Submitted to: Plant and Soil Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/28/2013
Publication Date: 2/7/2013
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2424.pdf
Citation: Suarez, D.L. 2013. Water quality criteria for use of saline/degraded water for irrigation. Plant and Soil Conference Proceedings. pp: 136-140.
Interpretive Summary: Fresh water use in arid and semiarid lands is not sustainable and agriculture will need to utilize marginal and saline waters for irrigation. Use of saline and marginal quality waters is possible, but sustained use requires consideration of the impacts of these waters on both crop production and maintenance of good soil physical properties. We present new water quality criteria that indicate that pH as well as sodicity and salinity must be considered for maintenance of good water infiltration, and indicate that sodicity hazard is currently underestimated, especially in regions with appreciable rainfall. We also demonstrate that current criteria overestimate the need for leaching, and vastly overestimate yield loss with saline waters. In many instances waters considered unsuitable for irrigation can in fact be utilized without need for excessive water applications and with only moderate yield loss. Use of these waters thus becomes primarily an economic rather than agronomic evaluation. These results are of interest to extension specialists and growers in arid regions as well as planners in municipal waste water and agricultural water districts.
Technical Abstract: Current fresh water use in arid and semiarid lands is not sustainable, as use exceeds replenishment and demand for water continues to increase. Agriculture will either need to reduce acreage under irrigation, which is undesirable since it will reduce food supply, or irrigate with alternative water sources and more effectively utilize existing water supplies. Use of saline and marginal quality waters is possible, but sustained use requires consideration of the impacts of these waters on both crop production and maintenance of good soil physical properties. In many instances waters previously considered not useable or impractical for irrigation can be used with careful management. Earlier water criteria may in some instances be overly conservative due to simplifying assumptions used in their evaluation. In other instances, hazards related to soil physical properties were underestimated. We present new water quality criteria that consider the effect of irrigation water pH as well as sodium and salinity on hazards to loss of infiltration. We also demonstrate the utility of the UNSATCHEM computer simulation model as a management tool, for evaluation of leaching requirement and irrigation with waters of elevated boron concentration. Dynamic computer simulations with integrated plant response , water transport and chemical processes relevant to salinity stress result in predictions of much greater yield, lower soil salinity and greater leaching, as compared to steady state assumption guidelines. Using computer simulations we also demonstrate that some marginal waters considered unusable from steady state analyses, such as waters with elevated high boron concentrations, can in fact be used intermittently without adverse impacts on yield or soil properties.