Chemical Analysis of Soils to Evaluate the Soil Fertility Status of Semi-arid Region of Three Taluks of Tumakuru District, Karnataka, India

Abstract

A study was conducted to assess the fertility status of surface soils from three representative taluks (Gubbi, Madhugiri and Sira) based on their agro-climatic zones. The study aimed to evaluate physico-chemical properties, nutrient index, and relationships among key soil parameters using descriptive statistics, a nutrient index, and correlation analysis. A total of 34 surface soil samples (0-30 cm depth) were collected from fields of farmers, studied for pH, electrical conductivity (EC), organic carbon (OC), available N, P, K, Ca, Mg, S, Cu, Zn, Mn, and Fe. Soil pH varied between 4.7 and 8.9 (mean = 7.3), EC ranged from 0.01 to 0.72 dS m⁻¹ (mean = 0.21 dS m⁻¹), and OC was between 0.35 and 1.18%; thus, most soils were classified as non‑saline, neutral to slightly alkaline, with low to medium organic matter content. Nutrient Index (NI) values showed medium fertility (NI 1.8), while N, P, K, Ca, and Mg had low fertility; S, Cu, Zn, Mn, and Fe reflected high NI values, indicating generally adequate secondary and micronutrient status. Results of correlation analysis indicated a significant relationship among several soil properties, particularly between base cations and micronutrients. The results demonstrate that deficiencies in macronutrients are the major constraints limiting crop production in these semi-arid soils, pointing to a need for balanced fertilization and enhanced organic matter management as important components of sustainable crop production systems.