| Rice is one of important cereal crops in China, which accounts for 1/2 of the total production in China and 1/5 of the world planting area. The microbes in the rhizosphere of rice plant play a key role in the nutrition flow between the soil and plants. Nitrogen and water are two major factors for maintaining rice yield and getting better economic return. The ecological effect of rice rhizosphere microbes under different N application levels was analyzed in paddy field in Zhejiang in 2006. Meanwhile, Study on the ecological effects of rice rhizosphere microbes under three water regimes and three nitrogen application levels using pot experiment were also conducted in 2006. The results indicated that the role and growth potential of Rice rhizosphere, affected by the management of N application, water regimes and their interaction effects. The major results from this paper were listed as followings:(1) The microbial biomass C, urease, phosphatase, catalase, dehydrogenase in rice rhizosphere during the rice growth stage were not only affected by the water regimes and the N application levels respectively, but also affected by the mutual effects of the two factors. The water regimes, in general, show a notable impact on the ecological effect of rice rhizosphere microbes in the rice tillering stage, and also in the booting stage , but the N application levels have a notable significance impact on phosphatase. In the filling stage, the fact that the rice was not only affected by the water regimes and N fertilizer , but also influenced by the interaction between the two factors which indicated that both of the N fertilizer and the water regimes have accumulated impacts on the rhizosphere effect.(2) In the booting stage, generally speaking, the water regime had strong effect on the ecological effect of rice rhizosphere microbes, but as for the phosphatase, the N fertilizer was the key factor. The order of the extent of the crossed action and the N factor didn't give the same trend when using different indexes.In the filling stage, the ecological effect of rice rhizosphere microbes mainly affected by the mutual effect of the two factors, but for the catalase ,the water regimes was the key factor, that was because catalase have relationship with soil respiration, moreover, soil moisture is the key factors of the soil respiration.(3) In the ripening stage, the dry and wet alternative controlling situation can enhance the content of the microbial biomass C, phosphatase, catalase, dehydrogenase content in rice rhizosphere notably, but the content of urease reaches the top level under the controlled water mode, all these results showed that an appropriate control of water could benefit rice growth and maintain the fertility of the soil.The dry and wet alternative controlling situation mode improved the root growth environment in the early growth period, the rice rhizosphere displayed rapid growth and spread, expanded the space of water and fertilizer absorption in the late stages of development.Under the continuous irrigation mode, soil is in reductive state, which lead the rice rhizosphere lack of oxygen, resulting in the rice rhizosphere growth declining and restrict its development.The dry and wet alternative controllong situation mode is fit for plant rice, the continuous irrigation water regime decline the indexes,Count against the ecological effect of rice rhizosphere ,of course,the effect of rice biology speciality under these different water regimes needs further study, this will afford practical basis for the rice plant in Zhejiang.(4) The water regimes was the key factor to the ecological effect of catalase , the N fertilizer has little ecological effect to dehydrogenase.(5) At different Developmental stages in Rice rhizosphere take different water regimes and N application from this result can improve the rhizosphere effect. Such as in the rice tillering stage with W1N0 treatment ; In the booting stage adopt W2N2,W3N1,W3N2; In the filling stage use W1N0,W2N1,W2N2. |
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