Spatial variability and mapping of extractable boron in soils of Bara tract under Sardar Sarovar Canal Command area of Gujarat

Bara tract under Sardar Sarovar Canal Command of Gujarat State has alkaline, calcareous and low organic carbon alluvial salt-affected black soils, predominantly classified as Vertisols. In this region, crops like cotton, pigeon pea, sorghum and wheat are cultivated as rainfed crops with sporadic application of saline ground water. Due to prevailing semi-arid climatic conditions, salinization of soils, saline ground water and restricted leaching condition, boron toxicity is generally expected. This study embodies the evaluation of boron status of soils, its spatial distribution and mapping of spatial variability. In an effort to find relative efficiency of extractants, the HWE-B (hot water extracted boron) and HCl-B (dilute HCl extracted boron) were compared for these soils. Dilute HCl extracted boron was significantly correlated with HWE-B and therefore dilute HCl extraction method is suggested for assessing the B fertility in these soils as this method is less tedious, rapid and less error-prone. These soils have extractable boron content ranging from 0.07 to 2.98 mg kg⁻¹ with an average of 1.02 mg kg⁻¹. Statistically the data on boron content in this area follow the normal distribution, which is observed from graphical as well as empirical distribution statistics. Boron content of these soils has spatial dependence and the isotropic semivariance is computed and modelled by a nugget component plus a spherical structure. The range of spatial dependence of boron is 8 km. Using the modelled variogram, kriged estimates have been computed by ordinary kriging and a contour map was prepared.