Saline water irrigation in semiarid region: I – effects on soil chemical properties

The use of saline water for crop irrigation is a commonly adopted practice among the farmers in the semiarid regions around the world, but the magnitude of soil salinization resulting from the use of these waters is currently insufficiently understood. This work aims to evaluate the chemical attribute changes of two Fluvisols cultivated with onion and subjected to irrigation with increasing levels of salinity, expressed by electrical conductivity (EC) and sodium adsorption ratio (SAR). Sandy loam and silty clay loam soils were irrigated with three different levels of saline waters with electrical conductivity (EC - 200, 700 and 2,000 μS cm-1) and six levels of sodium adsorption ratio (SAR - 0, 5, 10, 15, 20 and 25 (mmolc L-1)0.5). Thus, the experiment consisted of a complete factorial arrangement 2 x 3 x 6 (two soils, three EC levels and six SAR levels), in four replicates. The soils were cultivated with onion and pH levels of the soil were measured at 90 days after transplanting, as were the contents of exchangeable and soluble cations. ESP and SAR values were then calculated. This study revealed that the use of water with salinity at or above 700 μS cm-1 is capable of promoting changes in the chemical properties of soils and the continuous use of irrigation water with high EC and high SAR values may promote salinization and sodification of Fluvisols in a semiarid environment. These changes were found to be more severe in silty clay loam soils than in sandy loam soils.