Managing Cover Crops Profitably THIRD EDITION

USDA Plant Hardiness Zone Map

Agricultural Research Service USDA Managing Cover Crops Profitably THIRD EDITION

Handbook Series Book 9

Published by the Sustainable Agriculture Research and Education (SARE) program, with funding from the National Institute of Food and Agriculture, U.S. Department of Agriculture Third Printing - June 2012 Library of Congress Cataloging-in-Publication Data

Managing Cover Crops Profitably, Third Edition, was pub- Managing cover crops profitably / project manager and lished in 2007 by the Sustainable Agriculture Research and editor, Andy Clark.—3rd ed. Education (SARE) program under cooperative agreements p. cm. -- (Sustainable Agriculture Research and Education with the National Institute of Food and Agriculture, USDA, (SARE) program handbook series ; bk. 9) the University of Maryland and the University of Vermont. Includes bibliographical references and index. ISBN 978-1-888626-12-4 (pbk.) Every effort has been made to make this book as accurate as 1. Cover crops—United States—Handbooks, manuals, etc. possible and to educate the reader. This text is only a guide, I. Clark, Andy. II. Sustainable Agriculture Research & however, and should be used in conjunction with other infor- Education (SARE) program mation sources on farm management. No single cover crop management strategy will be appropriate and effective for all SB284.3.U6M36 2007 conditions. The editor/authors and publisher disclaim any lia- 631.5'82—dc22 bility, loss or risk, personal or otherwise, which is incurred as 2007024273 a consequence, directly or indirectly, of the use and application of any of the contents of this book. Cover photos (clockwise from top left): Jeff Moyer, farm manager for The Rodale Institute, kills a hairy Mention, visual representation or inferred reference of a vetch cover crop with a newly designed, front-mounted product, service, manufacturer or organization in this publi- roller while a no-till planter drops seed corn behind the cation does not imply endorsement by the USDA, the SARE tractor. Photo by Matthew Ryan for the Rodale Institute. program or the authors. Exclusion does not imply a negative evaluation. Annual ryegrass overseeded into kale is already providing cover crop benefits before cash crop harvest. Photo by SARE works to increase knowledge about—and help farmers Vern Grubinger, Univ. of VT. and ranchers adopt—practices that are profitable, environ- Guihua Chen, a Univ. of MD graduate student, studies the mentally sound and good for communities. For more informa- ability of forage radish to alleviate soil compaction. Photo by tion about SARE grant opportunities and informational Ray Weil, Univ. of MD. resources, go to www.sare.org. SARE Outreach is the national outreach arm of SARE. For more information, contact: A winter smother crop of yellow mustard minimizes weed growth in a vineyard. Photo by Jack Kelly Clark, Univ. of CA. SARE Outreach “Purple Bounty” hairy vetch, an early-maturing, winter hardy 1122 Patapsco Building variety for the Northeast, was developed by Dr. Tom Devine, University of Maryland USDA-ARS in collaboration with The Rodale Institute, College Park, MD 20742-6715 Pennsylvania State University and Cornell University (301) 405-8020 Agricultural Experiment Stations. Photo by Greg Bowman, (301) 405-7711 (fax) NewFarm.org. [email protected] www.sare.org Red clover, frostseeded into winter wheat, is well established just prior to wheat harvest. Photo by Steve Deming, To order copies of this book, ($19.00 plus $5.95 s/h) MSU Kellogg Biological Station. contact (301) 374-9696, [email protected], or order online at www.sare.org/WebStore. Back cover photo: Sorghum-sudangrass increased irrigated potato yield and tuber quality in Colorado, whether it was Project manager and editor: Andy Clark harvested for hay or incorporated prior to potato planting. Graphic design and layout: Diane Buric Photo by Jorge A. Delgado, USDA-ARS. Interior illustrations: Marianne Sarrantonio and Elayne Sears Copy editing: Andy Clark Printed in the United States of America on recycled paper. Proofreading: Aneeqa Chowdhury Indexing: Claire Brannen Printing: United Book Press, Inc. FOREWORD

over crops slow erosion, improve soil, results and updated farmer profiles and research smother weeds, enhance nutrient and data throughout. We also added two new chapters. Cmoisture availability, help control many Brassicas and Mustards (p. 81) lays out the pests and bring a host of other benefits to your current theory and management of cover crops in farm. At the same time, they can reduce costs, the BRASSICACEAE family. Brassica cover crops are increase profits and even create new sources of thought to play a role in management of nema- income. You’ll reap dividends on your cover crop todes, weeds and disease by releasing chemical investments for years, because their benefits accu - compounds from decomposing residue. Results mulate over the long term. are promising but inconsistent. Try brassicas on Increasing energy costs will have a profound small plots and consult local expertise for addi- effect on farm economics in coming years. As we tional information. go to press, it is impossible to predict how fast Managing Cover Crops in Conservation energy costs will increase, but since cover crop Tillage Systems (p. 44) addresses the management economics are rooted in nitrogen dynamics (how complexities of reduced tillage systems. If you are much N you save or produce with cover crops), already using cover crops, the chapter will help fuel costs (the cost of N and trips across the field) you reduce tillage. If you are already using con- and commodity prices, energy prices will certain- servation tillage, it shows you how to add or bet- ly impact the economics of cover crop use. ter manage cover crops. Cover crops and Economic comparisons in the 2nd edition were conservation tillage team up to reduce energy use based on the old economy of two-dollar corn, on your farm and that means more profits. twenty-cent nitrogen and cheap gas. Some studies We have tried to include enough information showed that cover crops become more profitable for you to select and use cover crops appropriate as the price of nitrogen increases. We retained to your operation. We recommend that you define some of these excellent studies because data from your reasons for growing a cover crop—the sec - new studies is not yet available. What we do know tion, Selecting the Best Cover Crops for Your is that cover crops can help you to increase yields, Farm (p. 12) can help with this—and take as save on nitrogen costs, reduce trips across the field much care in selecting and managing cover crops and also reap many additional agronomic benefits. as you would a cash crop. There is a cover crop to fit just about every Regional and site-specific factors can compli cate farming situation. The purpose of this book is to cover crop management. No book can ade quately help you find which ones are right for you. address all the variables that make up a crop pro- Farmers around the country are increasingly duction system. Before planting a cover crop, learn looking at the long-term contributions of cover as much as you can from this book and talk to oth- crops to their whole farm system. Some of the ers who are experienced with that cover crop. most successful are those who have seen the ben- We hope that this updated and expand ed edi- efits and are committed to making cover crops tion of Managing Cover Crops Profitably will work for them. They are re-tooling their cropping lead to the successful use of cover crops on a systems to better fit cover crop growth patterns, wider scale as we continue to increase the sus- rather than squeezing cover crops into their exist- tainability of our farming systems. ing system, time permitting. This 3rd edition of Managing Cover Crops Andy Clark, Communications Director Profitably aims to capture farmer and other Sustainable Agriculture Research and research results from the past ten years. We verified Education (SARE) the information from the 2nd edition, added new June, 2007

FOREWORD 3 MANAGING COVER CROPS PROFITABLY THIRD EDITION

Foreword ...... 3 Buckwheat ...... 90 Acknowledgments...... 5 Oats ...... 93 How to Use this Book ...... 7 • Oats, Rye Feed Soil in Benefits of Cover Crops ...... 9 Corn/Bean Rotation...... 96 Selecting the Best Cover Crops Rye ...... 98 for Your Farm...... 12 • Cereal Rye: Cover Crop Workhorse . . . . 102 Building Soil Fertility and Tilth • Rye Smothers Weeds Before Soybeans . 104 with Cover Crops ...... 16 Sorghum Sudangrass Hybrids ...... 106 • Cover Crops Can Stabilize Your Soil. . . . 19 • Summer Covers Relieve Compaction. . 110 • How Much N? ...... 22 Winter Wheat...... 111 Managing Pests with Cover Crops ...... 25 • Wheat Boosts Income and • Georgia Cotton, Peanut Farmers Soil Protection ...... 113 Use Cover Crops to Control Pests ...... 26 • Wheat Offers High-Volume • Select Covers that Balance Pests, Weed Control Too ...... 114 Problems of Farm ...... 30 Overview of Legume Cover Crops . . . . . 116 Crop Rotations with Cover Crops ...... 34 Cover Crop Mixtures Expand • Full-Year Covers Tackle Tough Weeds . . . 38 Possibilities ...... 117 • Start Where You Are ...... 41 Berseem Clover ...... 118 Managing Cover Crops in Conservation • Nodulation: Match Inoculant to Tillage Systems...... 44 Maximize N ...... 122 • After 25 Years, Improvements Cowpeas ...... 125 Keep Coming ...... 52 • Cowpeas Provide Elegant Solution Introduction to Charts...... 62 to Awkward Niche ...... 128 Chart 1: Top Regional Cover Crop Species . . 66 Crimson Clover ...... 130 Chart 2: Performance and Roles...... 67 Field Peas ...... 135 Chart 3A: Cultural Traits ...... 69 • Peas Do Double Duty for Kansas Chart 3B: Planting...... 70 Farmer ...... 140 Chart 4A: Potential Advantages...... 71 Hairy Vetch...... 142 Chart 4B: Potential Disadvantages...... 72 • Cover Crop Roller Design Holds Promise for No-Tillers...... 146 COVER CROP SPECIES • Vetch Beats Plastic ...... 150 Overview of Nonlegume Cover Crops . . . 73 Medics ...... 152 Annual Ryegrass...... 74 • Jess Counts on GEORGE for N and Barley ...... 77 Feed ...... 153 Brassicas and Mustards ...... 81 • Southern Spotted Bur Medic offers • Mustard Mix Manages Nematodes in Reseeding Persistence...... 154 Potato/Wheat System ...... 86

4 MANAGING COVER CROPS PROFITABLY Red Clover ...... 159 APPENDICES Subterranean Clovers ...... 164 A.Testing Cover Crops on Your Farm ...... 189 Sweetclovers ...... 171 B. Up-and-Coming Cover Crops...... 191 • Sweetclover: Good Grazing, Great C. Seed Suppliers ...... 195 Green Manure...... 174 D. Farming Organizations with White Clover ...... 179 Cover Crop Expertise ...... 200 • Clovers Build Soil, Blueberry E. Regional Experts ...... 202 Production ...... 182 F. Citations Bibliography ...... 280 Woollypod Vetch ...... 185 G. Resources from SARE ...... 230 H. Reader Response Form ...... 232

INDEX...... 233

ACKNOWLEDGMENTS

his 3rd edition could not have been written without the help of many cover crop experts. It is based in large part on the content of the 2nd edition, researched and written by Greg Bowman, TCraig Cramer and Christopher Shirley. The following people reviewed the 2nd edition, suggested revisions and updates and contributed new content.

Aref Abdul-Baki, retired, USDA-ARS Guihua Chen, Univ. of Maryland Wesley Adams, Ladonia, TX Aneeqa Chowdhury, SARE Kenneth A. Albrecht, Univ. of Wisconsin Hal Collins, USDA-ARS Jess Alger, Stanford, MT Craig Cramer, Cornell Univ. Robert G. Bailey, USDA Forest Service Nancy Creamer, North Carolina State Univ. Kipling Balkcom, USDA-ARS William S. Curran, The Pennsylvania State Univ. Ronnie Barentine, Univ. of Georgia Seth Dabney, USDA-ARS Phil Bauer, USDA-ARS Bryan Davis, Grinnell, IA R. Louis Baumhardt, USDA-ARS Jorge Delgado, USDA-ARS Rich and Nancy Bennett, Napoleon, OH Juan Carlos Diaz-Perez, Univ. of Georgia Valerie Berton, SARE Richard Dick, Ohio State Univ. Robert Blackshaw, Agriculture and Agri-Food Canada Sjoerd W. Duiker, The Pennsylvania State Univ. Greg Bowman, NewFarm Gerald W. Evers, Texas A&M Univ. Rick Boydston, USDA-ARS Rick Exner, Iowa State Univ. Extension Lois Braun, Univ. of Minnesota Richard Fasching, NRCS Eric B. Brennan, USDA-ARS Jim French, Partridge, KS Pat Carr, North Dakota State Univ. Eric Gallandt, Univ. of Maine Max Carter, Douglas, GA Helen Garst, SARE

ACKNOWLEDGMENTS 5 Dale Gies, Moses Lake, WA Vicki Morrone, Michigan State Univ. Bill Granzow, Herington, KS Jeff Moyer, The Rodale Institute Stephen Green, Arkansas State Univ. Paul Mugge, Sutherland, IA Tim Griffin, USDA-ARS Dale Mutch, MSU Kellogg Biological Station Steve Groff, Holtwood, PA Rob Myers, Jefferson Institute Gary Guthrie, Nevada, IA Lloyd Nelson, Texas Agric. Experiment Station Matthew Harbur, Univ. of Minnesota Mathieu Ngouajio, Michigan State Univ. Timothy M. Harrigan, Michigan State Univ. Eric and Anne Nordell, Trout Run, PA Andy Hart, Elgin, MN Sharad Phatak, Univ. of Georgia Zane Helsel, Rutgers Univ. David Podoll, Fullerton, ND Paul Hepperly, The Rodale Institute Paul Porter, Univ. of Minnesota Michelle Infante-Casella, Rutgers Univ. Andrew Price, USDA-ARS Chuck Ingels, Univ. of California Ed Quigley, Spruce Creek, PA Louise E. Jackson, Univ. of California RJ Rant, Grand Haven, MI Peter Jeranyama, South Dakota State Univ. Bob Rawlins, Rebecca, GA Nan Johnson, Univ. of Mississippi Wayne Reeves, USDA-ARS Hans Kandel, Univ. of Minnesota Extension Ekaterini Riga, Washington State Univ. Tom Kaspar, USDA-ARS Lee Rinehart, ATTRA Alina Kelman, SARE Amanda Rodrigues, SARE Rose Koenig, Gainesville, FL Ron Ross, No-Till Farmer James Krall, Univ. of Wyoming Marianne Sarrantonio, Univ. of Maine Amy Kremen, Univ. of Maryland Harry H. Schomberg, USDA-ARS Roger Lansink, Odebolt, IA Pat Sheridan, Fairgrove, Mich. Yvonne Lawley, Univ. of Maryland Jeremy Singer, USDA-ARS Frank Lessiter, No-Till Farmer Richard Smith, Univ. of California John Luna, Oregon State Univ. Sieglinde Snapp, Kellogg Biological Station Barry Martin, Hawkinsville, GA Lisa Stocking, Univ. of Maryland Todd Martin, MSU Kellogg Biological Station James Stute, Univ. of Wisconsin Extension Milt McGiffen, Univ. of California Alan Sundermeier, Ohio State Univ. Extension Andy McGuire, Washington State Univ. John Teasdale, USDA-ARS George McManus, Benton Harbor, MI Lee and Noreen Thomas, Moorhead, MN John J. Meisinger, USDA/ARS Dick and Sharon Thompson, Boone, IA Henry Miller, Constantin, MI Edzard van Santen, Auburn Univ. Jeffrey Mitchell, Univ. of California Ray Weil, Univ. of Maryland Hassan Mojtahedi, USDA-ARS Charlie White, Univ. of Maryland Gaylon Morgan, Texas A&M Univ. Dave Wilson, The Rodale Institute Matthew J. Morra, Univ. of Idaho David Wolfe, Cornell Univ.

6 MANAGING COVER CROPS PROFITABLY HOW TO USE THIS BOOK

hink of this book as a tool chest, not a cook- 3. With some particular cover crops in mind, step book. You won’t find the one simple recipe back and look at the big picture of how you can Tto meet your farming goals. You will find fit cover crops into your farming operations. Sit the tools to select and manage the best cover down with a highlighter and explore these crops for the unique needs of your farm. chapters: In this tool chest you will find helpful maps and • Benefits of Cover Crops (p. 9) explains impor- charts, detailed narratives about individual cover tant cover crop roles such as reducing costs, crop species, chapters about specific aspects of improving soil and managing pests. cover cropping and extensive appendices that • Selecting the Best Cover Crops (p. 12) helps will lead you to even more information. you evaluate your operation’s needs and niches (seasonal, cash-crop related, and profit potential). 1. Start with Top Regional Cover Crop Species Several examples show how to fit crops to (p. 66). This chart will help you narrow your detailed situations. search by listing the benefits you can expect from • Building Soil Fertility and Tilth (p. 16) shows the top cover crops adapted to your region. You’ll how cover crops add organic matter and greater discover which are the best nitrogen (N) sources, productivity to the biological, chemical and phys- soil builders, erosion fighters, subsoil looseners, ical components of soil. weed fighters and pest fighters.

2. Next, find out more about the performance and management of the cover crops that look like good candidates for your farm. You’ll find two streams of information: • Charts quickly provide you with details to help you compare cover crops. Performance and Roles (p. 67) lists ranges for N and dry matter pro - duction and ranks each cover crop’s potential for providing 11 benefits. Cultural Traits (p. 69) and Planting (p. 70) explains the growth, environ - mental tolerances, seeding preferences and estab - lishment costs for each crop. • Narratives. The Table of Contents (p. 4) and the page numbers accompanying each species in Charts 2, 3 and 4 direct you to the heart of the book, the chapters on each cover crop. The chapters offer even more practical descriptions of how to plant, manage, kill and make the best use of each species. Don’t overlook Up-and-Coming Cover Crops (p. 191) that briefly describes SORGHUM-SUDANGRASS is a tall, warm-season grass promising but lesser known cover crops. One of that stifles weeds and decomposes to build soil organic them may be right for your farm. matter.

HOW TO USE THIS BOOK 7 • Managing Pests with Cultivars of SUBTERRANEAN Cover Crops (p. 25) CLOVER, a low-growing, explores how cover reseeding annual legume, are crops change field adapted to many climates. environments to protect cash crops from insects, dis - 4. Now that you’ve ease, weeds and tried out most of the nematodes. tools, revisit the • New this edition: charts and narratives Managing Cover Crops to zero in on the cover in Conservation Tillage crops you want to try. Systems (p. 44) provides man- The Appendices include infor- agement details for cover crops in mation to help you run reli able on- reduced tillage systems. farm cover crop comparison trials. You’ll also • Crop Rotations (p. 34) explains how to inte- find contact infor mation for cover crop experts grate cover crops and cash crops in sequence in your region, seed and inoculant suppliers, ref- from year to year for optimum produc tivity from erences to books and academic papers cited in on-farm resources. this book and websites with more cover crop • Citations Bibliography (p. 208) lists many of information. the publications and specialists cited in the book. Citations within the book are numbered in paren - 5. Finally, share your cover crop plans with farm- theses. Refer to the numbered citation in the bib - ers in your area who have experience with cover liography if you want to dig deeper into a topic. crops. Your local Extension staff, regional IPM spe- • Climatic Zone Maps inside the front and cialist or a sustainable farming group in your area back covers help you understand differences in may be able to provide contacts. Be sure to tap cover crop performance from location to loca - local wisdom. You can find out the cover crop tion. You may find that some cover crops have prac tices that have worked traditionally, and the performed well in tests far from where you farm, new wrinkles or crops that innovative practition- but under comparable climatic conditions. ers have discovered.

The USDA Plant Hardiness Zone Map (inside Abbreviations used in this book front cover) shows whether a crop will survive A = acre or acres the average winter in your area.We refer to the bu. = bushel or bushels USDA hardiness zones throughout the book. DM = dry matter, or dry weight of plant material Readers’ note: A new version of the map is F = (degrees) Fahrenheit in. = inch or inches included in this reprint of the book (2012). K = potassium lb. = pound or pounds The U.S. Forest Service map, Ecoregions of N = nitrogen the United States (inside back cover), served in OM = organic matter part as the basis for the adaptation maps includ ed P = phosphorus at the beginning of each cover crop chapter. This p. = page ecosystem map, while designed to classify forest pp. = pages growth, shows localized climate differ ences, such T = ton or tons as rainfall and elevation, within a region. See > = progression to another crop Bailey (citation #17 in Appendix F, p. 209) for / = a mixture of crops growing together more information about ecoregions.

8 MANAGING COVER CROPS PROFITABLY BENEFITS OF COVER CROPS

over crops can boost your profits the first year you plant them. They can improve Cyour bottom line even more over the years as their soil-improving effects accumulate. Other benefits—reducing pollution, erosion and weed and insect pressure—may be difficult to quantify or may not appear in your financial statements. Identifying these benefits, however, can help you make sound, long-term decisions for your whole farm. What follows are some important ways to eval - RED CLOVER is an annual or multi-year legume that uate the economic and ecological aspects of improves topsoil. It is easily overseeded into standing cover crops. These significant benefits (detailed crops or frostseeded into grains in early spring. below) vary by location and season, but at least two or three usually occur with any cover crop. Legume cover crops convert nitrogen gas in Consult local farming groups and agencies with the atmosphere into soil nitrogen that plants can cover crop experience to figure more precise use. See Nodulation: Match Inoculant to crop budgets. Maximize N (p. 122). Crops grown in fields after • Cut fertilizer costs legumes can take up at least 30 to 60 percent of • Reduce the need for herbicides and other the N that the legume produced. You can reduce pesticides N fertilizer applications accordingly. For more • Improve yields by enhancing soil health information on nitrogen dynamics and how to • Prevent soil erosion cal culate fertilizer reductions, see Building Soil • Conserve soil moisture Fertility and Tilth with Cover Crops (p. 16). The • Protect water quality N value of legumes is the easiest cover crop • Help safeguard personal health benefit to evaluate, both agronomically and economically. This natural fertility input alone can Evaluate a cover crop’s impact as you would any justify cover crop use. other crop, balancing costs against returns in all • Hairy vetch boosted yield for no-till corn forms. Don’t limit your calculations, however, to more than enough to cover its establishment the target cover crop benefit. A cover often has costs, a three-year study in Maryland showed. several benefits. Many cover crops offer harvest Further, the vetch can reduce economic risk and possibilities as forage, grazing or seed that work usually will be more profitable than no-till corn well in systems with multiple crop enterprises after a winter wheat cover crop (1993 data). The and livestock. result held true even if corn were priced as low as $1.80 per bushel, or N fertilizer ($0.30/lb.) was SPELLING IT OUT applied at the rate of 180 lb. N/A (173). • Medium red clover companion seeded with Here’s a quick overview of benefits you can grow oats and hairy vetch had estimated fertilizer on your farm. Cover crops can: replacement value of 65 to 103 lb. N/A in a four- year study in Wisconsin, based on a two year rota - Cut fertilizer costs by contributing N to cash tion of oats/legume > corn. Mean corn grain yield crops and by scavenging and mining soil nutrients. following these legumes was 163 bu./A for red

BENEFITS OF COVER CROPS 9 clover and 167 bu./A for hairy vetch, compared Using a rotation of To estimate with a no legume/no N fertilizer yield of 134 malting barley>cover bu./A (400). crop radish>sugar your potential N • Austrian winter peas, hairy vetch and beets has successfully fertilizer savings NITRO alfalfa can provide 80 to 100 percent of a reduced sugar beet subsequent potato crop’s nitrogen requirement, a cyst nematodes to from a cover study in the Pacific Northwest showed (394). increase yield of sugar crop, see the • Fibrous-rooted cereal grains or grasses are beets in a Wyoming particularly good at scavenging excess nutri - test. Using this brassi- sidebar, How ents—especially N—left in the soil after cash crop ca cover crop after harvest. Much of the N is held within the plants malting barley or Much N? (p. 22). until they decompose. Fall-seeded grains or grass- silage corn substitut - es can absorb up to 71 lb. N/A within three ed profitably for months of planting, a Mary land study showed chemical nematicides when nematode levels (46). Addition of cover crops to corn>soybean were moderate (231). A corn>rye>soybeans> and corn>peanut>cotton rotations and appropri- wheat>hairy vetch rota tion that has reduced ate timing of fertilizer application usually reduce pesticide costs is at least as profitable as conven- total N losses, without causing yield losses in sub- tional grain rotations without cover crops, a study sequent crops, a USDA-ARS computer modeling in southeastern Pennsylvania shows (174). Fall- study confirms (354). planted brassica cover crops coupled with mechan ical cultivation help potato growers with Reduce the Need for Herbicides a long growing season maintain marketable yield Cover crops suppress weeds and reduce damage and reduce herbicide applications by 25 percent by diseases, insects and nematodes. Many cover or more, a study in the inland Pacific Northwest crops effectively suppress weeds as: showed (394). • A smother crop that outcompetes weeds for water and nutrients Improve Yields by Enhancing Soil Health • Residue or growing leaf canopy that blocks Cover crops improve soil by: light, alters the frequency of light waves and • Speeding infiltration of excess surface water changes soil surface temperature • Relieving compaction and improving struc- • A source of root exudates or compounds that ture of overtilled soil provide natural herbicidal effects • Adding organic matter that encourages beneficial soil microbial life Managing Pests with Cover Crops (p. 25) • Enhancing nutrient cycling describes how cover crops can: • Host beneficial microbial life that discourages Building Soil Fertility and Tilth with Cover disease Crops (p. 16) details the biological and chemical • Create an inhospitable soil environment for processes of how cover crops improve soil health many soilborne diseases and nutrient cycling. Leading soil-building crops • Encourage beneficial insect predators and par- include rye (residue adds organic matter and con- asitoids that can reduce insect damage below serves moisture); sorghum-sudangrass (deep pen- economic thresholds etrating roots can break compaction); and • Produce compounds that reduce nematode ryegrass (stabilizes field roads, inter-row areas and pest populations borders when soil is wet). • Encourage beneficial nematode species

10 MANAGING COVER CROPS PROFITABLY Prevent Soil Erosion than conven tional bare fallow (383). Timely Quick-growing cover crops hold soil in place, spring termination of a cover crop avoids the neg- reduce crusting and protect against erosion due ative impact of opposite water conditions: excess to wind and rain. The aboveground portion of cov- residue holding in too much mois ture for planting ers also helps protect soil from the impact of rain- in wet years, or living plants drawing too much drops. Long-term use of cover crops increases moisture from the soil in dry years. water infiltration and reduces runoff that can carry away soil. The key is to have enough stalk Protect Water Quality and leaf growth to guard against soil loss. By slowing erosion and runoff, cover crops Succulent legumes decompose quickly, especially reduce nonpoint source pollution caused by sed- in warm weather. Winter cereals and iments, nutrients and agricultural chemicals. By many brassicas have a better chance taking up excess soil nitrogen, cover crops pre- of overwintering in colder climates. vent N leaching to groundwater. Cover crops These late-summer or fall-planted also provide habitat for wildlife. A rye crops often put on sig nificant growth cover crop scavenged from 25 to 100 even when temperatures drop into percent of residual N from conven- the 50s, and often are more winter- tional and no-till Georgia corn hardy than legumes (361). In a no- fields, one study showed. Up to till cotton system, use of cover 180 lb. N/A had been applied. A crops such as winter wheat, crimson barley cover crop removed 64 per- clover and hairy vetch can reduce soil cent of soil nitrogen when applied erosion while maintaining high cot- N averaged 107 lb./A (220). ton yields, a Mississippi study shows (35). Help Safeguard Personal Health By reducing reliance on agrichemi cals Conserve Soil Moisture for cash crop production, cover crops Residue from killed cover crops increas es help protect the health of your family, water infiltration and reduces evap - neighbors and farm workers. They oration, resulting in less moisture stress also help address community health during drought. Lightly incorporated and ecological concerns arising from cover crops serve dual roles. They nonpoint source pollution attributed trap surface water and add organic to farming activities. matter to increase infiltration to the root zone. Especially effective at Cumulative Benefits covering the soil surface are grass- You can increase the range of ben- type cover crops such as rye, efits by increasing the diversity of wheat, and sorghum-sudangrass cover crops grown, the frequen- hybrid. Some water-effi cient cy of use between cash crops legumes such as medic and and the length of time that INDIANHEAD lentils provide cover cover crops are growing in the crop benefits in dryland areas field. while conserving more moisture

WINTER WHEAT grows well in fall, then provides forage and protects soil over winter.

BENEFITS OF COVER CROPS 11 SELECTING THE BEST COVER CROPS FOR YOUR FARM by Marianne Sarrantonio

over crops provide many benefits, but To plan how and where to use cover crops, try they’re not do-it-all “wonder crops.”To find the following exercise: Ca suitable cover crop or mix of covers: Look at your rotation. Make a timeline of 18 to • Clarify your primary needs 36 monthly increments across a piece of paper. • Identify the best time and place for a cover For each field, pencil in current or probable rota- crop in your system tions, showing when you typically seed crops and • Test a few options when you harvest them. If possible, add other key information, such as This book makes selection of cover crops a lit tle eas- rainfall, frost-free periods and times of heavy labor ier by focusing on some proven ones.Thousands of or equipment demand. species and varieties exist, however. The steps that Look for open periods in each field that corre- follow can help you find crops that will work best spond to good conditions for cover crop estab- with a minimum of risk and expense. lishment, underutilized spaces on your farm, as well as opportunities in your sea sonal work 1. Identify Your Problem or Use schedule. Also consider ways to extend or overlap Review Benefits of Cover Crops (p. 9) to decide cropping windows. what you want most from a cover crop. Narrowing your goals to one or two primary and Here are examples of common niches in some perhaps a few secondary goals will greatly simpli- systems, and some tips: fy your search for the best cover species. Some Winter fallow niche. In many regions, seed common goals for cover crops are to: win ter covers at least six weeks before a hard • Provide nitrogen frost. Winter cereals, especially rye, are an excep- • Add organic matter tion and can be plant ed a little later. If ground • Improve soil structure cover and N recycling needs are minimal, rye can • Reduce soil erosion be planted as late as the frost period for success- • Provide weed control ful over wintering. • Manage nutrients You might seed a cover right after harvesting a • Furnish moisture-conserving mulch summer crop, when the weather is still mild. In cooler climates, consider extending the window You might also want the cover crops to provide by overseeding (some call this undersowing) a habitat for benefi cial organisms, better traction shade-tolerant cover before cash crop harvest. during harvest, faster drainage or another benefit. White clover, annual ryegrass, rye, hairy vetch, crimson clover, red clover and sweetclover toler - 2. Identify the Best Place and Time ate some shading. Sometimes it’s obvious where and when to use a If overseeding, irrigate afterwards if possible, or cover crop. You might want some nitrogen before seed just before a soaking rain is forecast. Species a corn crop, or a perennial ground cover in a vine - with small seeds, such as clovers, don’t need a lot yard or orchard to reduce erosion or improve of moisture to germinate and can work their way weed control. For some goals, such as building through tiny gaps in residue, but larger-seeded soil, it may be hard to decide where and when to species need several days of moist conditions to schedule cover crops. germinate.

12 MANAGING COVER CROPS PROFITABLY When overseeding into cash crops early in the region: broadcast a cover Look for open season, vigorous growth of the cover crop may before the grain enters cause water stress, increase disease risks due to boot stage (when seed- periods in lower air circulation or create new insect pest heads start elongating) each field or risks. Changing cover crop seeding rate, seeding later in spring or plant time, or the rotation sequence may lessen this after harvest. open spaces risk. To ensure adequate sunlight for the cover Full-year improved crop, overseed before full canopy closure of the fallow niche. To rebuild on your farm. primary crop (at last cultivation of field corn, for fertility or organic matter example) or just before the canopy starts to open over a longer period, again as the cash crop starts to die (as soybean perennials or biennials—or mixtures—require leaves turn yellow, for example). the least amount of maintenance. Spring-seeded Expect excessive field traffic around harvest yellow blossom sweetclover flowers the follow- time? Choose tough, low-growing covers such as ing summer, has a deep taproot and gives plenty grasses or clovers. Limit foot traffic to alternate of aboveground biomass. Also consider perennial rows, or delay a field operation to allow for cover forages recommended for your area. The below- crop establishment. ground benefit of a tap rooted perennial can have Another option could be to use a reseeding tremendous soil improving benefits when winter annual that dies back and drops seed each allowed to grow for several years. summer but reestablishes in fall. Subclovers Another option is sequential cover cropping. reseed well in regions south of Hardiness Zone 6. Plant hairy vetch or a grass-legume mixture in fall, Shorter-season crimson clovers—especially vari- terminate it the following spring at flowering, and eties with a high hard-seed percentage that ger- plant sorghum-sudangrass. The winter cover crop minate over an extended period—work well in provides weed suppression and ground cover, but the Southeast where moisture is sufficient. Even also nitrogen for the high-N sorghum-sudangrass, rye and vetch can reseed if managed properly. which can produce tons of biomass to build soil Summer fallow niche. Many vegetable rota - organic matter. tions present cover crop opportunities—and Properly managed, living mulches give many challenges. When double cropping, you might growers year-round erosion protection, weed con - have fields with a three- to eight-week summer fal- trol, nutrient cycling and even some nitrogen if low period between early planted and late plant- they include a legume. Some tillage, mowing or ed crops. Quick-growing summer annuals provide herbicides can help manage the mulch (to keep it erosion control, weed management, organic mat- from using too much soil moisture, for example) ter and perhaps some N. before crops are strip-tilled into the cover or Consider overseeding a spring crop with a residue. White clover could be a good choice for quick-growing summer grain such as buckwheat, sweet corn and tomatoes. Perennial ryegrass or millet or sorghum-sudangrass, or a warm-season some less aggressive turfgrasses such as sheep fes- legume such as cowpeas. Or, you might till out cue may work for beans, tomatoes and other veg- strips in the cover crop for planting a fall vegetables. etable crop and control the remaining cover Create new opportunities. Have you honed between the crop rows with mowing or light cul- a rota tion that seems to have few open time slots? tivation. Plant a cover in strips the width of a bed or wider, Small grain rotation niche. Companion seed a alternating with your annual veg etable, herb or winter annual cover crop with a spring grain, or frost field crop. Switch the strips the next year. Mow seed (broadcasting seed onto frozen ground) a cover the strips periodically and blow the topgrowth into winter grains. Soil freezing and thawing pulls onto adjoining cash crops as mulch. In a bed seed into the soil and helps germination. Another system, rotate out every third or fourth bed for a option if soil moisture isn’t a limiting factor in your soil-building cover crop.

SELECTING THE BEST COVER CROPS 13 Another option: Band a cover or some insect- • use water efficiently attracting shrubs around fields or along • have a soil-improving root system hedgerows to suppress weeds or provide benefi- • release some nutrients during the year, but not cial habitat where you can’t grow cash crops. too much N These hedgerows could also be used to produce • not harbor or attract pests marketable products such as nuts, berries or even craft materials. For this orchard scenario, white clover is probably the best option north of Zone 8. A mixture of 3. Describe the Niche low-growing legumes or a legume and grass mix Refer to your timeline chart and ask questions could also work. In warm regions, low-growing such as: clovers such as strawberry clover and white clover • How will I seed the cover? work well together, although these species may • What’s the weather likely to be then? attract pocket gophers. BLANDO brome and annual • What will soil temperature and moisture ryegrass are two quick-grow ing, reseeding grasses conditions be like? often suitable for orchard floors, but they will prob- • How vigorous will other crops (or pests) be? ably need some control with mowing. Or, try a • Should the cover be low-growing and reseeding winter annual legume such as crimson spreading, or tall and vigorous? clover, rose clover, subclover, an annual vetch or an • What weather extremes and field traffic must annual medic, depending on your climate. it tolerate? • Will it winterkill in my area? Example 2. A dairy lacks adequate storage in fall • Should it winterkill, to meet my goals? and winter for the manure it generates, which • What kind of regrowth can I expect? exceeds the nutrient needs for its silage corn • How do I kill it and plant into it? and grass/legume hay rotation. The cover crop • Will I have the time to make this work? needs to: • What’s my contingency plan—and risks—if • establish effectively after (or tolerate) silage the crop doesn’t establish or doesn’t die on corn harvest schedule? • take up a lot of N and P from fall-applied • Do I have the needed equipment and labor? manure and hold it until spring

4. Select the Best Cover Crop For this dairy scenario, rye is usually the best You have identified a goal, a time and a place, now choice. Other cereal grains or brassicas could specify the traits a cover crop would need to work if planted early enough. work well.

Example 1 . A sloping orchard needs a ground cover to reduce erosion. You’d like it to con - tribute N and organic matter and attract ben - eficial organisms but not rodents, nematodes or other pests. The cover can’t use too much water or tie up nutrients at key periods. Too much N might stimulate excessive tree leaf growth or prevent hardening off before winter. Finally you want a cover crop that is easy to maintain. It should: • be a perennial or reseeding annual • be low-growing, needing minimal HAIRY VETCH is an winter annual legume that management grows slowly in fall, then fixes a lot of N in spring.

14 MANAGING COVER CROPS PROFITABLY Example 3. In a moderate rainfall region after small grain harvest in late summer, you want a soil-protecting winter cover that can supply Nfor no-till corn next spring. You want to kill the cover without herbicides. You need a legume that: • can be drilled in late summer and put on a lot of fall growth • will overwinter • will fix a lot of N • can be mow-killed shortly before (or after) corn planting • could provide some weed-controlling, WINTER (cereal) RYE is an annual grain that moisture-conserving residue prevents soil and wind erosion. Its killed vegetation suppresses weeds for no-till planting. Hairy vetch works well in the Northeast, Midwest and parts of the mid-South. Mixing it with rye or another cereal improves its weed-management and with regional experts. Keep in mind that you can moisture-conservation potential. Crimson clover mix two or more species, or try several options in may be an appropriate choice for the southeastern small areas. Piedmont. Austrian winter pea could be considered, alone or in a mix, in coastal plain environments, but 6. Or Build a Rotation Around Cover Crops. will winterkill in Zone 7 and below. Where grain har- It’s hard to decide in advance every field’s crops, vest occurs in late spring or early summer, LANA planting dates, fieldwork or management wool lypod vetch might be a better choice. specifics. One alternative is to find out which cover crops provide the best results on your farm, Example 4. After a spring broccoli crop, you then build a rotation around those covers, espe- need a weed-suppressing cover that adds N cially when trying to tackle some tough soil and organic matter, and perhaps mulch, into improvement or weed control issues. See Full- which you will no-till seed fall lettuce or spinach. Year Covers Tackle Tough Weeds (p. 38). You want a cover that: With this “reverse” strategy, you plan covers • is very versatile according to their optimum field timing, and then • grows fast in hot weather determine the best windows for cash crops. A • can be overseeded into broccoli cover crop’s strengths help you decide which • germinates on the soil surface under dry cash crops would benefit the most. conditions For now, however, you probably want to fit one • fixes N or more cover crops into your existing rotations. • persists until you’re ready to kill it The charts and narratives in this book can help you select some of the most suitable species for Here, a quick-growing, warm-season legume such as your farming system and objectives. See Crop cowpeas may work, especially if you can irrigate to Rotations with Cover Crops (p. 34) to get you hasten establishment during dry conditions. thinking more. When you’ve narrowed your choices, refer to Appendix A, Testing Cover Crops 5. Settle for the Best Available Cover. It’s like- on Your Farm (p. 189) for some straightforward ly the “wonder crop” you want doesn’t exist. One tips on what to do next. or more species could come close, as the above examples indicate. Top Regional Cover Crop Adapted from Northeast Cover Crop Handbook by Species (p. 66) can provide a starting point. Check Marianne Sarrantonio, Rodale Institute, 1994.

SELECTING THE BEST COVER CROPS 15 BUILDING SOIL FERTILITY AND TILTH WITH COVER CROPS by Marianne Sarrantonio

oil is an incredibly complex substance. It has EROSION PROTECTION physical and chemical properties that allow Sit to sustain living organisms—not just plant Erosion of topsoil occurs on many farms, depriv - roots and earthworms, but hundreds of thousands ing fields of the most fertile portion, that contain- of different insects, wormlike creatures and ing the highest percentage of organic matter and microorganisms. When these organisms are in bal- nutrients. Cover crops can play a major role in ance, your soil cycles nutrients efficiently, stores fighting soil erosion. water and drains the excess, and maintains an A raindrop falling at high speed can dislodge environment in which plants can thrive. soil particles and cause them to move as far as 6 To recognize that a soil can be healthy, one has feet (42). Once a soil particle is loose, it is much only to think of the soil as a living entity. It more vulnerable to being carried away by run- breathes, it transports and transforms nutrients, it ning water. Any aboveground soil cover can take interacts with its environment, and it can even some of the punch out of a heavy rainfall simply puri fy itself and grow over time. If you view soil by acting as a cushion for raindrops. as a dynamic part of your farming system, unsus- A cover crop also can: tainable crop management practices amount to • Slow the action of moving water, thus reduc- soil neglect. That neglect could worsen as the soil ing its soil-carrying capacity, by creating an sickens and loses its life functions one by one. obstacle course of leaves, stems and roots Regardless of how healthy or alive your soil is through which the water must maneuver on right now, cover crops can play a vital role in its way downhill ensuring that your soil provides a strong founda - • Increase the soil’s ability to absorb and hold tion for your farming system. While the most com- water, through improvement in pore structure, mon reasons for including cover crops in a thereby preventing large quantities of water farming system may relate to the immediate short- from moving across the soil surface term need, the continued practice of cover crop- • Help stabilize soil particles in the cover crop ping becomes an investment in building healthy root system soil over the long term. Cover crops improve soil in a number of ways. The reduction in soil erosion due to cover crop- Protection against soil loss from erosion is per - ping will be roughly proportional to the amount haps the most obvious soil benefit of cover crops, of cover on the soil. The Revised Universal Soil but providing organic matter is a more long-term Loss Equation developed by the Natural and equally important goal. Cover crops con - Resources Conservation Service predicts that a tribute indirectly to overall soil health by catching soil cover of just 40 percent when winter arrives nutrients before they can leach out of the soil can reduce erosion substantially until spring. pro file or, in the case of legumes, by adding It’s worthwhile to get covers established early, nitrogen to the soil. Their roots can even help to ensure that maximum soil cover develops unlock some nutrients, converting them to more before winter rains. Consider overseeding covers available forms. Cover crops pro vide habitat or a at layby cultivation, aerial seeding or hand spread- food source for some important soil organisms, ing before harvest, or planting as soon as possible break up compacted layers in the soil and help after harvest. It’s always a good idea to maintain dry out wet soils. year-round soil cover whenever possible.

16 MANAGING COVER CROPS PROFITABLY ORGANIC MATTER ADDITIONS After the microorganisms have devoured the portions of the active fraction that are easiest to The benefits of organic matter include improved digest, a more dedicated subset of these micro- soil structure, increased infiltration and or ganisms will start munching on the more water-holding capacity, increased cation com plex and tough material, such as celluloses exchange capacity (the ability of the soil to act and lignins, the structural materials of plants. as a short-term storage bank for positively charged Since cel lulose is tougher than simple sugars, and plant nutrients) and more efficient long-term lignin breaks down very slowly, they contribute storage of nutrients. Without organic matter, you more to the humus or stable fraction. Humus is have no soil to speak of, only a dead mixture of responsi ble for giving the soil that rich, dark, ground-up and weathered rocks. spongy feel ing and for properties such as water Organic matter includes thousands of different retention and cation exchange capacity. substances derived from decayed leaves, roots, Plant materials that are succulent and rich microorganisms, manure and even groundhogs in proteins and sugars will release nutrients rapid - that died in their burrows. These substances func- ly but leave behind little long-term organic matter. tion in different ways to build healthy soil. Plant materials that are woodier or more Different plants leave behind different kinds of fibrous will release nutrients much more slowly, organic matter as they decompose, so your choice perhaps even tie up nutrients temporarily (see of cover crop will largely determine which soil Tillage, No Tillage and N Cycling, p. 21), but will benefits you will receive. promote more stable organic matter, or humus, Soil scientists may argue over how to classify leading to better soil physical conditions, the various soil organic components. Most will increased nutrient-holding capacity and higher agree, however, that there is a portion that can be cation exchange capacity. called the “active” fraction, and one that might In general, annual legumes are succulent. They be called the “stable” fraction, which is roughly release nitrogen and other nutrients quick ly equivalent to humus. There are many categories through the active fraction, but are not very effec- in between the active and stable fractions. tive at building up humus. Long-term use of annu- The active fraction represents the most easily al legumes can increase soil humus, however, decomposed parts of soil organic matter. It tends some research suggests (429). to be rich in simple sugars and proteins and con- Grains and other grasses and nonlegumes will sists largely of recently added fresh residues, contribute to humus production, but won’t micro bial cells and the simpler waste products release nutrients very rapidly or in large quantities from microbial decay. if incorporated as they approach matu rity. Because microorganisms, like human organ - Perennial legumes such as white and red clover isms, crave sweet stuff, compounds containing may fall in both categories—their leaves will simple sugars disappear quickly. Proteins also are break down quickly, but their stems and root selected quickly from the menu of edible soil systems may become tough and fibrous and can goodies. When these compounds are digested, con tribute to humus accumulation. many of the nutrients that they contain are released into the soil. Proteins are nitrogen-rich, so Cover Crops Help “Glue” Soil the active fraction is responsible for the release As soil microorganisms digest plant material, they of most N, as well as some K, P and other nutri- produce some compounds in addition to the ents, from organic matter into the soil. The easi- active and stable fractions of the organic matter. ly decomposed proteins and sugars burn up One group of these by-products is known as almost completely as energy sources, and don’t polysaccharides. These are complex sugars that leave much behind to contribute to organic act as glues in the soil to cement small soil parti - matter building. cles into clusters or aggregates. Many farmers

BUILDING SOIL FERTILITY AND TILTH 17 use the term “crumb” to describe soil clusters soil aggregates and the poor soil struc ture often about the size of a grain of rice. A well-aggregated seen in overtilled soil. or “crumby” soil—not to be confused with crum- When adding cover crops to a system, mini - my or depleted soil—has good aeration. It allows mize tillage to maximize the long-term soil bene - better infiltration and retention of water. fits. Many of the cover crops discussed in this Cover crops can promote good aggregation in book are ones you can seed into growing crops or the soil through increased production of these no-till plant into crop residues. Otherwise, the and other microbial glues. See Cover Crops Can gain in organic matter may be counteracted by Stabilize Your Soil (p. 19). Well-aggregated soils higher decomposition rates. also are less prone to compaction, which has been shown to reduce yields of vegetables such TIGHTENING THE NUTRIENT LOOP as snap beans, cabbage and cucumber by 50 percent or more (451). In addition to reducing topsoil erosion and As they decompose, leguminous cover crops improv ing soil structure, cover crops enhance seem to be better than grasses for production of nutrient cycling in your farming system by taking polysaccharides (9). However, polysaccharides up nutri ents that otherwise might leach out of the will decompose in a matter of months, so their soil pro file. These excess nutrients have the aggregation effect is likely to last only the season potential to pollute groundwater or local streams after the use of the cover crop. and ponds, not to mention impoverishing the soil Grass species also promote good aggregation, they came from. but by a different mechanism. Grasses have a Of the common plant nutrients, nitrogen in the ‘fibrous’ root system—made of numerous fine nitrate form is the most water-soluble and there - roots spreading out from the base of the plant. fore the most vulnerable to leaching. Anytime These roots may release compounds that help soil is bare and appreciable rain falls, nitrates are aggregate the soil between roots. on the move. Nitrate can be present in the soil at Organic matter builds up very slowly in the the end of a cropping season if the crop did not soil. A soil with 3 percent organic matter might use all the N applied. Decomposing organic mat - only increase to 4 percent after a decade or more ter (including plant residues, compost and animal of soil building. The benefits of increased organic manures) also can supply nitrate-N, as long as the matter, however, are likely to be apparent long soil temperature is above freezing. Even in a field before increased quantities are detectable. Some, where the yearly application of N is well-suited to such as enhanced aggregation, water infil tration crop needs, nitrates can accumulate after crops rates and nutrient release, will be apparent the are harvested and leach when it rains. first season; others may take several years to Cover crops reduce nitrate leaching in two become noticeable (429). ways. They soak up available nitrate for their Your tillage method is an important considera - own needs. They also use some soil moisture, tion when using cover crops to build soil, because reducing the amount of water available to leach tillage will affect the rate of organic matter accu - nutrients. mulation. It is difficult to build up organic mat- The best cover crops to use for nitrate conser - ter under conventional tillage regimes. Tillage vation are nonlegumes that form deep, extensive speeds up organic matter decomposition by root systems quickly after cash crops are harvest- exposing more surface area to oxygen, warm ing ed. For much of the continental U.S., cere al rye is and drying the soil, and breaking residue into the best choice for catching nutrients after a sum- smaller pieces with more surfaces that can be mer crop. Its cold tolerance is a big advantage that attacked by decomposers. Like fanning a fire, allows rye to continue to grow in late fall and put tillage rapidly “burns up” or “oxidizes” the fuel, down roots to a depth of three feet or more. which in this case is organic matter. The resulting Where winters are mild, rye can grow through the loss of organic matter causes the break down of winter months.

18 MANAGING COVER CROPS PROFITABLY Cover Crops Can Stabilize Your Soil The more you use cover crops, the better phosphorus that plants obtain. In return, the your soil tilth, research continues to show. fungi receive energy in the form of sugars One reason is that cover crops, especially that plants produce in their leaves and send legumes, encourage populations of beneficial down to the roots. fungi and other microorganisms that help Growing a cover crop increases the bind soil aggregates. abundance of mycorrhizal spores. Legumes in The fungi, called mycorrhizae, produce a particular can contribute to mycorrhizal water-insoluble protein known as glomalin, diversity and abundance, because their roots which catches and glues together particles of tend to develop large populations of these organic matter, plant cells, bacteria and other beneficial fungi. fungi (453). Glomalin may be one of the most By having their own mycorrhizal fungi and important substances in promoting and by promoting mycorrhizal relationships in stabilizing soil aggregates. subsequent crops, cover crops therefore can Most plant roots, not just those of cover play a key role in improving soil tilth. The crops, develop beneficial mycorrhizal overall increase in glomalin production also relationships. The fungi send out rootlike could help explain why cover crops can extensions called hyphae, which take up improve water infiltration into soil and water and soil nutrients to help feed plants. In enhance storage of water and soil nutrients, low-phosphorus soils, for example, the even when there has been no detectable hyphae can increase the amount of increase in the amount of soil organic matter.

Research with soil high in residual N in the generally on the express route with N. These mid-Atlantic’s coastal plain showed that cereal rye nutrients can be brought up from deeper soil lay - took up more than 70 lb. N/A in fall when plant - ers by any deep-rooted cover crop. The nutrients ed by October 1. Other grasses, including wheat, are then released back into the active organic oats, barley and ryegrass, were only able to take mat ter when the cover crop dies and decomposes. up about half that amount in fall. Legumes were Although phosphorus (P) doesn’t generally practically useless for this purpose in the leach, as it is only slightly water-soluble, cover Chesapeake Bay study (46). Legumes tend to crops may play a role in increasing its availability establish slowly in fall and are mediocre N scav- in the soil. Some covers, such as buckwheat and engers, as they can fix much of their own N. lupins, are thought to secrete acids into the soil To maximize N uptake and prevent leaching, that put P into a more soluble, plant-usable form. plant nonlegumes as early as possible. In the Some cover crops enhance P availability in above study, rye took up only 15 lb. N/A when another manner. The roots of many common planting was delayed until November. It is impor - cover crops, particularly legumes, house benefi - tant to give cover crops the same respect as any cial fungi known as mycorrhizae. The mycor - other crop in the rotation and plant them in a rhizal fungi have evolved efficient means of timely manner. absorbing P from the soil, which they pass on to their plant host. The filaments (hyphae) of these Not Just Nitrogen Cycling fungi effectively extend the root system and help Cover crops help bring other nutrients back into the plants tap more soil P. the upper soil profile from deep soil layers. Keeping phosphorus in an organic form is the Calcium and potassium are two macronutrients most efficient way to keep it cycling in the soil. So with a tendency to travel with water, though not the return of any plant or animal residue to the

BUILDING SOIL FERTILITY AND TILTH 19 soil helps maintain P availability. Cover crops also equal—some are genetically challenged when it help retain P in your fields by reducing erosion. comes to fixation. Beans (Phaseolus spp.) are notoriously incapable of a good symbiotic rela - Adding Nitrogen tionship and are rarely able to fix much more than One of nature’s most gracious gifts to plants and 40 lb. N/A in a whole season. Cowpeas (Vigna soil is the way that legumes, with the help of rhi - unguiculata) and vetches (Vicia spp.), on the zobial bacteria, can add N to enrich your soil. If other hand, are generally capable of high fixation you are not familiar with how this remarkable rates. Check Chart 2 Performances and Roles process works, see Nodulation: Match Inoculant (p. 67) and the sections on individual cover crops to Maximize N (p. 122). for information about their N-fixation potential. The nitrogen provided by N-fixation is used Even under the best of conditions, legumes efficiently in natural ecosystems, thanks to the rarely fix more than 80 percent of the nitrogen soil’s complex web of interacting physical, chem - they need to grow, and may only fix as much as 40 ical and biological processes. In an agricultural or 50 percent. The legume removes the rest of system, however, soil and crop management fac- what it needs from the soil like any other plant. tors often interfere with nature’s ultra-efficient Legumes have to feed the bacteria to get them to use of organic or inorganic N. Learning a bit about work, so if there is ample nitrate already available the factors affecting N-use efficiency from legume in the soil, a legume will remove much of that first plants will help build the most sustainable crop- before expending the energy to get N-fixation ping system possible within your constraints. going. In soils with high N fertility, legumes may fix little or no nitrogen. See How Much N? How Much N is Fixed? (p. 22). A number of factors determine how much of the N in your legume came from “free” N, fixed from While it is tempting to think of legume nodules as N2 gas: little fertilizer factories pumping N into the sur- • Is the symbiosis (the interdependence of rounding soil, that isn’t what happens. The fixed the rhizobia and the plant roots) effective? See N is almost immediately shunted up into the Nodulation: Match Inoculant to Maximize N stems and leaves of the growing legume to form (p. 122). Use the correct rhizobial inoculant for proteins, chlorophyll and other N-containing the legume you’re growing. Make sure it’s fresh, compounds. The fixed nitrogen will not become was stored properly, and that you apply it with an available to the next crop until the legume effective sticking agent. Otherwise, there will be decomposes. Consequently, if the aboveground few nodules and N-fixation will be low. part of the legume is removed for hay, the majori - • Is the soil fertile? N-fixation requires ty of the fixed nitrogen also leaves the field. molybdenum, iron, potassium, sul fur and zinc to What about the legume roots? Under condi - function properly. Soils depleted of these micro - tions favoring optimal N fixation, a good rule of nutrients will not support efficient fixation. Tissue thumb is to think of the nitrogen left in the plant testing your cash crops can help you decide if you roots (15 to 30 percent of plant N) as being need to adjust micronutrient levels. roughly equivalent to the amount the legume • Is the soil getting enough air? N-fixation removed directly from the soil, and the amount in requires that N-rich air get to the legume roots. the stems and leaves as being equivalent to what Waterlogging or compaction hampers the move - was fixed. ment of air into the soil. Deep-rooted cover crops Annual legumes that are allowed to flower and can help alleviate subsoil compaction (451). mature will transport a large portion of their bio- • Is the pH adequate? Rhizobia generally will mass nitrogen into the seeds or beans. Also, once not live long in soils below pH 5. the legume has stopped actively growing, it will • Does the legume/rhizobial pair have high fix - shut down the N-fixing symbiosis. In annual ation potential? Not all legumes were created legumes this occurs at the time of flowering; no

20 MANAGING COVER CROPS PROFITABLY additional N gain will occur after that point. Unless water, and declines significantly when mois ture you want a legume to reseed itself, it’s generally a levels are higher or lower (244). This 60 percent good idea to kill a legume cover crop in the early- water-filled pore space roughly corre sponds to to mid-blossom stage. You’ll have obtained maxi- field capacity, or the amount of water left in the mum legume N and need not delay planting of the soil when it is allowed to drain for 24 hours after following cash crop any further, aside from any a good soaking rain. period you may want for residue decomposition as Microbes are sensitive to soil chemistry as well. part of your seedbed preparation. Most soil bacteria need a pH of between 6 and 8 to perform at peak; fungi (the slow decomposers) How Nitrogen is Released are still active at very low pH. Soil microorganisms How much N will soil really acquire from a also need most of the same nutrients that plants legume cover crop? Let’s take it from the point of require, so low-fertility soils support smaller pop - a freshly killed, annual legume, cut down in its ulations of primary decomposers, compared with prime at mid-bloom. The management and climat- high-fertility soils. Don’t expect N-release rates or ic events following the death of that legume will fertilizer replacement values for a given cover greatly affect the amount and timing of N release crop to be identical in fields of different fertility. from the legume to the soil. Many of these environmental factors are out of Most soil bacteria will feast on and rapidly your direct control in the near term. Management decompose green manures such as annual factors such as fertilization, liming and tillage, legumes, which contain many simple sugars and however, also influence production and avail a bili - proteins as energy sources. Soil bacteria love to ty of legume N. party and when there is lots to eat, they do some - thing that no party guest you’ve ever invited can Tillage, No-Tillage and N-Cycling do—they reproduce themselves, rapidly and Tillage affects decomposition of plant residues in repeatedly, doubling their population in as little as a number of ways. First, any tillage increases soil seven days under field conditions (306). Even a contact with residues and increases the microbes’ relatively inactive soil can come to life quickly access to them. The plow layer is a hospitable with addition of a delectable green manure. environment for microbes, as they’re sheltered The result can be a very rapid and large release from extremes of temperature and moisture. of nitrate into the soil within a week of the green Second, tillage breaks the residue into smaller manure’s demise. This N release is more rapid pieces, providing more edges for microbes to when covers are plowed down than when left on munch. Third, tillage will temporarily decrease the the surface. As much as 140 lb. N/A has been density of the soil, generally allowing it to drain measured 7 to 10 days after plowdown of hairy and therefore warm up more quickly. All told, vetch (363). Green manures that are less protein- residues incorporated into the soil tend to decom- rich (N-rich) will take longer to release N. Those pose and release nutrients much faster than those that are old and fibrous or woody are gen erally left on the surface, as in a no-till sys tem. That’s not left for hard-working but somewhat slug gish fungi necessarily good news, however. to convert slowly to humus over the years, gradu- A real challenge of farming efficiently is to keep ally releasing small amounts of nutrients. as much of the N as possible in a stable, storable Other factors contribute significantly to how form until it’s needed by the crop. The best quickly a green manure releases its N. Weather has a storage form of N is the organic form: the unde - huge influence. The soil organisms respon sible for composed residue, the humus or the microorgan - decomposition work best at warm temperatures isms themselves. and are less energetic during cool spring months. Let’s consider the N contained in the microbes. Soil moisture also has a dramatic effect. Nitrogen is a nutrient the microbes need for build - Research shows that soil microbial activity peaks ing proteins and other compounds. Carbon-con- when 60 percent of the soil pores are filled with taining compounds such as sugars are mainly

BUILDING SOIL FERTILITY AND TILTH 21 How Much N? To find out if you might need more N than If the stand has less than 100 percent your green manure will supply, you need to groundcover, multiply by (the percent ground estimate the amount of N in your cover crop. cover / 100). In this example, for 60 percent To do this, assess the total yield of the green groundcover, you would obtain: manure and the percentage of N in the plants 3,800 x (60/100) = 2,280 lb. just before they die. Keep in mind that these are rough To estimate yield, take cuttings from several estimates to give you a quick guide for the areas in the field, dry and weigh them. Use a productivity of your green manure.To know yardstick or metal frame of known dimensions the exact percent N in your plant tissue, you (1 ft. x 2 ft., which equals 2 ft2 works well) would have to send it to a lab for analysis. and clip the plants at ground level within the Even with a delay for processing, the results known area. Dry them out in the sun for a few could be helpful for the crop if you use split consecutive days, or use an oven at about applications of N.Testing is always a good idea, 140° F for 24 to 48 hours until they are as it can help you refine your N estimates for “crunchy dry.” Use the following equation subsequent growing seasons. to determine per-acre yield of dry matter: The following rules of thumb may help here: Yield (lb.)/Acre = Total weight of dried samples (lb.) 43,560 sq. ft. • Annual legumes typically have between X # square feet you sampled 1 Acre 3.5 and 4 percent N in their aboveground While actually sampling is more accurate, parts prior to flowering (for young material, you can estimate your yield from the height of use the higher end of the range), and 3 to 3.5 your green manure crop and its percent percent at flowering. After flowering, N in the groundcover. Use these estimators: leaves decreases quickly as it accumulates in At 100 percent groundcover and 6-inch the growing seeds. height*, most nonwoody legumes will contain roughly 2,000 lb./A of dry matter. For each * For cereal rye, the height relationship is a bit different. Cereal rye additional inch, add 150 lb. So, a legume that is weighs approximately 2,000 lb./A of dry matter at an 8-inch height and 100 percent groundcover. For each additional inch, add 150 18 inches tall and 100 percent groundcover lb., as before, and multiply by (percent groundcover/100). For most will weigh roughly: small grains and other annual grasses, start with 2,000 lb./A at 6 Inches >6: 18 in.–6 in. = 12 in. inches and 100 percent ground cover. Add 300 lb. for each additional inch and multiply by (percent groundcover/100). x 150 lb./in.: 12 in. x 150 lb./in. = 1,800 lb. Add 2,000 lb.: 2,000 lb. + 1,800 lb. = 3,800 lb. energy sources, which the microorganisms use as Materials with a high carbon to nitrogen (C:N) fuel to live. The process of burning this fuel sends ratio, such as mature grass cover crops, straw or most of the carbon back into the atmos phere as any fibrous, woody residue, have a low N con tent. carbon dioxide, or CO2. They can “tie up” soil N, keeping it immo bilized Suppose a lot of new food is suddenly put into (and unavailable) to crops until the carbon “fuel the soil system, as when a green manure is supply” starts depleting. Tie-up may last for sever- plowed down. Bacteria will expand their popula- al weeks in the early part of the growing season, tions quickly to tap the carbon-based energy and crop plants may show the yellowing charac- that’s available. All the new bacteria, though, will teristic of N deficiencies. That is why it often need some N, as well as other nutri ents, for body makes sense to wait one to three weeks after building before they can even begin to eat. So any killing a low-N cover before planting the next newly released or existing mineral N in soil gets crop, or to supplement with a more readily avail- scavenged by new bacteria. able N source when a delay is not practical.

22 MANAGING COVER CROPS PROFITABLY • For perennial legumes that have a Of course, cover crops will not be the only significant number of thick, fibrous or woody N sources for your crops. Your soil will release stems, reduce these estimates by 1 percent. between 10 and 40 lb. N/A for each 1 percent • Most cover crop grasses contain 2 to 3 organic matter. Cold, wet clays will be at the percent N before flowering and 1.5 to 2.5 low end of the scale and warm, well-drained percent after flowering. soils will be at the high end. You also may • Other covers, such as brassicas and receive benefits from last year’s manure, green buckwheat, will generally be similar to, or manure or compost application. slightly below, grasses in their N content. To Other tools could help you refine your put it all together: nitrogen needs. On-farm test strips of cover Total N in green manure (lb./A) = yield (lb./A) x % N crops receiving different N rates would be an 100 example. Refer to Appendix A, Testing Cover Crops on Your Farm (p. 189) for some tips on To estimate what will be available to your designing an on-farm trial. In some regions, a crop this year, divide this quantity of N by: pre-sidedress N test in spring could help you • 2, if the green manure will be conventionally estimate if supplemental N will be cost- tilled; effective. Bear in mind that pre-sidedress • 4, if it will be left on the surface in a no-till testing does not work well when fresh plant system in Northern climates; residues have been turned in—too much • 2, if it will be left on the surface in a no-till microbial interference relating to N tie-up may system in Southern climates. give misleading results. For more information on determining your Bear in mind that in cold climates, N will N from green manures and other amendments, mineralize more slowly than in warm climates, see the Northeast Cover Crop Handbook as discussed above. So these are gross (361). estimates and a bit on the conservative side. —Marianne Sarrantonio, Ph.D.

Annual legumes have low C:N ratios, such as the mixtures. This can be an effec tive manage- 10:1 or 15:1. When pure stands of annual legumes ment tool to reduce leaching while making the N are plowed down, the N tie-up may be so brief more available to the next crop. you will never know it occurred. Mixed materials, such as legume-grass mixtures, Potential Losses may cause a short tie-up, depending on the C:N A common misunderstanding about using green ratio of the mixture. Some N storage in the micro - manure crops is that the N is used more efficient- bial population may be advantageous in keeping ly because it’s from a plant source. This is not nec- excess N tied up when no crop roots are there to essarily true. Nitrogen can be lost from a green absorb it. manure system almost as easily as from chemical Fall-planted mixtures are more effective in fertilizers, and in comparable amounts. The reason mopping up excess soil N than pure legumes and, is that the legume organic N may be converted to as stated earlier, the N is mineralized more rapidly ammonium (NH4), then to ammonia (NH3) or from mixtures than from pure grass. A fall-seeded nitrate (NO3) before plants can take it up. Under mixture will adjust to residual soil N levels. When no-till systems where killed cover crops remain the N levels are high, the grass will dominate and on the surface, some ammonia (NH3) gas can be when N levels are low, the legume will dominate lost right back into the atmosphere.

