Forage Radish Cover Crop Suppresses Winter Annual Weeds in Fall and Before Corn Planting

Abstract

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. F orage radish is a new winter annual cover crop in the Mid-Atlantic region. Early work with forage radish as a cover crop in this region included observations that it could provide dramatic fall and spring weed suppression (Weil and Kremen, 2007). However, questions remain about the repeatability, amount, and duration of this suppression as well as the diversity of weed species aff ected. Answering these questions could lead to the development of integrated weed management strategies that reduce the use of herbicides while providing other soil and environmental benefi ts. Radish cover crops are members of the Brassicaceae family and behave diff erently than cover crops currently grown in the Mid-Atlantic region, such as rye (Secale cereale L.), oat (Avena sativa L.), winter wheat (Triticum aestivum L.), crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa Roth) (Holderbaum et al., 1990; Maryland Department of Agriculture, 2009; Weil and Kremen, 2007). Current cover crop species are winter annuals that grow more slowly in the fall and produce most of their biomass in the spring. Th ey must be terminated in the spring before subsequent crop planting and develop higher C/N ratios when left to grow longer in the spring. Th us they require timely management to reduce the potential for delayed planting and immobilization of N needed by the subsequent crop. Unlike the above-mentioned cover crops, forage radish emerges quickly and grows rapidly in the fall (Weil et al., 2009). Th is may help inhibit undesirable winter annual weed growth. It also has a large white fl eshy tap root that may protrude aboveground as much as 10 to 15 cm. Forage radish is sensitive to frost and typically winter-kills with prolonged exposure to temperatures below-4ºC (Weil et al., 2009). Forage radish roots and shoots have a low C/N ratio. Its residues decompose rapidly during the freeze-thaw cycles that characterize winters in the Mid-Atlantic region and leave little residue on the soil surface the following spring. As a result, a unique low residue and weed-free seed bed is created for planting in the early spring following forage radish cover crops. Th ese characteristics could make forage radish cover crops useful for farmers who are interested in the benefi ts of fall cover crops but want to avoid excessive spring crop residues or for organic farmers who wish to reduce preplant tillage without the use of prohibited herbicides. Few studies have described weed suppression by radish cover crops. In the Netherlands, fodder radish (Raphanus sativus L. cultivar Brutus) suppressed the growth of weeds while it grew in the fall (Kruidhof et al., 2008). Oilseed radish (Raphanus sativus L. var. oleiformis) suppressed the fall growth of volunteer winter wheat in Ont...

Allelopathic effects and weed suppressive ability of cover crops

“…niger, V. sativa, M1 and M2 achieved a significant decrease of weed population compared to the untreated control. Similar results were observed during autumn period in the study of Lawley et al (2011). Five WAS differences of the weed suppressive ability can be observed between treatments.…”

Radish Planting Date and Nitrogen Rate for Cover Crop Production and the Impact on Corn Yields in Upstate Missouri

“…Corn grain moisture (188 g kg -1 ) and test weight (42.3 g cm -3 ) were greatest following early-planted radish; however, no significant difference in grain yields occurred in moderate-(2013) and high-yield (2014) environments at preplant N rates typical for this region. This was similar to other research evaluating corn's rotational response to cover crops with radish (Lawley et al, 2011). However, there is some research that has shown a yield increase in subsequent crops such as sweet corn following radish (Malik et al, 2008) which was related to increased weed suppression.…”

“…However, in 2014 no differences among planting dates were observed. Research has shown that Brassica species includeing radish have significant weed suppression (Altieri et al, 2011;Lawley et al, 2011Lawley et al, , 2012Malik et al, 2008;Norsworth, 2003;Stivers-Young, 1998;Uremis et al, 2009). Norsworthy (2003) showed that germination and radical growth of all weed species [sickle pod (Senna obtusifolia L.), prickly sida (Sida spinosa L.), and yellow nutsedge (Cyperus esculentus L.)] evaluated were reduced by extract of forage radish in comparison to non-treated controls.…”

“…Lawley et al (2012) observed early spring suppression of common chickweed and henbit; however, radish showed almost complete weed control in early spring while control declined throughout the growing season as summer annual weeds started emerging. Forage radish provided complete weed suppression in early fall through winter and into early March when weed cover was only 0-3%; however, weed suppression from radishes did not extend to the next growing season and a postemergence herbicide was needed to be applied to avoid a yield reduction in corn due to weed interference (Lawley et al, 2011). Thus it is possible that winter annual weed suppression was greater in 2014 due to an earlier burdown application prior to allowing growth of weeds later in the season.…”

“…This simplifies spring seeding, provides warmer soils, and allows for more timely planting of subsequent crops compared to cover crops that overwinter, such as ryegrass (Lawley et al, 2011).…”