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

Author
item Suarez, Donald
item GONZALEZ RUBIO, ALBERTO - University Of California

Submitted to: World Congress of Soil Science
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2010
Publication Date: 8/1/2010
Citation: Suarez, D.L., Gonzalez Rubio, A. 2010. Season-long Changes in Infiltration Rates Associated with Irrigation Water Sodicity and pH. Proceedings in the 19th World Congress of Soil Science pp: 54-56.

Interpretive Summary: The increasing need to utilize low quality waters for irrigation in arid regions means that many water sources previously considered unsuitable for irrigation need to be re-evaluated. Currently used guidelines do not consider the effect of pH on infiltration nor do they consider the impact of rain when using irrigation water. This research examined the impact of sodium and pH on the infiltration of water with and without the presence of rain, in outdoor containers under a season- long study with wetting and drying cycles to better simulate field conditions. Based on these studies we conclude that the hazard of degraded waters is manageable with surface amendments, but the hazard of reduced infiltration is greater than currently considered, even for waters of low SAR. Rain increases the hazard associated with irrigation of sodic waters, as does an increase in the water pH from 7 to 8.2. This research is of interest to water quality specialists, agricultural consultants, farm advisors, and water agency personnel.

Technical Abstract: 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.