Land Application of Aluminum Water Treatment Residual to Bahiagrass Pastures: Soil and Forage Responses

Abstract

Phosphorus transport is an environmental concern, particularly in coarse‐textured soils with minimal P‐sorbing capability. This 2‐yr study evaluated the impact of an Al water treatment residual (Al‐WTR) application on soil P responses, leachate P concentrations, and bahiagrass (Paspalum notatum Flüggé) yield and nutritive value. Treatments were a factorial combination of three Al‐WTR levels (0, 35, and 70 Mg ha–1) and two methods of application (surface vs. incorporated), replicated four times in a randomized complete block design. Forage was harvested at 28‐d intervals from May to November 2007 and 2008 and analyzed for neutral detergent fiber and tissue mineral concentrations. Soil samples were collected in August 2006, before the Al‐WTR application, and in November 2007 and 2008. Shallow groundwater P was monitored using a piezometer installed at the 60‐cm depth. Soil water‐extractable P and leachate P concentrations decreased as Al‐WTR application level increased. Mehlich‐1 Al and soil P storage capacity values increased linearly as Al‐WTR application level increased. Soil disturbance due to incorporation of Al‐WTR resulted in horizontal P transport in the soil. Incorporation of Al‐WTR caused a yield suppression in Year 1 (∼11% compared with surface application), but no negative effect was observed in Year 2. Neutral detergent fiber and crude protein were not affected by Al‐WTR application level or method. Data indicate that Al‐WTR reduced P mobility in a Spodosol with no impact on forage responses except for a light reduction in yield in the first year if Al‐WTR was incorporated.