| Biochar is a highly aromatic substance remaining after pyrolysis of biomass such as crop-stalk or wood under complete or partial exclusion of oxygen.Biochar soil amendment not only improves soil quality and crop productivity but also decreases greenhouse gas emissions.How these biochar effects is highly variable,which proved to be dependent on soil types,climatic conditions and biochar properties.This study was conducted in a paddy field in Taihu lake region.Our objective was to investigate the effect of direct crop straw return and the application of biochar from crop straw through pyrolysis on soil properties,crop growth and greenhouse gas emissions.Four treatment were included:the conventional control with any organic amendments(CK),straw return(SR)and wheat straw biochar(WBC)and rice straw biochar(RBC)amendment.All crop straw were returned to the field after harvest.The biochar was applied at an rate of 20 t ha-1,Each treatment was repeated for three times.In this study,a sub-factor of N fertilization was also introduced to investigate the interaction effect of biochar with N fertilization.The main research results were as follows:?Compared with the traditional fertilizer management practice without any organic amendment(CK),the direct return of crop and its biochar did not affect the 1000-seed weight and the numbers of seeds per spike;however,biochar increased rice yield and aboveground biomass production by increasing the pant tillers and their mass.Nitrogen fertilization had no effect on the 1000-seed weight and the numbers of seeds per spike,but significantly increased rice yield and the above ground biomass.With nitrogen fertilizer or no nitrogen fertilizer,relative to the conventional,contrast straw returned handle has no significant factor to influence the yield and its composition.In the presence of N fertilization,RBC increased the yield of above ground biomass and grains of rice,whereas WBC only increased the yield of above ground biomass.?The direct crop straw return and application of crop straw biochar changed most of the soil properties significantly.Compared to the conventional control(CK),biochar amendment increased the topsoil concentration of soil organic carbon,available potassium and decreased bulk density,while no effects was observed on available phosphorous and soil pH.Nitrogen fertilization had no effects on these soil fertility ralted properties.In the absence of N fertilizer,crop straw return significantly increased the topsoil nitrate contents compared with other treatments.?The effects of biochar amendment on greenhouse gas emissions was dependent on the gas species.Straw return significantly promoted the production and emission of CH4 and CO2 under either N fertilized or no N fertilized treatment.However,biochar amendment greatly reduced CH4 and N2O emission.Compared with the conventional practice(CK),the organics amendment(straw return and biochar amendment)decreased N2O emission.Consequently,biochar amendments decreased the overall global warming potential(GWP)and greenhouse gas emission intensity(GHGI).In conclusion,the direct return of crop straw return and biochar amendment altered some soil properties,crop yield and greenhouse gas emission compared with conventional fertilizer management.The results showed that the contribution of crop straw return to soil fertility and crop productivity improvement is very limited although it is still a key way of crop straw management currently and motivated by the government.Crop return would also increase greenhouse gas emission,especially for CH4.In comparison,the pyrolysis of crop straw and biochar amendment could greatly improve soil fertility,increase crop yield and decrease greenhouse gas emission. |
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