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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 9/1/2008 Publication Date: 9/7/2008 Citation: Suarez, D.L. 2008. Salinity control on irrigated land and use of saline water for irrigation. Meeting Abstract. Given at workshop "State of the art of salinity control and use of low quality waters in irrigated areas" held in Santiago del Estero, Argentina September 9-11, 2008 p. 1-2. Interpretive Summary: Technical Abstract: Current irrigation practices in arid and semi-arid regions throughout the world are not sustainable. These regions are experiencing increasing population and development with increasing demands for limited fresh water for municipal and industrial use. In arid areas fresh water use is currently already in excess of sustainable quantities. Irrigated acreage in the western U.S. and many other regions is already declining due to reductions in delivered water. Soil salinization is still increasing throughout the world. Improvements in irrigation efficiency and leaching control are possible and essential, but they provide only a partial solution to sustaining irrigation and its high crop production. Almost all arid regions have abundant quantities of low-quality saline, drainage and sewage waters, most of which could potentially be used for irrigation. Use of these waters for irrigation is possible but requires new strategies for water management including new knowledge of factors affecting infiltration and crop production. We also need the development of models that consider the numerous interactions of chemical, physical and biological processes, enabling evaluation of various management practices. We need to develop alternative crops, and new varieties that are tolerant to salinity, ion imbalances and toxic elements. Water quality criteria were developed with the idea of being simple and designed to avoid problems in most instances. We currently reject waters that in some instances can be detrimental and without consideration that in many areas the water requirements can be met by a combination of rain, fresh water and saline water, thereby diminishing the salinity impact. In many instances use of recycled and brackish water, currently considered unsuitable, will result in some reduction in potential yield. Nonetheless this can be acceptable and desirable if yield is considered in the context of society needs and grower profitability. Treated wastewaters have elevated pH, alkalinity, and sodium, relatively low Ca/Mg ratios, high concentrations of dissolved organic matter, all adverse to infiltration and soil structure, as well as ion imbalances and potentially toxic elements. Use of these waters may require periodic application of amendments and/or leaching, utilizing new knowledge about factors affecting infiltration and crop production. Environmental concerns about recycled water include plant uptake of toxic elements, pharmaceuticals, endocrine disrupters etc. as well as off-site impacts to discharge areas. Existing guidelines consider only salinity and sodicity (SAR). The high variability in soil stability is related to the many factors that affect stability, among them pH, oxide content, organic matter, tillage, residue management, soil texture and clay mineralogy. Other factors that affect water suitability include irrigation system, rainfall-quantity, intensity and seasonal distribution, evoptranspiration demands, soil hydraulic conductivity, drainage system, uniformity of irrigation and acceptable relative yield- an economic consideration. Water suitability for irrigation and sodicity hazard related to infiltration has been established primarily from laboratory experiments, almost all based on short term column experiments of saturated hydraulic conductivity with waters of decreasing electrical conductivity (EC) and constant sodium adsorption ratio (SAR). Fortunately these data correlate with longer term infiltration experiments. We recently conducted year- long outdoor studies with conditions of combined simulated rain and irrigation and wetting and drying cycles with waters of varying SAR and electrical conductivity of either 1.0 and 2.0 dS/m, and varying pH. Rain has an adverse impact related to the SAR of the soil water at the time of infiltration. Based on these studies, we conclude that when considering rain a |
