Effect of reclamation on the structure of silty-clay soils irrigated with saline-sodic waters.

The objective of the work was to evaluate, by using the micromorphometric method, the effects of reclamation on porosity of two different clay loam soils irrigated with saline-sodic waters. Soil samples of the Ap horizon were put in cylindrical containers and irrigated with 9 types of saline-sodic waters (3 levels of salinity combined with 3 levels of sodicity). After a 4-year period, correction treatments were initiated by addition of calcium sulphate and leaching until electrical conductivity and sodium absorption ratio values of the drainage water matched 3 dS m-1 and 9, respectively. After 2 years of correction treatments, undisturbed soil samples were taken from the surface layer and soil thin sections for porosity measurements. Both soils did not show critical macroporosity values (> 10%, below this threshold a soil is classified as compact). Nevertheless, the soils exhibited a different behaviour: total porosity of the Pachic Haploxeroll soil was not affected by difference in water salinity and alkalinity; on the contrary, the Udertic Ustochrept soil showed a lower porosity associated with higher salt concentration in the irrigation waters. This may be due to the different iron and aluminium sesquioxides content and, as a consequence, a different effect on soil aggregate stability. K e y w o r d s: soil structure, soil porosity, salinity, image ana- lysis, bulk density