Prof. Hassan Hamza Abbas Ramdan :: Publications:

The current work aimed at spotlighting the importance of cation exchange phenomenon as one of the most important processes adffecting the different properties of soils. Thus, two top soils (0-30 cm) wer undertaken from Burg El-Arab (highly calcareous soil) and Moshtohor (alluvial non calcareous soil or low CaCO3 content)m besides their separated clay fractions, the organic matter-free soils and two commercial clay minerals namely attapulgite and bentonite. All of these material were subjected to equilibrium with chloride solutions having different Na/Cd ratios varied from 10/90 to 90/10. the obtained results could be summarized in the following: Increasing Na/Ca ratio in equilibrium solution increased equivalent fractions of exchangeable Na on all the investigated exchange materials showed quite different variations in this concern. All the calculated selectivity coefficients tended to decrease with increasing Na/Ca ratio at the equilibrium solutions indicating some performance for Na over ca at the low Na concentrations and vice versa. Values of selectivity coefficients of the clay fractions separated from the studied soils were generally higher than the corresponding ones of the examined soils themselves. On the other hand, removal of organic matter from soils resulted in lower selectivity coefficient compared with soil or their clay components. Values of selectivity coefficients of both attapulgite and bentonite clay minerals for Na were inversely related to the values of Na equivalent exchangeable fraction on these exchanger. Correlation coefficients between sodium adsorption ratio SAR and exchangeable sodium ratio (ESR) were highly significant indicating that the SAR value could be a reliable parameter for estimating exchangeable Na on soil complex; however, assessment of sodicity hazard requires also calculation of selectivity coefficients of soils for Na ion to integrate the picture.