BUILDING SOIL FERTILITY AND TILTH 23 Nitrate is the form of N that most plants prefer. organic form for gradual release in a number of Unfortunately, it is also the most water-soluble subsequent growing seasons. form of N. Whenever there is more nitrate than plant roots can absorb, the excess may leach with OTHER SOIL-IMPROVING BENEFITS heavy rain or irrigation water. As noted earlier, nitrates in excess of 140 lb./A Cover crops can be very useful as living plows to may be released into warm, moist soil within as lit tle penetrate and break up compacted layers in the as seven to 10 days after plowing down a high-N soil. Some of the covers discussed in this book, legume, such as a hairy vetch stand. Since the fol- such as sweetclover and forage radish, have roots lowing crop is unlikely to have much of a root sys- that reach as deep as three feet in the soil with- tem at that point, the N has a ticket for Leachville. in one crop ping season. The action of numerous Consider also that the green manure may have been pointy little taproots with the hydraulic force of plowed down to as deep as 12 inches—much deep- a deter mined plant behind them can penetrate er than anyone would con sider applying chemical soil where plowshares fear to go. Grasses, with fertilizer. Moreover, green manures sometimes con- their tremendously extensive root systems, may tinue to decom pose after the cash crop no longer relieve compacted surface soil layers. Sorghum - needs N. This N also is prone to leaching. sudangrass can be managed to powerfully frac - To summarize, conventional plowing and aggres- ture subsoil. See Summer Covers Relieve sive disking can cause a rapid decomposi tion of Compaction (p. 110). green manures, which could provide too much N One of the less appreciated soil benefits of too soon in the cropping season. No-till systems will cover crops is an increase in the total numbers have a reduced and more gradual release of N, and diversity of soil organisms. As discussed ear - but some of that N may be vulnera ble to gaseous lier, diversity is the key to a healthy, well-func - loss, either by ammonia volatiliza tion or by deni - tioning soil. Living covers help supply trification, which occurs when NO3- converts to year-round food for organisms that feed off root gases under low O2 (flooded) conditions. Thus, by-products or that need the habitat provided on depending on management, soil and weather situa- a residue-littered soil surface. Dead covers sup- tions, N from legume cover crops may not be more ply a more varied and increased soil diet for efficiently used than N from fertilizer. many organisms. Some possible solutions to this cover crop Of course, unwanted pests may be lured to the nitrogen-cycling dilemma: field. Effective crop rotations that include cover • A shallow incorporation of the green manure, crops, however, tend to reduce rather than as with a disk, may reduce the risk of gaseous loss. increase pest concerns. Pest-management consid - • It may be feasible to no-till plant or transplant erations due to the presence of a cover crop are into the green manure, then mow or incorporate discussed in the next chapter, Managing Pests it between the rows 10-14 days later, when cash with Cover Crops (p. 25). crop roots are more developed and able to take Finally, cover crops may have an added advan - up N. This has some risk, especially when soil tage of drying out and therefore warming soils moisture is limiting, but can provide satisfactory during a cold, wet season. The flip side of this is results if seedling survival is assured. that they may dry the soil out too much and rob • Residue from a grass/legume mix will have a the following crop of needed moisture. higher C:N than the legume alone, slowing the There are no over-the-counter elixirs for renew - release of N so it’s not as vulnerable to loss. ing soil. A long-term farm plan that includes cover crops, however, can help ensure your soil’s health Consider also that some portion of the N in the and productivity for as long as you farm. green manure will be conserved in the soil in an

24 MANAGING COVER CROPS PROFITABLY MANAGING PESTS WITH COVER CROPS By Sharad C. Phatak and Juan Carlos Diaz-Perez

over crops are poised to play increasingly of trees or pastures for at least 10 years remains important roles on North American farms. productive for row crops and vegetables for the CIn addition to slowing erosion, improving first two to three years. High yields of agronomic soil structure and providing fertility, we are learn - and horticultural crops are profitable, with coming how cover crops help farmers to manage paratively few pesticide and fertilizer inputs. pests (390). With limited tillage and careful atten- After that period—under conventional systems tion to cultivar choice, placement and timing, with cus tomary clean tillage—annual crops cover crops can reduce infestations by insects, require higher inputs. The first several years of diseases, nematodes and weeds. Pest-fighting excessive tillage destroys the food sources and cover crop systems help minimize reliance on micro-niches on which the soil organisms that pesticides, and as a result cut costs, reduce your help suppress pests depend. When protective nat- chemical expo sure, protect the environment, and ural biological systems are disrupted, pests have increase con sumer confidence in the food you new openings and crops are much more at risk. produce. Cover crop farming is different from clean-field Farmers and researchers are using cover crops monocropping, where perfection is rows of corn to design new strategies that preserve a farm’s or cotton with no thought given to encouraging natural resources while remaining profitable. Key biological diversity. Cover crops bring more forms to this approach is to see a farm as an “agro - of life into the picture and into your management ecosystem”—a dynamic relationship of the min - plan. By working with a more diverse range of eral, biological, weather and human resources crops, some growing at the same time in the same involved in producing crops or livestock. Our field, you’ve got a lot more options. Here’s a quick goal is to learn agricultural practices that are envi- overview of how these systems work. ron mentally sound, economically feasible and socially acceptable. Insect Management Environmentally sustainable pest management In balanced ecosystems, insect pests are kept in starts with building healthy soils. Research in check by their natural enemies (409). These nat- south Georgia (see Georgia Cotton, Peanut ural pest control organisms —called beneficials in Farmers, p. 26) shows that crops grown on bio- agricultural systems—include predator and para- logically active soils resist pest pressures better sitoid insects and diseases. Predators kill and eat than those grown on soils of low fertility, extreme other insects; parasitoids spend their larval stage pH, low biological activity and poor soil structure. inside another insect, which then dies as the There are many ways to increase biological invader’s larval stage ends. However, in conven- activity in soil. Adding more organic material by tional agricultural systems, synthetic chemical growing cover crops or by applying manure or treatments that kill insect pests also typically kill compost helps. Reducing or eliminating pesti- the natural enemies of the insects. Conserving cides favors diverse, healthy populations of bene- and encouraging beneficial organisms is a key to ficial soil flora and fauna. So does reducing or achieving sustainable pest management. eliminating tillage that causes losses of soil struc- You should aim to combine strategies that ture, biological life or organic matter. These losses make each farm field more hospitable to benefi- make crops more vulnerable to pest damage. cials. Reduce pesticide use, and, when use is Farming on newly cleared land shows the essential, select materials that are least harmful to process well. Land that has been in a “cover crop” beneficials. Avoid or minimize cultural practices

MANAGING PESTS WITH COVER CROPS 25 Georgia Cotton, Peanut Farmers Use Cover Crops to Control Pests TIFTON, Ga.—Here in southwestern Georgia, I’m Spring—Strip-till rows 18 to 24 inches wide, working with farmers who have had dramatic leaving the cover crop growing between the success creating biologically active soil in fields strips. Three weeks later, plant cotton. that have been conventionally tilled for genera- • Year 2. Fall—Replant cereal rye or cahaba tions. We still grow the traditional cash crops of vetch, allow crimson or subclover hard seed to cotton and peanuts, but with a difference. We’ve germinate. added cover crops, virtually eliminated tillage, and Spring—Strip-till cotton. added new cash crops that substitute for cotton • Year 3. Fall—Plant rye. and peanuts some years to break disease cycles Spring—Desiccate rye with herbicides. and allow for more biodiversity. No-till plant peanuts. Our strategies include no-till planting (using • Year 4. The cycle starts again at year 1. modified conventional planters), permanent planting beds, controlled implement traffic, Vegetable farmers frequently use fall-planted crop rotation and annual high-residue winter cereal rye plowed down before vegetables, or cover crops. We incorporate fertilizer and lime crimson clover strip-tilled before planting veg- prior to the first planting of rye in the conver- etables. The crimson clover matures, drops hard sion year. This is usually the last tillage we plan seed, then dies. Most of the seed germinates in to do on these fields for many years. Together, the fall. Cereal/legume mixes have not been these practices give us significant pest manage- more successful than single-crop cover crop ment benefits within three years. plantings in our area. Growers are experimenting with a basic win- Some vegetable farmers strip-till rows into ter cover crop>summer cash crop rotation. Our rye in April. The strips are planted in early May cover crops are ones we know grow well here. to Southern peas, lima beans or snap beans. Rye Rye provides control of disease, weed and in row middles will be dead or nearly dead. Rye nematode threats. Legume crops are crimson or crimson clover can continue the rotation. clover, subterranean clover or cahaba vetch. Vegetable farmers also broadcast crimson They are planted with the rye or along field bor- clover in early March. They desiccate the cover, ders, around ponds, near irrigation lines and in strip-till rows, then plant squash in April. The other non-cropped areas as close as possible to clover in the row middles will set seed then die fields to provide the food needed to support back through summer. The crimson strips will beneficials at higher populations. begin to regrow in the fall from the dropped When I work with area cotton and peanut seed, and fall vegetables may be planted in the growers who want to diversify their farms, we tilled areas after the July squash harvest. set up a program that looks like this: Insecticide and herbicide reduction begins • Year 1 . Fall—Adjust fertility and pH the first year, with no applications needed by according to soil test. Deep till if necessary to the third or fourth year in many cases. relieve subsurface soil compaction. Plant a The farmers get weed control by flail mow- cover crop of rye, crimson clover, cahaba vetch ing herbicide-killed, fall-planted rye, leaving or subterranean clover. about 6 inches of stubble. Alternatively, they such as tilling and burning that kill beneficials and By including cover crops in your rotations and destroy their habitat. Build up the sustenance and not spraying insecticides, beneficials often are habitat that beneficials need. Properly managed cover already in place when you plant spring or sum- crops supply moisture, physical niches and food in mer crops. However, if you fully incorporate cover the form of insects, pollen, honeydew and nectar. crops into the soil, you destroy or disperse most

26 MANAGING COVER CROPS PROFITABLY could use a roller to kill the rye crop. One or • Weeds. Strip-tilling into over-wintered two post-emerge herbicide applications should cover crops provides acceptable weed control suffice in the first few years. I don’t recom- for relay-cropped cucumbers (325). Convent - mend cultivation for weed control because it ional management of rye in our area is usually increases risks of soil erosion and damages the to disk or kill it with broad-spectrum herbi- protective outer leaf surface layer (cuticle) that cides such as paraquat or glyphosate. Rye can helps prevent plant diseases. also be killed with a roller, providing an accept- We see changes on farms where the rota- able level of weed control for the subsequent tions stay in place for three or more years: cash crop. • Insects. Insecticide costs under con- • Diseases. I’ve been strip-tilling crimson servation tillage are $50 to $100/A less clover since 1985 to raise tomatoes, peppers, than conventional crop management in the eggplant, cucumbers, cantaloupes, lima beans, area for all kinds of crops. The farmers using snap beans, Southern peas and cabbages. I’m the alternative system often substitute with using no fungicides. Our research staff has insect control materials such as Bacillus raised peanuts no-tilled into cereal rye for the thuringiensis (Bt), pyrethroids, and insect past six years, also without fungicides. growth regulators that have less severe envi- • Nematodes. If we start on land where pest ronmental impact than chemical pesticides. nematodes are not a major problem, this system These products are less persistent in the field keeps them from becoming a limiting factor. environment, more targeted to specific pests and do less harm to beneficials. By planting Even though the conventional wisdom says cover crops on field edges and in other you can’t build organic matter in our climate non-crop areas, these farmers are increasing and soils, we have top-inch readings of 4 per- the numbers of beneficials in the field cent organic matter in a field that tested 0.5 environments. percent four years ago. Pests that are no longer a problem on the We are still learning, but know that we can cover-cropped farms include thrips, bollworm, rotate crops, use cover crops and cut tillage to budworm, aphids, fall armyworm, beet army- greatly improve our sustainability. In our expe- worm and white flies. On my no-till research rience, we’ve reduced total costs by as much as plots with cover crops and long rotations, I’ve $200 per acre for purchased inputs and tillage. not used insecticides for six years on peanuts, Parts of our system will work in many places. for eight years on cotton and for 12 years on Experiment on a small scale to look more vegetables. I’m working with growers who use closely at what’s really going in your soil and cover crops and crop rotations to economic - on your crops. As you compare insights and ally produce cucumbers, squash, peppers, egg- share information with other growers and plant, cabbage, peanuts, soybeans and cotton researchers in your area, you’ll find cover crops with only one or two applications of insecti- that help you control pests, too. cide—sometimes with none. —Sharad C. Phatak of the beneficials that were present. Conservation Cover crops left on the surface may be living, tillage is a better option because it leaves more of temporarily suppressed, dying or dead. In any the cover crop residue on the surface. No-till event, their presence protects beneficials and planting only disturbs an area 2 to 4 inches wide, their habitat. The farmer-helpful organisms are while strip-till ing disturbs an area up to about 24 hungry, ready to eat the pests of cash crops that inches wide between undisturbed row middles. are planted into the cover-crop residue. The ulti-

MANAGING PESTS WITH COVER CROPS 27 mate goal is to provide year-round food and habi- • Lady beetles in cover crop systems help to tat for beneficials to ensure their presence within control aphids attacking many crops. or near primary crops. We’re just beginning to understand the effects Properly selected and managed, cover crops can of cropping sequences and cover crops on bene - enhance the soil and field environment to favor ficial and insect pest populations. Researchers beneficials. Success depends on properly manag- have found that generalist predators, which ing the cover crop species matched with the cash feed on many species, may be an important bio- crops and anticipated pest threats. While we don’t logical control. During periods when pests are yet have prescription plantings guaranteed to scarce or absent, several important generalist bring in all the needed benefi cials—and only ben- predators can subsist on nectar, pollen and alter- eficials—for long lists of cash crops, we know native prey afforded by cover crops. This suggests some associations: you can enhance the biological control of pests • We identified 13 known beneficial insects by using cover crops as habitat or food for the associated with cover crops during one growing beneficials in your area. season in south Georgia vegetable plantings (53, This strategy is important for farmers in the 55, 57). South, where pest pressure can be especially • In cotton fields in south Georgia where heavy. In south Georgia, research showed that residues are left on the surface and insecticides populations of beneficial insects such as insidious are not applied, more than 120 species of benefi - flower bugs (Orius insidiosus), bigeyed bugs cial arthropods, spiders and ants have been (Geocoris spp.) and various lady beetles observed. (Coleoptera coccinellidae) can attain high densi - • Fall-sown and spring-sown insectory mixes ties in various vetches, clovers and certain crucif - with 10 to 20 different cover crops work well erous crops. These predators subsisted and under orchard systems. These covers provide reproduced on nectar, pollen, thrips and aphids, habitat and alternative food sources for beneficial and were established before key pests arrived. insects. This approach has been used successfully Research throughout Georgia, Alabama and by California almond and walnut growers partici - Mississippi showed that when summer vegetables pating in the Biologically Intensive Orchard were planted amid “dying mulches” of cool-season Systems (BIOS) project of the University of cover crops, some beneficial insects moved in to California (184). attack crop pests. When crops are attacked by pests, they send chemical signals that attract beneficial insects. The beneficials move in to find their prey (420). Maximizing natural predator-pest interaction is the primary goal of biologically based Integrated Pest Management (IPM), and cover crops can play a leading role. For example: • Colorado potato beetles were observed at 9 a.m. attacking eggplant that had been strip-till planted into crimson clover. By noon, assassin bugs had clustered around the feeding beetles. The beneficial bugs destroyed all the beetles by evening. • Cucumber beetles seen attacking cucumber plants were similarly destroyed by beneficials within a day. BUCKWHEAT grows quickly in cool, moist weather.

28 MANAGING COVER CROPS PROFITABLY The level of ecological sustainability depends In the field, although Cover crops on the grower’s interests, management skills and plants are exposed to a can enhance situation. Some use no insecticides while others wide diversity of micro - have substantially reduced insecticide applica - organisms, plant infec- the soil and field tions on peanut, cotton and vegetable crops. tion by microorganisms • In Georgia, Mississippi and South Carolina, is rare (314). A patho- environment to minimally tilled crimson clover or cahaba vetch gen has to cross many favor beneficial before cotton planting have been successful in plant barriers before it reducing fertilizer N up to 50 percent and insecti - can cause disease to insects. cide inputs by 30 to 100 percent. roots, stem or leaves. • Many farmers are adopting a system of trans - You can use cover planting tomatoes, peppers and eggplant into a crops to reinforce two of these barriers. killed hairy vetch or vetch/rye cover crop. Plant cuticle layer. This often waxy surface Benefits include weed, insect and dis ease sup- layer is the first physical barrier to plant pene- pression, improved fruit quality and overall lower tration. Many pathogens and all bacteria enter production cost. the plant through breaks, such as wounds, or nat- • Leaving “remnant strips” of a cover when ural openings, such as stomata, in this cuticle most of the crop is mowed or incorporated pro- layer. This protective layer can be physically vides a continuing refuge and food source for ben- dam aged by cultivation, manipulation, spraying eficials, which might otherwise leave the area or and sand-blasting from wind erosion, as well as die. This method is used in orchards when con- by the impact and soil splashing from raindrops tinued growth of cover crops would cause mois- and overhead irrigation. Spray adjuvants may ture competition with trees. also damage the waxes of the cuticle resulting in • Insect movement is orchestrated in a system more disease, as with Botritys cinerea rot in developed by Oklahoma State University for grapes (356, 367). In well-developed minimum- pecan growers. As legume mixtures senesce, ben- till or no-till crop systems with cover crops, you eficials migrate into trees to help suppress harm- may not need cultivation for weed control (see ful insects. Not mowing the covers from August 1 below) and you can mini mize spraying. Organic until shuck split of the developing pecans lessens mulches form living, dying or killed covers that the unwanted movement of stink bugs, a pest hold soil, stop soil splash ing and protect crops which can damage green pecans (261). In from injury to the cuticle. California, lygus bugs on berseem clover or alfalfa Plant surface microflora. Many benign are pests of cash crops. Be careful that cover crop organ isms are present on the leaf and stem sur- maturity or killing a cover doesn’t force pests into face. They compete with pathogens for a limited a neighboring cash crop. sup ply of nutrients. Some of these organisms produce natural antibiotics. Epiphytic bacteria adhere Disease Management to plant surfaces forming multicellular structures Growers traditionally have been advised to turn known as biofilms (339). These biofilms play an under plant debris by moldboard plowing to min- important role in plant disease. Pesticides, soaps, imize crop losses due to diseases (321, 322, 403, surfactants, spreaders and sticking agents can kill 405, 406). Now we realize that burying cover crop or disrupt these beneficial microorganisms, weak- residues and disrupting the entire soil profile ening the plant’s defenses against pathogens eliminates beneficial insect habitats and the bene- (356, 367). Cover crops can help this natural profits of weed control by crop residues. The tection process work by reducing the need for increased use of conservation tillage increases the application of synthetic crop protection materi- need to manage crop disease with out burying als. Further, cover crop plant surfaces can support cover crops. healthy populations of beneficial microorgan-

MANAGING PESTS WITH COVER CROPS 29 Select Covers that Balance Pests, Problems of Farm Many crops can be managed as cover crops, but including cotton, soybean and most vegetables. only a few have been studied specifically for Rye will not control weedy grasses. Because it their pest-related benefits on cash crops and can increase numbers of cut worms and wire field environments. worms in no-till planting conditions, rye is not Learn all you can about the impacts of a the most suitable cover where those worms are cover crop species to help you manage it in a problem ahead of grass crops like corn, sweet your situation. Here are several widely used corn, sorghum or pearl millet. cover crops described by their effects under • Wheat (Triticum aestivum)—A winter conservation tillage in relation to insects, annual grain, wheat is widely adapted and diseases, nematodes and weeds. works much like rye in controlling diseases, • Cereal Rye (Secale cereale)—This winter nematodes and broadleaf weeds. Wheat is not annual grain is perhaps the most versatile cover as effective as rye in controlling weeds because crop used in the continental United States. it produces less biomass and has less allelo- Properly managed under conservation tillage, pathic effect. rye has the ability to reduce soil-borne diseases, • Crimson Clover (Trifolium incarnatum) nematodes and weeds. Rye is a non-host plant —Used as a self-reseeding winter annual legume for root-knot nematodes and soil-borne dis- throughout the Southeast, fall-planted crimson eases. It produces significant biomass that clover supports and increases soil-borne dis- smothers weeds when it is left on the surface eases, such as the pythium-rhizoctonia complex, and also controls weeds allelopathically and root-knot nematodes. It suppresses weeds through natural weed-suppressing compounds. effectively by forming a thick mulch. Crimson As it grows, rye provides habitat, but not clover supports high densities of beneficial food, for beneficial insects. Thus, only a small insects by providing food and habitat. Because number of beneficial insects are found on rye. some cultivars produce “hard seed” that resists Fall-planted rye works well in reducing soil- immediate germination, crimson clover can be borne diseases, root-knot nematodes and managed in late spring so that it reseeds in late broadleaf weeds in all cash crops that follow, summer and fall. isms, including types of yeasts that can migrate experience on south Georgia farms and research onto a cash crop after planting or transplanting. plots shows. Increased soil organic matter levels Soilborne pathogenic fungi limit production of may help in reducing plant disease incidence and vegetables and cotton in the southern U.S. (404, severity by enhancing natural disease suppression 405, 406, 407). Rhizoctonia solani, Pythium (252, 424). myriotylum, Pythium phanidermatum and In soils with high levels of disease inoculum, Pythium irregulare are the most virulent patho - however, it takes time to reduce population lev els genic fungi that cause damping-off on cucum- of soil pathogens using only cover crops. After bers, snap beans, and other vegetables. Sclerotium tests in Maine with oats, broccoli, white lupine rolfsii causes rot in all vegetables and in peanuts (Lupinus albus) and field peas (Pisum sativum) and cotton. Infected plants that do not die may be researchers cautioned it may take three to five stunted because of lesions caused by fungi on pri- years to effectively reduce stem lesion losses on mary or secondary roots, hypocotyls and stems, potatoes caused by R. solani (240).Yet there are and may have reduced yields of low quality. But single-season improve ments, too. For example, in after two or three years in cover cropped, no-till an Idaho study, Verticillium wilt of potato was systems, damping-off is not a serious disease, as reduced by 24 to 29 percent following sudangrass

30 MANAGING COVER CROPS PROFITABLY • Subterranean Clover (Trifolium subter- system substantially reduces root-knot nema- raneum)—A self-reseeding annual legume, fall- todes, soil-borne diseases and broadleaf weeds. planted subterranean clover carries the same By using clovers and vetches in your fields and risks as crimson clover with soil-borne diseases adding beneficial habitat in non-cultivated and nematodes. It suppresses weeds more areas, you can increase populations of benefi- effectively in the deep South, however, because cial insects that help to keep insects pests of its thick and low growth habit. Subclover under control. Mixed plantings of small grains supports a high level of beneficial insects. and legumes combine benefits of both while • Cahaba White Vetch (Vica sativa X V. reducing their shortcomings. cordata)—This cool-season annual legume is a As pesticides of all types (fungicides, herbi- hybrid vetch that increases soilborne diseases cides, nematicides and insecticides) are yet suppresses root-knot nematodes. It supports reduced, the field environment becomes beneficial insects, yet attracts very high num- increasingly resilient in keeping pest outbreaks bers of the tarnished plant bug, a serious pest. in check. Plantings to further increase benefi- • Buckwheat (Fagopyrum esculentum)— A cial habitat in non-cultivated areas can help summer annual non-legume, buckwheat is very maintain pollinating insects and pest predators, effective in suppressing weeds when planted but should be monitored to avoid build-ups of thickly. It also supports high densities of benefi- potential pests. Researchers are only beginning cial insects. It is suitable for sequential planting to understand how to manage these “insectary around non-crop areas to provide food and plantings.” habitat for beneficial insects. It is very attractive Editor’s Note: Each cover crop listed here, to honeybees. except for cahaba vetch, is included in the charts (p. 62 and following) and is fully A well-planned crop rotation maximizes bene- described in its respective section. Check the fits and compensates for the risks of cover Table of Contents (p. 4) for location. crops and cash crops. Planting rye in a no-till —Sharad C. Phatak green manure. Yield of U.S. No.1 potatoes If the community of nematodes contains increased by 24 to 38 percent compared with diverse species, no single species will dominate. potatoes following barley or fallow (394). This coexistence would be the case in the undis turbed field or woodland described above. Nematode Management In conventional crop systems, pest nematodes Nematodes are minute roundworms that interact have abundant food and the soil environment is directly and indirectly with plants. Some species conducive to their growth. This can lead to rapid feed on roots and weaker plants, and also intro duce expansion of plant parasitic species, plant disease disease through feeding wounds. Most nematodes and yield loss. Cropping systems that increase bio- are not plant parasites, but feed on and interact logical diversi ty over time usually prevent the onset with many soil-borne microorganisms, including of nematode problems. Reasons may include a fungi, bacteria and protozoa. Damage to the crop dynamic soil ecological balance and improved, from plant-parasitic nematodes results in a break - healthier soil structure with higher organic matter down of plant tissue, such as lesions or yellow (5, 245, 424). In Michigan, to limit nematodes foliage; retarded growth of cells, seen as stunted between potato crops, some potato growers report growth or shoots; or excessive growth such as root that two years of radish improves potato produc- galls, swollen root tips or unnatural root branching. tion and lowers pest control costs (270, 271).

MANAGING PESTS WITH COVER CROPS 31 Once a nematode species is established in a depth of several inches suppressed Columbia field, it is usually impossible to eliminate it. Some lance nematodes in North Carolina cotton fields covers can enhance a resident parasitic nematode better than if the cover was buried more deeply population if they are grown before or after by moldboard plowing. Associated greenhouse another crop that hosts a plant-damaging nema - tests in the study showed that incorporated rye tode species. was effective against root-knot, reniform and stub - If a nematode pest species is absent from the by root nematodes, as well (20). soil, planting a susceptible cover crop will not Malt barley, corn, radishes and mustard some times give rise to a problem, assuming the species is not worked as well as the standard nematicide to control introduced on seed, transplants or machinery sugar beet nematode in Wyoming sugar beets, a (357). Iowa farmer Dick Thompson reports that 1994 study showed. Increased production more researchers analyzing his fields found no evidence than offset the cover crop cost, and lamb grazing of that hairy vetch, a host for soybean cyst nema- the brassicas increased profit without diminishing tode, caused any problem with the pest in his nematode suppression. The success is conditional soy beans. This may be due to his use of compost upon a limited nematode density. The cover crop in strip-cropped fields with an oats/hairy treatment was effective only if there were fewer vetch>corn>soybean rotation. than 10 eggs or juveniles per cubic centimeter of You can gradually reduce a field’s nematode soil. A moderate sugar beet nematode level was pest population or limit nematode impact on reduced 54 to 75 percent in about 11 weeks, increas- crops by using specific cover crops. Nematode ing yield by nearly 4 tons per acre (231). control tactics involving covers include: • Manipulating soil structure or soil humus Weed Management • Rotating with non-host crops Cover crops are widely used as smother crops to • Using crops with nematicidal effects, such as shade and out-compete weeds (412). Cereal brassicas grains establish quickly as they use up the moisture, fer tility and light that weeds need to survive. Cover crops may also improve overall plant vitali- Sorghum-sudangrass hybrids and buckwheat are ty to lessen the nematode impact on yield. But if warm-season crops that suppress weeds through you suspect nematode trouble, send a soil sample these physical means and by plant-produced nat- for laboratory analysis to positively identi fy the ural herbicides (allelopathy). nematode species. Then be sure any cover crops Cereal rye is an overwintering crop that sup - you try aren’t alternate hosts for that pest species. presses weeds both physically and chemically. If Area IPM specialists can help you. rye residue is left on the soil surface, it releases Using brassicas and many grasses as cover allelochemicals that inhibit seedling growth of crops can help you manage nematodes. Cover many annual small-seeded broadleaf weeds, such crops with documented nematicidal properties as pigweed and lambsquarters. The response of against at least one nematode species include grassy weeds to rye is more variable. Rye is a sorghum-sudangrass hybrids (Sorghum bicolor X major com ponent in the killed organic mulches S. bicolor var. sudanese), marigold (Tagetes patu- used in no-till vegetable transplanting systems. la), hairy indigo (Indigofera hirsuta), showy cro- Killed cover crop mulches last longer if the talaria (Crotolaria spectabilis), sunn hemp stalks are left intact, providing weed control well (Crotalaria juncea), velvetbean (Mucuna into the season for summer vegetables. Two deeringiana), rapeseed (Brassica rapa), mustards implements have been modified specifically to and radish (Raphanus satiuus). enhance weed suppression by cover crops. The You must match specific cover crop species undercutter uses a wide blade to slice just under with the particular nematode pest species, then the surface of raised beds, sev ering cover crop manage it correctly. For example, cereal rye plants from their root mass. An attached rolling residue left on the surface or incorporated to a harrow increases effectiveness (95, 96, 97). A

32 MANAGING COVER CROPS PROFITABLY Buffalo rolling stalk chopper does no direct tillage, but aggressively bends and cuts crops at the surface (303). Both tools work well on most legumes when they are in mid-bloom stage or beyond. Killed mulch of a cover crop mix of rye, hairy vetch, crimson clover and barley kept processing tomatoes nearly weed-free for six weeks in an Ohio test. This length of time is significant, because other research has shown that tomato fields kept weed-free for 36 days yield as much as fields kept weed-free all season (97, 150). The roller is another method used to terminate the CRIMSON CLOVER, a winter annual legume, grows cover crop (13). The roller flattens and crimps rapidly in spring to fix high levels of nitrogen. the cover crop, forming a flat mat of cover crop residue that effectively control weeds. sea son. For example, shade-tolerant legumes such Cover crops can also serve as a “living mulch” as red clover or sweetclover that are planted with to manage weeds in vegetable production. Cover spring grains grow rapidly after grain harvest to crops are left to grow between rows of the cash prevent weeds from dominating fields in late sum - crop to suppress weeds by blocking light and out- mer. Overseeding annual ryegrass or oats at soy - competing weeds for nutrients and water. They bean leaf yellowing provides a weed-suppressing may also provide organic matter, nitro gen (if cover crop before frost and a light mulch to sup - legumes) and other nutrients mined from under- press winter annuals, as well. neath the soil surface, beneficial insect habitat, Healthy soils grow healthy weeds as well as erosion prevention, wind protection and a tough healthy crops, making it difficult to manage weeds sod to support field traffic. in conservation tillage without herbicides. Long To avoid competition with the cash crop, living term strategies for weed management should mulches can be chemically or mechanically sup- include: pressed. In the Southeast, some cool-season cover • Reducing the weed seed bank crops such as crimson clover die out natu rally • Preventing weeds from going to seed during summer crop growth and do not compete • Cleaning equipment before moving to differ- for water or nutrients. However, cover crops that ent fields and farms regrow during spring and summer—such as sub- • Planting cover crops to help manage weeds in terranean clover, white clover and red clover— conservation tillage can compete strongly for water with spring- planted crops unless the covers are ade quately Cover crops can play a pest-suppressing role on suppressed. virtually any farm. As we find out more about In New York, growing cover crops overseeded the pest management benefits of cover crop sys - within three weeks of potato planting provided tems, they will become even more attractive from good weed suppression, using 70 percent less both an economic and an environmental per- herbicide. Yield was the same as, or moderately spective. Traditional research will identify some reduced from, the standard herbicide control new pieces of these biologically based systems. plots in the two-year study. Hairy vetch, woolly- However, growers who understand how all pod vetch, oats, barley, red clover and an oats/ the elements of their farm fit together will be hairy vetch mix were suppressed as needed with the people who will really bring cover crops into fluaz ifop and metribuzin (341). the prominence they deserve in sustainable Cover crops often suppress weeds early, then farming. prevent erosion or supply fertility later in the

MANAGING PESTS WITH COVER CROPS 33 CROP ROTATION WITH COVER CROPS

Readers’ note: > indicates progression to anoth- • Cover crops can be used for feed. Consider er crop; / indicates a mixture of crops growing harvesting or grazing for forage or alternative at the same time. livestock such as sheep and goats.

ne of the biggest challenges of cover The ideas in this book will help you see cover cropping is to fit cover crops into your crop opportunities, no matter what your system. Ocurrent rotations, or to develop new rota- For more in-depth scientific analysis of cover tions that take full advantage of their benefits. This crops in diverse cropping systems, see several section will explore some of the systems used comprehensive reviews listed in Appendix F (77, successfully by farmers in different regions of the 106, 362, 390). U.S. One might be easily adapted to fit your existing crops, equipment and management. Other COVER CROPS FOR CORN BELT examples may point out ways that you can modi- GRAIN AND OILSEED PRODUCTION fy your rotation to make the addition of cover crops more profitable and practical. In addition to providing winter cover and build - Whether you add cover crops to your existing ing soil structure, nitrogen (N) management will rota tions or totally revamp your farming system, probably be a major factor in your cover crop you should devote as much planning and atten- decisions for the corn>soybean rotation. A fall- tion to your cover crops as you do to your cash planted grass or small grain will scavenge leftover crops. Failure to do so can lead to failure of the N from the previous corn or soybean crop. cover crop and cause problems in other parts of Legumes are much less efficient at scavenging N, your system. Also remember that there is likely but will add N to the system for the following no single cover crop that is right for your farm. crop. Legume/grass mixtures are quite good at Before you start: both. • Review Benefits of Cover Crops (p. 7) and Selecting the Best Cover Crops for Your Farm Corn>Soybean Systems (p. 9). Keep in mind that corn is a heavy N feed er, soy- • Decide which benefits are most important to beans benefit little, if at all, from cover crop N and you. that you have a shorter time for spring cover crop • Read the examples below, then consider how growth before corn than before soybeans. these cover crop rotations might be adapted to your particular conditions. ▼ Precaution. If you use herbicides, be sure to • Talk to your neighbors and the other “experts” check labels for plant-back or rotation intervals to in your area, including the contact people list - ensure that your cover crop isn’t adversely affected. ed in Regional Experts (p. 202). • Start small on an easily accessible plot that Cover crop features: rye provides winter you will see often. cover, scavenges N after corn, becomes a long-last- • Be an opportunist—and an optimist. If your ing (6 to 12 week) residue to hold moisture and cropping plans for a field are disrupted by suppress weeds for your soybeans; hairy vetch weather or other conditions outside of your provides spring ground cover, abundant N and a control, this may be the ideal window for moderate-term (4 to 8 week) mulch for a no-till establishing a cover crop. corn crop; field peas are similar to vetch, but • Consider using an early-maturing cash crop to residue breaks down faster; red clover is also allow for timely planting of the cover crop. similar, but pro duces slightly less N and has less

34 MANAGING COVER CROPS PROFITABLY vigorous spring regrowth; berseem clover Harvesting sweet corn, seed corn or silage corn grows quickly to pro vide several cuttings for high- opens a window for timely cover crop planting. N green manure. Harvest or graze the small grain or legume / small Here are some options to consider adapting to grain mixture in spring if needed for feed. See indi- your system: vidual cover crop chapters for management details. In Pennsylvania, Ed Quigley seeds rye or spring Corn>Rye>Soybeans>Hairy Vetch. oats after corn silage harvest. The oats can be cut In Zone 7 and warmer, you can grow a cover crop for silage in fall if planted by early Sept ember. Rye every year between your corn and full-season can be made into rylage or sprayed before no-till corn beans. Also, you can use wheat or another small the following spring. grain to replace the cover crop before beans, in a Worried about Growers are three-crop, two-year rotation (corn>wheat>dou- planting your corn looking to add blecrop beans). In all cases, another legume or a a bit late because grass/legume mixture can be used instead of a sin - you’re waiting for a small grain to gle species cover crop. Where it is adapted, you your cover crop to can use crimson clover or a crimson/grass mix - mature? Research in their corn>soybean ture instead of vetch. Maryland, Illinois and In cooler areas, plant rye as soon as possible else where suggests rotation. after corn harvest. If you need more time in the that no-tilling corn fall, try overseeding in rowed beans at drydown towards the end of “yellow leaf” stage in early fall, or in early summer the usual window when using a legume cover at the last cultivation of corn. Seeding options crop has its rewards. The delay can result in include aerial application where the service is greater yields than earlier planting, due to greater economical, using a specialty high-body tractor moisture conservation and more N pro duced by with narrow tires, or attaching a broadcast seeder, the cover crop, or due to the timing of summer air seeder or seed boxes to a cultivator. drought (82, 84, 300). In Pennsylvania, however, delayed planting sometimes reduced corn yields ▼ Precaution. Broadcast seeding of cover crops following rye (118). into standing crops is less dependable than other Check your state variety trial data for a shorter seeding methods. Success will depend on many season corn hybrid that yields nearly as well as factors, including adequate rainfall amount and slightly longer season corn. The cover crop bene- distribution after seeding. fit should over come many yield differences. Worried about soil moisture? There’s no Kill the rye once it is about knee-high, or let it question that growing cover crops may consume go a bit longer, killing it a couple of weeks before soil moisture needed by the next crop. In humid planting beans. Killing the rye with herbicides regions, this is a problem only in an unusually dry and no-tilling beans in narrow rows allows more spring. Time permitting, allow 2 to 3 weeks after time for cover crop growth, since you don’t have killing the cover crop to alleviate this problem. to work the ground. If soil moisture is low, con- While spring rainfall may compensate for the sider killing the rye earlier. Follow the beans with moisture demand of most cover crops by normal hairy vetch or a vetch/small grain mixture. planting dates, cover crops can quickly dry out a Legumes must be seeded at least 6 weeks field. Later in the season, killed cover crop before hard frost to ensure winter survival. Seed residues in conservation tillage systems can con- by drilling after soybean harvest, or by over - serve moisture and increase yields. seeding before leaf drop. Allow the vetch (or In dryland areas of the Southern Great Plains, mixture) to grow as long as possible in spring for lack of water limits cover crop use. (See Dryland maximum N fixation. Cereal Cropping Systems, p. 42).

CROP ROTATION WITH COVER CROPS 35 In any system where you are using accumulat- before corn the next spring. If possible, choose a ed soil moisture to grow your cash crop, you need differ ent cover crop following the corn this time to be extra careful. However, as noted in this sec- to avoid potential pest and disease problems with tion and elsewhere in the book, farmers and the crimson clover. researchers are finding that water-thrifty cover crops may be able to replace even a fallow year ▼ Precaution. In selecting a cover crop to inter- without adversely affecting the cash crop. seed, do not jeopardize your cash crop if soil moisture is usually limiting during the rest of the Corn>Rye>Soybeans>Small Grain>Hairy Vetch. corn season! Banding cover crop seed in row This rotation is similar to the corn>rye>soybeans middles by using insecticide boxes or other rotation described above, except you add a year of devices can reduce cover crop competition with small grains following the beans. In crop rotation the cash crop. research from different areas, many benefits accrue as the rotation becomes longer. This is 3 Year: Corn>Soybean>Wheat/Red Clover. because weed, disease and insect pest problems This well-tested Wisconsin sequence provides N generally decrease with an increase in years for corn as well as weed suppression and natural between repeat plantings of the same crop. control of disease and insect pests. It was more Residue from small grains provides good organ - profitable in recent years as the cost of synthetic ic matter for soil building, and in the case of win - N increased. Corn benefits from legume-fixed N, ter grains, the plants help to prevent erosion over and from the improved cation exchange capacity winter after soybeans loosen up the soil. in the soil that comes with increasing organic The length of the growing season will deter - matter levels. mine how you fit in cover crops after full-season Growers in the upper Midwest can add a small soybeans in the rotation. Consider using a short- grain to their corn>bean rotation. The small grain, season bean if needed in order to achieve timely seeded after soybeans, can be used as a cover planting after soybean harvest. Calculate whether crop, or it can be grown to maturity for grain. cover crop benefits will compensate for a possi - When growing wheat or oats for grain, frost-seed ble yield loss on the shorter season beans. If there red clover or sweet-clover in March, harvest the is not enough time to seed a legume after har vest, grain, then let the clover grow until it goes dor- use a small grain rather than no cover crop at all. mant in late fall. Follow with corn the next spring. The small grain scavenges leftover N following Some sec ondary tillage can be done in the fall, if beans. Legume cover crops reduce fertilizer N conditions allow. One option is to attach sweeps needed by corn, a heavy N feeder. If you cannot to your chis el plow and run them about 2 inches seed the legume at least six weeks before a hard deep, cut ting the clover crowns. frost, consider overseeding before leaf drop or at Alternatively, grow the small grain to maturity, last cultivation. harvest, then immediately plant a legume cover crop such as hairy vetch or berseem clover in July ▼ Precaution. Because hairy vetch is hard seed- or August. Soil moisture is critical for quick germi- ed, it will volunteer in subsequent small grain nation and good growth before frost. For much of crops. the northern U.S., there is not time to plant a legume after soybean harvest, unless it can be An alternate rotation for the lower mid-South is seeded aerially or at the last cultivation. If growing corn>crimson clover (allowed to go to seed) > spring grains, seed red clover or sweet-clover soybeans > crimson clover (reseeded) > corn. directly with the small grain. Allow the crimson clover to go to seed before An Iowa study compared no-till and conven- planting beans. The clover germinates in late tional tillage corn>soybean>wheat/clover rota- sum mer under the beans. Kill the cover crop tion with annual applications of composted

36 MANAGING COVER CROPS PROFITABLY swine manure. Berseem clover or red clover was Where moisture is sufficient, many vegetable frostseeded into wheat in March. Corn and soy- crops can be overseeded with a cover crop, bean yields were lower in no-till plots the first which will then be established and growing after year, while wheat yield was not affected by tillage. vegetable harvest. Select cover crops that tolerate With yearly application of composted swine shade and harvest traffic, especially where there manure, however, yield of both corn and soybean will be multi ple pickings. were the same for both systems beginning in year Cover crop features: Oats add lots of bio- two of the 4-year study (385). mass, are a good nurse crop for spring-seeded Adding a small grain to the corn>soybean rota- legumes, and winterkill, tion helps control white mold on soybeans, since doing away with the Residue from two years out of beans are needed to reduce need for spring killing small grains pathogen pop ulations. Using a grain/legume mix and tilling. Sor gh um- will scavenge available N from the bean crop, sudangrass hybrid provides organic hold soil over winter and begin fixing N for the produces deep roots and corn. Clovers or vetch can be harvested for seed, tall, leafy stalks that die matter for soil and red or yellow clover can be left for the second with the first frost. building. . . to year as a green manure crop. Yellow sweetclover is Using a spring seeding of oats and berseem a deep rooting legume prevent erosion clover has proved effective on Iowa farms that that provides cuttings of also have livestock. The mix tends to favor oat green manure in its sec- over winter. grain production in dry years and berseem pro - ond year. White clover duction in wetter years. Either way the mixture is a persistent perennial provides biomass to increase organic matter and and good N source. Brassicas and mustards build soil. You can clip the berseem several times can play a role in pest suppression and nutrient before flowering for green manure. management. Mixtures of hairy vetch and cer eal rye are increasing used in vegetable ▼ Precaution. Planting hairy vetch with small systems to scavenge nutrients and add N to the grains may make it difficult to harvest a clean grain system. crop. Instead, seed vetch after small grain harvest. In Zone 5 and cooler, plant rye, oats or a sum- Be sure to watch for volunteer vetch in subsequent mer annual (in August) after snap bean or sweet small grain crops. It is easily controlled with herbi- corn harvest for organic matter production and cides but will result in significant penalties if found erosion control, especially on sandy soils. Spray or in wheat grain at the elevator. incorporate the following spring, or leave unkilled strips for continued control of wind erosion. COVER CROPS FOR VEGETABLE If you have the option of a full year of cover PRODUCTION crops in the East or Midwest, plant hairy vetch in the spring, allow to grow all year, and it will die Vegetable systems have many windows for cover back in the fall. Come back with no-till sweet or crops. Periods of one to two months between har- field corn or another N-demanding crop the vest of early planted spring crops and planting of following spring. Or, hairy vetch planted after fall crops can be filled using fast-growing warm- about August 1 will overwinter in most zones season cover crops such as buckwheat, cowpeas, with adequate snow coverage. Allow it to grow sorghum-sudangrass hybrid, or another crop until early flower the following spring to achieve adapted to your condi tions. As with other crop- full N value. Kill for use as an organic mulch for ping systems, plant a winter annual cover crop on no-till transplants or incorporate and plant a sum- fields that otherwise would lie fallow. mer crop.

CROP ROTATION WITH COVER CROPS 37 Full-Year Covers Tackle Tough Weeds TROUT RUN, Pa.—Growing cover crops for a plant bugs were not an issue on their farm, but full year between cash crops, combined with in the 90’s they became a major problem in let- intensive tillage, helps Eric and Anne Nordell tuce. The problem—and the solution!—was in control virtually every type of weed nature their management of yellow sweetclover. throws at their vegetable farm—even quack- In their original rotation, sweetclover was grass. They are also manipulating the system to overseeded into early cash crops such as let- address insects. tuce. After overwintering, the sweetclover was The couple experimented with many different mowed several times the following year before cover crops on their north-central Pennsylvania plowing it under and planting late vegetable farm while adapting a system to battle quackgrass. crops. When the tarnished plant bugs began Originally modeled on practices developed on a moving in—possibly attracted by the flowering commercial herb farm in the Pacific Northwest, the sweetclover—the Nordells realized that mow- Nordells continue to make modifications to fit their ing the sweetclover caused the plant bugs to ever-changing conditions. move to the adjacent lettuce fields. It was time In the fallow year between cash crops, the to change their system. Nordells grow winter cover crops to smother Fully committed to the use of cover crops, weeds and improve soil. Combined with sum- they first tried to delay mowing of the sweet- mer tillage, the cover crops keep annual weeds clover until after lettuce harvest. Eventually, from setting seed. Cognizant of the benefits of they decided to revamp their clover manage- reduced tillage, they continue to modify their ment completely. They now plant sweetclover tillage practices—reducing tillage intensity in June of the second or fallow year of the rota- whenever possible. tion. This still gives the sweetclover plenty of Regular use of cover crops in the year before time to produce a soil-building root system vegetables also improves soil quality and mois- before late vegetables. It flowers later, so they ture retention while reducing erosion. “Vegetable are no longer mowing it and forcing tarnished crops return very little to the soil as far as a root plant bugs into lettuce fields. system,” says Eric, a frequent speaker on the con- Yellow blossom sweetclover—one of the ference circuit. “You cut a head of lettuce and best cover crop choices for warm-season nitro- have nothing left behind. Growing vegetables, gen production—puts down a deep taproot we’re always trying to rebuild the soil.” before winter if seeded in June or July, observes Continual modification to their system is the Eric. “That root system loosens the soil, fixes name of the game. When they set up their orig- nitrogen, and may even bring up minerals from inal 4-year rotation in the early 80’s, tarnished the subsoil with its long tap root.”

You can sow annual ryegrass right after har - 3 Year: Winter Wheat/Legume Interseed> vesting an early-spring vegetable crop, allow it to Legume>Potatoes. This eastern Idaho rotation grow for a month or two, then kill, incorporate conditions soil, helps fight soil disease and pro- and plant a fall vegetable. vides N. Sufficient N for standard potatoes Some farmers maximize the complementary depends on rainfall being average or lower to pre- weed-suppressing effects of various cover crop vent leaching that would put the soil N below the species by orchestrating peak growth periods, shallow-rooted cash crop. rooting depth and shape, topgrowth differences 2 Year Options: For vegetable systems in the and species mixes. See Full-Year Covers Tackle Pacific Northwest and elsewhere, plant a winter Tough Weeds (above). wheat cover crop followed by sweet corn or

38 MANAGING COVER CROPS PROFITABLY Originally part of their weed management seeding, the Nordells’ rye/vetch mixture pro- program, Eric points out that the clover alone duces “a tremendous root system” and much of would not suppress weeds. It works on their its biomass in fall. farm because of their successful management The Nordells plow the rye/vetch mix after it efforts over a decade to suppress overall weed greens up in late March to early April, working pressure using intensive tillage, crop rotation shallowly so as not to turn up as many weed and varied cover crops. The same concept seeds. They understand that such early kill sac- applies to the tarnished plant bug. Never satis- rifices some biomass and N for earlier planting fied with a single strategy rather than a whole- of their cash crop—tomatoes, peppers, sum- system approach, the Nordells also began mer broccoli or leeks—around the end of May. interseeding a single row of buckwheat into Thanks to their weed-suppressing cover successive planting of short term cash crops crops, the Nordells typically spend less than 10 like lettuce, spinach and peas. hours a season hand-weeding their three acres The idea was to create a full-season insec- of cash crops, and never need to hire outside tiary in the market garden, moderating the weeding help. “Don’t overlook the cover boom and bust cycle of good and bad insects. crops’ role in improving soil tilth and making They also hoped that the buckwheat would cultivation easier,” adds Eric. Before cover crop- provide an alternate host for the plant bugs. ping, he noticed that their silty soils deteriorat- The strategy seems to be working. Data col- ed whenever they grew two cash crops in lected as part of a research project with the a row. “When the soil structure declines, it Northeast Organic Network (NEON) found doesn’t hold moisture and we get a buildup of very few tarnished plant bugs in their lettuce annual weeds,” he notes. but lots in the buckwheat insectiary. The Nordells can afford to keep half their The two pronged cover crop approach land in cover crops because their tax bills and using buckwheat and a different management land value are not as high as market gardeners regime for sweetclover seems to be doing the in a more urban setting. “We take some land trick. The next step, currently being evaluated, out of production, but in our situation, we have is to mix Italian ryegrass with the sweetclover the land,” Eric says. “If we had to hire people to increase root mass and sod development for weed control, it would be more costly.” between June planting and frost. To order a video describing this system ($10 Rye and vetch are a popular combination to postpaid) or a booklet of articles from the manage nitrogen. The rye takes up excess N Small Farmers’ Journal ($12 postpaid), write to from the soil, preventing leaching. The vetch Eric and Anne Nordell, Beech Grove Farm, fixes additional nitrogen which it releases after 3410 Route 184, Trout Run, PA 17771. it’s killed the following spring. With the August Updated in 2007 by Andy Clark onions. Another 2-yr. option is green peas > sum- Northeast’s early spring vegetable crops often mer sorghum-sudangrass cover crop > potatoes leave little residue after their early summer har - (in year 2). Or, seed mustard green manure after vest. Sequential buckwheat plantings suppress winter or spring wheat. Come back with potatoes weeds, loosen topsoil and attract beneficial the following year. For maximum biofumigation insects. Buckwheat is easy to kill by mowing in effect, incorporate the mustard in the fall (see preparation for fall transplants. With light tillage to Brassicas and Mustards, pp. 81). incorporate the relatively small amount of fast- 1 Year: Lettuce>Buckwheat>Buckwheat> degrad ing buckwheat residue, you can then sow a Broccoli>White Clover/Annual Ryegrass.The winter grass/legume cover mix to hold soil

CROP ROTATION WITH COVER CROPS 39 throughout the fall and over winter. Planted at ANNUAL and PERENNIAL MEDIC least 40 days before frost, the white clover should cultivars can fix N on low moisture overwinter and provide green manure or a living and can reduce erosion in dryland mulch the next year. areas compared with bare fallow California Vegetable Crop Systems between crop seasons. Innovative work in California includes rotating cover crops as well as cash crops, adding diversi - ty to the system. This was done in response to an COVER increase in Alternaria blight in LANA vetch if CROPS FOR planted year after year. COTTON 4 Year: LANA Vetch>Cor n>Oats/Vetch> PRODUCTION Dry Beans>Common Vetch>Tomatoes>S-S Hybrid/ Cowpea>Safflower. The N needs of In what would the cash crops of sweet corn, dry beans, safflower otherwise be con- and can ning tomatoes determine, in part, which tinuous cotton pro- covers to grow. Corn, with the highest N demand, duction, any winter is preceded by LANA vetch, which produces more annual cover crop added N than other covers. Before tomatoes, common to the system can add vetch works best. A mixture of purple vetch rotation benefits, and oats is grown before dry beans, and a mix help maintain soil of sorghum-sudangrass and cowpeas precedes productivity, and safflower. provide the many In order to get maximum biomass and N pro- other benefits of cover crops highlighted duction by April 1, LANA vetch is best planted early throughout this book. enough (6 to 8 weeks before frost) to have good Hairy vetch, crimson clover, or mixtures with growth before “winter.”Disked in early April, LANA rye or another small grain can reduce erosion, add pro vides all but about 40 lb. N/A to the sweet N and organic matter to the system. Drill after corn crop. Common vetch, seeded after the corn, shredding stalks in the fall and kill by spraying or can fix most of the N required by the subsequent mowing prior to no-till seeding of cotton in May. tomato crop, with about 30 to 40 lb.N/A added as Or, aerially seed just before application of defoliant. starter. The dropping leaves mulch the cover crop seed, A mixture of sorghum-sudangrass and cowpeas aiding germination. Rye works better than wheat. is planted following tomato harvest. The mixture Yields are usually equal to, or greater than yields in responds to residual N levels with N-scavenging conventional tillage systems with winter fallow. by the grass component to prevent winter leach- Balansa clover, a promising cover crop for the ing. The cowpeas fix enough N for early growth of South, reseeds well in no-till cotton systems (see the subsequent safflower cash crop, which has Up-and-Coming Cover Crops, p. 191). relatively low initial N demands. The cover crop 1 Year: Rye/Legume>Cotton. Plant the breaks down fast enough to supply safflower’s rye/legume mix in early October, or early enough later-season N demand. to allow the legume to establish well before cooler winter temperatures. Kill by late April, and if ▼ Precaution. If you are not using any herbi - soil moisture permits, no-till plant cotton within cides, vetch could become a problem in the three to five days using tined-wheel row cleaner California system. Earlier kill sacrifices N, but does attach ments to clear residue. Band-spray normal not allow for the production of hard seed that pre emergent herbicides over the cleaned and stays viable for several seasons. planted row area. Cotton will need additional

40 MANAGING COVER CROPS PROFITABLY Start Where You Are In many instances, you can begin using cover spring cover crop killing, try a non-hardy cul- crops without substantially altering your cash tivar of berseem clover or annual alfalfa. crop mix or planting times or buying new If you have livestock, a forage/hay market machinery. Later, you might want to change option or want more soil benefits, choose a your rotation or other practices to take better longer-lived legume cover. advantage of cover crop benefits. Corn>Soybean>Small Grain/Legume> We’ll use a basic Corn Belt situation as a Legume Hay, Pasture or Green Manure. model. From a corn>soybean rotation, you can Yellow sweetclover or red clover are popular expand to: forage choices. An oats/berseem interseeding Corn>Cover>Soybean>Cover. Most popu- provides a forage option the first year. lar choices are rye or rye/vetch mixture follow- Harvesting the cover crop or terminating it ing corn; vetch or rye/vetch mixture following early in its second season opens up new beans. Broadcast or drill covers immediately options for cash crops or a second cover crop. after harvest. Hairy vetch needs at least 15 days Late-season tomatoes, peppers, vine crops or before frost in 60° F soil. Rye will germinate as sweet corn all thrive in the warm, enriched soil long as soil is just above freezing. Drill for quick- following a green manure. Two heat-loving cover germination. Consider overseeding at leaf-yel- ers that could be planted after killing a cool-sea- lowing if your post-harvest planting window is son legume green manure are buckwheat (used too short. to smother weeds, attract beneficial insects or If you want to make certain the legume is for grain harvest) and sorghum-sudangrass well established for maximum spring N and bio- hybrid (for quick plow-down biomass or to mass production, consider adding a small grain fracture compacted subsoil). to your rotation. These crops would work most places in the Corn>Soybean>Small Grain/Cover. Small Corn Belt. To get started in your area, check Top grains could be oats, wheat or barley. Cover Regional Cover Crop Species (p. 66) to fill various could be vetch, field peas or red clover. If you roles, or Cultural Traits and Planting (p. 69) to want the legume to winterkill to eliminate find which cover crops fit best in your system. weed control toward layby using flaming, cultiva- Strip planting into reseeding legumes works for tion or directed herbicides. Crimson clover, hairy many crops in the South, including cotton, corn, vetch, Cahaba vetch and Austrian winter peas are sweet potatoes, peanuts, peppers, cucumbers, effective legumes in this system. cabbage and snap beans. Tillage or herbicides Multiyear: Reseeding Legume>No-Till are used to create strips 12 to 30 inches wide. Cotton> Legume>No-Till Cotton. Subterranean Wider killed strips reduce moisture competition clover, Southern spotted burclover, balansa clover by the cover crop before it dies back naturally, but and some crimson clover cultivars set seed quick- also reduce the amount of seed set, biomass and ly enough in some areas to become perpet ually N produced. Wider strips also decrease the reseeding when cotton planting dates are late mulching effect from the cover crop residue. enough in spring. Germination of hard seed in late The remaining strips of living cover crop act as summer provides soil erosion protection over in-field insectary areas to increase overall insect winter, N for the following crop and an organic populations, resulting in more beneficial insects mulch at planting. to control pest insects.

CROP ROTATION WITH COVER CROPS 41 ▼ Precautions providing green manure and erosion control; • Watch for moisture depletion if spring is field peas and lentils (grain legumes) are shal- unusually dry. low-rooted yet produce crops and additional N in • Be sure to plant cotton by soil temperature years of good rainfall. (65° F is required), because cover crops may An excellent resource describing these rota - keep soil cool in the spring. Don’t plant too tions in detail is Cereal-Legume Cropping early! Systems: Nine Farm Case Studies in the Dryland • A delay of two to three weeks between cover Northern Plains, Canadian Prairies and crop kill and cotton planting reduces these Intermountain Northwest (258). problems, and reduces the chance of stand 7 to 13 Years: Flax>Winter Wheat>Spring losses due to insects (cutworm), diseases or Barley>Buckwheat>Spring Wheat>Winter allelopathic chemicals. Wheat>Alfalfa (up to 6 years) >Fallow • Additional mid-summer weed protection is needed during the hot-season “down time” for System sequences are: the reseeding legumes. • Flax or other spring crops (buckwheat, wheat, • Reseeding depends on adequate hard seed pro- barley) are followed by fall-seeded wheat duction by the clovers. Dry summer weather (sometimes rye), harvested in July, leaving favors hard seed production while wet sum- stubble over the winter; mers reduce the percentage of hard seed. • Spring-seeded barley or oats, harvested in August, leaving stubble over the winter; DRYLAND CEREAL-LEGUME • Buckwheat, seeded in June and harvested in CROPPING SYSTEMS October, helps to control weeds; • A spring small grain, which outcompetes any Soil moisture availability and use by cover crops volunteer buckwheat (alternately, fall-seeded are the dominant concerns in dryland production wheat, or fall-seeded sweetclover for seed or systems. Yet more and more innovators are finding hay). that carefully managed and selected cover crops in their rotations result in increased soil moisture The rotation closes with up to 6 years of alfalfa, availability to their cash crops. They are finding plowdown of sweetclover seeded with the previ - ways to incorporate cover crops into flexible rota- ous year’s wheat or an annual legume green tions that can be modified to capitalize on soil manure such as Austrian winter peas or berseem moisture when available while preventing clover. adverse effects on cash crops. This deli cate bal- There are many points during this rotation ance between water use by the cover crop and where a different cash crop or cover crop can water conservation—particularly in conservation be substitut ed, particularly in response to market tillage systems—will dictate, in part, how cover conditions. Furthermore, with cattle on the crops work in your rotation. See also Managing ranch, many of the crops can be grazed or cut Cover Crops in Conservation Tillage Systems for hay. (p. 44). Moving into areas with more than 12 inches of Perennial legumes provide numerous benefits rain a year opens additional windows for incor - to grain cropping systems in the Northern Plains, porating cover crops into dryland systems. including increased grain yield, nutrient scaveng- 9 Year: Winter Wheat>Spring Wheat> ing, carbon sequestration, breaking weed and Spring Grain/Legume Interseed>Legume insects cycles and for use as feed (129). Green Manure/Fallow>Winter Wheat> Cover crop features: perennial medics per sist Spring Wheat>Grain/Legume Interseed> due to hard seed (of concern in some systems), Legume> Legume. In this rotation, one year of

42 MANAGING COVER CROPS PROFITABLY winter wheat and two years of spring-seeded While moisture levels fluctuate critically from crops fol low a two or three-year legume break. year to year in dryland systems, N levels tend to be Each legume sequence ends with an early sum- more stable than in the hot, humid South, and mer incorporation of the legume to save moisture adding crop residue builds up soil organic matter fol lowed by minimal surface tillage to control more easily. Careful management of low-water use weeds. Deep-rooted winter wheat follows sweet- cover crops can minimize soil water loss while clover, which can leave surface soil layers fairly adding organic mat ter and N. Consequently, dry- dry. Spring-seeded grains prevent weeds that land rotations can have a significant impact on show up with successive winter grain cycles and soils and the field environment when used over a have shallower roots that allow soil moisture to number of years. build up deeper in the profile. These improved soils have higher organic mat- In the second spring-grain year, using a low-N ter, a crumbly structure, and good water retention demanding crop such as kamut wheat reduces and infiltration. They also resist compaction and the risk of N-deficiency. Sweetclover seeded with effectively cycle nutrients from residue to subse- the kamut provides regrowth the next spring that quent crops. helps to take up enough soil water to prevent Remember, the benefits of cover crops accrue saline seep. Black medic, INDIANHEAD lentils and over several years. You will see improvements in field peas are water-efficient substitutes for the crop yield, pest management and soil tilth if you deep-rooted—and water hungry—alfalfa and commit to cover crop use whenever and wherev - sweetclover. These peas and lentils are spring- er possible in your rotations. sown, providing back-up N production if the for - age legumes fail to establish.

CROP ROTATION WITH COVER CROPS 43 MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS by Kipling Balkcom, Harry Schomberg, Wayne Reeves and Andy Clark with Louis Baumhardt, Hal Collins, Jorge Delgado, Sjoerd Duiker, Tom Kaspar and Jeffrey Mitchell

INTRODUCTION This accumulation of surface organic matter results in: Conservation tillage is defined as a system that • increased aggregate stability, which helps to leaves enough crop residue on the soil surface increase soil water infiltration and resist erosion after planting to provide 30% soil cover, the • improved nutrient cycling and water quality, amount needed to reduce erosion below toler- due to keeping nutrients in the field ance levels (SSSA). Today, however, most conser- • increased biological activity, which improves vation tillage practitioners aim for greater soil nutrient cycling and can influence diseases cover because of additional benefits of crop and pests residue. Cover crops are critical to producing this residue and have the potential to maximize con- Additional benefits from conservation tillage sys- servation tillage benefits. tems compared to intensive or conventional Benefits of conservation tillage systems include: tillage systems (89) include: • reduced soil erosion • Reduced labor and time—one or two trips to • decreased labor and energy inputs prepare land and plant compared to three or • increased availability of water for crop production more reduces labor and fuel costs by 50% or • improved soil quality more. • Reduced machinery wear—fewer trips mean Cover crops further benefit conservation tillage fewer repairs. systems by: • Increased wildlife—crop residues provide • producing crop residues that increase soil shelter and food for wildlife, such as game organic matter and help control weeds birds and small animals, which can result in • improving soil structure and increasing infiltration additional farm revenue. • protecting the soil surface and dissipating rain- • Improved air quality—by reducing wind drop energy erosion (amount of dust in the air), fossil fuel • reducing the velocity of water moving over emissions from tractors (fewer trips) and the soil surface release of carbon dioxide into the atmosphere • anchoring soil and adding carbon deep in the (tillage stimulates the release of carbon from soil profile (via roots) organic matter).

Conservation tillage has been adopted on more In an Iowa study comparing no-till and conven- and more acres since the 1970’s thanks to tional tillage in a corn>soybean>wheat/clover improvements in equipment, herbicides and rotation, corn and soybean yields were lower in other technologies. Several long-term, incremen- no-till plots the first year. With yearly application tal benefits of conservation tillage have emerged. of composted swine manure, however, yield of The most important benefits have been attributed both corn and soybean were the same for both to the accumulation of organic matter at the soil systems beginning in year two of the study. Wheat surface. yields were not affected by tillage, but increased with compost application (385).

