Salt-affected soils, both saline and sodic, may develop under both dryland and irrigated conditions,affecting the physical and chemical soil properties, with negative consequences in the environment, in cropproduction and in animal and human health. Among the development processes of salt-affected soils, theprocesses of sodification have generally received less attention and are less understood than thedevelopment of saline soils. Although in both, hydrological processes are involved in their development, inthe case of sodic soils we have to consider some additional chemical and physicochemical reactions,making more difficult their modeling and prediction. This is especially true where we have to consider theeffects of the groundwater level and composition. In this contribution there are presented three case studies:one related to the development of sodic soils in the lowlands of the Argentina Pampas, under dry-landconditions with sub-humid temperate climate and pastures for cattle production; the second deals with thedevelopment of sodic soils in the Colombia Cauca Valley, under irrigated conditions and tropical sub-humidclimate, in lands used for sugarcane cropping dedicated to sugar and ethanol production; and the last onerelated to the sodification of soils in the Western Plains of Venezuela, under irrigated conditions, sub-humidtropical climate and continuous cropping of rice under flooding. The development of sodicity in the surfacesoil is partially related to the composition and level of the ground-water, mainly affected in the Argentinacase by drainage conditions, in the case of Colombia to the inefficient irrigation and inadequate drainage,and in the case of Venezuela to the soil management and irrigation system. There is shown how the modelSALSODIMAR, developed by the author, based on the balance of water and soluble components of bothirrigation water and ground-water, under different water and land management conditions, may besuccessfully adapted for the diagnosis and prediction of the different processes and problems, and forselection of alternatives for their prevention and amelioration.
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