Agronomy Journal • Volume 106, Issue 5 • 2014 1667 Agronomy, Soils & Environmental Quality Effects of Seasonal Nitrogen on Binary Mixtures of Tall Fescue and Bermudagrass John J. Read,* David J. Lang, and Ardeshir Adeli Published in Agron. J. 106:1667–1676 (2014) doi:10.2134/agronj13.0517 Copyright © 2014 by the American Society of Agronomy, 5585 Guilford 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 information storage and retrieval system, without permission in writing from the publisher. ABSTRACT Using poultry litter responsibly in cool-season/bermudagrass [ Cynodon dactylon (L.) Pers.] production systems may require supplemental N fertilization. is study determined if productivity in binary mixtures of tall fescue [Schedonorus arundina- ceus (Schreb.) Dumort] and bermudagrass could be improved through applying litter and fertilizer N to coincide with seasonal growth activities. e effects of N timing on dry matter (DM) yield, forage N and P contents, and fescue percent stand were investigated in binary mixtures that comprised two tall fescue cultivars, Flecha MaxQ (summer-dormant) and Jesup MaxQ (summer-active) drill-seeded in 2007 into swards of Russell and Tiſton 44 bermudagrass. ree seasonal N treatments were each comprised of 8.6 Mg litter ha –1 (as-is moisture basis) split into two applications per season with additional 168 kg N ha –1 split into three applications. Based on two spring harvests (April and May), forage DM yield was greater (P < 0.01) for October/Janu- ary treatment that applied N before April than January/March treatment that applied N in January–July (7.0 vs. 3.0 Mg ha –1 , 2 yr averages). Tall fescue stand count in May was greatest in October/January treatment and was greater in Jesup–Tiſton 44 than Flecha–Tiſton 44 in 2010 (79 vs. 59%). Based on five annual harvests, October/January treatment had the greatest cumulative N uptake of 189 and 182 kg ha –1 in 2009 and 2010, respectively, and uptake was generally least in Flecha–bermudagrass associa- tions. Results suggest N application timing to favor tall fescue increased the utilization of applied N and P. J.J. Read and A. Adeli, USDA-ARS, Genetics and Precision Agriculture Research Unit, Mississippi State, MS 39762; and D. J. Lang, Dep. of Plant and Soil Sciences, Mississippi State Univ., Mississippi State, MS 39762. Mississippi Agric. and Forestry Exp. Stn. Journal Article no. J-12429. Mention of trade names or commercial products is solely for the purpose of providing specifc information and does not imply recommendation or endorsement by the USDA. USDA is an equal opportunity provider and employer. Received 1 Nov. 2013. *Corresponding author (john.read@ars.usda.gov). Abbreviations: DM, dry matter; ICP–OES, inductively coupled argon plasma optical emission spectrometer. Growth of the broiler chicken industry in the southeastern United States and land application of broiler litter has focused research on nutrient uptake of southern forages, particularly bermudagrass (warm-season, C 4 ) and tall fescue (cool-season, C 3 ). Both species are perennial grasses that are characterized as having high growth rates under high fertility and extensive rooting systems, which makes them valuable in nutrient recycling systems; the nutrients taken up by the crop are removed when the hay is harvested (Newton et al., 2003; Read et al., 2010). Traditionally, broiler litter application has been based on yield goals and knowledge of crop N utilization from the manure, but not all of the nutrients in the litter are plant available (Sims and Wolf, 1994; Marshall et al., 2001). Imbal- ances between the quantity of nutrients applied in litter and the relative inefciency in nutrient utilization by crops contributes to build-up of soil nutrients, particularly P (Robinson, 1996; Sistani et al., 2004). A recommended practice is to apply nutrients, par- ticularly mobile nutrients like N, in phase with crop demands to stimulate growth and reduce nutrient loss from the system (Read et al., 2006; Mississippi Natural Resources Conservation Ser- vice, 2013). In a Mississippi study, a split application of 9.0 Mg litter ha –1 (as-is moisture basis, ~220 kg mineralizable N ha –1 ) to cultivar Alicia bermudagrass in April and June resulted in a 17% increase in DM yield, as compared to a single application in April, when minimum air temperatures were still below those required for optimum growth of warm-season forages (Brink et al., 2002). Te central role of temperature on the performance of cool- and warm-season forage grasses suggests N applications (either organic or inorganic) during the cool-season, October– January, should match the seasonal growth activity of tall fescue; whereas, N applications during the warm-season, March–May, should match the seasonal growth activity of bermudagrass. Tall fescue has vigorous growth in the spring (April–May) and autumn (October–December, if soil moisture is adequate) in the southeastern United States. It produces short rhizomes, but has a bunch-type growth habit, spreading chiefy by erect tillers. In contrast, bermudagrass has vigorous growth in late- spring and summer (May–October) and produces both stolons and rhizomes, enabling it to spread rapidly. Grazing mixed tall fescue and bermudagrass swards is commonly practiced, but the practice of harvesting hay from this mixture in a nutri- ent management scheme has received little attention (Pitman, 1999; Marshall et al., 2001; Broome et al., 2002). Nevertheless, Published September 24, 2014