Study on Emergy Development of Agro-ecosystem from the Perspective of Land Use Changes—Taking Dali County of Shaanxi Province as An Example

【Objective】The study was conducted to promote the high-quality development of agriculture at county level in the Yellow River basin, deepen the understanding of agricultural inputs and outputs, and improve the increasingly tight constraints on agricultural resources and the deterioration of agricultural ecological environment, and to propose optimized development ideas and countermeasures.【Method】The land use changes of Dali County, Shannxi Province were analyzed by the land use transfer matrix, then the emergy analysis (EMA) method was used and an index system was constructed, several indexes based on the emergy flow were defined and calculated, the operational characteristics of agroecosystems in 2014 and 2019 and the sustainability of development were characterized and measured, the emergy values of inputs and outputs in agro-ecosystems were quantitatively analyzed and evaluated output emergy, then the key factors that constrain the sustainable development of agro-ecosystems were identified.【Result】Compared with the base period of 2014, the emergy self-sufficiency rate of the agro-ecosystem in 2019 (year of land use planning) decreased from 18% to 13%, and the net emergy output rate decreased from 2.10 to 1.27, the sustainability index decreased from 0.90 to 0.35, the emergy value investment rate increased from 4.51 to 6.71, the environmental load rate increased from 2.33 to 3.61, the emergy value density from 1.93×1012 sej/m2 to 2.69×1012 sej/m2, and the emergy consumption per capita from 1.03×1016 sej/person to 1.41×1016 sej/person. In 2019, compared with 2014, the area of forest land, artificial land and water bodies decreased by 5.75%, 0.60% and 60.06% respectively, and the area of grassland, cultivated land and wetland increased by 19.80%, 1.44% and 21.15%, respectively.【Conclusion】Land use change is not the main factor influencing the change of agricultural output emergy, the overall development level of agriculture in Dali County is also increasing while the costs of agricultural production are also increasing, and the process of agricultural modernization is relatively rapid, which is a consumer-oriented economic system. The investment in non-renewable industrial auxiliary energy values represented by pesticides, diesel and chemical fertilizers has increased significantly, increasing the pressure on the agricultural ecological environment.