| Climate warming,which is caused by the increasing emissions of greenhouse gas,has become the focus of global attention in recent years.As an important source of greenhouse gas emissions,researchers has been paid more and more attention to agriculture at home and abroad.Global greenhouse gas emissions from agriculture and forestry in 2010 accounted for 24% of the total emissions of human activities.Therefore,it has become one of the hot spots in the study of climate change that to use effective measures to reduce greenhouse gas emissions in the process of agricultural production.In order to compare the differences in carbon sequestration and greenhouse gas mitigation after straw and straw–derived biochar amendment,a field experiment was conducted with simultaneous measurement of carbon dioxide(CO2),methane(CH4)and nitrous oxide(N2O)emissions,crop yield,soil organic carbon(SOC)content and net global warming potential(NGWP)in a wheat-maize rotation cropping system.We further analyzed the energy consume in each step of wheat production process to calculate the carbon footprint.Five treatments were included: control(no straw incorporation,no straw–derived biochar amendment and no fertilization,CK),fertilization(no straw incorporation and no straw–derived biochar amendment,F),straw with fertilization(wheat straw incorporated at 8 t·hm-2,FS),low straw–derived biochar(8 t·hm-2)with fertilization(FBlow)and high straw–derived biochar(16 t·hm-2)with fertilization(FBhigh).The purpose of the study is to provide a scientific basis for reducing emissions and increasing agricultural production in northern china by revealing the characteristics of greenhouse gas emission,soil aggregate composition and soil carbon chemistry in the wheat-maize rotation system after the wheat straw and it's biochar applied.(1)Under the irrigation condition,compared with the F reatment,the content of soil organic carbon(SOC)increased by 33.7%~79.6% under straw or biochar applications,and the content of soil total nitrogen(TN)increased by 24.1% under the FBhigh treatment.The Percentage of soil macro–aggregates(>2 mm)increased by 78.3% under the FBhigh treatment,but the FS or FBlow had no significant effects on the composition of soil aggregates.The straw and biochar applications significantly increased the aggregate–associated SOC content by 32.0%–182.9% in macro–aggregates(>2 mm).The concentrations of aggregate–associated HAC increased by increased by 14%,12.1% and 24.2% in soil micro-aggregates(<0.25 mm)under FS,FBlow,FBhigh treatment,respectively.The concentrations of aggregate–associated LAC increased by increased by 56.4% and 73.3% in macro–aggregates(>2 mm)under FBlow and FBhigh treatment,respectively.(2)Under rainfed condition,wheat yield increased by 30.9%,66.3% and 36.6% under FS,FBlow and FBhigh treatment,as compared to the F treatment,respectively.However,maize yield decreased by 14.1% and 24.6% under FS and FBhigh treatment as compared to the F treatment,respectively.However,there was no significant difference between FBlow and F treatment.Annual CO2 emission increased by 60.2% under FS treatment,but decreased by 14.4% under FBhigh treatment as compared to the F treatment,respectively.Annual N2 O emission decreased by 27.6% and 38.7% under FBlow and FBhigh treatment as compared to the F treatment,respectively.However,no significant difference was observed under straw application.Overall,the NGWP decreased by 24.1 and 58.4 t·hm-2 under FBlow and FBhigh treatment as compared to the F treatment,respectively.And the NGHGI decreased by 1.8 and 5.1 t·t-1 under FBlow and FBhigh treatment as compared to the F treatment,respectively.(3)Carbon footprint was used to analyze the carbon consumption of wheat growing season in 2013-2014.Results show that the carbon footprint in wheat production is mainly the net primary production(NPP)and energy consume relevant to fertilizer.As compared to the results under F treatment,net primary productivity under FS,FBlow and FBhigh treatments increased 30.9%,63.0% and 27.8%,respectively;seasonal amount of soil CO2 emissions under FS treatment increased 68.7%,but no significant difference were observed under biochar amendment.Cumulative N2 O emissions was reduced by 33.9%,23.8% and 58.6% under FS,FBlow and NBhigh treatment,respectively;the carbon footprint under FS,NBlow and NBhigh treatments increased 26.0% but reduced 198.0% and 112.9%,respectively.We conclude that amendment of wheat straw biochar reduced carbon footprint in the studied agricultural ecosystems.These results indicate that the greenhouse gas emission rate and total emissions in the farmland decreased and the soil organic carbon content and aggregate stability increased to a certain extent by adding biochar in the wheat-maize rotation system,farmland.Applying 8 t·hm-2 biochar could significantly increase crop yield.However,it can be concluded that the application of 16 t·hm-2 biochar can be used as a good measure to increase production and reduce the net global warming potential by considering the economic and environmental effects of straw / biochar application. |
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