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Two experiments were conducted to study the effects of arbuscular mycorrhizal fungi (AMF) inoculation on the rhizosphere microenvironment of Italian Ryegrass and growth of subsequent paddy rice. First, a root box experiment was designed to calculate effects of AMF (mainly Glomus mosseae) inoculation on growth of ryegrass and changes of the rhizosphere microenvironment, including soil enzyme activities, organic acid contents, actinomycetes numbers and chemical properties. Second, through pot experiment, influences of AMF inoculation and ryegrass cultivation in winter on growth of subsequent paddy rice including yields, plant weights and tiller numbers were systematically evaluated. The results were as follows:(1) Growth of ryegrass and subsequent paddy rice on rice soil were significantly better than zhuyuan soil, mainly due to difference of background chemical properties. Moreover, changes of yields and growth of subsequent paddy rice on these two tested soils were different. In rice soil, dried biomass, tiller numbers and plant weights of early rice were all less than those of late rice, while yield of early rice was higher than that of late rice. However, differences between early rice and late rice in zhuyuan soil were opposite.(2) In root box experiment, soil alkaline phosphatase activities, actinomycetes numbers and chemical properties changed significantly among three zones (p < 0.05). Meanwhile, contents and species of soil organic acid were different between rhizosphere and non-rhizosphere soil. In rice soil, compared with non-rhizosphere soil, acetic acid contents in rhizosphere soil were higher. Besides, in zhuyuan soil, acetic acid contents in rhizosphere soil were lower, while citric acid and succinic acid contents were much higher than those in non-rhizosphere soil.(3) AMF inoculation influenced growth of ryegrass and subsequent paddy rice greatly. AMF and DSE colonization were both observed in roots of ryegrass and subsequent paddy rice, and most roots were colonized by DSE colonization.In root box experiment, dried plant biomass, total P and N contents of ryegrass, soil organic acid contents, alkaline phosphatase and invertase activities under AMF inoculation treatments were all higher than those under treatments without inoculation. Moreover, compared with treatments without inoculation, AMF inoculation increased actinomycetes numbers in rice soil but reduced actinomycetes numbers in zhuyuan soil. Besides, total colonization of roots of ryegrass positively correlated with soil alkaline phosphatase activities (p < 0.05).Similarly, plant weights, tiller numbers and dried biomass of ryegrass with AMF inoculation in pot experiments also increased. Meanwhile, AMF inoculation promoted growth of subsequent paddy rice, including yields, plant weights, tiller numbers, dried biomass of rice, and maximum width of blade and leaf area of subsequent early rice. In addition, correlation between total colonization in roots of subsequent early rice and soil total P contents was both significant (p < 0.05), indicating that total colonization might greatly influenced by soil chemical properties.(4) Compared to winter fallow treatments, ryegrass planting increased rice yields in rice soil but reduced rice yields in zhuyuan soil on the contrary. This result showed that decomposition of roots of ryegrass might release components which would promote or inhibit growth of subsequent paddy rice, which was also related to soil chemical properties.
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