Effect Of Biochar Amendment On Crop Yield And Greenhouse Gases Emission

In the last couple of years,it has become a new way of increasing soil fertility and reducing greenhouse gases emission by converting treating crop straw into biochar through pyrolysis.Biochar amendment in agricultural soils could not only utilize crop straw,but also increase soil organic carbon storage and improve soil fertility.Previous studes have shown that biochar amendment could increase crop yield and decrease greenhouse gases emission.However,the change in crop productivity and greenhouse gas following biochar amendment varied across climate type,soil type,crop type,application rate,and biochar properties.In China,much more fertilizers and pest-an d herbicides are used every year.And the croplands are cultivated extensively.All these characristics in China’s agriculture might influence the response of crop yield and greenhouse gases emission to biochar amendent.In addition,most of the field studies applied biochar in a large amount(more than 20 t ha-1),and the mechanism of how biochar affect crop yield and soil greenhouse gas emissions is still unclear.Therefore,this study first conducted a meta-analysis to investigate the effects of biochar amendment on crop yields and greenhouse gases emission in China,and the key factors affecting crop yields and greenhouse gas emissions response to biochar were indetified.Secondly,a field experiment was conducted to study of the effects of different biochar amendment methods on crop yield and soil greenhouse gas emissions in two rotation systems(wheat-maize and wheat-soybean).The mechanism of biochar on crop yield and soil greenhouse gas emissions was accessed.Thirdly,the mechanism of how biochar regulates plant growth and was investigate by separating biochar into different components and then testing the effect of the different components on maize growth.The main results of this study are as follows:1.In this study,a meta-analysis was conducted to investigate the effect of biochar amendment on crop yield,soil carbon sequestration and greenhouse gas mitigation potential.The dataset was derived from field studies conducted in China’s mainland.The papers were published in either Chinese or English.This study showed that biochar soil amendment significantly increased crop yield by increased crop yield by 15.1%on average,whereas rice yield was increased by 10.4%and the grain yield of dry land crops was increased by an average of 16.4%.The changes in grain yield following biochar amendment were influenced by soil and biochar properties as well as soil management practices.With regards to experimental soils acidity and texture were important factors influencing the response of crop yield to biochar amendment.Substantially greater yield increases were observed in soil with very low pH and clayey and sandy texture.In addition to soil properties,biochar properties also influenced the response of crop yield to biochar amendment.No yield increases were observed when agricultural soils were amended with biochar produced at a high temperature(>550℃).Biochar amendment decreased nitrous oxide(N2O)emission by 13.6%in dry crop land and decreased methane(CH4)emission from paddy soil by 15.2%.Soil acidity and texture were found to be important factors that regulate the response of N2O emission to biochar amendment.In strongly acid soils,the addition of biochar had no effect on N2O emission,whereas in neutral or alkaline soils,biochar significantly decreased N2O emission.In terms of soil texture,the diminishing effects of biochar were in the order of loam>sand>clay.In loamy soils,biochar amendment decreased N2O emission by 33.9%.Nitrous oxide emission decreased significantly in soils amended with biochar under a nitrogen fertilizer application rate higher than 150 kg hm-2.In rice paddies,biochar amendment decreased N2O emission by 24.4%,which was significantly higher than the value in dry cropland soils.Soil texture and pH significantly affected the response of CH4 emission to biochar amendment.In strongly acidic or sandy soils,biochar amendment markedly decreased the emission of CH4.In soils with a sandy texture,biochar decreased CH4 emission by 25.9%.In conclusion,our study shows that biochar soil amendment can increase crop yield and decrease greenhouse gas emissions in China’s croplands.In the future,we suggest that it will be preferable to apply biochar to soils with lower fertility,such as acidic,clayey,or sandy soils,and to dry crop land rather than paddy soils.Furthermore,biochar produced at a pyrolyzing temperature lower than 550℃ would be more suitable for the amendment of agricultural soils.2.This study used the Huang huai hai agricultural area as the research object to study the effects of biochar and biochar compound fertilizer on crop yield and soil greenhouse gas emissions through field experiments.The five treatment designs are as follows:application of chemical fertilizer(control,CK);chemical fertilizer plus straw directly returning to field(CS);two