Evaluation Of Sustainable Development Of Dingxi Farmland Ecosystem Based On Emergy Analysis

Dingxi city is located in the central part of Gansu Province, is the typical ecological fragile areas of the country for its complicated topography, dry climate, serious soil erosion and frequent natural disasters. Agriculture, especially planting industry, is the foundation of the economic development of Dingxi city, the sustainable development of agriculture is directly related to the safety of the ecological environment in Dingxi city. Farmland ecosystem is the basics of agricultural economy.The stable development of agricultural economy is determined by efficient use of resources, the rational and high yield of planting structure. So it is important to quantitatively evaluate the farmland ecosystem in Dingxi city.It is analyzed and evaluated with the theory of Emergy Analysis on farmland ecosystem in Dingxi, from three aspects that include the input and output structure, efficiency of resource utilization and sustainable development of the ecosystem, the conclusions as follows:(1)During 2001-2014, the total emergy input of Dingxi city farmland ecosystem increases year by year, which is increased from 3.67×1021sej in 2001 to 4.61×1021sej in2014,and the increascs is 25.78%. Rate of environmental resources contribution is greater but shows a decreasing trend. Auxiliary energy is mainly in total energy input, In Unrenewable industrial emergy, the maximum value of fertilizer inputs, the average proportion is the largest at 91.77%; A large proportion of human and animal in renewable organic, their accounting for 63.82% and 23.14%,and animal organic reduces every year.The system energy input density and the energy input rate all showed the increasing trend.Researches show that economic investment accounts for more and more large in the Dingxi field producing, the level of mechanization is improved continually, the dependence on the natural environment is getting lower, the sustainable development capacity of the system is declining. From the perspective of space, there is significant difference of economic development degree in Dingxi city farmland ecosystem, better social and economic development in Lintao county and Anding county.(2)During 2001-2014, the total emergy output in Dingxi city farmland ecosystem shows a increasing trend. which is increased from 1.55×1021 sej in 2001 to 2.58×1021 sejin 2014,and the increascs is 68.09%. System energy output density shows a increasing trend,the increascs is 66.96%. the main crops of emergy output have corn, tubers, crude drugs,wheat, oil crops and legume. during these years the emergy output of corn, tubers and crude drugs show a increasing trend, the corn increases by 8.38 times; wheat, oil crops, legume present a decreasing trend. Sugar beet, fruits, vegetables, melons, are smaller proportion of emergy yield. The structure of farmland ecosystem is basically stable, and the average index is 1.72. The research shows that the productivity of farmland ecosystem is increasing year by year in Dingxi. Spatially, there is significant difference of the energy value output density for different county(district), Zhangxian and Minxian higher, productivity level is relatively good; other county(district) is lower, productivity relatively low.And different crops formed their own scale advantage.(3) During 2001-2014, Resources use efficiency of Dingxi city farmland ecosystem is low, the net emergy output rate is accounting for an average of 0.53, The total output value is much lower than the auxiliary energy input, and its system has been in a state of loss because of agricultural products in the market having no competition. In space, there is significant difference of the net emergy output rate, other counties(districts) are less than1,except Zhangxian county of 1.03 is highest is greater than 1. This indicates that the he total output value is much higher than the auxiliary energy input in Zhangxian county, other counties(districts) the resources use efficiency is low, and the production condition of high input and low output is presented. The research shows that the input factors which have great influence on the farmland system are irrigation water, organic fertilizer, chemical fertilizer and agricultural machinery, the negative correlation effect are environmental resources and animal. This proofs that the barren land of Dingxi city need to keep from outside the system to add energy, should increase investment in agricultural production of organic fertilizer and agricultural mechanization, as far as possible to create favorable conditions for irrigation in the future.(4) During 2001-2014, The sustainable development index of farmland ecosystem in Dingxi city is decreasing year by year, which is less than 1, the ecosystem belongs to a consumer ecological economic system, and the sustainable development is weak.The environmental loading rate is less than 3, and the environmental pressure is relatively small,but the sustainable growth trend shows that the environmental pressure will increase continuously. In space, the county(district) system of sustainable development index is significantly.Zhangxian and Minxian are more than 1, sustainable development ability is strong; Lintao County, Anding District, Weiyuan County, Longxi County and Tongwei County are less than 1, sustainable development force is weak.The comprehensive development level of the system is the geographical distribution of the decreasing trend of "South- Central- North". Stronger coordinated development, weaker coordinated development and non coordinated development of the region’s farmland area accounted for36.10%, 49.46% and 14.44% of the city’s total farmland area.