Assessment of soil quality index under coffee land use system of hilly zone of Karnataka, India

Abstract

Soil quality degradation is a major problem in recent times. Coffee is the major plantation crop in the majority of the areas of Chikkamagaluru and Kodagu districts which falls under hilly zone of Karnataka where it is mostly grown on slope terrains. To determine the sustainability of soil and land management practices prevalent in this region, a study on soil quality assessment was done through minimum data set. About 150 soil samples at 0-30 cm depth were collected from different locations of coffee growing plantations of Chikkamagaluru and Kodagu districts. Soil quality index (SQI) was assessed through identifying minimum data set (MDS) by employing principal component analysis. Twenty four soil attributes were subjected to principal component analysis (PCA) which yielded seven principal components with Eigen value >1 and explaining at least 5 % of total variance in the entire data set. The seven PCs together explained 77.86 per cent of total variance. Based on the rotated factor loadings, the selected MDS were exchangeable Mg from PC-1, maximum water holding capacity (MWHC) from PC-2, pH from PC-3, earthworm population density (EWPD) from PC-4, sand from PC-5, available P2O5 from PC-6, and available boron (B) from PC-7.The selected indicators were transformed into scores (linear scoring method) to calculate the SQI. The assessed SQI was 0.44forChikkamagaluru and the0.43 for Kodagu district under coffee land use system of hilly zone of Karnataka and showed non-significant difference between them. The overall contribution of different PCs in the determination of SQI was in the order of Mg – 22.15%, MWHC – 18.63%, pH – 17.45%, EWPD – 16.81%, sand – 11.37%, P2O5 – 7.72% and B – 5.88%.