To estimate clay dispersion the water dispersible clay is determined in the laboratory. This analysis may not correspond to reality in saline and saline-sodic soils, with high concentrations of salts in the solution. In this context, the dispersed clay was determined, using solutions of different electrical conductivities (0; 0.3; 0.6; 0.9 and 1.2 dS m-1) in seven representative soils of the State of Pernambuco, with the exchangeable-sodium-percentage adjusted in the range of 5-30%. The results showed that there was an increase of dispersed clay directly related to the increase in the exchangeable sodium percentage and the decrease of the electrical conductivity of the solution. The response to treatments was more pronounced in soils with higher proportions of more active clays compared to those with more iron oxides. The determinations of the water dispersible clay are accomplished with deionized or distilled water. However, in soils affected by salts, it is concluded that the determinations should be carried out with solutions of electrical conductivity different from 0 dS m-1 using solutions with values similar to those determined in the saturation extract.
saline soils; saline-sodic soils; exchangeable sodium percentage; saturation extract
