Submitted to: International Meeting on Advances in Micro-Irrigation Proceedings
Publication Type: Monograph
Publication Acceptance Date: 1/1/2005
Publication Date: 12/1/2005
Citation: Suarez, D.L. 2005. Management practices for use of degraded waters for irrigation: modeling and field results. In: Agricultural Monograph Series No. 17, Advances in Mirco-irrigation. INIA Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, Tenerife, Canary Islands. pp:63-80. Interpretive Summary: The increasing demands on our fresh water supplies means that irrigated agriculture will need to utilize low quality waters for irrigation, such as drainage waters and treated municipal effluent. These waters are typically high in salinity and potentially toxic elements. Use of these waters will require new management practices and improved analytical tools, such as computer models, to evaluate these practices and predict short and long term consequences. This paper examines the use of the computer model UNSATCHEM as a management tool. Examples are given for management of crop production with limited fresh water including supplemental irrigation with water containing elevated levels of salinity. Comparison of the model results to field data were excellent, the model was well able to predict drainage volume, no loss in crop yield and soil salinity with depth after 2 years of cropping with cyclic use of fresh and saline water. The model was also able to predict boron adsorption and desorption from a column study. An example is given of how the model can be used to optimize irrigation when using a high B containing water; the extent to which high or low leaching fractions are beneficial is shown to depend on the boron adsorption capacity of the soil.
Technical Abstract: Use of saline waters for irrigation in arid regions is increasingly necessary due to scarcity of fresh water. In most arid regions there is currently a rapid depletion of fresh water supplies, thus irrigation as practiced is not sustainable. In order to maintain agricultural productivity improved water use efficiency such as conversion to drip irrigation is essential but not sufficient. Use of low quality saline, drainage and sewage waters for irrigation will be necessary. This will require new strategies for water management. In many areas the overall water requirements can be met by a combination of rain, fresh water and saline water. In some instances periodic reclamation of the soil or continuous application of amendments will be necessary to control salinity sodicity and toxic element concentrations. These practices must be economically efficient and minimize degradation of waters receiving the subsequent drainage water. Computer models such as UNSATCHEM are well suited to analyze the performance of various management practices. Examples are given for management of crop production with limited fresh water including supplemental irrigation with water containing elevated levels of salinity, elevated levels of boron and reclamation of a saline sodic soil.