ARS | Publication request: Nutrients and nonessential elements in soil after 11 years of wastewater irrigation

Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2012
Publication Date: March 7, 2012
Citation: Faria, P.B., He, Z.L., Stoffella, P.J., Melfi, A.J., Baligar, V.C. 2012. Nutrients and nonessential elements in soil after 11 years of wastewater irrigation. Environmental Quality. 41:920-927.

Interpretive Summary: Success of perennial crops under prolonged drought depends on providing supplemental irrigation. Reuse of urban reclaimed wastewater (RWW) appears to be an attractive alternative where availability of fresh water is a problem. Even though RWW is a good source of plant essential nutrients, concerns remain regarding its effects on soil quality. Field research was undertaken to evaluate long term effects of RWW as compared to well water (WW)on soil quality under citrus trees. Although RWW irrigation affected the majority of evaluated soil quality parameters, the risk of negative impact from RWW irrigation on soil quality appears to be minimal. In years of prolonged drought irrigation of perennial crops with RWW appears to be beneficial in saving the crops from drought damage and additional benefits include saving fresh water and fertilizer cost. Findings of this study are very useful to sustain the productivity of perennial crops in areas where droughts are occurring very frequently thereby keeping steady economic returns for resource poor farmers of tropical region. Information obtained from this research will be used by researchers, plant breeders, extension personnel and farmers who are developing and using methods to reduce the impact of drought on cacao

Technical Abstract: Irrigation of citrus (Citrus aurantium L. x Citrus paradise Macf.) with urban reclaimed wastewater (RWW) can reduce its disposal costs and save fresh water. However concerns remain regarding its effects on soil quality. We investigated the ionic speciation of RWW and the potential impacts of 11 years of irrigation with RWW on soil quality, as compared with irrigation with well-water (WW). Most of nutrients (~53-99%) in RWW are free and readily available for plant uptake as: NH4+, NO3-, K+, Ca2+, Mg2+, SO42-, H3BO3, Cl-, Fe2+, Mn2+, Zn2+, Co2+,and Ni2+, whereas over ~80% of Cu, Cr, Pb and Al are complexed with CO3-, OH- and/or organic matter. The RWW irrigation increased the availability and total concentrations of nutrients and nonessential elements, and the soil salinity and sodicity by 2-3 times. Although, RWW irrigation affected the majority of evaluated soil parameters, but 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) the high quality of the RWW; ii) the low concentrations of metals in the soil after 11 years of irrigation with RWW; and iii) the rapid leaching of salts in the RWW irrigated soil during the rainy season.