Long-Term Lentil Green-Manure Replacement for Fallow in the Semiarid Northern Great Plains

Published in Agron. J. 103:1292–1298 (2011) Posted online 13 Jun 2011 doi:10.2134/agronj2010.0410 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. A the cost of N continues to increase, alternatives are being sought to reduce use of fossil-fuel-derived fertilizers. In the North America northern Great Plains (NGP) the use of leguminous green manures can be used to reduce fertilizer N requirements. Inclusion of green manures instead of fallowing not only reduces dependence on fossil fuel-derived fertilizer but can also be used to boost yields or as an organic farming fertilizer source. Limited soil water availability during critical growth stages reduces crop production in the semiarid Great Plains (Nielsen et al., 2002, 2009) restricting cropping options. Typically, wheat (Triticum aestivum L.)–fallow rotations have been used in the Great Plains to increase soil water storage during fallow periods (Greb et al., 1970). Summer fallow area has, however, decreased steadily in the past decade. For instance, in Montana wheat plantings following fallow decreased from 1.55 million ha in 1999 to 1.26 million ha in 2008 (NASS, 2009). Precipitation storage effi ciency during fallow periods ranges from about 15 to 40% (Black and Power, 1965; Tanaka and Aase, 1987; Peterson et al., 1996), with the greater values reported for reduced and no-till systems. Th ough the practice of summer fallow increases soil water for subsequent crops, detrimental eff ects of fallow are well documented and include decreased soil organic C and N, decreased mineralizable C and N, increased soil erosion, and development of saline seeps (Black et al., 1981; Janzen, 1987; Campbell et al., 1990; Wienhold et al., 2006). Research on green manure in the NGP is not new; literature dates back to 1917 (Pieters, 1917). In his summary, Pieters in 1917 concluded that conditions in the Great Plains do not warrant the use of leguminous green-manure crops. Army and Hide (1959) tested this hypothesis and reported that use of green manure crops grown during part of the fallow period had no benefi cial impact on wheat yield, test weight, or protein content. Since then, technology changes warrant a reevaluation of this concept. Less water-intensive rotations have used pulse crops with great success in the North America NGP (Karamanos et al., 2003; Miller et al., 2003a). Miller et al. (2003b) noted that pea (Pisum sativum L.) or lentil harvested for seed provided rotational benefi ts leading to increased wheat yield compared with continuous wheat. When Indianhead lentil was grown in place of fallow in a spring wheat–fallow system in northeast Montana and lentil growth was terminated at full bloom, wheat yield was reduced by 25% (Pikul et al., 1997). Th e authors attributed the yield reduction primarily to less available N in the green fallow system (Pikul et al., 1997). Th at study reported no diff erences in soil water content at wheat planting between the wheat–fallow system and the wheat–legume fallow system. Vigil and Nielsen (1998) and Nielsen and Vigil (2005) reported on replacing a portion of the fallow period in winter wheat–fallow systems in the central Great Plains with legume production and found subsequent wheat yields were greatly diminished following legume growth due to water use by the legume. Vigil and Nielsen (1998) concluded that the reduction in wheat yields, even with early legume termination ABSTRACT