Changes in Soil Properties, Yield and Trace Gas Emission from a Paddy After Biochar Amendment in Two Consecutive Rice Growing Cycles

【Objective】The effect of biochar on soil quality,rice yield and trace gas emissions in 2 consecutive rice growing cycles were investigated for providing a scientific basis for sustainable low carbon development of rice agriculture.【Method】 A field experiment was initiated in a rice farm from Chengdu Plain with 0,20 and 40 t.hm-2of biochar soil amendment with(240 kg N.hm-2) and without(0 kg N.hm-2) N fertilizer in 2010.Changes in soil fertility properties,rice yield and non-CO2greenhouse gases emission in a whole rice growing cycle with biochar amendment were monitored throughout 2010-2011.【Result】Biochar amendments significantly increased soil organic carbon,total nitrogen,pH value and decreased bulk density of soil in both rice-growing cycles,when N fertilizer was applied,but it had no changes in rice yield.Biochar effect on CH4emission varied with N status.Increase of CH4 emission was observed only under low rate of 20 t.hm-2in the first cycle.However,no increase in CH4 emission was found with N fertilization in the first cycle and even a decrease in the second cycle.With N fertilization,great decrease in N2O emission(by as high as 66% under 40 t.hm-2 of biochar amendment) was evidenced throughout the two cycles.Overall,biochar soil amendment tended to decrease the global warming potential and rice production carbon intensity from the two non-CO2 trace gases in the consecutive two rice cycles,under 40 t.hm-2 in particular.【Conclusion】Biochar soil amendment at 40 t.hm-2 could be a technical option to reach low carbon intensity and stable rice productivity in rice paddy agriculture.