Submitted to: Suelos Ecuatoriales
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 2, 2006
Publication Date: N/A
Interpretive Summary: Scarcity of fresh water in arid regions means that we must evaluate the use of less desirable, more saline supplies for irrigation. Existing criteria are not adequate as they are generalized, with the objective of avoiding infiltration or yield loss in all instances. Site specific evaluation requires consideration of water quality and quantity, climate, management practices, soil properties and crop selection. We demonstrate the utility of the UNSATCHEM model to evaluate the impact of different management practices including use of cyclic fresh and saline drainage water, and irrigation with high boron water. Scenarios are provided where water considered unsuitable for irrigation can be utilized under specified conditions. Such analysis will provide the framework for successful use of lower quality waters for irrigation.
Technical Abstract: In arid regions the use of saline and reclaimed waters for irrigation is increasingly necessary. Scarcity of fresh water for agriculture is increased by the water demands of the municipal and industrial sectors. In the majority of these regions there is a rapid decrease in fresh water availability and overuse of existing supplies, thus the current irrigation practices are not sustainable. In order to maintain agricultural productivity and irrigation, it is essential that we improve overall efficiency, such as by use of drip irrigation, but this by itself will not be sufficient. It will be necessary to use water of lower quality, saline waters, agricultural drainage waters, and municipal waste waters for irrigation. Use of these waters will require new strategies for water use and management. In many regions, water requirements can be satisfied by a combination of rain, fresh water and brackish or saline waters. In these situations it will be necessary to periodically reclaim the soil by leaching or apply amendments for sodicity and toxic element control. Proposed practices must be economically efficient and the resultant drainage must minimize the degradation of receiving waters. At this time there exist many water classification systems for irrigation water quality. By necessity these general criteria are cautious and overly simplistic, with the objective of avoiding infiltration problems and loss of yield in all cases. In reality, the determination as to whether or not a water is suitable for irrigation depends on many factors and is to be distinctly determined in each case or location. Process based models, such as UNSATCHEM are well suited for evaluating water suitability and irrigation management impacts on relative plant yield. Examples are presented of management plans and analysis of yield with limited use of fresh water cycled with more saline water drainage water, and impacts of different management practices on soil boron levels when irrigation with waters of elevated boron concentration are utilized.