Emergy Analysis For Rice Ecosystem In Hunan

Rice cultivation has multifunctionality, namely, in addition to providing food, it has several ecological services those can't reflect its value through market transactions, such as flood control, gas regulation, water purification, providing habitat and so on. Evaluation results with the market profit or market comparative benefit as the goal can not reflect comprehensively the contribution of rice cultivation to people's well-being, and then they have an influence on people's choices and inputs to rice cultivation activities. Comprehensive evaluation of rice cultivation value can provide an important basis for the protection of its multifunctionality and the realization of its sustainable management for the government and society. For this purpose, this paper takes Hunan that is the largest rice producing area in China as an example and applies emergy theory to evaluate comprehensively rice cultivation.The input emergy of Hunan paddy ecosystem from 1985 to 2012 are 2.10E+22 3.37E+22 sej. Among the input emergy, the natural resources are 2.03E+21 — 2.88E+21 sej, account for 7.85 — 8.93%; and the human society are 1.90E+22 — 3.09E+22 sej, account for 91.07 — 92.15%.The output emergy of Hunan paddy ecosystem from 1985 to 2012 are 5.26E+22 6.55E+22 sej. Among the output emergy, the products are 1.84E+22 — 2.33E+22 sej; the positive externalities are 3.49E+22 — 4.35E+22 sej; and the negative externality are-7.97+20—-6.27E+20 sej.The emergy self-suifficiency ratio of Hunan paddy ecosystem from 1985 to 2012 are 0.078 — 0.099; the emergy investment ratio are 9.15 — 11.75; the emergy per area are 1.46E+16 — 1.61E+16 sej hm-2; the ratio of emergy of mechanical power and total emergy input are 4.38 — 26.42%; the environment load ratio are 0.52 — 0.97; product quality index are -20.60—-2.14 sej J-1; renewable ratio are 50.76 — 65.71%.Considering the non market output, the gains from the human economic society's 1 $ input for rice cultivation from 1985 to 2012 are 2.08 — 2.85$; the emergy sustainability index are 2.17 — 5.31; and profit rate are 90.30 — 156.91%. If not, the gains from the human economic society's 1$ input for rice cultivation from 1985 to 2012 are 0.71 — 1.00$; the emergy sustainability index are 0.78 — 1.85; and profit rate are 27.35 — 84.73%.The research results show that (1) non market services of rice cultivation contribute significantly to people's well-being, and it is much higher than the market outputs. Without considering non market services, it will underestimate the contribution of rice cultivation to people's well-being and the profit of rice panting. This will affect farmers'enthusiasm for planting rice to to a certain extent. (2) In the process of rice production in Hunan from 1985 to 2012, production activities mainly rely on the inputs from human society and highly depend on fertilizer and labor force. However, the input structure of human society is constantly changing. During this period, the use of chemical fertilizers has been reduced in recent years and has stabilized; the use of pesticides has increased, which will have a greater pressure on the environment; agro-mechanization level improve constantly and has gradually replaced the animal power; lots of labors transfer to the town. (3) Due to the smaller support capacity, the independent development degree of Hunan paddy ecosystem is weaker, but the openness degree of it is relatively high. Due to the low level of technology used and less development to local resources, it leads to a higher production cost of Hunan paddy ecosystem and the reduction of the market competitiveness of rice in Hunan. Hunan paddy ecosystem has a higher productivity, less environment pressure, high rates of return and adopts more renewable energy inputs. The system development is relatively sustainable. Therefore, firstly, the government should increase grain subsidies and targeted subsidies for non market outputs of paddy farming, and advertise the value of local natural resources and non market outputs to the farmers, thus, it hopes to affect the farmers'production decisions and encourage them to cherish and protect the natural environment. Secondly, in addition to provide technology, the government should take reasonable measures to attract young people who are working outside to plant rice. Finally, it proposes the government adjust appropriately agricultural policies and institutions on the basis of current situation.