44 MANAGING COVER CROPS PROFITABLY Cover crop contributions to In Kentucky, on a Maury silt loam soil with a 5% conservation tillage systems slope, soil loss was 8 tons/A for conventionally Biomass. Conservation tillage systems depend tilled corn with the corn residue and cover crop on having crop residues on the soil surface for turned under in the spring. In contrast, for no- most of the year. Cover crops help provide the tillage corn with 3 tons/A of corn residue remain- additional biomass needed to meet this year- ing on the soil surface, round requirement. A typical high residue cover soil loss was 1 ton/A Tillage breaks without a cover crop and crop should contain at least 4000 lb. biomass/A. down organic In low-fertility soils, you can increase biomass 0.9 tons/A with a winter production of grass cover crops with the addition cover crop (91, 151). matter much of a small amount of N fertilizer. Cover crops In Missouri, on a grown in soils with higher levels of organic mat- Mexico series silt loam faster than no-till. ter, or following a legume summer crop like soy- soil with a claypan, bean, may not need additional N fertilizer. inclusion of a rye or Remember, minimal cover crop residue or bio- wheat cover crop reduced soil loss in no-tillage mass translates into minimal benefits. silage corn from 9.8 to 0.4 tons/A/year (437). Soil improvement. Cover crop biomass is a Rotation effects. Crop rotation provides source of organic matter that stimulates soil bio- numerous benefits to any cropping system. It is logical activity. Soil organic matter and cover crop critical to reducing the incidence of diseases and residues improve soil physical properties, result- pests, and is also credited with improving nutrient ing in: use and reducing weeds. Cover crops increase the • greater water infiltration, due to direct effects complexity and intensity of crop rotations, effec- of the residue coverage or to changes in soil tively increasing crop rotation benefits. Note, structure however, as addressed throughout this book, that • greater soil aggregation or tilth, resulting in cover crops can adversely affect other crops in better nutrient and moisture management the rotation. • less surface sealing, because residue intercepts rain drops, reducing the dispersal of clay parti- Cover crop management in cles during a rainfall or irrigation event conservation tillage systems • greater soil porosity, due to the macropores Nutrient management. Nitrogen and phospho- that are formed as roots die and decompose rus are the two macronutrients most likely to be lost from cropping systems. Cover crops help Improvements in soil physical properties depend reduce losses of these nutrients by: on soil type, crops grown and residue manage- • increasing infiltration—thus reducing surface ment system, as well as temperature and rainfall. runoff and erosion Regardless of soil type, however, tillage will very • taking up nutrients—or acting as a ‘catch crop’ quickly negate cover crop benefits associated • using water for cover crop growth during with increased soil organic matter. Simply put, peak leaching season (late fall through early tillage breaks down organic matter much faster spring)—reducing the amount of water avail- than no-till. able to leach nutrients Improvements in soil physical properties due to cover crops have been documented widely in Grasses and brassicas are better than legumes at conservation tillage systems (25, 52, 106, 114, 115, reducing N leaching (106, 234, 265). Cereal rye is 119, 238, 318, 419). very effective at reducing N leaching because it is Erosion control. Cover crops and conserva- cold tolerant, has rapid growth, and produces a tion tillage combine to reduce soil erosion and large quantity of biomass (111). Winter annual wind erosion (26, 115, 119, 223, 267). weeds do not effectively reduce N losses.

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 45 Cover crops may reduce the efficiency of N fer- Values exceeding 30 parts carbon to one part tilizer in no-till systems, depending on the method nitrogen (C:N ratio of 30:1) are generally expect- of application. Surface applications of urea-con- ed to immobilize N during the early stages of the taining fertilizers to soils with large amounts of decomposition process. For more information cover crop residues can result in large losses of about C:N ratios and cover crop nutrient dynam- ammonia N. When applied to the soil surface, urea ics, see Building Soil Fertility and Tilth with and urea-ammonium nitrate (UAN) solutions Cover Crops (pp. 16). volatilize more than ammonium nitrate and sub- The C:N ratio of small grain residues is mostly sequently lose more N to the atmosphere. dependent on time of termination. Early termina- Injecting urea-containing fertilizers into the soil tion of grass cover crops results in a narrower C:N eliminates volatilization losses. Banding urea-con- ratio, typical of young plant tissue. If killed too taining fertilizers also reduces volatilization losses early, this narrower C:N ratio results in rapid because banding minimizes fertilizer and residue decomposition of a smaller amount of residue, contact, while increasing fertilizer and soil contact. reducing ground coverage. Nitrogen dynamics with nonlegume cover Because of the need for residue in conservation crops. Differences between nonlegumes and tillage systems, small grain cover crops are often legume cover crops are mostly related to nitrogen allowed to grow as long as possible. Termination management. Legumes fix N while nonlegumes date depends on crop rotation and climate. When can only use N already in the soil. Legume small grain cover crops are killed at flowering, the residues usually contain more total N that is more C:N ratio is usually greater than 30:1. readily available to subsequent crops. In Pennsylvania, delaying rye termination date The addition of fresh crop residues stimulates from early to late boot stage increased average growth of soil microbes and increases microbial above-ground dry matter accumulation from 1200 demand for nutrients, particularly N. Micro - to 3700 lb./A with no negative effect on corn organisms use C, N and other nutrients as a food yield (118). source in order to break down the residues. If the In Alabama, rye, black oat and wheat cover amount of N in the residues is too low, the crops were terminated at different growth stages microorganisms use soil N instead, reducing N with a roller or roller-herbicide combinations. availability to the cash crop. This is called N Biomass production was about 2.0 – 2.6 tons/A at immobilization. If the amount of N in the the flag leaf stage and corresponding C:N ratio residues is greater than microbial demand, N is averaged 25:1, regardless of cover crop species. released and N availability for plant growth is At flowering, biomass averaged 4.2, 3.8, and 3.3 increased, a process called N mineralization. tons/A for black oat, rye and wheat, respectively, Small grain and other grass cover crops usually and the C:N ratio for all covers was 36:1. Killing at result in an initial, if not persistent, immobilization soft dough stage did not increase biomass pro- of N during the cash crop season. The N content duction for any of the covers, but did increase the of small grain cover crop residues varies greatly, C:N ratios, which would increase N immobiliza- but generally ranges from 20 to 50 lb./A for the tion (13). aboveground biomass and 8 to 20 lb./A in the The wide C:N ratio of small grain residues must roots. The N contribution from small grain cover be taken into account for best N management. crops depends on N availability during the cover Nitrogen fertilizer rates for cash crops may need crop growing period, the total amount of biomass to be increased 25 to 30 lb./A following a high produced and the growth stage when the cover is residue cereal cover crop. terminated. In N-limited soils, early-season growth of the The carbon to nitrogen ratio (C:N ratio) of cash crop is usually enhanced if this N is applied cover crop residue is a good indicator of whether as starter fertilizer. Although yield increases from immobilization or mineralization will occur. starter N applications are dependent on rainfall

46 MANAGING COVER CROPS PROFITABLY and crop, they occur frequently enough to justify Due to the initial lag in availability of N from the practice. Starter fertilizer promotes more legume cover crop residues, any additional fertil- rapid canopy development, which reduces weed izer N should be applied to cash crops at planting competition and can offset the negative effects of in conservation-tillage winter annual legume sys- cool, wet soils often experienced with conserva- tems. Splitting N applications to corn grown in tion tillage systems. Ideally, starter fertilizers these systems, as is generally recommended for should be placed near the seeding row in a 2 X 2 conventional-tilled corn grown without legume band, i.e. 2 inches to the side and 2 inches below cover crops, is not necessary (347). the seed. Grass-legume mixtures. Mixtures of grass Legumes add N. Legume cover crops obtain and legume cover crops provide the same bene- nitrogen from the atmosphere through a symbiot- fits to conservation tillage but often mitigate the ic relationship with nitrogen fixing bacteria. The nitrogen immobilization of pure grass cover N content of legume cover crops and the amount crops. The grass component scavenges residual of N available to subsequent crops is affected by: nitrogen effectively, while the legume adds fixed • Legume species and adaptation to soil and nitrogen that is more readily available to the cash climatic conditions crop (86, 343, 344, 345). • residual soil N The C:N ratio of grass-legume mixtures is usu- • planting date ally intermediate to that of pure stands. In several • termination date studies in Maryland, the C:N ratio of mixtures of hairy vetch and rye never exceeded 25:1; the C:N Cover crop management affects the N content of ratio of pure rye ranged from 30:1 to 66:1 across legume cover crops and the contribution of N to several spring kill dates (81, 83, 84, 85, 86). the following cash crop. Early establishment of Water availability. Cover crops use soil water legume cover crops results in greater biomass while they are growing. This can negatively affect production and N production. The nitrogen con- cash crop yields. Once killed, however, cover crop tent of legume cover crops is optimized at the residues may increase water availability by increas- flowering stage. Legumes can contribute from 15 ing infiltration and reducing evaporation losses. to 200 lb. N/A to the subsequent crop, with typi- Short-term soil water depletion at planting may cal values of 50 to 100 lb./A. or may not be offset by soil water conservation In North Carolina, delaying the kill date of crim- later in the growing season. This is dependent on son clover 2 weeks beyond 50% bloom, and hairy rainfall distribution in relation to crop develop- vetch 2 weeks beyond 25% bloom increased the ment. A rainfall event following cover crop termi- biomass of clover by 41% and vetch by 61%. nation enables soil surface water recharge, which Corresponding increases in N content were 23% usually provides adequate soil moisture in humid for clover and 41% for vetch (427). In Maryland, regions to facilitate cash crop planting. Time of hairy vetch fixed about 2 lb. N/acre/day from termination becomes more critical as the proba- April 10 to May 5, resulting in an additional 60 lb. bility of precipitation decreases (423). N/A in aboveground biomass (82, 83, 86). The C:N ratio of mature legume residues varies Cover crops increase water availability by: from 25:l to 9:1 and is typically well below 20:1, • decreasing evaporation due to a mulching the guideline threshold where rapid mineraliza- effect tion of the N in the residue occurs. Residues • increasing infiltration of rainfall by decreasing on the soil surface decompose more slowly runoff velocity than those incorporated in conventional tillage • increasing organic matter, which increases systems. Consequently, in conservation tillage sys- water-holding capacity tems, legume-residue N may not be readily avail- • improving soil structure and consequently able during the early part of the growing season. increasing root interception of soil water

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 47 • protecting the soil surface from raindrop For example, yield reductions due to early-season impact, thus reducing development of a sur- depletion of soil water can be reduced by killing face seal or crust, which can greatly reduce the cover crop 2 to 3 weeks before planting the infiltration cash crop (428, 290, 348). Depending on your situation, you could extend this window to termi- In Alabama, cover crop residue left on the soil sur- nate cover crops in conservation systems from 4 face reduced runoff and increased infiltration by to 6 weeks prior to planting the cash crop. 50 to 800% compared to removing or incorporat- Cover crops can sometimes be used to deplete ing the residues (418, 419). In Georgia, infiltration soil water on poorly drained soils, allowing an ear- rates were 100% greater even after removal of lier planting date for the cash crop, but the prac- crop residues for a Cecil sandy loam when grain tical advantage of this practice is not certain. sorghum was no-till planted into crimson clover Soil temperature. Cover crop residues keep compared to a tilled seedbed without a cover the soil cooler, reduce daily fluctuations of soil crop (52). temperature, and reduce soil temperature maxi- In Maryland, pure and mixed stands of hairy mums and minimums. The cooler soil tempera- vetch and rye did not deplete soil water or tures, which benefit the cash crop throughout the adversely affect corn yield. Rather, the additional summer, can delay spring planting compared to a residue from cover crops killed in early May con- system without a cover crop. served soil moisture and contributed to greater Spring soil temperature is particularly impor- corn yield (84, 85). tant in cover crop/conservation tillage systems. In Kentucky, surface evaporation from May to Where possible, plant your cash crop according September was five times less under no-till to soil temperature rather than the calendar. (which leaves a surface mulch) than with con- Follow local recommendations about the appro- ventional tillage. Because less water was lost to priate soil temperature for your cash crop. As evaporation, more water was available for the noted below, the use of row cleaners will allow crop (91). faster soil warmup. Cover crop use in dryland systems is often The harmful effects of planting when the soil limited by moisture availability. A literature temperature is too low were demonstrated in review of dryland cover crop studies on the Great Colorado for conservation tillage with continuous Plains concluded that use of cover crops on dry- corn (but not cover crops). Low soil temperatures land cropping systems of the Great Plains contributed to reduced corn yields over 5 years reduced yields of subsequent crops. However, in (171, 172). semi-arid Texas, 5 tons/A of wheat straw increased Insects and diseases. Conservation tillage sys- available soil water by 73% and more than dou- tems alter pest dynamics, due in large part to bled grain sorghum yields from 26 to 59 residues left on the soil surface. Conservation bushels/A (423). tillage systems with surface residues create a The risk for early-season soil water depletion by more diverse plant/soil ecosystem than conven- cover crops is the same regardless of the tillage tional tillage systems (137, 185, 416). system. However, the full potential of cover crops Cover crops may harbor insects, diseases, and to increase infiltration and conserve soil water nematodes that could be harmful to the cash can only be achieved in a conservation system crop. Before planting a cover crop, be sure to where cover crop residues are left on the surface. investigate specific pest/crop interactions that Conservation tillage increased water use efficien- may become a problem (100). Understanding cy compared to a traditional wheat>fallow system these interactions and the conditions that favor with tillage (319, 135). them helps you make good management deci- One way to reduce the risk of early-season soil sions. For example: water depletion by cover crops is to desiccate the • Cereal rye, orchardgrass and crimson clover cover some time prior to planting the cash crop. may attract armyworms.

48 MANAGING COVER CROPS PROFITABLY • Clover root curculio, a common pest of red month after spring Consult local clover, can attack alfalfa. cover crop kill), and • Chickweed can attract black cutworm or August (under corn), experts to minimize slugs. suggest that the cover the potential for • Johnsongrass is a host to maize dwarf mosaic crops, living or dead, virus (MDMV), which also infects corn. increased bacterial pest problems activity and may have Conversely, cover crops can be used in conserva- enhanced nitrogen tion tillage systems to attract beneficial insects. cycling through the food web (432). One approach is to allow a live strip of cover The need for sound crop rotation is greater in crops to remain between crop rows to serve as conservation systems than in conventional sys- habitat and a food source until the main crop is tems. Cover crops should be a key component of established. This approach resulted in one less any conservation rotation system. With the vast insecticide application in conservation-tilled cot- number of potential combinations of crops, cover ton compared to conventional cotton in South crops, and diseases, consult local experts to Georgia (368, 416). ensure that you manage cover crops in conserva- For more information about cover crops and tion tillage systems to minimize the potential for beneficial insects, see Manage Insects on Your pest problems. Farm: A Guide to Ecological Strategies (409, Weed management. Cover crops affect http://www.sare.org/learning-center/insect). weeds and weed management in conservation Cover crop residues have been shown to tillage systems in several ways: reduce the incidence of several diseases in many • Cover crops compete with weeds for light, different cash crop systems by reducing splash water and nutrients. dispersal of pathogens. Small grain cover crops in • Cover crop residue can suppress weed seed conservation tillage have also been shown to germination; the more residue the better. reduce peanut yield losses from Tomato Spotted • Grass cover crops (high C:N ratio) usually pro- Wilt Virus (TSWV), with greater residue amounts vide longer-lasting residue than legumes. resulting in lower incidence of TSWV. This • Some cover crops release weed-suppressing benefit was directly related to less incidence of allelopathic compounds. damage from thrips, the vector of TSWV (49). • Conservation tillage does not continually turn Some cover crops can serve as an overwinter- up new weed seeds for germination. ing host for nematodes and may thus increase the • Cover crops can become weeds. severity of nematode damage. This may be a greater concern where crops are not rotated, like Some legume, cereal and brassica cover crops continuous cotton in some areas of the South. On release allelopathic compounds that can reduce the other hand, cover crops such as brassicas can weed populations and/or suppress weed growth reduce nematode populations (48, 231, 283, 284, (39, 45, 176, 177, 178, 336, 359, 410, 422). 285, 353, 430). Unfortunately, these same allelopathic com- On a Maryland sandy soil, winterkilled forage pounds can also stunt and/or kill cash crop radish increased bacteria-eating nematodes, rye seedlings, particularly cotton (24) and some small and rapeseed increased the proportion of fungal seeded vegetable crops. Allowing time between feeding nematodes, while nematode communities the termination date and the cash crop planting without cover crops were intermediate. The date reduces the risk to cash crops because these Enrichment Index, which indicates a greater chemicals leach out of the cover crop residue and abundance of opportunistic bacteria–eating are decomposed by soil microorganisms. nematodes, was 23% higher in soils that had Cereal rye is known to release phenolic and brassica cover crops than the unweeded control benzoic acids that can inhibit weed seed germi- plots. These samples, taken in November, June (a nation and development. In Arkansas, the concen-

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 49 tration of these allelopathic chemicals varied 100- about twice as much to establish as small grain fold among ten varieties of rye in the boot stage, covers. The increased cost of the legume cover with the cultivar BONEL having the greatest con- crop seed can be offset by the value of N that centration and PASTAR the least. Factoring in the legumes can replace. yield of each cultivar with the concentration and Depending on your system, legume cover activity of the inhibitors, BONEL, MATON and ELBON crops can replace 45 to 100 lb. N/A. On the were considered the best rye cultivars for allelo- other hand, a rye cover crop terminated at a late pathic use (66). stage of growth might require 20-30 lb. more Conservation tillage and the allelopathic effects N/A due to N immobilization by the wide C:N of cover crop residue can both contribute to the ratio rye residue. Thus, the difference in cost suppression of weeds in these systems (452). In between a rye cover crop and a legume cover Alabama, a conservation tillage system using rye crop would be offset by the value of 65 to 125 or black oat cover crops eliminated the need for lb. N/A. At a price of $0.45/lb. N, this would be post-emergence herbicides in soybean and cotton worth $29 to $56/A. (335, 349). Including rye or black oat increased yields of non-transgenic cotton in 2 of 3 years, com- Cover crop establishment in pared to conservation tillage without a cover crop. conservation tillage systems The major challenges to cover crop adoption in Economics of cover crop both tilled and conservation tillage systems establishment and use include seeding time and method, killing time and Using cover crops in any tillage system usually method, and cover crop residue management to costs more time and money than not using cover ensure good stands of the cash crop. Success with crops. Depending on your particular system, you cover crops requires adequate attention to each. may or may not be repaid for your investment Plant cover crops on time. In order to maxi- over the short term. If you are already using cover mize benefits—or to work at all—cover crops need crops but are considering switching to conserva- to be planted early, sometimes before the summer tion tillage, the economics are similar to using crop is harvested. Timely planting results in: cover crops in conventional tillage systems, but • good root establishment and topgrowth the benefits may be expressed more in the con- before the crops go dormant servation system (51). • reduced chance of winter kill Factors affecting the economics of cover crop • more biomass production compared to later use include: planting dates • the cash crop grown • greater uptake of residual soil N • the cover crop selected • time and method of establishment Timely fall planting is particularly important • method of termination before early vegetables or corn. Corn is typically • the cash value applied to the environment, soil planted early in the spring, which forces an early productivity and soil protection benefits cover crop termination date. A late planted cover derived from the cover crop. crop that must be terminated early will not pro- • the cost of nitrogen fertilizer and the fertilizer duce sufficient biomass to provide adequate soil value of the cover crop protection and enhance soil quality. • the cost of fuel Planting methods. Cover crops in conservation tillage systems are usually planted with a drill The economic picture is most affected by seed or broadcast on the soil surface, but several alter- costs, energy costs and nitrogen fertility dynamics nate methods can be used. Good soil-seed contact in cover crop systems. Cover crop seed costs vary is required for germination and emergence. Most considerably from year to year and from region to small seeded legumes require shallow seed place- region, but historically, legume cover crops cost ment (1/4 inch), while larger seeded legumes and

50 MANAGING COVER CROPS PROFITABLY small grains are generally planted up to 1.5 inch- ity for reseeding in Decisions about es deep (see CHARTS, p. 62). conservation-tillage sys- Conservation tillage drills can handle residue tems. Auburn University when to kill the and provide uniform seeding depth and adequate in cooperation with cover crop must seed-soil contact, even with small seeded cover USDA-NRCS has released crops. In some situations, preplant tillage can be several legume cover be site- and used to control weeds and disrupt insect and dis- crops that flower early, ease life cycles. including AU ROBIN situation-specific. Broadcast seeding requires an increase in the and AU SUNRISE crimson seeding rate compared to other methods (see clover, and AU EARLY CHARTS, p. 62). Broadcasting is often the least COVER hairy vetch (288). Leaving 25 to 50% of the successful seeding method. Small-seeded species row area alive when desiccating the cover crop such as clovers tend to establish better by broad- allows reseeding without reducing corn grain casting than larger seed species. A drop-type or yields. However, the strips of live cover crop may cyclone-type seeder can be used on small acreage compete with the cash crop for water, a potential and provides a uniform distribution of seed. problem during a spring drought. Conventional drills work adequately in some conservation tillage systems—depending on the Spring management of cover crops amount of residue—and may be more successful in conservation tillage systems than broadcast seeding. Kill date. Timing of cover crop termination On larger areas, aerial seeding by fixed-wing affects soil temperature, soil moisture, nutrient aircraft or helicopter in late summer during crop cycling, tillage and planting operations, and the die-down can be effective. As the leaves of the effects of allelopathic compounds on the subse- summer crop drop off, they aid germination by quent cash crop. Because of the many factors covering the seed, retaining moisture and pro- involved, decisions about when to kill the cover tecting the soil. crop must be site- and situation-specific. In colder climates, frost-seeding can be used There are a number of pros and cons of killing for some cover crop species (see individual a cover crop early vs. late. Early killing: cover crop chapters in this book). Seed is broad- • allows time to replenish soil water cast during late fall or early spring when the • increases the rate of soil warming ground has been “honeycombed” by freezing and • reduces phytotoxic effects of residues on cash thawing. The seed falls into the soil cracks and crops germinates when the temperature rises in the • reduces survival of disease inoculum spring. • speeds decomposition of residues, decreasing Some legumes can be managed to reseed the potential interference with planter operation following year. This reduces economic risks and • increases N mineralization from lower C:N seeding costs. Reseeding systems generally ratio cover crops depend on well-planned rotations such as that reported in Alabama (311), where crimson clover Advantages for later kill include: was followed with strip-tilled soybean planted • more residue available for soil and water con- late enough to let the clover reseed. Corn was servation grown the next year in the reseeded clover. In this • better weed control from allelopathic com- system, the cover crop is planted every other year pounds and mulch affect rather than annually. Grain sorghum can be plant- • greater N contribution from legumes ed late enough in the South to allow crimson • better potential for reseeding of the cover crop clover to reseed in a conservation-tillage system. The introduction of legume cover crops that bloom and set seed earlier also improves their util-

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 51 After 25 Years, Improvements Keep Coming By Pat Sheridan, Sheridan Farms, Fairgrove, Mich as interviewed by Ron Ross for the No-Till Farmer

Talk to 10 no-tillers and you’ll probably hear 10 as soon as we can; but if it’s wet, we let the rye different viewpoints on why it pays to quit dis- grow to suck up excess moisture. We can be turbing and start building the soil. At Sheridan very wet in the spring, but Michigan also Farms, we’ve got our list, too. We are able to bet- receives less rain during the growing season ter time planting, weed control and other pro- than any other Great Lakes state, on average. duction chores. And we’ve got the potential Moisture management is critical to us. for sediment and nutrient runoff into Saginaw We’ve seen less white Bay on Lake Huron under control. mold in no-tilled soy- An open mind Like a lot of no-tillers would testify, however, beans wherever we have welcomes a lot these changes didn’t come quickly, nor without heavy residue. We’ve had some reluctance and skepticism along the way. years with zero white of ideas that, In our first years of no-tilling, starting in 1982, mold when our conven- we did just about everything wrong and had an tional till neighbors with a little absolute train wreck. We overcame a few hur- faced a costly problem. tweaking, can dles early on, started adding more no-till acres It’s become a simple and were 100% continuous no-till by 1990. equation: the heavier the deliver even residue mat, the less more success Cover Crop Success white mold. We started working with cover crops about 20 to your fields. years ago. We deal with about a dozen different Deep-Rooted Crops soil types, 80 percent of which are clay loam. We’re looking for a cover And much of our land is poorly drained, low- crop that will help establish a more diverse organic-matter lake bed soils. rotation, so we can always follow a broadleaf Cereal rye has been a good cover crop year crop behind a grass crop and vice-versa. Oilseed in and year out for this mixture of soils. We like radish is beginning to show real promise. It has the AROOSTOCK variety from Maine because it about the same tremendous appetite for nitro- provides fast fall and spring growth and its gen as wheat, and it develops a very deep root smaller seed size makes it more economical to mass. It’s an excellent nutrient scavenger. plant. This combination enables the cover crop to In late August, we fly rye into standing corn capture maximum nitrogen from deep in the and also into soybeans if we’re coming back soil profile to feed the following corn crop. No with soybeans the following year. We learned one has ever proven to me that we need nutri- that rye is easier to burn down when it’s more ents down deep. It sounds good to have a plant than 2 feet tall than when it has grown only a food layer at 16 to 18 inches, but I much prefer foot or less. the nitrogen and other nutrients near the sur- The rye crop also helps us effectively manage face where the crop can use them. soil moisture. If it looks like we’re going to get Deep-rooted cover crops like oilseed radish a dry spring, we burn down rye with Roundup can help reverse the traditional theory of nitro-

52 MANAGING COVER CROPS PROFITABLY gen stratification. Nitrogen allowed to concen- What Works At Home? trate deep in the soil scares us because it is Our county is part of the Saginaw Bay water- more likely to leach into the tile lines and reach shed, the largest in the state with more than Lake Huron. 8,700 square miles. Everything we do as farm- We’ve also tried wheat, hairy vetch, crimson ers can affect the water quality of the bay, and clover and a dry bean and soybean mix for we’re very conscious of that. cover crops, and we’ll keep experimenting. A group of about 150 farmers from three Recently, I traded oilseed radish seed to Kansas counties formed the Innovative Farmers of no-tillers Red and David Sutherland for Austrian Michigan in 1994. Our objectives have been to winter pea seed. The Sutherlands have reported reduce the amount of sediment entering the good moisture retention and nitrogen fixation bay and change our farming practices to with the peas. We like what we’ve seen with the reduce nutrient and pesticide runoff. We peas, as well. don’t want our soils in the bay. After a 3-year study, financed with an EPA 319 grant in 1996, Less Nitrogen, More Corn we came up with some pretty dramatic results. We partly credit the cover crop program with We found that conservation tillage does not sharply reducing our fertilizer bills. In fact, the reduce yields; in fact we saw significant yield first time I hit a 200-bushel corn yield, I did it increases in corn. with only 140 to 150 pounds of nitrogen per Also, reduced tillage increases the soil’s acre, or about 0.7 to 0.8 pounds of nitrogen capacity to supply nitrogen and phosphorus to per bushel. As anyone who has been growing a growing crop. Water-holding capacity and corn knows, the typical nitrogen recommenda- water infiltration rates were higher on no-till tion has been about a pound-plus per bushel. fields. We reduced the potential for soil erosion Oversupplying nitrogen has absolutely no from water by up to 70 percent and from wind value. I think the whole nutrient cycle concept by up to 60 percent, compared to conventional is intriguing; no-till in conjunction with cover tillage. At the end of the project, we were get- crops really makes it work. ting a lot better handle on what no-till systems work best in our three-county area. Organic Matter Boost At Sheridan Farms, we’ll keep looking for When we started no-tilling, we had heard sto- more diversity and hope to get back to a four- ries from farmers and others that we could or five-crop continuous no-till system.The most expect to see increased organic matter content valuable lesson we learned is there is no uni- in our soils after a few years. But some soil versal truth or no-till game plan that will apply experts cautioned that this likely wouldn’t hap- for everyone. Eventually, we adapted a no-till pen. Fortunately, we’ve triggered significant system that fits our particular soil types, crops, humus development during the past 20 years, climate, long-range goals and farming style. with organic matter increasing from about 0.5 to as much as 2.5 percent. This is a real bonus —Adapted with permission from “The No-Till in addition to all the other benefits from no-till- Farmer,” May 2006. www.no-tillfarmer.com ing, and we expect to see even more improvement as we include more cover crops in our rotation.

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 53 As a general rule, cover crops, particularly cereals, ing in early season weed control. When using a need to be terminated 2-3 weeks ahead of planti- roller alone for cover crop termination, best ng to allow plant material to dry out and become results are obtained when rolling is delayed until brittle. Dry brittle cover crop residue allows flowering stage or later. tillage and planting equipment to cut through the Roller-crimpers work best with tall-growing cover residue more easily, as opposed to semi-dry cover crops. Small weeds are not killed by rolling. Weed crop residue. Semi-dry residue is tough and hard suppression by the mat of rolled cover crop residue to cut, which can result in considerable dragging depends on cover crop, weed species and height, and of the residue as implements traverse the field. the density (thickness) of the cover crop mat. Allelopathic compounds can be a greater prob- Rollers can be front- or rear-mounted. They usu- lem with crop establishment when fresh residues ally consist of a round drum with equally spaced become trapped in the seed furrow, a condition blunt blades around the drum. Blunt blades are known as “hairpinning.” Hairpinning can be a used to crimp the cover crop. This is preferable to problem even for residues that have been on the sharp blades that would cut the cover crop and surface for a number of weeks if planting in the dislodge residue that might interfere with seed morning when residues are still moist from pre- soil contact at planting. cipitation or dew. Hairpinning can reduce seed to The roller-crimper is a viable way to kill cover soil contact and cash crop stands. crops without using herbicides. It also helps pre- You can sometimes plant the cash crop directly vent planter problems that can occur when tall- into standing (live) cover crop, then kill the cover growing cover crops lodge in many different crop.This allows more time for cover crop growth directions after chemical termination and biomass production, and usually side-steps the In Alabama, a mechanical roller was used to kill problem of planting into tough cover crop residue. black oat, rye and wheat cover crops. The roller However, planting into standing green residue can combined with glyphosate at one-half the recom- increase the risk of allelopathic chemicals affecting mended rate was as effective as using glyphosate sensitive cash crop seedlings, and can make it diffi- at the full recommended rate to kill all cover cult to align rows when planting. crops. The key was to use the roller at flowering. Herbicides can be eliminated if the roller opera- Killing methods tion occurs at the soft dough stage or later, a good Many kill methods have been developed and test- option for organic growers (13). ed. Some are described below. Be sure to check with Extension or other farmers for recommend- ▼ Precaution: Applying non-selective herbicides ed methods for your area and crop system. at reduced rates could lead to weed resistance. Killing with an herbicide. Killing cover The half rate of herbicide may not completely crops with a non-selective herbicide is the stan- eradicate the weed, increasing the chance that the dard method used by conservation tillage grow- weed will produce seed. Under these circum- ers. They favor this option because they can cover stances, such seeds are more likely to be resistant many acres quickly and herbicides are relatively to the herbicide. Therefore, it is safer to com- cheap. Herbicides can be applied at any time or pletely eliminate the use of the non-selective growth stage to terminate the cover crop. herbicide with a roller or use the non-selective Killing with a roller-crimper. Cover crops herbicide at the labeled rate, with or without the can be killed using a mechanical roller (often roller. called a roller-crimper). The roller kills the cover Growers and researchers are addressing several crop by breaking (crimping) the stems. The barriers to the use of rollers: crimping action aids in cover crop desiccation. • Operation speed was hampered by vibration. The cover crop is rolled down parallel to the Using curved blades on the roller drum allevi- direction of planting to form a dense mat on the ates this problem. soil surface, facilitating planter operation and aid-

54 MANAGING COVER CROPS PROFITABLY • Most rollers are 8 rows or smaller, but growers In conservation tillage systems, living mulches can have built wider rollers that can be folded for improve nitrogen budgets, provide weed and ero- transportation. sion control, and may contribute to pest manage- • Rolling and planting can be done in one oper- ment and help mitigate environmental problems. ation by using a front-mounted roller and rear- Living mulch systems are feasible in Midwest mounted drill, saving time and energy. alfalfa-corn rotations (386). Use in corn-soybean rotations was also feasible but more challenging For more information about cover crop rollers, because soybean is more susceptible to competi- see ATTRA (11) and Cover Crop Roller Design tion from the living mulch. With adequate sup- Holds Promise for No-Tillers, p. 146. pression, living mulches can be managed to Mowing/chopping. Mowing and chopping minimize competition with corn with little or no are quick methods to manage large amounts of reduction in yield. The system requires close mon- cover crop residue by cutting it into smaller itoring and careful control of competition pieces. An alternative to the use of herbicides, it is between the living mulch and grain crop to main- more energy intensive. tain crop yields. In humid climates, mowed residues break Cash crop establishment. Cash crop estab- down faster, negating some of the residue benefits lishment can be complicated by the use of cover of conservation tillage. In drier climates, cover crops in conservation-tillage systems. Cover crops crop residues do not decompose as fast, but wind can reduce cotton, corn and soybean stands if not and water may cause residue to accumulate in managed well. Possible causes of stand reductions low areas or remove it from the field altogether. include: Cutting residue into smaller pieces may • poor seed-soil contact due to residue interfer- adversely affect the performance of tillage and ence with planter operations planting equipment because coulters designed to • soil water depletion cut through residue may instead push small • wet soils due to residue cover residue pieces into the soil. Use “row cleaners” or • cold soils due to residue cover “trash whippers” to prevent this problem. • allelopathic effects of cover crop residues Living mulch. Living mulches are cover crops • increased levels of soilborne pathogens that co-exist with the cash crop during the grow- • increased predation by insects and other pests ing season and continue to grow after the crop is • free ammonia (in the case of legume covers) harvested. Living mulches do not need to be reseeded each year (182). They can be chosen To prevent stand problems following cover crops: and managed to minimize competition with the • Check for good seed-soil contact and seed main cash crop yet maximize competition with placement, particularly seeding depth. weeds. The living mulch can be an annual or • Be sure that coulters are cutting through perennial plant established each year, or it can be cover crop residue rather than pushing it into an existing perennial grass or legume stand into the soil along with the seed. which a crop is planted. • Desiccate the cover crop at least 2 to 3 weeks Living mulch systems are dependent on adequate before planting the cash crop. moisture for the cash crop. They can be viable for • Monitor the emerging crop for early season vineyards, orchards, agronomic crops, such as corn, insect problems such as cutworms. soybean, and small grains, and many vegetables. Legumes are often used because they fix nitrogen, a Small seeded crops like vegetables and cotton are portion of which will be available for the compan- especially susceptible to stand reductions follow- ion crop. If excess nitrogen is a problem, living ing cover crops. Winter annual legumes may cause mulches (especially grasses) can serve as a sink to tie more problems due to allelopathic effects and/or up some of this excess nitrogen and hold it until the increased populations of plant pathogens. next growing season.

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 55 Residue management systems that leave cover emergence in the row creating unnecessary com- crop residue on the surface can reduce the risk of petition between weeds and the cash crop. stand problems provided the residue does not Spoked closing wheels improve establishment interfere with planter operation. in poorly drained or fine-textured soils. On these Good seed placement is more challenging soils, traditional cast-iron or smooth rubber clos- where residues remain on the soil surface. ing wheels can result in soil crusting. Spoked clos- However, improvements in no-till planter design ing wheels crumble the seed trench closed for have helped. Equipment that removes crop adequate seed to soil contact, but leave the soil residue from the immediate seeding area can help loose and friable for plant emergence. to reduce stand losses (see equipment discussion, Additional planter attachments to ensure ade- below). quate seed to soil contact in rough soil conditions Surface residues reduce soil temperature. The include V-slice inserts and seed firmers. V-slice relative influence of this temperature reduction inserts clean the seed trench created by the open- on crop growth is greater in northern areas of a ing disks. Seed firmers press the seed into the soil crop’s adapted zone. Removal of residue from the at the bottom of the seed trench. zone of seed placement will increase soil temper- Strip-tillage equipment. Strip-tillage equip- ature in the seed zone and also decrease the ment is designed to manage residue and perform amount of residue that comes in contact with the some non-inversion tillage in the row. In the seed. This will result in better seed-soil contact South, strip-tillage refers to in-row subsoiling (14- and less allelopathic effects from residue to the 16 inches deep) to reduce compaction, with min- developing seedling. imal disturbance of residue on the soil surface. In No-till planters. The key to successful no-till the Midwest, zone-tillage typically refers to shal- cash crop establishment in cover crop residues is low tillage within the row designed to remove adequate seed to soil contact at a desired seeding residue and enhance soil warming in the seed depth. No-till planters are heavier than conven- zone. tional planters. The additional weight allows the Regardless of manufacturer, strip tillage imple- planter to maintain desired seeding depth in ments typically consist of a coulter that runs rough soil conditions and prevents the planter ahead of a shank, followed by such attachments as from floating across the soil surface and creating additional coulters, rolling baskets, drag chains, or uneven seed placement. Individual planter row press wheels. Depending on conditions, these units are typically equipped with heavy-duty attachments are used alone or in various combi- down-pressure springs that allow the operator to nations to achieve different degrees of tillage. apply down pressure in uneven soil conditions to When strip-tilling in cover crop residue, the maintain depth control. coulter should be positioned as far forward of the Row cleaners are designed to operate in heavy shank as possible and centered on the shank. This cover crop residue. Manufacturers have devel- allows the coulter to operate in firm soil enabling oped different types of row cleaners that can be it to cut residue ahead of the shank. By cutting the matched to various planters. All row cleaners are residue ahead of the shank, the residue can flow designed to sweep residue away from the open- through the shanks more easily and not wrap up ing disks of the planter units. Removing this or drag behind the implement. residue reduces the chance of pushing residue Fine-textured soils sometimes stick to the into the seed furrow (hairpinning). shank and may accumulate there, disturbing too All row cleaners can be adjusted to match spe- much soil and making the slit too wide. This can cific field conditions. Row cleaners should be impede planter operations and is referred to as adjusted to move residue but not soil. If too much “blowout.” Plastic shields that fit over the shank soil is disturbed in the row, the soil will dry out help prevent blowout. Another way to reduce and can crust over, which will hinder emergence. blowout is to install splitter points on the subsoil In addition, disturbed soil can promote weed shanks. The splitter points look like shark fins

56 MANAGING COVER CROPS PROFITABLY that attach vertically upright to the tips of the Farm systems. Midwest farms are large, aver- shank points. They fracture the soil at the bottom aging 350 acres. Cover crops and conservation of the trench, preventing soil upheaval to the soil tillage are most common in corn and soybean sys- surface. The soil fracture created is analogous to tems, with or without livestock. Cover crops are stress cracks in concrete. also commonly used in vegetable systems. Row cleaners can be used on cool, poorly Cover crop species. Rye and other small drained soils to enable faster soil-warming in grains are the primary cover crops used in the spring. This may allow earlier planting and helps Midwest. Legume cover crop include red clover, ensure optimal plant emergence conditions. hairy vetch and sweetclovers. Available for most strip-tillage implements, row Cover crop benefits. Advantages of cover cleaners function much like row cleaners for crops in the Midwest include reducing erosion, planters, sweeping cover crop residue away from anchoring residues in no-till systems, suppressing the row.Adjustments for strip tillage row cleaners winter annual weeds and nutrient management. are not as flexible as those on planters. The ability of cover crops to scavenge nitrates is Vegetable establishment. Adop tion of no- particularly beneficial in the Midwest, where the tillage systems for transplanted vegetable crops majority of United States corn is produced, was limited by equipment and stand establish- because the high N requirement of corn increas- ment problems. This problem was overcome in es the potential for nitrate loss. the 1990’s with the development of the Subsur - Drawbacks. Cover crops have reduced corn face Tiller-Transplanter (287). The SST-T is a (but not soybean) yields when they are terminat- “hybrid,” combining subsurface soil loosening to ed at planting. Earlier termination helps reduce alleviate soil compaction and effective setting of this problem, but residue benefits are reduced. transplants, in one operation with minimum The potential biomass production is complicated disturbance of surface residues or surface soil. by the already short, cold cover crop growing sea- The spring-loaded soil-loosening com ponent of son between harvest and planting of corn and the subsurface tiller tills a narrow strip of soil soybean crops. Cash crop planting and harvest ahead of the double disk shoe of the transplanter. coincide with cover crop kill and planting dates. The double-disk shoe moves through the residue Management. Cover crops need to be planted and the tilled strip with relatively little resistance. at the same time farmers are harvesting corn and In addition, the planter can be equipped with fer- soybean to ensure adequate biomass production. tilizer and pesticide applicators to reduce the Producers would benefit from alternative cover number of trips required for a planting operation. crop establishment methods, such as overseeding before harvest, seeding at weed cultivation with Regional Roundup: Cover Crop Use delayed emergence, or frost seeding after harvest. in Conservation Tillage Systems Environmental payments or incentives may entice growers to try alternative practices. Midwest—Tom Kaspar Soils. Soils of the Midwest contain high levels of Northeast—Sjoerd Duiker organic matter compared to other regions. Cover crops are becoming an integral part of crop Research has yet to confirm if cover crops can production in the Northeast. This is due in large increase soil organic matter contents beyond cur- part to the increasing adoption of no-tillage sys- rent levels.The possibility of using corn stover as a tems, because cover crops can be managed more bioenergy source would leave the soil unprotected easily than with tillage, while cover crop residues and much more vulnerable to degradation, but in no-till systems lead to multiple benefits. cover crops could offset any detrimental effects Soils. There are many soil types in the associated with corn stover removal. The degree Northeast, including soils developed in glacial to which cover crops could protect the soil follow- deposits or from melt water lakes; sedimentary ing corn stover removal has not been investigated. soils formed from the sedimentary rocks sand-

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 57 stone, shale and limestone; Piedmont soils, rem- • timely seeding, overseeding into standing nants of a coastal mountain range with complex crops, or interseeding, including some use of geology, characterized by a gently to strongly undu- living mulches lating landscape; and coastal plain soils, developed • various termination methods, including mow- in unconsolidated material deposited by rivers and ing or rolling standing cover crops the ocean, often sandy with a shallow water table. • manipulation of cover crop kill and cash crop Soil and nutrient management in the region aim planting dates to maximize cover crop benefits to address soil erosion, clay subsoils, fragipans, shallow water tables and the nutrient enrichment Southeast—Kipling Balkcom caused by the high density of animal production. High-residue cover crops are essential to the suc- Farm systems. Farms in the Northeast are cess of conservation systems in the Southeast. diverse, tend to be small, and include cash grain, Soils. Soils in the Southeast are highly weath- perennial forage, dairy, hog, poultry, fruit and veg- ered, acidic, and often susceptible to erosion due etable operations. Nutrient management regula- to their low organic matter content. Decades of tions in some states encourage the use of cover conventional tillage practices have exacerbated crops and conservation tillage practices, particu- their poor physical and chemical condition. larly for the application of manure. Farmer orga- Farm systems. Southeast farms raise various nizations such as the Pennsylvania No-Till Alliance combinations of cotton, soybeans, corn, peanuts actively promote cover crops for their soil- and small grains. Some include livestock, have improving benefits, while government programs access to irrigation or raise fruit and vegetables. such as the 2006 Maryland cover crop subsidy of Cover crop species. Rye, wheat, oats, hairy $30-$50 per acre led to a dramatic increase in vetch and crimson clover are the cover crop cover crop acreage. mainstays for grain and oil crop systems. Cover crop species. Cover crop options and Cover crop benefits. Cover crop biomass is niches are as diverse as the farming systems in the needed on the weathered soils of the Southeast to region. Rye, wheat, oats and ryegrass are the most add organic matter and improve soil physical, common grass cover crops; hairy vetch, crimson chemical, and biological properties. Cover crop clover and Austrian winter pea are important residues reduce soil erosion and runoff, increase legumes; buckwheat finds a place in many veg- infiltration and conserve soil moisture, particularly etable systems and brassica crops such as forage beneficial in dry years or on drought-prone soils. radish are increasingly being tested and used in Drawbacks. Major concerns are: the region. • water management Cover crop benefits. Cover crops are planted • integration of different cover crop species into for erosion control, soil improvement, moisture southeastern crop production conservation, forage and nutrient management, • reduced effectiveness of pre-emergence herbi- particularly the nitrogen and phosphorus from cides in high-residue systems intensive animal agriculture. Cover crops can fit into many different niches in the region, particu- Producers are also concerned about residue inter- larly fruit and vegetable systems (1, 2, 3, 4). Recent ference with efficient equipment operation, ade- work with forage radish (Raphanus sativus L.) quate soil moisture at planting, and stand suggests that its large taproot can penetrate deep establishment problems. In addition, some are not soil layers and alleviate compaction (446). willing to commit to the additional management Drawbacks. Barriers to the adoption of cover level or perceived costs. crops include the time and cost of establishment Management. Producers like the idea of and management, water use, and, for some sys- reducing trips across the field, which reduces fuel tems, the length of the growing season. and labor costs and saves time. Significant increas- Management. Farmers and other researchers es in the use of cover crops and conservation fit cover crops into many different niches using: tillage systems in the Southeast have paralleled

58 MANAGING COVER CROPS PROFITABLY the adoption of new genetic varieties of corn, soy- Southern Plains —Louis Baumhardt bean and cotton that are herbicide resistant or Conservation tillage was first introduced for soil have incorporated genes for improved insect erosion control on the Great Plains. It followed resistance. These genetic changes reduced some inversion tillage that incorporated crop residue of the challenges associated with weed and insect and degraded the soil’s natural cohesiveness and management, making the conservation tillage sys- aggregation. Combined with the 1930’s dry and tems easier to manage. The relatively longer grow- windy conditions, this intensive tillage produced ing season usually allows ample time to plant catastrophic wind erosion known historically as cover crops after cash crops. the “Dust Bowl” (26). Use of conservation tillage practices for much of the Southern Great Plains Northern Plains—Jorge Delgado seems to lag behind other regions, but may be Rainfall and moisture availability are the major fac- underestimated, in part, because insufficient tors affecting the use of cover crops in conserva- residue is produced in dryland areas to qualify as tion tillage systems. conservation tillage acres. Soils. Soils of the Northern Great Plains are Soils. Soils of the Southern Great Plains were exposed to high wind conditions with enough formed from a range of materials including, for force to move soil particles off site in minimum example, an almost flat aeolian mantle in the tillage conditions where soil cover is low. Crop north (Texas High Plains and western Kansas) and systems do not, in general, leave substantial reworked Permian sediments of the Texas Rolling residue on the soil surface, due in part to low Plains extending towards western Oklahoma. annual rainfall in non-irrigated systems. These soils have varied mineralogy, are frequently Farm systems. Farms in the Northern Plains calcareous, and generally have poor structure and tend to be large and can be divided into irrigated low organic matter content (37). All Southern and non-irrigated systems. Crops rotations include Great Plains soils are managed for wind erosion potato, safflower, dry bean, sunflower, canola, control and water conservation. crambe, flax, soybean, dry pea, wheat and barley. Farm systems. Farm systems on the Southern Cover crop species. Rye, field pea (Austrian Great Plains vary with irrigation. They are larger winter pea, trapper spring pea), sweetclover and and more diverse as irrigation declines to distrib- sorghum-sudangrass are commonly grown. ute risk and meet production requirements. Cover crop benefits. Cover crop residues Principal crops include cotton, corn, peanut, grain improve water retention, helping to increase soil sorghum, soybean, and sunflower. Grain and for- water content and yields. Cover crops reduce wind age crops support the regional cattle industry. erosion and nutrient loss, and increase soil carbon. Wheat-sorghum-fallow is a common rotation High crop residue and winter cover crops also and permits cattle grazing on wheat forage and sequester carbon and nitrogen and increase the avail- sorghum stubble (27). This and similar rotations ability of other macro- and micronutrients (7, 113). may include additional years of sorghum or a Drawbacks. Rainfall amount, the availability of wheat green fallow before cotton. irrigation and water use by cover crops are criti- Cover crop species. Water governs cover cal considerations for the region. Cool, wet spring crop species selection, but wheat, rye, and oats weather is exacerbated by cover crop residues are most common. Wheat is commonly grown for that delay soil-warming. Cover crops and conser- grain or forage and as a green fallow crop vation tillage often reduce cash crop yields, even between annual cotton crops (29). in irrigated systems (171, 172). Cover crop benefits. Cover crop residue Management. Management is key to increas- helps meet the 30% cover requirement for con- ing nutrient use efficiencies and reduce nutrient servation tillage, helps control wind erosion in losses to the environment (112, 113, 114, 371). low residue crops, and provides other water infil- Management is also the key to increasing water tration and storage benefits. use efficiency.

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 59 Drawbacks. Cover crop use in the region ing from 1-2%. Soils developing on the flood depends on precipitation or the availability and deposits of Glacial Lakes’ Missoula and Bonneville economy of irrigation to produce residue. Some in the Columbia Basin of Washington, Oregon and crops such as cotton produce insufficient residue Idaho are predominately sands to silt loams with for soil cover, but establishing cover crops com- weak soil structure and low soil organic C (<1%). petes for water needed by the subsequent cotton Cultivated soils of the region are exposed to crop (28). Grazing crop residues and cover crops severe soil erosion from water and snow melt in also limits the amount of crop residue left on the the higher precipitation zones and due to high soil surface and must be balanced against the wind conditions in low rainfall areas (Columbia value of the forage. Basin). Management. Southern Great Plains produc- Farm systems. Farms in the dryland and irri- ers often use cover crops to control wind erosion gated regions of the PNW tend to be large in annual crops like cotton that produce insuffi- (2,000+ acres on average). Dryland regions are cient cover to protect the soil. During years with commonly cropped to wheat, barely, canola, oats, limited precipitation, cover crops compete for grass seed and dry peas. Crop rotations under irri- water resources needed to establish primary cash gation are diverse, vegetable based rotations that crops (28). Nevertheless, producers wishing to include potato, onion, carrots, field corn, sweet grow cotton on soils subject to wind erosion have corn, fresh beans and peas, sugar beets, mint, successfully introduced residue producing winter canola, mustards, safflower, dry pea, grass seed, cereal crops with minimum irrigation input. alfalfa, wheat and barley. Conservation tillage increases storage of pre- Cover crop species. Field pea (Austrian cipitation in the soil through increased infiltration winter pea), sweetclover, hairy vetch, sudangrass, and reduced evaporation. This additional water small grains (wheat, triticale) and a variety of supplements growing season precipitation and brassica species are used in the region. irrigation to meet crop water needs on the semi- Cover crop benefits. Cover crop residues arid Southern Great Plains. improve water retention, infiltration and storage, soil structure, soil carbon reserves, microbial Pacific Northwest —Hal Collins activity and crop yields. Cover crop residues have Under dryland conservation tillage systems in the been shown to reduce water and wind erosion Pacific Northwest (PNW), winter precipitation and nutrient loss from leaching and overland flow and limited water availability are major factors of sediments. High crop residues and the use of affecting the use of cover crops. With irrigation, winter cover crops under irrigation sequester car- heavy crop residues from previous grain crops bon and nitrogen and increase the availability of can negatively impact cover crop stand establish- other macro and micronutrients. Cover crop ment. Annual precipitation in agricultural regions residues can meet or exceed the 30% cover of the PNW ranges from 15 to 76 cm, due to oro- requirement for conservation tillage in low rain- graphic effects of the Cascade and Blue Mountain fed areas. Ranges that strongly influence total precipitation Drawbacks. Rainfall amount and distribution, and distribution patterns in Washington, Oregon the availability of irrigation and water use by cover and Idaho. crops are critical considerations for the dryland Soils. Soils of the PNW have developed from regions. Heavy residues under irrigation inhibit aeolian and flood deposits originating from vol- stand establishment. Cool, wet spring weather exac- canic activity and the last continental glaciations erbated by cover crop residues delay soil warming (~12,000 years BP) under shrub-steppe vegeta- and seedling emergence of cash crops. Absentee tion. Soils that developed on wind blown loessal land owners combined with the diversity of crop- deposits are typically silt loams with moderate to ping under irrigation of high value vegetable crop- strong structure and soil organic C contents rang- ping has limited adoption of conservation tillage

60 MANAGING COVER CROPS PROFITABLY and cover crop use. Cover crops and conservation California’s Central Valley. Aboveground biomass tillage can reduce economic benefits and crop production can reach 11,000 lb. of aboveground yields under some situations. dry matter/A without irrigation (279, 280). Management. Management of cover crops is The cover crops are mowed or chopped in complex and differs in dryland and irrigated sys- March using ground-driven stalk choppers, or tems. Cover crops are managed to reduce nutrient merely allowed to collapse following herbicide losses, increase nutrient use efficiencies and application. reduce severity of soil pathogens (88, 111, 115, Tomatoes can be no-till transplanted directly 430). Management is also key to increasing water into the mulch or transplanted following a strip- use efficiency and can affect protein content of till pass using either narrow PTO-driven rotary small grains. mulchers or ground-driven strip-till implements modified for tomato beds (250). Because of inad- California —Jeffrey Mitchell equate weed control by the cover crop mulch Despite the many benefits of cover cropping and itself, high residue cultivators that effectively slice conservation tillage, adoption by row crop pro- through residues while cultivating weeds are nec- ducers in California has been limited. Cover crops essary for in-season weed control. are used on less than 5% of California’s annual Field corn has also been successfully direct crop acreage and conservation tillage practices seeded into flail mowed vetch cover crops in the are used on less than 2% of annual cropland. Sacramento Valley. Corn yield is similar to “green Soils. A wide range of soil types are used for manure” systems in which winter cover crops are agricultural production in California. Cover crops incorporated. and conservation tillage are used predominantly on finer-textured clay loams or loam soils. More SUMMARY AND RECOMMENDATIONS recently, conservation tillage is increasingly used in dairy forage production systems on coarser soil Cover crops benefit conservation tillage systems types. by: Farm systems. Most cover crop use in con- • decreasing soil erosion servation tillage systems in California has been for • providing crop residues to increase soil processing and fresh market commercial tomato organic matter production systems (187). Research is underway • improving soil structure and increasing evaluating cover crops in CT corn and cotton sys- infiltration tems (281). • increasing availability of water for crop Cover crop species. In tomato systems, the production most successful and manageable cover crops are • improving soil quality mixtures of triticale, rye and pea. Vetches are used • aiding in early season weed control for field corn. • breaking disease cycles Cover crop benefits. California farmers use cover crops to reduce intercrop tillage, suppress To enhance the beneficial effects of cover crops: winter weeds, reduce pathogen buildup and man- • Plant in a timely fashion. age nutrients. • Consider additional N fertilizer for small grain Drawbacks. Producers are most concerned covers only if residual N is low. about cooler temperatures above and below • Terminate covers 2-3 weeks ahead of antici- mulch, slower maturing crops, cover crop pated planting date to allow soil moisture regrowth and specialized management required. recharge and reduce problems associated with In-season weed management options may be lim- allelopathy, pests, and planter operation. ited in conservation tillage systems. • Take advantage of equipment modifications Management. Cover crops are normally designed for tillage and/or planter operations grown from mid-October to mid-March in in heavy residue.

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 61 INTRODUCTION TO CHARTS

he four comprehensive charts that follow more seasonal details. The added effect of a nurse can help orient you to the major cover crop is included in the “Weed Fighter” ratings for Tcrops most appropriate to your needs and legumes usually planted with a grain or grass region. Bear in mind that choice of cultivar, weath- nurse crop. er extremes and other factors may affect a cover crop’s performance in a given year. Column headings Legume N Source. Rates legume cover crops for CHART 1: TOP REGIONAL COVER their relative ability to supply fixed N. CROP SPECIES (Nonlegumes have not been rated for their bio - mass nitrogen content, so this column is left blank This chart lists up to five cover crop recommen - for nonlegumes.) dations per broad bioregion for six different major purposes: N Source, Soil Builder, Erosion Total N. A quantitative estimate of the reason - Fighter, Subsoil Loosener, Weed Fighter and Pest ably expected range of total N provided by a Fighter. If you know your main goal for a cover legume stand (from all biomass, above- and below crop, Chart 1 can suggest which cover crop ground) in lb. N/A, based mostly on published entries to examine in the charts that follow and research. This is total N, not the fertilizer replace - help you determine which major cover narra - ment value. Grasses have not been rated for their tive(s) to read first. biomass nitrogen content because mature grass Disclaimer. The crops recommended here residues tend to immobilize N. Brassicas are less will not be the most successful in all cases within likely to immobilize N than grasses. a bioregion, and others may work better in some locations and in some years. The listed cover Dry Matter. A quantitative estimate of the range crops are, however, thought by reviewers to have of dry matter in lb./A/yr., based largely on pub- the best chance of success in most years under lished research. As some of this data is based on current management regimes. research plots, irrigated systems or multicut systems, your on-farm result probably would be in the CHART 2: PERFORMANCE AND ROLES low to midpoint of the dry matter range cited. This estimate is based on fully dry materi al. “Dry” alfalfa This chart provides relative ratings (with the hay is often about 20 percent moisture, so a ton of exception of two columns having quantitative hay would only be 1,600 lb. of “dry matter.” ranges) of what the top covers do best, such as supply or scavenge nitrogen, build soil or fight N Scavenger. Rates a cover crop’s ability to take erosion. up and store excess nitrogen. Bear in mind that Seasonality has a bearing on some of these rat- the sooner you plant a cover after main crop har- ings. A cover that grows best in spring could sup - vest—or overseed a cover into the standing press weeds better than in fall. Unless otherwise crop—the more N it will be able to absorb. footnoted, however, the chart would rate a cover’s performance (relative to the other covers) for the Soil Builder. Rates a cover crop’s ability to pro - entire time period it is likely to be in the field. duce organic matter and improve soil structure. Ratings are general for the species, based on mea - The ratings assume that you plan to use cover sured results and observations over a range of crops regularly in your cropping system to pro - conditions. The individual narratives provide vide ongoing additions to soil organic matter.

62 MANAGING COVER CROPS PROFITABLY Erosion Fighter. Rates how extensive and how Type. Describes the general life cycle of the crop. quickly a root system develops, how well it holds soil against sheet and wind erosion and the influ - B = Biennial. Grows vegetatively during its first ence the growth habit may have on fighting wind year and, if it successfully overwinters, sets seed erosion. during its second year.

Weed Fighter. Rates how well the cover crop CSA = Cool-Season Annual. Prefers cool tem - outcompetes weeds by any means through its life peratures and depending on which Hardiness cycle, including killed residue. Note that ratings Zone it is grown in, could serve as a fall, winter or for the legumes assume they are established with spring cover crop. a small-grain nurse crop. SA = Summer Annual. Germinates and matures Good Grazing. Rates relative production, nutrit - without a cold snap and usually toler ates warm ional quality and palatability of the cover as a for- temperatures. age. WA = Winter Annual. Cold-tolerant, usually Quick Growth. Rates the speed of establishment planted in fall and often requires freezing temper- and growth. atures or a cold period to set seed.

Lasting Residue. Rates the effectiveness of the LP = Long-lived Perennial. Can endure for cover crop in providing a long-lasting mulch. many growing seasons.

Duration. Rates how well the stand can provide SP = Short-lived Perennial. Usually does not long-season growth. persist more than a few years, if that long.

Harvest Value. Rates the cover crop’s economic Hardy Through Zone. Refers to the standard value as a forage (F) or as a seed or grain crop (S), USDA Hardiness Zones. See map on inside front bearing in mind the relative market value and cover. Bear in mind that regional microclimate, probable yields. weather variations, and other near-term manage - ment factors such as planting date and compan - Cash Crop Interseed. Rates whether the cover ion species can influence plant performance crop would hinder or help while serving as a expectations. companion crop. Tolerances. How well a crop is likely to endure CHART 3A: CULTURAL TRAITS despite stress from heat, drought, shade, flooding or low fertility. The best rating would mean that This chart shows a cover crop’s characteristics the crop is expected to be fully tolerant. such as life cycle, drought tolerance, preferred soils and growth habits. The ratings are general for Habit. How plants develop. the species, based on measured results and obser- C = Climbing vations over a range of conditions. Choice of cul- U = Upright tivar, weather extremes and other factors may P = Prostrate affect a cover crop’s performance in a given year. SP = Semi-Prostrate SU = Semi-Upright Column headings Aliases. Provides a few common names for the pH Preferred. The pH range in which a species cover crop. can be expected to perform reasonably well.

CHARTS 63 Best Established. The season in which a cover Inoculant Type. The recommended inoculant crop is best suited for planting and early growth. for each legume. Your seed supplier may only Note that this can vary by region and that it’s carry one or two common inoculants. You may important to ascertain local planting date rec - need to order inoculant in advance. See Seed ommendations for specific cover crops. Suppliers, p. 195. Season: F = Fall ; Sp = Spring; Su = Summer; W = Winter Reseeds. Rates the likelihood of a cover crop re - Time: E = Early; L = Late; M = Mid establishing through self-reseeding if it’s allowed to mature and set seed. Aggressive tillage will bury Minimum Germination Temperature. The seed and reduce germination. Ratings assume the minimum soil temperature (F) generally required tillage system has minimal effect on reseeding. for successful germination and establishment. Dependable reseeding ability is valued in some orchard, dryland grain and cotton systems, but CHART 3B: PLANTING can cause weed problems in other systems. See the narratives for more detail. Depth. The recommended range of seeding depth (in inches), to avoid either overexposure or CHARTS 4A AND 4B burying too deeply. These charts provide relative ratings of other Rate. Recommended seeding rate for drilling and management considerations—benefits and possi - broadcasting a pure stand in lb./A, bu/A. and ble drawbacks—that could affect your selection oz./100 sq. ft., assuming legal standards for germi - of cover crop species. nation percentage. Seeding rate will depend on The till-kill rating assumes tillage at an appro - the cover crop’s primary purpose and other fac - priate stage. The mow-kill ratings assume mowing tors. See the narratives for more detail about at flowering, but before seedheads start maturing. establishing a given cover crop. Pre-inoculated See sectional narratives for details. (“rhizo-coated”) legume seed weighs about one- Ratings are based largely on a combination of third more than raw seed. Increase seeding rate published research and observations of farmers by one-third to plant the same amount of seed per who have grown specific covers. Your experience area. with a given cover could be influenced by site- specific factors, such as your soil condition, crop Cost. Material costs (seed cost only) in dollars per rotation, proximity to other farms, weather pound, based usually on a 50-lb. bag as of fall extremes, etc. 2006. Individual species vary markedly with sup - ply and demand. Always confirm seed price and CHART 4A: POTENTIAL ADVANTAGES availability before ordering, and before planning to use less common seed types. Soil Impact. Assesses a cover’s relative ability to loosen subsoil, make soil P and K more readily Cost/A. Seed cost per acre based on the midpoint available to crops, or improve topsoil. between the high and low of reported seed prices as of fall 1997 and the midpoint recommended Soil Ecology. Rates a cover’s ability to fight pests seeding rate for drilling and broadcasting. Your by suppressing or limiting damage from nema- cost will depend on actual seed cost and seeding todes, soil disease from fungal or bacterial infec- rate. Estimate excludes associated costs such as tion, or weeds by natural herbicidal (allelopathic) labor, fuel and equipment. or competition/smothering action. Researchers

64 MANAGING COVER CROPS PROFITABLY report difficulty in conclusively documenting rarely causes pest problems, but certain cover allelopathic activity distinct from other cover crops may contribute to particular pest, disease or crop effects, and nematicidal impacts are variable, nematode problems in localized areas, for exam- studies show. These are general, ten tative ratings ple by serving as an alternate host to the pest. See in these emerging aspects of cover crop influ- the narratives for more detail. ence. ▼ Readers note the shift in meaning for symbols Other. Indicates likelihood of attracting benefi - on this chart only. cial insects, of accommodating field traffic (foot or vehicle) and of fitting growing windows or short Management Challenges. Relative ease or diffi - duration. culty of establishing, killing or incorporating a stand. “Till-kill” refers to killing by plowing, disking CHART 4B: POTENTIAL or other tillage. “Mature incorporation” rates the DISADVANTAGES difficulty of incorporating a relatively mature stand. Incorporation will be easier when a stand is Increase Pest Risks. Relative likelihood of a killed before maturity or after some time elapses cover crop becoming a weed, or contributing to a between killing and incorporating. likely pest risk. Overall, growing a cover crop

CHARTS 65 Chart 1 TOP REGIONAL COVER CROP SPECIES1

Soil Erosion Subsoil Weed Pest Bioregion N Source Builder Fighter Loosener Fighter Fighter

Northeast red cl, hairy v, ryegrs, swt cl, rye, ryegrs, sorghyb, sorghyb, rye, berseem, sorghyb, sub cl, swt cl, ryegrs, rye, sorghyb, swt cl rye oats forad buckwheat rape Mid-Atlantic hairy v, red cl, ryegrs, rye, sub cl, sorghyb, rye, ryegrs, rye, berseem, swt cl, cowpeas, swt cl, oats, sorghyb, crim cl sorghyb rye, ryegrs forad buckwheat rape Mid-South hairy v, sub cl, ryegrs, rye, sub cl, sorghyb, buckwheat, rye, berseem, sub cl, cowpeas, swt cl ryegrs, sub cl, sorghyb crim cl sorghyb rye, ryegrs rye Southeast Uplands hairy v, red cl, ryegrs, rye, sub cl, sorghyb, buckwheat, rye, berseem, sorghyb, cowpeas, rye, swt cl ryegrs, sub cl, sorghyb crim cl swt cl ryegrs rye Southeast Lowlands winter peas, ryegrs, sub cl, sorghyb berseem, rye, rye, sub cl, hairy v, rye, cowpeas, wheat, sorghyb berseem, sorghyb, rye, ryegrs, cowpeas, crim cl sub cl sorghyb oats, ryegrs Great Lakes hairy v, red cl, ryegrs, rye, oats, sorghyb, berseem, rye, berseem, sorghyb, rye, swt cl, ryegrs, rye, sorghyb, crim cl ryegrs, swt cl ryegrs forad buckwht, oats rape Midwest Corn Belt hairy v, red cl, rye, barley, wht cl, rye, sorghyb, rye, ryegrs, rye, berseem, sorghyb, ryegrs, swt cl, wheat, sorghyb crim cl swt cl barley forad buckwht, oats Northern Plains hairy v, swt cl, rye, barley, rye, sorghyb, medic, rye, rye, medics medic, swt cl barley swt cl barley sorghyb Southern Plains winter peas, rye, barley, rye, sorghyb, rye, rye, medic, hairy v medic barley swt cl barley sorghyb Inland Northwest winter peas, medic, swt cl, rye, sorghyb, rye, wheat, rye, mustards, hairy v rye, barley barley swt cl barley sorghyb Northwest Maritime berseem, ryegrs, rye, wht cl, rye, sorghyb, ryegrs, rye, sub cl, lana v, sorghyb, ryegrs, swt cl lana v, oats, mustards crim cl lana v barley wht cl Coastal California berseem, ryegrs, rye, wht cl, sorghyb, rye, ryegrs, sorghyb, sub cl, sorghyb, cowpeas, swt cl berseem, crim cl, lana v, medic lana v rye, ryegrs wht cl rye Calif. Central Valley winter peas, medic, wht cl, sorghyb, ryegrs, sorghyb, lana v, sub cl, sub cl barley, rye, swt cl wht cl, rye, crim cl, medic ryegrs lana v rye Southwest medic, sub cl, barley, medic, sub cl medic, barley sorghyb barley

1ryegrs=annual ryegrass. buckwht=buckwheat. forad=forage radish. rape=rapeseed. sorghyb=sorghum-sudangrass hybrid. berseem=berseem clover. winter peas=Austrian winter pea. crim cl=crimson clover. hairy v=hairy vetch. red cl=red clover. sub cl=subterranean clover. swt cl=sweetclover. wht cl=white clover. lana v=LANA woollypod vetch.

