Assessment of soil quality index (SQI) in irrigated paddy and sugarcane ecosystems within the Thonnur Kere distributary of the Southern Dry Zone of Karnataka

Soil quality assessment is vital for sustainable land management, particularly in intensively irrigated agroecosystems. This study evaluates the soil quality index (SQI) of irrigated paddy and sugarcane ecosystems within the Thonnur Kere distributary of the Southern Dry Zone of Karnataka, using a principal component analysis (PCA) linear score-based approach. To measure and categorize soil quality and find sensitive markers impacting total soil health, soil samples from 3 regions—upper, middle and tail-end—were examined. The "very high" quality class (Grade I, >0.547) was occupied by the upper, middle and tail-end areas, with corresponding SQI scores of 0.74, 0.68 and 0.78. The tail region's sensitivity index, which was 1.15, showed that soil health was very susceptible to management techniques. Overall soil quality is generally good across the command area, despite regional variations in particular soil metrics. By highlighting important factors affecting soil functioning, the PCA technique successfully decreased the complexity of the data. The importance of nutritional status in determining soil health was demonstrated by the essential indicators that emerged: bulk density, organic carbon, cation exchange capacity, exchangeable nutrients and accessible macronutrients. Interestingly, the tail-end region's strong SQI points to either natural soil resilience or efficient management techniques. This study highlights the necessity of site-specific soil management techniques to maintain soil quality, with an emphasis on nitrogen balance and soil physical quality. The study offers a useful paradigm for the long-term sustainability of irrigated farming systems in semi-arid canal command regions and supports evidence-based planning.