CROP SCIENCE, VOL. 51, JANUARY– FEBRUARY 2011 353 RESEARCH ‘T ifton 85’ bermudagrass has become an important forage grass in the southeastern United States since it was released in 1992 (Burton et al., 1993). Forage dry matter (DM) accumula- tion and nutritive value of this grass are greater than other ber- mudagrass [ Cynodon dactylon (L.) Pers.] cultivars, including ‘Tifton 78’, ‘Coastal’, and ‘Florakirk’ (Hill et al., 1993; Mandebvu et al., 1999). As a result, Tifton 85 is increasingly used for hay produc- tion and grazed pasture. Grazing management afects forage production, DM intake, and digestibility as well as grazing behavior of ruminants (Wright et al., 1990; Prigge et al., 1997; Newman et al., 2002). There have been several studies evaluating grazing management of Tif- ton 85. Mandebvu et al. (1999) measured regrowth interval (RI) efects on Ti fton 85 and Coastal bermudagrass herbage accumu- lation. Herbage accumulation increased with increasing RI for both cultivars, and Tifton 85 outyielded Coastal by 34%. Mis- levy and Martin (1998) evaluated herbage accumulation and per- sistence responses of Tifton 85 and Florakirk bermudagrass and ‘Florona’ and ‘Florico’ stargrass ( Cynodon nlemfuensis Vanderyst) to regrowth interval (14, 28, 35, or 49 d) in south Florida. Herbage Grazing Management Efects on Productivity, Nutritive Value, and Persistence of ‘Tifton 85’ Bermudagrass K. Liu, L. E. Sollenberger,* Y. C. Newman, J. M. B. Vendramini, S. M. Interrante, and R. White-Leech ABSTRACT ‘Tifton 85’ bermudagrass (Cynodon spp.) is an important forage in the southern United States, but its responses to the interaction of grazing frequency and intensity have not been stud- ied. Sward persistence, herbage accumulation, and nutritive value were measured during 3 yr. Treatments were all combinations of three post- graze stubble heights (SH; 8, 16, and 24 cm) and three regrowth intervals (RI; 14, 21, and 28 d). Short SH (8 cm) with long RI (28 d) or tall SH (24 cm) with short RI (14 d) produced great- est herbage accumulation (11–15 Mg ha −1 yr −1 ). Lowest or nearly lowest herbage accumulation occurred with 14-d RI and 8-cm SH or 28-d RI with 24-cm SH (7.4–12 Mg ha −1 yr −1 ). Intermedi- ate levels of RI (21 d) or SH (16 cm) produced consistent herbage accumulation regardless of level of the other factor. Nutritive value was pri- marily affected by RI, and P (3.1 to 2.8 g kg −1 ), crude protein (CP; 150 to 108 g kg −1 ), and in vitro digestible organic matter (IVDOM; 602 to 582 g kg −1 ) concentrations decreased as RI increased. Organic matter and nutrient mass of storage organs increased with increasing SH, but the 24-cm SH treatment exhibited greater reduction in percentage cover (~43% units) than the other SH treatments (~22% units) after 3 yr of graz- ing. These data indicate that intermediate levels of SH (16 cm) and RI (21 d) provided relatively high Tifton 85 herbage accumulation and nutri- tive value while minimizing negative impacts on persistence-related responses. K. Liu, L.E. Sollenberger, and Y.C. Newman, Agronomy Dep., Univ. of Florida, Gainesville, FL 32611-0500; J.M.B. Vendramini, Range Cattle Research and Education Center, Ona, FL 33865; S.M. Interrante, The Noble Foundation, 2510 Sam Noble Pkwy., Ardmore, OK 73401; R. White-Leech, Natural Resource Conservation Service, LaBelle, FL 33935. Received 28 Feb. 2010. *Corresponding author (lesollen@ul.edu). Abbreviations: CP, crude protein; DM, dry matter; IVDOM, in vitro digestible organic matter; RI, regrowth interval; SH, postgraze stubble height; TNC, total nonstructural carbohydrate. Published in Crop Sci. 51:353–360 (2011). doi: 10.2135/cropsci2010.02.0122 Published online 25 Oct. 2010. © Crop Science Society of America | 5585 Guilford 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.