66 MANAGING COVER CROPS PROFITABLY Chart 2 PERFORMANCE AND ROLES

Legume Total N Dry Matter N Soil Erosion Weed Good Quick Species N Source (lb./A)1 (lb./A/yr.) Scavenger2 Builder3 Fighter4 Fighter Grazing5 Growth

Annual ryegrass p. 74 2,000–9,000

Barley p. 77 2,000–10,000

Oats p. 93 2,000–10,000

Rye p. 98 3,000–10,000

Wheat p. 111 3,000–8,000 NONLEGUMES Buckwheat p. 90 2,000–4,000

Sorghum–sudan. p. 106 8,000–10,000

Mustards p.81 30–120 3,000–9,000

Radish p. 81 50–200 4,000–7,000

BRASSICASRapeseed p. 81 40–160 2,000–5,000

Berseem clover p. 118 75–220 6,000–10,000

Cowpeas p. 125 100–150 2,500–4,500

Crimson clover p. 130 70–130 3,500–5,500

Field peas p. 135 90–150 4,000–5,000

Hairy vetch p. 142 90–200 2,300–5,000

Medics p. 152 50–120 1,500–4,000

Red clover p. 159 70–150 2,000–5,000 LEGUMES Subterranean clovers p.164 75–200 3,000–8,500

Sweetclovers p. 171 90–170 3,000–5,000

White clover p. 179 80–200 2,000–6,000

Woollypod vetch p. 185 100–250 4,000–8,000

1Total N—Total N from all plant. Grasses not considered N source. 2N Scavenger—Ability to take up/store excess nitrogen. 3Soil Builder—Organic matter yield and soil structure improvement. 4Erosion Fighter—Soil-holding ability of roots and total plant. 5Good Grazing—Production, nutritional quality and palatability. Feeding pure legumes can cause bloat. =Poor; =Fair; =Good; =Very Good; =Excellent

CHARTS 67 Chart 2 PERFORMANCE AND ROLES continued

Lasting Harvest Cash Crop Species Residue1 Duration2 Value3 Interseed4 Comments F* S*

Annual ryegrass Heavy N and H20 user; cutting boosts dry matter significantly. Barley Tolerates moderately alkaline conditions but does poorly in acid soil < pH 6.0. Oats Prone to lodging in N-rich soil. Rye Tolerates triazine herbicides.

Wheat Heavy N and H20 user in spring. NONLEGUMES Buckwheat Summer smother crop; breaks down quickly. Sorghum–sudangrass Mid-season cutting increases yield & root penetration. Mustards Suppresses nematodes and weeds. Radish Good N scavenging and weed control; N released rapidly.

BRASSICASRapeseed Suppresses Rhizoctonia. Berseem clover Very flexible cover crop, green manure, forage. Cowpeas Season length, habit vary by cultivar. Crimson clover Established easily, grows quickly if planted early in fall; matures early in spring. Field peas Biomass breaks down quickly. Hairy vetch Bi-culture with small grain expands seasonal adaptability. Medics Use annual medics for interseeding. Red clover Excellent forage, easily established; widely adapted. LEGUMES Subterranean clover Strong seedlings, quick to nodulate. Sweetclovers Tall stalks, deep roots in second year. White clover Persistent after first year. Woollypod vetch Reseeds poorly if mowed within 2 months of seeddrop; overgrazing can be toxic.

1Lasting Residue—Rates how long the killed residue remains on the surface. 2Duration—Length of vegetative stage. 3Harvest Value—Economic value as a forage (F) or as seed (S) or grain. 4Cash Crop Interseed—Rates how well the cover crop will perform with an appropriate companion crop. =Poor; =Fair; =Good; =Very Good; =Excellent

68 MANAGING COVER CROPS PROFITABLY Chart 3A CULTURAL TRAITS Hardy Tolerances Min. through pH Best Germin. Species Aliases Type1 Zone2 Habit3 (Pref.) Established4 Temp. heat drought shade flood low fert

Annual ryegrass p. 74 Italian ryegrass WA 6U6.0–7.0 ESp, LSu, 40F EF, F

Barley p. 77 WA 7U6.0–8.5 F, W, Sp 38F Oats p. 93 spring oats CSA 8U4.5–7.5 LSu, ESp 38F W in 8+

Rye p. 98 winter, cereal, CSA 3U5.0–7.0 LSu, F 34F or grain rye

Wheat p. 111 WA 4U6.0–7.5 LSu, F 38F NONLEGUMES Buckwheat p. 90 SA NFT U/SU 5.0–7.0 Sp to LSu 50F SU

Sorghum–sudan. p. 106 Sudax SA NFT U 6.0–7.0 LSp, ES 65F Mustards p.81 brown, oriental WA, 7U5.5–7.5 Sp, LSu 40F white, yellow CSA

Radish p. 81 oilseed,Daikon, CSA 6U6.0–7.5 Sp, LSu, EF 45F forage radish

BRASSICASRapeseed p. 81 rape, canola WA 7U5.5–8 F, Sp 41F

Berseem clover p. 118 BIGBEE, SA, WA 7 U/SU 6.2–7.0 ESp, EF 42F multicut SU

Cowpeas p. 125 crowder peas, SA NFT SU/C 5.5–6.5 ESu 58F southern peas

Crimson clover p. 130 WA, SA 7 U/SU 5.5–7.0 LSu/ESu Field peas p. 135 winter peas, WA 7C6.0–7.0 F, ESp 41F black peas

Hairy vetch p. 142 winter vetch WA,CSA 4C5.5–7.5 EF, ESp 60F Medics p. 152 SP, SA 4/7 P/Su 6.0–7.0 EF, ESp, ES 45F Red clover p. 159 SP, B 4U6.2–7.0 LSu; ESp 41F LEGUMES Subterranean cl. p. 164 subclover CSA 7 P/SP 5.5–7.0 LSu, EF 38F Sweetclovers p. 171 B, SA 4U6.5–7.5 Sp/S 42F

White clover p. 179 white dutch LP, WA 4 P/SU 6.0–7.0 LW, E to 40F ladino LSp, EF

Woollypod vetch p. 185 Lana CSA 7 SP/C 6.0–8.0 F

1B=Biennial; CSA=Cool season annual; LP=Long-lived perennial; SA=Summer annual; SP=Short-lived perennial;WA=Winter annual 2See USDA Hardiness Zone Map, inside front cover. NFT=Not frost tolerant. 3C=Climbing; U=Upright; P=Prostrate; SP=Semi-prostrate; SU=Semi-upright. 4E=Early; M=Mid; L=Late; F=Fall; Sp=Spring; Su=Summer; W=Winter =Poor; =Fair; =Good; =Very Good; =Excellent

CHARTS 69 Chart 3B PLANTING

Cost Cost/A Inoc. Species Depth Seeding Rate ($/lb.)1 (median)2 Type Reseeds3 Drilled Broadcast lb./A bu/A lb./A bu/A oz./100 ft2 drilled broadcast

1 Annual ryegrass 0– /2 10–20 .4–.8 20–30 .8–1.25 1 .70–1.30 12 24 U

3 Barley /4–2 50–100 1–2 80–125 1.6–2.5 3-5 .17–.37 20 27 S

1 1 Oats /2–1 /2 80–110 2.5–3.5 110–140 3.5–4.5 4–6 .13–.37 25 33 S

3 Rye /4–2 60–120 1-2 90–160 1.5–3.0 4–6 .18–.50 25 35 S

1 1 Wheat /2–1 /2 60–120 1–2 60–150 1–2.5 3–6 .10–.30 18 22 S

NONLEGUMES 1 1 Buckwheat /2–1 /2 48–70 1–1.4 50–90 1.2–1.5 3–4 .30–.75 32 38 R

1 1 Sorghum-sudangrass /2–1 /2 35 1 40–50 1–1.25 2 .40–1.00 26 34 S

1 3 Mustards /4– /4 5–12 10–15 11.50–3.00 16 24 U

1 1 Radish /4– /2 8–13 10–20 1 1.50–2.50 22 32 S

1 3 Rapeseed /4– /4 5–10 8–14 11.00–2.00 11 16 S BRASSICAS

1 1 Berseem clover /4– /2 8–12 15–20 2 1.70– 22 39 crimson, N 2.50 berseem

1 Cowpeas 1–1 /2 30–90 70–120 5 .85– 71 113 cowpeas, S 1.50 lespedeza

1 1 Crimson clover /4– /2 15-20 22–30 2–3 1.25– 27 40 crimson, U 2.00 berseem

1 Field peas 1 /2–3 50–80 90–100 4 .61–1.20 50 75 pea, vetch S

1 1 Hairy vetch /2-1 /2 15–20 25–40 2 1.70–2.50 35 65 pea, vetch S

1 1 Medics /4– /2 8–22 12–26 2/3 2.50– 58 75 annual R 4.00 medics

1 1 Red clover /4– /2 8–10 10–12 3 1.40– 23 28 red cl, S 3.30 wht cl LEGUMES 1 1 Subterranean clover /4– /2 10–20 20–30 3 2.50– 45 75 clovers, U 3.50 sub, rose

1 Sweetclovers /4–1.0 6–10 10–20 1.5 1.00– 16 32 alfalfa, U 3.00 swt cl

1 1 White clover /4– /2 3–9 5–14 1.5 1.10– 19 30 red cl, R 4.00 wht cl

1 Woollypod vetch /2–1 10–30 30–60 2-3 1.25–1.60 30 65 pea, vetch S

1Per pound in 50-lb. bags as of summer/fall 2006; To locate places to buy seed, see Seed Suppliers (p. 166). 2Mid-point price at mid-point rate, seed cost only. 3R=Reliably; U=Usually; S=Sometimes; N=Never (reseeds).

70 MANAGING COVER CROPS PROFITABLY Chart 4A POTENTIAL ADVANTAGES

Soil Impact Soil Ecology Other free loosen choke attract bears short Species subsoiler P&K topsoil nematodes disease allelopathic weeds beneficials traffic windows

Annual ryegrass p. 74

Barley p. 77

Oats p. 93

Rye p. 98

Wheat p. 111 NONLEGUMES Buckwheat p. 90

Sorghum–sudangrass p. 106

Mustards p.81

Radish p. 81

BRASSICAS Rapeseed p. 81

Berseem clover p. 118

Cowpeas p. 125

Crimson clover p. 130

Field peas p. 135

Hairy vetch p. 142

Medics p. 152

Red clover p. 159 LEGUMES Subterranean clover p. 164

Sweetclovers p. 171

White clover p. 179

Woollypod vetch p. 185

=Poor; =Fair; =Good; =Very Good; =Excellent

CHARTS 71 Chart 4B POTENTIAL DISADVANTAGES Note change in symbols = problem = not a problem Increase Pest Risks Management Challenges

Species weed insects/ crop hinder mature Comments Pro/Con potential nematodes disease crops establish till-kill mow-kill incorp. Annual ryegrass 1 If mowing, leave 3-4" to ensure regrowth. Barley Can be harder than rye to incorporate when mature. Oats Cleaned, bin-run seed will suffice. Rye Can become a weed if tilled at wrong stage.

Wheat Absorbs N and H20 heavily during

NONLEGUMES stem growth, so kill before then. Buckwheat Buckwheat sets seed quickly. Sorghum–sudangrass Mature, frost-killed plants become quite woody. Mustards Great biofumigation potential; winterkills at 25° F. Radish Winter kills at 25° F; cultivars vary widely.

BRASSICAS Rapeseed Canola has less biotoxic activity than rape. Berseem clover Multiple cuttings needed to achieve maximum N. Cowpeas Some cultivars, nematode resistant. Crimson clover Good for underseeding, easy to kill by tillage or mowing. Field peas Susceptible to sclerotinia in East. Hairy vetch Tolerates low fertility, wide pH range, cold or fluctuating winters. Medics Perennials easily become weedy. Red clover Grows best where corn grows well. LEGUMES Subterranean clover Cultivars vary greatly. Sweetclovers Hard seed possible problem; does not tolerate seeding year mowing White clover Can be invasive; survives tillage. Woollypod vetch Hard seed can be problematic; resident vegetation eventually displaces.

1Note change in symbols, this page only: = problem. = Could be a moderate problem. = Could be a minor problem. = Occasionally a minor problem. = not a problem

72 MANAGING COVER CROPS PROFITABLY OVERVIEW OF NONLEGUME COVER CROPS

Commonly used nonlegume cover crops include: ground would otherwise be left fallow (between • Annual cereals (rye, wheat, barley, oats) vegetable crops, for example). Buckwheat, while • Annual or perennial forage grasses such as not a grass, is also a warm-season plant used in the ryegrass same ways as summer-annual grasses. • Warm-season grasses like sorghum-sudangrass Nonlegume cover crops are higher in carbon • Brassicas and mustards than legume cover crops. Because of their high carbon content, grasses break down more slowly Nonlegume cover crops are most useful for: than legumes, resulting in longer-lasting residue. • Scavenging nutrients—especially N—left over As grasses mature, the carbon-to-nitrogen ratio from a previous crop (C:N) increases. This has two tangible results: • Reducing or preventing erosion The higher carbon residue is harder for soil • Producing large amounts of residue and microbes to break down, so the process takes adding organic matter to the soil longer, and the nutrients contained in the cover • Suppressing weeds crop residue usually are less available to the next crop. Annual cereal grain crops have been used suc - So although grass cover crops take up leftover cessfully in many different climates and cropping N from the previous crop, as they mature the N is systems. Winter annuals usually are seeded in late less likely to be released for use by a crop grown summer or fall, establish and produce good root imme diately after the grass cover crop. As an and topgrowth biomass before going dormant example of this, think of how long it takes for during the winter, then green up and produce sig - straw to decom pose in the field. Over time, the nificant biomass before maturing. Rye, wheat, and residue does break down and nutrients are hardy triticale all follow this pattern, with some released. In general, this slower decomposition relatively small differences that will be addressed and the higher carbon con tent of grasses can lead in the section for each cover crop. to increased soil organic matter, compared to There is growing interest in the use of brassica legumes. and mustard cover crops due to their “biofumiga- The carbon content and breakdown rate of tion” characteristics. They release biotoxic chemi- brassicas is usually intermediate to grasses and cals as they break down, and have been found to legumes, depending on maturity when terminat- reduce disease, weed and nematode pressure in ed. Brassicas and mustards can take up as much N the subsequent crop. Brassicas and mustards pro- as grass cover crops, but may release that N more vide most of the benefits of other nonlegume readily to the subsequent crop. cover crops, while some (forage radish, for exam- Nonlegume cover crops can produce a lot of ple) are thought to alleviate soil compaction. See residue, which contributes to their ability to prevent the chapter, Brassicas and Mustards (pp. 81), for ero sion and suppress weeds while they are growing more information. or when left on the soil surface as a mulch. Perennial and warm-season forage grasses also Although grasses and other nonlegumes con- can serve well as cover crops. Forage grasses, like tain some nitrogen in their plant tissues, they gen- sod crops, are excellent for nutrient scavenging, erally are not significant sources of N for your erosion control, biomass production and weed cropping sys tem. They do, however, keep excess control. Perennials used as cover crops are usual - soil N from leaching, and prevent the loss of soil ly grown for about one year. Summer-annual organic mat ter through erosion. (warm-season) grasses may fill a niche for biomass Management of nonlegumes in your cropping production and weed or erosion control if the sys tem may involve balancing the amount of

OVERVIEW OF NONLEGUME COVER CROPS 73 residue produced with the possibility of tying up In addition to grasses, another summer non- N for more than one season. Mixtures of grass and legume is buckwheat, which is described in detail legume cover crops can alleviate the N-immobi - in its own section (p. 90). Buckwheat is usually lization effect, can produce as much or more dry classed as a non-grass coarse grain. While it is man- matter as a pure grass stand and may provide bet - aged like a quick-growing grain, it has a succulent ter erosion control due to the differences in stem, large leaves and white blossoms. growth habit. Suggestions for cover crop mixtures are found in the individual cover crop sections.

ANNUAL RYEGRASS Lolium multiflorum

Also called: Italian ryegrass

Type: cool season annual grass

Roles: prevent erosion, improve soil structure and drainage, add organic matter, suppress weeds, scavenge nutrients

Mix with: legumes, grasses See charts, pp. 66 to 72, for ranking and management summary.

f you want to build soil without investing BENEFITS much in a cover crop, consider annual rye - Igrass. A quick-growing, nonspreading bunch Erosion fighter. Ryegrass has an extensive, soil- grass, annual ryegrass is a reliable, versatile per - holding root system. The cover crop estab lishes former almost anywhere, assuming adequate quickly even in poor, rocky or wet soils and toler- moisture and fertility. It does a fine job of holding ates some flooding once established. It’s well-suited soil, taking up excess N and outcompeting weeds. for field strips, grass waterways or exposed areas. Ryegrass is an excellent choice for building soil structure in orchards, vineyards and other crop - Soil builder. Ryegrass’s dense yet shallow root land to enhance water infiltration, water-holding system improves water infiltration and enhances capacity or irrigation efficiency. It can reduce soil soil tilth. Rapid aboveground growth helps splash on solanaceous crops and small fruit crops, supply organic matter. Expect about 4,000 to decreasing disease and increasing forage quality. 8,000 lb. dry matter/A on average with a multicut You also can overseed ryegrass readily into corn, regimen, climbing as high as 9,000 lb. DM/A over soybeans and many high-value crops. a full field season with high moisture and fertility.

74 MANAGING COVER CROPS PROFITABLY Weed suppressor. Mixed with legumes or grasses, annual ryegrass usually establishes first and improves early-season weed control. With adequate moisture, it serves well in Hardiness Zone 6 and warmer as a living mulch in high-value systems where you can mow it regularly. It may winterkill elsewhere, especially without pro - tective snow cover during prolonged cold snaps. Even so, its quick establishment in fall still would provide an excellent, winterkilled mulch for early- spring weed suppression.

Nutrient catch crop. A high N user, ryegrass can capture leftover N and reduce nitrate leaching

over winter. Provided it survives the winter, its Marianne Sarrantonio extensive, fibrous root system can take up as much as 43 lb. N/A, a University of California study showed (445). It took up about 60 lb. N/A ANNUAL RYEGRASS (Lolium multiflorum) by mid-May following corn in a Maryland study. Cereal rye scavenged the same amount of N by plants survive more than a year, this reseeding mid-April on this silt loam soil (372). Ryegrass characteristic can create a weed problem in some works well ahead of no-till corn or soybeans in areas, such as the mid-Atlantic or other areas with the Corn Belt, sometimes winterkilling, or spray it mild winters. In the Midwest and Southern Plains, for a weed-controlling mulch (302). it can be a serious weed problem in oat and wheat crops. It has also been shown to develop Nurse/companion crop. Ryegrass helps slow- herbicide resistance, compounding possible growing, fall-seeded legumes establish and over- weed problems (161). winter in the northern U.S., even if the ryegrass winterkills. It tends to outcompete legumes in the Establishment & Fieldwork South, although low N fertility favors the legume. Annual ryegrass germinates and establishes well Emergency forage. Ryegrass is a very palatable even in cool soil (421). Broadcast seed at 20 to 30 forage (132). You can extend the grazing period in lb./A. You needn’t incorporate seed when broad - late fall and early spring by letting livestock graze casting onto freshly cultivated soil—the first good cover crops of ryegrass or a ryegrass-based mix. shower ensures seed coverage and good germina - Annual ryegrass can be used as emergency forage if tion. Cultipacking can reduce soil heaving, how- alfalfa winterkills. It establishes quickly and pro- ever, especially with late-fall plantings. Drill 10 to 1 1 duces a lot of forage in a short amount of time. 20 lb./A, /4 to /2 inch deep. Noncertified seed will reduce seeding cost, MANAGEMENT although it can introduce weeds. Annual ryegrass also cross-pollinates with perennial ryegrass and Ryegrass prefers fertile, well-drained loam or sandy turf-type annual ryegrass species, so don’t expect loam soils, but establishes well on many soil types, a pure stand if seeding common annual ryegrass. including poor or rocky soils. It tolerates clay or poorly-drained soils in a range of climates and will Winter annual use. Seed in fall in Zone 6 or outperform small grains on wet soils (132, 421). warmer. In Zone 5 and colder, seed from mid - Annual ryegrass has a biennial tendency in cool summer to early fall—but at least 40 days before regions. If it overwinters, it will regrow quickly your area’s first killing frost (194). Late seeding and produce seed in late spring. Although few increases the probability of winterkill.

ANNUAL RYEGRASS 75 If aerially seeding, increase rates at least 30 per - Killing & Controlling cent compared to broadcast seeding rate (18). You You can kill annual ryegrass mechanically by disk - can overseed into corn at last cultivation or later ing or plowing, preferably during early bloom (consider adding 5 to 10 pounds of red or white (usually in spring), before it sets seed (361, 422). clover with it) or plant right after corn silage har- Mowing may not kill ryegrass completely (103). vest. Overseed into soybeans at leaf-yel lowing or You also can kill annual ryegrass with non - later (191, 194). When overseeding into solana- persistent contact herbicides, although some ceous crops such as peppers, tomatoes and egg- users report incomplete kill and/or resistance to plant, wait until early to full bloom. glyphosate (161, 302). To minimize N tie-up as the biomass decom - Spring seeding. Sow ryegrass right after small poses, wait a few weeks after incorporation grains or an early-spring vegetable crop, for a four- before you seed a subsequent crop. Growing rye - to eight-week summer period before a fall veg- grass with a legume such as red clover would min - etable crop (361). imize the N concern. By letting the cover residue decompose a bit, you’ll also have a seedbed that is Mixed seeding. Plant ryegrass at 8 to 15 lb./A easier to manage. with a legume or small grain, either in fall or early in spring. Ryegrass will dominate the mixture Pest Management unless you plant at low rates or mow regularly. Weed potential. Ryegrass can become a weed if The legume will compete better in low-N condi- allowed to set seed (361). It often volunteers in vine- tions. Seed the legume at about two-thirds its nor- yards or orchards if there is high fertility and may mal rate. Adequate P and K levels are important require regular mowing to reduce competi tion with when growing annual ryegrass with a legume. vines (422). A local weed management specialist In vineyards, a fall-seeded, 50:50 mix of ryegrass may be able to recommend a herbicide that can and crimson clover works well, some California reduce ryegrass germination if the cover is becoming growers have found (211). a weed in perennial grass stands. Chlorsulfuron is Although not a frequent pairing, drilling rye - sometimes used for this purpose in California (422). grass in early spring at 20 lb./A with an oats nurse crop or frost seeding 10 lb./A into over- Insect and other pests. Ryegrass attracts few wintered small grains can provide some fine fall insect pests and generally can help reduce insect grazing. Frost seeding with red clover or other pest levels in legume stands and many vegetable large-seeded, cool-season legumes also can work crops, such as root crops and brassicas. Rodents well, although the ryegrass could winterkill in are occasionally a problem when ryegrass is used some conditions. as a living mulch. Rust occasionally can be a problem with annu - Maintenance. Avoid overgrazing or mowing rye - al ryegrasses, especially crown and brown (stem) grass closer than 3 to 4 inches. A stand can persist rust. Look for resistant, regionally adapted vari- many years in orchards, vineyards, and other areas eties. Annual ryegrass also can host high densities if allowed to reseed naturally and not subject to of pin nematodes (Paratylenchus projectus) and prolonged heat, cold or drought. That’s rarely the bromegrass mosaic virus, which plant-parasitic case in Zone 5 and colder, however, where cli- nematodes (Xiphinema spp.) transmit (422). mate extremes take their toll. Perennial ryegrass may be a smarter choice if persistence is impor - Other Options tant. Otherwise, plan on incorporating the cover Ryegrass provides a good grazing option that can within a year of planting. Annual ryegrass is a rel- extend the grazing season for almost any kind of live- atively late maturing plant, so in vineyards it may stock. Although very small-seeded, ryegrass does not use excessive water and N if left too long. tiller heavily, so seed at high rates if you expect a rye-

76 MANAGING COVER CROPS PROFITABLY grass cover crop also to serve as a pas ture. Some vari- COMPARATIVE NOTES eties tolerate heat fairly well and can persist for several years under sound grazing practices that allow • Establishes faster than perennial ryegrass but the grass to reseed. As a hay option, annual ryegrass is less cold-hardy can provide 2,000 to 6,000 pounds of dry forage per • Less persistent but easier to incorporate than acre, depending on moisture and fertility levels (422). perennial ryegrass For highest quality hay, cut no later than the early • About half as expensive as perennial ryegrass bloom stage and consider growing it with a legume. • In Southern USA, annual is more adapted and When using ryegrass for grass waterways and con- produces much greater biomass servation strips on highly erodible slopes, applying 3,000 to 4,000 pounds of straw per acre after seeding Cultivars. Many varieties are widely available. at medium to high rates can help keep soil and seed Improved cultivars should be considered if grow- in place until the stand estab lishes (422). ing for forage. There are diploid (2n = 14 chromosomes) and tetraploid (4n = 28 chromosomes) Management Cautions cultivars. Tetraploids produce larger plants with Ryegrass is a heavy user of moisture and N. It per- wider leaves and mature later. forms poorly during drought or long periods of high or low temperature, and in low-fertility soils. Seed sources. See Seed Suppliers (p. 195). It can compete heavily for soil moisture when used as living mulch. It also can become a weed problem (361).

BARLEY Hordeum vulgare

Type: cool season annual cereal grain

Roles: prevent erosion, suppress weeds, scavenge excess nutrients, add organic matter

Mix with: annual legumes, ryegrass or other small grains

See charts, pp. 66 to 72, for ranking and management summary.

nexpensive and easy to grow, barley provides grains and can sop up excess subsoil moisture to exceptional erosion control and weed sup - help prevent saline seep formation (136). Ipression in semi-arid regions and in light soils. It It’s a fine choice for reclaiming overworked, weedy also can fill short rotation niches or serve as a top- or eroded fields, or as part of a cover crop mix for soil-protecting crop during droughty condi tions in improving soil tilth and nutrient cycling in perennial any region. It is more salt tolerant than other small cropping systems in Hardiness Zone 8 or warmer.

BARLEY 77 Barley prefers cool, dry growing areas. As a Tilth-improving organic matter. Barley is a spring cover crop, it can be grown farther north quick source of abundant biomass that, along with than any other cereal grain, largely because of its its thick root system, can improve soil structure short growing period. It also can produce more and water infiltration (273, 445). In California crop- biomass in a shorter time than any other cereal ping systems, cultivars such as UC476 or COSINA crop (273). can produce as much as 12,900 lb. biomass/A. Nurse crop. Barley has an upright posture and BENEFITS relatively open canopy that makes it a fine nurse crop for establishing a forage or legume stand. Erosion control. Use barley as an overwintering Less competitive than other small grains, barley cover crop for erosion control in Zone 8 and also uses less water than other covers crops. In warmer, including much of California, western weedy fields, wait to broadcast the forage or Oregon and western legume until after you’ve mechanically weeded A fast-growing Washington. It’s well- barley at the four- or five-leaf stage to reduce barley can be suited for vineyards weed competition. and orchards, or as As an inexpensive, easy-to-kill companion crop, grown farther part of a mixed seed- barley can protect sugarbeet seedlings during their ing. north and produce first two months while also serving as a soil pro- As a winter annual, tectant during droughty periods (details below). more biomass in barley develops a deep, fibrous root system. Pest suppression. Barley can reduce incidence of a shorter time The roots can reach as leafhoppers, aphids, army worms, root-knot nema- than any other deep as 6.5 feet. As a todes and other pests, a number of studies suggest. spring crop, barley has cereal grain. a compara tively shal- MANAGEMENT low root system but holds soil strongly to Establishment & Fieldwork minimize erosion during droughty conditions (71). Barley establishes readily in prepared seedbeds, and can also be successfully no-tilled. It prefers Nutrient recycler. Barley can scavenge significant adequate but not excessive moisture and does amounts of nitrogen. It captured 32 lb. N/A as a poorly in waterlogged soils. It grows best in well- winter cover crop following a stand of fava beans drained, fertile loams or light, clay soils in areas (Vicia faba) in a California study, compared with having cool, dry, mild winters. It also does well on 20 lb./A for annu al ryegrass. A barley cover crop light, droughty soils and tolerates some what alka- reduced soil N an average of 64 percent at eight line soils better than other cereal crops. sites throughout North America that had received With many varieties of barley to choose from, an average of 107 lb. N/A (265). Intercropping bar- be sure to select a regionally adapted one. Many ley with field peas (Pisum sativum) can increase are well-adapted to high altitudes and cold, short the amount of N absorbed by barley and returned growing seasons. to the soil in barley residue, other studies show (215, 218). Barley improves P and K cycling if the Spring annual use. Drill at 50 to 100 lb./A (1 to 2 3 residue isn’t removed. bushels) from /4 to 2 inches deep into a pre pared seedbed, or no-till using the same seeding rate. Weed suppressor. Quick to establish, barley out- If broadcasting, prepare the seedbed with at competes weeds largely by absorbing soil mois - least a light field cultivation. Sow 80 to 125 lb./A ture during its early growing stages. It also shades (1.5 to 2.5 bushels) and harrow, cultipack or disk out weeds and releases allelopathic chemicals lightly to cover. Use a lower rate (25 to 50 that help suppress them.

78 MANAGING COVER CROPS PROFITABLY pounds) if overseeding as a companion crop or a quickly on top of the disked higher rate (140 pounds) for very weedy fields. alleyways to set a seedbed When broadcasting, consider seeding half in one before broadcasting and direction, then the rest in a perpendicular direc - cultipacking a similar tion for better coverage (71). mix of cover crops.

Winter annual use. Barley can be used as a win- Field Management ter annual cover crop wherever it is grown as a Although barley absorbs a winter grain crop. It is less winter-hardy than rye. lot of water in its early In Zone 8 or warmer, it grows throughout the stages, it uses moisture winter if planted from September through more efficiently than other February. Plantings before November 1 generally cereals and can be grown fare best, largely due to warmer soil conditions. without irrigation in Expect mixed results if trying to use barley as a some situations. About Sears Elayne self-reseeding cover crop. half of the commercial barley acreage Mixed seedings. Barley works well in mixtures in dry land areas is with other grasses or legumes. In low-fertility soils irrigated, however. or where you’re trying to minimize tie-up of soil California crop ping nitrogen, growing barley with one or more systems that include legumes can be helpful. Your seeding cost per barley tend to be pound will increase, but the reduced seeding rate irrigated as well. can offset some of this. A short-season Canadian Low seeding rates BARLEY (Hordeum vulgare) field pea would be a good companion, or try an won’t neces sarily oat/barley/pea mix, suggests organic farmer Jack conserve moisture, as vegetative growth often Lazor, Westfield, Vt. increases. In northern California, Phil LaRocca (LaRocca LaRocca hasn’t had any moisture problems or Vineyards, Forest Ranch, Calif.) lightly disks his grape-yield concerns from growing barley or upper vineyard’s soil before broadcasting a mix other cover crops, even in the 40 percent of his of barley, fescue, brome, LANA vetch, and crim son, upper vineyard that isn’t furrow-irrigated.“Once red and subterranean clovers, usually during your vines are established, their root system is October. He seeds at 30 to 35 lb./A, with 10 to 20 deeper and much more competitive than a typical percent being barley. “I’ve always added more cover crop’s root system,” he observes. barley to the seeding rate than recom mended. Mowing can postpone and prolong barley More is better, especially with barley, if you want flowering, as with other cereal grains. As a spring biomass and weed suppression,” he says. cover, barley puts on biomass quickly, so you can After broadcasting, LaRocca covers erosion- kill it in plenty of time for seeding a following prone areas with 2 tons of rice straw per acre, crop. If you want barley to reseed, don’t mow which is “cheaper than oat straw here and has until most of the stand has headed and seed is fewer weed seeds,” he notes. “The straw decom- about to fall off. poses quickly and holds seed and soil well.” To encourage reseeding of his cover mix, Phil Besides contributing to soil humus (as the cover LaRocca allows every other row in his upper vine - crop also does), the straw helps keep the seedbed yard to go to seed, then disks it down. That lets warm and moist. That can be very helpful in him skip reseeding some blocks. LaRocca’s upper vineyard, where it sometimes If you’re concerned about barley reseeding or snows in winter. crop competition when intercropped, however, In his other, less-erodible vineyard, LaRocca plant a lighter stand, suggests Alan Brutlag, Wendell, disks up the cover vegetation, then runs a harrow Minn. During droughty conditions, he broadcasts

BARLEY 79 25 to 30 pounds of barley per acre as a soil-protec- emergence and lessen incidence of root rot disease, tive companion crop for sugarbeet seedlings. The if this has been a problem in your area (397). low-density stand is easy to stunt or kill a month Varieties resistant to leaf diseases are avail able. Two- later with the combination of herbicides and crop rowed varieties are more resistant to leaf rust and oil that he uses for weed control in his sugarbeets. mildew. Also avoid planting barley after wheat. Another control option is a single application of an If nematodes are likely to be a problem, plant herbicide labeled for grass control. late in fall or during winter to avoid warm-season growth and incorporate early in spring in Zone 8 Killing and warmer. Barley can be a host for a nematode Kill barley with a grass herbicide in late spring, or species (Meloidogyne javanica) that adversely by rolling disking or mowing at the mid- to late- affects Thompson seedless grapes. bloom stage but before it starts setting seed. Barley drastically reduced root-knot nematode If plant-parasitic nematodes have been a prob - (Meloidogyne hapla M. Chitwood) populations lem, incorporate overwintered barley early in and increased marketable carrot yields by at least spring, before warm temperatures encourage seventeen-fold in a Quebec study comparing nematode populations. three-year rotations (242).

Pest Management Other Options Annual weeds and lodging can occur when grow - Barley can be grazed lightly in winter or spring or ing barley in high-fertility soils, although these cut for hay/haylage (191). It has greater forage nutri- wouldn’t pose problems in a barley cover crop. tive value than oats, wheat or triticale. It also can be Despite their less dense canopy, six-rowed vari - grown as a specialty grain for malting, soups, bread eties tend to be taller and more competitive and other uses. As a feed grain (in a hog ration, for against weeds than two-rowed varieties. If you’re example), it can replace some costlier corn. considering a grain option, harrowing or hoeing just before barley emergence could reduce weeds COMPARATIVE NOTES that already have sprouted. Barley produces alkaloids that have been • Barley tillers more than oats and also is more shown to inhibit germination and growth of drought-tolerant, but oats generally perform white mustard (247). These exudates also protect better as a companion crop or winterkilled barley plants from fungus, armyworm larvae, bac- nurse crop because they are less competitive teria and aphids (248, 455). than barley (397). Barley seems to reduce the incidence of grape • Barley tolerates alkaline soils better than any leafhoppers in vineyards and increase levels of other cereal. beneficial spiders, one California grower • Winter cultivars are less winterhardy than observed (211). Growing high-biomass cover win ter wheat, triticale or cereal rye. crops such as barley or rye increased populations of centipedes, predator mites and other important Cultivars. Many commercial varieties are avail - predators, independent of tillage system used, a able. Look for low-cost, regionally adapted culti - study in the Pacific Northwest found (444). vars with at least 95-percent germination. Cutworms and other small grain pests can be Six-rowed cultivars are better for overseeding, and occasional problems. Some perennial crop grow - are more heat- and drought-tolerant. Two-rowed ers in California report increased incidence of types have more symmetrical kernels and are more gophers when growing cover crop mixes and try disease-resistant (e.g. leaf rust and mildew) than six- to minimize this by encouraging owl populations. rowed types, in which two-thirds of the lateral rows Avoid seeding in cold, damp soils, which makes of the spike are smaller and twisted. barley more prone to fungus and disease. Assum ing adequate soil moisture, shallow seeding can hasten Seed sources. See Seed Suppliers (p. 195).

80 MANAGING COVER CROPS PROFITABLY BRASSICAS AND MUSTARDS

Type: Annual (usually winter or spring; summer use possible)

Roles: Prevent erosion, suppress weeds and soilborne pests, alleviate soil compaction and scavenge nutrients

Mix with: Other brassicas or mustards, small grains or crimson clover

Species: Brassica napus, Brassica rapa, Brassica juncea, Brassica hirta, Raphanus sativus, Sinapsis alba Marianne Sarrantonio Marianne See charts, pp. 66 to 72, for ranking and management summary. RAPE or CANOLA (Brassica rapa)

Nomenclature Note: The cover crops Adaptation Note: This chapter addresses man- described in this chapter all belong to the agement of eight different cover crop species family BRASSICACEAE. Most but not all of the with varying degrees of winterhardiness. Some species belong to the genus Brassica. In com- can be managed as winter or spring annuals. mon usage, the various species are sometimes Others are best planted in late summer for cover lumped together as “brassicas” and sometimes crop use but will winterkill. Consult the infor- distinguished as “brassicas” vs. “mustards.” In mation on management, winterhardiness and this book, we will use brassicas as an umbrella winter vs. spring use (pp. 87-88) and the exam- term for all species; mustards will be used to ples throughout the chapter, then check with distinguish that subgroup, which has some local experts for specific adaptation information unique characteristics. for your brassica cover crop of choice.

rassica and mustard cover crops are known trapping, and biotoxic or biofumigation activity. for their rapid fall growth, great biomass Some brassicas have a large taproot that can break Bproduction and nutrient scavenging ability. through plow pans better than the fibrous roots of However, they are attracting renewed interest pri- cereal cover crops or the mustards. Those brassicas marily because of their pest management charac- that winterkill decompose very quickly and leave a teristics. Most Brassica species release chemical seedbed that is mellow and easy to plant in. compounds that may be toxic to soil borne With a number of different species to consider, pathogens and pests, such as nematodes, fungi you will likely find one or more that can fit your and some weeds. The mustards usually have farming system. Don’t expect brassicas to elimi- higher concentrations of these chemicals. nate your pest problems, however. They are a Brassicas are increasingly used as winter or rota- good tool and an excellent rotation crop, but pest tional cover crops in vegetable and specialty crop management results are inconsistent. More production, such as potatoes and tree fruits. There is research is needed to further clarify the variables also growing interest in their use in row crop pro- affecting the release and toxicity of the chemical duction, primarily for nutrient capture, nematode compounds involved (see p. 82).

BRASSICAS AND MUSTARDS 81 BENEFITS commercial fumigants (388). It varies depending on species, planting date, growth stage when Erosion control and nutrient scavenging. killed, climate and tillage system. Be sure to con- Brassicas can provide greater than 80% soil cover- sult local expertise for best results. age when used as a winter cover crop (176). Depending on location, planting date and soil fer- ▼ Precaution. The use of brassicas for pest man- tility, they produce up to 8,000 lb. biomass/A. agement is in its infancy. Results are inconsistent Because of their fast fall growth, brassicas are well- from year to year and in different geographic suited to capture soil nitrogen (N) remaining after regions. Different species and varieties contain crop harvest. The amount of nitrogen captured is different amounts of bioactive chemicals. Be sure mainly related to biomass accumulation and the to consult local expertise and begin with small amount of N available in the soil profile. test plots on your farm. Because they immobilize less nitrogen than some cereal cover crops, much of the N taken up Disease can become available for uptake by main crops in In Washington, a SARE-funded study of brassica early to late spring (see also Building Soil Fertility green manures in potato cropping systems com- and Tilth with Cover pared winter rape (Brassica napus) and white Brassicas must Crops, pp. 16–24). mustard (Sinapis alba) to no green manure, with Brassicas can root to and without herbicides and fungicides. The win- be planted earlier depths of six feet or ter rape system had a greater proportion of than winter cereal more, scavenging nutri- Rhizoctonia-free tubers (64%) than the white ents from below the mustard (27%) and no green manure (28%) treat- cover crops in rooting depth of most ments in the non-fumigated plots. There was less crops. To maximize bio- Verticillium wilt incidence with winter rape most regions. mass production and incorporation (7%) than with white mustard nutrient scavenging in (21%) or no green manure incorporation (22%) in the fall, brassicas must non-fumigated plots (88). be planted earlier than winter cereal cover crops In Maine, researchers have documented consis- in most regions, making them more difficult to fit tent reductions in Rhizoctonia (canker and black into grain production rotations. scurf) on potato following either rapeseed green manure or canola grown for grain (459, 460). Pest management.All brassicas have been shown They have also observed significant reductions in to release bio-toxic compounds or metabolic by- powdery scab (caused by Spongospora subter- products that exhibit broad activity against bacte- ranea) and common scab (Streptomyces scabiei) ria, fungi, insects, nematodes, and weeds. Brassica following brassica green manures, especially an cover crops are often mowed and incorporated to Indian mustard (B. juncea) green manure (458, 459). maximize their natural fumigant potential. This is because the fumigant chemicals are produced only Nematodes when individual plant cells are ruptured. In Washington state, a series of studies addressed Pest suppression is believed to be the result of the effect of various brassica and mustard cover glucosinolate degradation into biologically active crops on nematodes in potato systems (260, 266, sulfur containing compounds call thiocyanates 353, 283, 284, 285). (152, 320). To maximize pest suppression, incor- The Columbia root-knot nematode (Meloi - poration should occur during vulnerable life- dogyne chitwoodi) is a major pest in the Pacific stages of the pest (446). Northwest. It is usually treated with soil fumigants The biotoxic activity of brassica and mustard costing $20 million in Washington alone. cover crops is low compared to the activity of

82 MANAGING COVER CROPS PROFITABLY Rapeseed, arugula and mustard were studied as ed to the sugar beet cyst nematode). The same alternatives to fumigation. The brassica cover species, when grown with rye or clover, did crops are usually planted in late summer (August) reduce incidence of stubby root nematode (432). or early fall and incorporated in spring before Also in Maryland, in no-till corn on a sandy soil, planting mustard. winterkilled forage radish increased bacteria-eat- Results are promising, with nematodes reduced ing nematodes, rye and rapeseed increased the up to 80%, but—because of the very low damage proportion of fungal feeding nematodes, while threshold—green manures alone cannot be rec- nematode communities without cover crops ommended for adequate control of Meloidogyne were intermediate. The Enrichment Index, which chitwoodi in potatoes. The current recommend- indicates a greater abundance of opportunistic ed alternative to fumigation is the use of rapeseed bacteria–eating nematodes, was 23% higher in or mustard cover crop plus the application of soils that had brassica cover crops than the MOCAP. This regimen costs about the same as unweeded control plots. fumigation (2006 prices). These samples, taken in November, June (a Several brassicas are hosts for plant parasitic month after spring cover crop kill), and August nematodes and can be used as trap crops followed (under no-till corn), suggest that the cover crops, by an application of a synthetic nematicide. living or dead, increased bacterial activity and may Washington State University nematologist Ekaterini have enhanced nitrogen cycling through the food Riga has been planting arugula in the end of August web (432). and incorporating it in the end of October. Nematicides are applied two weeks after incor- Weeds poration, either at a reduced rate using Telone or Like most green manures, brassica cover crops the full rate of Mocap and Temik. Two years of suppress weeds in the fall with their rapid growth field trials have shown that arugula in combina- and canopy closure. In spring, brassica residues tion with synthetic nematicides reduced M. chit- can inhibit small seeded annual weeds such as, woodi to economic thresholds. pigweed, shepherds purse, green foxtail, kochia, Longer crop rotations that include mustards hairy nightshade, puncturevine, longspine sand- and non-host crops are also effective for nema- bur, and barnyardgrass (293), although pigweed tode management. For example, a 3-year rotation was not inhibited by yellow mustard (178). of potatoes>corn>wheat provides nearly com- In most cases, early season weed suppression plete control of the northern root-knot nematode obtained with brassica cover crops must be sup- (Meloidogyne hapla) compared to methyl bro- plemented with herbicides or cultivation to avoid mide and other broad-spectrum nematicides. crop yield losses from weed competition later in However, because the rotation crops are less prof- the season. As a component of integrated weed itable than potatoes, they are less commonly used. management, using brassica cover crops in veg- Not until growers better appreciate the less tangible etable rotations could improve weed control and long-term cover crop benefits of soil improvement, reduce reliance on herbicides (39). nutrient management and pest suppression will In Maine, the density of sixteen weed and crop such practices be more widely adopted. species was reduced 23 to 34% following incorpo- In Wyoming, oilseed radish (Raphanus sativus) ration of brassica green manures, and weed estab- and yellow mustard (Sinapsis alba) reduced the lishment was delayed by 2 days, compared to a sugar beet cyst nematode populations by 19-75%, fallow treatment. However, other short-season green with greater suppression related to greater manure crops including oat, crimson clover and amount of cover crop biomass (231). buckwheat similarly affected establishment (176). In Maryland, rapeseed, forage radish and a mus- In Maryland and Pennsylvania, forage radish is tard blend did not significantly reduce incidence planted in late August and dies with the first hard of soybean cyst nematode (which is closely relat- frost (usually December). The living cover crop

BRASSICAS AND MUSTARDS 83 and the decomposing residues suppress winter rapeseed cultivars belong to the species B. rapa. annual weeds until April and result in a mellow, Rapeseed is used as industrial oil while canola is weed-free seedbed into which corn can be no- used for a wider range of products including tilled without any preplant herbicides. Preliminary cooking oils and biodiesel. data show summer suppression of horseweed but Besides their use as an oil crop, these species not lambsquarters, pigweed, or green foxtail (432). are also used for forage. If pest suppression is an Mustard cover crops have been extremely effec- objective, rapeseed should be used rather than tive at suppressing winter weeds in tillage inten- canola since the breakdown products of glucosi- sive, high value vegetable production systems in nolates are thought to be a principal mechanism Salinas, California. Mustards work well in tillage for pest control with these cover crops. intensive systems because they are relatively easy Rapeseed has been shown to have biological to incorporate into the soil prior to planting veg- activity against plant parasitic nematodes as well etables. However, the growth and biomass pro- as weeds (176, 365). duction by mustards in the winter is not usually as Due to its rapid fall growth, rapeseed captured reliable as that of other cover crops such as cereal as much as 120 lb. of residual nitrogen per acre in rye and legume/cereal mixtures (45). Maryland (6). In Oregon, aboveground biomass accumulation reached 6,000 lb./A and N accumu- Deep tillage. Some brassicas (forage radish, rape- lation was 80 lb./A. seed, turnip) produce large taproots that can pene- Some winter-type cultivars are able to withstand trate up to six feet to alleviate soil compaction quite low temperatures (10° F) (352). This makes (432). This so-called “biodrilling” is most effective rapeseed one of the most versatile cruciferous cover when the plants are growing at a time of year crops, because it can be used either as a spring- or when the soil is moist and easier to penetrate. summer-seeded cover crop or a fall-seeded winter Their deep rooting also allows these crops to cover crop. Rapeseed grows 3 to 5 feet tall. scavenge nutrients from deep in the soil profile. As the large tap roots decompose, they leave Mustard. Mustard is a name that is applied to channels open to the surface that increase water many different botanical species, including white infiltration and improve the subsequent growth or yellow mustard (Sinapis alba, sometimes and soil penetration of crop roots. Smaller roots referred to as Brassica hirta), brown or Indian decompose and leave channels through the plow mustard (Brassica juncea)—sometimes erro- plan and improve the soil penetration by the neously referred to as canola—and black mustard roots of subsequent crops (446). (B. nigra (L.) (231). Most mustards have a fibrous root system, and The glucosinolate content of most mustards is rooting effects are similar to small grain cover very high compared to the true Brassicas. crops in that they do not root so deeply but devel- In the Salinas Valley, California, mustard biomass op a large root mass more confined to the soil reached 8,500 lb./A. Nitrogen content on high surface profile. residual N vegetable ground reached 328 lb. N/A (388, 422). SPECIES Because mustards are sensitive to freezing, winterkilling at about 25º F, they are used either as a Rapeseed (or Canola). Two Brassica species are spring/summer crop or they winter kill except in commonly grown as rapeseed, Brassica napus and areas with little freeze danger. Brown and field Brassica rapa. Rapeseed that has been bred to mustard both can grow to 6 feet tall. have low concentrations of both erucic acid and In Washington, a wheat/mustard-potato system glucosinolates in the seed is called canola, which is shows promise for reducing or eliminating the a word derived from Canadian Oil. soil fumigant metam sodium. White mustard and Annual or spring type rapeseed belongs to the oriental mustard both suppressed potato early species B. napus, whereas winter-type or biennial dying (Verticillium dahliae) and resulted in tuber

84 MANAGING COVER CROPS PROFITABLY yields equivalent to fumigated soils, while also sis group), chinese cabbage (pekinensis group) improving infiltration, all at a cost savings of and turnip (rapa group). Varieties of Brassica about $66/acre (see www.plantmanagementnet napus include Canadian turnip, kale, rutabaga, work.org/pub/cm/research/2003/mustard/). rape, swede, swedish turnip and yellow turnip. Mustards have also been shown to suppress Collard, another vegetable, is a cabbage, B. oler- growth of weeds (See “Weeds” p. 99 and 39, 176, acea var. acephala, and B. juncea is consumed as 365). mustard greens. A grower in Maryland reported harvesting the Radish. The true radish or forage radish larger roots of forage radish (cultivar DAIKON) (Raphanus sativus) does not exist in the wild cover crop to sell as a vegetable. In California, and has only been known as a cultivated species broccoli reduced the incidence of lettuce drop since ancient times. Cultivars developed for high caused by Sclerotinia minor (175). forage biomass or high oilseed yield are also useful for cover crop purposes. Common types AGRONOMIC SYSTEMS include oilseed and forage radish. Their rapid fall growth has the potential to cap- Brassicas must be planted earlier than small grain ture nitrogen in large amounts and from deep in cover crops for maximum benefits, making it dif- the soil profile (170 lb./acre in Maryland (234). ficult to integrate them into cash grain rotations. Above ground dry biomass accumulation reached Broadcasting seeding (including aerial seed- 8,000 lb./acre and N accumulation reached 140 ing) into standing crops of corn or soybean has lb./acre in Michigan (304). Below ground biomass been successful in some regions (235). See also of radishes can be as high as 3,700 lb./acre. After 25 Years, Improvements Keep Coming, Oilseed radish is less affected by frost than for- (p. 52). Brassica growth does not normally inter- age radish, but may be killed by heavy frost below fere with soybean harvest, although could be a 25° F. Radish grows about 2–3 feet tall. problem if soybean harvest is delayed. The shad- Radishes have been shown to alleviate soil ing by the crop canopy results in less cover crop compaction and suppress weeds (177, 446). biomass and especially less root growth, so this option is not recommended where the Turnips. Turnips (B. rapa L. var. rapa (L.) Thell) brassica cover crop is intended for compaction are used for human and animal food because of alleviation. their edible root. Turnip has been shown to In a Maryland SARE-funded project, dairy alleviate soil compaction. While they usually do farmers planted forage radish immediately after not produce as much biomass as other brassicas, corn silage harvest. With a good stand of forage they provide many macrochannels that facilitate radish, which winterkills, corn can be planted water infiltration (359). Similar to radish, turnip is in early spring without tillage or herbicides, unaffected by early frost but will likely be killed resulting in considerable savings. The N released by temperatures below 25° F. by the decomposed forage radish residues In an Alabama study of 50 cultivars belonging to increased corn yield boost in most years. the genera Brassica, Raphanus, and Sinapis, forage This practice is particularly useful when and oilseed radish cultivars produced the largest manure is fall-applied to corn silage fields. (For amount of biomass in central and south Alabama, more information visit http://www.sare.org/pro- whereas winter-type rapeseed cultivars had the jects and search for project report LNE03-192). highest production in North Alabama (425). ▼ Precaution: Brassica cover crops may be sus- Some brassicas are also used as vegetables ceptible to carry-over from broadleaf herbicides (greens). Cultivated varieties of Brassica rapa applied to the previous grain crop. include bok choy (chinensis group), mizuna (nip- posinica group), flowering cabbage (parachinen-

BRASSICAS AND MUSTARDS 85 Mustard Mix Manages Nematodes in Potato/Wheat System

Looking for a green manure crop to maintain control early dying disease (Verticillium soil quality in his intensive potato/wheat dahliae), that cost that up to $500 per acre. rotation, Dale Gies not only improved Farmers are especially vulnerable to early infiltration and irrigation efficiency, he also dying disease if their rotations contain fewer found biofumigation, a new concept in pest than three years between potato crops. management. However, with potato prices dropping, Farming 750 irrigated acres with two sons potato farmers in Washington and elsewhere and a son-in-law in the Columbia basin of Grant started looking for ways to reduce costs. Gies County, Wash., Gies started growing green contacted Andy McGuire at Washington State manure crops in 1990 because he wanted to University Extension for help documenting improve his soils for future generations. Since the results he was seeing with brassicas. then, he has reduced his use of soil fumigants With research funding from SARE, McGuire thanks to the biocidal properties of Brassica confirmed that the mustards improved cover crops. In particular, Gies is most excited infiltration. He also showed that white about results using a mixture of white or mustard was as effective as metam sodium oriental mustard and arugula (Eruca sativa), in controlling potato early dying disease. also a brassica, to manage nematodes and “The findings suggest that mustard green potato early dying disease. manures may be a viable alternative to the “We use the mustards to augment other fumigant metam sodium in some potato good management practices,” Gies cautions. cropping systems,” says McGuire. “The practice “Don’t expect a silver bullet that will solve can also improve water infiltration rates and your pest problems with one use.” provide substantial savings to farmers. Until Controlling nematodes is essential to more research is done, however, mustard quality potato production, both for the cover crops should be used to enhance, not domestic and the international market. eliminate, chemical control of nematodes.” Farmers typically manage root knot Researchers have found that mustards can nematodes (Meloidogyne chitwoodi) and also suppress common root rot (Aphano - fungal diseases with pesticides, such as myces euteiches) and the northern root-knot Metam sodium, a fumigant used routinely to nematode (Meloidogyne hapla).

Vegetable Systems. Fall-planted brassica cover Winter-killed forage radish leaves a nearly crops fit well into vegetable cropping systems fol- weed- and residue-free seedbed, excellent for lowing early harvested crops. White mustard and early spring “no-till” seeding of crops such as car- brown mustard have become popular fall-planted rots, lettuce, peas and sweet corn. This approach cover crops in the potato producing regions of can save several tillage passes or herbicide appli- the Columbia Basin of eastern Washington. cations for weed control in early spring and can Planted in mid to late August, white mustard take advantage of the early nitrogen release by the emerges quickly and produces a large amount of forage radish. Soils warm up faster than under biomass before succumbing to freezing tempera- heavy residue, and because no seedbed prepara- tures. As a component of integrated weed man- tion or weed control is needed, the cash crop can agement, using brassica cover crops in vegetable be seeded earlier than normal. rotations could improve weed control and reduce reliance on herbicides (39).

86 MANAGING COVER CROPS PROFITABLY Two types of mustard commonly used in “Arugula acts both as a green manure and a the Columbia Basin are white mustard nematode trap crop,” says Riga. (Sinapis alba, also called Brassica hirta or “It contains chemicals with high biocidal yellow mustard), and Oriental mustard activity that mimic synthetic fumigants. Since (Brassica juncea, also called Indian or brown nematodes are attracted to the roots of mustard). Blends of the two are often planted Arugula, it can be managed as a trap crop.” as green manures. Fall incorporation seems to What causes brassicas to have biocidal be best to control nematodes and soil-borne properties? Researchers are keying in on the diseases, and Oriental mustard may be better presence of glucosinolates in mustards. When at it than white mustard. the crop is incorporated into the soil, the Gies plants a mix of mustards and NEMAT, breakdown of glucosinolates produces other an arugula variety developed in Italy for chemicals that act against pests. Those nematode suppression. The arugula attracts secondary chemicals behave like the active nematodes but they cannot reproduce on its chemical in commercial fumigants like metam roots, so nematode populations reduce, sodium. according to Washington State University More research is needed to better researcher Ekaterini Riga. determine site- and species-specific brassica Riga’s greenhouse studies showed that cover crop effects on pests. It seems to be arugula reduced Columbia root knot working for Dale Gies, however, “whose short nematode (Meloidogyne chitwoodi) season fresh market potato system probably populations compared to the control or other functions differently than processing potatoes” green manure treatments. Subsequent field according to WSU’s Andy McGuire. To stay trial in 2005 and 2006 showed that arugula in updated on cover crop work in Washington combination with half the recommended rate State, see www.grant-adams.wsu.edu/ of Telone (another fumigant) or full rates of agriculture/ covercrops/green_manures/. Mocap and Temik reduced root knot For Gies, however, “Tying the whole system nematode populations from 700 nematodes together makes it work economically, and it per gram of soil to zero. The combination also improves the soil.” improved potato yield and tuber quality and it —Andy Clark is still affordable for the growers.

MANAGEMENT Winter hardiness Some brassicas and most mustards may winterkill, Establishment depending on climate and species. Forage radish Most Brassica species grow best on well drained normally winter kills when air temperatures drop soils with a pH range of 5.5–8.5. Brassicas do not below 23° F for several nights in a row. Winter har- grow well on poorly drained soils, especially during diness is higher for most brassicas if plants reach establishment. Winter cover crops should be estab- a rosette stage between six to eight leaves before lished as early as possible. A good rule of thumb the first killing frost. is to establish brassicas about 4 weeks prior to the Some winter-type cultivars of rapeseed are average date of the first 28° F freeze. The minimum able to withstand quite low temperatures (10° F) soil temperature for planting is 45° F; the maximum (352). is 85° F.

BRASSICAS AND MUSTARDS 87 Late planting will likely result in stand failure region to produce high biomass for incorporation and will certainly reduce biomass production and to biofumigate soil for nematodes and diseases nutrient scavenging. Planting too early, however, prior to planting strawberries and fruit trees. may increase winterkill in northern zones (166). In Washington (Zone 6), canola and rapeseed Mixtures. Mix with small grains (oats, rye), other usually overwinter, mustards do not. Recent work brassicas or legumes (e.g. clover). Brassicas are very with arugula (Eruca sativa) shows that it does competitive and can overwhelm the other species overwinter and may provide similar benefits as in the mixture. The seeding rate must be adjusted the mustards (430). so ensure adequate growth of the companion In Michigan, mustards are planted in mid- species. Consult local expertise and start with small August, and winterkill with the first hard frost, plots or experiment with several seeding rates. usually in October. When possible, plant another Washington farmers use mixtures of white and winter cover crop such as rye or leave strips of brown mustard, usually with a greater proportion untilled brassica cover crop rather than leave the of brown mustard. soil without growing cover over the winter (391). In Maryland and Pennsylvania, farmers and In Maine, all brassica and mustards used as researchers seed the small grain and forage radish cover crops winterkill (166). in separate drill rows rather than mixing the seed. This is done by taping closed alternate holes in Winter vs. spring annual use the two seeding boxes of a grain drill with both Brassica and mustard cover crops can be planted small seed and large seed boxes. Two rows of oats in spring or fall. Some species can be managed to between each row of forage radish has also winterkill, leaving a mellow seedbed requiring lit- proven successful (432). Rye (sown at 48 lb./A) tle or no seedbed preparation. For the maximum can be grown successfully as a mixture with win- benefits offered by brassicas as cover crops, fall- ter-killing forage radish (13 lb./A). planting is usually preferable because planting conditions (soil temperature and moisture) are Killing more reliable and the cover crops produce more Brassica cover crops that do not winterkill can dry matter. be terminated in spring by spraying with an In Maryland, rapeseed and forage radish were appropriate herbicide, mowing, and/or incorpo- more successful as winter- rather than spring- rating above-ground biomass by tillage before annual cover crops. The early spring planted bras- the cover crop has reached full flower. Rolling sicas achieved about half the quantities of may also be used to kill these covers if they are biomass and did not root as deeply, before bolting in flower. in spring (432). Rapeseed has proved difficult to kill with In Michigan, mustards can be planted in spring glyphosate, requiring a higher than normal rate of following corn or potatoes or in fall into wheat application—at least 1 quart/acre of glyphosate— residue or after snap beans. Fall seedings need and possibly multiple applications. Radish, mus- about 900 growing-degree-days to produce tard, and turnip can be killed using a full rate of acceptable biomass, which is usually incorporated paraquat, multiple applications of glyphosate, or at first frost (usually October). Spring seeding is glyphosate plus 1pt/acre 2,4-D. less reliable due to cool soil temperatures, and its In Alabama and Georgia, brassica cover crops use is limited mostly to late-planted vegetable were reportedly harder to chemically kill than crops (391). winter cereals. Timely management and multiple In Maine, brassicas are either planted in late herbicide applications may be necessary for suc- summer after the cash crop and winterkill, or they cessful termination. If not completely killed, rape- are spring-seeded for a summer cover crop (166). seed volunteers can be a problem in the Rapeseed planted in late spring to summer has subsequent crop. Always check herbicide rota- been used with some success in the mid-Atlantic tion restrictions before applying.

