Assessment and Mapping of Available Soil Nutrients using GIS for Nutrient Management in Hot Arid regions of North-Western India

Soil fertility assessment and mapping for hot arid regions of Thar Desert in the Indian state of Rajasthan was carried out and on the basis of fertility ratings the soils were classified as low, medium and high. In the present assessment a systematic set of 5655 soil samples across the land use systems viz., rainfed croplands, irrigated croplands and rangelands covering 12 districts of hot arid Rajasthan were collected using global positioning system (GPS). The soil samples were analyzed for pH, electrical conductivity (EC), organic carbon (OC), available phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu) and manganese (Mn). Results of the soil analysis revealed that OC is low throughout the region, while available P was low to medium, but generally medium to high in available K. Among the micronutrients, Cu and Mn were adequately supplied in most areas, but Zn and Fe were inadequate in large parts. The spatial variability of OC and available plant nutrients viz., P, K, Fe, Zn, Cu and Mn in hot arid regions of Rajasthan across the land uses in region, has been mapped in a geographic information system (GIS), and their adequacy determined as per the criteria followed in the soil testing laboratories. Spatial distribution maps indicated that about 99.4, 48.7, 11.0, 56.1 and 41.0% of the area are under low availability class for OC, P, K, Zn and Fe, respectively. Present study also showed that the hot arid regions of India not only deficient in individual nutrients but they also suffer from multi-nutrients deficiencies which warrants attention for soil test based integrated plant nutrition system. The wide spread deficiencies of P, Fe and Zn were most revealing; their deficiencies varies with topography, soil type and land management practices. Irrigated croplands were better endowed than other land uses in respect of OC, P, Zn and Cu; rangelands in respect of K and Fe, and rainfed croplands in respect of Mn. With use of information technology tools like GIS and GPS helps in generation of spatial data/maps on distribution of available plant nutrients with which we can precisely use the required input at right place (location specific application of inputs). Information on spatial distribution of available micronutrients enables grouping of the soils into homogenous units for better nutrient management.