Effect of High Sulfate Irrigation Waters on Soil Salinity and Yields1

Abstract

AbstractMore information is needed concerning the effects of high sulfate waters on soil salinization and the magnitude of yield losses of crops irrigated with such waters. This greenhouse study investigated the response of tomato (Lycopersicon esculentumL.), eggplant (Solanum melongenaL.), and bell pepper (Capsicum annuumL.) to soil salinity as influenced by the ionic composition of two naturally occurring sulfate waters (EC=3.1 dS/m) in comparison to rainwater. One of the saline waters was saturated with gypsum (34.8 mmol(−)/L) and the other contained 15, 18, and 14 mmol(±)/L of SO24, Na, and Cl, respectively (mixed water). In all treatments a 0.3 leaching fraction was used. The soil was a Pellic Vertisol, which contained no gypsum. Soil salt buildup was high with the saline waters and followed two stages. A sharp increase of soil electrical conductivity (EC) initially occurred with ions of both sparingly (Ca, SO24) and highly (Mg, Na, Cl) soluble salts contributing to soil EC. Sulfate concentration at the initial stage increased due to the presence of other ions in the soil solution and it was more than twice that of a pure gypsum solution. At the second stage, Ca and SO24concentrations in soil solutions remained unchanged and the increase of EC was slower in comparison with the initial stage. At both stages the increase of soil EC was higher with the mixed water. A significant increase of soil solution sodium adsorption ratio (SAR) also occurred with the mixed water. Fresh fruit yields of tomato decreased by 29 and 21%, and eggplant yields were reduced by 23 and 16% when irrigated with the mixed or the sulfate water in comparison to rainwater, respectively. Lower yield was due to smaller fruit size. Yield of bell pepper was not affected, but quality deteriorated.