Impacts Of Biochar And Straw Application On Soil Organic Carbon And Nitrogen Transformation

The straw production in our country is most in the world. The improper handing on straw was leading to waste the resources and pollute the environment. Applying the straw directly or preparing to biochar then applying into field were important measures of soil carbon sequestration. Especially, It was believed that biochar in terms of carbon sequestration has the key effect. For exploring the effects of biochar and straw application on soil carbon and nitrogen constitution and transformation, An incubation experiment continued for 200 days which was in constant temperature and humidity condition was conducted to study the characteristic of the release of carbon dioxide,the changes in kinds of organic carbon(total organic carbon, microbial biomass carbon, highly active organic carbon) and nitrogen-containing compound(total nitrogen, microbial biomass nitrogen, nitrate nitrogen, ammonium nitrogen, free amino acid) in two different soils by applying inorganic nitrogen, biochar or straw only, or biochar plus straw. The main conclusions are as follows:(1) Exploring the effects of biochar and straw application on soil organic carbon transformation. Applying straw in soils would imprve the cumulative releasing carbon dioxide amount and the releasing carbon dioxide rate of soil. On the contrary, the cumulative releasing carbon dioxide amount and the releasing carbon dioxide rate of soil was lower after applying high level biochar(4%) in soils. Biochar promoted the straw mineralization and resulted in the interaction effect between biochar and straw on soil organic carbon was negative. It reflected biocatalysis effect of biochar in soils.The application of straw or biochar only increased the content of soil organic carbon and highly active organic carbon. The application of straw increased soil microbial biomass carbon(MBC) greatly, while biochar had less impact on MBC. The application of straw and biochar also increased soil microbial biomass carbon and highly active organic carbon, but the interaction effect was depended on the incubation time or agrotype. The interaction effect between high level biochar and straw(4%) on soils microbial biomass carbon at 80 th day was negative, while between low level biochar and straw(2%) was positive.(2) Exploring the effects of biochar and straw application on soil nitrogen transformation. The application of straw increased soil total nitrogen, microbial biomass nitrogen and free amino acid, decresed soil ammonium nitrogen and nitrate nitrogen. The application of biochar increased soil total nitrogen and free amino acid, while had less impact on MBN. The effects of biochar on soil ammonium nitrogen and nitrate nitrogen was depended on the incubation time or application rate of biochar and straw. The application of high level biochar(4%) decreased soil nitrate nitrogen; the application of low level biochar(2%) increased dark loessial soil nitrate nitrogen during 21d-70 d, while decreasing loess soil nitrate nitrogen. The application of straw and biochar increased soil total nitrogen, nitrate nitrogen and ammonium nitrogen, and the interaction effect was positive. The application of straw and biochar also increased soil microbial biomass nitrogen, but the interaction effect was depended on the incubation time or agrotype. The interaction effect between high level biochar and straw(4%) on dark loessial soil microbial biomass nitrogen at 20 th day was positive, while at 80 th day was negative.(3) Exploring the effects of inorganic nitrogen source、biochar and straw application on soil organic carbon transformation.The releasing carbon dioxide rate of soil was higher after applying inorganic nitrogen source in soils, but it had timeliness. The responses of two experimental soils cumulative releasing carbon dioxide amount, organic carbon and high active organic carbon to inorganic nitrogen source were different. The application of inorganic nitrogen source increased dark loessial soil organic carbon, but there was no influence on loess soil organic carbon. The application of inorganic nitrogen source increased soil microbial biomass carbon.