| Farmland ecosystem is an important part of terrestrial ecosystems.With the rapid advancement of urbanization and industrialization in china,heavy metals and heavy metal compounds had contaminated farmland by mining,exhaust emission,sewage irrigation and chemical fertilizer application,causing adverse effects on human health and food security.Howerer,heavy metals contamination is different from organic pollutants in soil.The heavy metal contamination couldn't be degraded by micro-organism,and persisted in soil then causing a worsening environment for a long time.It may further influence soil carbon and nitrogen cycling and increased GHGs production and emission.Biochar,as a new soil amendment,is a solid material containing high fractions of aromatic functional group and high physiochemical adsorption.Using biochar is an effective soil improvement method to enhance soil C stock mitigate greenhouse gas emission and slow down heavy metals toxicity to crops.However,it is not clear that biochar and heavy metal contamination effects on greenhouse gas emission under different multiple cropping modelsin southern China.In order to elucidate the effect of biochar amendment and cadmium on greenhouse emission form ryegrass-rice and wheat-rice multiple cropping models.A field experiment of soil column simulation in greenhouse was carried out.The main results are as fallows:1.Effect of biochar amendment and Cd-contamination on rice yield and soil greenhouse gas emissions(1)Biochar amendment significantly improved rice yield,but had no significant change was observed in Cadmium treatment.As compared to the control,biochar amendment increased rice yield by 148%and 103%following without and with Cadmium,respectively.(2)Biochar amendment significantly decreased CH4 and N2O emission,but increased CO2 emission.However,there was no significant change on CH4 and N2O emission but decreased CO2 emission significantly following Cadmium treatment.By contrast with the control,CH4 emission was sharply decreased by 72%and 60%as well as N2O emission was decreased by 25%and 34%following biochar amendment,without and with Cadmium,respectively.With single biochar amendment,CO2 emission was significantly increased by 32%compared to control,but CO2 emission was decreased by 17%and 40%in Cadmium treatment,respectively.(3)Biochar amendment increased global warming potential(GWP),but significantly decreased greenhouse gas intensity(GHGI).GWP was reduced but GHGI was significantly increased by Cadmium.With and without biochar amendment,GWP was observed a decrease by 25%and 26%following Cadmium treatment.With biochar amendment,GHGI was decreased by 55%and 62%following with and withoutCadmium,respectively..2.Effect of biochar amendment and Cadmium on greenhouse gas emission and ryegrass-rice yield under ryegrass-rice multiple croping model(1)Biochar amendment caused a signficant increase of ryegrass yield but had no significant change was observed in rice yield.Rice yield was significantly decreased by Cadmium while had no significant difference on ryegrass yield.Ryegrass biomass was significantly increased by 138%and 103%following biochar amendment,repectively,but hadno significant change in Cadmium treatment.Cadmiumtreatment decreased 43%of rice yield,but had no significant change in biochar addition whether Cd contamination or not.(2)Biochar amendment increased CH4 and CO2 emission,but decreased N2O emission.There was no significant change on CH4 emission in ryegrass growing season among the treatments.On the contrary,CH4 emission was increased by 147%and 410%with biochar amendment in rice growing season,respectively.Biochar amendment could increase CO2 emission for 16%and 9%,respectively.In rice growing season,single biochar amendment was observed on significantly improving CO2 emissionbut had no significant change on other treatments.In ryegrass season,N2O emission was sharply reduced 60%and 56%,and in rice season that was decreased 21%and 41%,respectively,following biochar addition with or without Cadmium.(3)Biochar amendment decreased global warming potential(GWP)and greenhouse gas intensity(GHGI).With and without Cadmium,GWP was decreased by 23%and 7%and GHGI was decreased by 45%and 42%,respectively,following biochar amendment under ryegrass-rice multiple croping model.3.Effect of biochar amendment and cadmium on greenhouse gas emission and wheat-rice yield under wheat-rice multiple croping model(1)Biochar amendment significantly increased wheat yield but had no significant change was observed in following rice yield.Wheat yield was improved by 31%and 18%,respectively,but was observed there was no significant change on rice yield compared to control.Cd-contamination had an adverse effect on wheat and riceyield,which was decreased by 38%and 51%,respectively.(2)Biochar amendment decreased N2O emission,but had no influenced on CH4 and CO2 emission.In wheat season,N2O emission was increased by 147%but CO2 emission was decreased by 24%following Cadmium treatment.However,N2O emission was decreased by 36%and 95%,respectively,but had no significant difference on CH4 and CO2 emission with and without Cadmium following biochar amendment.In rice growing season,with and without Cadmium,N2O emission was significantly decreased by 85%and 86%,respectively,following biochar amendment.But CO2 emission was decreased 16%in case of Cadmium treatment.(3)Biochar amendment decreased global warming potential(GWP)and greenhouse gas intensity(GHGI).With and without Cadmium,GWP was sharply decreased 68%and 67%,and GHGI was decreased 75%and 74%,respectively,following biochar amendment in whole wheat-rice multiple croping season.However,there was no significant change on GWP but increased GHGI by 76%following Cd-contaminated treatment. |
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