Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. 1178 CROP SCIENCE, VOL. 48, MAY–JUNE 2008 RESEARCH S t. Augustinegrass [ Stenotaphrum secondatum (Walt.) Kuntze] is a popular choice for lawns throughout the southern United States. It is believed to be native to the Caribbean, African and Mediter- ranean regions, and best adapted to subtropical climates. It grows best in full sun and long daylength, but most cultivars have a high tolerance for shade compared to other warm-season turfgrasses. St. Augustinegrass grows quickly during the summer months, but slows during the spring and fall and may enter a dormancy period during the winter months if temperatures drop below freezing. Due to poor wear tolerance, St. Augustinegrass is used primarily for lawns and general purpose turf, but not for high trafc sports turf (Trenholm et al., 2006). It can grow satisfactorily in a wide variety of soils (Trenholm et al., 2006). St. Augustinegrass requires moderate to high nitrogen fertilization to maintain good visual quality and vigor, with recommendations for other nutrient fertil- ization based on soil test results (Trenholm et al., 2006). The most essential function of P in plants is energy storage and transfer. Phosphorus is also an important structural compo- nent of nucleic acids, coenzymes, nucleotides, phosphoproteins, phospholipids, and sugar phosphates. Phosphorus plays an essen- tial role in plants; therefore, total elimination of P fertilization due to environmental concerns is not justifed. Plants absorb Phosphorus Requirements of St. Augustinegrass Grown in Sandy Soils Min Liu, J.B. Sartain,* L.E. Trenholm, and G.L. Miller ABSTRACT Phosphorus fertilization of St. Augustinegrass [Stenotaphrum secondatum (Walt.) Kuntze] is performed on the basis of soil tests designed for agronomic crops. The objectives of this study were to determine the critical minimum P application rate and soil and tissue P concentra- tion of St. Augustinegrass grown in sandy soils. Three studies were conducted in a glasshouse using a Pomona sand, two Tavares sands, and a Pottsburg sand. Established pots of ‘Flora- tam’ St. Augustinegrass received P at 0, 0.14, 0.27, 0.54, and 1.09 g m –2 every four weeks for 16 weeks for Study 1 and 12 weeks for Studies 2 and 3. Critical minimum tissue P concentration was determined to be 1.8 g kg –1 on dry weight basis. Minimum P application rate was 0.14 g m –2 4-wk –1 to obtain acceptable turfgrass quality and growth rate. Additional growth was not observed when Mehlich-1 P level was greater than 7, 8, 9, and 5 mg kg –1 for Pomona sand, Tavares sand (a), Pottsburg sand, and Tavares sand (b), respec- tively. Phosphorus fertilization would not be rec- ommended if soil Mehlich-1 P concentration is above 10 mg kg –1 for sandy soils or tissue P level is beyond 1.8 g kg –1 on dry weight basis. Phos- phorus application of 0.14 g m –2 4-wk –1 is recom- mended when P is required. M. Liu, College of Resources and Environment Science, China Agri- cultural Univ., Beijing, China, 100094; J.B. Sartain, Soil and Water Science Dep., Univ. of Florida, 414 Newell Hall, P.O. Box 110510, Gainesville, FL 32611-0510; L.E. Trenholm, Environment Horticul- tural Dep., Univ. of Florida, Gainesville, FL 32611-0670; G.L. Miller, Crop Science Dep., North Carolina State Univ., Raleigh, NC 27695; Received 27 Dec. 2007. *Corresponding author (sartain@uf.edu). Published in Crop Sci. 48:1178–1186 (2008). doi: 10.2135/cropsci2007.09.0506 © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA 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 information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Published May, 2008