不同土壤类型养分垂直分布特征

以昆明烟区几种典型土壤类型为研究对象，运用相关性分析法探讨了不同土壤类型剖面理化性状和真菌、细菌、放线菌数量与耕作深度的关系。结果表明，紫色土、水稻土和红壤的有机质、速效氮、速效钾和真菌、细菌及放线菌数量与剖面深度呈极显著负相关关系，水稻土的交换性钙和交换性镁含量均与剖面深度呈极显著负相关关系，而紫色土和红壤呈负相关关系；三种土壤类型剖面的各养分含量及真菌、细菌、放线菌数量具有较强的表聚性特征，自上而下存在明显的递减性；从养分含量及微生物数量的递减幅度来看，紫色土耕作深度以20 cm左右为宜，红壤和水稻土耕作深度以20～30 cm为宜。生产中，若耕作深度大于30 cm，3种土壤的养分均存在下降的风险。因此，针对深耕地块，建议合理提高施肥水平。

Characteristics of Nutrient Vertical Distribution under Different Tobacco Planting Soils

The vertical physicochemical properties and fungi, bacteria, actinomycetes number under various tobacco planting soil types in Kunming tobacco areas were investigated to explore their relationship with tillage depth. The results showed that contents of organic matter, available N, available K, and number of fungi, bacteria, actinomycetes had a significantly or highly significantly negative correlation with profile depth of purple soil, paddy soil and red soil. The contents of exchangeable Ca and exchangeable Mg of paddy soil had highly significant negative correlation with profile depth, purple soil and red soil only showed negative correlation. Nutrient contents and microbial numbers in all of the three tobacco planting soils showed characteristics of strong surface accumulation, decreasing from top to bottom. Considering these nutrient and microbial number change, it is suggest that appropriate tillage depth is 20 cm purple soil, 20-30 cm for paddy soil and red soil. In production practice, nutrient contents will decline largely if the plough layer is too deep （＆gt;30 cm）. Therefore, additional fertilizers should be applied.