不同种植模式对土壤理化性质及微生物特征的影响

【目的】研究不同种植模式对土壤理化性质及微生物特征的影响，为湖南省湘西州农田土壤的可持续利用提供科学依据。【方法】在湘西州分别调研采集连续5年以上常规施肥条件下进行烟—稻轮作（TRT）、烟—玉米轮作（TMT）和烟—烟连作（TT） 3种种植模式土壤，测定土壤容重、孔隙度、有机碳、氮磷钾、化学计量、pH、过氧化氢酶、酸性磷酸酶、脲酶和微生物量碳氮等指标，分析种植模式对土壤理化性质和微生物特征的影响以及不同模式间的差异。【结果】种植模式对土壤孔隙度、有机碳、氮磷钾、化学计量、pH、3种酶和微生物量碳氮均有显著（P<0.05）或极显著（P<0.01）影响。不同种植模式土壤容重和毛管孔隙度均以TRT最高，通气孔隙度则以TMT最高； TRT土壤pH、有机碳、氮素和化学计量均明显高于其他模式，土壤总磷、速效磷和速效钾含量在TT中最高；土壤过氧化氢酶和脲酶活性及微生物量碳含量在TRT中最高，而酸性磷酸酶活性在TT中最高；不同种植模式灰色关联度指数排序为TRT>TMT>TT。主坐标分析结果表明，不同模式间存在明显差异，且TRT与TT间差异更明显；土壤有机碳与总氮、化学计量和微生物量碳呈显著或极显著正相关，各化学计量间呈极显著正相关；结构方程模型表明种植模式对土壤理化性质具有直接作用效应，对微生物特征具有间接作用效应，微生物特征是评价土壤质量的重要指示因子。【结论】烟—稻轮作模式土壤pH稳定，养分较充足且均衡，微生物特征最佳，有益于保持土壤肥力和质量，是一种用养结合且经济效益较高的可持续利用模式，值得在湘西地区长期推广应用。

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.