Variability and Distribution of Macronutrients in Calcareous Soils of Vaishali District, Bihar, India

Abstract

Soil fertility assessment is crucial for sustainable agricultural productivity, particularly in calcareous soils that often exhibit nutrient imbalances. The present study was undertaken to evaluate the spatial distribution and status of major soil fertility parameters and macronutrients in the calcareous soils of Vaishali district, Bihar. A total of 139 geo-referenced surface soil samples (0–15 cm) were collected across different blocks using GPS-based random sampling. Standard analytical procedures were employed to determine soil pH, electrical conductivity (EC), organic carbon (OC), and available macronutrients including nitrogen (N), phosphorus (P), potassium (K), and sulphur (S). Descriptive statistics and correlation analysis were performed to understand nutrient variability and inter-relationships among soil properties. Results revealed that soil pH varied from 7.02 to 8.36, indicating near-neutral to moderately alkaline conditions, while EC values (0.11–2.48 dS m⁻¹) confirmed predominantly non-saline soils. Organic carbon ranged from 0.21% to 1.21%, with nearly 46% of soils in the low category. Available nitrogen was consistently deficient (87.81–351.23 kg ha⁻¹), with 94.96% of samples below the critical limit. Phosphorus content ranged from 8.61 to 44.49 kg ha⁻¹, mostly in the low to medium category, whereas potassium was severely deficient in 96.4% of samples (<150 kg ha⁻¹). Sulphur levels (6.62–34.3 ppm) were generally low to medium. Correlation analysis indicated strong positive relationships of nitrogen with organic carbon, and moderate associations between phosphorus and nitrogen. Overall, the soils of Vaishali district were found to be low in organic matter and deficient in essential macronutrients, particularly N and K. These findings highlight the need for balanced fertilizer application and integrated nutrient management strategies to sustain soil fertility and enhance crop productivity in calcareous regions of Bihar.