Spatial Variations and Quality Evaluation of Soil Physicochemical Properties in Typical Tobacco-growing Areas of Yuxi, Yunnan

Purpose To identify the differences in soil physicochemical properties in typical tobacco-growing areas of Yuxi, Yunnan Province, and to establish an efficient and concise soil quality evaluation indicator system for scientifically assessing the health status of tobacco fields.

Methods A total of 75 surface soil samples were collected from five main tobacco-producing counties in Yuxi: Chengjiang, Xinping, Eshan, Huaning and Jiangchuan. Fifteen physicochemical indicators were measured. The minimum data set (MDS) was screened using principal component analysis and Pearson correlation analysis. The soil health index was calculated using the area-weighted method to quantitatively evaluate soil quality across regions.

Results Soils in the study area were predominantly loam to clay loam, and there was no significant difference in sand, clay and silt-clay ratio, but there were significant differences in silt content, field water capacity, total nitrogen, total phosphorus, exchangeable calcium, exchangeable magnesium, and pH among different tobacco-growing areas (P<0.05). Notably, Eshan had significantly higher silt content than other tobacco-growing areas except Xinping, while Xinping exhibited the lowest total nitrogen and exchangeable calcium levels. Six key indicators, including organic matter, clay, silt, exchangeable calcium, exchangeable magnesium, and total potassium, were selected to construct the MDS. Soil health index values calculated from the MDS showed no significant difference among tobacco-growing areas (P>0.05), with Huaning scoring the highest (0.599) and Xinping the lowest (0.441), indicating a moderate level of overall soil health. The soil health index constructed based on the MDS was extremely significantly positively correlated with that based on the total data set (TDS) (P<0.001), indicating that the MDS could be used as a substitute for the TDS to assess soil quality in tobacco-growing areas of Yuxi.

Conclusion While the overall spatial variability of soil physicochemical properties in typical tobacco-growing areas of Yuxi is low, some indicators exhibit significant differences. The constructed MDS-based indicator system is representative and practical for rapid assessment of tobacco field soil health at the regional scale, providing important guidance for precision fertilization and sustainable tobacco production.