Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 12/23/2008
Publication Date: 1/7/2012
Citation: Ayars, J.E., Corwin, D.L., Hoffman, G.J. 2012. Leaching and root zone salinity control. 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. p. 371-403. Interpretive Summary: Controlling salinity in arid irrigated areas is a significant problem throughout the world. The basic concept for salinity control is called leaching which is the application of water in excess of crop water requirements to move salinity out of the root zone. This chapter discusses the sources of salinity and identifies the major sources to be considered in salinity control. It then details the concepts related to root zone salt balance and the concept known as a leaching fraction. The management of shallow groundwater systems and how it impacts the root zone salinity is discussed. Disposal of saline drainage water from arid irrigated lands is a significant environmental problem that has begun to modify the approach taken to leaching by reducing the levels required to control salinity in the root zone. These concepts are also highlighted.
Technical Abstract: A detailed description of the salt balance index is provided with a discussion related to individual components and their importance in calculating the index. Major sources identified are fertilizers, geologic sources, irrigation water, and rainfall in specific areas. The concept of leaching fraction and leaching requirements are discussed in detail, and new concepts are evolved which go beyond the study state method previously used in calculating the leaching fraction. New concepts using transient state analysis for calculating the leaching requirement and leaching fraction are discussed. Shallow groundwater is a significant or can be a significant contributor to root zone salinity. Methods to determine the mass of salt contributed from a shallow groundwater are discussed. The effect in situ use of water by crops on root zone salt accumulation is highlighted along with management opportunities to control root zone salinity