chemical fertilizers plus biochar(B1,low-dose quarterly crop application;B2,high-dose one-time application)biochar);application of biochar-based fertilizer(BF),two rotation systems,maize-wheat rotation and soybean-wheat rotation,two rotation systems separated by 2 meters.The results showed that under the wheat jade rotation,B1 and BF increased by 8.4%and 11.3%,respectively,compared with the control corn.Compared with CK and CS treatment,B1 increased by 14.4%and 12.0%in wheat,respectively.Treatment increased corn root biomass,and B2 treatment increased root length,root surface,root volume,and root tip number.In soybean-wheat rotation,B1 treated soybean yield increased by 15.3%and 20.0%,respectively,compared with CK and CS treatment,and BF treated soybean yield increased by 14.8%and 19.5%,respectively,compared with CK and CS treatment.The wheat yield of B1 treatment increased by 12.1%and 13.0%.The yield of BF treated wheat increased by 11.9%and 12.8%compared with CK and CS,respectively.There was no significant difference in wheat straw biomass under each treatment.For soil greenhouse gas emissions,in the maize-wheat rotation system,the trend of CO2 emission between the treatments in the maize season is consistent,and there are multiple peaks in the whole growth period,in which the straw returning treatment has a higher emission peak and the highest cumulative CO2 emissions;The N2O emission peak appeared after topdressing and raining,and the peak of treatment and straw returning treatment was higher.The cumulative emission of N2O in B2 treatment was significantly lower than that of the control treatment,and the N2O emission coefficient was reduced by 53%compared with the control.In the wheat growing season,there was no significant difference in soil CO2 emission under different treatments.The application of biochar and carbon-based fertilizer had no effect on soil CO2,while compared with control and CS,N2O was significantly reduced under B1 and BF treatment,among which carbon-based fertilizer The lowest emissions.In the soybean-wheat rotation system,compared with straw returning,the soybean season B1 and BF treatments reduced CO2 emissions,and there was a tendency to reduce N2O emissions.The application of carbon-based fertilizers in the wheat season significantly reduced N2O emissions.3.By hot water extraction,the biochar,which is mainly composed of organic carbon in the carbon skeleton(washed biochar)and is given priority to with small molecule organic matter of the plant growth hormone(biochar extracts)separation,again through the burning method will be given priority to with nitrogen,phosphorus,potassium and other nutrients in the "quick fix" nutrient(biochar ash)separation.The effects of these components on the growth and soil properties of maize were studied.Adding different components of biochar of maize above-ground biomass and root biomass has significant effect,and the response in two different fertility soil,in high fertility soil,compared with the CK and the CF treatment,adding different components of biochar were significantly improve the ground part of the fresh weight of maize,and the BC,BA and BW under the treatment of root fresh weight was significantly higher than that of CF and BB;In low fertility soil,different components of biochar are treated differently.The abovground biomass is shown as BW>BC>BA>BB>CF and the fresh weight of root system under the treatment with different components of biochar is significantly higher than that of CK and CF.In the high-fertility soil,there was no significant difference in maize plant height between different treatments,while maize stem diameter showed that different components of biochar were significantly greater than CF and CK.The leaching solution treatment in low fertility soil was significantly higher than that in carbon skeleton treatment.The addition of different components of biochar significantly affected the root morphology of corn.Compared with the control,in high-fertility soil,the total root length and root surface area of corn were significantly increased by the treatment with the extract solution.The average diameter of the root system was increased by the original biochar and biochar extract solution,and the total root tip number treated with the extract solution was significantly higher than CK,CF and BA.Adding biochar different components to the low nutrient in the soil,corn root system response and in high fertility soil are different,in low fertility soil,compared with the CF processing,BA,BB and BC processing corn total root length and root surface area increased significantly,BA deal with total root volume is greater than the BB and CF,BA to the total number of root tip is greater than the BW and CF,all treatment had no significant effect on maize root average diameter;The increase of maize above ground biomass was significantly correlated with the biomass of root system(p<0.001),and the above ground biomass was positively correlated with root volume,surface area and number of root tips.