Aluminum-containing residuals influence high-phosphorus soils and runoff water quality

Phosphorus (P) loading in surface water can degrade water quality. Previous research has shown that soil test P levels are directly correlated to runoff P levels and that aluminum (Al) will bind P in the soil. Both water treatment residuals (WTR) and HiClay Alumina (HCA) are readily available waste materials high in Al. Water treatment residuals and HCA are by-products of the potable water treatment and commercial alum production process, respectively. Our objective was to determine if runoff P from fields excessively high in soil test P could be decreased by land applying these materials. Water treatment residuals and HCA were surface applied at rates of 0, 2.2, 9.0, and 18 Mg ha -1 to plots high in P. We used rainfall simulation to produce runoff 1 d, 1 mo, and 4 mo following application. The P adsorption capacity for the WTR was 20 times higher than HCA because it was predominantly clay (95%) and contained three times as much Al. High rates of WTR increased the total recoverable Al concentrations in the soil, whereas HCA had no effect. High rates of both materials decreased Mehlich III soil test P levels due to the increased levels of soil Al. The two highest rates of WTR decreased runoff P levels significantly below those of the control plots for all dates, whereas the two highest rates of HCA decreased P levels for only the first two dates. Relative to the control, runoff concentrations of either total or dissolved Al were not significantly increased by WTR.