Relating Turfgrass Growth and Quality to Frequently Measured Soil Nitrate

Currently, there is no soil-based N test used to guide N fertilizer recommendations for turfgrass. This study was conducted across 3 yr in Connecticut to determine if frequent measurement of soil nitrate–N (No3–N) could be used to estimate color, density, clippings yield, clippings total N concentration, and clippings N uptake in Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns. randomized complete block field experiments were set out on the two species with nine N rates. Soil cores and clippings were collected at 2-wk intervals from May through october and analyzed for concentrations of No3–N and total N, respectively. Turfgrass color was measured with chlorophyll and normalized difference vegetative index meters, and shoot count density was measured after the last sampling. Significant (p < 0.001) Cate-Nelson, linear-plateau, and quadratic-plateau models were observed for all relative measures of turfgrass growth and quality as a function of soil No3–N concentrations. The critical soil No3–N concentrations for the three models that indicated the beginning of a plateau response or marked the Cate-Nelson change point between likely or unlikely response ranged from 3.7 and 18.0 mg kg-1 for Kentucky bluegrass and from 2.5 and 10.1 mg kg-1 for tall fescue. probability plots indicated a high likelihood of acceptable turfgrass responses at the lower range of the critical concentrations suggested by the Cate-Nelson model. These results suggest that frequent measurement of soil No3–N may help to guide N fertilization of Kentucky bluegrass and tall fescue when managed as lawns. Dep. of Plant Science and Landscape Architecture, Univ. of Connecticut, 1376 Storrs Road, Unit 4067, Storrs, CT 06269-4067. Received 5 Mar. 2013. *Corresponding author (karl.guillard@uconn.edu). Abbreviations: AEM, anion-exchange membrane; AIC, Akaike information criterion; C-N, Cate-Nelson; CL, critical level; CNUP, clippings total N uptake; CTN, clippings total N concentration; DMY, clippings dry matter yield; LRP, linear-response plateau; NDVI, normalized difference vegetative index; PSNT, pre-sidedress nitrate test; QRP, quadratic-response plateau. Published in Crop Sci. 54:366–382 (2014). doi: 10.2135/cropsci2013.03.0145 Freely available online through the author-supported open-access option. © 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. Published November 12, 2013