Season-long Changes in Infiltration Rates Associated with Irrigation Water Sodicity and pH

There is increasing need to substitute low quality waters, including saline sodic waters and treated municipal waste water for fresh water when irrigating land in arid and semi-arid regions of the world. In almost all instances low quality waters are more sodic than the fresh waters currently utilized. A major hazard associated with these waters is the reduction in water infiltration rates due to the increase in the soil exchangeable sodium percentage. Deterioration of soil; physical properties may threaten the present and future productivity of these lands. We examine the effect of even small increases in sodium on the infiltration rate over the span of a complete cropping season in a series of experiments from sodium adsorption ratio (SAR) of 0-13. Based on these controlled studies with wetting and drying cycles over 180 d conducted in container studies, we conclude that for the non-calcareous soil examined, even small increases in SAR resulted in significant decreases in infiltration rates. The deterioration in infiltration capability increased with time, suggesting that short term experiments may not characterize the long term consequences of using degraded waters for irrigation. Increased pH resulted in decreased infiltration at comparable SAR values.