| In the process of agricultural production,continuous cropping is carried out in some areas in pursuit of agricultural benefits,which leads to continuous cropping obstacles and is not conducive to soil health and food security.Crop rotation can alleviate many soil problems caused by continuous cropping.In order to investigate the differences of soil physicochemical properties,microbial community characteristics and carbon（C）,nitrogen（N）and phosphorus（P）invertase activities of four main rice cropping systems in south China,and analyze the functional potential of soil microbial and enzyme activities of rice rotation system.In this study,soil physical and chemical properties,enzyme activities and microbial community structure characteristics of rice-rice rotation,tobacco-rice rotation,rice-rape and rice-rice-rape systems were analyzed based on long-term location experiments,which provided partial reference for rational rice rotation and soil fertility maintenance in southern rice region.The main results are as follows:Compared with rice-rice rotation,the three types of paddy-upland rotation significantly improved surface soil porosity,decreased soil bulk density,improved soil aggregate composition,and significantly increased the contents of total nitrogen,available P,total K and organic matter in paddy soil.The contents of total N,total P and available P in tobacco-rice rotation were 32.4%,32.4%and 219.7%higher than those in rice-rice rotation,respectively.However,the amount of available P in tobacco-rice rotation was 0.87g kg-1in the 20–40 cm soil layer.The contents of water-stable macroaggregates,total k and organic matter in rice-rape cropping were the highest,which were increased by 12.8%,10.2%and68.64%compared with rice-rape cropping,respectively.The contents of nitrate N and ammonium N in rice-rice-rape farming were 1.61mg kg-1and 1.57mg kg-1,respectively,and the contents of total N,total P,available P and organic matter remained high in rice-rice-rape farming.Compared with rice-rice rotation,the soil bacterialɑ-diversity in the 20–40 cm soil layer was significantly increased in the three types of paddy and drought rotation,and the Chao1 index and ACE index in the 0–20 cm soil layer were significantly increased in rice-rape rotation.Rice-rice-rape cropping significantly increased the Chao1 index,ACE index and Shannon index of soil fungi in 20–40 cm soil layer.At the same time,the levels of phylum and phylum of bacteria and fungi in soil were significantly increased and soil microbial community structure was improved.In particular,rice-rice-rape rotation significantly improved the Chloroflexi,Bacteroidetes,Mortierella,Fusicolla,Fusarium,Psilocybein in soil,Rozellomycota,Zoopagomycota in the 0–20 cm soil layer.Compared with the other three models,the improvement effect of soil microbial population diversity and abundance was the most obvious.The soil enzyme activities and microbial biomass C and N contents were increased in paddy-upland rotation,and rice-rice-rape cropping was the most beneficial to improve the functional potential of soil microbial and enzyme activities.Compared with rice-rice rotation,soil enzyme activity ofβ-D-cellobiosidase,α-1,4-glucosidase,β-1,4-glucosidase,β-1,4-xylosidase and leucine amino peptidase increased by 52.6%,76.2%,76.2%,73.3%,and 47.0%in rice-rice-rape cropping.Meanwhile,compared with rice-rice rotation,the content of microbial biomass C and N in rice-rice-rape increased by 137.3%–690.3%and51.2%–69.8%,respectively.The activities of N-Acetyl-glucosaminidase and acid phosphatase in tobacco-rice rotation increased by 22.1%–35.7%and 30.3%–38.2%,respectively.The activity of leucine amino peptidase in rice-rape soil increased by 129.1%.In conclusion,compared with rice-rice rotation,long-term rice-rape,rice-rice-rape and tobacco-rice rotation could improve soil physical and chemical properties and enhance soil microbial biomass and enzyme activity potential.Among them,rice-rice-rape farming significantly improved soil physical structure,increased soil nutrient retention potential and availability,and increased the activities ofβ-D-cellobiosidase,α-1,4-glucosidase,β-1,4-glucosidase,β-1,4-xylo-glucosidase and leucine amino peptidase and the contents of microbial biomass C and N in soil and rhizosphere soil.The diversity structure and abundance of soil microbial population were improved.Therefore,the rice-rice-rape system was of great significance for improving soil structure,maintaining fertility and productivity of paddy fields in the double cropping rice region of south China,and it was a paddy field rotation model worth promoting. |
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