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Nutrients and Nonessential Elements in Soil after 11 Years of Wastewater Irrigation

Pereira, B. F. Faria, He, Zhenli, Stoffella, Peter J., Montes, Celia R., Melfi, Adolpho J., Baligar, Virupax C.
Journal of environmental quality 2012 v.41 no.3 pp. 920
Citrus aurantium, Citrus paradisi, aluminum, ammonium nitrogen, calcium, chlorides, chromium, cobalt, copper, crop yield, iron, irrigated soils, leaching, lead, long term experiments, magnesium, manganese, nickel, nitrate nitrogen, nutrient availability, nutrients, organic matter, potassium, risk, soil nutrients, soil quality, soil salinity, soil sodicity, sulfates, wastewater irrigation, wastewater treatment, water reuse, wet season, zinc
Irrigation of citrus (L. × Macf.) with urban reclaimed wastewater (RWW) can be economical and conserve fresh water. However, concerns remain regarding its deleterious effects on soil quality. We investigated the ionic speciation (ISP) of RWW and potential impacts of 11 yr of irrigation with RWW on soil quality, compared with well-water (WW) irrigation. Most of nutrients (∼53–99%) in RWW are free ionic species and readily available for plant uptake, such as: NH, NO, K, Ca, Mg, SO, HBO, Cl, Fe, Mn, Zn, Co, and Ni, whereas more than about 80% of Cu, Cr, Pb, and Al are complexed with CO, OH, and/or organic matter. The RWW irrigation increased the availability and total concentrations of nutrients and nonessential elements, and soil salinity and sodicity by two to three times compared with WW-irrigated soils. Although RWW irrigation changed many soil parameters, no difference in citrus yield was observed. The risk of negative impacts from RWW irrigation on soil quality appears to be minimal because of: (i) adequate quality of RWW, according to USEPA limits; (ii) low concentrations of metals in soil after 11 yr of irrigation with RWW; and (iii) rapid leaching of salts in RWW-irrigated soil during the rainy season.