| As the basis of human survival and development,crop production industry plays an important role that others cannot address.And population growth,environmental pressure and economic development are the main factors that influencing the sustainable development of this industry.To satisfy human survival and further development,it is very necessary to evaluate the sustainability of the crop production industry.This paper adopted emergy analysis to explore the comprehensive performance of Sichuan crop production system.Based on emergy analysis,the contribution of renewable inputs(including sunlight,wind and rain)have been identified,so as to evaluate the sustainability of the holistic system.The total emergy input of Sichuan crop production system were divided into 4 categories:(a)free renewable resource including sunlight,wind,rain and earth cycle.(b)free nonrenewable resource which is top soil loss.(c)purchased nonrenewable resources including nitrogen fertilizer,phosphate fertilizer,potash fertilizer,compound fertilizer,pesticides,plastic mulch,diesel,mechanical equipments and electricity.(d)purchased renewable resources including irrigating water,labor and seeds.Besides,the output includes rice,wheat,corn,beans,tubers,cotton,peanuts,rape seeds,sugarcane,beetroots.fruits and vegetables which are the most common crop productions.Since only focuses on one year cannot give the trends of the crop production system,the input and output data from 2003 to 2013 to was used to investigate the temporal difference of the studied system.The results from emergy based indicator shows that Sichuan crop production system is in a transition phase from traditional agriculture to modern agriculture.The main results are summarized as follow:(1)In the study period,the average annual free renewable input is 1.89×1022(sej),which mainly contributed by the rain,and it has increased 3.19%from 2003 to 2013;the average annual free nonrenewable input is 1.62×1019(sej),which all came from top soil loss;the average annual purchased nonrenewable input is 2.92×1019(sej),and it has increased 36.89%from 2003 to 2013,electricity contributed more than half of the purchased nonrenewable input,the average annual purchased renewable input is 9.98×<1021(sej),with an increasing of 3.73 during the study period.And the mainly contribution came from seed,following by the irrigating water,while the labor had the least contribution.(2)In the studied,the total emergy output increased from 1.21×1023(sej)in 2003 to 1.49×1023(sej)with a total increasing of 23.14%.The annual value is 1.33×1023(sej).And therein the annual emergy of rice is 1.30×1022(sej),with an increasing of 4.65%.(3)The emergy yield ratio(EYR)of Sichuan crop production system decreased from 3.52 to 3.41 during the study period,a total decreasing of 3.13%.The EYR of 2006 and 2007 are lower than the average value.The input which decreasing from 2003 to 2013 highly influences the emergy output,such as fertilizer,pesticides and so on.This indicates that the influence of purchased nonrenewable resources is increasing.The emergy loading ratio(ELR)of Sichuan crop production system increased from 0.85 to 1.13 during the study period,with a total increasing of 32.94%,annual increasing of 2.62%and the annual average value is 0.93.The EYR of 2006 and 2007 are lower than the average value.The input which decreasing from 2003 to 2013 highly influences the emergy output,such as fertilizer,pesticides and so on.This indicates that the influence of purchased nonrenewable resources is increasing.The ELR increased at a slower pace which reflects that this crop production system has little impact on environment.However,it still has possibility to further increase.The emergy sustainable index is also decreasing from 4,13 to 3.03 which indicating this system can keep sustainable development.The main reason came from the excessive input of purchased resources.(4)The input emergy of the free renewable resource,free nonrenewable resource,purchased nonrenewable resources and purchased renewable resources have the same influence on EYR,ELR and EIS.The free renewable resource has a significant influence on ELR and ESI;and free nonrenewable resource does not have obvious effects on the results.The purchased renewable resources has a significant influence on the three emergy indicator,especially the ESI,following by the purchased renewable resources.Finally,the following suggestions are recommended.(1)Raising farmers’ knowledge of agricultural science and technology(2)Committed to developing agriculture talent,increasing investment in agricultural science and technology(3)speeding up rural information service platform and agricultural infrastructure construction(4)Promoting agricultural mechanization production and scale production(5)proper pesticide and fertilizer application... |
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