Soil Quality Assessment in Major Mango-Growing Regions of Southern Karnataka, India

Abstract

The Soil Quality Index (SQI) is a vital tool for crop-specific land-use planning aimed at sustaining productivity and long-term soil health. This study identified key soil indicators that influence soil quality across two major mango-growing belts in southern Karnataka. Soils were sampled from the Central Mango Belt (Davangere, Chikmagalur, Shivamogga, Chitradurga, Mandya, and Mysuru) and the Southern Mango Belt (Kolar, Tumakuru, Chikkaballapura, Bengaluru Rural, Ramanagara, and Bengaluru Urban), representing diverse agro-climatic conditions. Soils samples were collected from the horizons of 15 representative pedons and analysed for their physico-chemical properties. Principal Component Analysis (PCA) was used to derive a Minimum Data Set (MDS) of key soil indicators, and the Soil Quality Index (SQI) was subsequently computed using additive and weighted approaches with both linear (LSF) and non-linear (NLSF) scoring functions. In SMB, Bangalore North, Hoskote, Chintamani, and Srinivasapura taluks showed high to very high SQI, whereas Mulabaghilu exhibited low SQI (0.38–0.43) due to high sand content and exchangeable sodium. Similarly, in the CMB, Tarikere and Hunsur Taluks showed high to very high SQI, while Nagamangala recorded a low SQI (0.36), constrained by a shallow effective soil depth. Yield–SQI relationships showed that NLSF captured soil functional variability more effectively than LSF, while weighted indexing outperformed the additive approach, particularly in semi-arid red ferruginous soils. The findings highlight the importance of incorporating inherent soil quality into land-use planning for perennial crops. These results offer a robust basis for region-specific, crop-optimized land use planning in comparable agro-climatic environments.