Assessment of spatial distribution of bicarbonates (HCO3 ) using geo-spatial technology Indo-Gangetic Plain, India

This study explores the spatial variability of bicarbonate (HCO– ) and its correlation with soil physicochemical properties in the Mirzapur district of Uttar Pradesh, India. The district spans 4,522 km² and has a humid to sub-humid climate. It is located between latitudes 24°41’30"–24°47’N and longitudes 82°21’45"– 82°30’E. The region receives an average of 1,085 mm of rainfall annually, with temperatures ranging from 14.18°C in December to 39.80°C in January and an approximate relative humidity of 80%. The region’s sandy loam to clay loam soils are a result of its alluvial plains in the north and Vindhyan terrain in the south. The district’s twelve geo-referenced profiles were sampled at four different depths (0-15, 15-30, 30- 45, and 45-60 cm). This yielded 48 soil samples that were subjected to standard physico-chemical analyses. Electrical conductivity (EC) varied between 0.02 and 0.206 dSm-1 and soil pH ranged from 5.1 to 8.8, indicating areas of both acidic and alkaline conditions and exhibiting a slight depth-wise variation. Bicarbonate levels peaked between 45 and 60 cm (mean: 26.75 mg/100 g), with increasing trends at deeper layers. The concentrations ranged from 18.4 to 36.9 mg/100 g. A moderate to strong spatial dependency (nugget-to-sill ratio < 0.25) and high prediction accuracy (low RMSE and ME near zero) were found through spatial analysis using ordinary kriging in a GIS environment. About 90% of the area had bicarbonate content between 22 and 30 mg/100 g. Influences from topography, parent material, and climate were evident in the Gaura region’s highest bicarbonate levels and Lauriya’s lowest. These results advance our knowledge of the distribution of bicarbonate and its effects on soil suitability and nutrient management for agricultural productivity in the Mirzapur district.