Forms of Boron in Alkaline Alluvial Soils in Relation to Soil Properties and Their Contribution to Available and Total Boron Pool

In alkaline alluvial soils of Punjab, located in northern India, seven forms of boron (B) were compared using different extractants. The comparison was assessed in relation to soil properties and their contribution to soil available and total B pool. The mean contents of water-soluble (WS-B), hot-water-soluble (HWS-B), hot 0.01 M calcium chloride (CaCl2)–soluble (HCC-B), acid-soluble (HCl-B), leachable or mannitol-extractable (Mann-B), ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA)–extractable, and total B in alluvium-derived soils of Punjab were 0.24, 0.49, 0.50, 0.53, 0.55, 0.19, and 17.04 mg kg−1 soil, respectively. All the forms of B were related with soil properties, especially organic carbon (C) content, clay content, texture, and cation exchange capacity. Different forms were correlated significantly with each other. Total B content ranged from 10.25 to 25.42 mg kg−1 and was nonsignificantly correlated with other forms of B. All the forms of B were positively and significantly correlated with organic C content, clay content, and cation exchange capacity while negatively correlated with soil pH, electrical conductivity, and sand content. The most commonly used form of B, i.e., hot water-soluble B, was significantly correlated with hot 0.01 M CaCl2–extractable B (r = 0.885**). Regression equations showed that 85, 94, 95, 88, 90, and 86% variations in WS-B, HWS-B, HCC-B, HCl-B, Mann-B, and AB DTPA-B contents were governed by various soil properties.