Nitrogen Use Effi ciency of Irrigated Corn for Three Cropping Systems in Nebraska

Published in Agron. J. 103:76–84 (2011) Published online 3 Nov 2010 doi:10.2134/agronj2010.0189 Copyright © 2011 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. N fertilizer will continue to be indispensible for meeting global food, feed, and fi ber needs. Voroney and Derry (2008) estimated that 340 million Mg yr−1 N is fi xed by natural means, including lightning and biological N fi xation, and 105 million Mg yr−1 is fi xed by human activities, including burning of fossil fuels and N fertilizer production, with N fi xation by human activities expected to continue to increase. Townsend and Howarth (2010) estimated the amount of N fi xed by human activities to be about 180 million Mg yr−1, with most used as mineral fertilizer. Fertilizer N production has important environmental implications with an average of ~2.55 kg CO2 emitted per kg fertilizer N fi xed and transported (Liska et al., 2009). Th e amount of N applied is associated with emission of N2O (IPCC–OECD, 1997) and N accumulation in sensitive aquatic, marine, and terrestrial ecosystems (Groff man, 2008; Malakoff , 1998). Th e challenge is to produce more grain to meet growing global needs with high NUE. Nitrogen use effi ciency, or grain production per unit of available N in the soil, is composed of the effi ciency of N uptake and of conversion of total UN to grain (Moll et al., 1982). Corn NUE has an impact on energy effi ciency, profi tability, water protection, and CO2 and N2O emission. High N requirement for high yield cereal systems can lead to substantial N losses to the environment and low NUE with suboptimal management and yields well below the attainable yield potential (Cassman et al., 2002). Globally, 46% of the N input for crop production is from inorganic fertilizers with biological N fi xation, atmospheric deposition, animal manure, and crop residues being major sources (Smil, 1999). Th e main factor aff ecting NUE is N application rate with excess N supply causing reduced NUE (Meisinger et al., 2008). Effi cient N recovery with minimal losses of N to denitrifi cation, leaching, and volatilization is important to NUE which in turn will improve natural resource protection and profi tability (Raun and Schepers, 2008). Th e potential for N loss increases as inorganic N, and especially NO3–N in the soil profi le increases (Cassman et al., 2002). Crop NUE is a function of effi ciency of recovery of indigenous soil nitrogen and applied nitrogen (RE), and internal effi ciency of nitrogen use within the plant (IE), specifi cally conversion of UN to grain. Uptake of indigenous soil N by the crop is important to NUE and includes uptake of N from RSN, net mineralization of N from soil organic matter (SOM) and crop residues, atmospheric N2 fi xation, wet and dry deposition of atmospheric NH4, and NO3–N in irrigation water. Considering RSN in formulating N recommendations for corn is common in subhumid corn production areas where risk of leaching and denitrifi cation loss ABSTRACT