A review of the effects of wastewater sodium on soil physical properties and their implications for irrigation systems

Abstract

This paper reviews the effects of wastewater sodium on soil physical properties, particularly with respect to irrigation systems. Fundamental sodicity concepts are examined including (i) sodicity definitions, (ii) the effects of sodium on soil properties, (iii) a discussion of factors that impede the infiltration rate and hydraulic conductivity, (iv) the changes that occur in ionic strength of percolating water in soil, and (v) consideration of the wastewater and soil constituents that modify the effective sodium adsorption ratio. Importantly, the ability for soils to assimilate wastewater over time changes, but these changes are not often considered prior to the planning of such irrigation systems, or after the irrigation systems are operating. The general lack of understanding of sodicity is in part due to the considerable variation in sodicity definitions. Exchangeable sodium percentage (ESP) values that are reported to pose a sodicity problem vary around the world due to the different mineralogy of the soils investigated, but variations in threshold ESP values have also been caused by a lack of consideration of the solution electrolyte concentration when determining ESP. In practice, the effects of sodicity may be evident in soils that are well under reported threshold values. When the effects of sodicity are identified, the landholder at least has the opportunity to implement remediation practices. However, more often than not, the effects of sodium from irrigation water are latent, leading to considerable problems following the cessation of effluent irrigation and changed land use.

Wastewater Reuse in Agriculture: A Review about Its Limitations and Benefits

“…Sodicity is caused by expansive and dispersive processes on clays as a consequence of the destruction of aggregates due to high Na + concentrations [109,110]. Different research studies noted that changes in sodicity generate an increase in soil compaction and reduce the infiltration rate of water [108,109,111].…”

Soil Chemistry after Irrigation with Treated Wastewater in Semiarid Climate

“…One of the main problems associated with irrigation using wastewater is an increase in soil exchangeable Na, as Na is present in high concentrations in wastewater (Hayes et al, 1990;Papadopoulos and Stylianou, 1991;Bond, 1998;Magesan et al, 1999;Jnad et al, 2001). Sodification processes cause disaggregation of the soil clay fraction due to an interlayer cationic replacement by Na + ions (Halliwell et al, 2001). The monovalency of the Na ion and its large hydration sphere further facilitate dispersion of the clay (Balks et al, 1998), which may then lead to a reduction in hydraulic conductivity (Magesan et al, 1999;Shainberg et al, 2001;Bagarello et al, 2006) and decrease permeability (Meenner et al, 2001), drainage, and soil aeration (McBride, 1989).…”

Irrigation of paddy soil with industrial landfill leachate: impacts in rice productivity, plant nutrition, and chemical characteristics of soil

“…Among the most common problems are the contamination of groundwater by nitrate, increasing the soil salinization promoting sodification of the soil. The consequences of sodicity find manifestation in the deterioration of soil structure, the decrease in soil permeability, and osmotic changes promoting lower productivity, and in some cases, plant toxicity (Oster and Schainberg 2001;Halliwell et al 2001).…”