The transferring and management of water and nutrients, and the mechanism of productivity in rice paddy ecosystem Weijun Zhou, Kelin Wang, Kairong Wang Taoyuan Experimental Station of Agroecosystem Observation

Introduction Taoyuan Station is located in hilly area of South China, is a compositive field experimental station with function of located observation and research of agricultural ecosystem, demonstration of the model of high-efficiency utilization of resources and agricultural sustainable development. The station is subordinated to Institute of Subtropical Agriculture (IAS). In this area, it is rich in the resources of light, caloric, water and biology. The potential productivity of climate is very high, and the management of compositive agriculture is advanced too. This is a typical “valley agriculture” area and the structure of the agricultural production is unitary. Rice is a most important crop.  Its scientific aim is providing the decision-making basis and technique support for the ecological and environmental constructing and the development of high-efficiency and sustainable agriculture in central hilly area in the country by researching the important problems, and promoting the development and constructing of agro-ecology and resource management.

In rice paddy ecosystem, the researches have been focused on the following fields:  The recycle of the nutrients and the mechanism of the productivity in rice paddy ecosystem.  The transferring and management of water and optimization of the irrigation technique in rice paddy ecosystem.  The environmental response to the fertilization and its adjustment mechanism.  The ecological elements in high productivity cultivation of special rice(high quality rice, function rice, food rice).  The constitution of high productivity super-rice colony and its physiological index.  The fertility index system of high productivity and high quality rice.

1. Change of rice planting systems in rice paddy ecosystems The rice planting area have increased since 1950’s, and it decreased after 1970’s Area of middle-rice have induced since 1950’s, by the early of 1970’s it is up to the lowest. That of early and late rice have increased since 1950’s, by the early of 1970’s it is up to the largest Single cropping rice have been changed double cropping rice

2. Change trend of rice total yield near 50 years in Hunan province Less rice yield increase was observed before 1960’s, then the yield increased rapidly, by the early of 1980’s it was up to the highest The yield of middle rice have decreased since 1950’s, by the early of 1970’s it was up to the lowest, however, that of early and late rice indicated the increased trend.

3. Change trend of rice grain yield of unit area near 50 years in Hunan province The rice yield of unit area showed the increase trend. Before the early of 1960’s, middle-rice was the important planting system, so the annual yield increased slowly and then the early and late rice became the main planting system, the annual yield increased rapidly.

4. Change of fertilizer application amount near 50 years in Hunan province The amount of fertilizer application was much less before 1960’s, Since the early of 1960’s, the rapid increase of fertilizer have observed The ratio of N, P, K was inadaptable, N:P:K is 1: 0.2: 0.1

5. The relationship of between fertilizer application and total rice grain yield By the 1960’s, the less increment of rice yield was observed due to fertilizer was applied too less, from the early of 1960’s to the middle of 1980’s, the rice yield increased with increased fertilizer applied, then that was at steady state while the quantity of fertilizer was increased

6. The relationship of between rice grain yield of unit area and fertilizer application quantity The change trend of the rice yield of unit area was the same as total rice yield.

Fertilization Models with Double Cropping Rice System

7. Change of rice grain yield under fertilizer application The less yield-increase observed, no significant difference the relative no fertilization under only N application, while the rice yield was increased under N, P, K was incorporated.

8. Rice yield benefit under different fertilization model The rice yield increased under organic residue cycle, no considerably difference was observed between NPK incorporation, but based on organic residue cycle, the rice yield is the largest among all the fertilization models.

9. Rice yield benefit under different fertilization models Table 1 Rice yield benefit of different stage under different fertilization systems The rice yield-increase rate was decreased under fertilizer application while it was increased under based on organic residue cycle, no fertilizer or NPK incorporation. Residual efficiency of organic residue was very important.

The Relationship of Rice Productivity and water Irrigation Models

10.The annual variation of irrigation effect in the growth of double-crop rice (1989~1998, in Taoyuan,Hunan) The negative correlation was observed between the quantity of irrigation water and its production efficiency. More the quantity of irrigation, less its efficiency.

11. The cumulative effect of colony photosynthesis in rice booting in the different water management(in 2000) Seasonal drought influents production of double cropping rice in the region, net photosynthesis was decreased under less water

12. The relationship of plant transpiration rate and leaf porous conductance Considerably correction was found between plant transpiration rate and leaf porous conductance

Conclusion Improved the composition of fertilizer input, adjusted the ratio of NPK fertilizer Reasonably applied the fertilizer according to the law of nutrient balance Enough using the organic residue resource, let organic residue in rice paddy system recycle and utilize Adjusted and saved the rainfall resource, reasonable irrigation according to the law of rice need, heightened the use efficiency

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