Effect of Irrigation Water Quality Under Supplementary Irrigation on Soil Chemical and Physical Properties in the “Southern Humid Pampas” of Argentina

Summary

Salinity and sodicity were quantified at five locations irrigated with central pivots and different water qualities in the southeast of Buenos Aires Province. Changes in electrical conductivity (EC_e) and sodium adsorption ratio (SAR_e) of saturated soil extract were determined from soil cores collected to a depth of 0.6 m between 1996 and 1998. Unsaturated hydraulic conductivity was measured with disk in-filtrometers. Soil from one location, Balcarce, was treated with synthetic waters to obtain variable levels of SAR_e. Laboratory studies on optical transmission (OT), aggregate percentage (AP), and saturated hydraulic conductivity (Ks) were performed.

Infiltration of rainfall caused a substantial dilution of salt concentration. Changes in sodicity were persistent, but tended to stabilize between SAR_e = 5 to SAR_e = 7. When irrigation was discontinued for a year and 1129 mm of rainfall leached the soil, the SAR_e value decreased from 5.3 to 1.8.

Ks showed a threshold at exchangeable sodium percentage (ESP) of 5. The results from the Ks laboratory experiment were non-consistent with field estimation of Ks using disk infiltrometers.

Key Words:

• Supplementary irrigation
• water quality
• salinity
• sod-icity