Investigation of greenhouse gas emissions from the soil amended with rice straw biochar

Biochar, which is a byproduct from pyrolysis of any kinds of biomass, has received attention recently for its potential to mitigate climate change if we are to apply it to agricultural soil. However, the effects of biochar application on greenhouse gas emissions are difficult to be generalized because we do not fully understand the mechanisms how biochar influences soil functions. In this study, Korean rice paddy soil was incubated for 30 d amended with biochars made from Chinese/Korean rice straw at low (300-400°C) and high (600°C) pyrolysis temperatures. The controls were prepared by amendment with the straw materials and nothing. Biochar addition significantly decreased the CO2 and CH4 evolution compared to the straw amendment. However, the FDA activity, microbial biomass, the abundance of methane related microorganisms were not changed by biochar addition. We observed an increase in the soil N2O emissions with the biochar. We attributed it to the increased microbial nitrification followed by pH increase by biochar addition. Overall data suggests that care should be taken when we apply biochar to the rice paddy soils that are acidic and heavily fertilized, because it might stimulate N2O emission through nitrification, although CO2 and CH4 are not changed or reduced.