Influence Of Biochar Amendment On Paddy Soil Carbon Sequestration And Ghgs Emission Reduction And Rice Productivity

Biochar refers to the highly aromatic substance remaining after pyrolysis of biomass under complete or partial exclusion of oxygen. Biochar amendment is a way to tackle the problem of mitigation of climate change; also it could solve problems of sustainable development of agriculture, such as the low efficiency of nitrogen use, and large amount of greenhouse gases emissions. Biochar which was prepared out of wheat straw was applied in Red and Yellow paddy soil in Changsha, Hunan; in Red paddy soil in Jinxian, Jiangxi through field experiment, the purpose was to check the effect of biochar on soil physicial and chemical properties, rice yields, nitrogen recovery efficiency and agronomic efficiency, and the emissions of greenhouse gases.The field experiments proceeded between Late April and November in2010. The experiment sites were Jinxian in Jiangxi and Changsha in Hunan. The treatments included blank control (C0N0),20t·hm-2biochar amendment only (C1N0),40t·hm-2biochar amendment only (C2N0), nitrogen fertilizer amendment only (C0N1),20t·hm-2biochar amendment+nitrogen fertilizer (C1N1),40t·hm-2biochar amendment+nitrogen fertilizer (C2N1). The rate of nitrogen fertilizer were150kg·hm-2(TN) during Early rice growth period in the two experiment sires;240kg·hm-2(TN) in Changsha and300kg·hm-2(TN) in Jinxian during Late rice growth period. The other management measures were as same as the local’s.The test results of the study are as follows:(1) Biochar amendment could impove physical and chemical properties of the paddy soil and microbial habitats. At the rate of40t·hm-2the content of soil organic carbon increased above50%at the same rate of nitrogen fertilizer compared with control at the two experiment sites. The results also showed that the volume weight decreased, pH increased in acidulous and acidic soil with biochar weight increasing, and in the more acidic soil extent of increasing was lager. Biochar amendment also could increase microbial biomass and improve enzyme activity of the soil.(2) Influence of biochar amendment on rice yield was different due to the experiment sites and times. Early rice yield didn’t change remarkably with biochar amendment in the two experiment sites, but the biochar amendments increased the Late rice productivity by5.18%and7.95%in Red paddy soil in Jinxian with the incorporation of nitrogen, but isn’t variational remarkably in Red and Yellow paddy soil in Changsha(3) Biochar amendments also improved nitrogen recovery efficiency and agronomic efficiency, but the extent of improvement had to do with the experiments and the basic properties of soil. At the rate of20t·hm-2biochar amendment the nitrogen recovery efficiency was increased by7.21%, also the agronomic efficiency was increased by35.97%in Jinxian experiment site. The nitrogen recovery efficiency was increased by17.58%in Jinxian and20.33%in Changsha at the rate of40t·hm-2biochar amendment, also nitrogen agronomy efficiency was increased39.81%in Jinxian.(4) Biochar amendment also could affect Greenhouse gas emissions. It increased the emission of CH4significantly in the treatments without nitrogen fertilizer in the two experiment sites at the whole Late Rice growing period. The increasing trend was slow in Changsha, but the emissions of CH4were let down in Jinxian at the rate of40t·hm-2biochar amendment. At the same time there was no influence to the emissions of N2O and CO2in the whole growing period. The emission of CH4in Jinxian didn’t increase as the use of biochar, but it reduced by70.57and27.59%as the increasing of biochar amendment in Changsha with nitrogen fertilizer. It reduced the emission of N2O significantly in the treatments with nitrogen fertilizer; the emission in Jinxian was decreased by46.28%and53.74%, also it in Changsha was decreased by27.40%and50.68%. Biochar amendment didn’t affect the emission of CO2significantly.(5) On the two time scales, biochar amendment could reduce the Greenhouse Warming Potential (GWP) and the GWP of per unit of production (GHGI) in the current farm management practices. On a time scale20-year period the decreasing extent of GHGI was16.12%-33.10%in Jinxian; it was about50%in Changsha. The decreasing extent of GWP was50.80%and38.60%. On a time scale20-year period the GWP of N2O accounted for21.55-216.84%of the GWP of CH4, on a time scale100-year period the proportion was more than100%, the emission of N2O in paddy soil couldn’t be ignored. Meanwhile we could prove biochar will be a new improver to change traditional agriculture inte Low-carbon agriculture, further to ensure the healthy development of agriculture in China. At the same time biochar amendments could increase the reserves of soil carbon pool, and decrease emissions of greenhouse gases. Also it could be a promising technology of carbon sequestration and GHGs reduction under the current farm management practices.