The phenomenon of dispersion of soil clay can be caused by the quality of irrigation water. This study investigated the effect of irrigation water with different electric conductivities (EC), combined with different Sodium Adsorption Relation (SAR) values on clay dispersion in soil commonly found in the state of Minas Gerais, with different mineralogies. The samples were collected from the B horizon of three soils (Oxisols) in Viçosa, Belo Horizonte and Barroso, respectively, with high levels of the clay minerals kaolinite, hematite, and gibbsite, and are classified as Yellow-Red Latosol, Red Latosol and dystroferric Red Latosol. The physical, chemical, and mineralogical properties of the soils were characterized. The treatments corresponded to percolation, through the three soils, of NaCl and CaCl2 solutions with six different EC values (20; 50; 100; 200; 400, and 800 mS m-1) and five SAR values (0, 5, 10, 20, and 40 mmol c L-1), in a randomized block design with three replications. The solutions were applied in vertical column and constant load permeameters. The solution was applied until the EC of the effluent approached that in the applied solution (C/C0 = 1.0). To evaluate the effect of the solutions applied to the soil structure, the contents of clay dispersed in water (CDW) were quantified. The values of CDW in the soil materials percolated with the different sodic-saline solutions (CDW-S) were related to EC and SAR of the percolated solutiona. The soil behavior was distinct regardint clay dispersion, which was ascribed to its mineralogy as well as to the degree of weathering. The Yellow-Red Latosol showed a non-dispersive pattern in all treatments. In general, all percolation solutions, especially those with highest EC, regardless of the SAR value, indicated reduced dispersed clay (CDW-S) in the Red Latosol and dystroferric Red Latosol.
soil physics; soil structure; agregacion
