RETENTION OF BORON BY AGRICULTURAL SOILS FROM ONTARIO

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Abstract
The retention of B by 20 agricultural soils from Ontario was investigated by equilibration of the soils with various concentrations of boric acid. The retention of B conformed to both Langmuir and Freundlich adsorption isotherms for all but one soil. Adsorption maxima were calculated for both isotherms and from simple linear regression analysis only pH was found to be significantly correlated with the calculated adsorption maxima. For soils with pH above 6.8, the Langmuir adsorption maxima were significantly correlated with organic C and water-soluble carbohydrate contents. Application of phase diagrams indicated that, under the experimental conditions employed, the solutions of some of the acidic soils were supersaturated with respect to the Ca-containing borate minerals inyoite, colemanite and nobleite and, given a number of reasonable assumptions, that at rates of B application of 3 kg ha−1, acidic soils could be supersaturated with respect to the mineral nobleite. The extent of complexation of B with glucose was shown only to be important at pH in excess of 8. Key words: Boron, carbohydrates, inyoite, colemanite, nobleite, complexation