88 MANAGING COVER CROPS PROFITABLY Another no-till method for terminating mature that of winter rye. A winter-killed radish cover brassicas is flail mowing. Be sure to evenly dis- crop releases plant available nitrogen especially tribute residue to facilitate planting operations early in spring, so it should be followed by an and reduce allelopathic risk for cash crop. As early planted nitrogen demanding crop to avoid mentioned above, many producers incorporate leaching losses (432). brassica residues using conventional tillage methods to enhance soil biotoxic activity especially in COMPARATIVE NOTES plasticulture systems. Brassica pest suppression may be more effec- Canola is more prone to insect problems than tive if the cover crop is incorporated. mustards, probably because of its lower concentration of glucosinolates. Seed and Planting In the Salinas Valley, which has much milder Because Brassica spp. seed may be scarce, it is summer and winter temperatures than the best to call seed suppliers a few months prior to Central Valley of California, brassica cover crops planting to check on availability. Brassica seeds in are generally less tolerant of suboptimal condi- general are relatively small; a small volume of seed tions (i.e. abnormally low winter temperatures, goes a long way. low soil nitrogen, and waterlogging), and hence • Rapeseed (Canola). Drill 5-10 lb./A no deeper are more likely to produce a nonuniform stand than ¾ in. or broadcast 8–14 lb./A. than other common cover crops (45). • Mustard. Drill 5-12 lb./A ¼–¾ in. deep or broadcast 10-15 lb./A. ▼ Precautions. The use of brassicas for pest • Radish. Drill 8 to 12 lb/A.¼–½ in. deep, or management is in its infancy. Results are inconsis- broadcast 12-20 lb./A. Plant in late summer or tent from year to year and in different geographic early fall after the daytime average tempera- regions. Be sure to consult local expertise and ture is below 80° F. begin with small test plots on your farm. • Turnip. Drill 4-7 lb./A about ½ in. deep or Bio-toxic activity can stunt cash crop growth, broadcast 10-12 lb./A. Plant in the fall after the thus avoid direct planting into just-killed green daytime average temperature is below 80° F. residue. Brassica cover crops should NOT be planted in Nutrient Management rotation with other brassica crops such as cab- Brassicas and mustards need adequate nitrogen bage, broccoli, and radish because the latter are and sulfur fertility. Brassica sulfur (S) nutrition susceptible to similar diseases. Also, scattered needs and S uptake capacity exceed those of volunteer brassica may appear in subsequent many other plant species, because S is required crops. Controlling brassica cover crop volunteers for oil and glucosinolate production. A 7:1 N/S that come up in brassica cash crops would be ratio in soils is optimum for growing rape, while challenging if not impossible. N/S ratios ranging from 4:1 to 8:1 work well for Black mustard (Brassica nigra) is hardseeded brassica species in general. and could cause weed problems in subsequent Ensuring sufficient N supply to brassicas during crops (39). establishment will enhance their N uptake and Rapeseed contains erucic acid and glucosino- early growth. Some brassicas, notably rape, can lates, naturally occurring internal toxicants. These scavenge P by making insoluble P more available compounds are anti-nutritional and are a concern to them via the excretion of organic acids in their when feeding to livestock. Human consumption root zone (168). of brassicas has been linked to reducing inci- Brassicas decompose quickly. Decomposition dence of cancer. All canola cultivars have been and nutrient turnover from roots (C:N ratios 20- improved through plant breeding to contain less 30) is expected to be slower than that from than 2% erucic acid. shoots (C:N ratios 10-20), but overall faster than

BRASSICAS AND MUSTARDS 89 Winter rape is a host for root lesion nematode. go to www.sare.org/projects/ and search for In a SARE funded study in Washington, root lesion SW95-021. See also SW02-037. nematode populations were 3.8 times higher in Rapeseed may provide overwintering sites for the winter rape treatment than in the white mus- harlequin bug in Maryland (432). tard and no green manure treatments after green manure incorporation in unfumigated plots. Contributors: Guihua Chen, Andy Clark, However, populations in the unfumigated winter Amy Kremen, Yvonne Lawley, Andrew Price, rape treatment were below the economic thresh- Lisa Stocking, Ray Weil old both years of the study. For more information,

BUCKWHEAT Fagopyrum esculentum

Type: summer or cool-season annual broadleaf grain

Roles: quick soil cover, weed suppressor, nectar for pollinators and beneficial insects, topsoil loosener, rejuvenator for low-fertility soils

Mix with: sorghum-sudangrass hybrids, sunn hemp

See charts, pp. 66 to 72, for ranking and management summary.

uckwheat is the speedy short-season BENEFITS cover crop. It establishes, blooms and Breaches maturity in just 70 to 90 days and Quick cover. Few cover crops establish as rapid - its residue breaks down quickly. Buckwheat sup - ly and as easily as buckwheat. Its rounded pyra - presses weeds and attracts beneficial insects and mid-shaped seeds germinate in just three to five pollinators with its abundant blossoms. It is easy days. Leaves up to 3 inches wide can develop to kill, and reportedly extracts soil phosphorus within two weeks to create a relatively dense, soil from soil better than most grain-type cover shading canopy. Buckwheat typically produces crops. only 2 to 3 tons of dry matter per acre, but it does Buckwheat thrives in cool, moist conditions so quick ly—in just six to eight weeks (257). but it is not frost tolerant. Even in the South, it is Buckwheat residue also decomposes quickly, not grown as a winter annual. Buckwheat is not releasing nutrients to the next crop. particularly drought tolerant, and readily wilts under hot, dry conditions. Its short growing sea - Weed suppressor. Buckwheat’s strong weed- son may allow it to avoid droughts, however. suppressing ability makes it ideal for smothering

90 MANAGING COVER CROPS PROFITABLY warm-season annual weeds. It’s also planted after intensive, weed-weakening tillage to crowd out perennials. A mix of tillage and successive dense seedings of buckwheat can effectively suppress Canada thistle, sowthistle, creeping jenny, leafy spurge, Russian knapweed and perennial pepper - grass (257). While living buckwheat may have an allelopathic weed-suppressing effect (351), its pri - mary impact on weeds is through shading and competition.

Phosphorus scavenger. Buckwheat takes up phosphorus and some minor nutrients (possibly including calcium) that are otherwise unavailable to crops, then releasing these nutrients to later crops as the residue breaks down. The roots of the plants produce mild acids that release nutri- Sarrantonio Marianne ents from the soil. These acids also activate BUCKWHEAT (Fagopyrum esculentum) slow-releasing organic fertilizers, such as rock phos phate. Buckwheat’s dense, fibrous roots clus- sitize aphids, mites and other pests. These benefi - ter in the top 10 inches of soil, providing an exten- cials include hover flies (Syrphidae), predatory sive root surface area for nutrient uptake. wasps, minute pirate bugs, insidious flower bugs, tachinid flies and lady beetles. Flowering may Thrives in poor soils. Buckwheat performs start within three weeks of planting and continue bet ter than cereal grains on low-fertility soils and for up to 10 weeks. soils with high levels of decaying organic matter. Nurse crop. Due to its quick, aggressive start, That’s why it was often the first crop planted on buckwheat is rarely used as a nurse crop, cleared land during the settlement of woodland although it can be used anytime you want quick areas and is still a good first crop for rejuvenating cover. It is sometimes used to pro tect late-fall over-farmed soils. However, buckwheat does not plantings of slow-starting, winter-hardy legumes do well in compacted, droughty or excessively wherever freezing temperatures are sure to kill wet soils. the buckwheat.

Quick regrowth. Buckwheat will regrow after MANAGEMENT mowing if cut before it reaches 25 percent bloom. It also can be lightly tilled after the Buckwheat prefers light to medium, well-drained mid point of its long flowering period to reseed a soils—sandy loams, loams, and silt loams. It per - sec ond crop. Some growers bring new land into forms poorly on heavy, wet soils or soils with high production by raising three successive buck - levels of limestone. Buckwheat grows best in wheat crops this way. cool, moist conditions, but is not frost-tolerant. It is also not drought tolerant. Extreme afternoon Soil conditioner. Buckwheat’s abundant, fine heat will cause wilting, but plants bounce back roots leave topsoil loose and friable after only min - overnight. imal tillage, making it a great mid-summer soil con - ditioner preceding fall crops in temperate areas. Establishment Plant buckwheat after all danger of frost. In Nectar source. Buckwheat’s shallow white blos - untilled, minimally tilled or clean-tilled soils, drill 1 1 soms attract beneficial insects that attack or para - 50 to 60 lb./A at /2 to 1 /2 inches deep in 6 to 8

BUCKWHEAT 91 inch rows. Use heavier rates for quicker canopy Buckwheat is sensitive to herbicide residues development. For a fast smother crop, broadcast from previous crops, especially in no-till up to 96 lb./A (2 bu./A) onto a firm seedbed and seedbeds. Residue from trifluralin and from tri - incor porate with a harrow, tine weeder, disk or azine and sulfonylurea herbicides have damaged field cultivator. Overall vigor is usually better in or killed buckwheat seedlings (79). When in drilled seedings. As a nurse-crop for slow- doubt, sow and water a small test plot of the fast- grow ing, winter annual germinating seed to detect stunting or mortality. Buckwheat legumes planted in late germinates and sum mer or fall, seed at Pest Management one-quarter to one-third Few pests or diseases bother buckwheat. Its most grows quickly, of the normal rate. serious weed competitors are often small grains Buckwheat compen- from preceding crops, which only add to the producing 2 to 3 sates for lower seeding cover crop biomass. Other grass weeds can be a tons of dry rates by developing problem, especially in thin stands. Weeds also can more branches per plant increase after seed set and leaf drop. Diseases matter in just and more seeds per blos- include a leaf spot caused by the fungus som. However, skimping Ramularia and Rhizoctonia root rot. 6 to 8 weeks. too much on seed makes stands more vul- Other Options nerable to early weed Plant buckwheat as an emergency cover crop to competition until the canopy fills in. Using protect soil and suppress weeds when your main cleaned, bin-run or even birdseed-grade seed can crop fails or cannot be planted in time due to lower establishment costs, but increas es the risk unfavorable conditions. of weeds. As denser stands mature, stalks become To assure its role as habitat for beneficial spindly and are more likely to lodge from wind or insects, allow buckwheat to flower for at least 20 heavy rain. days—the time needed for minute pirate bugs to produce another generation. Rotations Buckwheat can be double cropped for grain Buckwheat is used most commonly as a mid-sum - after harvesting early crops if planted by mid-July mer cover crop to suppress weeds and replace in northern states or by early August in the South. bare fallow. In the Northeast and Midwest, it is It requires a two-month period of relatively cool, often planted after harvest of early vegetable crops, moist conditions to prevent blasting of the blos - then followed by a fall vegetable, winter grain, or soms. There is modest demand for organic and cool-season cover crop. Planted later, winterkilled specially raised food-grade buckwheat in domes- residue provides decent soil cover and is easy to tic and overseas markets. Exporters usually no-till into. In many areas, it can be planted fol- specify variety, so investigate before planting lowing harvest of winter wheat or canola. buckwheat for grain. In parts of California, buckwheat grows and flowers between the killing of winter annual Management Cautions legume cover crops in spring and their re-estab- Buck wheat can become a weed. Kill within 7 to 10 lishment in fall. Some California vineyard man- days after flowering begins, before the first seeds agers seed 3-foot strips of buck wheat in row begin to harden and turn brown. Earliest maturing middles, alternating it and another summer cover seed can shatter before plants finish blooming. crop, such as sorghum-sudangrass. Some seed may overwin ter in milder regions. Buckwheat can harbor insect pests including Lygus bugs, tarnished plant bugs and Pratylynchus penetrans root lesion nematodes (256).

92 MANAGING COVER CROPS PROFITABLY COMPARATIVE NOTES • Buckwheat is nearly three times as effective as barley in extracting phosphorus, and more • Buckwheat has only about half the root mass than 10 times more effective than rye—the as a percent of total biomass as small grains poorest P scavenger of the cereal grains (355). (355). Its succulent stems break down quickly, • As a cash crop, buckwheat uses only half as leaving soils loose and vulnerable to erosion, much soil moisture as soybeans (299). particularly after tillage. Plant a soil-holding crop as soon as possible. Seed sources. See Seed Suppliers (p. 195).

OATS Avena sativa

Also called: spring oats

Type: cool season annual cereal

Roles: suppress weeds, prevent erosion, scavenge excess nutrients, add biomass, nurse crop

Mix with: clover, pea, vetch, other legumes or other small grains

See charts, pp. 66 to 72, for ranking and management summary.

f you need a low-cost, reliable fall cover that win- BENEFITS terkills in Hardiness Zone 6 and colder and much Iof Zone 7, look no further. Oats provide quick, You can depend on oats as a versatile, quick-grow - weed-suppressing biomass, take up excess soil nutri- ing cover for many benefits: ents and can improve the productivity of legumes when planted in mixtures. The cover’s fibrous root Affordable biomass. With good growing condi - system also holds soil during cool-weather gaps in tions and sound management (including timely rotations, and the ground cover pro vides a mellow planting), expect 2,000 to 4,000 pounds of dry mulch before low-till or no-till crops. matter per acre from late-summer/early fall-seed - An upright, annual grass, oats thrive under cool, ed oats and up to 8,000 pounds per acre from moist conditions on well-drained soil. Plants can spring stands. reach heights in excess of 4 feet. Stands generally fare poorly in hot, dry weather. Nutrient catch crop. Oats take up excess N and small amounts of P and K when planted early

OATS 93 enough. Late-summer plantings can absorb as but, because of its relatively high nitrogen con- much as 77 lb. N/A in an eight- to ten-week peri - tent, could pose a nitrate-poison ing threat to live- od, studies in the Northeast and Midwest have stock, especially if you delay harvesting until oats shown (313, 329). are nearing the flowering stage. Where the plant winterkills, some farmers use The climbing growth habit of some viny oats as a nitrogen catch crop after summer legumes such as vetch can contribute to lodging legume plowdowns, to hold some N over winter and make oat grain harvest difficult. If you’re without needing to kill the cover in spring. Some growing the legume for seed, the oats can serve as of the N in the win- a natural trellis that eases combining. Oats are a terkilled oats may still be MANAGEMENT reliable, low-cost lost by spring, either through denitrification cover that into the atmosphere or Establishment & Fieldwork by leaching from the soil Time seeding to allow at least six to 10 weeks of winterkill in profile. Consider mixing cool-season growth. Moderately fertile soil gives Zone 6 and oats with an overwinter- the best stands. ing legume if your objec- much of Zone 7. tive is to maximize N Late-summer/early-fall planting. For a win - contribution to the next terkilled cover, spring oats usually are seeded in crop. late summer or early fall in Zone 7 or colder. Broadcasting or overseeding will give the best Smother crop. Quick to germinate, oats are a results for the least cost, unless seeding into heavy great smother crop that outcompetes weeds and residue. Cleaned, bin-run seed will suffice. also provides allelopathic residue that can hinder If broadcasting and you want a thick win - germination of many weeds—and some crops (see terkilled mulch, seed at the highest locally recom - below)—for a few weeks. Reduce crop sup - mended rate (probably 3 to 4 bushels per acre) at pression concerns by waiting two- to three weeks least 40 to 60 days before your area’s first killing after killing oats before planting a subsequent crop. frost. Assuming adequate moisture for quick germination, the stand should provide some soil-pro- Fall legume nurse crop. Oats have few equals tecting, weed-suppressing mulch. as a legume nurse crop or companion crop. They Disk lightly to incorporate. In many regions, can increase the fertilizer replacement value of you’ll have the option of letting it winterkill or legumes. Adding about 35 to 75 lb. oats/A to the sending in cattle for some fall grazing. seeding mix helps slow-establishing legumes such If seeding oats as a fall nurse crop for a legume, as hairy vetch, clovers or winter peas, while a low rate (1 to 2 bushels per acre) works well. increasing biomass. It also helps reduce fall If drilling oats, seed at 2 to 3 bushels per acre 1 1 weeds. The oats will winterkill in many areas /2 to 1 inch deep, or 1 /2 inches when growing while improving the legume’s winter survival. grain you plan to harrow for weed control. Shallow seeding in moist soil provides rapid emer- Spring green manure or companion crop. gence and reduces incidence of root rot dis ease. Spring-seeded with a legume, oats can provide Timing is critical when you want plenty of bio- hay or grain and excellent straw in the Northern mass or a thick ground cover. As a winter cover U.S., while the legume remains as a summer—or following soybeans in the Northeast or Midwest, even later—cover. There’s also a haylage option overseeding spring oats at the leaf-yellowing or with a fast-growing legume if you harvest when early leaf-drop stage (and with little residue pre- oats are in the dough stage. The oats will increase sent) can give a combined ground cover as high the dry matter yield and boost the total protein, as 80 percent through early winter (200). If you

94 MANAGING COVER CROPS PROFITABLY wait until closer to or after soybean harvest, however, you’ll obtain much less oat biomass to help retain bean residue, Iowa and Pennsylvania studies have shown. Delaying planting by as little as two weeks in late summer also can reduce the cover’s effectiveness as a spring weed fighter, a study in upstate New York showed. By spring, oat plots that had been planted on August 25 had 39 percent fewer weed plants and one-seventh the weed biomass of control plots with no oat cover, while oats planted two weeks later had just 10 percent fewer weed plants in spring and 81 percent of the weed biomass of control plots (329, 330). Marianne Sarrantonio Marianne No-hassle fieldwork. As a winterkilled cover, OATS (Avena sativa) just light disking in spring will break up the brit - tle oat residue. That exposes enough soil for If you want to incorporate the stand, allow warming and timely planting. Or, no-till directly at least two to three weeks before planting the into the mulch, as the residue will decompose next crop. readily early in the season. Killing too early reduces the biomass potential and you could see some regrowth if killing Winter planting. As a fall or winter cover crop mechanically. But waiting too long could make in Zone 8 or warmer, seed oats at low to medium tillage of the heavier growth more difficult in a rates. You can kill winter-planted oats with spring conven tional tillage system and could deplete soil plowing, or with herbicides in reduced-tillage sys- mois ture needed for the next crop. Timely killing tems. also is important because mature oat stands can tie up nitrogen. Spring planting. Seeding rate depends on your intended use: medium to high rates for a spring Pest Management green manure and weed suppressor, low rates for Allelopathic (naturally occurring herbicidal) mixtures or as a legume companion crop. Higher compounds in oat roots and residue can hinder rates may be needed for wet soils or thicker weed growth for a few weeks.These compounds ground cover. Excessive fertility can encourage also can slow germination or root growth of some lodging, but if you’re growing oats just for its subsequent crops, such as lettuce, cress, timothy, cover value, that can be an added benefit for weed rice, wheat and peas. Minimize this effect by wait - suppression and moisture conservation. ing three weeks after oat killing before seeding a susceptible crop, or by following with an alter- Easy to kill. Oats will winterkill in most of zone nate crop. Rotary hoeing or other pre-emerge 7 or colder. Otherwise, kill by mowing or spray ing mechanical weeding of solo-seeded oats can soon after the vegetative stage, such as the milk or improve annual broadleaf control. soft dough stage. In no-till systems, rolling/crimp- Oats are less prone to insect problems than ing will also work (best at dough stage or later). wheat or barley. If you’re growing oats for grain or See Cover Crop Roller Design Holds Promise For forage, armyworms, various grain aphids and No-Tillers, p. 146. If speed of spring soil-warming mites, wireworms, cutworms, thrips, leaf hoppers, is not an issue, you can spray or mow the oats and grubs and billbugs could present occasional leave on the soil surface for mulch. problems.

OATS 95 Oats, Rye Feed Soil in Corn/Bean Rotation

Bryan and Donna Davis like what cover crops Spring oats are broadcast in mid or late March have done for their corn/soybean rotation. with a fertilizer cart and then rotary harrowed. If They use less grass herbicide, have applied going back to corn, they seed at a heavier, 3.5 bu insecti cides only once in the last six years, and rate, expecting only about 5 or 6 weeks of growth they have seen organic matter content almost before they work down the cover crop with a soil double from less than 2% to almost 4%. finisher and plant corn in early May. For soybeans, Rye and oats are the cover crop mainstays on they either kill chemically and no-till the beans, or the nearly 1,000 acres they farm near Grinnell, work down and seed conventionally. Iowa. Bryan and Donna purchased the farm—in They have managed rye in different ways over the family since 1929—in 1987 and almost im - the years depending on its place in the rotation, medi ately put most of the operation under 100% but prefer to seed into killed or tilled rye rather no-till, a system they had experimented with over than a living cover crop. They figure that they get the years. They now till some acres and are also in about 35 lb. N from oats and up to 60 lb. from rye. the process of transitioning 300 acres to organic. On their organic transition acres they are 1 Moving /3 of their acreage toward organic applying chicken manure (2 tons/A), and seems the logical culmination of the Davis’ cover crops are crucial to sopping up excess makeover of their farm that started with a nutrients and crowding out the weeds that desire to “get away from the chemicals.” That crop up in response to the extra nutrients. was what motivated them to start using cover They feel that their efforts to balance nutrients crops to feed the soil and help manage pests. are also helping with weed control, because “We were trying to get away from the idea weeds feed on nutrient imbalances. that every bug and weed must be exterminated. In addition to the increase in soil organic Rather, we need to ‘manage’ the system and matter, attributed to cover crops and no-tillage, tolerate some weed and insect pressure. It should they’ve also seen improvements in soil moisture be more of a balance,” says Bryan. and infiltration. Fields that used to pond after Bryan and Donna are practitioners and heavy rains no longer do. Soybeans are weathering proponents of “biological farming,” a systems drought better, and corn stays green longer during approach based on such principles as feeding a “more natural” drying down process. the soil to keep it biologically active, reducing “Our system takes more time and is more labor chemical inputs and paying attention to trace intensive, but if you look at the whole budget, we elements or micronutrients in order to are doing much better now. We have cut our maintain balance in the system. Cover crops chemical costs dramatically, and have reduced 1 play an integral role in this system. fertility costs—in some fields—by /3 to ½,” says They seed oats at 2-3 bu/A in spring or fall, Bryan. “With energy costs these days, you can’t depending on time and labor availability. Donna afford not to do this.” does most of the combining and planting, but Davis is careful to note that this is not just even with a lot of acres for two people to about adding one component such as cover manage, cover crops are a high priority on their crops. “You need to address the whole system, not schedule. Fall-seeded oats are planted after just one piece of the pie. To be able to have a soybean harvest and “need rain on them soon sustaining system, you must work with the living after planting to get them started.” They’ll put on system. Feed the soil and give it a roof over its about a foot of growth before winterkilling, head.” Cover crops play a crucial role in that usually in December in their south-central Iowa system. conditions. —Andy Clark

96 MANAGING COVER CROPS PROFITABLY Resistant oat varieties can minimize rusts, market for organic oats also could exist in your smuts and blights if they are a concern in your area, he observes. area or for your cropping system. Cover crops Oats are more palatable than rye and easily such as oats help reduce root-knot nematodes and overgrazed. If using controlled grazing in oat vegetable crop diseases caused by Rhizoctonia, stands, watch for high protein levels, which can results of a producer study in South Carolina vary from 12 to 25 percent (434). The potassium show (448), although brassicas are better. To level of oat hay also is sometimes very high and reduce harmful nema todes that oats could could cause metabolic problems in milking cows encourage, avoid planting oats two years in a row if it’s the primary forage. Underseeding a legume or after nematode-susceptible small grains such as enhances the forage option for oats by increasing wheat, rye or triticale (71). the biomass (compared with solo-cropped oats) and providing nitrogen for a subsequent crop. Other Options There are many low-cost, regionally adapted and COMPARATIVE NOTES widely available oat varieties, so you have hay, straw, forage or grain options. Select for cul- • Fall brassicas grow faster, accumulate more tural and local considerations that best fit your N and may suppress weeds, nematodes and intended uses. Day-length, stalk height, resistance disease better than oats. to disease, dry matter yield, grain test weight and • Rye grows more in fall and early spring, other traits may be important considerations. In absorbs more N and matures faster, but is the Deep South, fast-growing black oats (Avena harder to establish, to kill and to till than oats. strigosa) look promising as a weed-suppressive • As a legume companion/nurse crop, oats out- cover for soybeans. See Up-and-Coming Cover perform most varieties of other cereal grains. Crops (p. 191). • Oats are more tolerant of wet soil than is bar- Aside from their value as a cover crop, oats are ley, but require more moisture. a great feed supplement, says grain and hog farmer Carmen Fernholz, Madison, Minn. A niche Seed sources. See Seed Suppliers (p. 195).

OATS 97 RYE Secale cereale

Also called: cereal rye, winter rye, grain rye

Type: cool season annual cereal grain

Roles: scavenge excess N, prevent erosion, add organic matter, suppress weeds

Mix with: legumes, grasses or other cereal grains

See charts, pp. 66 to 72, for ranking and management summary.

he hardiest of cereals, rye can be seeded • A Maryland study credited rye with holding later in fall than other cover crops and still 60 percent of the residual N that could have Tprovide considerable dry matter, an exten - leached from a silt loam soil following intensive soil-holding root system, significant reduction tionally over-fertilized corn (372). of nitrate leaching and exceptional weed sup - • A Georgia study estimated rye captured from pression. Inexpensive and easy to establish, rye out- 69 to 100 percent of the residual N after a performs all other cover crops on infertile, sandy or corn crop (220). acidic soil or on poorly prepared land. It is widely • In an Iowa study, overseeding rye or a rye/oats adapted, but grows best in cool, temper ate zones. mix into soybeans in August limited leaching Taller and quicker-growing than wheat, rye can loss from September to May to less than 5 lb. serve as a windbreak and trap snow or hold rain - N/A (313). fall over winter. It overseeds readily into many high-value and agronomic crops and resumes Rye increases the concentration of exchange able growth quickly in spring, allowing timely killing potassium (K) near the soil surface, by bring ing it by rolling, mowing or herbicides. Pair rye with a up from lower in the soil profile (123). winter annual legume such as hairy vetch to off- Rye’s rapid growth (even in cool fall weather) set rye’s tendency to tie up soil nitrogen in spring. helps trap snow in winter, further boosting win - terhardiness. The root system promotes better BENEFITS drainage, while rye’s quick maturity in spring— compared with other cover crops—can help con - Nutrient catch crop. Rye is the best cool-season serve late-spring soil moisture. cereal cover for absorbing unused soil N. It has no taproot, but rye’s quick-growing, fibrous root sys - Reduces erosion. Along with conservation tem can take up and hold as much as 100 lb. N/A tillage practices, rye provides soil protection on until spring, with 25 to 50 lb. N/A more typical sloping fields and holds soil loss to a tolerable (422). Early seeding is better than late seeding for level (124). scavenging N (46).

98 MANAGING COVER CROPS PROFITABLY Fits many rotations. In most regions, rye can by 99 percent in a California study (422). You can serve as an overwintering cover crop after corn increase rye’s weed-suppressing effect before no- or before or after soybeans, fruits or vegetables. till corn by planting rye with an annual legume It’s not the best choice before a small grain crop such as hairy vetch. Don’t expect complete weed such as wheat or barley unless you can kill rye control, however. You’ll probably need comple- reliably and completely, as volunteer rye seed mentary weed management measures. would lower the value of other grains. Rye also works well as a strip cover crop and Pest suppressor. While rye is susceptible to the windbreak within vegetables or fruit crops and as same insects that attack other cereals, serious a quick cover for rotation gaps or if another crop infestations are rare. Rye reduces insect pest fails. prob lems in rotations (448) You can overseed rye into vegetables and tas- and attracts significant num- Rye can be seling or silking corn with consistently good bers of beneficials such as planted later results. You also can overseed rye into brassicas lady beetles (56). (369, 422), into soy beans just before leaf drop or Fewer diseases affect rye in fall than between pecan tree rows (61). than other cereals. Rye can other cover help reduce root-knot nema- Plentiful organic matter. An excellent source todes and other harmful crops. of residue in no-till and minimum-tillage systems nematodes, research in the and as a straw source, rye provides up to 10,000 South suggests (20, 448). pounds of dry matter per acre, with 3,000 to 4,000 pounds typical in the Northeast (118, 361). Companion crop/legume mixtures. Sow rye A rye cover crop might yield too much residue, with legumes or other grasses in fall or overseed depending on your tillage system, so be sure your a legume in spring. A legume helps off set rye’s planting regime for subsequent crops can handle tendency to tie up N. A legume/rye mix ture this. Rye overseeded into cabbage August 26 cov- adjusts to residual soil N levels. If there’s plenty of ered nearly 80 per cent of the between-row plots N, rye tends to do better; if there is insufficient N, by mid-October and, despite some summer heat, the legume component grows better, Maryland already had accumulated nearly half a ton of bio- research shows (86). Hairy vetch and rye are a mass per acre in a New York study. By the May 19 popular mix, allowing an N credit before corn of plowdown, rye provided 2.5 tons of dry matter 50 to 100 lb. N/A. Rye also helps protect the less per acre and had accumulated 80 lb. N/A. hardy vetch seedlings through winter. Cabbage yields weren’t affected, so competi tion wasn’t a problem (329). MANAGEMENT

Weed suppressor. Rye is one of the best cool Establishment & Fieldwork season cover crops for outcompeting weeds, Rye prefers light loams or sandy soils and will ger - especially small-seeded, light-sensitive annuals minate even in fairly dry soil. It also will grow in such as lambsquarters, redroot pigweed, vel - heavy clays and poorly drained soils, and many vetleaf, chickweed and foxtail. Rye also suppress - cultivars tolerate waterlogging (63). es many weeds allelopathically (as a natural Rye can establish in very cool weather. It herbicide), including dandelions and Canada this - will germinate at temperatures as low as 34° F. tle and has been shown to inhibit germina tion of Vegetative growth requires 38° F or higher (361). some triazine-resistant weeds (336). Rye reduced total weed density an average of 78 Winter annual use. Seed from late summer to percent when rye residue covered more than 90 midfall in Hardiness Zones 3 to 7 and from fall to percent of soil in a Maryland no-till study (410), and midwinter in Zones 8 and warmer. In the Upper

RYE 99 Midwest and cool New England states, seed two to eight weeks earlier than a wheat or rye grain crop to ensure maximum fall, winter and spring growth. Elsewhere, your tillage system and the amount of fall growth you prefer will help deter - mine planting date. Early planting increases the amount of N taken up before winter, but can make field management (especially killing the cover crop and tillage) more difficult in spring. See Rye Smothers Weeds Before Soybeans (p. 104). Rye is more sensitive to seeding depth than other cereals, so plant no deeper than 2 inches (71). Drill 60 to 120 lb./A (1 to 2 bushels) into a prepared seedbed or broadcast 90 to 160 lb./A (1.5 to 3 Sarrantonio Marianne bushels) and disk lightly or cultipack (361, 422). CEREAL RYE (Secale cereale) If broadcasting late in fall and your scale and budget allow, you can increase the seed ing rate to mination), the rye can’t set seed and dies on its as high as 300 or 350 lb./A (about 6 bushels) to own within a few months in many areas. This pro- ensure an adequate stand. Rye can be overseed by vides good weed control in asparagus, says Rich air more consistently than many other cover crops. de Wilde, Viroqua, Wis. “I use a Buffalo Rolling Stalk Chopper to help After drilling a large-seeded summer crop such shake rye seeds down to the soil surface,” says as soybeans, try broadcasting rye. The cover grows Steve Groff, a Holtwood, Pa., vegetable grower. well if it’s a cool spring, and the summer crop “It’s a very consistent, fast and economical way takes off as the temperature warms up. Secondary to establish rye in fall.” (Groff’s farming system tillage or herbicides would be neces sary to keep is described in detail at www.cedarmeadow the rye in check and to limit the cover crop’s use farm.com). of soil moisture.

Mixed seeding. Plant rye at the lowest locally Killing & Controlling recommended rate when seeding with a legume Nutrient availability concern. Rye grows and (361), and at low to medium rates with other matures rapidly in spring, but its maturity date grasses. In a Maryland study, a mix of 42 pounds of varies depending on soil moisture and tempera - rye and 19 pounds of hairy vetch per acre was the ture. Tall and stemmy, rye immobilizes N as it optimum fall seeding rate before no-till corn on a decomposes. The N tie-up varies directly with the silt loam soil (81). If planting with clovers, seed maturity of the rye. Mineralization of N is very rye at a slightly higher rate, about 56 lb. per acre. slow, so don’t count on rye’s overwintered N For transplanting tomatoes into hilly, erosion- becoming available quickly. prone soil, Steve Groff fall-seeds a per-acre mix of Killing rye early, while it’s still succulent, is one 30 pounds rye, 25 pounds hairy vetch and 10 way to minimize N tie-up and conserve soil mois- pounds crimson clover. He likes how the three- ture. But spring rains can be problematic with rye, way mix guarantees biomass, builds soil and pro - especially before an N-demanding crop, such as vides N. corn. Even if plentiful moisture has tens the opti- Spring seeding. Although it’s not a common mal kill period, you still might get too much rain practice, you can spring seed cereals such as rye in the following weeks and have significant as a weed-suppressing companion, relay crop or nitrate leaching, a Maryland study showed (109). early forage. Because it won’t have a chance to Soil compaction also could be a problem if you’re vernalize (be exposed to extended cold after ger - mowing rye with heavy equipment.

100 MANAGING COVER CROPS PROFITABLY Late killing of rye can deplete soil moisture and Mow-kill works well in the South after rye could produce more residue than your tillage sys - sheds pollen in late April (101). If soil moisture is tem can handle. For no-till corn in humid climates, adequate, you can plant cotton three to five days however, summer soil-water con servation by after mowing rye when row cleaners are used in cover crop residues often was more important reduced-tillage systems. than spring moisture depletion by grow ing cover Some farmers prefer to chop or mow rye by crops, Maryland studies showed (82, 84, 85). late boot stage, Rye is the best before it heads or Legume combo maintains yield. One way to flowers. “If rye gets cool-season cover offset yield reductions from rye’s immobilization away from you, of N would be to increase your N application. you’d be better off crop for scavenging Here’s another option: Growing rye with a baling it or harvest- N, typically carrying legume allows you to delay killing the covers by a ing it for seed,” few weeks and sustain yields, especially if the cautions southern 25 to 50 lb. N/A legume is at least half the mix. This gives the Illinois organic grain over to spring. legume more time to fix N (in some cases dou - farmer Jack Erisman bling the N contribution) and rye more time to (38). He often over- scavenge a little more leachable N. Base the kill winters cattle in rye date on your area’s normal kill date for a pure fields that precede soy beans. But he prefers that stand of the legume (109). soil temperature be at least 60° F before planting A legume/rye mix generally increases total dry beans, which is too late for him to no-till beans matter, compared with a pure rye stand. The high- into standing rye. er residue level can conserve soil moisture. For “If rye is at least 24 inches tall, I control it with best results, wait about 10 days after killing the a rolling stalk chopper that thoroughly flattens covers before planting a crop. This ensures ade- and crimps the rye stems,” says Pennsylvania veg - quate soil warming, dry enough conditions for etable grower Steve Groff. “That can sometimes planter coulters to cut cleanly and minimizes eliminate a burndown herbicide, depending on allelopathic effects from rye residue (84, 109). If the rye growth stage and next crop.” using a herbicide, you might need a higher spray A heavy duty rotavator set to only 2 inches volume or added pressure for adequate coverage. deep does a good job of tilling rye, says Rich de Legume/rye mixes can be rolled once the legume Wilde, Viroqua, Wis. is at full bloom (303). Can’t delay a summer planting by a few weeks Kill before it matures. Tilling under rye usu- while waiting for rye to flower? If early rye culti - ally eliminates regrowth, unless the rye is less than vars aren’t available in your area and you’re in 12 inches tall (361, 422). Rye often is plowed or Zone 5 or colder, you could plow the rye and use disked in the Midwest when it’s about 20 inches secondary tillage. Alternately, try a knockdown tall (307). Incorporating the rye before it’s 18 in. herbicide and post-emergent herbicide or spot- high could decrease tie-up of soil N (361, 422). In spraying for residual weed control. Pennsylvania (118) and elsewhere, kill at least 10 For quicker growth of a subsequent crop such days before planting corn. as corn or soy beans, leave the residue upright For best results when mow-killing rye, wait after killing (rather than flat). That hastens crop until it has begun flowering. A long-day plant, rye develop ment—unless it’s a dry year—via warmer is encouraged to flower by 14 hours of daylight soil temperatures and a warmer seed zone, and a temperature of at least 40° F. A sickle bar according to a three-year Ontario study (146). mower can give better results than a flail mower, This rarely influences overall crop yield, however, which causes matting that can hinder emergence unless you plant too early and rye residue or low of subsequent crops (116). soil tem perature inhibits crop germination.

RYE 101 Cereal Rye: Cover Crop Workhorse

Talk to farmers across America about cover Fall management (planting): crops and you’ll find that most of them have • While results are best if you plant rye by planted a cereal rye cover crop. Almost early fall, it also can be planted in certainly the most commonly planted cover November or December in much of the crop, cereal rye can now be seen growing on country—even into January in the deep millions of acres of farmland each year. South—and still provide tangible benefits. There are almost as many ways to manage • It can be drilled or broadcast after main cover crop rye as there are farmers using it. crop harvest, with or without cultivation. Climate, production system, soil type, • It can be seeded before main crop harvest, equipment and labor are the principal factors usually by broadcasting, sometimes by plane that will determine how you manage rye. Your or helicopter, and in northern climates, at own practical experience will ultimately last cultivation of the cash crop. Soil mois- determine what works best for you. ture availability is crucial to many of these Check out how others are managing rye in pre-harvest seeding methods, either for ger- this book, on the Web and around your region. mination of the cover crop or to avoid com- Test alternatives management practices that petition for water with the main crop. allow you to seed earlier or manage cover crop residue differently. Add a legume, a Spring management (termination) is even brassica or another grass to increase diversity more diverse: on your farm. • Rye can be killed with tillage, mowing, Reasons for rye’s widespread use include: rolling or spraying. • It is winter-hardy, allowing it to grow longer • It can be killed before or after planting the into fall and resume growth earlier in the cash crop, which can be drilled into stand- spring than most other cover crops. ing cover crops in conservation tillage • It produces a lot of biomass, which trans- systems. lates into a long-lasting residue cover in con- • Some want to leave rye growing as long as servation tillage systems. possible; others insist on terminating it as • It crowds out and out-competes winter soon as possible in spring. annual weeds, while rye residue helps sup- • Vegetable growers may leave walls of stand- press summer weeds. ing rye all season long between crop rows, • It scavenges nutrients—particularly nitrogen usually to alleviate wind erosion. —very effectively, helping keep nutrients on the farm and out of surface and ground Some examples of rye management wisdom water. from practitioners around the country: • It is relatively inexpensive and easy to seed. • Pat Sheridan Jr., Fairgrove, Mich. Continuous • It works well in mixtures with legumes, no-till corn, sugar beets, soybeans, dry resulting in greater biomass production and beans: “In late August, we fly rye into stand- more complete fall/winter ground cover. ing corn (or soybeans if we’re coming back • It can be used as high-quality forage, either with soybeans the following year). We grazed or harvested as ryelage. learned that rye is easier to burn down • It can fit into many different crop and live- when it’s more than two feet tall than stock systems, including corn/soybean rota- when it has grown only a foot or less.” tions, early or late vegetable crops, and dairy • Barry Martin, Hawksville, Ga. Peanuts and or beef operations. cotton. “After cotton, in late October or

102 MANAGING COVER CROPS PROFITABLY November, we use a broadcast spreader • Ed Quigley, Spruce Creek, PA. Dairy. “We seed (two bushels of rye per acre), then shred or cereal rye (two bushels per acre) immediate- mow to cover the seed. We usually get ly after corn silage. We allow as much spring enough moisture in November and growth as possible up to about 10 inches, at December for germination. After peanuts, which point it becomes more difficult to kill, we use a double disc grain drill (1.5 bushels especially with cool/overcast conditions. We of rye per acre) in mid-September to mid- will also wait to make rylage in spring if we October.” need feed, and then plant corn a bit later.” • Bryan and Donna Davis, Grinell, Iowa. Corn, soybeans, hay. “We tried to no-till corn and In some areas, farmers substitute other small beans into rye three feet tall, but failed. The grain cover crops for rye. They are doing so to C:N ratio was way out of whack. The corn better fit their particular niches, better manage looked like it had been sprayed. If you don’t their systems, or to cut costs by saving small kill before planting, you will invite insects.” grain seeds. Wheat is a popular alternative to See also Oats, Rye Feed Soil in Corn/Bean rye. Look around and experiment! Rotation, p. 96. —Andy Clark

Pest Management bigflower vetch (a quick-establishing, self-seed - Thick stands ensure excellent weed ing, winter-annual legume that flowers and sup pression. To extend rye’s weed-management matures weeks ahead of hairy vetch) can sup - benefits, you can allow its allelopathic effects to press weeds signifi- persist longer by leaving killed residue on the sur- cantly more than Rye can effectively face rather than incorporating it. Allelopathic rye alone, while effects usually taper off after about 30 days. After also allowing high- suppress weeds by killing rye, it’s best to wait three to four weeks er N accumulations shading, competition before planting small-seeded crops such as car- (110). rots or onions. If strip tilling vegetables into rye, “Rye can provide and allelopathy. be aware that rye seedlings have more allelopath- the best and clean- ic compounds than more mature rye residue. est mulch you Transplanted veg etables, such as tomatoes, and could want if it’s cut or baled in spring before pro- larger-seeded species, especially legumes, are less ducing viable seed,” says Rich de Wilde. Rye can susceptible to rye’s allelopathic effects (117). become a volunteer weed if tilled before it’s 8 In an Ohio study, use of a mechanical under-cut- inches high, however, or if seedheads start matur- ter to sever roots when rye was at mid- to late ing before you kill it. Minimize regrowth by wait- bloom—and leaving residue intact on the soil sur - ing until rye is at least 12 inches high before face (as whole plants)—increased weed suppres - incorporating or by mow-killing after flowering sion, compared with incorporation or mowing. but before grain fill begins. The broadleaf weed reduction was comparable to that seen when sickle-bar mowing, and better Insect pests rarely a problem. Rye can reduce than flail-mowing or conventional tillage (96). insect pest problems in crop rotations, southern If weed suppression is an important objective research suggests (448). In a number of mid- when planting a rye/legume mixture, plant early Atlantic locations, Colorado pota to beetles have enough for the legume to establish well. Other - been virtually absent in tomatoes no-till trans - wise, you’re probably better off with a pure stand. planted into a mix of rye/vetch/crimson clover, Overseeding may not be cost-effective before a perhaps because the beetles can’t navigate crop such as field corn, however. A mix of rye and through the residue.

RYE 103 Rye Smothers Weeds Before Soybeans

An easy-to-establish rye cover crop helps 13 ounces of surfactant per acre makes it Napoleon, Ohio, farmer Rich Bennett enrich his easier for Roundup to penetrate rye leaves,” sandy soil while trimming input costs in no-till he explains. soybeans. Bennett broadcasts rye at 2 bushels The cover dies in about two weeks. The per acre on corn stubble in late October. He slow kill helps rye suppress weeds while incorporates the seed with a disc and roller. soybeans establish. In this system, Bennett The rye usually breaks through the ground doesn’t have to worry about rye regrowing. but shows little growth before winter Roundup Ready® beans have given him dormancy. Seeded earlier in fall, rye would greater flexibility in this system. He used to provide more residue than Bennett prefers cultivate beans twice using a Buffalo no-till by bean planting—and more effort to kill the cultivator. Now, depending on weed pressure cover. “Even if I don’t see any rye in fall, I know (often giant ragweed and velvetleaf) he will it’ll be there in spring, even if it’s a cold or wet spot treat or spray the whole field once with one,” he says. Roundup. Bennett figures the rye saves him By early May, the rye is usually at least 1.5 $15 to $30 per acre in material costs and feet tall and hasn’t started heading. He no-tills fieldwork, compared with conventional no-till soybeans at 70 pounds per acre on 30-inch systems for soybeans. rows directly into standing rye cover crop. Rye doesn’t hurt his bean yields, either. Then, depending on the amount of rye growth, Usually at or above county average, his yields he kills the rye with herbicide immediately range from 45 to 63 bushels per acre, after planting, or waits for more rye growth. depending on rainfall, says Bennett. “If it’s shorter than 15 to 18 inches, rye “I really like rye’s soil-saving benefits,” he won’t do a good enough job of shading out says. “Rye reduces our winter wind erosion, broadleaf weeds,” notes Bennett, who likes improves soil structure, conserves soil how rye suppresses foxtail, pigweed and moisture and reduces runoff.” Although he lambsquarters. “I sometimes wait up to two figures the rye’s restrained growth (from the weeks to get more rye residue,” he says. late fall seeding) provides only limited “I kill the rye with 1.5 pints of Roundup scavenging of leftover N, any that it does per acre—about half the recommended rate. absorb and hold overwinter is a bonus. Adding 1.7 pounds of ammonium sulfate and Updated in 2007 by Andy Clark

While insect infestations are rarely serious with can reduce diseases in some cropping systems. rye, as with any cereal grain crop occasional prob- No-till transplanting tomatoes into a mix of lems occur. If armyworms have been a problem, rye/vetch/crimson clover, for example, consistent - for example, burning down rye before a corn ly has been shown to delay the onset of early crop could move the pests into the corn. Purdue blight in several locations in the Northeast. The Extension entomologists note many northeastern mulch presumably reduces soil splashing onto the Indiana corn farmers reported this in 1997. Crop leaves of the tomato plants. rotations and IPM can resolve most pest problems If you want the option of harvesting rye as a you might encounter with rye. grain crop, use of resistant varieties, crop rotation and plowing under crop residues can minimize Few diseases. Expect very few diseases when rust, stem smut and anthracnose. growing rye as a cover crop. A rye-based mulch

104 MANAGING COVER CROPS PROFITABLY Other Options don’t expect dramatic soil improvement from a Quick to establish and easy to incorporate when single stand’s growth. Left in a poorly draining succulent, rye can fill rotation gaps in reduced- field too long, a rye cover could slow soil tillage, semi-permanent bed systems without and warming even further, delaying crop planti- increasing pest concerns or delaying crop plant - ng. It’s also not a silver bullet for eliminating her- ings, a California study showed (216). bi cides. Expect to deal with some late-season Erol Maddox, a Hebron, Md. grower, takes weeds in subsequent crops (410). advantage of rye’s relatively slow decomposition when double cropping. He likes transplanting COMPARATIVE NOTES spring cole crops into rye/vetch sod, chopping the cover mix at bloom stage and letting it lay • Rye is more cold- and drought-tolerant than until August, when he plants fall cole crops. wheat. Mature rye isn’t very palatable and provides • Oats and barley do better than rye in hot poor-quality forage. It makes high quality hay or bal - weather. age at boot stage, however, or grain can be ground • Rye is taller than wheat and tillers less. It can and fed with other grains. Avoid feeding ergot- produce more dry matter than wheat and a infected grain because it may cause abortions. few other cereals on poor, droughty soils but Rye can extend the grazing season in late fall is harder to burn down than wheat or triticale and early spring. It tolerates fall grazing or mow - (241, 361). ing with little effect on spring regrowth in many • Rye is a better soil renovator than oats (422), areas (210). Growing a mixture of more palatable but brassicas and sudangrass provide deeper cover crops (clovers, vetch or ryegrass) can soil penetration (451). encourage regrowth even further by discouraging • Brassicas generally contain more N than rye, overgrazing (329). scavenge N nearly as well and are less likely to tie up N because they decompose more Management Cautions rapidly. Although rye’s extensive root system provides quick weed suppression and helps soil structure, Seed sources. See Seed Suppliers (p. 195).

RYE 105 SORGHUM-SUDANGRASS HYBRIDS Sorghum bicolor x S. bicolor var. sudanese

Also called: Sudex, Sudax

Type: summer annual grass

Roles: soil builder, weed and nematode suppressor, subsoil loosener

Mix with: buckwheat, sesbania, sunnhemp, forage soybeans or cowpeas

See charts, pp. 66 to 72, for rank ing and management summary.

orghum-sudangrass hybrids are unrivaled for plants and nematodes. They are not frost tolerant, adding organic matter to worn-out soils. and should be planted after the soil warms in SThese tall, fast-growing, heat-loving summer spring or in summer at least six weeks before first annual grasses can smother weeds, suppress some frost. nematode species and penetrate compacted sub - soil if mowed once. Seed cost is modest. Followed BENEFITS by a legume cover crop, sorghum-sudangrass hybrids are a top choice for renovating over- Biomass producer. Sorghum-sudangrass grows farmed or compacted fields. 5 to 12 feet tall with long, slender leaves, stalks up The hybrids are crosses between forage-type to one-half inch in diameter and aggressive root sorghums and sundangrass. Compared with corn, systems. These features combine to produce they have less leaf area, more secondary roots and ample biomass, usually about 4,000 to 5,000 lb. a waxier leaf surface, traits that help them with - DM/A. Up to 18,000 lb. DM/A has been measured stand drought (361). Like corn, they require good with multiple cuttings on fertile soils with ade- fertility—and usually supplemental nitrogen—for quate moisture. best growth. Compared with sudangrass, these hybrids are taller, coarser and more productive. Subsoil aerator. Mowing whenever stalks reach Forage-type sorghum plants are larger, leafier 3 to 4 feet tall increases root mass five to eight and mature later than grain sorghum plants. times compared with unmowed stalks, and forces Compared with sorghum-sudangrass hybrids, they the roots to penetrate deeper. are shorter, less drought tolerant, and don’t In addition, tops grow back green and vegeta - regrow as well. Still, forage sorghums as well as tive until frost and tillering creates up to six new, most forms of sudangrass can be used in the same thicker stalks per plant. A single mowing on New cover-cropping roles as sorghum-sudan grass York muck soils caused roots to burrow 10 to 16 hybrids. All sorghum- and sudangrass-related inches deep compared to 6 to 8 inches deep for species produce compounds that inhibit certain unmowed plants. The roots of mowed plants frac-

106 MANAGING COVER CROPS PROFITABLY tured subsoil compaction with worm hole-like openings that improved surface drainage. However, four mowings at shorter heights caused plants to behave more like a grass and significantly decreased the mass, depth and diameter of roots (277, 450, 451).

Weed suppressor. When sown at higher rates than normally used for forage crops, sorghum - sudangrass hybrids make an effective smother crop. Their seedlings, shoots, leaves and roots secrete allelopathic compounds that suppress many weeds. The main root exudate, sor - goleone, is strongly active at extremely low con - centrations, comparable to those of some Sarrantonio Marianne synthetic herbicides (370). As early as five days SORGHUM-SUDANGRASS (Sorghum bicolor X S. after germination, roots begin secreting this alle - bicolor var. sudanese lochemical, which persists for weeks and has visi - ble effects on lettuce seedlings even at 10 parts tems, and weed and nematode suppression can per million (440). produce dramatic results. Sorghum-sudangrass hybrids suppress such On a low-producing muck field in New York annual weeds as velvetleaf, large crabgrass, barn - where onion yields had fallen to less than a third yardgrass (126, 305), green foxtail, smooth pig- of the local average, a single year of a dense plant - weed (190), common ragweed, redroot pigweed ing of sorghum-sudangrass hybrid restored the and purslane (316). They also suppressed pine soil to a condition close to that of newly cleared (214) and redbud tree seedlings in nursery tests land (217). (154). The residual weed-killing effects of these allelo chemicals increased when sorghum-sudan- Widely adapted. Sorghum-sudangrass hybrids grass hybrids were treated with the herbicides can be grown throughout the U.S. wherever rain - sethoxydim, glyphosate or paraquat, in descend- fall is adequate and soil temperature reaches ing order of magnitude (144). 65° F to 70° F at least two months before frost. Once established, they can withstand drought by Nematode and disease fighter. Planting going nearly dormant. Sorghum-sudangrass sorghum-sudangrass hybrids instead of a host hybrids tolerate pH as high as 9.0, and are often crop is a great way to disrupt the life cycles of used in rotation with barley to reclaim alkaline many diseases, nematodes and other pests. For soil (421). They tolerate pH as low as 5.0. example, when sorghum-sudangrass or sorghum alone were no-tilled into endophyte-infected fes - Quick forage. Sorghum-sudangrass is prized as cue pastures in Missouri that had received two summer forage. It can provide quick cover to pre - herbicide applications, the disease was controlled vent weeds or erosion where legume forages have nearly 100 percent. No-till reseeding with endo - been winterkilled or flooded out. Use care phyte-free fescue completed this cost-effective because these hybrids and other sorghums can renovation that significantly improved the rate of produce prussic acid poisoning in livestock. gain of yearling steers (16). Grazing poses the most risk to livestock when plants are young (up to 24 inches tall), drought Renews farmed-out soils. The combination of stressed or killed by frost. Toxicity danger varies abundant biomass production, subsoiling root sys- between cultivars.

SORGHUM-SUDANGRASS HYBRIDS 107 MANAGEMENT This can result in an unmanageable amount of tough residue that interferes with early planting Establishment the following spring (277). Plant sorghum-sudangrass when soils are warm Mowing or grazing when stalks are 3 to 4 feet and moist, usually at least two weeks after the tall encourages tillering and deeper root growth, prime corn-planting date for your area. It will tol - and keeps regrowth vegetative and less fibrous erate low-fertility, moderate acidity and high alka - until frost. For mid-summer cuttings, leave at least linity, but prefers good fertility and near-neutral 6 inches of stubble to ensure good regrowth and pH (361). Standard biomass production usually continued weed suppression. Delayed planting requires 75 to 100 lb. N/A . within seven weeks of frost makes mowing With sufficient surface moisture, broadcast 40 unnecessary and still allows for good growth to 50 lb./A, or drill 35 to 40 lb./A as deep as 2 inch- before winterkilling (277, 361). es to reach moist soil. Disking while plants are still vegetative will These heat-loving These rates provide a speed decomposition. Make several passes with a plants are unrivaled quicker canopy to heavy disk or combination tillage tool to handle smother weeds than the dense root masses (277). Sicklebar mowing or for adding organic lower rates used flail chopping before tillage will reduce the num - for forage produc - ber of field operations required to incorporate the matter to soils. tion, but they require crop and speed decom position. Sicklebar mowers mowing or grazing cut more cleanly but leave the stalks whole. Using to prevent lodging. a front-mounted flail chopper avoids the problem Herbicide treatment or a pass with a mechanical of skips where tractor tires flatten the plants, weeder may be necessary if germination is spotty putting them out of reach of a rear-mounted or perennial weeds are a problem. New York on- chopper. farm tests show that a stale seedbed method— Any operations that decrease the residue size tilling, then retilling to kill the first flush of weeds shortens the period during which the decompos - just before planting—provides effective weed ing residue will tie up soil nitrogen and hinder control. early planted crops in spring. Even when mowed, residue will become tough and slower to break Warm season mixtures. Plant sorghum-sudan - down if left on the surface. grass in cover crop mixtures with buckwheat or Flail chopping after frost or killing the cover with the legumes sesbania (Sesbania exaltata), crop with herbicide will create a suitable mulch sunnhemp (Crotolaria juncea), forage soybeans for no-till planting, preserving soil life and soil (Glycine max) or cowpeas (Vigna unguiculata). structure in non-compacted fields. Broadcast these large-seeded cover crops with the sorghum-sudangrass, then incorporate about Pest Management 1 inch deep. Fast-germinating buckwheat helps Weeds. Use sorghum-sudangrass to help control sup press early weeds. Sorghum-sudangrass sup- nutsedge infestations, suggests Cornell Extension ports the sprawling sesbania, forage soybeans IPM vegetable specialist John Mishanec. Allow and cow peas. Sunnhemp has an upright habit, the nutsedge to grow until it’s about 4 to 5 inch- but could compete well for light if matched es tall but before nutlets form, about mid-June in with a sorghum-sudangrass cultivar of a similar New York. Kill the nutsedge with herbicide, then height. plant the weed-smothering hybrid. To extend weed suppressive effects into the Field Management second season, select a cultivar known for weed Plants grow very tall (up to 12 feet), produce tons suppression and leave roots undisturbed when of dry matter and become woody as they mature. the stalks are mowed or grazed (440).

108 MANAGING COVER CROPS PROFITABLY Beneficial habitat. Some related sorghum culti - sorghum-sudangrass hybrid cultivars failed to vars harbor beneficial insects such as seven-spot - show any significant nematicidal effects in a later ted lady beetles (Coccinella septempunctata) and experiment in Wisconsin potato fields (249). lacewings (Chrysopa carnea) (421). When faced with infestations of the nematodes Nematodes. Sorghum-sudangrass hybrids and Meloidogoyne incognita and M. arenaria, other sorghum-related crops and cultivars sup- Oswego, N.Y., onion grower press some species of nematodes. Specific culti - Dan Dunsmoor found that a These plants vars vary in their effectiveness on different races well-incorporated sorghum- of nematodes. These high-biomass-producing sudangrass cover crop was produce crops have a general suppressive effect due to more effective than fumiga- chemicals their organic matter contributions. But they also tion. Further, the nematicidal produce natural nematicidal compounds that effect continued into the next that inhibit chemically suppress some nematodes, many stud- season, while the conditions a certain ies show. year after fumigation seemed Timing of cutting and tillage is very important worse than before the applica- weeds and to the effectiveness of nematode suppression. The tion. He reports that the cover crop needs to be tilled before frost while it sorghum-sudan grass cover nematodes. is still green. Otherwise, the nematicidal effect is crop also controls onion mag- lost. For maximum suppression of soil borne dis- got, thrips and Botrytis leaf eases, cut or chopped sudangrass must be well blight (217). incor porated immediately (308). For suppressing root-knot nematodes in Idaho Insect pests. Chinch bug (Blissus leucopterus), potato fields, rapeseed has proven slightly more sorghum midge (Contarinia sorghicola), corn effective and more dependable than sorghum - leaf aphid (Rhopalosiphum maidis), corn ear- sudangrass hybrids (394). worm (Heliothis zea), greenbugs (Schizaphis In an Oregon potato trial, TRUDAN 8 sudangrass gram inum) and sorghum webworm (Celama controlled Columbia root-knot nematodes sorghiella) sometimes attack sorghum-sudangrass (Meloidogoyne Chitwoodi), a serious pest of hybrids. Early planting helps control the first two many vegetable crops. Control extended through- pests, and may reduce damage from webworms. out the zone of residue incorporation. The cover Some cultivars and hybrids are resistant to chinch crop’s effect prevented upward migration of the bugs and some biotypes of greenbugs (361). In nematodes into the zone for six weeks, working Georgia, some hybrids hosted corn leaf aphid, as well as the nematicide ethoprop. Both treat- greenbug, southern green stinkbugs (Nezara ments allowed infection later in the season (285). viridula) and leaffooted bug (Leptoglossus phyl- In the study, TRUDAN 8 sudangrass and the lopus). sorghum-sudangrass hybrid cultivars SORDAN 79 and SS-222 all reduced populations of root-knot Crop Systems nematodes. These cultivars are poor nematode There are several strategies for reducing nitrogen hosts and their leaves—not roots—have a nemati - tie-up from residue: cidal effect. TRUDAN 8 should be used if the crop • Interplant a legume with the sorghum-sudan - will be grazed due to its lower potential for prus - grass hybrid. sic acid poisoning. The sorghum-sudangrass culti- • Plant a legume cover crop after the sorghum - vars are useful if the cover crop is intended for sudangrass hybrid, in either late summer or anti-nematicidal effects only (285). In other the following spring. Oregon and Washington trials, the cover crop sup - • Apply nitrogen fertilizer or some other N pression required supplemental chemical nemati - source at incorporation and leave the land fal- cide to produce profitable levels of U.S. No. 1 low for a few months when soil is not frozen potatoes (285). These same sudangrass and to allow decomposition of the residue.

SORGHUM-SUDANGRASS HYBRIDS 109 Summer Covers Relieve Compaction

A summer planting of sudangrass was the best fall cash crop into the rotation while still single-season cover crop for relieving soil growing the cover during summer. compaction in vegetable fields, a team of Heavy equipment, frequent tillage and lack Cornell researchers found. Yellow mustard, of organic matter contribute to compaction HUBAM annual white sweetclover and problems for vegetable growers in the perennial ryegrass also were effective Northeast, where frequent rains often force to some extent in the multi-year study. “But growers into the fields when soils are wet. sudangrass has proven the most promising so Compacted soils slow root development, far,” says project coordinator David Wolfe. “It hinder nutrient uptake, stunt plants, delay has shown the fastest root growth.” maturity and can worsen pest and disease “Sudangrass is best managed with one problems (451). For example, the Cornell mowing during the season,” Wolfe adds. Mowing researchers found that slow-growing cabbages promotes tillering and a deep, penetrating root direct-seeded into compacted soils were system. Mowing also makes it easier to vulnerable to flea beetle infestations (450). incorporate the large amount of biomass Brassica cover crops such as yellow mustard produced by this crop. With its high C:N ratio, were solid challengers to sudangrass as a it adds to soil organic matter. compaction reliever, but it was sometimes Farmers and researchers have long known difficult to establish these crops in the test. that alfalfa’s deep root system is a great “We still have a lot to learn about how best compaction-buster. But alfalfa does not to grow brassicas and fit them into rotations establish easily on wet compacted fields, and with vegetables,” Wolfe says. most vegetable growers can’t afford to remove Wolfe and his team assessed the cover land from production for two to three years to crops’ effectiveness by measuring yields of grow it, notes Wolfe. Many also lack the subsequent crops and conducting a host of equipment to subsoil their fields, which is soil quality measurements, including often only a temporary solution, at best. That’s infiltration rates, water-holding capacity, why Wolfe geared his study to identify cover aggregate stability and organic matter levels. crops that can produce results in a single For more information, contact David Wolfe, season. In the case of heat-loving sudangrass, 607-255-7888; [email protected]. it also may be possible to squeeze a spring or Updated in 2007 by Andy Clark

If you kill the cover crop early enough in fall, vide needed soil structure benefits wherever the residue will partially break down before cold intensive systems cause compaction and loss of temperatures slow biological action (361). Where soil organic matter reserves. See Summer Covers possible, use sorghum-sudangrass ahead of later- Relieve Compaction, above. planted crops to allow more time in spring for Grown as a summer cover crop that is cut once residue to decompose. and then suppressed or killed, sorghum-sudan - Planting sorghum-sudangrass every third year grass can reduce weeds in fall-planted alfalfa. on New York potato and onion farms will rejuve - Sorghum-sudangrass suppressed alfalfa root nate soil, suppress weeds and may suppress soil growth significantly in a Virginia greenhouse pathogens and nematodes. Working a legume into study (144), but no effect was observed on alfalfa the rotation will further build soil health and add germination when alfalfa was no-till planted into nitrogen. Sorghum-sudangrass hybrids can pro - killed or living sorghum-sudangrass (145).

110 MANAGING COVER CROPS PROFITABLY In Colorado, sorghum-sudangrass increased irri- Cultivars. When comparing sorghum-sudangrass gated potato tuber quality and total marketable cultivars, consider traits such as biomass yield yield compared. It also increased nutrient uptake potential, tillering and regrowth ability, disease efficiency on the sandy, high pH soils. In this sys- resistance, insect resistance (especially if green - tem, the sorghum-sudangrass is grown with limit- bugs are a problem) and tolerance to iron defi - ed irrigation, but with enough water so that the ciency chlorosis. biomass could be harvested for hay or incorpo- If you plan to graze the cover crop, select rated as green manure (112, 113). sorghum-sudangrass hybrids and related crops In California, some table grape growers use with lower levels of dhurrin, the compound sorghum-sudangrass to add organic matter and to responsible for prussic acid poisoning. For maxi- reduce the reflection of light and heat from the mum weed control, choose types high in sor- soil, reducing sunburn to the grapes. goleone, the root exudate that suppresses weeds. Sterile cultivars are best where escapes could be COMPARATIVE NOTES a problem, especially where crossing with johnsongrass (Sorghum halpense) is possible. Sorghum-sudangrass hybrids can produce more organic matter per acre, and at a lower seed cost, Seed sources. See Seed Suppliers (p. 195). than any major cover crop grown in the U.S. Incorporated sorghum-sudangrass residue reduces N availability to young crops more than oat residue but less than wheat residue (389).

