The effect of water quality on chemical and physical properties of a Hoban silty clay loam soil in situ

Abstract

Maintenance of permanent agriculture is often difficult to achieve in arid regions because of limited water and associated salinity problems. Water quality standards for irrigation water are generally very broad and often do not account for reactions between the water and the soil to which it is applied. Agricultural crops of the Trans-Pecos Area are entirely dependent upon irrigation due to limited rainfall (less than 10 inches annually) and most irrigation waters contain sufficient salts to require management practices to maintain production. The purpose of this study was to determine the effects of nine types of waters with varying ion composition and concentration (SAR values of 5 to 20, and 27 to 91 meq/L total salts) on the chemical and physical properties of a Hoban silty clay loam soil (in situ), a major soil of the Trans-Pecos area of West Texas. The calcium, magnesium, and sodium concentration, and electrical conductivity of the soil solution from saturated extracts were used to characterize the chemical changes. Infiltration, soil content, and soil water pressure, were measured during the movement of water into and through the soil profile to allow calculation of infiltration rates, and (unsaturated) hydraulic conductivity values. Soil solution data at depths to 170 cm are presented at the initial sampling, following the first 15-cm application of water (well water, SAR 6, 40 meq/L total salts), following the third 15-cm application of water (Salt mixture) to each of the nine plots. Data relative to water movement is presented during the entering and ensuing drainage periods of the three 15-cm water applications. From these data, the influence of the treatment waters on the SAR and electrical conductivity are shown. The influence of treatment waters on water movement is also shown..