Selected farmlands in southern Baja California, Mexico, were surveyed to determine the levels and the causes of salinization/sodication in irrigated agricultural soil. The salt dynamics observed in profiles differed from farm to farm. Low EC and high pH levels were observed in the profiles of sandy fields, because the salt composition of these soils can easily change when salts are leached by irrigation water that contains carbonates of sodium. On the other hand, high levels of salinity and sodicity were observed in the soils of clayey fields. Soil salinization/sodication is complexly interrelated with soil characteristics, the amount and composition of salts in the soil, the quantity and quality of irrigation water applied, and the irrigation methods used. Our findings indicate that irrigation water in Baja California should be supplied at a rate that is sufficient to meet crop requirements without exacerbating salt accumulation. 1. Introduction In arid regions, desertification is mainly caused by human activity [1, 2]. Attempts to grow crops in arid inadequate irrigated areas have mainly resulted in the salinization and/or sodication of the soil. Because the irrigation of agricultural lands in arid regions has not yet become a widespread practices a relatively small area has been degraded compared to the areas used for grazing or those in which rain-fed agriculture is carried out. However, irrigation tends to increase productivity in the short term, and the need to produce food for an increasing population might result in the conversion of grazed, rain-fed, and even virgin lands to irrigated fields [3]. Furthermore, the reclamation of salt-affected land that has been irrigated for agricultural purposes has become increasingly important. Reducing the severity and extent of soil salinity is primarily a matter of soil and water management. Good water management involves both preventing water received in the recharge areas from percolating into groundwater and maintaining the water table of the discharge areas at low, safe levels. The most common approach to salinity management is to maintain a prescribed leaching requirement. However, this approach is ineffective when the irrigation water contains significant levels of sodium, carbonates, and bicarbonates. In addition, the surface drainage capacity of these arid soils is usually poor. The Baja California peninsula was once a part of the North American Plate, of which mainland Mexico remains a part. In southern Baja California, Pliocene to early Quaternary sedimentary formations were deposited
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