WINTER WHEAT Triticum aestivum

Type: winter annual cereal grain; can be spring-planted

Roles: prevent erosion, suppress weeds, scavenge excess nutrients, add organic matter

Mix with: annual legumes, ryegrass or other small grains

See charts, pp. 66 to 72, for ranking and management summary.

lthough typically grown as a cash grain, rush to kill it early in spring and risk compacting winter wheat can provide most of the soil in wet conditions. It is increasingly grown Acover crop benefits of other cereal crops, instead of rye because it is cheaper and easier to as well as a grazing option prior to spring tiller manage in spring. elongation. It’s less likely than barley or rye to Whether grown as a cover crop or for grain, become a weed and is easier to kill. Wheat also is winter wheat adds rotation options for slower to mature than some cereals, so there is no underseeding a legume (such as red clover or

WINTER WHEAT 111 sweet-clover) for forage or nitrogen. It works well without underseed- in no-till or reduced-tillage systems, and for weed ing a legume or control in potatoes grown with irrigation in semi- legume-grass mix, arid regions. winter wheat provides great BENEFITS grazing and nutritional value Erosion control. Winter wheat can serve as an and can extend the overwintering cover crop for erosion control in grazing season. most of the continental U.S. • In Colorado vegetable systems, wheat Nutrient catch crop. Wheat enhances cycling of reduced wind erosion N, P and K. A heavy N feeder in spring, wheat and scavenged N takes up N relatively slowly in autumn. It adds up, from 5 feet deep in however. A September-seeded stand absorbed 40 the profile (111, lb. N/A by December, a Maryland study showed 114). (46). As an overwintering cover rather than a grain • In parts of Zone 6 crop, wheat wouldn’t need fall or spring fertilizer. and warmer, you A 50 bushel wheat crop can take up 20 to 25 also have a depend- lb. P2O5 and 60 lb. K2O per acre by boot stage. able double-crop About 80 percent of the K is recycled if the stems option. See Wheat

and leaves aren’t removed from the field at har- Boosts Income Sears Elayne vest. All the nutrients are recycled when wheat is and Soil Protection WINTER WHEAT managed as a cover crop, giving it a role in scav - (p. 113). (Triticum aestivum) enging excess nitrogen. “Cash and Cover” crop. Winter wheat can be Weed suppressor. As a fall-sown cereal, wheat grown as a cash crop or a cover crop, although competes well with most weeds once it is estab - you should manage each differently. It provides a lished (71). Its rapid spring growth also helps cash-grain option while also opening a spot for a choke weeds, especially with an underseeded winter annual legume in a corn>soybean or simi- legume competing for light and surface nutrients. lar rotation. For example: Soil builder and organic matter source. • In the Cotton Belt, wheat and crimson clover Wheat is a plentiful source of straw and stubble. would be a good mix. Wheat’s fine root system also improves topsoil • In Hardiness Zone 6 and parts of Zone 7, plant tilth. Although it generally produces less than rye hairy vetch after wheat harvest, giving the or barley, the residue can be easier to manage and legume plenty of time to establish in fall. Vetch incorporate. growth in spring may provide most of the N When selecting a locally adapted variety for use nec essary for heavy feeders such as corn, or as a cover crop, you might not need premium all of the N for sorghum, in areas northward to seed. A Maryland study of 25 wheat cultivars southern Illinois, where early spring warm-up showed no major differences in overall biomass allows time for development. production at maturity (92). Also in Maryland, • In much of Zone 7, cowpeas would be a good wheat produced up to 12,500 lb. biomass/A choice after wheat harvest in early July or following high rates of broiler litter (87). before planting winter wheat in fall. In Colorado, wheat planted in August after early • In the Corn Belt and northern U.S., undersow vegetables produced more than 4,000 lb. bio- red clover or frostseed sweetclover into a mass/A, but if planted in October, yielded only wheat nurse crop if you want the option of a one-tenth as much biomass and consequently year of hay before going back to corn. With or scavenged less N (114).

112 MANAGING COVER CROPS PROFITABLY Wheat Boosts Income and Soil Protection

Wheat is an ideal fall cover crop that you can Disease or pests rarely have been a problem, later decide to harvest as a cash crop, cotton he notes. farmer Max Carter has found. “It’s easier to “It’s a very easy system, with wheat always manage than rye, still leaves plenty of residue serving as a fall cover crop for us. It builds soil to keep topsoil from washing away—and is and encourages helpful soil microorganisms. an excellent double crop,” says Carter. It can be grazed, or we can burn some down The southeastern Georgia farmer no-till in March for planting early corn or peanuts drills winter wheat at 2 bushels per acre right anytime from March to June,” he says. after cotton harvest, without any seedbed For a double crop before 2-bale-an-acre preparation. “It gives a good, thick stand,” he cotton, Carter irrigates the stand once in says. spring with a center pivot and harvests 45- “We usually get wheat in by Thanksgiving, to 60-bushel wheat by the end of May. “The but as long as it’s planted by Christmas, I chopper on the rear of the combine puts the know it’ll do fine,” he adds. After drilling straw right back on the soil as an even blanket wheat, Carter goes back and mows the cotton and we’re back planting cotton on June 1.” stalks to leave some field residue until the “It sure beats idling land and losing topsoil.” wheat establishes.

If weed control is important in your system, avoid pulverizing topsoil (358) and depleting soil look for a regional cultivar that can produce early moisture. spring growth. To scavenge N, select a variety with good fall growth before winter dormancy. Winter annual use. Seed from late summer to early fall in Zone 3 to 7—a few weeks earlier than MANAGEMENT a rye or wheat grain crop—and from fall to early winter in Zone 8 and warmer. If you are consider- Establishment & Fieldwork ing harvesting as a grain crop, you should wait Wheat prefers well-drained soils of medium tex - until the Hessian fly-free date, however. If cover ture and moderate fertility. It tolerates poorly crop planting is delayed, consider sowing rye drained, heavier soils better than barley or oats, instead. but flooding can easily drown a wheat stand. Rye Drill 60 to 120 lb./A (1 to 2 bushels) into a firm 1 1 may be a better choice for some poor soils. seedbed at a /2- to 1 /2-inch depth or broadcast 60 Biomass production and N uptake are fairly to 160 lb./A (1 to 2.5 bushels) and disk lightly or slow in autumn. Tillering resumes in late win - cultipack to cover. Plant at a high rate if seeding ter/early spring and N uptake increases quickly late, when overseeding into soybeans at the leaf- during stem extension. yellowing stage, when planting into a dry seedbed Adequate but not excessive N is important dur - or when you require a thick, weed-suppressing ing wheat’s early growth stages (prior to stem stand. Seed at a low to medium rate when soil growth) to ensure adequate tillering and root moisture is plentiful (71). growth prior to winter dormancy. In low-fertility After cotton harvest in Zone 8 and warmer, or light-textured soils, consider a mixed seeding no-till drill 2 bushels of wheat per acre without any with a legume (80). See Wheat Offers High Value seedbed preparation. In the Southern Plains, 1 bushel Weed Control, Too (p. 114). is sufficient if drilling in a timely fashion (302). A firm seedbed helps reduce winterkill of With irrigation or in humid regions, you could wheat. Minimize tillage in semiarid regions to harvest 45- to 60- bushel wheat, then double crop

WINTER WHEAT 113 Wheat Offers High-Value Weed Control

Pairing a winter wheat cover crop with a 90 lb./A into a good seedbed, generally in mid- reduced herbicide program in the inland September in Idaho. “In our area, growers can Pacific Northwest could provide excellent deep rip in fall, disk and build the beds (hills), weed control in potatoes grown on light soils then drill wheat directly into the beds,” she in irrigated, semiarid regions. A SARE-funded says. Some starter N (50 to 60 lb./A) can help study showed that winter wheat provided the wheat establish. If indicated by soil testing, effective competition against annual weeds P or K also would be fall-applied for the that infest irrigated potato fields in following potato crop. Washington, Oregon and Idaho. The wheat usually does well and shows Banding herbicide over the row when good winter survival. Amount of spring rainfall planting potatoes improved the system’s and soil moisture and the wheat growth rate effectiveness, subsequent research shows, says determine the optimal dates for killing wheat project coordinator Dr. Charlotte Eberlein at and planting potatoes. the University of Idaho’s Aberdeen Research Some years, you might plant into the wheat and Extension Center. “In our initial study, we and broadcast Roundup about a week later. were effectively no-tilling potatoes into the Other years, if a wet spring delays potato Roundup-killed wheat,” says Eberlein. “In this planting, you could kill wheat before it gets study we killed the cover crop and planted out of hand (before the boot stage), then wait potatoes with a regular potato planter, which for better potato-planting conditions. rips the wheat out of the potato row.” A Moisture management is important, grower then can band a herbicide mixture especially during dry springs, she says. “We over the row and depend on the wheat mulch usually kill the wheat from early to mid May— to control between-row weeds. a week or two after planting potatoes. That’s “If you have sandy soil to start with and can soon enough to maintain adequate moisture in kill winter wheat early enough to reduce the hills for potatoes to sprout.” water-management concerns for the potatoes, An irrigation option ensures adequate soil the system works well,” says Eberlein. moisture—for the wheat stand in fall or the “Winter rye would be a slightly better cover potato crop in spring, she adds. “You want a crop for suppressing weeds in a system like good, competitive wheat stand and a vigorous this,” she notes. “Volunteer rye, however, is a potato crop if you’re depending on a banded serious problem in wheat grown in the West, herbicide mix and wheat mulch for weed and wheat is a common rotation crop for control,” says Eberlein. That combination gives potato growers in the Pacific Northwest.” competitive yields, she observes, based on She recommends drilling winter wheat at research station trials. with soybeans, cotton or another summer crop. Mixed seeding or nurse crop. Winter wheat See Wheat Boosts Income and Soil Protection works well in mixtures with other small grains or (p. 113). You also could overseed winter wheat with legumes such as hairy vetch. It is an excel- prior to cot ton defoliation and harvesting. lent nurse crop for frostseeding red clover or Another possibility for Zone 7 and cooler: Plant sweetclover, if rainfall is sufficient. In the Corn full-season soybeans into wheat cover crop Belt, the legume is usually sown in winter, before residue, and plant a wheat cover crop after bean wheat’s vegetative growth resumes. If frostseed- harvest. ing, use the full seeding rates for both species,

114 MANAGING COVER CROPS PROFITABLY according to recent work in Iowa (34). If you sow Because of its slower spring Wheat is less growth, there is less need to sweetclover in fall with winter wheat, it could likely than outgrow the wheat. If you want a grain option, rush to kill wheat in spring as that could make harvest difficult. is sometimes required for barley or rye rye. That’s one reason veg- to become a Spring annual use. Although it’s not a common etable grower Will Stevens of practice, winter wheat can be planted in the Shoreham, Vt., prefers wheat weed, and is spring as a weed-suppressing companion crop or to rye as a winter cover on his early forage. You sacrifice fall nutrient scavenging, heavy, clay-loam soils. The easier to kill. however. Reasons for spring planting include win- wheat goes to seed slower and ter kill or spotty overwintering, or when you just can provide more biomass didn’t have time to fall-seed it. It won’t have a than an earlier killing of rye would, he’s found. With chance to vernalize (be exposed to extended cold rye, he has to disk two to three weeks earlier in after germination), so it will not head out and usu- spring to incorpo rate the biomass, which can be a ally dies on its own within a few months, without problem in wet conditions. “I only chisel plow setting seed. This eliminates the possibility of it wheat if it’s really rank,” he notes. becoming a weed problem in subsequent crops. By sow ing when field conditions permit in early Pest Management spring, within a couple months you could have a Wheat is less likely than rye or barley to become 6- to 10-inch tall cover crop into which you can a weed problem in a rotation, but is a little more no-till your cash crop. You might not need a burn- susceptible than rye or oats to insects and dis ease. down herbicide, either. Managed as a cover crop, wheat rarely poses an Early spring planting of spring wheat, with or insect or disease risk. Diseases can be more of a without a legume companion, is an option, espe- problem the earlier wheat is planted in fall, especially if you have a longer rotation niche available. cially if you farm in a humid area. Growing winter wheat could influence the Field Management buildup of pathogens and affect future small-grain You needn’t spring fertilize a winter wheat stand cash crops, however. Use of resistant vari eties and being grown as a cover crop rather than a grain other IPM practices can avoid many pest prob- crop. That would defeat the primary purpose (N- lems in wheat grown for grain. If wheat diseases scavenging) of growing a small grain cover crop. or pests are a major concern in your area, rye or As with any overwintering small grain crop, how- barley might be a better choice as an overwinter- ever, you will want to ensure the wheat stand ing cover crop that provides a grain option, doesn’t adversely affect soil moisture or nutrient despite their lower grain yield. availability for the following crop. Other Options Killing Choosing wheat as a small-grain cover crop offers Kill wheat with a roller crimper at soft-dough the flexibility in late spring or early summer to stage or later, with a grass herbicide, or by plow- harvest a grain crop. Spring man agement such as ing, disking or mowing before seed matures. As removing grazing livestock prior to heading and with other small grain cover crops, it is safest to topdressing with N is essential for the grain crop kill about 2-3 weeks before planting your cash option. crop, although this will depend on local conditions and your killing and tillage system. Seed sources. See Seed Suppliers (p. 195).

WINTER WHEAT 115 OVERVIEW OF LEGUME COVER CROPS

Commonly used legume cover crops include: cash crops, these forage crops also can be used for • Winter annuals, such as crimson clover, hairy more than one year and often are harvested for vetch, field peas, subterranean clover and feed during this time. They can be established many others along with—or overseeded into—other crops • Perennials like red clover, white clover and such as wheat or oats, then be left to grow after some medics cash crop harvest and used as a forage. Here they • Biennials such as sweetclover are functioning more as a rotation crop than a • Summer annuals (in colder climates, the win - cover crop, but as such provide many benefits ter annuals are often grown in the summer) including erosion and weed control, organic mat - ter and N production. They also can break weed, Legume cover crops are used to: disease and insect cycles. • Fix atmospheric nitrogen (N) for use by Summer-annual use of legume crops includes, subse quent crops in colder climates, the use of the winter-annual • Reduce or prevent erosion crops listed above, as well as warm-season • Produce biomass and add organic matter to legumes such as cowpeas. Grown as summer the soil annuals, these crops produce N and provide • Attract beneficial insects ground cover for weed and erosion control, as well as other benefits of growing cover crops. Legumes vary widely in their ability to prevent Establishment and management varies widely erosion, suppress weeds and add organic matter depending on climate, cropping system and the to the soil. In general, legume cover crops do not legume itself. These topics will be covered in the scavenge N as well as grasses. If you need a cover individual sections for each legume. crop to take up excess nutrients after manure or Legumes are generally lower in carbon and fertilizer applications, a grass, a brassica or a mix- higher in nitrogen than grasses. This lower C:N ture is usually a better choice. ratio results in faster breakdown of legume Winter-annual legumes, while established in residues. Therefore, the N and other nutrients con- the fall, usually produce most of their biomass and tained in legume residues are usually released N in spring. Winter-annual legumes must be plant - faster than from grasses. Weed control by legume ed earlier than cereal crops in order to survive the residues may not last as long as for an equivalent winter in many regions. Depending on your cli - amount of grass residue. Legumes do not increase mate, spring management of legumes will often soil organic matter as much as grasses. involve balancing early planting of the cash crop Mixtures of legume and grass cover crops com - with waiting to allow more biomass and N pro - bine the benefits of both, including biomass pro - duction by the legume. duction, N scavenging and additions to the Perennial or biennial legumes can fit many dif - system, as well as weed and erosion control. Some ferent niches, as described in greater detail in the cover crop mixtures are described in the individ - individual sections for those cover crops. ual cover crop sections. Sometimes grown for a short period between

116 MANAGING COVER CROPS PROFITABLY COVER CROP MIXTURES EXPAND POSSIBILITIES

ixtures of two or more cover crops are come on strong. Because they reseed themselves, often more effective than planting a sin- the cooperative trio persists year after year. Mgle species. Cover crop mixtures offer Sometimes you don’t know how much N may the best of both worlds, combining the benefits of be left after cash crop harvest. Do you need a grass grasses and legumes, or using the different growth to scavenge leftover N, or a legume to pro vide fixed characteristics of several species to fit your needs. N? A grass/legume cover crop mixture adjusts to You can use cover crop mixtures to improve: the amount of available soil N: If there is a lot of N, • Winter survival the grass dominates; if there is not much available • Ground cover soil N, the legume will tend to dominate a mixture. • Use of solar energy In either case, you get the combined benefit of N • Biomass and N production scavenging by the grass cover crop and N additions • Weed control from the legume cover crop. • Duration of active growing period Mixing low-growing and taller crops, or fast- • Range of beneficial insects attracted starting grasses and slow-developing legumes, • Tolerance of adverse conditions usually provides better erosion control because • Forage options more of the ground is covered. The vegetation • Response to variable soil traits intercepts more raindrops before they can dislodge soil particles. Sunlight is used more effi - Disadvantages of cover crop mixtures may ciently because light that passes through the tall include: crop is captured by the low-growing crop. • Higher seed cost Adding grasses to a fall-seeded legume • Too much residue improves soil coverage over winter and increases • More complicated management the root mass to stabilize topsoil. A viny crop like • Difficult to seed vetch will climb a grass, so it can get more light and fix more N, or so it can be harvested more Crop mixtures can reduce risk in cropping sys - easily for seed. A faster-growing crop serves as a tems because each crop in the mix may respond nurse crop for a slow-growing crop, while cover - differently to soil, pest and weather conditions. In ing the ground quickly for erosion control. The forage or grazing systems, for example, a mix of possibilities are endless! rye, wheat and barley is more nutritious, can be Mixtures can complicate management, how - grazed over a longer period of time and is less ever. For example: likely to be devastated by a single disease. • They may cost more to seed. Seeding rates for Using drought-tolerant plants in a perennial each component of the mix are usually lower mix builds in persistence for dry years. Using a than for sole-crop plantings, but the total seed number of cover crops with “hard seed” that takes cost may still be more. many months to germinate also improves cover - • The best time to kill one crop may not be the age over a broader range of conditions. best for another crop, so a compromise date Mixing cultivars of a single species with varied may be used. maturity dates and growth habits maintains opti - • If you use herbicides, your choices may be mum benefits for a longer time. Orchardists in lim ited when you plant a mixture of legumes California mix subclovers to keep weeds at bay all and nonlegumes. season. One cultivar comes on early, then dies back • Sometimes you can end up with more residue as two later cultivars—one tall and one short— than your equipment can handle.

COVER CROP MIXTURES 117 The benefits of a mixture will usually outweigh tures, and create your own tailor-made mixtures. these disadvantages, but you need to be prepared to Remember that adding another crop increases manage the mixture carefully to prevent problems. the diversity on your farm, and is likely to increase Each cover crop chapter gives examples of spe - the many proven benefits of rotations over cific mixtures that have been tested and work monocropping. well. Try some of the proven cover crop mix-

BERSEEM CLOVER Trifolium alexandrinum

Also called: Egyptian clover

Type: summer annual or winter annual legume

Roles: suppress weeds, prevent erosion, green manure, chopped forage, grazing

Mix with: oats, ryegrass, small grains as nurse crops; as nurse crop for alfalfa

See charts, p. 66 to 72, for ranking and management summary.

fast-growing summer annual, berseem growth period during the West Coast’s rainy sea - clover can produce up to 8 tons of forage son and its highly efficient water use compare Aunder irrigation. It’s a heavy N producer favorably to alfalfa as a high-producing forage and and the least winter hardy of all true annual green manure. clovers. This makes it an ideal winterkilled cover before corn or other nitrogen-demanding crops in BENEFITS Corn Belt rotations. Berseem clover draws down soil N early in its cycle. Once soil reserves are Green manure. Berseem clover is the fertility used up, it can fix 100 to 200 lb. N/A or more. It foundation of agriculture in the Nile Delta, and establishes well with an oat nurse crop, making it has nourished soils in the Mediterranean region an excellent cover for small grain>corn>soybean for millennia. MULTICUT berseem clover averaged rotations in the Midwest. 280 lb. N/A in a six-year trial in California with six In Iowa, the cultivar BIGBEE compares favorably cuttings per year (162), and grew faster than with alfalfa in its regrowth following small grain BIGBEE in one Iowa report (155). Berseem is less harvest, its feed value and its tolerance to drought prone to possible N leaching if grown to maturi ty and excess moisture (156). As a winter annual in without cutting, when it produces 100 to 125 lb. California, irrigation usually is needed to allow N/A. Top N fixation occurs when soils have less berseem to achieve its full potential. Its peak than 150 lb. N/A (162). A single cutting can yield

118 MANAGING COVER CROPS PROFITABLY 50 to 100 lb. topgrowth N/A. Berseem’s dry mat- Grazing and forage crop. At 18 to 28 percent ter N concentration is about 2.5 percent (162). protein, young berseem clover is comparable to or better than crimson clover or alfalfa as feed. Biomass. Berseem clover produced the most No cases of bloat from grazing berseem clover biomass (6,550 lb./A) of five winter annual have been reported (158, 278). Forage quality legumes in a two-year Louisiana test, and came in remains accept able until the onset of seed second to arrowleaf clover (Trifolium vesiculo - pro duction. BIGBEE berseem clover and TIBBEE sum) in N, accumulating 190 lb. N/A to crimson produce more fall and winter growth arrowleaf’s 203 lb. N/A. Also tested were TIBBEE than do other winter annual clovers in the crimson clover, WOOGENELUP subterraneum South. BIGBEE con - clover and WOODFORD bigflower vetch. All but tinues pro ducing MULTICUT berseem arrowleaf clover were able to set seed by May 13 longer into the and regrow in the fall, despite the herbicides used spring than other clover averaged 280 to suppress them in spring and to control weeds legumes, extending lb. N/A in a six-year during summer (36). cuttings into late In Alberta legume trials, berseem clover aver- May or early June in California trial. aged 3,750 lb. dry matter/A over three years at a Mississippi (225). site where hairy vetch and field peas produced 5,300 and 4,160 lb./A, respectively. With irriga- MANAGEMENT tion, berseem clover topped 19 other legumes at the same site with a mean yield of 5,500 lb. DM/A. Establishment Berseem prefers slightly alkaline loam and silty Smother crop. Planted with oats or annual rye- soils but grows in all soil types except sands. grass, berseem clover suppresses weeds well dur- Soil phosphorus can limit berseem clover ing establishment and regrowth after oat harvest. growth. Fertilize with 60 to 100 lb. P2O5/A if soil tests below 20 ppm (162). Boron also Companion crop. Planted with oat, the two may limit growth, so test soil to maintain levels crops can be harvested together as silage, haylage (278). Berseem tolerates saline conditions better or hay, depending on the crop’s development than alfalfa and red clover (120). Use R-type stage. Berseem/oat haylage has very high feed inoculant suitable for berseem clover and crim- quality if cut at oats’ boot stage (157). Dry seasons son clovers. favor development of an oat grain crop, after Broadcast or drill berseem seed alone or with which berseem clover can be cut one, two or spring grains onto a firm, well-prepared seedbed three times in the Midwest. or closely cropped sod so that it is 1/4-inch deep with a light soil covering. To improve seed-soil Quick growing. At 60° F, berseem clover will be contact and to maintain seed-zone moisture, culti- ready to cut about 60 days after planting. pack or roll soil before and after broadcast seeding (162). Dry, loose soil will suppress germi- Legume nurse crop. Because of its quick germination. nation (seven days), quick growth and win- Recommended seeding rates are 8 to 12 lb./A terkilling tendency, berseem clover can be used as drilled or 15 to 20 lb./A broadcast. Excessive rates a nurse crop for alfalfa. will create an overly thick stand that prevents tillering and spreading of the root crowns. Seed crop. Berseem produces up to 1,000 lb. Montana trials set the optimum seeding rate at seed/A if it is left to mature. Only BIGBEE berseem about 8 lb./A drilled in 12-inch rows, with a high - clover has hard seed that allows natural self- er rate in narrower rows where herbicides are not reseeding, and it reseeds too late for timely plant - used to control weeds (442). ing of most summer crops (103).

BERSEEM CLOVER 119 grow about 15 inches before frost, provide winter erosion protection and break down quickly in spring to deliver N from its topgrowth and roots. You can overseed berseem clover into standing small-grain crops, a method that has worked well in a series of on-farm tests in Iowa (155). Plant the berseem as late as three weeks after the grain crop germinates or after the tillering stage of win - ter-seeded small grains. Use a heavy seeding rate to compensate for reduced seed-soil contact. Frostseeding in late winter into winter wheat has not worked in several attempts in Pennsylvania (361) and Iowa.

Southeast. Fall planting in mild regions provides

Marianne Sarrantonio Marianne effective weed control as well as N and organic BERSEEM CLOVER (Trifolium alexandrinum) matter for a spring crop. Seed Aug. 25 to Oct. 15 in Mississippi or up to Dec.1 in Florida. For a cool- Midwest. Seed after April 15 to avoid crop loss season grass mixture, plant 12 lb. berseem clover due to a late frost. Berseem frostseeded at 15 lb./A seed with 10 lb. orchardgrass or 20 lb. annual or yields well in the upper Midwest. In southern perennial ryegrass/A (225). Michigan, frostseeded berseem clover produced 1.5 T dry matter/A and 85 lb. N/A (373, 376), but West. Berseem does best in California’s Central frost risk is significant. Valley when planted by the first or second week Iowa tests over four years showed that inter- of October. If planting is delayed until November, seeded berseem and oats averaged 76 percent seedlings will start more slowly in the cool of more dry matter (ranging from 19 to 150 percent) winter (162). than oats alone. Underseeding berseem clover did not significantly reduce oat yields in another Iowa Field Management study. Seed early- to mid-April in Iowa (159). Mowing for green manure. Clip whenever When seeding a mixture, harvest goals affect plants are 12 to 15 inches tall and basal shoots variety selection and seeding rates, Iowa research - begin to grow. This will be 30 to 60 days after ers have found. If establishment of an optimum planting, depending on weather, field and mois - berseem clover stand for green manure is most ture conditions. Mow again every 25 to 30 days to important, oat or other small grain crop seeded at encourage growth of up to 4 T/A. Keep stubble about 1 bushel per acre will protect the young height at least 3 to 4 inches tall, because plants clover and help to break the soil crust. If early regrow from lower stem branches. forage before green manuring is the goal, seed a To maximize dry matter production, cut as soon mixture of 4 bu. oats and 15 lb.berseem/A. If as basal bud regrowth reaches 2 inches (162). At bio mass quantity is foremost, use a short- the latest, clip before early flowering stage or plants stalked, long-season oat. If oat grain production is will not regrow. Berseem clover responds best primary, keep oat seeding rate the same, but when field traffic is minimized (156). select a short-season, tall variety to reduce the Mowed berseem clover left in the field as green likelihood of berseem clover interfering with manure can hinder regrowth of the legume from grain harvest (156). its lower stems. To lessen this problem, flail or Berseem clover also can be a late-summer crop. sickle-bar mow then rake or fluff with a tedder at Planted in mid-August in the Corn Belt, it should intervals until regrowth commences.

120 MANAGING COVER CROPS PROFITABLY Remember that berseem clover has a tap root Killing and shallow 6- to 8-inch feeder root system (156). Berseem dies when exposed to temperatures be - In thin plantings or well-drained soils, it can be low 20° F for several days, making winterkill a vir- susceptible to drought, a trait that could trigger tu al certainty in Zone 7 and colder. This eliminates mowing, grazing or killing earlier than originally the need for herbicides or mechanical killing after planned (186). a cold winter, and hastens delivery of nutrients to Abundant soil N will restrict N fixation by the soil. berseem clover, but moderate amounts up to 150 To kill berseem lb. N/A did not limit annual fixation in north cen - clover ahead of fall- The least winter hardy tral California. Researchers explain that berseem planted crops, wait clover draws heavily on soil N during early for it to die after of the true annual growth. When soil N was depleted in this test, blooming, use mul- clovers, berseem can berseem began fixing N rapidly until it produced tiple diskings or seed and died (447). apply herbicides. be planted with oats Berseem made its N contribution to soil in the In mild areas, ber - in the Corn Belt and final third of its cutting cycle—regardless of initial seem clover grows soil N availability—in all six years of the study. vigorously through produce abundant N Nitrogen fixation was closely correlated to a drop late spring. BIGBEE in water-use efficiency in the trial. After produc- berseem clover re - before winterkilling. ing from 400 to 640 lb. of dry matter per acre-inch mained vegetative of water in the first four cuttings, production until early May or dropped to 300 lb. DM/A-in. for the final two cut- later in an experiment at a northern Mississippi tings (447). (Zone 7) site. Until it reaches full bloom, it will require either tillage or a combination of herbi cides Small grain companion. Underseeded and mechanical controls to kill it. berseem clover provided about 1.2 T forage dry In a northern Mississippi mechanical control matter/A after oat harvest in Iowa. Removing the study, BIGBEE berseem clover added the most dry forage decreases the soil-saving ground cover and matter after mid-April compared to hairy vetch, N con tribution (159), trading soil and N benefits MT. BARKER subterranean clover and TIBBEE crim - for attractive near-term income. son clover. Berseem and hairy vetch remained In the Midwest, greenchop an oat/berseem vegetative until mid-May, but by early May, ber - clover mixture when oat is at the pre-boot stage seem clover and crimson had a considerable to avoid berseem clover going to seed early and, amount of stems laying down (105). therefore, not producing maximum nitrogen. Oats Rolling with 4-inch rollers killed less berseem have high crude protein at this stage. Monitor clover than hairy vetch or crimson when the carefully during warm periods to avoid nitrogen legumes had more than 10 inches of stem laying tox icity. on the ground. Kill rate was more than 80 per- A Montana study found that spring plantings of cent for the latter two crops, but only 53 percent berseem clover will produce the most legume dry for berseem clover. Without an application of matter and N if clear seeded. If, however, you wish atrazine two weeks prior to either flail mowing to maximize total dry matter and protein, seeding or rolling with coulters, the mechanical controls with oats is recommended. The oat nurse crop failed to kill more than 64 percent of the suppressed weeds well and increased total dry berseem clover until early May, when flailing matter production by 50 to 100 percent regard- achieved 93-percent control. Atrazine alone less of whether plots were cut two, three or four reduced the stand by 68 percent in early April, times (434). 72 percent in mid-April and 88 percent in early May (105).

BERSEEM CLOVER 121 Nodulation: Match Inoculant to Maximize N

With the help of nitrogen-fixing bacteria, The rate of N fixation is determined largely legume cover crops can supply some or all by the genetic potential of the legume species of the N needed by succeeding crops. This and by the amount of plant-available N in the nitrogen-producing team can’t do the job right soil. Other environmental factors such as heat unless you carefully match the correct and moisture play a big role, as well. Fueling N bacterial inoculant with your legume cover fixation is an expensive proposition for the crop species. legume host, which may contribute up to 20 Like other plants, legumes need nitrogen to percent of its carbohydrate production to the grow. They can take it from the soil if enough root-dwelling bacteria. If the legume can take is present in forms they can use. Legume roots up free N from the soil, it won’t put as much also seek out specific strains of soil-dwelling energy into producing nodules and feeding bacteria that can “fix” nitrogen gas from the bacteria to fix nitrogen from the air. air for use by the plant. While many kinds of Perennial legumes fix N during any time of bacteria compete for space on legume roots, active growth. In annual legumes, N fixation the root tissues will only begin this symbiotic peaks at flowering. With seed formation, it N-fixing process when they encounter a ceases and the nodules slough from the roots. specific species of rhizobium bacteria. Only Rhizobia return to the soil environment to particular strains of rhizobia provide optimum await their next encounter with legume roots. N production for each group of legumes. These bacteria remain viable in the soil for When the root hairs find an acceptable three to five years, but often at too low a level bacterial match, they encircle the bacteria to to provide optimum N-fixation when legumes create a nodule. These variously shaped lumps return to the field. on the root surfaces range in size from a BB If legume roots don’t encounter their ideal pellet to a kernel of corn. Their pinkish bacterial match, they work with the best interiors are the visible sign that nitrogen strains they can find. They just don’t work as fixation is at work. efficiently together and they produce less N. Nitrogen gas (N2) from air in the spaces Inoculating seeds with the correct strain between soil particles enters the nodule. The before planting is inexpensive insurance bacteria contribute an enzyme that helps to make sure legumes perform up to their convert the gas to ammonia (NH3). The plant genetic potential. Clover inoculum, for uses this form of N to make amino acids, the example, costs just a few cents per pound of building blocks for proteins. In return, the host seed treated, or more for an enhanced sticker legume supplies the bacteria with that buffers and feeds the seedling. carbohydrates to fuel the N-fixation process.

Pest Management nation and seedling development of onion, carrot Avoid direct seeding small-seeded vegetables into and tomato, based on lab tests (40). fields where you have incorporated berseem Lygus bugs have been a serious problem in clover within the past month, due to allelopathic California seed production, and virus outbreaks compounds in the residue. Berseem clover, crim- can cause serious damage during wet springs son clover and hairy vetch residue incorporat ed where berseem grows as a winter annual. Where directly into the seed zone may suppress germi - virus is a concern, use JOE BURTON, a resistant cul-

122 MANAGING COVER CROPS PROFITABLY While they are alive, legumes release little not expose packages or inoculated seed to or no nitrogen to the soil. The N in their roots, excessive heat or direct sunlight. stalks, leaves and seeds becomes available when the plants die naturally or are killed by Mix the sticker with non-chlorinated water tillage, mowing or herbicide. This plant and add the inoculant to create a slurry, then material becomes food for microbes, worms, thoroughly coat seeds. Seed should be dry insects and other decomposers. enough to plant within half an hour. Microorganisms mineralize, or convert, the Re-inoculate if you don’t plant the seed within complex “organic” forms of nitrogen in the 48 hours. Mix small quantities in a five-gallon plant material into inorganic ammonium and bucket or tub, either by hand or using a drill nitrate forms, once again making the N equipped with a paint-mixer attachment. For available to plants. How quickly the larger quantities, use special inoculant mixing mineralization of N occurs is determined by hoppers or a cement mixer without baffles. a host of environmental and chemical factors. Gum arabic stickers with sugars and liming These will affect how much of that legume N agents boost the chances for optimum is available to the next crop or has the nodulation over water-applied inoculant alone. potential to leach from the soil. Pre-inoculated (“rhizo-coated”) seed weighs For more information about mineralization about one-third more than raw seed, so and how much you can reduce your N increase seeding rates accordingly. fertilizer rate for crops following legumes, see Check nodulation as the plants approach How Much N? (p. 22). bloom stage. Push a spade in the soil about 6 To get the most from your legume/bacteria inches below the plant. Carefully lift the plant combination: and soil, gently exposing roots and nodules. • Choose appropriate legume species for (Yanking roots from the soil usually strips off your climate, soils and cropping system. nodules).Wash gently in a bucket of water to Also, consider the amount of N it can see the extent of nodulation. Slice open deliver when you will need it. nodules. A pink or reddish interior indicates • Match inoculant to the species of legume active N-fixation. Remember, an you are growing. See Chart 3B, Planting overabundance of soil nitrogen from fertilizer, (p. 70) to determine the best inoculant to use. manure or compost can reduce nodulation. • Coat seed with the inoculant just before For more information about nodulation, see planting. Use milk, weak sugar water or a two books by Marianne Sarrantonio: Northeast commercial sticking agent to help the material Cover Crop Handbook (361) and stick to the seeds. Use only fresh inoculant Methodologies for Screening Soil-Improving (check the package’s expiration date), and do Legumes (360). tivar. BIGBEE is susceptible to crown rot and other Crop Systems root diseases common to forage legume species Flexible oats booster. In the Corn Belt, berseem (162). clover seeded with oats helps diversify corn>soy - Berseem, like other clovers, shows little resis - bean rotations, breaks pest cycles and provides tance to root-knot nematode (Meloidogyne spp.). some combination of grain and/or forage harvest, It seems to be particularly favored by rabbits erosion control and N to the following corn crop. (361). An added benefit is that it requires no tillage or herbicide to kill it in spring (159). Plant 4 bu. oats with 12 lb. berseem/A.

BERSEEM CLOVER 123 In a four-year Iowa study, planting berseem Vegetable overseeding. Berseem can be over- clover with oats increased net profit compared seeded into spring vegetables in northern cli- with oats alone. The clover was baled for forage mates where it thrives at moderate tempera tures and the underseeded oats were har vested for and moisture. Berseem is well suited to a “mow grain. Not calculated in the benefit were the 40 and blow” system where strips of green manure to 60 lb. N/A provided to the follow ing corn are chopped and transferred to adjacent crop crop or other soil-improvement benefits. The strips as a green manure and mulch (361). oats/ berseem mix pro- Boost the N plow-down potential of old pas- Mow strips of duced 70 percent more tures or winter-killed alfalfa by no-tilling or inter- bio mass, increased sub- berseem between seeding berseem clover. Or, broadcast seed then sequent corn yields by incorporate with light harrowing. vegetable rows 10 percent and reduced weed competition com- COMPARATIVE NOTES and blow the pared with a year of clippings around oats alone (159). Berseem clover is: Pure berseem clover • Not as drought-tolerant as alfalfa. Some culti- the plants regrowth averaged 1.2 vars can tolerate more soil moisture—but not T dry matter/A, which waterlogging—than alfalfa or sweet clover for mulch. can be used as forage or • Similar in seed size to crimson clover green manure. These • Bee-friendly because its white or ivory blos - options could help oats soms have no tripping mechanism. become an economically viable crop for Midwest • Because of its short roots, berseem clover crop/live stock farms in an era of decreasing does not use phosphorus to the depth that government payments for corn and soybeans mature, perennial alfalfa does. (159, 160). • Winterkilled berseem allows for earlier spring planting than winter-hardy annuals. As a dead Wheat companion. Berseem was one of six organic mulch, it poses no moisture depletion legume intercrops that improved productivity risk, but may slow soil warming and drying and profit of wheat and barley crops in low-N compared to erosion-prone bare fallow. soils under irrigated conditions in northwestern Mexico. All of the legumes (including common Cultivars. BIGBEE berseem clover was selected and hairy vetch, crimson clover, New Zealand and from other traditional cultivars for its cold-toler - Ladino white clover, and fava beans) provided ance, which is similar to crimson clover. Some of multiple benefits without decreasing grain yield the strong winter production tendency found in of 15 to 60 bu./A on the heavy clay soil. non-winter hardy berseem clover was sacrificed Wheat and legumes were planted at normal to obtain BIGBEE’s winter hardiness (162). Mature monoculture rates with wheat in double rows BIGBEE plants hold their seeds well and produce about 8 inches apart atop 30-inch beds, and adequate hard seed for reseeding. Other berseem legumes in the furrows. In a second, related clover cultivars have less hard seed and will not experiment, researchers found they could more dependably reseed (278). than double total wheat productivity (grain and California tests show MULTICUT berseem clover total dry matter) by interplanting 24-inch strips of produces 20 to 25 percent more dry matter than berseem clover or hairy vetch with double rows BIGBEE. It has greater N-fixing ability, blooms later, of wheat 8 inches apart. Control plots showed and has a longer growing period than other vari- wheat planted at a greater density did not eties, but is not as cold tolerant as BIGBEE (162). increase yield (350). JOE BURTON, developed from MULTICUT, is more cold tolerant.

124 MANAGING COVER CROPS PROFITABLY In California, BIGBEE begins to flower in mid- MULTICUT was about 6 inches taller at each clip- May, about two weeks ahead of MULTICUT. ping than other varieties (447). In Montana tests, MULTICUT grows faster and pro duces more dry BIGBEE out-yielded MULTICUT in eight of 13 loca- matter in Cali fornia conditions, averaging about tions (381). 1.6 T/A more in a six-year study. When the five or six cuttings per year were clipped and removed, Seed sources. See Seed Suppliers (p. 195).

COWPEAS Vigna unguiculata

Also called: southern peas, blackeye peas, crowder peas

Type: summer annual legume

Roles: suppress weeds, N source, build soil, prevent erosion, forage

Mix with: sorghum-sudangrass hybrid or foxtail hay-type millet for mulch or plow-down before vegetables; interseeded with corn or sorghum

See charts, pp. 66 to 72, for ranking and management summary.

owpeas are the most productive heat- Cowpeas make an excellent N source ahead of adapted legume used agronomically in the fall-planted crops and attract many beneficial CU.S. (275). They thrive in hot, moist zones insects that prey on pests. Used in California in where corn flourishes, but require more heat for vegetable systems and sometimes in tree crops, optimum growth (263). Cowpea varieties have di - cowpeas also can be used on poor land as part of verse growth habits. Some are short, upright bush a soil-building cover crop sequence. types. Taller, viny types are more vigorous and bet - ter suited for use as cover crops. Cowpeas protect BENEFITS soil from erosion, smother weeds and produce 100 to 150 lb. N/A. Dense residue helps to Weed-smothering biomass. Drilled or broad cast improve soil texture but breaks down quickly in cowpea plantings quickly shade the soil to block hot weather. Excellent drought resistance com- out weeds. Typical biomass produc tion is 3,000 to bined with good tolerance of heat, low fertility 4,000 lb./A (361). Cowpeas produced about 5,100 and a range of soils make cow peas viable through- lb. dry matter/A in a two-year Nebraska screening of out the temperate U.S. where summers are warm cover crops while soybeans averaged about 7,800 or hot but frequently dry. lb. DM/A in comparison plots (332).

COWPEAS 125 Thick stands that grow well can outcompete Inter cropping with soybeans also increased para- bermudagrass where it does not pro duce seed sitism of the bollworms compared with plots and has been plowed down before cowpea inter cropped with onions or cotton without an planting (263). In New York, both cowpea and inter crop. No effects on overall aphid, leafhopper soybean provided some weed-suppressing bene- or bollworm populations were observed (422). fits. Neither adequately controlled weeds, but mixing with buckwheat or sorghum-sudangrass Companion crop. Thanks to its moderate shade improved performance as a weed management tolerance and attractiveness to beneficial insects, tool (43). cowpeas find a place in summer cover crop mix - In California, cowpea mulch decreased weed tures in orchards and vineyards in the more tem- pressure in fall-planted lettuce, while incorporat- per ate areas of California. Avoid use under a heavy ed cowpea was less effec- tree canopy, however, as cowpeas are susceptible Cowpeas thrive tive. An excellent desert to mildew if heavily shaded (263). As in much of under hot, moist cover crop, cowpea also the tropical world where cowpeas are a popular reduced weed pressure food crop, they can be underseeded into corn for conditions, but in California pepper pro- late-sea son weed suppression and post-harvest duction (209). soil cover age (361). also tolerate The weed-suppressing drought and low activity of cowpea may Seed and feed options. Cowpea seed (yield be due, in part, to allelo- range 350 to 2,700 lb./A) is valued as a nutrition - soil fertility. pathic compounds in the al supplement to cereals because of complemen - residue. The same com- tary protein types. Seed matures in 90 to 140 days. pounds could adversely Cowpeas make hay or forage of highest feed value impact your main crop. Be sure to consult local when pods are fully formed and the first have information about impacts on cash crops. ripened (120). A regular sickle-bar mower works for the more upright-growing cultivars (120, 422). Quick green manure. Cowpeas nodulate pro- Crimping speeds drying of the rather fleshy stems fusely, producing an average of about 130 lb. N/A to avoid over-drying of leaves before baling. in the East, and 200 lb. N/A in California. Properly Low moisture need. Once they have enough inoculated in nitrogen deficient soils, cowpeas soil moisture to become established, cow peas are can produce more than 300 lb. N/A (120). a rugged survivor of drought. Cowpeas’ delayed Plowdown often comes 60 to 90 days after plant - leaf senescence allows them to survive and recov- ing in California (275). Higher moisture and more er from midseason dry spells (21). Plants can send soil N favor vegetative growth rather than seed taproots down nearly 8 feet in eight weeks to production. Unlike many other grain legumes, reach moisture deep in the soil profile (107). cowpeas can leave a net gain of nitrogen in the field even if seed is harvested (361). Cultivars for diverse niches. Cover crop culti - vars include CHINESE RED, CALHOUN and RED IPM insectary crop. Cowpeas have “extrafloral RIPPER, all viny cultivars noted for superior resis- nectaries”—nectar-release sites on petioles and tance to rodent damage (317). IRON CLAY, a mix- leaflets—that attract beneficial insects, including ture of two formerly separate cultivars widely many types of wasps, honeybees, lady beetles, ants used in the Southeast, combines semi-bushy and and soft-winged flower beetles (422). Plants have viny plants and resistance to rootknot nematodes long, slender round pods often borne on bare and wilt. petioles above the leaf canopy. Most of the 50-plus commercial cowpea culti - Intercropping cotton with cowpeas in India vars are horticultural. These include “crowder increased levels of predatory ladybugs and peas” (seeds are crowded into pods), grown para sitism of bollworms by beneficial wasps. throughout the temperate Southeast for fresh pro-

126 MANAGING COVER CROPS PROFITABLY cessing, and “blackeye peas,” grown for dry seed in California. Watch for the release of new varieties for cover crop use. Use leafy, prostrate cultivars for the best erosion prevention in a solid planting. Cultivars vary sig - nificantly in response to environmental condi - tions. Enormous genetic diversity in more than 7,000 cultivars (120) throughout West Africa, South America and Asia suggests that breeding for forage production would result in improved cultivars (21, 422) and cover crop performance.

Easy to establish. Cowpeas germinate quickly and young plants are robust, but they have more diffi- COWPEAS (Vigna unguiculata) culty emerging from crusted soils than soybeans. Sarrantonio Marianne

MANAGEMENT another warm-season annual legume. See Up-and- Coming Cover Crops (p. 191). Establishment Don’t plant cowpeas until soil temperature is a Field Management consistent 65° F and soil moisture is adequate for Cowpea plants are sometimes mowed or rolled to germination—the same conditions soybeans suppress regrowth before being incorporated for need. Seed will rot in cool, wet soils (107). green manure. It’s best to incorporate cowpeas Cowpeas for green manure can be sown later in while the entire crop is still green (361) for quick- summer (361), until about nine weeks before est release of plant nutrients. Pods turn cream or frost. Cowpeas grow in a range of well-drained brown upon maturity and become quite brittle. soils from highly acid to neutral, but are less well Stems become more woody and leaves eventually adapted to alkaline soils. They will not survive in drop. waterlogged soils or flooded conditions (120). Crop duration and yield are markedly affected In a moist seedbed, drill cowpeas 1 to 2 inches by night and day temperatures as well as day deep at about 30 to 90 lb./A, using the higher rate length. Dry matter production peaks at tempera - in drier or cooler areas or for larger-seeded culti - tures of 81° F day and 72° F night (120). vars (361, 422). While 6- to 7-inch row spacings are best for rapid groundcover or a short growing Killing season, viny types can be planted in 15- to 30-inch Mowing at any point stops vegetative develop - rows. Pay particular attention to pre-plant weed ment, but may not kill plants without shallow control if you go with rows, using pre-cultivation tillage. Mowing and rolling alone do not consis- and/or herbicides. tently kill cowpeas (95). Herb icides can also be If you broadcast seed, increase the rate to about used. If allowed to go to seed, cowpeas can 100 lb./A and till lightly to cover seed. A lower volunteer in subsequent crops. rate of 70 lb./A can work with good moisture and effective incorporation (361). Broadcast seeding Pest Management usually isn’t as effective as drilling, due to cow - Farmers using cowpeas as cover crops do not peas’ large seed size. You can plant cowpeas after report problems with insects that are pests in harvesting small grain, usually with a single disk- commercial cowpea production, such as Lygus ing if weed pressure is low. No-till planting is also bugs and 11-spotted cucumber beetle (95, 83). an option. Use special “cowpea” inoculant which Insect damage to cowpea cover crops is most also is used for sunn hemp (Crotolaria juncea), likely to occur at the seedling stage.

COWPEAS 127 Cowpeas Provide Elegant Solution to Awkward Niche

PARTRIDGE, Kan.—Cowpeas fill a rotational decomposition. He runs an S-tine field rough spot between milo (grain sorghum) and cultivator 1 to 2 inches deep just before wheat for Jim French, who farms about 640 planting wheat to set back fall weeds, targeting acres near Partridge, Kan. a 20 to 25 percent residue cover. The cowpeas “I miss almost a full season after we take off improve rainfall infiltration and the overall the milo in late October or November until we ability of the soil to hold moisture. plant wheat the following October,” says French observes that the timing of rainfall French. “Some people use cash crops such as after cowpea planting largely determines the oats or soybeans. But with cowpeas, I get wind weediness of the cover crop. “If I get a week erosion control, add organic matter to improve to 10 days of dry weather after I plant into soil tilth, save on fertilizer and suppress weeds moisture, the cowpeas will out-compete the for the wheat crop. Plus I have the options of weeds. But if I get rain a few days after haying or grazing.” planting, they’ll be weedy.” He chisel plows the milo stubble in late French manages his legumes to stay in April, disks in May and field cultivates just compliance with USDA farm program before planting about the first week of June. provisions. The Freedom to Farm Act allows He drills 30 to 40 lb./A of CHINESE RED vegetables used as green manure, haying or cowpeas 1 to 2 inches deep when soil grazing to be planted on program acres, but temperature reaches 70° F. Growth is rapid, prohibits planting vegetables for seed harvest and by early August he kills the cowpeas by on those acres. The rules list cowpeas as a making hay, having his cattle graze them off or vegetable, even though different cultivars are by incorporating them for maximum soil used for culinary production. Use of grain benefit. legumes such as lentils, mung beans and dry French says cowpeas usually produce about peas (including Austrian winter peas) is not 90 to 120 lb. N/A—relatively modest for a restricted by the act, opening flexible rotation legume cover—but he feels his soil greatly options. benefits from the residue, which measured French cooperated with Rhonda Janke of 8,000 lb./A in one of his better fields. He disks Kansas State University to define soil health the sprawling, leafy legume once, then does a more precisely. He can tell that covers improve shallow chisel plowing to stop growth and the “flow” of his soil, and he is studying root save moisture. Breakdown of the somewhat growth after covers. But he feels her work tough stems depends on moisture. measuring enzymes and carbon dioxide levels When he leaves all the cowpea biomass in will give farmers new ways to evaluate the field, he disks a second time to speed microbial activity and overall soil health.

Once cowpea plants form pods, they may suppres sion and about 90 percent of their attract stinkbugs, a serious economic pest in parts nitrogen con tribution. However, waiting too of the lower Southeast. However, no significant long before mowing or incorporation will stinkbug presence was reported in three years of flush stinkbugs into adjacent crops. Leaving screening in North Carolina. If stinkbugs are a remnant strips of cowpeas to attract stinkbugs concern, remember these points: may reduce move ment into other crops, as • Flail mowing or incorporating cowpeas at long as the cowpeas keep producing enough pod set will prevent a stinkbug invasion. By new pods until the cash crop is no longer that time, cowpeas can provide good weed threatened.

128 MANAGING COVER CROPS PROFITABLY • Plan crop rotations so the preceding, adjacent Cowpeas can fill a mid- Unlike many and succeeding crops are not vulnerable or summer fallow niche in are resistant to stinkbugs. inland North Carolina grain legumes, • If you plan to use an insecticide to control between spring and sum- cowpeas can another pest, the application may also help mer vegetable crops. A mix man age stinkbugs. of IRON AND CLAY cowpeas leave a net N (50 lb./A) and German mil- gain even if No cowpea cultivar is resistant to root rot, but let (15 lb./A) planted in late there is some resistance to stem rot. Persistent June can be killed mechani- seeds are wet weather before development of the first true cally before no-till trans- leaf and crowding of seedlings due to poor seed planted fall broccoli. In harvested. spacing may increase damping off. To reduce dis- several years of screening ease and nematode risks, rotate with four or five trials at the same sites, cow- years of crops that aren’t hosts. Also plant seed pea dry matter (3,780 lb./A) out yielded soybeans into warm soils and use certified seed of tolerant (3,540 lb. DM/A), but plots of sesbania (Sesbania varieties (107). IRON and other nematode-tolerant exaltata) had top yields at about 5,000 lb. cowpea cultivars reduced soybean cyst and root- DM/A (95). knot nematode levels in greenhouse experiments (422). Despite some research (422) showing an COMPARATIVE NOTES increased nematode risk after cowpeas, California farmers report no such problem. Cowpeas are more drought tolerant than soy - beans, but less tolerant of waterlogging (361) and Crop Systems frost (263). Sown in July, the cowpea canopy Cowpeas’ heat-loving nature makes them an ideal closed more rapidly and suppressed weeds better mid-summer replenisher of soil organic matter than lespedeza (Lespedeza cuneata), American and mineralizable nitrogen. Cowpeas set pods jointvetch (Aeschynomene americana), sesbania over a period of several weeks. Viny varieties con- and alyceclover (Alysicarpus spp.), the other tinue to increase dry matter yields during that warm-season legumes tested (422). Cowpeas per - time. form better than clovers and alfalfa on poor or A mix of 15 lb. cowpeas and 30 lb. buck - acid soils. Cowpea residue breaks down faster wheat/A makes it possible to incorporate the than white sweetclover (361) but not as fast as cover crop in just six weeks while still providing Austrian winter peas. some nitrogen. Replacing 10 percent of the nor- Warm-season alterna tives to cowpeas include mal cowpea seeding rate with a fast-growing, two crops that retain some cowpea benefits. drought-tolerant sorghum-sudangrass hybrid Buckwheat provides good beneficial habitat and increases dry matter production and helps sup - weed control without attracting stinkbugs. port the cowpea plants for mowing. Cowpeas Velvetbeans (Mucuna deeringiana) provide also can be seeded with other tall annu al crops nitro gen, soil protection and late-season forage in such as pearl millet. Overseeding cowpeas into hot, long-season areas. They do not attract nearly mature spring broccoli in June in Zones 5 stinkbugs and are resistant to nematodes (107). and 6 of the Northeast suppresses weeds while improving soil (361). Planting cowpeas in late Cultivars. See Cultivars for diverse niches June or early July in the upper Midwest after (p. 126). spring canning peas pro vides green manure or an emergency forage crop (422). Seed sources. See Seed Suppliers (p. 195).

COWPEAS 129 CRIMSON CLOVER Trifolium incarnatum

Type: winter annual or summer annual legume

Roles: N source, soil builder, ero sion prevention, reseeding inter-row ground cover, forage

Mix with: rye and other cereals, vetches, annual ryegrass, subclover, red clover, black medic

See charts, p. 66 to 72, for ranking and management summary.

ith its rapid, robust growth, crimson Reseeding cultivars provide natural fertility to clover provides early spring nitrogen corn and cotton. Crimson clover works especially Wfor full-season crops. Rapid fall growth, well before grain sorghum, which is planted later or summer growth in cool areas, also makes it a than corn. It is being tested extensively in no-till top choice for short-rotation niches as a weed- and zone-till systems. One goal is to let the legume suppressing green manure. Popular as a staple reseed yearly for no-cost, season-long erosion con- for age and roadside cover crop throughout the trol, weed suppression and nitrogen banking for Southeast, crimson clover is gaining increased the next year. recognition as a versatile summer-annual cover in Along the northern edge of the “crimson clover colder regions. Its spectacular beauty when flow - zone,” winterkill and fungal diseases will be more ering keeps it visible even in a mix with other of a problem. Hairy vetch is the less risky over - flowering legumes, a common use in California wintering winter annual legume, here and in nut groves and orchards. In Michigan, it is used northern areas. Crimson clover often can survive successfully between rows of blueberries. winters throughout the lower reaches of Zone 6, especially from southeastern Pennsylvania north - BENEFITS east to coastal New England (195). Crimson clover is gaining popularity as a win- Nitrogen source. Whether you use it as a spring ter-killed annual, like oats, in Zones 5 and cold er. or fall N source or capitalize on its vigorous Planted in late summer, it provides good ground- reseeding ability depends on your location. cover and weed control as it fixes nitrogen from Growers in the “crimson clover zone”—east of the atmosphere and scavenges nitrogen from the the Mississippi, from southern Pennsylvania and soil. Its winterkilled residue is easy to manage in southern Illinois south—choose winter annual spring. crimson clover to provide a strong, early N boost. In Hardiness Zone 8—the warmer half of the Biomass. As a winter annual, crimson clover can Southeast—crimson clover will overwinter produce 3,500 to 5,500 lb. dry matter/A and fix 70 dependably with only infrequent winterkill. Its N to 150 lb. N/A by mid-May in Zone 8 (the inland contribution is 70 to 150 lb./A. Deep South). In a Mississippi study, crim son clover

130 MANAGING COVER CROPS PROFITABLY had produced mature seed by April 21, as well as 5,500 lb. DM and 135 lb. N/A. The study concluded that crimson clover is one of several winter annual legumes that can provide adequate but not excessive amounts of N for southern grain sorghum production (22, 36, 105). Crimson clover has produced more than 7,000 lb. DM/A several times at a USDA- ARS site in Beltsville, Md., where it produced 180 lb. N and 7,800 lb. DM/A in 1996 (412). In field trials of six annual legumes in Mississippi, crimson clover was found to produce the most dry matter (5,600 to 6,000 lb./A) com - pared to hairy vetch, bigflower vetch, berseem clover, arrowleaf clover (Trifolium vesiculosum)

and winter peas. It produced 99 to 130 lb. N/A Sarrantonio Marianne and is recommended for soil erosion control CRIMSON CLOVER (Trifolium incarnatum) because of its high early-autumn dry matter pro - duction (426). Nutrient cycler. Crimson clover adds to the soil As a summer annual in lower Michigan, a mid - organic N pool by scavenging mineralized N and summer planting of crimson clover seeded at 20 by normal legume N fixation. The scavenging lb./A produced 1,500–2,000 lb. dry matter and 50- process, accomplished most effectively by grass- 60 lb. N/A by late November (270). es, helps reduce the potential for N leaching into groundwater during winter and spring (181, 265). Mixtures. Crimson clover grows well in mixtures Mixed with annual ryegrass in a simulated rainfall with small grains, grasses and other clovers. An study, crimson clover reduced runoff from the oats crop is a frequent companion, either as a herbicide lactofen by 94 percent and norflurazon nurse crop to establish a clear stand of crimson and fluometuron by 100 percent (346). The clover, or as a high-biomass, nutrient-scav enging grass/legume mixture combines fibrous surface partner. In California, crimson clover is planted roots with short tap roots. with rose clover and medics in orchards and nut groves to minimize erosion and provide some N MANAGEMENT to tree crops (422). Establishment & Fieldwork Beneficial habitat and nectar source. Crimson Crimson clover will grow well in about any type clover has showy, deep red blossoms 1/2 to 1 inch of well drained soil, especially sandy loam. It may long. They produce abundant nectar, and are visit- fare poorly on heavy clay, waterlogged, extremely ed frequently by various types of bees. The acid or alkaline soils. Once established, it thrives blooms may contain many minute pirate bugs, an in cool, moist conditions. Dry soil often hinders important beneficial insect that preys on many fall plantings in the South. small pests, especially thrips (422). In Michigan, Inoculate crimson clover if it hasn’t been crimson increased blueberry pollination when grown before. Research in Alabama showed that planted in row middles. Georgia research shows deficiencies of phosphorus or potassium—or that crimson clover sustains pop ulations of pea strongly acidic soil with a pH of less than 5.0— aphids and blue alfalfa aphids. These species are can virtually shut down N fixation. Nodules not pests of pecans, but provide alternative food were not even formed at pH 5.0 in the test. for beneficial predators such as lady beetles, Phosphorus deficiency causes many small but which later attack pecan aphids. inactive nodules to form (188).

