EVALUATION OF NUTRIENT INDEX FOR SOIL FERTILITY OF SIDDAPURA CATCHMENT, KARNATAKA STATE

Soil quality standards are used as a means to maintain long-term soil productivity and these standards provide threshold values beyond which further alteration of soil properties would significantly change or impair the productivity potential of the soil. Suitability of the soils for a particular crop is an important factor from the productivity point of view. The importance of soil in supporting food crops requires due attention towards study of the chemical composition of soils in relation to crop needs. The study area chosen is Siddapura catchment which is a part of Harangi command area covered in Hassan, Madikeri and Mysore districts, Karnataka state. Geographically it lies between 750 38' E and 760 15' E longitude and 120 24' N and 120 46' N latitude, covering an area of 1522.4 km2. The study area is covered in Survey of India (SOI) Toposheet numbers 48P/10, 48 P/11, 48 P/14, 48 P/15, 57 D/1, 57 D/2, 57 D/3 on 1:50,000 scale. The maximum length and width of the catchment is approximately equal to 37.53 km and 68.88 km respectively. In the present study, representative soil samples are collected from the field in different locations of the study area and are subjected to chemical analysis to determine the various macronutrients and micronutrients present and fertility status of the soils are determined from the nutrient index criteria. Results shows that based on the nutrient index criteria the soil fertility of Siddapura catchment can be categorized into lowlow-medium (LLM) category with respect to available organic carbon, phosphorous and potassium concentrations