Impacts of biochar amendment and straw incorporation on soil heterotrophic respiration and desorption of soil organic carbon

While biochar amendment and straw incorporation in soil have received great attention due to the potential of carbon sequestration and improvements in soil physicochemical properties, there were limited studies addressing their impacts on soil heterotrophic respiration over a seasonal cycle. Here, we conducted a field experiment to evaluate the effects of biochar amendment and straw incorporation on the temporal variations of soil heterotrophic respiration and desorption of soil organic carbon (SOC) in the North China Plain. We measured CO2 efflux over 1-year period in the field, together with water extractable organic carbon (WEOC) and soil microbial biomass carbon (SMBC). Our study showed a significant exponential relationship (P < 0.001) between CO2 efflux and temperature, with Q(10) values in a range of 2.6-3. CO2 efflux was significantly higher in summer under straw incorporation (5.66 mu mol m(-2) s(-1)) than under biochar amendments (3.54-3.92 mu mol m(-2) s(-1)) and without amendment (3.76 mu mol m(-2) s(-1)). We found significantly lower WEOC:SOC ratio and SMBC:SOC ratio under biochar amendments than with straw incorporation and without amendment. Our study indicated that biochar amendment had a greater potential for reducing SOC desorption and CO2 efflux in the cropland of North China Plain.

Automated summary

Through a field experiment, we found that biochar amendment and straw incorporation had a seasonal variation in their effects on soil heterotrophic respiration and desorption of soil organic carbon. CO2 efflux showed a significant exponential relationship with temperature, and was significantly higher in summer under straw incorporation compared to biochar amendments and without amendment. Biochar amendment also resulted in lower ratios of water extractable organic carbon to soil organic carbon and soil microbial biomass carbon to soil organic carbon. Overall, biochar amendment had a greater potential for reducing carbon emissions and desorption in cropland in the North China Plain.