Identifying factors controlling the continuous corn yield penalty

By Laura F. Gentry, M. Ruffo, F. Below. 2013

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Published in Agron. J. 105:295–303 (2013) Available freely online through the author-supported open access option. doi:10.2134/agronj2012.0246 Copyright © 2013 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. T USDA-Economic Research Service’s Regional Environmental and Agriculture Programming (REAP) model predicts that CC—i.e., planting corn on the same land for three or more consecutive years—will account for 30% of the total U.S. corn hectares by 2015 according to the baseline (“business as usual”) scenario and as much as 50% of corn hectares under the 57 billion L biofuel scenario presented by the enactment of the Energy Independence and Security Act (EISA) of 2007 (Malcolm et al., 2009). Th e EISA mandate has substantially increased domestic demand for corn grain. Meeting the EISA biofuel targets without loss of livestock, animal feedstock, or grain for human consumption will require additional increases in corn production on existing farmland (Mehaff ey et al., 2012). If projected increases for corn demand are substantiated, CC production will inevitably increase. Studies conducted during the past 40 yr have clearly established that yields are less when corn is grown continuously relative to a cropping rotation. Th e reduction in grain yields observed in CC systems is not clearly understood. Th is study was conducted to elucidate the source(s) of the yield loss commonly observed when corn is grown continuously relative to SC, a yield diff erence we designate as the CCYP. A greater understanding of the agents and mechanisms underlying the CCYP is needed as a result of domestic and international issues that are increasing the demand for U.S. corn grain. In a summary of 28 U.S. studies comparing CC with SC, Erickson (2008) determined that all but two studies resulted in a yield decrease for CC, with reductions ranging from 2 to 19%. Porter et al. (1997) combined data from 29 site-years in the northern Great Plains and determined that corn yields from SC rotations yielded 13% greater than CC systems. In a 4-yr study conducted by Peterson and Varvel (1989) in eastern Nebraska under rainfed conditions, corn yields were 29% greater for SC than for CC. Additionally, in a 16-yr study conducted in southeastern Nebraska under rainfed conditions, Wilhelm and Wortmann (2004) measured 22% greater yield for SC than CC. Nitrogen availability is oft en thought to play the dominant role in explaining the CCYP (Shrader et al., 1966; Baldock and Musgrave, 1980; Stanger and Lauer, 2008). Corn residue management, which aff ects plant-available N among other things, can also control the CCYP. Th e larger C/N ratio of corn residues and the greater quantity of biomass remaining aft er corn harvest compared with soybean production explains observations of reduced net soil N mineralization in CC systems (Kaboneka et al., 1997; Gentry et al., 2001). Additionally, increased residue-induced N immobilization (Varvel and Peterson 1990; Kaboneka et al., 1997) and diff erences in the timing of immobilization (Green and Blackmer, 1995) may also explain diff erences in N fertilizer ABSTRACT It is widely accepted that yields decline when corn (Zea mays L.) is grown continuously vs. in rotation with soybean [Glycine max (L.) Merr.], although causes for the yield reduction are unclear. Th e primary objective of this study was to elucidate the source(s) of the continuous corn yield penalty (CCYP). Th e experiment was conducted from 2005 to 2010 in east-central Illinois beginning with third-year continuous corn (CC) or a soybean–corn (SC) rotation at six N fertilizer rates. Averaged across all years, yield at the agronomic optimum N rate for CC was 8.84 Mg ha–1 and for SC was 10.20 Mg ha–1, resulting in a CCYP of 1.36 Mg ha–1; values ranged yearly from 0.47 to 2.23 Mg ha–1. Using a regression model, three signifi cant and independent predictors explained >99% of the variability in the CCYP: unfertilized CC yield (0NCCYD), years in CC (CCYRS), and the diff erence between CC and SC delta yields (maximum yield – unfertilized yield) (DELTADIFF). Th e strongest predictor, 0NCCYD, refl ects net soil N mineralization and demonstrates that it decreases in CC systems. Th e CCYRS was strongly and positively correlated with CCYP, indicating that the CCYP increased through Year 7. We believe that CCYRS measures the eff ects of accumulated corn residue in CC systems. Finally, we consider DELTADIFF to be a measure of the interaction between yearly weather patterns and crop rotation, which results in more negative yield responses for CC than SC under hot or dry conditions. Th is study concluded that the primary causative agents of the CCYP are N availability, corn residue accumulation, and weather.

Subfields: Agronomy and Crop Science, Ecology, Evolution, Behavior and Systematics, Soil Science

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