Maria Lucia A. Silveira, Range Cattle Research and Education Center, University of Florida, Ona, FL, Joao Vendramini, UF/IFAS Range Cattle Research and Education Center, Ona, FL and Lynn E. Sollenberger, 3105 McCarty Hall B, PO Box 110500, University of Florida, Gainesville, FL
Phosphorus management in agricultural systems continues to be a relevant issue of agronomic and environmental importance. The objectives of this study were to i) investigate the potential P-removal capacity of four bioenergy crops [(elephantgrass (Pennisetum purpureum Schum.), sugarcane (Saccharum spp.), switchgrass (Panicum virgatum L.), and stargrass (Cynodon nlemfuensis Vanderyst)] grown on a manure-enriched soil, and ii) examine the impacts of crop P uptake on soil P concentrations and surface groundwater quality. Treatments were distributed in a completely randomized design with four replicates. The greatest dry matter (DM) yields were observed for elephantgrass (average of 46 Mg ha-1 yr-1) followed by sugarcane (average of 40 Mg ha-1 yr-1). Tissue P concentrations were greater for stargrass (~ 4 g kg-1) as compared to elephantgrass (3.2 g kg-1) and sugarcane (1.9 g kg-1). Elephantgrass showed the greatest cumulative P removal (420 kg P ha-1 during the 3-yr period). Soil P concentrations in the Ap horizon decreased over time, while an increase in soil P concentration was observed in the Bh horizon. Elephantgrass resulted in the lowest leachate P concentrations (~0.5 mg P L-1) at 60-cm depth. Crop species had no effect on leachate P at the 90-cm depth. Growth of elephantgrass as a biofuel feedstock appears to be an effective approach for remediation of excess soil P.