SALINITY AND TRACE ELEMENTS ASSOCIATED WITH WATER REUSE IN IRRIGATED SYSTEMS: PROCESSES, SAMPLING PROTOCOLS, AND SITE-SPECIFIC MANAGEMENT
Location: Water Reuse and Remediation
Title: The chemistry of salt-affected soils and waters
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: September 1, 2011
Publication Date: January 2, 2012
Citation: Suarez, D.L., Jurinak, J.J. 2012. The chemistry of salt-affected soils and waters. In: Wallender, W.W. and Tanji, K.K. (eds.) ASCE Manual and Reports on Engineering Practice No. 71 Agricultural Salinity Assessment and Management (2nd Edition). ASCE, Reston, VA. Chapter 3 pp. 57-88.
Knowledge of the chemistry of salt affected soils and waters is necessary for management of irrigation in arid and semi-arid regions. In this chapter we review the origin of salts in the landscape, the major chemical reactions necessary for prediction of the soil solution composition, and the use of this information for crop production and maintenance of adequate soil physical properties. Among the important considerations are the presence of gypsum in the soil, the exchangeable sodium content and the electrical conductivity. Prediction of the major ion chemistry of the soil water under irrigation of arid land soils can be well represented by consideration of the following processes: Cation exchange, calcite and gypsum dissolution and precipitation and evapotranspiration. The inputs include quantity of water applied, crop water demands, composition of the irrigation water and initial soil water composition, if the time frame of interest is short. Consideration must also be made for adsorption-desorption reactions for potentially toxic elements such as boron, and changes in ion mobility due to changes in oxidation state for elements such as arsenic and selenium. We describe both use of computer models for prediction of soil solution composition and plant response, as well as simple methods for evaluating individual parameters such as sodium adsorption ratio.