High-Yielding Corn Response to Applied Phosphorus, Potassium, and Sulfur in Nebraska

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. O n-going improvement of nutrient recommendations for crops is necessary because of changes in yield levels, varieties and production practices, and economic conditions. In the western Corn Belt and Great Plains of the United States, many land-grant universities including the University of Nebraska–Lincoln (UN-L) have utilized the defi ciency correction approach to making nutrient recommendations. Soil tests are used with other production information to recommend nutrient application based on the probability of economic response. Th e basis for calibration of the Bray-1 P and Olsen P soil tests was published by Olson et al. (1954), with further refi nement of the interpretation of soil test results using later research results including diff erent rates for broadcast and band application (Shapiro et al., 2003). Current UN-L recommendations do not recommend P and K application for corn when Bray-1 P is greater than 15 mg kg –1 and exchangeable K is greater than 124 mg kg –1 , respectively. Recommended S application is limited to sandy soils with less than 10 mg kg –1 SOM and <8 mg kg –1 SO 4 –S by Ca(H 2 PO 4) 2 extraction. In studies conducted more than 20 yr ago, the UN-L recommendations for corn were found to be more profi table with less P, K, and S applied compared with recommendations based on nutrient replenishment or other approaches (Olson et al., 1982, 1987; McCallister et al., 1987). Th ese results verifi ed the UN-L P recommendations and there were no yield responses to applied K. Soil test calibration may be needed for high yield situations and current cropping and tillage systems. Current P and K recommendations were mainly based on research conducted when mean corn grain yields in Nebraska were less than 5 Mg ha –1 compared with the 2008 average of more than 10 Mg ha –1 (USDA-NASS, 2008) and with yields oft en exceeding 15 Mg ha –1. More recent research conducted in Iowa supports the current UN-L recommendations, although P application when Bray-1 P is between 15 and 20 mg kg –1 could be economical when the P fertilizer/corn price ratio is relatively low (Mal-larino and Blackmer, 1992; Webb et al., 1992). …