The Life Cycle Resource And Environmental Effects Of The Shift From Traditional Arable Farming To Grassland Agriculture

With the urbanization of China and the continuous improvement of people's living standards,the dietary structure of residents is also changing:the decline in food consumption and the increase in consumption of animal food,thus promoting the rapid development of the aquaculture industry and widening the gap in the demand for fodder grains,a new food crisis has emerged.In addition,the problems of non-point source pollution and soil nutrient imbalance and degradation caused by traditional agricultural production methods have seriously threatened the productivity and stability of agro-ecosystem,and the traditional farming itself is also facing a serious crisis.In order to solve the double crisis of traditional agriculture and find the way out of food security in our country,we must reconstruct the traditional farming-based agro-ecosystem.With the increasingly serious pollution of traditional agriculture in China and the significant changes in the dietary structure of residents,the traditional agricultural structure can not meet the needs of China's social and economic development.In 2015,the first central document proposed to speed up the development of grass husbandry,support silage corn and alfalfa forage planting,adjust the planting structure and aquaculture structure,promote China's agriculture from traditional farming to grassland agriculture gradually.Although grassland agriculture is the strategic choice of agricultural adjustment in China,there is little research on the resource and environment effects brought by this structural adjustment,especially on the basis of life cycle assessment.It is difficult to provide effective theoretical support for the path of agricultural structure adjustment and the design of grassland agricultural development mode in China.Based on the theory of human-land relationship,using the method of life cycle assessment?LCA?and using eFootprint software system,this paper takes Tongwei County which located in the Loess Plateau as the research area,aiming at the traditional crop?corn,wheat?planting system,and forage crops?silage corn,Alfalfa and oat?planting system and breeding?beef cattle?system respectively set up the life cycle inventory,analyzed the material and energy flow of the production life cycle of the three systems,and quantitatively identified the resource and environment effects of each system running process.On this basis,the changes of resource consumption and environmental impact caused by the change of planting structure were calculated through the change of planting area from 2015 to 2018,and then the resource and environment effects of the change of planting structure were analyzed.In the aspect of culture system,the environmental impact of the whole life cycle of 1 functional unit beef production was calculated,and the cumulative contribution of each stage was analyzed,and the key influencing stages and substances were identified.Studies show that the change of planting structure arising from the implementation of grassland agriculture can reduce the negative impact on the environment.Traditional crops usually adopt the production mode of high input and high return where a large number of agricultural capital invested in the process of planting such as fertilizer,pesticides and so on,has a great negative influence on the environment.while in the planting process of forage crops,the investment of agricultural capital involved is relatively less,and what is more important is that all the outputs can be used directly or indirectly as animal feed,which effectively simplifies,even skips over the process of waste disposal.As a result,the energy and resource consumption and environmental impact are significantly reduced.However,the increase in the scale of cattle breeding has offset the reduced environmental impact brought by the changes of planting structure and the impact on the regional environment has been further aggravated.It is of great necessity and effectiveness to energetically look for the breakthrough in the reduction of emission from the aspect of the key pollution stages and substances in the life cycle of agricultural system.Substituting partial chemical fertilizers with organic ones,expanding the resource and reducing the loss of water,and cutting down the amount of CH₄ emissions generated in the process of the fermentation of the intestines of cattle can reduce the negative environmental impact on the agricultural system and promote its sustainable development in China.