CRIMSON CLOVER 131 Winter annual use. Seed six to eight weeks using insecticide boxes and an air seeder. The before the average date of first frost at 15 to 18 clover established well and caused no corn yield lb./A drilled, 22 to 30 lb./A broadcast. As with loss (295). Crimson clover has proved to be more other winter legumes, the ideal date varies with promising in this niche than black medic, red elevation. In North Carolina, for example, the rec - clover or annual ryegrass, averaging 1,500 lb. ommended seeding dates are three weeks later DM/A and more than 50 lb. N/A (270). along the coast than in the mountains. In Maine, spring-seeded crimson clover can Don’t plant too early or crimson clover will go yield 4,000 to 5,000 lb. DM/A by July, adding 80 lb. to seed in the fall and not regrow in spring until N/A for fall vegetables. Mid-July seedings have the soil warms up enough yielded 5,500 lb./A of weed-suppressing biomass In Hardiness to germinate seeds. Early to by late October. Summer-annual use is planned with the expectation of winterkill. It sometimes Zone 5 and mid-August seeding is common in the northern part survives the winter even in southern Michigan colder, crimson of crimson clover’s winter- (270), however, so northern experimenters annual range. In southern should maintain a spring-kill option if icy winds clover can Michigan (Zone 5b - 6a) and heaving don’t do the job. provide a crimson clover, no-tilled In California, spring sowing often results in into wheat stubble in mid- stunting, poor flowering and reduced seed yield, winterkilled July, not only grew well and usually requires irrigation (422). into fall, but thrived the fol- mulch. lowing spring, performing Rotations. In the South, crops harvested in early nearly as well as hairy fall or sown in late spring are ideal in sequence vetch (270). with crimson clover. Timely planting of crimson While October plantings are possible in the clover and its rapid spring growth can enable it to lower Mississippi Delta, an August 15 planting in a achieve its maximum N contribution, and perhaps northern Mississippi test led to higher yields than reseed. While corn’s early planting date and cot - later dates (228). In the lower Coastal Plain of the ton’s late harvest limit a traditional winter-annual Gulf South, crimson clover can be planted until role for crimson clover, strip planting and zone mid-November. tillage create new niches. By leaving unkilled Nutrient release from crimson clover residue— strips of crimson clover to mature between zone- and that of other winter annual legumes—is tilled crop rows, the legume sets seed in May. quicker if the cover crop is tilled lightly into the The majority of its hard seed will germinate in fall. soil. Apart from erosion concerns, this fertility Kill crimson clover before seed set and use enhancing step adds cost and decreases the longer season cultivars where regrowth from weed-suppression effect early in the subsequent hard seed would cause a weed problem. crop’s cycle. Researchers have successfully strip-tilled into standing crimson clover when 25 to 80 percent of Summer annual use. In general, plant as soon as the row width is desiccated with a herbicide or all danger of frost is past. Spring sowing establish - mechanically tilled for the planting area. es crimson clover for a rotation with potatoes in Narrower strips of crimson clover increased Maine. In Michigan, researchers have successfully weed pressure but reduced mois ture competi- established crimson clover after short-season tion, while wider strips favored reseeding of the crops such as snap beans (229, 270). cover (236). In Northern corn fields, Michigan studies In a crimson clover-before-corn system, grow - showed that crimson clover can be overseed ed at ers can optimize grain yields by no-tilling into the final cultivation (layby) when corn is 16 to 24 crimson clover and leaving the residue on the sur- inches tall. Crimson clover was overseeded at 15 face, or optimize total forage yield by har vesting lb./A in 20-inch bands between 30-inch rows the crimson clover immediately before planting

132 MANAGING COVER CROPS PROFITABLY corn for grain or silage (204). In Mississippi, sweet A rolling stalk chopper flattens a mix of crim - potatoes and peanuts suffered no yield or quality son clover, hairy vetch and rye ahead of no-till veg- penalty when they were no-tilled into killed crim- etable transplanting at Steve Groff’s farm in son clover. The system reduced soil erosion and southeastern Pennsylvania. The crimson is killed decreased weed com petition (35). completely if it is in full bloom; and even early In Ohio, crimson clover mixed with hairy bloom is killed better than vegetative crimson. vetch, rye and barley provided a fertility enhanc - ing mulch for no-till processing tomato trans - Pest Management plants. Use of a prototype undercutter implement Crimson clover is a secondary host to plant pests with a rolling harrow provided a good kill. of the Heliothus species, Because the wide blades cut just under the soil which include corn In Mississippi, surface on raised beds, they do not break stalks, ear worm and cotton thus lengthening residue durability. The long-last- bollworm. Despite its crimson clover ing residue gave excellent results, even under known benefits, crimson produced mature organic management without the herbicides, clover has been eradicat- insecticides or fungicides used on parallel plots ed from many miles of seed and 135 lb. under different management regimes. Nancy roadsides in Mississippi Creamer at the University of North Carolina is at the request of some N/A by April 21. continuing work on the undercutter and on cover Delta farmers who sus- crops in organic vegetable systems (96). pect it worsens prob - lems from those pests (106). Mixed seeding. For cover crop mixtures, sow Crimson clover doesn’t sig nificantly increase crimson clover at about two-thirds of its normal risk of Southern corn rootworm in no-till corn, rate and the other crop at one third to one-half of while hairy vetch does (67). It is more resistant to its monoculture rate. Crimson clover develop- dis eases (422) and to some nematodes than other ment is similar to tall fescue. It even can be estab- clovers (337). Crimson clover is said to tolerate lished with light incorporation in existing stands viral diseases, but it succumbed to virus in July of aggressive grasses after they have been closely plantings in Mississippi (228) and to Sclerotinia mowed or grazed. in fall plantings in Maryland (108). In lab tests, crimson clover, berseem clover and Reseeding. Overwintered crimson clover needs hairy vetch have been shown to inhibit germina - sufficient moisture at least throughout April to tion and seedling development of onion, carrot produce seed (130). Cultivar selection is critical and tomato (40). However, this interference hasn’t when early spring maturity is needed. been observed in North Carolina field crops DIXIE and CHIEF are full-season standards. AU where strips are mechanically tilled, or in other ROBIN and FLAME beat them by about two weeks; studies with crimson clover as part of a killed a new cultivar, AU SUNRISE, is reportedly 1-3 organic mulch. No-till vegetable transplant ing has weeks earlier; the popular TIBBEE is about a week been done successfully on the same day as ahead of the standards. Price varies more by sea- mechanically killing the cover crop mix on Steve son al supply than by cultivar. Groff’s Lancaster County, Pa., farm with no negative effects. Killing. Its simple taproot makes crimson clover Wait two to three weeks after killing before easy to kill mechanically. Mowing after early bud planting seeds, to allow the biomass to begin to stage will kill crimson clover. Maximum N is avail- decompose and the soil biological life to stabilize. able at late bloom or early seed set, even before the During this time, a flush of bacteria such as plant dies naturally. Killing earlier yields less N—up Pythium and Rhizoctonia attack rapidly decaying to 50 lb. N/A less at its late veg etative stage, which plants. These bacteria also can attack seedling is about 30 days before early seed set (342). crops. To plant more quickly, mow the clover and

CRIMSON CLOVER 133 use row cleaners to clear the tops from the early bud stage. Mixing with grass reduces its seed zone. The mow/wait/plant cycle also may rel atively low bloat risk even further. Timely be influenced by the need to wait for rain to mowing four to six weeks before bloom improves increase seedbed moisture. growth, reduces lodging and will cause more uni- Mixed with hairy vetch, crimson clover attracts form flowering and seed ripening on highly fertile beneficial insects, provides nitrogen and sup - soils (120, 422). presses weeds in Oklahoma’s native and planta - Crimson clover can be grazed lightly in the fall, tion pecan groves. Both legumes go to seed and more intensively in the spring and still be left to then are harvested for forage. Arrowleaf clover accumulate N and/or set seed with little reduc - provided more biomass and N, but didn’t work as tion in its soil N contribution, provided livestock well for insect pest management and is very sus- are removed before flowering (80). ceptible to root knot nematode. Crimson clover harbors flower thrips and is a COMPARATIVE NOTES more likely host for tarnished plant bug than hairy vetch or subterranean clover (56). Intensive Crimson clover is: screenings show less abundant arthropod herbi - • less tolerant of mowing than are subclovers or vores and predators on crimson clover than on medics (422) hairy vetch (206). • similar to hairy vetch and Austrian winter pea Tillage practices and residue management vari - in the Southeast for total N production ations (no-till, incorporate, removal) of cover • a better weed suppressor in fall than hairy cropped lupin, rye, hairy vetch or crimson clover vetch had little consistent effect on nematodes in north • earlier to mature in spring than hairy vetch Florida corn fields (264). Cultivars. See Reseeding (p. 154) for cultivar Other Options comparisons. Pasture and hay crop. Crimson clover is excel - lent for grazing and haying. It will regrow if grazed Seed Sources. See Seed Suppliers (p. 195). or mowed no lower than 3 or 4 inches before the

134 MANAGING COVER CROPS PROFITABLY FIELD PEAS Pisum sativum subsp. arvense

Also called: Austrian winter peas (black peas), Canadian field peas (spring peas)

Type: summer annual and winter annual legume

Roles: plow-down N source, weed suppressor, forage

Mix with: strong-stemmed wheat, rye, triticale or barley for vertical support

See charts, pp. 66 to 72, for ranking and management summary.

igh N-fixers, field peas produce abundant the mid-Atlantic area. Risk of infection increases if vining forage and contribute to short-term pea crops are grown on the same land in close Hsoil conditioning. Succulent stems break rotation. down easily and are a quick source of avail able N Canadian field peas are a related strain of vining (361). Field peas grow rapidly in the cool, moist pea. These annual “spring peas” can out grow weather they encounter as winter annuals in the spring-planted winter peas. They often are seed- South and in parts of Idaho, and as early-sown ed with triticale or another small grain. Spring summer annuals in the Northeast, North Central peas have larger seeds, so there are fewer seeds and Northern Plains areas. Harvest options as per pound and seeding rates are higher, about 100 high-quality forage and seed increase their value. to 160 lb./A. However, spring pea seed is a bit less Winter-hardy types of field peas, especially expensive than Austrian winter pea seed. TRAPPER Austrian winter peas, can withstand tempera - is the most com mon Canadian field pea cultivar. tures as low as 10° F with only minor injury, but This section focuses on the widely grown they don’t overwinter consistently in areas colder Austrian winter pea. “Field peas” refers to both the than moderate Hardiness Zone 6. They are sensi - winter and spring types. tive to heat, particularly in combination with humidity. They tend to languish in mid-summer BENEFITS even in the cool Northeast (361), where average summers have fewer than 30 days exceeding Bountiful biomass. Under a long, cool, moist 86° F. Temperatures greater than 90° F cause flow- season during their vegetative stages, Austrian ers to blast and reduce seed yield. On humus-rich winter peas produce more than 5,000 lb. dry mat - black soils, field peas will produce abundant viny ter/A, even when planted in spring in colder cli- growth with few seed pods. mates. Idaho farmers regularly produce 6,000 to Use in the East and Southeast is limited by field 8,000 lb. DM/A from fall-planted Austrian winter peas’ susceptibility to Sclerotinia crown rot, peas. Because the residue breaks down quickly, which can destroy whole fields during winter in only peas in the high-production areas build up

FIELD PEAS 135 much long-term organic matter. Peas do not make viding disease suppression, better tilth and other a good organic mulch for weed control (361). enhancements to soil quality in a Saskatchewan study. Even at rates of 180 lb. N/A, fertilizer alone Nitrogen source. Austrian winter peas are top N was unable to bring yields of barley planted into producers, yielding from 90 to 150 lb. N/A, and at barley residue to the maximum achieved from times up to 300 lb. N/A. these pulse residues (163). Plowed down as green manure, fall-planted legume crops of Austrian winter pea, alfalfa and Water thrifty. In a comparison of water use hairy vetch each produced enough N for the pro - alongside INDIANHEAD lentils and GEORGE black duction of high-quality muskmelons under plastic medic, Austrian winter pea was the most mois - mulch and drip irrigation in a Kansas study. Melon ture-efficient crop in producing biomass. Each yields produced with the legumes were similar to crop had used 4 inches of water when Austrian those receiving synthetic fertilizer at 63 and 90 lb. winter pea vines were 16 inches long, the lentils N/A. The winter peas in the experiment pro duced were 6 to 8 inches tall and the black medic cen - 96 lb. N/A the first year and 207 lb. N/A the sec- tral tillers were 4 inches tall (383). ond (387). Austrian winter peas grown in a controlled set- Austrian winter peas harvested as hay then ting at 50° F recorded more than 75 percent of its applied as mulch mineralized N at more than dou- N2 fixed per unit of water used by the 63rd day of ble the rate of alfalfa hay. The N contribution was growth. White clover, crimson clover and hairy measured the summer after a fall plowdown of vetch reached the same level of water effi ciency, the residue. The estimated N recovery of Austrian but it took 105 days (334). winter pea material 10 months after incorporation was 77 percent—58 percent through spring Quick growing. Rapid spring growth helps peas wheat and 19 percent in the soil (254). out compete weeds and make an N contribution Austrian winter pea green manure provided the in time for summer cash crops in some areas. highest spring wheat yield the following year in a Montana trial comparing 10 types of medics, Forage booster. Field peas grown with barley, seven clovers, yellow biennial sweet clover and oat, triticale or wheat provide excellent livestock three grains. Crops that produced higher tonnage forage. Peas slightly improve forage yield, but sig - of green manure usually had a negative effect on nificantly boost protein and relative feed value of the subsequent wheat crop due to moisture defi - small grain hay. ciency that continued over the winter between the crops (381). Field peas can leave 80 lb. N/A if Seed crop. Seed production in Montana is about terminated at mid-season in lieu of summer fallow 2,000 lb./A and about 1,500 lb./A in the Pacific in dryland areas, or leave more than 30 lb. N/A Northwest. Demand is growing for field peas as after pea harvest at season’s end (74). food and livestock feed (74). A winter pea green manure consistently result - ed in higher malting barley protein content than Long-term bloomer.The purple and white blos - that following other legumes or fallow in a soms of field peas are an early and extended Montana trial. Annual legumes harvested for seed source of nectar for honeybees. left less soil N than did plots in fallow. Also tested were fava bean, lentil, chickpea, spring pea, winter Chill tolerant. Austrian winter pea plants may pea hay and dry bean (262). lose some of their topgrowth during freezes, but can continue growing after temperatures fall as Rotational effects. Pulse crops (grain legumes low as 10° F. Their shallow roots and succulent such as field peas, fava beans and lentils) improv - stems limit their overwintering ability, however. ed sustainability of dryland crop rotations by pro - Sustained cold below 18° F without snow cover

136 MANAGING COVER CROPS PROFITABLY usually kills Austrian winter pea (202). To maxi - mize winter survival: • Select the most winter-hardy cultivars avail - able—GRANGER, MELROSE and COMMON WINTER. • Seed early enough so that plants are 6 to 8 inches tall before soil freezes, because peas are shal low rooted and susceptible to heaving. Try to plant from mid-August to mid- September in Zone 5. • Plant into grain stubble or a rough seedbed, or interseed into a winter grain. These environ - ments protect young pea roots by suppressing

soil heaving during freezing and thawing. Sarrantonio Marianne Trapped snow insulates plants, as well. FIELD PEAS (Pisum sativum subsp. arvense)

MANAGEMENT fall-planted. Seed by September 15 in Zone 5 of the Inter-Mountain region in protected valleys Establishment & Fieldwork where you’d expect mild winter weather and Peas prefer well-limed, well-drained clay or heavy good, long-term snow cover. October-planted loam soils, near-neutral pH or above and moderate Austrian winter pea in the Zone 9 Sacramento fertility. They also do well on loamy sands in Valley of California thrive on cool, moist condi - North Carolina. Field peas usually are drilled 1 to tions and can contribute 150 lb. N/A by early 3 inches deep to ensure contact with moist soil April. and good anchoring for plants. The general rule for other parts of the semi-arid If you broadcast peas, incorporation will great - West where snow cover is dependable is to plant ly improve stands, as seed left exposed on the peas in the fall after grain harvest. In these dry sur face generally does not germinate well. Long- regions of Montana and Idaho, overseed peas at vined plants that are shallow-seeded at low seed - 90 to 100 lb./A by “frostseeding” any time soils ing rates tend to fall over (lodge), lay against the have become too cold for pea germination. Be soil and rot. Combat this tendency by planting sure residue cover is not too dense to allow seed with a small grain nurse crop such as oats, wheat, to work into the soil through freeze/thaw cycles barley, rye or triticale. Reduce the pea seeding rate as the soil warms (383). by about one quarter—and grain by about one In the low-rainfall Northern Plains, broadcast third—when planting a pea/grain mix. clear stands of peas in early spring at a similar rate Planted at 60 to 80 lb./A in Minnesota, Austrian for the “Flexible Green Manure” cropping system winter peas make a good nurse crop for alfalfa. (below). Seeding at about 100 lb./A compensates Field pea seed has a short shelf life compared somewhat for the lack of incorporation and pro - with other crops. Run a germination test if seed is vides strong early competition with weeds (383). more than two years old and adjust seeding rate Plant as soon as soil in the top inch reaches 40° F accordingly. If you haven’t grown peas in the to make the most of spring moisture (74). seeded area for several years, inoculate immedi - A mixture of Austrian winter peas and a small ately before seeding. grain is suitable for dryland forage production because it traps snow and uses spring moisture to West. In mild winter areas of California and produce high yields earlier than spring-seeded Idaho, fall-plant for maximum yield. In those areas, annual forages (74). With sufficient moisture, you can expect spring-planted winter peas to spring peas typically produce higher forage yields produce about half the biomass as those that are than Austrian winter peas.

FIELD PEAS 137 East. Planted as a companion crop in early spring of Mexico. Quick regrowth starts about the third in the Northeast, Austrian winter peas may pro - week in January. He kills them in mid-April by vide appreciable N for summer crops by disking, then shallow plows to incorporate the Memorial Day (361). In the mid-Atlantic, Austrian heavy residue (202). winter peas and hairy vetch planted October 1 Farmers and researchers note several IPM cau- and killed May 1 produced about the same total N tions, because Austrian winter peas: and corn yields (108). • Host some races of nematodes • Are susceptible to winter Sclerotinia crown Southeast. Seed by October 1 in the inland Zone rot, Fusarium root rot as well as seed rot and 8 areas of the South so that root crowns can blights of the stem, leaf or pod become established to resist heaving. Peas pro- • Are variably susceptible to the Ascochyta duce more biomass in the cooler areas of the blight (MELROSE cultivar has some resistance) South than where temperatures rise quickly in • Host the pathogen Sclerotinia minor. There spring (74, 361). Peas planted in late October in was a higher incidence of leaf drop in South Carolina’s Zone 8 and terminated in mid- to California lettuce planted after Austrian winter late April produce 2,700 to 4,000 lb. dry matter/A peas in one year of a two-year test (232). (23). Austrian winter peas were heavily damaged by Killing Sclerotinia trifoliorum Eriks in several years of a Peas are easily killed any time with herbicides, or four-year study in Maryland, but the crop still pro - by disking or mowing after full bloom, the stage of duced from 2,600 to 5,000 lb. dry matter/A per maturity that provides the optimum N contri - year in four out of five years. One year DM pro- bution. Disk lightly to preserve the tender residue duc tion was only 730 lb./A. Mean N contribution for some short-term erosion control. despite the disease was 134 lb. N/A. Overall, The downside to the Austrian winter peas were rated as being more Winter pea quick breakdown of pea suited for Maryland Coastal Plain use than in the vines is their slimy condi- Piedmont, due to harsher winters in the latter residue breaks tion in spring if they win - location (204). down and terkill, especially in dense, To combat disease, rotate cover crops to avoid pure stands. Planting with a growing peas in the same field in successive years. releases N winter grain provides some To minimize disease risk, waiting several years is protection from winterkill best. To minimize risk of losing cover crop benefits quickly. and reduces matting of to Sclerotinia disease in any given season, mix with dead pea vegetation. another cover crop such as cereal rye.

Pest Management Crop Systems Winter peas break crop disease cycles, Ben Northern Plains. Austrian winter peas (and Burkett of Petal, Miss., has found. Septoria leaf other grain legumes) are increasingly used instead spot prob lems on his cash crops are reduced of fallow in dryland cereal rota tions. The legumes when he plants Austrian winter pea in fall after help prevent saline seeps by using excess soil snap beans and ahead of collards and mustard moisture between cereal crops. They also add N greens the next sum mer. Between October 15 and to the system. The legume>cereal sequence starts November 15, Burkett broadcasts just 50 lb./A with a spring- or fall-planted grain legume then incorporates the seed with a shallow pass of (instead of fallow), followed by a small grain. his field cultivator. They grow 3 to 6 inches tall Peas work well in this system because they are before going dormant in late December in his shallow-rooted and therefore do not extract deep Zone 8 location about 75 miles north of the Gulf soil moisture. The pea crop is managed according

138 MANAGING COVER CROPS PROFITABLY to soil moisture conditions. Depending on grow- yields as did using the peas as green manure or ing season precipitation, the peas can be grazed, leaving the field fallow in the first year. While terminated or grown to grain harvest. Growers neither Austrian winter pea green manure nor fal - terminate the crop when about 4 inches of plant- low produced income, the green manure available water remains in the soil, as follows: improved soil organic matter and added more N • Below-normal rainfall—terminate the grain for wheat than did summer fallow. Fallow caused legume early. a net soil capacity loss by “mining” finite soil • Adequate rainfall—terminate the grain organic matter reserves (253). legume when about 4 inches of soil water In a northern Alberta comparison of conven - remains. Residue is maintained for green tional (tilled), chemical (herbicide) and green manure, moisture retention and erosion (field pea) fallow systems, spring-planted field prevention. peas provided 72 lb. N/A, significantly more than • Above-average rainfall—grow the crop to the other systems. The field pea system was also maturity for grain harvest. more profitable when all inputs were considered, providing higher yield for two subsequent In conventional fallow systems, fields are left cash crops, higher income unplanted to accumulate soil moisture for the and improvement of soil In the cash crop. Weeds are controlled using tillage or quality (12). Northeast, herbicides. Grain legumes provide a soil-protecting alter- Southeast. Fall-seeded spring-planted native to fallow that can be managed to ensure Austrian winter peas out- adequate moisture for the cereal crop. Legumes produced hairy vetch by peas can be provide long-term benefits by producing N for about 18 percent in both incorporated by the subsequent crop, disrupting disease, insect dry matter and N produc- and weed cycles and building soil. tion in a three-year test in Memorial Day. Austrian winter peas work in these rotations the Coastal Plain of North where there is at least 18 inches of rain per year. Carolina. When legumes INDIANHEAD lentils (Lens culinaris Medik), a spe- were grown with rye, wheat or spring oats, cialty lentil for cover crop use, are also widely Austrian winter pea mixtures also had the highest used in this system. dry matter yields. Over the three years, Austrian Montana research shows that when soil mois - winter peas ranked the highest (dry-matter and ture is replenished by winter precipitation, annu - N) in the legume-only trials and as the legume al legumes can substitute for fallow without component of the legume/grain mix tures. In significantly reducing the yield of the next barley descending order after the peas were hairy vetch, crop. Montana rainfall averages 12-16 inches, common vetch and crimson clover. The peas so peas are planted but can only be taken to were sown at 54 lb./A in the pure seedings and 41 grain harvest in above-normal rainfall years. The lb./A in mixtures (344). legume can generate income from harvest of its In the year of greatest N fixation, soil N in the hay or grain or through fertilizer N savings from Austrian winter pea mixture treatments was 50 the legume’s contribution to the small grain crop percent greater than the average of all other treat - (136). ments. Researchers noted that the bottom leaves In Idaho, fall-seeded Austrian winter peas har - of pea vines were more decomposed than other vested for seed provided income, residual N from legumes, giving the crop an earlier start in N con - the pea straw and soil disease suppression in a tribution. Further, soil N in the upper 6 inches of study of efficient uses of the legume cover. A crop soil under the Austrian winter peas held 30 to 50 rotation of Austrian winter pea (for grain)>winter percent of the total soil inorganic N in the winter wheat>spring barley produced similar wheat pea treatments, compared with levels of less than

FIELD PEAS 139 Peas Do Double Duty for Kansas Farmer

PARTRIDGE, Kan.—Jim French figures Austrian colder early and mid-winter temperatures. In winter peas provide free grazing, free nitrogen, most years, he sets up temporary fence and or both. The vining legume produces just as turns his cattle into the peas about April 1 at much N for the following grain sorghum crop the stocking rate of two animal units per acre. even if he lets his registered Gelbvieh herd eat During the best years of mild weather and all they want of the winter annual’s spring adequate moisture, “the cattle have a hard time growth. keeping up,” says French. Depending on his French farms on flat, well-drained sandy need for forage or organic matter, he leaves loam soil near Partridge, Kan. He manages the cattle in until he incorporates the pea about 640 acres each of cash crops (winter stubble, or gives it time to regrow. wheat and grain sorghum) and forages (alfalfa, One reason he gets about the same 90 to 120 sudangrass, winter peas and cowpeas, and an lb. N/A contribution with or without grazing is equal area in grass pasture). Peas follow wheat that the winter pea plants apparently continue in the three-year crop rotation on his south- N fixation and root growth while being grazed. central Kansas farm. He chisel plows the Soil tests show that 25 to 30 lb. N/A are wheat stubble twice about 7 inches deep, available in the nitrate form at incorporation in disks once to seal the surface, then controls late spring, with the balance in an organic form weeds as necessary with a light field cultivator. that mineralizes over the summer. Grazing the Between mid-September and mid-October he peas helps to contain cheatgrass, which tends inoculates about 30 lb./A of the peas and drills to tie up N if it’s incorporated just ahead of his them with an old John Deere double-run disk sorghum crop. drill in 8-inch rows. Establishment is usually French is sold on winter peas ahead of his good, with his only anxiety coming during grain sorghum because it provides N while freeze-thaw cycles in spring. “Each time the peas reducing weed pressure from cheatgrass and break dormancy, start to grow, then get zapped pigweed and decreasing lodging from charcoal with cold again they lose some of their root root rot. The option to use the peas as reserves and don’t have quite the resistance to forage—while still achieving adequate freezing they did. They’ll sprout back even if sorghum yield—lets him buy less processed there’s vegetative freeze damage as long as their feed, improves livestock health and accelerates food reserves hold out,” French reports. conversion of the peas’ organic material into Ironically, this spring freezing is less of a available soil nutrients. problem further north where fields stay frozen “Winter peas work best where you integrate longer before a slower thaw. This works as crops and livestock,” says French. “They give long as snow cover protects the peas from the you so many benefits.”

30 percent in the top soil layer for all other treat - break down. Mixtures of small grains with ments. In situations where the early-summer N Austrian winter peas and the vetches had C:N val- release from peas could be excessive, mixing ues from 13 to 34, but were generally under 25 to Austrian winter peas with a grain can moderate 30, the accepted threshold for avoiding net immo- the N contribution and slow down its release into bilization of N (344). the soil (344). Austrian winter peas and crimson clover can The carbon to nitrogen (C:N) ratio of plant mat - provide adequate N for conventionally planted cot- ter is an indication of how rapidly vegetation will ton in South Carolina. In a three-year trial, fer tilizer

140 MANAGING COVER CROPS PROFITABLY rates of up to 150 lb. N/A made no improve ment COMPARATIVE NOTES to cotton yield on the pea plots. The evaluation showed that soil nitrate under Austrian winter peas Field peas won’t tolerate field traffic due to peaked about nine weeks after incor poration (22). succulent stems (191). When selecting types, Austrian winter peas achieved 50 to 60 percent remember that long-vined varieties are better for groundcover when they were overseeded at weed control than short-vined types. about 75 lb./A into soybeans at leaf yellowing in southeastern Pennsylvania, where they can sur - Cultivars. MELROSE, In dryland vive some winters. The peas produced nearly 2 known for its winter - systems, winter tons of dry matter and 130 lb. N/A by May 20 in hardi ness, is a cultivar this test (191). Overseeding peas into corn at last of the Austrian winter peas produce cultivation is not recommended due to poor pea type. Planted shade tolerance. the first week of abundant biomass Austrian winter peas, like other hollow- Sept ember in Idaho, with limited stemmed succulent covers such as vetch and fava MELROSE peas yielded beans, do not respond well to mowing or cutting 300 lb. N/A and 6 tons moisture. after they begin to bloom. In their earlier stages, of dry matter the next Austrian winter peas will regrow even when June. Planted in mid- grazed several times. See Peas Do Double Duty April, the cultivar yielded “just” 175 lb. N/A and for Kansas Farmer (p. 140). 3.5 T dry matter/A (202). After three years of moisture testing, Kansas GRANGER is an improved winter pea that has farmer Jim French can explain why he sees more fewer leaves and more tendrils, which are stiffer soil moisture after spring grazing than when the than standard culti vars. It is more upright and its peas are left to grow undisturbed. “There’s decreas- pods dry more quickly than other winter pea ing overall transpiration because there’s less leaf types. MAGNUS field peas have out-produced area to move moisture out of the soil into the air. Austrian winter peas in California and bloom up Yet the root mass is about the same.” Ungrazed peas to 60 days earlier. pump more water as they keep growing. Seed sources. See Seed Suppliers (p. 195). Other Options. Harvest field peas for hay when most of the pods are well formed. Use a mower with lifting guards and a windrow attachment to handle the sprawl - ing vines.

FIELD PEAS 141 HAIRY VETCH Vicia villosa

Type: winter annual or summer annual legume

Roles: N source, weed suppressor, topsoil conditioner, reduce erosion

Mix with: small grains, field peas, bell beans, crimson clover, buckwheat

See charts, p. 66 to 72, for ranking and management summary.

ew legumes match hairy vetch for spring Corn planting date comparison trials with residue production or nitrogen contribu- cover crops in Maryland show that planting as Ftion. Widely adapted and winter hardy late as May 15 (the very end of the month-long through Hardiness Zone 4 and into Zone 3 (with local planting period) optimizes corn yield and snow cover), hairy vetch is a top N provider in profit from the system. Spring soil moisture was temperate and subtropical regions. higher under the vetch or a vetch-rye mixture The cover grows slowly in fall, but root devel- than under cereal rye or no cover crop. Killed opment continues over winter. Growth quickens vetch left on the surface conserved summer mois- in spring, when hairy vetch becomes a sprawling ture for improved corn production (80, 82, 84, 85, vine up to 12 feet long. Field height rarely exceeds 173, 243). 3 feet unless the vetch is supported by another Even without crediting its soil-improving bene- crop. Its abundant, viney biomass can be a benefit fits, hairy vetch increases N response and pro- and a challenge. The stand smothers spring duces enough N to pay its way in many systems. weeds, however, and can help you replace all or Hairy vetch without fertilizer was the preferred most N fertilizer needs for late-planted crops. option for “risk-averse” no-till corn farmers in Georgia, according to calculations comparing BENEFITS costs, production and markets during the study. The economic risk comparison included crimson Nitrogen source. Hairy vetch delivers heavy clover, wheat and winter fallow. Profit was higher, contributions of mineralized N (readily available but less predictable, if 50 pounds of N were added to the following cash crop). It can provide suffi- to the vetch system (310). cient N for many vegetable crops, partially replace Hairy vetch ahead of no-till corn was also the N fertilizer for corn or cotton and increase cash preferred option for risk averse farmers in a three- crop N efficiency for higher yield. In some parts of California and the East in Zone Note: To roughly estimate hairy vetch N contri- 6, hairy vetch provides its maximum N by safe bution in pounds per acre, cut and weigh fresh corn planting dates. In Zone 7 areas of the vetch top growth from a 4-foot by 4-foot area. Southeast, the fit is not quite as good, but sub- Multiply pounds of fresh vetch by 12 to gauge stantial N from vetch is often available before available N, by 24 to find total N (377). For a more corn planting. accurate estimate, see How Much N? (p. 22).

142 MANAGING COVER CROPS PROFITABLY year Maryland study that also included fallow and winter wheat ahead of the corn. The vetch-corn system maintained its economic advantage when the cost of vetch was projected at maximum his- toric levels, fertilizer N price was decreased, and the herbicide cost to control future volunteer vetch was factored in (173). In a related study on the Maryland Coastal Plain, hairy vetch proved to be the most profitable fall-planted, spring desiccated legume ahead of no-till corn, compared with Austrian winter peas and crimson clover (243). In Wisconsin’s shorter growing season, hairy vetch planted after oat harvest provided a gross

margin of $153/A in an oat/legume/corn rotation Sarrantonio Marianne (1995 data). Profit was similar to using 160 lb. N/A in continuous corn, but with savings on fertilizer and corn rootworm insecticide (400). HAIRY VETCH (Vicia villosa) Hairy vetch provides yield improvements beyond those attributable to N alone. These may tions than does vetch. Residue with a C:N ratio of be due to mulching effects, soil structure 25:1 or more tends to immobilize N. For more improvements leading to better moisture reten- information, see How Much N? (p. 22), and the tion and crop root development, soil biological rest of that section, Building Soil Fertility and activity and/or enhanced insect populations just Tilth with Cover Crops (p. 16). below and just above the soil surface. Early weed suppression. The vigorous spring Soil conditioner. Hairy vetch can improve root growth of fall-seeded hairy vetch out-competes zone water recharge over winter by reducing weeds, filling in where germination may be a bit runoff and allowing more water to penetrate the spotty. Residue from killed hairy vetch has a weak soil profile through macropores created by the allelopathic effect, but it smothers early weeds crop residue (143). Adding grasses that take up a mostly by shading the soil. Its effectiveness wanes lot of water can reduce the amount of infiltration as it decomposes, falling off significantly after about and reduce the risk of leaching in soils with excess three or four weeks. For optimal weed control with nutrients. Hairy vetch, especially an oats/hairy a hairy vetch mulch, select crops that form a quick vetch mix, decreased surface ponding and soil canopy to compensate for the thinning mulch or crusting in loam and sandy loam soils. Researchers use high-residue cultivators made to handle it. attribute this to dual cover crop benefits: their abil- Mixing rye and crimson clover with hairy vetch ity to enhance the stability of soil aggregates (par- (seeding rates of 30, 10, and 20 lb./A, respectively) ticles), and to decrease the likelihood that the extends weed control to five or six weeks, about aggregates will disintegrate in water (143). the same as an all-rye mulch. Even better, the mix Hairy vetch improves topsoil tilth, creating a provides a legume N boost, protects soil in fall and loose and friable soil structure. Vetch doesn’t winter better than legumes, yet avoids the poten- build up long-term soil organic matter due to its tial crop-suppressing effect of a pure rye mulch tendency to break down completely. Vetch is a on some vegetables. succulent crop, with a relatively “low” carbon to nitrogen ratio. Its C:N ratio ranges from 8:1 to Good with grains. For greater control of winter 15:1, expressed as parts of C for each part of N. annual weeds and longer-lasting residue, mix Rye C:N ratios range from 25:1 to 55:1, showing hairy vetch with winter cereal grains such as rye, why it persists much longer under similar condi- wheat or oats.

HAIRY VETCH 143 Growing grain in a mixture with a legume not germination, particularly if broadcast seeded. only lowers the overall C:N ratio of the combined Plant vetch 30 to 45 days before killing frost for residue compared with that of the grain, it may winter annual management; in early spring for actually lower the C:N ratio of the small grain summer growth; or in July if you want to kill or residue as well. This internal change causes the incorporate it in fall or for a winter-killed mulch. grain residue to break down faster, while accu- Hairy vetch has a relatively high P and K mulating the same levels of N as it did in a mono- requirement and, like all legumes, needs sufficient culture (344). sulfur and prefers a pH between 6.0 and 7.0. However, it can survive through a broad pH range Moisture-thrifty. Hairy vetch is more drought- of 5.0 to 7.5 (120). tolerant than other vetches. It needs a bit of mois- An Illinois farmer successfully no-tills hairy ture to establish in fall and to resume vegetative vetch in late August at 22 lb./A into closely growth in spring, but relatively little over winter mowed stands of fescue on former Conservation when above-ground growth is minimal. Reserve Program land (417). Using a herbicide to kill the fescue is cheaper than mowing, but it Phosphorus scavenger. Hairy vetch showed must be done about a month later when the grass higher plant phosphorus (P) concentrations than is actively growing for the chemical to be effec- crimson clover, red clover or a crimson/ryegrass tive. Vetch also can be no-tilled into soybean or mixture in a Texas trial. Soil under hairy vetch also corn stubble (50, 80). had the lowest level of P remaining after growers In Minnesota, vetch can be interseeded into applied high amounts of poultry litter prior to sunflower or corn at last cultivation. Sunflower vegetable crops (121). should have at least 4 expanded leaves or yield will be reduced (221, 222). Fits many systems. Hairy vetch is ideal ahead of Farmers in the Northeast’s warmer areas plant early-summer planted or transplanted crops, pro- vetch by mid-September to net 100 lb. available viding N and an organic mulch. Some Zone 5 N/A by mid-May. Sown mid-August, an oats/hairy Midwestern farmers with access to low-cost vetch mix can provide heavy residue (180). seed plant vetch after winter grain harvest in mid- Rye/hairy vetch mixtures mingle and moderate summer to produce whatever N it can until it the effects of each crop. The result is a “hybrid” winterkills or survives to regrow in spring. cover crop that takes up and holds excess soil nitrate, fixes N, stops erosion, smothers weeds in Widely adapted. Its high N production, vigorous spring and on into summer if not incorporated, growth, tolerance of diverse soil conditions, low fer- contributes a moderate amount of N over a longer tility need and winter hardiness make hairy vetch period than vetch alone, and offsets the N limiting the most widely used of winter annual legumes. effects of rye (81, 83, 84, 86, 377). Seed vetch/rye mixtures, at 15-25 lb. hairy MANAGEMENT vetch with 40-70 lb. rye/A (81, 361). Overseeding (40 lb./A) at leaf-yellowing into Establishment & Fieldwork soybeans can work if adequate rainfall and soil Hairy vetch can be no-tilled, drilled into a pre- moisture are available prior to the onset of freez- pared seedbed or broadcast. Dry conditions often ing weather. Overseeding into ripening corn (40 reduce germination of hairy vetch. Drill seed at 15 lb./A) or seeding at layby has not worked as con- to 20 lb./A, broadcast 25 to 30 lb./A. Select a high- sistently. Late overseeding into vegetables is possi- er rate if you are seeding in spring, late in the fall, ble, but remember that hairy vetch will not stand or into a weedy or sloped field. Irrigation will help heavy traffic (361).

144 MANAGING COVER CROPS PROFITABLY Killing A series of trials in Maryland showed a differ- Your mode of killing hairy vetch and managing ent mix of conditions. Corn planting in late-April residue will depend on which of its benefits are is common there, but early killing of vetch to most important to you. Incorporation of hairy plant corn then had the surprising effect of vetch vegetation favors first-year N contribution, decreasing soil moisture and corn yield, as well as but takes significant energy and labor. Keeping predictably lowering N contribution. The earlier- vetch residue on the surface favors weed sup- planted corn had less moisture-conserving pression, moisture retention, and insect habitat, residue. Late April or early May kill dates, with but may reduce N contribution. However, even in corn no-tilled 10 days later, consistently resulted no-till systems, hairy vetch consistently provides in higher corn yields than earlier kill dates (82, 83, very large N input (replacing up to 100 lb. N/A). 84, 85). With hairy vetch and a vetch/rye mixture, In spring, hairy vetch continues to add N summer soil water conservation by the cover through its “seed set” stage after blooming. crop residue had a greater impact than spring Biomass and N increase until maturity, giving moisture depletion by the growing cover crop in either greater benefit or a dilemma, depending on determining corn yield (84, 85). your ability to deal with vines that become more Results in the other trials, which also included sprawling and matted as they mature. a pure rye cover, demonstrated the management Mulch-retaining options include strip-tilling flexibility of a legume/grain mix. Early killed rye or strip chemical desiccation (leaving vetch protects the soil as it conserves water and N, untreated between the strips), mechanical killing while vetch killed late can meet a large part of the (rotary mowing, flailing, cutting, sub-soil shearing N requirement for corn. The vetch/rye mixture with an undercutter, or chopping/flattening can conserve N and soil moisture while fixing N with a roller/crimper) or broadcast herbicide for the subsequent crop. The vetch and vetch/rye application. mixture accumulated N at 130 to 180 lb./A. The mixture contained as much N or more than vetch No-till corn into killed vetch.The best time for alone (85, 86). no-till corn planting into hairy vetch varies with In an Ohio trial, corn no-tilled into hairy vetch local rainfall patterns, soil type, desired N contri- at mid-bloom in May received better early season bution, season length and vetch maturity. weed control from vetch mulch than corn seeded In southern Illinois, hairy vetch no-tilled into into vetch killed earlier. The late planting date fescue provided 40 to 180 lb. N/A per year over decreased yield, however (189), requiring calcula- 15 years for one researcher/farmer. He used her- tion to determine if lower costs for tillage, weed bicide to kill the vetch about two weeks before control, and N outweigh the yield loss. the area’s traditional mid-May corn planting date. Once vetch reaches about 50% bloom, it is easily The 14-day interval was critical to rid the field of killed by any mechanical treatment. To mow-kill for prairie voles, present due to the field’s thick fes- mulch, rye grown with hairy vetch improves cut- cue thatch. ting by holding the vetch off the ground to allow He kills the vetch when it is in its pre-bloom or more complete severing of stems from roots. Rye bloom stage, nearing its peak N-accumulation also increases the density of residue covering the capacity. Further delay would risk loss of soil vetch stubble to prevent regrowth. moisture in the dry period customary there in Much quicker and more energy-efficient than early June. When the no-tilled vetch was left to mowing is use of a modified Buffalo rolling stalk grow one season until seed set, it produced 6 tons chopper, an implement designed to shatter stand- of dry matter and contributed a potentially pol- ing corn stubble. The chopper’s rolling blades luting 385 lb. N/A (417). This high dose of N must break over, crimp and cut crop stems at ground be managed carefully during the next year to pre- level, and handle thick residue of hairy vetch at 8 vent leaching or surface runoff of nitrates. to 10 mph (169).

HAIRY VETCH 145 Cover Crop Roller Design Holds Promise For No-Tillers However, timing of control and planting in a single pass could limit adoption; hope lies in breeding cover crops that flower in time for traditional planting window.

THE POSSIBILITY of using rollers to reduce with a 3-inch overlap on each end. The original herbicide use isn’t new, but advances are design has already been modified to include a being made to improve the machines in ways 15-foot, 6-inch model suitable for use with a 6- that could make them practical for controlling row planter on 30-inch rows. It can be adapted no-till cover crops. to fit a 4-row planter on 38-inch rows, and a 5- Cover crop rolling is gaining visibility and foot version for 2-row vegetable planters. credibility in tests by eight university/farmer “We realize that 6-row equipment is small research teams across the country. The test by today’s standards, and work is under way rollers were designed and contributed by The on a system that mounts one section of the Rodale Institute (TRI), a Pennsylvania-based roller in front of the tractor with the organization focused on organic agricultural remainder mounted on the planter ahead of research and education. The control achieved the row units. This design will allow as wide a with the roller is comparable to a roller roller system as a farmer needs,” Moyer says. combined with a glyphosate application, Chevron Pattern. The chevron pattern on according to TRI. the face of the roller came about after the The Rodale crop rollers were delivered to designers realized that mounting the roller state and federal cooperative research teams in blades in a straight line would cause excessive Virginia, Michigan, Mississippi, North Dakota, bouncing, while just curving the blades in a Pennsylvania, Georgia, California and Iowa in screw pattern would act like an auger and Spring, 2005. Funding for the program comes create a pulling effect. “If you were driving up from grants and contributions from the a hill that might be fine, but we don’t need Natural Resources Conservation Service and help pulling our tractors down the steep private donors. I&J Manufacturing in Gap, Pa., slopes we farm. The chevron pattern fabricated the models distributed to the neutralizes any forces that might pull the research teams. tractor in either direction,” Moyer explains. It “The requirement is that each research overcomes both the bounce of straight-line leader partners with a farmer cooperator to blades and the auguring effect of corkscrew adapt the rollers to local conditions and cover blades. cropping systems,” explains Jeff Moyer, TRI’s “In addition, with the twisted blade design, farm manager. “Our goal is to gain more only a very small portion of the blade touches knowledge about the soil building and weed the ground at any one time as it turns, so the management effects of cover crops while full pressure of the roller is applied 1 inch at a reducing the need for herbicides,” he says. time. This roller design works better than Farmer Built. Moyer designed and built anything we’ve ever used,” he adds. the first front-mounted TRI roller prototype in Prior to settling on the TRI prototype, Moyer 2002 in conjunction with Pennsylvania farmer and Brubaker studied stalk choppers with nine John Brubaker, whose land abuts the TRI rolling drums arranged in two parallel rows. property. The original 10-foot, 6-inch roller This design required 18 bearings and provided width is equal to 4 rows on 30-inch spacing, lots of places for green plant material to bunch

146 MANAGING COVER CROPS PROFITABLY up. The TRI ground-driven roller has a single vetch, wheat, triticale, oats, buckwheat, clover, cylinder and two offset bearings inset 3 inches winter peas and other species. Timing is the on either side and fronted with a shield. The key to success, Moyer emphasizes, and a lot of blades are welded onto the 16-inch-diameter farmers don’t have the patience to make it drum, but replacement blades can be work right. purchased from the manufacturer and bolted “The bottom line is that winter annuals on as needed. The 10-foot, 6-inch roller weighs want to die anyway, but if you time it wrong, 1,200 pounds empty and 2,000 pounds if filled they’re hard to kill,” he says. “If you try to roll a with water. winter annual before it has flowered—before Front Mount Benefits. The biggest it has physiologically reproduced—the plant advantage of the front-mounted roller is that will try to stand up again and complete the the operator can roll the cover crop and no-till job of reproduction, the most important stage the cash crop in a single field pass, Moyer of its life cycle. But, if you roll it after it has explains. In TRI trials, simultaneous rolling and flowered, it will dry up and die.” no-till planting eliminated seven of the eight At least a 50 percent, and preferably a 75 to field passes usually necessary with 100 percent bloom, is recommended before conventional organic corn production, rolling. Moyer hopes to see plant breeders including plowing, discing, packing, planting, recognize the need to develop cover crop two rotary hoe passes and two cultivations. varieties with blooming characteristics that Rolling the field and no-tilling in one pass coincide with preferred crop planting also eliminates the problem of creating a thick windows. green cover crop mat that makes it difficult to “We really like to use hairy vetch on our see a row marker line on a second pass for farm, for example, because it’s a great source planting. of nitrogen and is a very suitable crop to plant Also, planting in a second pass in the corn into. The roller crimps the stem of the opposite direction from which the cover crop hairy vetch every 7 inches, closing the plant’s was rolled makes getting uniform seeding vascular system and ensuring its demise. depth and spacing more difficult because the “The problem is we would like it to flower planter tends to stand the plant material back a couple weeks earlier to fit our growing up. “Think of it as combing the hair on your season. It’s hard for farmers to understand dog backwards,” Moyer says. when it’s planting time and we’re telling them “Another disadvantage of rear-mounted to wait a couple more weeks for their cover machines like stalk choppers is that the tractor crop to flower,” he says. tire is the first thing touching the cover crop. “We need to identify the characteristics we If the soil is even a little spongy, the cover want in cover crops and encourage plant crop will be pushed into the tire tracks and breeders to focus on some of those. It should because the roller is running flat, it can’t be a relatively easy task to get an annual crop crimp the depressed plant material. A week to mature a couple weeks earlier, compared to later the plants missed by the roller will be some of the breakthrough plant breeding back up and growing again.” we’ve seen recently,” Moyer says. Crop Versatility. The TRI roller concept has been tested in a wide range of winter annual cover crops, including cereal rye, hairy continued on page 148

HAIRY VETCH 147 For More Information. Updates on roller Editor’s Note: PURPLE BOUNTY, a new, earlier research, more farmer stories and plans for the variety of hairy vetch, was released in 2006 by TRI no-till cover crop roller can be accessed at the USDA-Agricultural Research Service, www.newfarm.org/depts/notill. To ask Beltsville, MD in collaboration with the Rodale questions of The Rodale Institute, e-mail to Institute, Pennsylvania State University and [email protected]. Cornell University. See also “Where can I find information —Ron Ross. Adapted with permission from about the mechanical roller-crimper used in www.no-tillfarmer.com no-till production?” http://attra.ncat.org/ calendar/question.php/2006/05/08/p2221. To contact the manufacturer of commercially available cover crop rollers, visit www.croproller.com.

No-till vegetable transplanting. Vetch that is Herbicides will kill vetch in three to 30 days, suppressed or killed without disturbing the soil depending on the material used, rate, growth maintains moisture well for transplanted vegeta- stage and weather conditions. bles. No-till innovator Steve Groff of Lancaster Vetch incorporation. As a rule, to gauge the County, Pa., uses the rolling stalk chopper to cre- optimum hairy vetch kill date, credit vetch with ate a killed organic mulch. His favorite mix is 25 adding two to three pounds of N per acre per lb. hairy vetch, 30 lb. rye sunny day after full spring growth begins. Usually, Winter hardy and 10 lb. crimson N contribution will be maximized by early bloom (10-25 percent) stage. through the clover/A. No-till, delayed kill. Cutting hairy vetch close to the ground at full warmer parts of Farmers and researchers bloom stage usually will kill it. However, waiting are increasingly using a this long means it will have maximum top Zone 4, few roller/crimper to kill growth, and the tangled mass of mature vetch can legumes can rival hairy vetch and other overwhelm many smaller mowers or disks. Flail cover crops (11). Jeff mowing before tillage helps, but that is a time and hairy vetch’s N Moyer and others at the horsepower intensive process. Sickle-bar mowers Rodale Institute in should only be used when the vetch is well sup- contributions. Kutztown, Pa., roll hairy ported by a cereal companion crop and the mate- vetch and other cover rial is dry (422). crops in late May or early June (at about 50% flower). The modified Management Cautions roller is front-mounted, and corn is no-tilled on About 10 to 20 percent of vetch seed is “hard” the same pass (303). See Cover Crop Roller seed that lays ungerminated in the soil for one or Design Holds Promise For No-Tillers, p. 146. more seasons. This can cause a weed problem, Also useful in killing hairy vetch on raised beds especially in winter grains. In wheat, a variety of for vegetables and cotton is the improved proto- herbicides are available, depending on crop type of an undercutter that leaves severed residue growth stage. After a corn crop that can utilize virtually undisturbed on the surface (96). The the vetch-produced N, you could establish a hay undercutter tool includes a flat roller attachment, or pasture crop for several years. which, by itself, usually provides only partial sup- Don’t plant hairy vetch with a winter grain if pression unless used after flowering. you want to harvest grain for feed or sale.

148 MANAGING COVER CROPS PROFITABLY Production is difficult because vetch vines will and minute pirate bugs (Orius tristicolor). pull down all but the strongest stalks. Grain cont- Two insects may reduce hairy vetch seed yield amination also is likely if the vetch goes to seed in heavy infestations: the vetch weevil or vetch before grain harvest. Vetch seed is about the same bruchid. Rotate crops to alleviate buildup of these size as wheat and barley kernels, making it hard pests (361). and expensive to separate during seed cleaning (361). Grain price can be markedly reduced by CROP SYSTEMS only a few vetch seeds per bushel. A severe freeze with temperatures less than In no-till systems, killed hairy vetch creates a 5° F may kill hairy vetch if there is no snow cover, short-term but effective spring/summer mulch, reducing or eliminating the stand and most of its especially for transplants. The mulch retains mois- N value. If winterkill is possible in your area, plant- ture, allowing plants to use mineralized nutrients ing vetch with a hardy grain such as rye ensures better than unmulched fields. The management spring soil protection. challenge is that the mulch also lowers soil temperature, which may delay early season growth Pest Management (361). One option is to capitalize on high quality, In legume comparison trials, hairy vetch usually low-cost tomatoes that capture the late-season hosts numerous small insects and soil organisms market premiums. See Vetch Beats Plastic (206). Many are beneficial to crop production, (p. 150). (see below) but others are pests. Soybean cyst How you kill hairy vetch Mix hairy vetch nematode (Heterodera glycines) and root-knot influences its ability to nematode (Meliodogyne spp.) sometimes suppress weeds. Durability with cereal increase under hairy vetch. If you suspect that a and effectiveness as a light- grains to field has nematodes, carefully sample the soil after blocking mulch are great- hairy vetch. If the pests reach an economic est where the stalks are left reduce the risk threshold, plant nematode-resistant crops and whole. Hairy vetch severed consider using another cover crop. at the roots or sickle-bar of N leaching. Other pests include cutworms (361) and south- mowed lasts longer and ern corn rootworm (67), which can be problems blocks more light than in no-till corn, tarnished plant bug, noted in flailed vetch, preventing more weed seeds from coastal Massachusetts (56), which readily dispers- germinating (96, 411). es to other crops, and two-spotted spider mites in Southern farmers can use an overwintering Oregon pear orchards (142). Leaving unmowed hairy vetch crop in continuous no-till cotton. remnant strips can lessen movement of disruptive Vetch mixed with rye has provided similar or pests while still allowing you to kill most of the even increased yields compared with systems cover crop (56). that include conventional tillage, winter fallow Prominent among beneficial predators associ- weed cover and up to 60 pounds of N fertilizer ated with hairy vetch are lady beetles, seven-spot- per acre. Typically, the cover crops are no-till ted ladybeetles (56) and bigeyed bugs (Geocaris drilled after shredding cotton stalks in late spp.). Vetch harbors pea aphids (Acyrthosiphon October. Covers are spray killed in mid-April pisum) and blue alfalfa aphids (Acyrthosiphon ahead of cotton planting in May. With the relative- kondoi) that do not attack pecans but provide a ly late fall planting, hairy vetch delivers only part food source for aphid-eating insects that can disperse into pecans (58). Similarly, hairy vetch blos- Note:An unmowed rye/hairy vetch mix sustained soms harbor flower thrips (Frankliniella spp.), a population of aphid-eating predators that was which in turn attract important thrip predators six times that of the unmowed volunteer weeds such as insidious flower bugs (Orius insidiosus) and 87 times that of mown grass and weeds (57).

HAIRY VETCH 149 Vetch Beats Plastic

BELTSVILLE, Md.—Killed cover crop mulches • Transplant seedlings using a minimum tillage can deliver multiple benefits for no-till planter able to cut through the mulch and vegetable crops (1, 2, 3, 4). The system can firm soil around the plants. provide its own N, quell erosion and leaching, and displace herbicides. It’s also The hairy vetch mulch suppresses early season more profitable than conventional weeds. It improves tomato health by commercial production using black plastic preventing soil splashing onto the plants, and mulch. A budget analysis showed it also keeps tomatoes from soil contact, improving should be the first choice of “risk averse” quality. Hairy vetch-mulched plants may need farmers, who prefer certain although more more water. Their growth is more vigorous and modest profit over higher average profit that may yield up to 20 percent more than those is less certain (224). on plastic. Completing harvest by mid- The key to the economic certainty of a September allows the field to be immediately successful hairy vetch planting is its low cost reseeded to hairy vetch. Waiting for vetch to compared with the black plastic purchase, bloom in spring before killing it and the tight installation and removal. fall turnaround may make this system less From refining his own research and on-farm useful in areas with a shorter growing season tests in the mid-Atlantic region for several than this Zone 7, mid-Atlantic site. years, Aref Abdul-Baki, formerly of the USDA’s Abdul-Baki rotates season-long cash crops of Beltsville (Md.) Agricultural Research Center, tomatoes, peppers and cantaloupe through the outlines his approach: same plot between fall hairy vetch seedings. He • Prepare beds—just as you would for planting shallow plows the third year after cantaloupe tomatoes—at your prime time to seed hairy harvest and seeds hairy vetch for flat-field crops of vetch. sweet corn or snap beans the following summer. • Drill hairy vetch at 40 lb./A, and expect He suggests seeding rye (40 lb./A) with the about 4 inches of top growth before vetch for greater biomass and longer-lasting dormancy, which stretches from mid- mulch. Adding 10-12 lb./A of crimson clover December to mid-March in Maryland. will aid in weed suppression and N value. • After two months’ spring growth, flail mow Rolling the covers before planting provides or use other mechanical means to suppress longer-lasting residue than does mowing them. the hairy vetch. Be ready to remow or use Some weeds, particularly perennial or winter herbicides to clean up trouble spots where annual weeds, can still escape this mixture, hairy vetch regrows or weeds appear. and may require additional management (4). of its potential N in this system. It adds cost, but Other Options supplies erosion control and long-term soil Spring sowing is possible, but less desirable than improvement (35). fall establishment because it yields significantly Cotton yields following incorporated hairy less biomass than overwintering stands. Hot vetch were perennial winners for 35 years at a weather causes plants to languish. northwestern Louisiana USDA site. Soil organic Hairy vetch makes only fair grazing—livestock matter improvement and erosion control were do not relish it. additional benefits (276).

150 MANAGING COVER CROPS PROFITABLY Harvesting seed. Plant hairy vetch with grains if Cultivars. MADISON—developed in Nebraska— you intend to harvest the vetch for seed. Use a tolerates cold better than other varieties. Hairy moderate seeding rate of 10-20 lb./A to keep the vetches produced in Oregon and California tend stand from getting too rank. Vetch seed pods will to be heat tolerant. This has resulted in two appar- grow above the twining vetch vines and use the ent types, both usually sold as “common” or “vari- grain as a trellis, allowing you to run the cutter bar ety not stated” (VNS). One has noticeably hairy, higher to reduce plugging of the combine. Direct bluish-green foliage with bluish flowers and is combine at mid-bloom to minimize shattering, or more cold-tolerant. The other type has smoother, swath up to a week later. Seed is viable for at least deep-green foliage and pink to violet flowers. five years if properly stored (361). A closely related species—LANA woollypod If you want to save dollars by growing your vetch (Vicia dasycarpa)—was developed in own seed, be aware that the mature pods shatter Oregon and is less cold tolerant than Vicia vil losa. easily, increasing the risk of volunteer weeds. To Trials in southeastern Pennsylvania with many keep vetch with its nurse crop, harvest vetch with accessions of hairy vetch showed big flower a winter cereal and keep seed co-mingled for vetch (Vicia grandiflora, cv WOODFORD) was the planting. Check the mix carefully for weed seeds. only vetch species hardier than hairy vetch. EARLY COVER hairy vetch is about 10 days earlier than COMPARATIVE NOTES regular common seed. PURPLE BOUNTY, released in 2006, is a few days earlier and provides more bio- Hairy vetch is better adapted to sandy soils than crim- mass and better ground cover than EARLY COVER. son clover (344), but is less heat-tolerant than LANA woollypod vetch. See Woollypod Vetch (p. 185). Seed sources. See Seed Suppliers (p. 195).

HAIRY VETCH 151 MEDICS Medicago spp.

Also called: black medic, burr (or bur) medic, burclover

Type: Winter annual or summer annual legume

Roles: N source, soil quality builder, weed suppressor, erosion fighter

Mix with: Other medics; clovers and grasses; small grains

See charts, p. 66 to 72, for ranking and management summary.

nce established, few other legumes out - tall, is semi-erect or prostrate, hairless, and offers perform medics in soil-saving, soil-build- great seed production and N-fixing ability; barrel Oing and—in some systems—forage, when medic (M. truncatula), about 16 inches tall, with summer rainfall is less than 15 inches. They serve many mid-season cultivars; and snail medic (M. well in seasonally dry areas from mild California scutellata), which is a good biomass and N pro- to the harsh Northern Plains. With more rainfall, ducer. however, they can pro duce almost as much bio- Southern spotted burr medic is a native M. poly- mass and N as clovers. Perennial medics are self- mor pha cultivar with more win terhardiness than reseeding with abundant “hard seed” that can take most of the current burr medics, which are several years to germinate. This makes medics imported from Australia. See Southern Burr ideal for long rotations of forages and cash crops Medic Offers Reseeding Persistence (p. 154). in the Northern Plains and in cover crop mixtures Naturalized burr medic seed is traded locally in in the drier areas of California. California. Annual medics include 35 known species Annual medics broadcast in spring over wheat that vary widely in plant habit, maturity date and stubble in Michigan reduced weed number and cold tolerance. Most upright varieties resemble growth of spring annual weeds prior to no-till alfalfa in their seeding year with a single stalk and corn planting the following spring. Spring-planted short taproot. Medics can produce more than 100 annual medics produced dry matter yields similar lb. N/A in the Midwest under favorable condi- to or greater than alfalfa by July (373, 376). tions, but have the potential for 200 lb. N/A where Black medic (M. lupulina) is usually called a the plants grow over winter. They germinate and perennial. It can improve soil, reduce dis eases, grow quickly when soil moisture is adequate, save moisture and boost grain protein when forming a thick ground cover that holds soil in grown in rotations with grains in the Northern place. The more prostrate species of annual medic Plains. GEORGE is the most widely used cultivar in provide better ground cover. dryland areas of the Northern Plains. Black medic Significant annual types include: burr medic produces abundant seed. Up to 96 percent of it is (M. polymorpha), which grows up to 14 inches hard seed, much of it so hard seed ed that it won’t

152 MANAGING COVER CROPS PROFITABLY Jess Counts on GEORGE for N and Feed

STANFORD, Mon.—Jess Alger can count on stand of GEORGE medic. The medic/wheat 13 inches of rainfall or less on his central interplant yielded 29 bushels per acre—six Montana farm, occasional hail damage, too few bushels less than the other field. But the solar units to raise safflower or millet, some interplanted grain tested at 15 percent protein, bone-chilling winters without snow cover— a full percentage point higher. Those are high and George. That’s GEORGE black medic. yields for Alger’s area, partly due to timely On-farm tests showed he got 87 lb. N/A and summer rain. “The yield drop with medic was 3 percent organic matter on his Judith clay mostly a weed problem with Persian darnel,” loam soils. He initially seeded the medic on 10- Alger explains, “but I now have that mostly inch row spacings with barley at 10 lb./A, his under control.” standard rate and seeding method. He grazed Jess continues to fine-tune his system to the medic early in the second year, and then let maximize income and weed management. He it go to seed. In Year 3, he sprayed it with became certified organic in 1999. He maintains glyphosate in order to establish a sorghum- the medic seed bank with no-till plantings of sudangrass hybrid as emergency forage on May GEORGE with a nurse crop of Austrian winter 15. He had several inches of growth when frost peas. He is experimenting successfully with rye hit about June 10 and killed the tender grass. instead of summer fallow. The medic came on strong. He let it mature If weed pressure is high, medic fields are to its full 12 inches to harvest it for seed. “It grazed closely to prevent weeds from going to was already laying over, but the pickup guards seed, then plowed. Otherwise, he no-tills on my combine helped to gather in about half winter wheat into standing medic so he can the seed.” The other half pumped up the seed leave most of the medic in place, bury less bank for years ahead. seed and allow GEORGE to rest more securely He did a comparison with side-by-side fields in his field. of spring wheat. One followed a spring wheat Updated in 2007 by Andy Clark crop, the other he planted into a six-year-old germinate for two years. Second-year growth may medic increased spring wheat yield by about 92 be modest, but coverage improves in years three percent compared with spring wheat following and four after the initial seeding if competition is fallow, and also appreciably raised the grain pro- not excessive (422) and grazing management is tein level (379). GEORGE grows in a prostrate to timely. ascending fashion and overwinters well with snow cover in the Northern Plains. BENEFITS April soil N value after black medic in one Montana test was 117 lb./A, about 2.5 times the Good N on low moisture. In dryland areas, fallow N level and the best of six cultivars tested, most legumes offer a choice between N produc - all of which used less water than the fallow treat- tion and excessive water use. Medics earn a place ment (378). In North Dakota, however, unrestrict- in dryland crop rotations because they provide N ed medic growth depressed yield of a following while conserving moisture comparable to bare- wheat crop (73). ground fallow (230, 380). Fallow is the intention al resting of soil for a sea- Great N from more water. Under normal dry - son so it will build up moisture and gain fertility land conditions, medics usually produce about 1 T by biological break down of organic matter. Black dry matter/A, depending on available soil mois -

MEDICS 153 Southern Spotted Burr Medic Offers Reseeding Persistence

While annual medics, in general, are hard medic cultivar CIRCLE VALLEY successfully seeded, they usually cannot tolerate winters reseeded in a Louisiana no-till cotton field for north of the Gulf South. Southern spotted burr more than 10 years without special medic (Medicago arabica) shows promise as management to maintain it (103). a winter legume that can reseed for several Research in the Southeast showed that if years from a single seed crop in Hardiness Southern spotted burr medic begins blooming Zone 7 of the Southeast. March 23, it would form viable seed by May 2, Once as widely grown as hairy vetch in the and reach maximum seed formation by May mid-South region of the U.S., burr medic 12. By allowing the cover crop to grow until persists in non-cropland areas because it is 40 to 50 days after first bloom and managing well adapted to the region (326, 327). A local the cropping system without tillage that accession collected in northern Mississippi would bury burclover seeds too deeply, exhibits better cold hardiness and insect Southern spotted burclover should resistance than commercially available successfully reseed for several years. (Australian) annual medics. Native medic seed is being increased in In a replicated cold-hardiness trial spanning cooperation with the USDA-Natural Resources several states, spotted burr medic flowered in Conservation Service’s Jamie Whitten Plant mid-March, about two weeks after SERENA, Materials Center, Coffeeville, Miss., for possible CIRCLE VALLEY or SANTIAGO burclover, but two accelerated release to seed growers as a weeks before TIBBEE crimson clover. The burr “source-identified” cover crop. medic flowered over a longer period than Insect pests such as clover leaf weevil crimson, matured seed slightly sooner than (Hypera punctata Fabricius) and the alfalfa TIBBEE but generally did not produce as much weevil (Hypera postica Gyllenhal) biomass. preferentially attack medics over other winter The big advantage of spotted burr medic legume cover crops in the Southeast, and over crimson clover was its ability to reseed could jeopardize seed production. These for several years from a single seed crop. In insects are easily controlled with pyrethroid studies in several states, the native medic insecticides when weevils are in their second successfully reseeded for at least two years instar growth stage. While not usually needed when growth was terminated two weeks after for single-season cover crop benefits, insect- TIBBEE bloomed. Only balansa clover (see Up- icides may be warranted in the seeding year to and-Coming Cover Crops, p. 191) reseeded as ensure a reseeding crop for years to come. well as spotted burclover (105). The burr ture and fertility. When moisture is abundant, stand. In California orchards and vineyards where medics can reach their full potential of 3 T/A of winters are rainy instead of frigid, medics mixed 3.5 to 4 percent plant-tissue nitrogen, contribut - with other grasses and legumes provide a contin - ing more than 200 lb. N/A (201, 422). uous cover that crowds out weeds. In those situa - tions, medics help reduce weed seed production Fight weeds. Quick spring regrowth suppresses for the long-term. early weeds. Fall weeds are controlled by medic regrowth after harvest, whether the medic stand Boost organic matter. Good stands of medics in is overseeded or interplanted with the grain, or well drained soil can contribute sufficient residue the grain is seeded into an established medic to build soil organic matter levels. One Indiana

154 MANAGING COVER CROPS PROFITABLY Hard-seeded test reported a yield of benefit. GEORGE black medic is medics are ideal more than 9,000 lb. dry prostrate, allowing other grasses matter/A from a spring- and forbs to become the over- for reseeding sown barrel medic (164). story for grazing. It is well- Reduce soil erosion. suited to cold winter systems in Medics can survive in areas of Hardiness orchards and sum mer drought-prone Zone 4, where it can areas where few other stay green much of vineyards. culti vated forage legumes the winter (6). would, thanks to their Quick starting. Black hard-seeded tendency medic can germinate and drought tolerance. Low, dense vegetation with in three days of breaks raindrop impact while roots may pene- planting (286). About trate 5 feet deep to hold soil in place. 45 days after mid- April planting in south- Tolerate regular mowing. Medics can be grazed ern Illinois, two annual or mowed at intervals with no ill effects. They medics were 20 inch- should be mowed regularly to a height of 3 to 5 es tall and blooming.

inches during the growing season for best seed set In the upper Mid - Sears Elayne and weed suppression. To increase the soil seed west, snail and burr BLACK MEDIC bank, rest medic from blooming to seed maturation, medics achieve peak (Medicago lupulina) then resume clipping or grazing (285, 422, 435). biomass about 60 days after planti ng. An early August seeding of the Provide good grazing. Green plants, dry plants annuals in southern Illinois germinated well, and burs of burr medic provide good forage, but stopped grow ing during a hot spell, then restart- solid stands can cause bloat in cattle (422). The ed. Growth was similar to the spring-planted plots burs are concentrated nutrition for winter forage, by September 29 when frost hit. The plants stayed but lower the value of fleece when they become green until the temperature dipped to the upper embedded in wool. Annual medics overseeded teens (201). into row crops or vegetables can be grazed in fall after cash crop harvest (376). Widely acclimated. Species and cultivars vary by up to seven weeks in their estimated length of Reseeding. Black medic has a high percentage of time to flowering. Be sure to select a species to fit hard seed. Up to 90 percent has an outer shell that your weather and crop rotation. resists the softening by water and soil chemicals that triggers germination (286). Scarified seed will MANAGEMENT achieve 95 percent germination, and 10-year old raw seed may still be 50 percent viable (422). Burr Establishment medic seed in the intact bur remains viable for a Annual medics offer great potential as a substitute longer time than hulled seed (120). for fallow in dry northern regions of the U.S. with Their status as a resilient, reseeding forage longer day length. Annual medics need to fix as makes medics the basis for the “ley system” devel- much N as winter peas or lentils and have a com - oped in dry areas of Australia. Medics or subter- petitive establishment cost per acre to be as valu - ranean clover pastured for several years on able as these better-known legume green Australian dry-lands help to store moisture and manures (383). build up soil pro ductivity for a year of small grain Medics are widely adapted to soils that are rea - production before being returned to pasture. This sonably fertile, but not distinctly acid or alkaline. use requires live stock for maximum economic Excessive field moisture early in the season can

