Spatial Variability of DTPA Extractable Micronutrients in the Soils of Bara Tract of Sardar Sarovar Canal Command in Gujarat State, India

The spatial variability of DTPA extractable Zn, Fe, Cu and Mn was investigated in the soils of Bara tract of Sardar Sarovar canal command located in Gujarat State, western India. The surface soil was systematically sampled to describe the spatial variability by geostatistical techniques. The spatial variability of the micronutrients was described by both graphical method and empirical distribution function statistics (Kolmogorov statistics D). At the sampled scale results showed that the micronutrients viz., Zn, Fe and Cu followed normal distribution whereas the Mn followed lognormal distribution. The measurements are spatially dependent and also present a distinct ordered spatial variation. The spatial structure of the studied micronutrients was analysed and variogram models with a nugget component and two spatial components' with ranges of 9 and 10 km were fitted to the experimental results. Contour maps prepared by ordinary kriging allowed to identify micro-regions with significantly high or low DTPA extractable micronutrient contents. Accordingly 10% of the area is found to be deficient in zinc, 5% in copper and iron whereas available manganese content is adequate in the area. The number of samples required to assess a mean value for DTPA extractable micronutrient content was calculated. Reasonably accurate determination (90% confidence and 10% relative error) of mean DTPA extractable micronutrients contents in this area requires 16, 24, 22, and 55 samples for Zn, Fe, Cu and Mn, respectively.