| Global warming and ecological environment deterioration caused mainly by the increase of greenhouse gas concentrations have become major challenges in the survival and development of human society.How to improve the sustainable development of intensive agricultural production and improve the efficiency of the utilization of agricultural ecosystem resources is the focus of international community.The farmland in the North China Plain which is an important source of global greenhouse gas emissions has great potential for emission mitigation.Hence,how to accurately estimate and effectively reduce soil greenhouse gas(CH4,N2O,etc.)emissions from farmland in the North China Plain is particularly important for the study of global change.Due to the large amount fertilization of the traditional rotation mode in agricultural production activities in North China Plain,an experiment was conducted by setting different wheat-maize rotation mode and other modes based on biological nitrogen fixation of legumes of soybean.We used static box-gas chromatography to measure the emission of soil greenhouse gases(CH4 and N2O)and analyzed the changes of crop yield under different rotation modes.In order to provide data support and scientific basis for the establishment of sustainable agriculture with low or no nitrogen input,the effects of different rotation patterns on greenhouse gas emission and crop productivity of farmland soil in North China Plain were examined,and the economic benefits and application prospects of different rotation modes were also compared and analyzed.The main findings of the study are as follows:1.Rotation mode and nitrogen fertilizer application were the two main factors affecting soil N2O emission.The cumulative emission of N2O for conventional maize-wheat rotation mode with the normal fertilization(WM330)was the highest which was 1708.22 mg m-2,and soybean related rotation could significantly reduced the fertilization of soil N2O emission.For instance,the cumulative emissions under soybean-wheat rotation(WS200)and soybean-wheat-maize rotation(WSM265)with normal fertilization were 1271.26 and 1398.21 mg m-2,respectively.However,the condition of soybean related rotation with non-fertilization enhanced soil N2O emission which was about 10%higher than the N2O emission under maize-wheat rotation mode without fertilization(WM0).2.CH4 emission fluxes showed a large variety with seasonal and rotation altogether,but the trend of CH4 emission flux between these treatments was basically the same.Furthermore,the cumulative emissions under WMO,WM330,soybean-wheat rotation mode without fertilization(WS0),soybean-wheat rotation mode with half normal fertilization(WS100),WS200,soybean-wheat-maize rotation without fertilization(WSM0)and WSM265 were-0.01 g m-2,0.03 g m-2,0.00 g m-2,-0.01 g m-2,-0.09 g m-2,-0.06 g m-2 and-0.05 g m-2.The wheat-maize rotation with regular fertilization showed obvious CH4 emission,but the other treatments showed CH4 absorption,indicating that the soil of the farmland ecosystem in the area showed CH4 sink.3.There were significant differences in global warming potential between different treatments.The application of nitrogen fertilizer significantly increased the global warming potential caused by CH4 and N2O emissions.The global warming potential caused by the wheat-maize rotation(WM330)with normal fertilization was the highest,which was 510.03 kg CO2 hm-2.The soybean related rotation was able to significantly reduce the global warming potential caused by CH4 and N2O emissions.4.Fertilization had significantly increased the economic yield of soybeans,corn and wheat,above-ground biomass,and 1000-grain weight.Whether under the condition of fertilization or non-fertilization,the yield of maize for the wheat-maize rotation had a decreased trend in the third growth season compared to the first growth season.For the soybean related rotation mode(WSM and WS),the yield of maize or soybeans in the third growth season did not show a reduction or showed an even increased production trend.5.The final economic benefits accumulated over three crop growing seasons among different rotations patterns had become more pronounced.The economic benefits under WMO and WMS0 rotation modes were the lowest which were about 22 thousand yuan and 28 thousand yuan,respectively.The economic benefits under WS200 and WSM265 rotation modes were the highest which were 45 thousand and 46 thousand yuan,respectively.And the economic benefits under WM330 and WS100 rotation modes were at the medium level.In conclusion,the soybean related rotation modes under the condition of fertilization could significantly reduce greenhouse gas emissions,maintain crop yield or biomass,and improve overall economic benefits compared to conventional maize-wheat rotation mode.Hence,the soybean related rotation modes are ecological sustainability rotation systems. |
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