Abstract
Adsorption data for 20 calcareous soils, obtained by equilibrating soil samples with 9 different concentrations of Manganese, were evaluated using Langmuir adsorption equations. When the data were plotted according to the conventional Langmuir equation, the isotherms were curvilinear at low Mn concentrations and linear at higher concentrations. Where the data were fitted to a "competitive" Langmuir equation, the isotherms were again found to be nonlinear, indicating that more than one population of adsorption sites existed in these soils. Manganese adsorption maxima, estimated from the linear parts of the conventional Langmuir isotherms, were highly correlated with the cation exchange capacity (CEC) of the soils but not with values of organic matter content, calcium carbonate equivalent or free iron. A desorption study confirmed that part of the adsorbed Mn was held quite tightly.
NOTES
1 Contribution from the Soils and Irrigation Dep., American Univ. of Beirut, Beirut, Lebanon. Journal no. 516B. Presented before Div. S-2, Soil Sci. Soc. Am. Chicago, Ill., 4 Dec. 1978.
2 Former Assistant Professor, Associate Professor, and former Graduate Student, respectively. The present address of the senior author is Soil Science Dep., University College, Dublin, Ireland. The third author is now with Soil Testing Institute, Rawalpindi, Pakistan.
Received for publication February 8, 1980.
Accepted for publication March 18, 1980.