Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/9/2004
Publication Date: 4/11/2005
Citation: Levy, G.J., Goldstein, D., Mamedov, A. 2005. Saturated hydraulic conductivity of semi-arid soils: combined effects of salinity, sodicity and rate of wetting. Soil Science Society of America Journal. 69:653-662. Interpretive Summary: How fast water enters into the soil depends on its texture, (i.e., sand, silt and clay fractions), aggregate stability, as well as the amount and type of chemicals, especially salts, adsorbed in the soil particles. In semi-arid regions, buildup of salt in the soil is a common problem. Excessive amount of sodium in the soil can cause disintegration of soil aggregates, resulting in reduced water entry into the soil. But, the sodium effect is also dependent on the soil texture, the quality of water used for irrigation and soil condition. In this research, we quantified the interactions of soil texture, sodium saturation, and wetting rate on saturated hydraulic conductivity, a measure of water entry. We found that when water is low in electrolytes, clays swell and aggregates disintegrate easily, causing a reduced hydraulic conductivity. These processes occur more severe with increasing in the degree of sodium saturation and water adding rate, particularly in clayey soils. When the soil has 5 to 10 percent sodium saturation, the use of saline water can keep the soil aggregates together, hence, increases its hydraulic conductivity. The impact of this research is an improved water management strategy to maintain infiltration for soils that are affected by salt accumulation.
Technical Abstract: Combined effects of soil conditions (wetting rate), soil sodicity and salinity on soil saturated hydraulic conductivity (HC) have not been studied systematically and were the objective of our study. We examined the effects of (i) exchangeable sodium percentage (ESP, 1-20) and fast wetting (50 mm h-1) and leaching with distilled water on the HC of 60 Israeli soils (7-70% clay); and (ii) wetting rate (2 or 50 mm h-1), ESP and water salinity (distilled water or saline water, 2 dS m-1) on the HC of 16 selected samples. Results of the first experiment showed that (i) steady state HC of medium- and fine-textured soils was lower than 2 cm h-1 already for non sodic soils, and (ii) the adverse impact of sodicity on the HC strongly depended on soil texture. The second experiment revealed that in the loamy sand rate of wetting had no effect on the HC beyond that of sodicity and salinity. In the loam, sandy clay and clay soils a significant triple interaction among water quality, wetting rate and ESP in their effect on HC existed. In the absence of electrolytes, the impact of fast wetting (slaking) and swelling on the HC was most notable, mainly at the intermediate sodicity levels (ESP 5-10). Use of saline water significantly reduced the impact of fast wetting and swelling on the HC. Our results suggested that combined effects of salinity, wetting rate and sodicity on the HC were complex and should thus be considered simultaneously when estimating soil HC.