The Modes, Material And Energy Flow Analysis And Function Evaluation Of Straw Recycling

Currently, the resource constrained and environmental problem of agricultural development in China are increasingly severe. Linear agricultural mode of production made agricultural internal material and energy cycle interrupt, and material energy was lost and environmental pollution was produced. Therefore, the urgent problem of China's current agricultural sustainable development, and the significant way of agricultural low-carbon economy are to enhance the matter and energy utilization of agricultural system and form the benign agroecological cycle system. Planting is the basic production department of China's agricultural system. Crop waste-straw is an important part of recycling agriculture. It can realize low energy consumption and emission and efficient goal, and also promote the formation of sustainable modern cycle agroecosystem. Based on the ecological economy theory as the guide, combined normative analysis with positive analysis methods, and fused natural science and social science, this research analyzed straw recycling modes, proportions and benefits in Sichuan by technological and economic method through random sampling survey and field location experiment, and felt out character of material cycle and energy flow of straw recycling, moreover, the ecosystem services evaluation and life cycle assessment of straw recycling modes were made by constructing proper evaluation system. This research was also a kind of exploration, which provided a new perspective for planting and breeding waste efficient recycling and controlling the process of agricultural ecological environment. It also offered the reference to the development strategy of straw recycling in Sichuan and southwestern region. The important conclusions are as follows:(1)A new classification system, which contained fine scale circular agriculture mode, mesoscale circular agriculture mode and large-scale circular agriculture mode was put forward in this study, and the characteristics and principle of this three modes were analysed.(2) Fertilizer Transformed from straw made the maximum proportion in straw utilization which was in rice-wheat rotation area of Sichuan, and utilization of straw as feed or raw material was the second, then fermenting straw into biogas got the minimum ratio. Direct straw recycling was the main of using straw as fertilizer, of which straw mulching treatment was dominant and the utilization amount of straw in unit area was the maximum. The utilization of straw as raw material, which mainly referring to "straw-culture medium-edible fungi", obtained the highest economic benefits, whereas the benefits from the other modes were relatively balance.(3) Direct straw recycling and fungi waste recycling to field, which helps to improve nutrient uptake by crop seeds and the transfer to grain, had enhanced the nutrient use efficiency and nutrients recycling level of farmland ecosystem, especially under the fungi waste recycling mode, the nitrogen of farmland soil system had been in surplus and the nutrient utilization and conversion were higher.(4)After the fungi waste recycling to field, the farmland ecosystem system had a stronger sustainable development capability and a greater development potential, which was due to the high proportion that the organic emergy accounted from the total emergy of system, the less fertilizer emergy input. It also because the high net emergy yield ratio, the lower emergy input ratio and environmental loading ratio, and the low environmental pressure. In particular, among the fungi waste recycling modes, FR2 was the optimum mode for sustainable circulation.(5) The non-market service values of farmland ecosystem under different straw recycling modes were significantly higher than that of market value. Compared with conventional cropping, the total service values that got from direct straw recycling and fungi waste recycling were both higher. Furthermore, there was large environment purification capacity and soil quality improvement function under direct straw recycling mode and fungi waste recycling mode, especially the value of waste treatment of fungi waste recycling mode was much higher than thant of crop production.(6) Farming systems of the three typical straw utilization modes was the main links that caused potential climate warming, environment acidification, eutrophication and soil toxicity, of which the potential environment acidification and eutrophication were mainly caused by straw abandoned or burned and nitrogen fertilizer excessive used, whereas the key factors caused the potential soil toxins were the excessive using of pesticide and fertilizer. Compared with conventional cropping, it was more conducive for direct straw recycling mode and "rice-(straw)-edible fungi-(fungi waste)-wheat" straw recycling mode to energy conservation and emission reduction, climate warming alleviation, and environmental impact potential decrease.(7) Six policy suggestions had been put forward, which was showed as below:to strengthen the construction on regulation and policy system and evaluation index system; reasonably planning and optimizing the circular agriculture industry structure and layout; To promote the development, integrated innovation and demonstration of planting and breeding industry waste(such as straw etc. recycling technologies, and make great efforts to improve technological achievement transformation; to innovative market operation mechanism and speed up the industrialization development and utilization of straw; to improve grass-roots technology extension workers'and peasants'scientific and cultural quality.