Effects of different planting patterns on soil physicochemical properties and microbial characteristics

【Objective】 The effects of different planting patterns on soil physicochemical properties and microbial characteristics were researched to provide scientific basis for the sustainable utilization of farmland soil in Xiangxi Prefecture, Hunan Province.【Method】 The farmland soils of 3 planting patterns of tobacco-rice rotation (TRT), tobacco-maize rotation (TMT) and tobacco continuous cropping(TT) for more than 5 consecutive years under conventional fertilization conditions were investigated and collected in Xiangxi Prefecture, respectively. Soil bulk density, porosity, organic carbon, nitrogen, phosphorus, potassium, stoichiometry, pH, catalase, acid phosphatase, urease and microbial biomass carbon and nitrogen were measured, to analyze the effects of planting patterns on soil physicochemical properties and microbial characteristics, and the differences among different patterns.【Result】 Planting patterns had significant(P<0.05) or extremely significant (P<0.01) effect on soil porosity, organic carbon, nitrogen, phosphorus, potassium, stoichiometry, pH, 3 enzymes and microbial biomass carbon and nitrogen. The soil bulk density and capillary porosity of different patterns were the highest in TRT, and the aeration porosity was the highest in TMT. The soil pH, organic carbon, nitrogen and stoichiometry of TRT were higher than those of other patterns. The contents of total phosphorus, available phosphorus and available potassium were the highest in TT; soil catalase and urease activities and microbial biomass carbon content were the highest in TRT, while acid phosphatase activity was the highest in TT. The grey correlation degree of different patterns was TRT>TMT> TT. Principal coordinate analysis showed that there were obvious differences among different patterns, and had especially great differences between TRT and TT. Soil organic carbon had significant or extremely significant positive correlation with total nitrogen, stoichiometry, and microbial biomass carbon, and there was extremely significant positive correlation between each stoichiometry. The structural equation model showed that the planting patterns had a direct effect on soil physicochemical properties, and an indirect effect on microbial characteristics. Microbial characteristics was important indicators for evaluating soil quality.【Conclusion】 The tobacco-rice crop rotation pattern can result in stable pH, soil nutrients are sufficient and balanced, has best microbial characteristics, which is beneficial to maintain soil fertility and quality. As a sustainable utilization pattern with high economic benefits combining utilization and breeding, it is worth promoting and applying for a long time in Xiangxi region.