Integrated soil fertility assessment system for tobacco cultivation: A case study in Honghe prefecture

This study developed an integrated soil fertility evaluation framework for flue-cured tobacco (Nicotiana tabacum L.) cultivation by combining indicator screening, weighting, and quality assessment methods. A three-stage analytical procedure was applied to 6,349 soil samples collected from 2011 to 2021 across seven counties in the Honghe Hani and Yi Autonomous Prefecture (Honghe Prefecture). This procedure included indicator optimization based on Total Dataset and Minimum Data Set (MDS) approaches, weight determination using entropy weight (EW) and correlation coefficient methods, and fertility assessment using the Soil Basic Niche-Fitness model and Soil Fertility Index (SFI). Validation by regression analysis (R² = 0.72), Kappa consistency testing (0.458), and correlation analysis (r = 0.85) identified the MDS-EW-SFI system (MESFI) as the most suitable evaluation framework. The optimized MDS included six indicators with corresponding weights: soil pH (0.071), soil organic matter (0.085), available potassium (0.169), available boron (0.141), water-soluble chlorine (0.292), and exchangeable magnesium (0.242). Soil fertility indices (0.393-0.565) showed stable spatial patterns, with 54.72% of soils classified as good and 32.43% as medium. The average fertility levels followed the order Gejiu (0.489) > Jianshui (0.467) > Mile (0.463) > Mengzi (0.457) > Kaiyuan (0.457) > Luxi (0.448) > Shiping (0.445). Structural equation modeling showed that soil properties exerted the strongest direct positive influence on MESFI, with available potassium and boron having the highest path coefficients (0.608 and 0.558, respectively). Geographic factors, including longitude and altitude, and environmental variables indirectly increased MESFI by improving soil properties. However, they indirectly reduced MESFI through their influence on annual temperature, which negatively affected soil properties and explained 37% of the variance. These results suggest that careful selection of indicators, weighting schemes, and evaluation methods can improve soil fertility assessments in tobacco-growing regions. Future studies should further examine the natural and anthropogenic factors contributing to the spatial and temporal variabilities in soil fertility.