Effects of Biochar Addition on CO(2) and N(2)O Emissions following Fertilizer Application to a Cultivated Grassland Soil

Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO(2) and N(2)O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO(2) emissions differed according to biochar addition and amendments. CO(2) emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO(2) emission was observed when biochar and compost were applied together during the summer. Overall N(2)O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N(2)O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N(2)O emission. Two possible mechanisms were proposed to explain the higher N(2)O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N(2)O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N(2)O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N(2)O emission when applied to soil amended with urea.