Mitigating Soil Phosphorus Release Using Liquid Water Treatment Residuals

Abstract

Water treatment residuals (WTRs) have been land‐applied at 20% solids to reduce phosphorus (P) release, but liquid WTRs (2% solids) may be more effective. Our objectives were to show the variability of phosphorus release within a field treated with solid WTRs, determine an optimal application rate for liquid WTRs, and evaluate the long‐term effectiveness of that rate. Six liquid WTR treatment rates (220–4,400 kg/ha) were applied in triplicate to soil cores at varying soil test phosphorus (STP) levels and then flooded. Soluble reactive phosphorus was measured in overlying water, release rates were calculated, and the soil was analyzed for Mehlich‐III and water extractable phosphorus. Release rates were highly variable (2–14 mg/m2/h) within a WTR‐treated field. A small application rate (440 kg/ha) was sufficient to control release at an STP level <100, but greater or repeated application may be necessary for long‐term control.