Retention of Boron-A Plant Micronutrient Using Pure Clay

Boron is an essential micronutrient with narrow range of deficiency and toxicity. To predict B behavior in soils and its influence on plants, it is crucial to understand the mechanisms of B sorption by mineral phase. The adsorption of B increased as the pH increased up to 10, thereafter it decreased with further increase in the pH. The amount of boron adsorbed increased slightly at 4 hours of time and decreased as the time was increased to 6 hours thereafter an increase and decrease was observed for subsequent variation in contact time. As the concentration of B increased in the solution the adsorption of B increased. Yet the percentage of B adsorbed decreased. The importance to study the effect of varying concentration was to highlight the availability of this trace element, which enters the soil by number of path ways. At moderate levels of concentration the soil will act as repository for this trace element, but at higher concentration it may be transported to ground water table. The amount of B adsorption was more in presence of Ca⁺² ions. The B adsorption may be more in alkaline soils with high clay content and high CaCO₃ content. The adsorption of B was initially rapid followed by a slow process. As the amount of clay increased, for a given initial concentration, the amount of adsorption increased. Application of Freundlich isotherm and Langmuir isotherm to the adsorption of boron were satisfactory. The applicability of the Lagergren model to adsorption of boron was not satisfactory A plot of Ln Ci/Ce Vs t indicated that the adsorption of B does not follow the first order kinetics. The value of R_L, a dimensionless equilibrium parameter, was 0.05363 indicating favorable adsorption.