Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2008
Publication Date: 8/8/2008
Citation: Suarez, D.L., Wood, J.D., Lesch, S.M. 2008. Infiltration into cropped soils: Effect of rain and sodium adsorption ration - impacted irrigation water. Journal of Environmental Quality - Special Submissions. 37:S169-S179. Interpretive Summary: Increasing demands on available water means that irrigated agriculture will likely have to utilize treated waste waters and other impaired waters. Water quality standards for irrigation have been developed with emphasis on desert conditions where rainfall is not an important factor. The objective of this study was to determine if these standards are applicable to management systems in environments where rainfall is an important component of the water budget for crop production. We determined that under rain- irrigation sequences, even low levels of exchangeable sodium result in decreases in water infiltration. The effects observed under cropped conditions, where the soil is considered protected by the physical impact of rain, were comparable to impacts determined earlier under bare soil conditions. These studies indicate that new standards should be developed for environments where rainfall occurs during the growing season.
Technical Abstract: The SAR salinity criteria for irrigation have been developed for conditions where the irrigation water is the only source of water supply. It is not clear that these criteria are applicable to conditions where there are rain and irrigation events during the growing season. The low electrical conductivity of rainfall is expected to result in increased sodicity hazard to soil hydraulic properties. In this study we examine the effects of irrigation waters of SAR 2, 4, 6, 8, and 10 and electrical conductivities of 1 and 2 dS/m on the infiltration rate of two soils in a management system where there are alternating cycles of rain (simulated with a rainfall sprinkler) and irrigation water. A sandy loam and silty clay soil were evaluated under cropped conditions of full canopy cover for 200 d. At the end of the experiment undisturbed soil cores were taken for laboratory determination of saturated hydraulic conductivity. Reductions in infiltration in the container studies were observed for both soils for SAR above 2. Decreases in saturated hydraulic conductivity were observed above SAR 2 for the sandy loam soil but significant differences were not observed for the silty clay soil, likely due to the high degree of sample variability.