Depth-Resolved Assessment of Soil Fertility in the Indo-Gangetic Plains: Amhat and Bankepur, Sultanpur, with a Focus on N, P, K, and S

This study assesses soil fertility in the Dubepur district of Sultanpur, located in the Indo-Gangetic plains, to elucidate how physical and chemical soil properties influence macronutrient availability under intensive agricultural practices. Recognizing soil as a dynamic, living system that sustains plant growth, nutrient cycling, water retention, and microbial activity, the research focuses on the interactions among texture, structure, porosity, pH, organic matter, cation-exchange capacity, and macronutrients (N, P, K, S). A two-village survey (Amhat and Bankepur) involved surface soils (0–15 cm) and multi-depth profiles (0–90 cm), with comprehensive analyses of pH, EC, OC, N, P, K, S, Zn, bulk and particle density, texture, and porosity. Results reveal substantial spatial variation: Bankepur exhibits higher nutrient levels (N up to 328.8 kg/ha; P up to 14.2 kg/ha; K up to 138.0 kg/ha; S up to 13.5 ppm; Zn up to 0.88 ppm) compared to Amhat, and notable differences in pH (7.1–8.2) and soil physical attributes (bulk density 1.02–1.48 g/cm³; porosity 35.1–56.4%). Across sites, phosphorus remains deficient (P < 20 kg/ha), while nitrogen shows a broader range with potential leaching risks. The study aims to correlate texture, pH, and organic matter with nutrient availability to generate site-specific management recommendations, including precision fertilization, crop rotation, and organic amendments, to enhance productivity, minimize chemical inputs, and promote sustainable soil health.