Effects of biochar amendment on greenhouse gas emission in two paddy soils with different textures

To study the greenhouse gas (GHG) emission with biochar amendment in two or more soils with different textures, an incubation experiment was carried out with two paddy soils (developed from granite-weathered red soil (S1) and from quaternary red clay (S2)) with different textures in flooding condition. The soils were subjected to the following three biochar (derived from wheat straw) treatments: 0%, 1% and 2% of soil weight, represented by CK, LC and HC, respectively. The incubation lasted for 180 d. Biochar significantly increased CO2 emission by 5.8–9.9% in S1. Biochar can combine with soil particles and provide a suitable habitat for soil microbes in S1, which increased organic C decomposition. However, biochar had no effect on CO2 emission in S2, which was due to soil aggregate formation with biochar amendment. Furthermore, biochar addition considerably reduced CH4 emission by 19.8–28.2% and 31.7–37.1% in comparison with those in CK in S1 and S2. Increased soil pH and decreased soil NH4+–N contributed to the reduction in CH4 emission. However, due to soluble C and N within biochar, N2O emissions with biochar amendment were significantly increased by 22.8–27.5% and 36.5–42.8% compared with those in CK in S1 and S2, which mainly occurred in the first 5 d. The increase in N2O emission with biochar amendment in S2 was higher than that in S1, which can be attributed to improved soil aeration with biochar application in silt clay loam soil. The net greenhouse gas emission (NGHGE, CO2-equivalents), based on the global warming potential of which for a given time horizon (e.g., 100 years), was used to assess the climatic impacts. Due to C sequestration of biochar, biochar amendment significantly decreased the NGHGE by 5123–10,250% and 5480–10,958% in S1 and S2. This study provides a theoretical basis for the application of biochar in paddy field.