soil C sequestration ascribed to the priming effect with different straw-C components application. The mechanism underlying the decomposition of soil organic carbon via the priming effect with different straw-C components amendment still remains insufficiently resolved. Here we evaluated the impact of hydrophobic- (HC) and fat-dissolved C (FC) from rice straw on priming effect using an incubation experiment, which would explain well the observed current variation in CO2 emission and soil C storage in response to straw return. Applying HC and FC to the soil, we found that the emitted CO2 from soil in HC addition treatment was higher than that in FC treatment during first two weeks, thus resulting in a higher cumulative priming effect. The increase in cumulated CO2 emission was ascribed to strong priming effect in HC treatment in the first 14 days, and higher mineralization percentage in FC treatment, separately. In the end, both straw-C addition treatments induced equivalent CO2 emission and increased soil C storage. Our findings suggested that adjusting the driver in controlling the contribution of hydrophobic- and fat-C to CO2 emission was an important strategy to mitigate climate change in response to straw return. Due to the equivalent CO2 emission, the fat-C-derived CO2 emission needs to further study in the future.