Abstract
Sllils GIIT\ both the positivI: and negative charges. To accomplish quantitative information for arid lands of Pakistan. samples lrorn the A and B horizons of normal (Ustalfic Haplatgids) and salinesodic (Aquic Haplargids) soils were collected. Positive and Ill:gativl: charucs WLrI: determined by saturating the samples with KCI solution followed by desorption with Na,SO~ solution. The zero point of charge (ZPC) was determined by salt-titration method. Negative charge for the A and B horizons of normal soil was (l.!l7 and o.O? crnol kg '. while corresponding values were 5.20 and 5.55 cmol kg' for the saline -sodic soil. Positive charge ill the A and B horizons of normal soil was I. X5 and 2.60 cmol, kg I • while charge values were 2.32 and 3.17 cmol kg tor the A and B horizons of salt-affected soil. respectively. Negative and positive charge was higher at higher soil pH The ZPC values were 11.<)5and 7.0() tor the A and B horizons of the normal soil. while these were 7.60 and 7.35 for the A and B horilOns of the salt-affected soil. respectively. At ZPC, permanent charge was 4.80 and 3.47 cmol, kg' for the A and B horizons of normal soil and 2.88 and 2.38 cmol, kg' for the A and B horizons of the salt-affected soil. respectively. Variable charge (pl l-dcpendcnu at ZPC was 1.85 and 2.60 cmol, kg' for the A and B horizons of normal soil. while 2.32 and 3.17 cmol, kg' for the A and B horizons of salt-affected soil. respectively. Although the native soils arc dominated by illite type clay minerals. the results indicated the presence of some other minerals carrying pl-l-depcndent negative and positive charges both in thl: Ilorll1~t1as wL11as salinL-smlic soil. Key words: calcareous soils. charge characteristics, xalt-al'lccu«!
