Evaluation of Different Extractants for Boron Estimation in Soils of Odisha and Andhra Pradesh

The present study was conducted to compare the four different extractants widely used in boron (B) determination in soils and to screen the most suitable extractant for acidic (Alfisols) and alkaline (Vertisols) soils of Odisha and Andhra Pradesh. A total of 200 surface soil samples were collected across two sites (100 from each site) representing different pH ranges. Hot-water-soluble boron (HWS-B) extraction procedure being the most widely used B determination procedure was kept as a benchmark in order to compare the B extracting efficiency by the extractants viz., 0.01 M Calcium Chloride (CaCl2), 1 N Ammonium acetate (NH4OAc) pH-7.0 and 0.01 M Barium Chloride. The mean values of hot water extractable B for acidic soils were 0.49 (mean between 0.18 and 1.50 mg kg-1), CaCl2 – 0.42 (mean between 0.14 and 1.52 mg kg-1), BaCl2 – 0.45 (mean between 0.10 and 1.68 mg kg-1) and NH4OAc – 0.60 (mean between 0.17 and 2.43 mg kg-1). The mean values of hot water extractable B for alkaline soils were 1.87 (mean between 0.71 and 4.79 mg kg-1), CaCl2 – 1.57 (mean between 0.45 and 5.43 mg kg-1), BaCl2 – 1.37 (mean between 0.52 and 4.15 mg kg-1) and NH4OAc – 1.92 (mean between 0.85 and 8.33 mg kg-1) in acidic and alkaline soils respectively. The coefficient of variation for extractable B varied from 53.0 to 66.6 and 42.7 to 55.7 in acidic and alkaline soils respectively. The variation in B extracting efficiency in both the types of soils was found in the order: Hot water > Hot CaCl2 > BaCl2 > NH4OAc. Authors conclude that amongst all the compared extractants, 0.01 M CaCl2 extraction may be an adequate procedure for B determination in both the acidic as well as alkaline soils.