Combined Effects of SAR and pH On Infiltration.

Current use of fresh water supplies for irrigation in arid and semiarid regions is not sustainable. There is thus an increasing need to use more saline and more sodic waters for irrigation, as well as use recycled waste waters. The adverse effects of SAR on saturated hydraulic conductivity in laboratory columns are well documented, however there is limited information on long term effects on infiltration and almost no information on the combined effects of pH and SAR.  In this study we examine the infiltration of waters with an EC of 1 dS/m and SAR in the range of 0-10 at pH=7.0 and pH=8.2 in containers of Pachappa soil, both under irrigation only and under cycles of irrigation and simulated rain. The study was conducted for one year and included wetting and drying cycles.  We observed that for all treatments, any increase in SAR above SAR=0 resulted in a decrease in infiltration.  The decrease in infiltration increased with increasing SAR, as expected, but the decrease did not stabilize over time, meaning that the differences in infiltration increased with time as well. Thus the adverse effects are greater than those predicted from short term experiments. Even a moderate increase in pH, from 7.0 to 8.2 adversely impacted infiltration. These results will be useful to development of guidelines for use of low quality waters for irrigation.