Phosphorus Management Agronomy Journal  Volume 101, Issue 6  2009 1345 Published in Agron. J. 101:1345–1351 (2009) Published online 26 Aug. 2009 doi:10.2134/agronj2009.0163 Copyright © 2009 by the American Society of Agronomy, 677 South Segoe Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any in- formation storage and retrieval system, without permission in writing from the publisher. P hosphorus is regarded as one of the most critical nutrients in manure relative to potential environmental impact, and its movement from soils to surface and ground- water via runof and/or leaching can result in eutrophication even at relatively low concentrations (Harris et al., 1994; Whitehead, 2000; Boruvka and Rechcigl, 2003). Warm-season grasses have been recognized as environmental bioremedia- tion agents for ameliorating the environmental impact of excess soil nutrients (Pant et al., 2004). he high productivity of these grasses and their long-term persistence are attrac- tive attributes for their use in phytoremediation (Burns et al., 1990). Grasses tend to outperform legumes in DMY and nutrient uptake when dairy manure is applied (Newton et al., 2003). Despite evidence of nutrient removal by forages from di ferentially impacted soils (Sanderson and Jones, 1997; Brink et al., 2008; McLaughlin et al., 2005), it is important to assess the potential of management options to enhance yield and increase soil nutrient removal. Data of these kind have particular relevance for producers who are afected by envi- ronmental regulations and need further information to guide implementation of management practices that have less impact on the environment. Bahiagrass, a warm-season perennial, is grown in Florida on approximately one million hectares, and is the most-planted perennial warm-season forage in the state (Kalmbacher et al., 2005). Floralta limpograss is another warm-season perennial grass used widely by producers in wet latwood environments (Sollenberger et al., 1989; New- man, 2008). he efects of N fertilizer on herbage yield and nutritive value has been studied intensively for warm-season grasses. Typically, grass production and nutritive value increase with increasing levels of N fertilization (Lima et al., 1999; Vendramini et al., 2008). his response to N fertilizer may provide options for increasing removal of soil P from impacted sites. Stanley and Rhoads (2000) found highest soil P concentration (49 mg kg –1 ) for bahiagrass in North Florida that was not N fertilized compared with rates of 336 kg N ha –1 . Intensively managing forages for hay production there- fore represents a feasible option for remediating P-impacted soils due to the potential for high DMY that can be increased with N fertilization (Burton et al., 1999). he impact of N fertilization on forage P removal and subse- quent efect on residual soil-P concentrations in impacted soils has not been documented for South Florida. he objectives of this study were to evaluate the efect of increasing N fertilizer level on grass productivity and phytoremediation of P-impacted soils in South Florida. Speci ic objectives were to (i) determine DMY response to increasing N fertilizer rates of warm-season forage species (bahiagrass and limpograss) commonly used on South Florida ranches; (ii) determine the P-removal potential of the forages across a range of N rates; and (iii) assess P in leachate at the selected sites. ABSTRACT Phytoremediation or use of plants to extract soil nutrients is a practice used to ameliorate the impacts of excessive soil nutri- ents. Pensacola bahiagrass (Paspalum notatum Flügge) and ‘Floralta’ limpograss [Hemarthria altissima (Poir.) Stapf & Hubb] were grown in a P-impacted Immokalee ine sand (Mehlich-1 P ≈ 30 mg P kg –1 ) to evaluate increasing N levels on dry matter yield (DMY), forage P concentration, P removal, and P dynamics in the soil proile. Treatments were four levels of N fertiliza- tion (0, 50, 67, and 101 kg N ha –1 harvest –1 ) replicated four times for each species. Both grasses showed increases in P removal with increasing N fertilizer applications. Phosphorus removed by forages for the highest N application level ranged from 59 (bahiagrass; 2-yr period) to 83 kg ha –1 (limpograss; 3-yr period). he initial soil P content of the Ap horizon of all N > 0 treat- ments decreased by ≥85% over the study period. However, more P from the control (N = 0) plots leached to subsurface horizons compared to P lost from the plots receiving N fertilizer. Nitrogen application enhanced P uptake from the soil and consequently reduced of-site P losses from the surface soil. Nitrogen application of 67 kg ha –1 harvest –1 optimized P removal by bahiagrass and limpograss. hese data show that well managed, warm-season perennial forage grasses with adequate N fertilization and managed for hay production or greenchop are an option for reducing of-site P losses from P-impacted soils. Y.C. Newman and L.E. Sollenberger, Agronomy Dep., and S. Agyin- Birikorang and M. Chrysostome, Soil and Water Sci. Dep., Univ. of Florida, Gainesville, FL 32611; M. Adjei (deceased), M.L. Silveira, and J.M.B. Vendramini, UF/IFAS Range Cattle REC, Ona, FL 33865; J. Rechcigl, UF/IFAS Gulf Coast REC, Wimauma, FL 33598. Received 23 Apr. 2009. *Corresponding author (ycnew@ul.edu). Abbreviations: DM, dry matter; DMY, dry matter yield; PO 4 –P, orthophosphate P. Enhancing Phosphorus Phytoremedation Potential of Two Warm-Season Perennial Grasses with Nitrogen Fertilization Y. C. Newman,* S. Agyin-Birikorang, M. B. Adjei, J. M. Scholberg, M. L. Silveira, J. M. B. Vendramini, J. E. Rechcigl, L. E. Sollenberger, and M. Chrysostome Published November, 2009