Soil Water , Soil Nitrate , and Corn Development

Published in Agron. J. 103:316–323 (2011) Published online 15 Dec 2010 doi:10.2134/agronj2010.0327 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. W rye is a recommended cover crop in cold climates as it is winter hardy and is able to begin regrowth early in the spring (Stoskopf, 1985). Rye is also a good choice when the cover crop is harvested for spring forage because it reaches optimum growth stage sooner than other small grains (Maloney et al., 1999). In the Upper Midwest region of the United States, rye has been shown to scavenge excess soil NO3–N (Jewett and Th elen, 2007) and reduce NO3–N leaching (Kaspar et al., 2007; Strock et al., 2004). Increased ground cover provided by the rye may also reduce soil erosion (Kaspar et al., 2001), while rye biomass may help maintain soil organic matter (Kaspar et al., 2006). Th ese environmental benefi ts make rye particularly useful in dairy operations where corn silage is the primary crop and manure is oft en applied in the fall. However, rye can decrease profi tability due to corn yield declines (Th elen and Leep, 2002), which may be one reason why adoption of rye cover crop systems has been limited (Singer et al., 2007). Th e impact of rye on corn production is infl uenced by rye management methods (Tollenaar et al., 1992). When used as a cover crop, rye can be chemically terminated before corn planting, but timing of termination infl uences the subsequent impacts on corn yield. Rye termination at corn planting can result in decreased corn yield (Johnson et al., 1998; Tollenaar et al., 1992), but when terminated a week or more before corn planting, corn yield similar to (Singer et al., 2008) or slightly greater than (Duiker and Curran, 2005) corn aft er winter fallow has been observed. When corn yield suppression aft er rye has occurred, reduced soil moisture (Raimbault et al., 1991), inadequate N (Tollenaar et al., 1993), rye residue (Raimbault et al., 1991), and allelopathic eff ects of rye on corn (Raimbault et al., 1990; Tollenaar et al., 1992) have been cited as reasons for the corn yield decline. Rye can be terminated earlier to limit resource depletion, prevent excess rye residue, and avoid possible allelopathic eff ects. When rye is used as a cover crop, environmental benefi ts are immediate and long-term economic benefi t is gained by conserving soil resources (Reicosky and Forcella, 1998), but the economic benefi t of rye as a forage is not achieved. In dairy or beef (Bos taurus) production systems, rye can be harvested as high quality spring forage (Maloney et al., 1999), with a balance between rye forage yield and quality being reached when rye is harvested at boot stage (Edmisten et al., 1998). When double cropped aft er winter rye, decreased corn yield compared to sole cropped corn has been observed, but total forage production was greater in a rye–corn silage double crop system (Raimbault et al., 1990; Tollenaar et al., 1992). Th e double-crop system therefore off ers the potential for increased profi tability. Previous work suggests that spring rye management can dictate the eff ect of the cover crop on subsequent corn production. However, few data are available on soil moisture and NO3–N depletion induced by killed vs. harvested rye and the eff ect of resource depletion on subsequent corn silage. We hypothesize that later rye termination in the harvested rye double crop system will result in greater resource depletion and greater impact on subsequent corn than for a killed rye cover crop. Th e objective of this study was to examine the feasibility of winter ABSTRACT A winter rye (Secale cereale L.) cover crop can be seeded aft er corn (Zea mays L.) silage to mitigate some of the environmental concerns associated with corn silage production. Rye can be managed as a cover crop by chemical termination or harvested for forage. A fi eld study was conducted in Morris, MN in 2008 and 2009 to determine the impact of killed vs. harvested rye cover crops on soil moisture and NO3–N, and to monitor the impact of the rye on subsequent corn yield. Corn for silage was seeded either aft er winter fallow (control), aft er a rye cover crop terminated 3 to 4 wk before corn planting (killed rye), or aft er a rye forage crop harvested no more than 2 d before corn planting (harvested rye). Soil moisture aft er killed rye was similar to the control, but aft er harvested rye was 16% lower. Available soil NO3–N was decreased aft er both killed rye (35%) and harvested rye (59%) compared to the control. Corn biomass yield aft er killed rye was similar to the control, but yield following harvested rye was reduced by 4.5 Mg ha−1. Total forage biomass yield (silage + rye) was similar for all treatments. Th is work demonstrates that the environmental benefi ts of a winter rye cover crop can be achieved without impacting corn yield, but the later termination required for rye forage production resulted in soil resource depletion and negatively impacted corn silage yield.