| Animal husbandry has significant influnce on most of environmental problems that human beings are facing to.Feed crop production is one of the sources of environmental pollution in animal husbandry.Alfalfa,as one of the important feed crops in animal husbandry development,brings about environmental problems that can not be ignored.In this study,four different alfalfa planting modes in Gansu Province were taken as the research object,and life cycle assessment method was used to evaluate the environmental impacts and main influencing stages and pollutants of four planting modes:spreading bottom fertilizer-no irrigation,spreading fertilizer and no irrigation,spreading fertilizer and river irrigation,spreading fertilizer and well water irrigation.Corresponding improvement measures were put forward for different planting modes,and alfalfa planting in China was also studied.The results show that:?1?The potential values of global warming,acidification,eutrophication,energy consumption,land use and water resources consumption for producing 1 kg dry matter of alfalfa non-fertilization and non-irrigation planting mode were as follows:66.275 gCO2,1.599 gSO2,0.354 gPO43-,0.660 MJ,1.485 m2,6.390×10-55 m3.The main impacts of global warming,acidification and eutrophication are nitrogen fertilizer field emissions,nitrogen fertilizer production and residue emissions,while the main contribution of energy consumption is nitrogen fertilizer production and agricultural machinery use;CO2 is the main pollutant of global warming,accounting for 70.2%of the total potential value,and NH3 is the main pollutant of acidification and eutrophication.?2?The potential values of global warming,acidification,eutrophication,energy consumption,land use and water resources consumption for producing 1 kg dry matter of alfalfa under spreading fertilizer and non-irrigation planting mode were as follows:113.560 g CO2,3.448 gSO2,0.856 gPO43-,1.105 MJ,0.947 m2,7.10×10-5 m3.The main influencing factors and pollutants are the same as the only spreading bottom fertilizer-no irrigation planting pattern..?3?The potential values of global warming,acidification,eutrophication,energy consumption,land use and water resources consumption for producing 1 kg dry matter of alfalfa under spreading fertilizer and river irrigation planting mode were as follows:136.372 g CO2,3.634 gSO2,0.918 gPO43-,1.431 MJ,0.864 m2,0.670 m3.The main influence links and pollutants are the same as the first two planting patterns.?4?The potential values of global warming,acidification,eutrophication,energy consumption,land use and water resources consumption for producing 1 kg dry matter of alfalfa under spreading fertilizer and well irrigation planting mode were as follows:353.884 g CO2,4.269 gSO2,0.735 gPO43-,3.779 MJ,0.706 m2,0.454 m3.Irrigation is the main contributing link of global warming and acidification,and the main contributing link of eutrophication is nitrogen fertilizer field discharge and residue discharge.Irrigation is the main contributing link of energy and water resources consumption.The main pollutant sources of global warming,acidification and eutrophication are the same as the first three planting modes.?5?By moderately reducing the amount of nitrogen application and irrigation,the resource consumption and environmental impact of Alfalfa per unit of production can be reduced if the yield is not reduced and other additional consumables are not increased.However,if the yield is reduced,the environmental problems such as global warming may be improved,but the land occupation may be increased.In this study,the scheme of reducing nitrogen fertilizer application under the spreading fertilization and non-irrigation mode reduces the output,reduces global warming,acidification,eutrophication and energy consumption,but increases land occupation and water resource consumption;However,the optimum schemes of spreading fertilization and river irrigation mode 2 and spreading fertilization and well irrigation mode 1 have been improved in different degrees due to the moderate reduction of nitrogen application and irrigation amount,but no reduction of yield and no increase of additional consumables. |
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