Zinc Adsorption as Related to Its Availability in Some Soils of Karnataka

Zinc adsorption was studied in seven soils of the state of Karnataka. In three red soils with lower pH and cation exchange capacity (CEC) the adsorption isotherm conformed to Langmuir's equation. In the other four soils, which were either sodic or calcareous and had higher pH, the isotherms could be resolved into two linear portions and the lower portion showed better fit to Langmuir's equation. The adsorption maxima accounted for 24 to 35.4% of the CEC in red soils, whereas in the other four the adsorption maxima pertaining to the lower linear portion correspond to 35 to 54.4% of CEC. Correlation studies showed that zinc content and uptake by tomato had a negative relationship with adsorption maxima, bonding energy coefficients and maximum buffering capacity.