Biochar changes thermal activation of greenhouse gas emissions in a rice–lettuce rotation microcosm experiment

Abstract

Abstract Despite numerous studies of the effects of biochar amendments on soil greenhouse gas (GHG) emissions in recent years, the intrinsic temperature sensitivity of GHG emissions in biochar-amended soils is still not clear. In order to investigate the effects of biochar on the thermal activation of GHG emissions, the GHG emissions and their activation energies (Ea) were analyzed in a rice-lettuce rotation microcosm experiment. The experiment had five treatments: control (CK), chemical fertilizers (NPK), and three biochar application rates that are equivalent to 10 Mg ha−1 biochar (BC10), 20 Mg ha−1 biochar (BC20) and 40 Mg ha−1 biochar (BC40). The study showed that biochar treatments reduced CO2 and N2O emissions by lowering their Ea compared with the NPK treatment in the rice cultivation season. The biochar amendment treatments significantly reduced N2O cumulative emissions by 55.2–72.9% compared with the NPK treatment in the lettuce cultivation season largely due to the thermally deactivated impact of soil temperature on N2O emissions. Microbial biomass carbon was increased in the lower rates of biochar amendment in both crop cultivation seasons. These findings suggest that biochar amendment of soil has the potential to decrease the positive and increase the negative Ea of GHG emissions, with the implication of mitigating GHG emissions from cropland soils that would otherwise be increased by applying chemical fertilizers in the context of rising global temperature. Production of biochar from agricultural wastes, which is a method of cleaner production, and its application to the soil shows its potential for reducing GHG emissions by changing the thermal activation of the emissions during rice–lettuce crop rotation.