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Land application of biosolids on the basis of crop N needs typically applies P far in excess of crop P needs. This excess P can cause pollution problems, especially in very sandy soils with limited P retention capacity. Water treatment residuals (WTRs) are largely amorphous Fe and Al
hydroxyoxides capable of retaining large amounts of P. Our objective was to determine the effect of two WTRs on P solubility, mobility, and bioavailabilty when co-applied with various biosolids-P sources. Laboratory studies confirmed the huge P-sorbing capacity of two Fe- and Al-WTRs. Adding
either WTR to soil suspensions fertilized with fertilizer or three biosolids P-sources dramatically reduced soluble P at WTR rates as low as <1 % by weight. Biosolids produced with biological P removal (BPR) techniques can contain appreciable leachable P. Greenhouse leaching studies
confirmed the usefulness of the WTRs in controlling P leaching under extreme conditions of high soluble P loads (from a BPR biosolids and a fertilizer) applied to a very poorly P-sorbing soil. Rates of WTRs needed to control soluble P are related to the oxalate-extractable Fe and Al content
of the WTR and the P-source rather than total elemental composition. A Phosphorus Saturation Index (PSI) can be calculated and used to predict P leaching potential for P-sources and mixtures of P-source and WTR. Additions of Fe- or Al-WTRs appear to limit soluble P by adsorption and/or
precipitation reactions (conversion of KCl-extractable P to NaOH-extractable P “forms” ) of limited reversibility. Decreases in soluble P reduce susceptibility of added P to leaching losses, and reduce plant uptake of P. However, a WTR rate of 2.5 % (˜50 Mg ha−1)
dramatically reduced P leaching loss and reduced P uptake without detrimentally affecting bahiagrass yield or nutritional value.
Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.