Different Irrigation Modes Effect On The Ecological Service Value Of Paddy Rice

Paddy field, as a kind of artificial wetland ecosystem, not only providing a lot of food products for society, but also has greater ecological service value. Ever talking about irrigation mode from two aspects of yield and water saving effect, tend to ignore the value of the other aspects of rice paddies, thereby causing loss to the resources of rice paddies. We can improve the ecological service value of rice paddies, provide a theoretical basis for selecting an irrigation mode, and provide a new Angle of view to compete several irrigation modes based on the research of the different irrigation modes ecological service value. This article considered several influence factors including providing primary products, gas conditioning, water regulation, environmental purification, formation and maintenance of soil organic matter, greenhouse gas release, Non-point source pollution and estimated the value of each factor under different irrigation models.Afforestation cost is one of important parameters in the evaluation of ecosystem service value. According to the current economic development level and price level, with the analysis of the afforestation cost composition, this article reestimated the afforestation cost in different areas and get a suitable afforestation cost of 522.86 yuan/t carbon. Compared with former afforestation cost 260.9 yuan/t carbon, it improves a lot and provides a new benchmark for estimating the value of ecological services.This article used the DNDC model for simulating paddy greenhouse gas emissions under different irrigation mode. The results showed that the rice paddy field under shallow wet irrigation produced about 80.8kg CH₄ in the growth period,and the paddy rice field under the flooding irrigation produced about 524kg CH₄ in the growth period which is 6.48 times as the former; On the other hand, paddy rice field under shallow wet irrigation produced about 3.4kgN₂O in the whole growth period, while the N₂O is relatively less in flooded rice field. So that water management has a great effect on the emission of greenhouse gases in the paddy field. In general, the greenhouse gas produced by shallow wet irrigation paddy field was less than that of flooded rice field. This article proposed a paddy field ecosystem service value system based on the domestic and foreign ecological service value, and estimated the ecosystem service value of different irrigation modes rely on the data of 2006～2010. The ecological service value of the shallow wet irrigation is about 5.799 million yuan, otherwise the same of flooding irrigation is about 5.374 million yuan. The result shows that the shallow wet irrigation gets more ecological service value than the flooding irrigation.In this paper, the preliminary estimation results of simulation show that shallow wet irrigation gets higher yield and less water using than flooding irrigation, in terms of overall ecological service value the shallow wet irrigation also gets higher than the flooding irrigation.