Spatial variations in soil micronutrients as influenced by agro ecological conditions in a tropical humid region

The continuous and indiscriminate use of NPK fertilizers for boosting productivity in the farming sector longer periods resulted in the imbalance of soil nutrients in the long run. This nutrient disparity in soil gradually throw back in crops, animals and human beings, leading to various degenerative and deficiency related diseases now more than ever. This constrained site specific nutrient management for crops, which essentially rely upon evaluation of variability spatially and temporarily. In this study we scrutinized the spatial variation of soil fertility in exhaustive plough lands of Thrissur district, Kerala, India. A total of 600 geo referred soil samples were collected from different agroecological units of the district and examined for selected micronutrients such as Fe, Cu, Mn, Zn and B. Geo-statistical mapping tool (Arc GIS10.2.2) was used to quantify the degree of spatial variability in various soil fertility parameters. The spatial variation of nutrients in the study area was assessed by using semivariogram method in kriging interpolation and spatial dependence was calculated. The best fit model was applied to the kriging interpolation according to the determination coefficient, which is the correlation of measured and predicted values on space and spatial distribution maps of all the micronutrients. Among the variables analyzed, B revealed strong spatial dependence (24%), Zn with weak spatial dependence (78%) with model gaussian and others with moderate spatial dependence. The results from the present study call to develop a strategy for site-specific management for the parameters showing moderate spatial dependence and weak spatial dependence. But for B, showing strong spatial dependence, only uniform management is needed because it was greatly affected by the structural factors such as climate, topography and parent material. Spatial variability of soil properties is essential for precision agriculture because soil parameters with little or no spatial dependence will not be conducive to site-specific management, and will be managed on the average level only.