MEDICS 155 significantly reduce medic stands (373). Acid-tol - Where medic and corn work together, such as erant rhizobial strains may help some cool-season California, maximize medic survival during the medics, especially barrel medic, to grow on sites corn canopy period by seeding early (when corn that otherwise would be inhospitable (422). is eight to 16 inches tall) and heavy (15 to 20 To reduce economic risk in fields where you’ve lb./A) to build up medic root reserves (47, 422). never grown medic, sow a mixture of medics • After wheat harvest. MOGUL barrel medic with variable seed size and maturation dates. In seeded after wheat harvest produced 119 lb. N/A dry areas of California, medic monocultures are in southern Michigan, more than double the N planted at a rate of 2 to 6 lb./A, while the rate with production of red clover seeded at the same time grasses or clovers is 6 to 12 lb./A (422). (373). In Montana, mid-season establishment of Establishment options vary depending on cli- snail medic after wheat works only in years with mate and crop system: adequate precipitation, when it smothers weeds, 1 1 • Early spring—clear seed. Drill /4 to /2 builds up N, then winterkills for a soil-holding inch deep (using a double-disk or hoe-type drill) organic mulch (72). into a firm seed bed as • Autumn seeding.Where winters are rainy in Medics earn a you would for alfalfa. California, medics are planted in October as win - place in dryland Rolling is recommend- ter annuals (436). Plant about the same time as ed before or after seed- crimson clover in the Southeast, Zones 7 and 8. rotations because ing to improve seed-soil contact and moisture in Killing they provide N the seed zone. Seeding Medics are easy to control by light tillage or her- while conserving rate is 8 to 10 lb./A for bicides. They reseed up to three times per sum- black medic, 12 to 20 mer, dying back naturally each time. Medics in the moisture. lb./A for larger-seeded vegetative stage do not tolerate field traffic. (snail, gamma and burr) annual medics. In the Field Management arid Northern Plains, fall germination and winter Black medic>small grain rotations developed in survival are dependable, although spring planting Montana count on successful self-reseeding of also has worked. medic stands for grazing by sheep or cattle. A • Spring grain nurse crop. Barley, oats, month of summer grazing improves the econom - spring wheat and flax can serve as nurse crops for ics of rotation by supplying forage for about one medic, greatly reducing weed pressure in the animal unit per acre. In this system, established seeding year. The drawback is that nurse crops self-reseeding black medic plowed down as green will reduce first-year seed production if you are manure in alternate years improved spring wheat trying to establish a black medic seed bank. To yield by about 50 percent compared to fallow increase the soil seed reserve for a long-term (380). black medic stand (germinating from hard seed), Black medic is a dual-use legume in this adapt - allow the medic to blossom, mature and reseed ed “ley” system. Livestock graze the legume in the during its second year. “medic years” when the cover crop accumulates • Corn overseed. SANTIAGO burr medic and biomass and contributes N to the soil. Cash crops SAVA snail medic were successfully established in can be no-tilled into killed medic, or the legume no-till corn three to six weeks after corn planting can be incorporated. during a two-year trial in Michigan. Corn yield was A well-established black medic stand can reduced if medics were seeded up to 14 days after reduce costs compared with annual crops by corn planting. Waiting 28 days did not affect corn coming back for many years. However, without yield, but medic biomass production was reduced the livestock grazing benefit to supply additional by 50% (219). utilization, water-efficient legumes such as lentils

156 MANAGING COVER CROPS PROFITABLY and Austrian winter peas will probably be more window with a late frost could give both forage effective N sources. Further, the long-lived seed and N-bearing residue, protecting soil and adding bank that black medic establishes may be unde - spring fertility. Take steps to reduce weed pres- sirable for some cash crop rotations (383). sure in solid seedings, especially in early July. Use of medics for grain production in the In another Michigan comparison, winter canola upper Midwest has given inconsistent results. (Brassica napus) yields were similar after a green Berseem clover may be a better choice in many manure comparison of two medics, berseem situations. In a series of trials in Ohio, Michigan, clover and NITRO annual Wisconsin and Minnesota, medic sometimes alfalfa. All the covers were With abundant reduced corn yield and did not provide enough clear (sole-crop) seeded in moisture, weed control or N to justify its use under current early May after pre-plant cash grain prices, even when premiums for pesti- incorporated herbi cide medics can cide-free corn were evaluated (141, 219, 373, 374, treatment, and were 376, 456, 457). One Michigan farmer’s situation is plowed down 90 days later. produce more fairly typical. He established annual medic at 10 Harvesting the medics at 60 than 200 lb. lb./A when his ridge-tilled corn was about knee- days as forage did not sig- high. The legume germinated, but didn’t grow nifi cantly lessen their green N/A. well or provide weed suppression until after manure value (373). corn dry-down in mid-September. The medic put In the mid-Atlantic at the on about 10 inches of growth before win- USDA Beltsville, Md. site, medics have been diffi- terkilling, enough for effective winter ero sion pro- cult to establish by over-seeding at vegetable tection (201). planting or at final cultiva tion of sweet corn. Black medic and two annual medics produced 50 to 150 lb. N/A when interplanted with stan- Pest Management dard and semi-dwarf barley in a Minnesota trial. Under water logged conditions for which they are Annual MOGUL produced the most biomass by ill-suited, annual medics are susceptible to dis eases fall, but also reduced barley yields. GEORGE was like Rhizoctonia, Phytophthora and Fusarium. the least competitive and fixed 55 to 120 lb. N/A. Burr medic harbors abundant lygus bugs in The taller barley was more competitive, indicating spring. It also appears to be particularly prone to that taller small grain cultivars should be used to outbreaks of the two-spotted spider mite, a pest favor grain pro duction over medic stand develop- found in many West Coast orchards (422). ment (289). Pods and viable seeds develop without pollina - Midwestern farmers can overseed annual tors because most annual medics have no floral medic or a medic/grass mixture into wheat in nectaries (120). very early spring for excellent early summer graz - ing. With timely moisture, you can get a hay cut - COMPARATIVE NOTES ting within nine to 10 weeks after germination, and some species will keep working to produce a Snail medic produced about the same biomass second cutting. Regrowth comes from lateral and N as red clover when both legumes were stems, so don’t clip or graze lower than 4 or 5 spring sown with an oats nurse crop into a disked inches if you want regrowth. To avoid bloat, man- seedbed in Wisconsin. Yields averaged over one age as you would alfalfa (201). wet year and one dry year were about 1 T dry mat - Annual medics can achieve their full potential ter and 60 lb. N/A (141). when planted after a short-season spring Medics can establish and survive better than crop such as processing peas or lettuce. subterranean clover in times of low rainfall, and Wisconsin tests at six locations showed medic are more competitive with grasses. A short peri- produced an average of 2. 2 T/A when sown in the od of moisture will allow medic to germinate and late June or early July (399). Early planting in this send down its fast-growing taproot, while sub-

MEDICS 157 clover needs more consistent mois ture for its shal- crops in several years of trials run from northern lower, slower growing roots (422). Medics are California into Mexico in the 1990s. While some more susceptible than subclover to seed produc- of the naturalized strains have been self-reseeding tion loss from closely mowing densely planted for 30 years in some orchards, Extension special - erect stalks. Burr and barrel medics are not as ists say the commercial cultivars may be prefer- effective as subclover at absorbing phosphorus able because they are widely avail able and better (422). documented. Medics may survive where true clovers Established burr medic tolerates shade as a (Trifolium spp.) fail due to droughty conditions com mon volunteer in the understories of (422) if there is at least 12 in. of rain per year California walnut orchards, which are heavily (292). shaded from April through November. However, Medics grow well in in Michigan trials over several years, SANTIAGO (a Medics are easy mixtures with grasses and burr medic with no spines on its burs) failed to clovers, but don’t per- to kill with light establish sat isfactorily when it was overseeded form well with red clover into corn and soybeans at layby. Researchers sus- tillage or most (422, 263). Once estab- pect the crop canopy shaded the medic too soon lished, black medic han- after planting, and that earlier overseeding may herbicides. dles frost better than have allowed the medic to establish. crimson or red clover. There are at least 10 cultivars of barrel medic. GEORGE grows more Dates of first flowering for barrel medics range slowly than yellow blos som sweetclover in spring from 80 to 105 days after germination, and seed of the second year, but it starts flowering earlier. It count per pound ranges from 110,000 for uses less water in the 2- to 4-foot depth than HANAFORD to 260,000 for SEPHI (422). A leading sweetclover, soybeans or hairy vetch seeded at new cultivar, SEPHI, flowers about a week earlier the same time. than JEMALONG, commonly used in California (251, 422).SEPHI, a mid-season cultivar, has a more erect Annual Medic Cultivars. Species and cultivars habit for better winter production, is adapted to of annual medic vary significantly in their dry mat - high- and low-rainfall areas, yields more seed and ter production, crude protein concentration and biomass than others, has good tolerance to total N. Check with local or regional forage spe- Egyptian alfalfa weevil and high tolerance to spot - cialists for cultivar recommendations ted alfalfa aphid and blue green aphid. It is sus - Burr medic (also called burclover) cultivars ceptible to pea aphid. are the best known of the annual medics. They Snail medic (M. scutellata) is a prolific seed branch profusely at the base, and send out pros - producer. Quick germination and maturity can trate stems that grow more erect in dense stands lead to three crops (two reseedings) in a single (422). They grow quickly in response to fall season from a spring planting in the Midwest California rains and fix from 55 to 90 lb. N/A, near - (373). MOGUL barrel medic grew the most bio- ly as much as true clovers (294, 422). Most stands mass in a barley intercrop, compared with are volunteer and can be encouraged by proper SANTIAGO burr medic and GEORGE black medic in grazing, cultivation or fertilization. a four-site Minnesota trial. It frequently reduced Selected cultivars include SERENA (an early barley yields, particularly those of a semi-dwarf bloomer), and CIRCLE VALLEY, both of which have barley variety, but increased weed suppression fair tolerance to Egyptian alfalfa weevil (435). and N and biomass production (289). SANTIAGO blooms later than SERENA. Early burr In a Michigan test of forage legumes for emer- medics flower in about 62 days in California, rang- gency forage use, MOGUL barrel medic pro duced ing up to 96 days for mid-season cultivars (422). 1.5 T dry matter/A com pared to about 1 T/A for Naturalized and imported burr medic proved SAVA snail medic and SANTIAGO burr medic (M. the best type of burclover for self-reseeding cover polymorpha). Nitrogen pro duction was 66 lb./A

158 MANAGING COVER CROPS PROFITABLY for MOGUL, 46 for SAVA and 22 for SANTIAGO. The tial seeding. GAMMA medic (M. rugosa) had the seeding rate for SAVA medic is 29 lb./A, more than highest first-year seed production but re-estab - twice the 13 lb./A recommended for clear seed- lished poorly, apparently due to a low hard seed ings of MOGUL and SANTIAGO (373, 376). content. All the medics re-established better In a California pasture comparison of three under permanent pasture than under any rota - annual medics, JEMALONG barrel had the highest tional system involving tillage (94, 422). level of seed reserves in the soil after six years, but didn’t continue into the seventh year after the ini - Seed sources. See Seed Suppliers (p. 195).

RED CLOVER Trifolium pratense

Also called: medium red clover (multi-cut, early blooming, June clover); mammoth clover (single cut, late blooming, Michigan red)

Type: short-lived perennial, biennial or winter annual legume

Roles: N source, soil builder, weed suppressor, insectary crop, forage

Mix with: small grains, sweetclover, corn, soy beans, vegetables, grass forages

See charts, p. 66 to 72, for rankings and management summary.

ed clover is a dependable, low-cost, readily BENEFITS available workhorse that is winter hardy in Rmuch of the U.S. (Hardiness Zone 4 and Crop fertility. As a cover crop, red clover is used warmer). Easily overseeded or frostseeded into primarily as a legume green manure killed ahead standing crops, it creates loamy topsoil, adds a of corn or vegetable crops planted in early sum- moderate amount of N, helps to suppress weeds mer. Full-season, over-wintered red clover can pro- and breaks up heavy soil. Its most common uses duce 2 to 4 T dry matter/A and fix 70 to 150 lb. include forage, grazing, seed harvest, plowdown N N/A. In Ohio, over-wintered mammoth and medi- and, in warmer areas, hay. It’s a great legume to um red clover contained about 75 lb. N/A by May frostseed or interseed with small grains where 15, increasing to 130 lb. N by June 22 (366). you can harvest grain as well as provide weed Two years of testing in Wisconsin showed that suppression and manage N. conventionally planted corn following red clover

RED CLOVER 159 yielded the same as corn supplied with 160 lb. Red clover was the most profitable of five N/A, with less risk of post-harvest N leaching. legumes under both seeding methods in the Corn and the soil testing showed that 50 percent trial—sequentially planted after oats harvest or of the cover crop N was released in the first companion planted with oats in early spring. The month after incorporation, corresponding well companion seedings yielded nearly twice as with corn’s fertility demand. Post-harvest soil N much estimated fertilizer replacement value as levels in the clover plots were the same or less the sequential seedings. The work showed that than the fertilized plots, and about the same as red clover holds great potential to reduce fertiliz- unfertilized plots (401). er N use for corn grown in rotation (401). In Michigan, red clover frost-seeded into winter Widely adapted. While many other legumes can wheat suppressed common ragweed growth grow quicker, produce more biomass and fix through wheat harvest and into the summer. The more nitrogen, few are adapted to as many soil red clover did not provide complete ragweed types and temperate climatic niches as red clover. control, but there was no adverse effect on wheat As a rule, red clover grows well wherever corn yield (297). grows well. It does Red clover sown as a companion with spring Red clover can best in cool condi- oats outperformed the other leg umes, which suf- tions. fered from insect damage, mechanical damage yield 2 to 3 tons of In southern Canada during oat harvest and slow subsequent dry matter and 70 and the northern U.S., regrowth. The short season proved inadequate for and in the higher ele- sequentially seeded legumes with the exception to 150 lb. N/A vations of the South - of hairy vetch, which was nearly as profitable as east and West, red the red clover (400). clover grows as a bien- The role of red clover’s N contribution in the nial or short-lived perennial. At lower elevations in rotation grew more significant as N prices the Southeast, it grows as a winter annual, and at increased in the late 1990s (and 2007!), even lower elevations in the West and Canada, it grows though clover seed price also increased from the under irrigation as a biennial (120). It grows in orig inal 1989 calculations (398). any loam or clay soil, responding best to well- drained, fertile soils, but also tolerates less well- Soil conditioner. Red clover is an excellent soil drained conditions. conditioner, with an extensive root system that permeates the topsoil. Its taproot may penetrate Many economic uses. Red clover has been a several feet. popular, multi-use crop since European immigrant farmers brought it to North America in the 1500s. Attracts beneficial insects. Red clover earned a It remains an important crop thanks to its greater co-starring role with LOUISIANA S-1 white clover adaptability, lower seeding cost and easier estab - in pecan orchard recommendations from lishment than alfalfa. It can produce up to 8,000 Oklahoma State University. Red clover attracts lb. biomass/A. more beneficials than white clover, which fea- A red clover/small grain mix has been a tradi - tures high er N fixation and greater flood toler- tional pairing that continues to be profitable. A ance than red clover (261). rotation of corn and oats companion-seeded with red clover proved as profitable as continuous Two Types corn receiving 160 lb. N/A in a four-year Two distinct types of red clover have evolved Wisconsin study (400). For more information, see from the same species. Be sure you plant a multi- the Wisconsin Integrated Cropping Systems Trial cut culti var if you plan to make more than one (449) and the final report of this project, partially green manure cutting, or to main tain the stand to funded by SARE (328). prepare for a late-summer veg etable planting.

160 MANAGING COVER CROPS PROFITABLY Medium red clover. Medium red (some call it Red clover’s tolerance of shade and its ability to multi-cut) grows back quickly, and can be cut germinate down to 41° F give it a remarkable once late in the seeding year and twice the fol - range of establishment niches. lowing year. For optimum N benefit and flexible It can be overseeded at 10 to 12 lb./A into: cropping options from the planting (allowing it to • Dormant winter grains before ground overwinter as a soil-protecting mulch), you can thaws. This “frostseeding” method relies on move - use it for hay, grazing or seed throughout the sec- ment of the freeze-thaw cycle to work seed into suf- ond season. Seed may be up to 25 percent more ficient seed-soil contact for germination. If the soil is expensive than single-cut. See Chart 3B: Planting level and firm, you can broadcast seed over snow (p. 70). cover on level terrain.You can seed the clover with Mammoth red clover produces significant urea if fertilizer application is uniform (229). Use bio mass and as much N as medium red in a single just enough N fertilizer to support proven small- first cutting, but does not produce as much total grain yields, because excess N application will hin- biomass and N as medium red’s multiple cuttings der clover establishment. To reduce small grain over time. Use this “single-cut” red clover where a competition with clover in early spring, graze or field will be all-clover just during the seeding year. clip the small grain in early spring just before the Slow-growing mammoth doesn’t bloom the estab- stems begin to grow (120). Hoof impact from graz- lishment year and regrows quite slowly after cut- ing also helps ensure seed-to-soil contact. ting, but can provide good bio mass by the end of • Summer annuals such as oats, barley, spelt even one growing season. or spring wheat before grain emergence. A single cutting of mammoth will give slightly • Corn at layby. Wait until corn is 10 to 12 more biomass—at a slightly lower cost—than a inches tall, and at least 6 weeks (check labels!) single cutting of medium red. Where multiple cut- after application of pre-emergent herbicides such tings or groundcover are needed in the second as atrazine. Clover sown earlier in favorable cool- season, medium red clover’s higher seed cost is er conditions with more light may compete too easily justified (197). much for water. Later, the clover will grow more Some types of mammoth do better overseeded slowly and not add substantial biomass until after into wheat than into oats. ALTASWEDE (Canadian) corn harvest lets light enter (197). Dairy produc- mammoth is not as shade tolerant as MICHIGAN ers often broadcast red clover after corn silage mammoth, but works well when seeded with harvest. oats. MICHIGAN mammoth shows the best vigor • After wheat harvest. Red clover logged a when frostseeded into wheat, but is not as pro- fertilizer replacement value of 36 lb. N/A in a two- ductive as medium red (229). year Michigan trial that used N isotopes to track nitrogen fixation. Red clover and three other MANAGEMENT legumes were no-till drilled into wheat stubble in August, then chemically killed by mid-May just Establishment & Fieldwork ahead of no-till corn. Clover even in this short In spring in cool climates, red clover germinates niche shows good potential to suppress weeds in about seven days—quicker than many and reduce N fertilizer application (140). legumes—but seedlings develop slowly, similar to • Soybeans at leaf-yellowing. Sowing the winter annual legumes. Traditionally it is drilled at clover seed with annual or perennial ryegrass as a 10 to 12 lb./A with spring-sown grains, using nurse crop keeps the soil from drying out until auxiliary or “grass seed” drill boxes. Wisconsin the clover becomes established (197). researchers who have worked for sev eral years to optimize returns from red clover/oats interseed- Whenever possible, lightly incorporate clover ings say planting oats at 3 to 4 bu./A gives good seed with a harrow. Wait at least six weeks (check stands of clover without sacrificing grain yield labels!) to establish a red clover stand in soil treat- (398). ed with pre-emergent herbicides such as atrazine.

RED CLOVER 161 perature should be above 60° F (so that the plants are actively grow ing). When soil temperature drops below 50° F, biological decomposition slows to the point that mineralization of N from the clover roots and top-growth nearly stops (229).

Field Evaluation In Michigan, about half of the total N fixed by a legume will mineralize during the fol lowing growing season and be available to that season’s crop (229). However, Wisconsin research shows release may be faster. There, red clover and hairy vetch released 70 to 75 percent of their N in the first season (401).

Marianne Sarrantonio Marianne Rotations Rotation niches for red clover are usually between RED CLOVER (Trifolium pratense) two non-leguminous crops. Spring seeding with oats or frostseeding into wheat or barley are com mon Killing options (34). The intersowing allows economic use For peak N contribution, kill red clover at about of the land while the clover is developing. This mid-bloom in spring of its second season. If you grain/red clover combination often follows corn, but can’t wait that long, kill it earlier to plant field also can follow rice, sugar beets, tobac co or potatoes corn or early vegetables. If you want to har vest in two-year rotations. For three-year rotations includ- the first cutting for hay, compost or mulch, kill the ing two full years of red clover, the clover can be regrowth in late summer as green manure for fall incorporated or surface-applied (clipped and left on vegetables (197). If avoiding escapes or clover the field) for green manure, cut for mulch or har- regrowth is most important, terminate as soon as vested for hay (120). soil conditions allow. Red clover in a corn>soybean>wheat/red Actively growing red clover can be difficult to clover rotation in a reduced-input system out-per - kill mechanically, but light fall chisel plowing fol- formed continuous corn in a four-year Wisconsin lowed by a second such treatment has worked study. The legume cover crop system used no well in sandy loam Michigan soils. commercial fertilizer, no insecti cides and herbi- To kill clover mechanically in spring, you can cides on only two occasions—once to-spot spray till, chop or mow it any time after blooming starts. Canada thistles and once as a rescue treatment for You can also shallow plow, or use a moldboard soybeans. Rotary hoeing and cultivating provided plow. Chop (using a rolling stalk chopper), flail or weed control. sicklebar mow about seven to 10 days ahead of Gross margins were $169 for the corn>soy - no-till planting, or use herbicides. Roundup beans>wheat/red clover and $126 for continuous Ready® soybeans can be drilled into living red corn using standard agricultural fertilizers, insecti - clover and sprayed later. cides and herbicides. Top profit in the study went A summer mowing can make it easier to kill red to a corn>soybean rotation with a gross margin of clover with herbicides in fall. Michigan recom - $186, using standard inputs (272, 398, 167). mendations call for mowing (from mid-August in Ohio farmer Rich Bennett frostseeds redclover northern Michigan to early September in south - (10-12 lb./A) into wheat in February. He gets a ern Michigan), then allowing regrowth for four decent stand of clover that keeps weeds down in weeks before spraying. The daytime high air tem- summer after wheat harvest. The clover overwin-

162 MANAGING COVER CROPS PROFITABLY ters and continues to grow in spring. He waits as If an emergency for- Few legumes are long as possible, and then kills the clover with a age cut is needed, har- disc and roll (two passes) in late April and plants vest red clover in early as widely adapted corn. He doesn’t add any fertilizer N and the corn summer, then broad- as red clover, averages 165 bu/A on his Ottokee fine sandy soil. cast and lightly incor- If summer annual grasses are a problem, red porate millet seed with which can be used clover is not your best option because it allows a tine harrow or disk. as green manure, the grasses to set seed, even under a mowing Millet is a heat-loving regime. grass used as a cover forage or seed and for age in warm-soil Pest Management areas of Zone 6 and crop. If poor establishment or winterkill leads to weed warmer. growth that can’t be suppressed with clipping or grazing, evaluate whether the anticipated cover COMPARATIVE NOTES crop benefits warrant weed control. Take care to completely kill the cover crop when planting dry Medium red clover has similar upper-limit pH tol - beans or soybeans after clover. Unless you are erance as other clovers at about 7.2. It is general - using herbicide-tolerant crops, you have limited ly listed as tolerating a minimum pH of 6.0—not herbicide options to control clover escapes that quite as low as mammoth, white or alsike survive in the bean crop (229). (Trifolium hybridum) clovers at 5.5—but it is Root rots and foliar diseases typically kill com - said to do well in Florida at the lower pH. Red mon medium red clover in its second year, making clover and sweetclover both perform best on it function more like a biennial than a perennial. well-drained soils, but will tolerate poorly drained Disease-resistant cultivars that persist three to soils. Alsike thrives in wet soils. four years cost 20 to 40 cents more per pound Red clover has less tendency to leach phos - and are unnecessary for most green manure appli - phorus (P) in fall than some non-legume covers. It cations. When fertilizer N cost is high, however, released only one-third to one-fifth the P of annu - remember that second-year production for some al ryegrass and oilseed radish, which is a winter- improved varieties is up to 50 percent greater annual brassica cover crop that scavenges large than for common varieties. amounts of N. Figuring the radish release rates— Bud blight can be transmitted to soybeans by even balanced somewhat by the erosion suppres - volunteer clover plants. sion of the covers—researchers determined that P runoff potential from a quick-leaching cover Other Management Options crop can be as great as for unincorporated Mow or allow grazing of red clover four to six manure (274). weeks before frost in its establishment year to For early fall plowdown, alsike clover may be a prepare it for overwintering. Remove clippings cheaper N source than mammoth, assuming simi- for green manure or forage to prevent plant dis - lar N yields. ease. Red clover reaches its prime feeding value at Red clover and alfalfa showed multi-year bene- five to 15 days after first bloom. fits to succeeding corn crops, justifying a cred it of Under ideal conditions, medium red clover can 90 lb. N/A the first year for red clover (197) and be cut four times, mammoth only once. Maximum 50 lb. N/A the second year. The third legume in cutting of medium one year will come at the the trial, birdsfoot trefoil (Lotus corniculatus), expense of second-year yield and stand longevity. was the only one of the three that had enough Red clover and red clover/grass mixtures make third-year N contribu tion to warrant a credit of 25 good silage if wilted slightly before ensiling or if lb. N/A (148). other preservative techniques are used (120).

RED CLOVER 163 Cultivars. KENLAND, KENSTAR, ARLINGTON, and (90). CHEROKEE has performed well in Iowa (384), MARATHON are improved varieties of medium red is suited to the Coastal Plain and lower South, and clover with specific resistance to anthracnose and has superior resistance to rootknot nematode. mosaic virus strains. They can persist three or even four years with ideal winter snow cover Seed sources. See Seed Suppliers (p. 195).

SUBTERRANEAN CLOVERS Trifolium subterraneum, T. yanninicum, T. brachycalcycinum

Also called: Subclover

Type: reseeding cool season annual legume

Roles: weed and erosion suppres - sor, N source, living or dying mulch, continuous orchard floor cover, forage

Mix with: other clovers and subclovers

See charts, p. 66 to 72, for ranking and management summary.

ubterranean clovers offer a range of low- (Hardiness Zone 7 and warmer) as a killed or liv- growing, self-reseeding legumes with high ing mulch for summer or fall crops. SN contribution, excellent weed suppres- Most cultivars require at least 12 inches of sion and strong persistence in orchards and pas- growing-season rainfall per year. A summer dry tures. Fall-planted subclovers thrive in period limits vegetative growth, but increases Mediterranean conditions of mild, moist winters hard seed tendency that leads to self-reseeding for and dry sum mers on soils of low to moderate fer- fall reestablishment (131). tility, and from moderately acidic to slightly Subclovers generally grow close to the ground, alkaline pH. piling up their biomass in a compact layer. A Subclover mixtures are used on thousands of Mississippi test showed that subclover stolons were acres of California almond orchards. It holds about 6, 10 and 17 inches long when the canopy promise in the coastal mid-Atlantic and Southeast was 5, 7 and 9 inches tall, respectively (105).

164 MANAGING COVER CROPS PROFITABLY Diversity of Types, Cultivars Subclover mixtures help West Coast orchardists Select among the many subclover culti vars that fit achieve season-long weed management. In your climate and your cover crop goals. Identify Coastal California, fast-growing TRIKKALA, a midsea- your need for biomass (for mulch or green son cul tivar with a moderate moisture require- manure), time of natural dying to fit your spring- ment, jumps out first to suppress weeds and planting schedule and prominence of seed set for produces about twice as much winter growth dur- a persistent stand. ing January and February as the other subclovers. It Subclovers comprise three Trifolium species: dies back naturally as KOALA, (tall) and KARRIDALE • T. subterraneum. The most common cultivars (short) come on strong in March and April. The that thrive in acid to neutral soils (pH=5.5-7.5) three cultivars complement each other spatially and a Mediterranean climate and temporally for high solar efficiency, similar to • T. yanninicum. Cultivars best adapted to the interplanting of peas, purple vetch, bell beans water-logged soils and oats in California vegetable fields where a high- • T. brachycalcycinum. Cultivars adapted to residue, high-N cover is desired. alkaline soils and milder winters In legume test plots along the Maryland shore, Subclovers Primary differences between these species are subclover mulch controlled their moisture requirements, seed production and weeds better than con - thrive in days to maturity (21). Other variables include: ventional herbicide treat- Mediterranean • Overall dry matter yield ments. The only weed to • Dry matter yield at low moisture or low fertility penetrate the subclover climates of • Season of best growth (fall, winter or spring) was a fall infes tation of yel- mild, moist • Hard-seeding tendency low nutsedge. The cover • Grazing tolerance crop regrew in fall from winters and hard seed in the second and Subclover cultivars often are described by their third years of the experi- dry summers. days to maturity. Seed production is dependent ment (31). on maturity and weather. The wetter it is during seed set, the lower the percentage of hard seed – Green manure. In east Texas trials, subclover important for reseeding systems (131). delivered 100 to 200 lb. N/A after spring plow- • Short season subclovers tend to set seed down. Grain sorghum planted into incorporated quickly. They need only 8 to 10 inches of grow- subclover or berseem clover with no additional N ing-season rainfall and set seed about 85 days after yielded about the same as sorghum planted into planting. Early subclovers tend to be less winter disked and fertilized soil without a cover crop in hardy (103). three out of four years. The fertilized fields had • Intermediate types thrive with 14 to 20 inch- received 54 lb. N/A (243). es of rain and set mature seed in about 100 days. • Long-season cultivars perform best with Versatile mulch. Subclover provides two oppor- 18 to 26 inches of rainfall, setting seed in about tunities for use as a mulch in vegetable sys tems. In 130 days. spring, you can no-till early planted crops after subclover has been mechanically or chemi cally BENEFITS killed, or plant later, after subclover has set seed and dried down naturally (31). In fall, you can Weed suppressor. Subclover can produce 3,000 manage new growth from self reseeding to pro- to 8,500 lb. dry matter/A in a thick mat of stems, vide a green living mulch for cold-weather crops petioles (structures connecting leaves to stems) such as broccoli and cauliflower. and leaves. Denser and less viny than hairy vetch, Conventionally tilled corn without a cover crop it also persists longer as a weed-controlling mulch. in a New Jersey test leached up to 150 lb. N/A

SUBTERRANEAN CLOVERS 165 profit compared with monocropped control plots. Eliminating pesticide costs offset the reduced weight of the cabbages in the undersown plots. Primary pests were Mamestra brassicae, Brevicoryne brassicae and Delia brassicae. Undersowing leeks with subclover in the Netherlands greatly reduced thrips that cannot be controlled by labeled insecticides, and slightly reduced leek rust, a disease that is difficult to con trol. While leek quality improved, the quantity of leeks produced was reduced considerably (415).

Elayne Sears Elayne When tarnished plant bug (Lygus lineolaris) is SUBTERRANEAN CLOVER (Trifolium subterraneum) a potential pest, subclover may be the legume cover crop of choice, based on a Georgia com - over winter while living subclover prevented N parison among subclovers, hybrid vetches and loss (128). Mowing was effective in controlling a crimson clover. MT. BARKER had particularly low living mulch of subclover in a two-year California levels, and nine other subclover cultivars had trial with late-spring, direct-seeded sweet corn lower levels than the crimson (56). and lettuce. This held true where subclover stands were dense and weed pressure was low. Planting Home for beneficial insects. In tests of eight into the subclover mulch was difficult, but was cover crops or mixtures intercropped with canta - done without no-till equipment (239). lope in Georgia, MT. BARKER subclover had the highest population of big-eyed bugs (Geocorus Soil loosener. In an Australian study in com - punctipes), a pest predator. Subclover had signifi - paction-prone sandy loam soil, lettuce yield dou - cantly higher numbers of egg masses of the preda - bled following a crop of subclover. Without the tor than rye, crimson clover and a polyculture of clover, lettuce yields were reduced 60 percent on six other cover crops, but not significantly higher the compacted soil. Soil improvement was credited than for VANTAGE vetch or weedy fallow. While the to macropores left by decomposing clover roots covers made a significant difference in the preda- and earthworms feeding on dead mulch (395). tor level, they did not make a significant difference in control of the target pest, fall army worm Great grazing. Subclovers are highly palatable (Spodoptera frugiperda) (56). and relished by all livestock (120). Seeded with perennial ryegrass, tall fescue or orchardgrass, sub - Erosion fighter. Subclover’s soil-hugging, dense, clovers add feed value as they improve produc - matted canopy is excellent for holding soil. tivity of the grasses by fixing nitrogen. In California, subclover is used in pasture mixtures Disease-free. No major diseases restrict sub- on non-irrigated hills. Perennial ryegrass is pre - clover acreage in the U.S. (21). ferred for pasture through early summer, especial - ly for sheep (309). MANAGEMENT

Insect pest protection. In the Netherlands, Establishment subclover and white clover in cabbage sup- Subclovers grow best when they are planted in pressed pest insect egg laying and larval popula- late summer or early autumn and grow until early tions enough to improve cabbage quality and winter. They go dormant over winter and resume

166 MANAGING COVER CROPS PROFITABLY growth in early spring. In late spring, plants Southeast (103). This is about double the usual flower and seeds mature in a bur at or below the recommended rate for pastures in the warmer soil surface (hence the name subter ranean clover) soils of the Southeast. as the plant dries up and dies. A dense mulch of Small plants of ground-hugging subclover dead clover leaves and long peti oles covers the ben efit more from heat radiating from the soil seeds, which germinate in late summer to estab- than larger plants, but are more vulnerable during lish the next winter’s stand (127). Their persis- times of freezing and thawing. Where frost tence over many seasons justifies the investment heav ing is expected, earlier planting and well- in seed and careful establishment. estab lished plants usually survive better than In California, sow in September or early smaller ones (103). October to get plants well established before cool weather (309). Planting continues through Killing November in the most protected areas. Subclover dies naturally in early summer after In marginally mild areas, establish with grasses blooming and seed set. It is relatively difficult to for winter protection. Subclover stimulates the kill without deep tillage before mid-bloom stage. grasses by improving soil fertility. You can over- After stems get long and seed sets, you can kill seed pasture or range land without tillage, but you plants with a grain drill or a knife roller (95). can improve germination by having livestock In northern Mississippi, subclover was the least trample in the seed. Subclover often is aerially controlled of four legumes in a mechanical kill applied to burned or cleared land. Initial growth test. The cover crops were will be a little slower than that of crimson, but a rolled with coulters spaced 4 Subclover little faster than white clover (120). inches apart when the plants Broadcast at 20-30 lb./A in a firm, weed-free had at least 10 inches of mixes help seedbed. Cover seed with a light, trailing harrow prostrate growth. While keep weeds or with other light surface tillage to a depth of less hairy vetch and crimson than one-half inch. Add lime if soil is highly acid— clover were 80 to 100 per- in check all below pH 5.5 (309). Soils low in pH may require cent controlled, berseem season long supplemental molybdenum for proper growth, control was 53 percent and and phosphorus and sulfur may also be limiting subclover was controlled in West Coast nutrients. Only the T. yanninicum culti vars will only 26 to 61 percent (105). tolerate standing water or seepage areas (21, 309). Researchers in Ohio had orchards. Subclover often is planted with rose clover and no trouble killing post-bloom crimson clover in California orchard mixes. subclover with a custom-built Crimson and subclover usually dominate, but undercutter. The specialized tool is made to slice hard-seeded rose clover per sists when dry weath- 1 to 2 inches below the surface of raised beds. The er knocks out the other two (447). undercutter consisted of two blades that are In the East, central Mississippi plantings are rec- mounted on upright standards on either side of the ommended Sept. 1 to Oct. 15, although earlier bed and slant backward at 45 degrees toward the plantings produce the earliest foliage in spring center of the bed. A mounted rolling harrow was (120). In coastal Maryland where MT. BARKER attached to lay the cover crop flat on the surface plants were tallest and most lush, winterkill after being cut (96). The tool severs stalks from (caused when the temperature dropped to 15° F roots while above-ground residue is undamaged, or below) has been most severe. Planting in this greatly slowing residue decomposition (95). area of Zone 7 should be delayed until the first Subclover tolerance to her bicides varies with two weeks of October. Plant at about 22 lb./A for cultivar and growth stage. Generally, subclover is cover crop use in the mid-Atlantic (31) and easier to kill after it has set some seed (104, 165).

SUBTERRANEAN CLOVERS 167 Reseeding Management suppres sed lettuce, broccoli and tomato seedlings The “over-summering” fate of reseeding subclover for eight weeks, but not as severely or as long as plantings is as critical to their success as is the did com pounds from ryegrass (Lolium rigidum over-wintering of winter-annual legumes. The cv. WIMMERA) mulch. An alfalfa mulch showed no thick mat of vegetation formed by dead residue such allelopathic effect in an Australian study can keep subclover seeds dormant if it is not dis - (395). turbed by grazing, tillage, burning or seed harvest. Guard against moisture competition from sub- Where cover crop subclover is to be grazed clover at planting. Without irrigation to ensure before another year’s growth is turned under, crop seeds will have enough soil mois ture to ger- intensive grazing management works best to minate in a dry year, be sure that the subclover is reduce residue but to avoid excess seed bur con - killed seven to 14 days prior to planting to allow sumption (309). Grazing or mowing in late spring rainfall to replenish soil moisture naturally (31). or early summer helps control weeds that grow through the mulch (292). Soil-borne crop seedling disease. In north You can improve volunteer regrowth of sub- Mississippi tests, residue and leachate from clover in warm-season grass mixes by limiting N legume cover crops (including subclover) caused fertilization during summer, and by grazing the greater harm to grain sorghum seedlings, com - grass shorter until cold temperatures limit grass pared to nonlegumes. Rhizoctonia solani, a soil - growth. This helps even though subclover borne fungus, infected more than half the seedlings may emerge earlier (21). Subclover flow- sorghum seedlings for more than a month, but dis- ers are incon spicuous and will go unnoticed with- appeared seven to 13 days after legume residues out careful, eye-to-the-ground inspection (103). were removed (101). After plants mature, livestock will eagerly eat seed heads (120). In dry years when you want to N-leaching. The early and profuse nodulation of maintain the stand, limit grazing over summer to subclovers that helps grass pastures also has a avoid over-consumption of seed heads and deple - downside—excess N in the form of nitrate can tion of the seed bank. Close mowing or grazing contaminate water supplies. Topgrowth of sub- can be done any time. clover, black medic and white clover leached 12 to 26 lb. N/A over winter, a rate far higher than Management Challenges red clover and berseem clover, which leached Possible crop seedling suppression. The only 2 to 4 lb. N/A in a Swedish test (227). allelopathic compounds that help subclover sup - press weeds also can hurt germination of some Pest Management crops. To avoid problems with these crops, delay Subclovers showed little resistance to root-knot planting or remove subclover residue. No-till nematodes in Florida tests on 134 subclover lines planters equipped with tine-wheel row cleaners in three years of testing the most promising vari- can reduce the recommended 21-day waiting eties (233). period that allows allelopathic compounds to Lygus species, important pests of field, row and drop to levels that won’t harm crops (101). Kill orchard crops in California and parts of the subclover at least a year before planting peach Southeast, were notably scarce on subclover trees to avoid a negative effect on seedling vigor. plants in a south Georgia comparison. Other It’s best to wait until August of the trees’ second legumes harboring more of the pests were, in summer to plant subclover in row middles, an descending order, CAHABA and VANTAGE vetch, Arkansas study found (61). hairy vetch, turnip and monoculture crimson The degree to which a cover crop mulch hin- clover (56). ders vegetable seedlings is crop specific. Plant- Most cultivars imported to the U.S. are low in toxic compounds from subclover mulch estrogen, which is present in sufficient levels in

168 MANAGING COVER CROPS PROFITABLY some Australian cultivars to reduce fertility in ewes, Rice N-source. In Louisiana trials, subclover but not in goats or cattle. Confirm estro gen status regrew well in fall when allowed to set seed of a cultivar if you plan to graze sheep on it (309). before spring flooding of rice fields. Compared with planting new seed, this method yields larger Crop Systems seedling populations, and growth usually begins Interseeded with wheat. NANGEELA subclover earlier in the fall. The flood period seems to provided 59 lb. N/A when it was grown as an enhance dormancy of both subclover and crim - interseeded legume in soft red winter wheat in son clover, and germination is robust when the eastern Texas. That extra N helped boost the fields are drained (103). Formerly, some Louisiana wheat yield 283 percent from the previous year’s rice farmers seeded the crop into dry soil then let yield when four subclover cultivars were first it develop for 30 days before flooding. Early vari - established and actually decreased yield, com - eties such as DALKIETH and NORTHAM may make pared with a control plot. NANGEELA, MT. BARKER, seed prior to the recommended rice planting WOOLGENELLUP and NUNGARIN cultivars boosted date. In recent decades, “water planting” has been wheat yield by 24, 18, 18, and 11 bu./A, respec - used to control red rice, a weedy relative of tively, in the second year of the study. Over all domestic rice. Water seeding into cover crop three years, the four cultivars added 59, 51, 38 and residues has not been successful (36). 24 lb. N/A, respectively (44). Plant breeder Gerald Ray Smith of Texas A&M Fertility, weed control for corn. In the humid University worked with several subclovers in east - mid-Atlantic region, grain and silage corn no-tilled ern Texas. While the subclovers grew well the first into NANGEELA subclover did well in a six-year year, he concluded that those cultivars need a pro- New Jersey trial. With no additional N, the sub- longed dry period at maturity to live up to their clover plots eventually out-yielded comparison reseeding performance in Australia and California. plots of rye mulch and bare-soil that were con - Surface moisture at seed set reduces seed harden- ventionally tilled or minimum-tilled with fertilizer ing and increases seed decay. Mid summer rains at up to 250 lb. N/A. The subclover contributed cause premature germination that robs the sub- up to 370 lb. N/A (128), an N supply requiring clover seed bank, especially in pas tures where careful management after the subclover dies to grasses tend to create moist soil. Most summer- prevent leaching. germinating plants die when dry weather returns. Control of fall panicum was poor in the first In Mississippi, subclover hard seed develop - year, but much better the next two years. Control ment has been quite variable from year to year. In of the field’s other significant weed, ivyleaf morn - dry years, close to 100 percent hard seed is devel - ing glory, was excellent in all years. Even though oped. Dormancy of the seed breaks down more no herbicide was used in the subclover plots, rapidly on bare soil with wider temperature weed biomass was lowest there (128). swings than it does on mulched soils (133, 134). Central New Jersey had mild winters during To facilitate reseeding or to seed into pastures, the these experiments. Early spring thaws trig gered grasses must be mowed back or grazed quite subclover regrowth followed by plunging short for the subclover to establish (103). tem peratures that dropped below 15° F. This weak ened the plants and thinned the stands. Mix for persistence. California almond growers The surviving plants, which formed dense stands need a firm, flat orchard floor from which to pick at times, were mowed or strip-killed using herbi - up almonds. Many growers use a mix of moisture- cides or tillage. Mowing often induced strong tolerant TRIKKALA, alkaline-tolerant KOALA, and regrowth, so strips at least 12 inches wide proved KARRIDALE, which likes neutral to acid soils. These to be the best to prevent moisture competition blended subclovers give an even cover across between the subclover and the cabbage and moist swails and alkaline pockets. zucchini transplants.

SUBTERRANEAN CLOVERS 169 Sustainable sweet corn. On Maryland’s Eastern growth, especially when fall rains began, but failed Shore (one USDA hardiness zone warmer than to set any seed (383). Stress from drought and New Jersey), University of Maryland weed spe- heat also can trigger seed set. cialist Ed Beste reported good reseeding in four consecutive years and no problems with stand COMPARATIVE NOTES loss from premature spring regrowth. Overwintering MT. BARKER plants sent out stolons White and arrowleaf clovers have proved to be across the soil surface to quickly re-establish a better self-reseeding clovers than subclover in the good stand ahead of sweet corn plantings (31). humid South because their seed is held in the air, Beste believes the sandy loam soil with a sand giving them a better chance to harden. Top underlayer at his site is better for subclover than reseeding contenders are balansa clover (see Up- the heavier clay soils at the USDA Beltsville station and-Coming Cover Crops, p. 191) and south ern some 80 miles north, where hairy vetch usually spotted burr medic (see Southern Spotted Burr out-performs subclover as a killed organic mulch Medic Offers Reseeding Persistence, p. 154). in transplanted vegetable systems. Winterkill While mid-season subclovers generally pro - reduced the subclover stand on top of bedded duced more dry matter and N than medics for rows one year of the comparison, yet surviving dryland cereal-legume rotations in Montana plants between the beds produced nearly as much (381), they did not set seed when grown as sum - biomass per square foot as did hairy vetch (2). mer annuals in the region. Summer growth con - Beste has worked with subclover at his tinued as long as moisture held up in trials there. Salisbury, Md., site for several years, seeding veg - Vegetative growth increased until frost, as cool, etables in spring, early summer and mid-summer moist fall weather mimicks the Mediterranean into the killed or naturally dead cover crop winter conditions where subclover thrives (383). mulch. For three years, subclover at Beste’s sweet CLARE is a cultivar of the subclover subspecies corn system comparison site yielded about 5,400 brachycalycinum. Compared with the more com - lb. DM/A. Without added N, the subclover plots mon subspecies subterranean (SEATON PARK and yielded as much sweet corn as conventional plots DALIAK), CLARE has vigorous seedlings, robust receiving 160 lb. N/A. Weed suppression also was growth when mowed monthly and is said to tol - better than in the conventional plots. He sprayed erate neutral to alkaline soils. However, it appears glyphosate on yellow nutsedge in fall to prevent to be less persistent than other types (61). tuber formation by the grassy weed, the only Subclover, rye and crimson clover provided grass weed that penetrated the subclover mulch (31). weed control that was 46 to 61 percent better than Beste sprays paraquat twice to control sub- a no-cover/no-till system at two North Carolina clover ahead of no-till, direct seeded zucchini in locations. Subclover topped the other covers in the first week of June. His MT. BARKER will set seed suppressing weeds in plots where no herbicides and die back naturally at the end of June—still in were used. None of the cover crop treatments elim- time to seed pumpkins, fall cucumbers, snap inated the need for pre-emergent herbicides for beans or fall zucchini planted without herbicides economic levels of weed control (454). (31). Such a no-chemical/dying mulch/perpetually Subclover creates a tighter mat of topgrowth reseeding legume system is the goal of cultivar than vetch (31) or crimson clover (103). and system trials in California. Seed production in subclovers normally is trig - Cultivars. See Comparative Notes, above, and gered by increasing day length in spring after the Diversity of Types, Cultivars (p. 165). plant experiences decreasing fall day length. This explains why spring-planted subclover in Seed sources. See Seed Suppliers (p. 195). Montana tests produced profuse vegetative

170 MANAGING COVER CROPS PROFITABLY SWEETCLOVERS Yellow sweetclover (Melilotus officinalis) and white sweetclover (M. alba)

Also called: HUBAM (actually a culti var of annual white sweetclover)

Type: biennial, summer annual or winter annual legume

Roles: soil builder, fertility source, subsoil aerator, weed suppressor, erosion preventer

Mix with: small grains, red clover See charts, pp. 66 to 72, for ranking and management summary.

ithin a single season on even marginal - and grazing legumes in the South and later ly fertile soils, this tall-growing biennial throughout the Midwest in the first half of this Wproduces abundant biomass and mod - century. Sweetclover is used as a cover crop most erate amounts of nitrogen as it thrusts a taproot commonly now in the Plains region, with little use and branches deep into subsoil layers. Given fer - in California. tile soils and a second season, it lives up to its full potential for nitrogen and organic matter produc - Types tion. Early in the second year it provides new top Biennial yellow sweetclover can produce up to 24 growth to protect the soil surface as its roots inches of vegetative growth and 2.5 tons dry mat - anchor the soil profile. It is the most drought-tol - ter/A in its establishment year. During the second erant of forage legumes, is quite winter-hardy and year, plants may reach 8 feet tall. Root mass and can extract from the soil then release phospho - penetration (to 5 feet) are greatest at the end of rus, potassium and other micronutrients that are dormancy in early spring, then gradually dissipate otherwise unavailable to crops. through the season (443). Sweetclover thrives in temperate regions wher - A distinguishing sweetclover feature is bracts of ever summers are mild. Annual sweetclovers tiny blooms through much of its second year. (HUBAM is the most well known) work best in the White biennial sweetclovers are taller, more Deep South, from Texas to Georgia. There, they coarsely stemmed, less drought tolerant, and pro - establish more quickly than the biennial types and duce less biomass in both the seeding and second produce more biomass in the seeding year in years. White types bloom 10 to 14 days later than southern regions. yellow, but bloom for a longer season. They In this chapter, “sweetclover” refers to biennial reportedly establish more readily in New York types unless otherwise noted. (450). Tall, stemmy cultivars are better for soil Sweetclover was the king of green manures improvement (120, 361, 422).

SWEETCLOVERS 171 wheat, could tap the deep P buildup from the legume roots and fallow leaching, whereas spring wheat could not. The vesicular-arbuscular mycor - rhizal (VAM) fungi associated with legume roots contribute to the increased P availability associat - ed with sweetclover (69, 70).

N source. A traditional green manure crop in the upper Midwest before nitrogen fertilizer became widely available, sweetclover usually produces about 100 lb. N/A, but can produce up to 200 lb. N/A with good fertility and rainfall. In Ohio, it contained about 125 lb. N/A by May 15, increasing to

Marianne Sarrantonio Marianne 155 lb. by June 22. Illinois researchers reported more than 290 lb. N/A. YELLOW SWEETCLOVER (Melilotus officinalis) Abundant biomass. If planted in spring and Both yellow and white sweetclover have culti - then given two full seasons, biennial sweetclovers vars bred for low levels of coumarin. This com - can produce 7,500 to 9,000 lb. dry matter/A pound exists in bound form in the plant and (3,000 to 3,500 lb./A in the seeding year, and poses no problem during grazing. However, 4,500 to 5,500 lb./A the second). Second-year coumarin can cause internal injury to cattle when yields may go as high as 8,500 lb./A. they eat spoiled sweetclover hay or silage. Hot-weather producer. Sweetclover has the Annual sweetclover (Melilotus alba var. greatest warm-weather biomass production of annua) is not frost tolerant, but can produce up any legume, exceeding even alfalfa. to 9,000 lb. dry matter/A over a summer after being oversown into a grain crop or direct seed- Soil structure builder. Kansas farmer Bill ed with a spring grain nurse crop. The best-known Granzow says sweetclover gives his soils higher annual sweetclover cultivar is HUBAM, a name organic matter, looser structure and better tilth. often used for all annual white sweetclover. While See Sweetclover: Good Grazing, Great Green its taproot is shorter and more slender than that Manure (p. 174). HUBAM annual sweetclover also of its biennial cousins, it still loosens subsoil com- improved soil quality and increased yield poten- paction. tial in 1996 New York trials (451). Compaction fighter. Yellow sweetclover has BENEFITS a determinate taproot root up to 1 foot long with extensive branches that may penetrate 5 feet to Nutrient scavenger. Sweetclover appears to aerate subsoils and lessen the negative effects of have a greater ability to extract potassium, phos - compaction on crops. White types have a strong phorus and other soil nutrients from insoluble tap root that is not determinate. minerals than most other cover crops. Root branches take in minerals from seldom-disturbed Drought survivor. Once established, sweet- soil horizons, nutrients that become available as clover is the most drought tolerant of all cover the tops and roots decompose (361). crops that produce as much biomass. It is espe - Research in Saskatchewan during a 34-year cially resilient in its second year, when it could do period showed that phosphorus (P) availability well in a dry spring during which it would be dif- increased in subsoil layers relative to surface lay - ficult to establish annual cover crops. The yel low ers, peaking at an 8-foot depth. Winter wheat and type is less sensitive to drought and easier to safflower, with deeper root systems than spring establish in dry soils than the white type.

172 MANAGING COVER CROPS PROFITABLY Attracts beneficial insects. Blossoms attract Sweetclover produces 50 percent or more hard honeybees, tachinid flies and large predatory seed that can lie in soil for 20 years without ger - wasps, but not small wasps. minating. Commercial seed is scarified to break this non-porous seedcoat and allow moisture to Widely acclimated. Self-reseeding sweetclover trigger germination. If you use unscarified seed, can be seen growing on nearly barren slopes, road check hardseed count on the tag and do not rights-of-way, mining spoils and soils that have count on more than 25 percent germination from low fertility, moderate salinity or a pH above 6.0 the hardseed portion. (183). It also can tolerate a wide range of envi - The need for scarifica- Winter-hardy and ronments from sea level to 4,000 feet in altitude, tion to produce an drought tolerant, including heavy soil, heat, insects, plant diseases adequate stand may (120) and as little as 6 inches of rain per year. be over-rated, howev- this biennial can er. The process had no produce up to 200 Livestock grazing or hay. If you need emer - effect on germina tion gency forage, sweetclover has a first-year feed in six years of field lb. N/A with good value similar to alfalfa, with greater volume of less - testing in North er quality in the second year. Dakota—even when fertility and rainfall. planting 70 percent MANAGEMENT hard seed still in seed pods. 1 1 Establishment & Field Management Seed at a depth of /4 to /2 inch in medium to 1 Sweetclover does well in the same soils as alfalfa. heavy textured soils, and /2 to 1.0 inch on sandy Loam soils with near-neutral pH are best. Like soils. Seeding too deeply is a common cause of alfalfa, it will not thrive on poorly drained soils. poor establishment. For high yields, sweetclover needs P and K in the Seed annual white sweetclover at 15 to 30 medium to high range. Deficient sulfur may limit pounds per acre. Expect 70 to 90 lb. N/A from its growth (153). Use an alfal fa/sweetclover 4,000 to 5,000 lb. dry matter/A on well-drained, inoculant. clay loam soils with neutral to alkaline pH. In temperate areas of the Corn Belt, drill yellow A press-wheel drill with a grass seed attach - sweetclover in pure stands at 8 to 15 lb./A or ment and a seed agitator is suitable for planting broadcast 15 to 20 lb./A, using the higher rate in sweetclover into a firm seed bed. If the seedbed is dry or loose soils or if not incorporating. too loose to allow the drill to reg ulate seeding In drier areas such as eastern North Dakota, trials depth, run the seed spouts from the grass and of seeding rates from 2 to 20 lb./A showed that just legume boxes to drop seed behind the double- 4 lb./A, broadcast or drilled, created an adequate disk opener and in front of the press wheels. sole-crop stand for maximum yield. Recommended Light, shallow harrowing can safely firm the rates in North Dakota are 4 to 6 lb./A drilled with seedbed and incorporate seed (183). small grains at small-grain plant ing, 5 to 8 lb./A In the Canadian Northern Plains, dribble the broadcast and harrowed (some times in overseed- seed through drill box hoses directly in front of ing sunflowers), and 6 to 10 lb./A. broadcast with- the presswheels for quick and easy establishment out incorporating tillage (183). (32). An excessively dense stand will create spindly If your press-wheel drill has no legume box or stalks that don’t branch or root to the degree that grass-seed attachment, you can mix the legume plants do in normal seedings. Further, the plants and small grain seed, but mix seed often due to will tend to lodge and lay over, increasing the risk settling. Reduce competition between the crops of diseases. So for maximum effect of subsoil pen- by seeding a part of the com panion crop first, etration or snow trapping, go with a lighter seed- then seed a mix of the clover seed and the baling rate. ance of the grain seed at right angles (183).

SWEETCLOVERS 173 Sweetclover: Good Grazing, Great Green Manure

Bill Granzow taps biennial yellow sweetclover keep cattle healthy on the lush legume to enhance soil tilth, control erosion and forage. prevent subsoil from becoming compacted. He • Quick green manure. Spray after it has uses common varieties, either from the grown 3 to 4 inches, then plant sorghum. elevator or one his father originally bought This method contributes about 60 pounds from a neighbor. of N to the soil. He knocks back persistent Granzow, of Herington, Kan., produces no- re-growing sweetclover crowns in the till grain and runs cattle in an area midway sorghum by adding 2, 4-D or Banvel to the between Wichita and Manhattan in the east- postemerge herbicide mix. central part of the state. Granzow overseeds • Green manure/fallow. Kill at mid- to full sweetclover into winter wheat in December bloom, leave fallow over summer, then plant or January at 12 to 15 lb./A using a rotary wheat again in fall. This method provides broadcaster mounted on his pickup. about 120 lb. N/A, according to estimates Sometimes he asks the local grain cooperative from Kansas State University. to mix the seed with his urea fertilizer for the • Seed crop. He windrows the plants when wheat. There’s no extra charge for seed about 50 percent of the seedpods have application. Alternately, Granzow plants turned black, then runs the stalks through sweetclover at the same rate with March- his combine. To remove all of the hulls, he seeded oats. runs the seed through the combine a Yellow sweetclover has overgrown second or third time. Granzow’s wheat only when the wheat stand is thin and abnormally heavy rains delay Despite the heavy growth in the second year, harvest. The minimal problem is even rarer in yellow sweetclover matures and dies back oats, he says. naturally. If the residue is heavy, he sets the He uses yellow sweetclover with the drill a bit deeper for planting. companion wheat crop in four possible ways, He rates fall sweetclover hay from the depending on what the field needs or what seeding year as “acceptable forage.” He’s aware other value he wants to maximize. For each, that moldy sweetclover hay contains he lets the clover grow untouched after wheat coumarin, a compound that can kill cattle, but harvest for the duration of the seeding year. He he’s never encountered the problem. Second- used to disk the sweetclover at least twice to year yellow sweetclover makes silage at initial kill it. Now 100% no-till, he sprays with to mid-bloom stage with 16 percent protein Roundup and “a little bit of 2,4-D.” Second-year on a dry matter basis. options include: “Mixed with grass hay or other silage, it • Grazing/green manure. Turn in livestock makes an excellent feed,” he says, adding value when the clover reaches 4 inches tall, let to its cover crop benefits and giving him them graze for several weeks, spray to kill, farming flexiblity. then plant grain sorghum within a couple of Updated in 2007 by Andy Clark days. He feeds an anti-bloat medication to

174 MANAGING COVER CROPS PROFITABLY Spring seeding provides yellow sweetclover Second-year growth comes from crown buds that ample time to develop an extensive root system form about an inch below the soil surface. Avoid and store high levels of nutrients and carbohy - mowing or grazing of sweetclover in the six- to drates necessary for over-wintering and robust seven-week period prior to frost when it is build - spring growth. It grows slowly the first 60 days ing final winter reserves. Root production practi - (153). Where weeds would be controlled by mow- cally doubles between Oct.1 and freeze-up. ing, no-till spring seeding in small grain stubble Sweetclover establishes well when sown with works well. winter grains in fall, but it can outgrow the grain Broadcast seeding for pure sweetclover stands in a wet season and complicate harvest. works in higher rainfall areas in early spring where soil moisture is adequate for seven to 10 Second-year management. After it breaks win - days after planting. No-till seeding works well in ter dormancy, sweetclover adds explosive and vig - small grain stubble. orous growth. Stems can reach 8 feet before Frostseeding into winter grains allows a harvest flowering, but if left to mature, the stems become of at least one crop during the life cycle of the woody and difficult to manage. Plants may grow sweetclover and helps control weeds while the extremely tall in a “sweetclover year” with high sweetclover establishes. Apply sweetclover seed rainfall and moderate temperatures. before rapid stem elongation of the grain. Cut Nearly all growth the second year is topgrowth, grain rate about one-third when planting the and it seems to come at the expense of root mass. crops together. From March to August in Ohio, records show top- Sweetclover spring seeded with oats exhibited growth increasing tenfold while root production poor regrowth after oat harvest in two years of a decreased by 75 percent (443). All crown buds Wisconsin study. To establish a sweetclover cover initiate growth in spring. If you want regrowth crop in this way, the researchers found sweet- after cutting, leave plenty of stem buds on 6 to 12 clover did not fare well in years when the com- inches of stubble. You increase the risk of killing bine head had to be run low to pick up lodged the sweetclover plant by mowing heav ier stands, oats. When oats remained upright (sacri ficing at shorter heights, and/or at later growth stages, some straw for a higher cut), sweetclover grew especially after bloom (183). adequately (402). Before it breaks dormancy, sweetclover can You can plow down spring-planted yellow withstand flooding for about 10 days without sweetclover in late fall of the planting year to cash significant stand loss. Once it starts growing, in early on up to half its N contribution and a bit however, flooding will kill the plants (183). less than half its biomass. Plant biennial sweetclover through late sum- Killing mer where winters are mild, north through Zone For best results ahead of a summer crop or fallow, 6. Plant at least six weeks before frost so roots can kill sweetclover in the second year after seeding develop enough to avoid winter heav ing. In the when stalks are 6 to 10 inches tall (183, 361). It Northern Plains into Canada, it should be planted can be killed by mowing, cultivating or disking by late August. once it reaches late bloom stage (32). Killing sweetclover before bud stage has several benefits: First-year management. Seeding year harvest 80 percent of the potential N is present; N release or clipping is usually discouraged, because the is quick because the plant is still quite vegetative energy for first-year regrowth comes directly from with a high N percentage in young stalks and photosynthesis (provided by the few remaining roots; and moisture loss is halted with out reduc- leaves), not root reserves (361, 402). ing N contribution. Sweetclover may regrow from Top growth peaks in late summer as the plant’s healthy crowns if incorporated before the end of main taproot continues to grow and thicken. dormancy. For optimum full-sea son organic mat-

SWEETCLOVERS 175 ter contribution, mow prior to blossom stage Pest Management whenever sweetclover reaches 12 to 24 inches Sweetclover is a rather poor competitor in its high before final incorporation or termination establishment year, making it difficult to establish (361). Mowing or grazing at bloom can kill the pure sweetclover in a field with significant weed plants. pressure. Once established, it provides effective In dryland areas, the optimum termination date weed control during the first fall and spring of fal- for a green manure varies with moisture condi - low, whether or not it is harvested for hay, incor- tions. In a spring wheat>fallow rotation in porated or left on the soil surface (33). Saskat chewan, sweetclover Sweetclover residue is said to be allelopathic During its incorporated in mid-June against kochia, Russia thistle, dandelion, perennial of a dry year provided 80 sowthistle, stinkweed and green foxtail. Repeated second season, percent more N the fol - mowing of yellow sweetclover that is then left to yellow sweet- lowing spring than it did mature is reported to have eradicated Canada this - when incorporated in tle. Letting sweetclover bloom and go to seed clover can grow early July or mid-July— dries out soil throughout the profile, depleting the 8 feet tall while even though it yielded up root reserves of weeds. to a third less biomass at Sweetclover weevil (Sitonia cylindricollis) is a roots penetrate the June date. Mineraliz - major pest in some areas, destroying stands by ation from sweetclover defoliating newly emerged seedlings. Long rota - 5 feet deep. usually peaks about a year tions can reduce damage, an important factor for after it is killed. The organic farmers who depend on sweetclover fer - potential rate of N release tility and soil improvements. In the worst years of decreases as plants mature and is affect ed by soil an apparent 12 to 15-year weevil cycle in his area, moisture content (147). “every sweetclover plant across the countryside In this study, the differences in N release were is destroyed,” according to organic farmer David consistent in years of normal precipitation, but Podoll, Fullerton, N.D. “Then the weevil popula - were less pronounced. Little N mineralization tion crashes, followed by a few years where occurred in the incorporation year. Nitrogen addi- they’re not a problem, then they begin to rebuild.” tion peaked in the following year, and has been Cultural practices have not helped change the shown to continue over seven years fol lowing yel- cycle, but planting early with a non-competitive low sweetclover (147). nurse crop (flax or small grains) gives sweetclover In northern spring wheat areas of North plants the best chance to survive weevil foraging, Dakota, yellow sweetclover is usually terminated Podoll says. Further research is needed to develop in early June just at the onset of bloom, when it management techniques to control the weevil. reaches 2 to 3 feet tall. This point is a compro- In a three-year Michigan trial of crop rotations mise between cover crop gain (in dry matter to decrease economic losses to nematodes, a yel- and N) and water consumption. A quick kill from low sweetclover (YSC)>YSC>potato sequence tillage or haying is more expensive and labor- out-yielded other combinations of rye, corn, intensive than chemical desiccation, but it stops sorghum-sudangrass and alfalfa. Two years of moisture-robbing transpiration more quickly clover or alfalfa followed by potatoes led to a yield (153). response equivalent to application of a nemati - Grazing is another way to manage second-year cide for control of premature potato vine death sweetclover before incorporation. Start early in (78). Legume-supplied N coupled with an overall the season with a high stocking rate of cattle to nutrient balance and enhanced cation exchange stay ahead of rapid growth. Bloat potential is capacity from the cover crop are thought to be slightly less than with alfalfa (153). involved in suppressing nematode damage (271).

176 MANAGING COVER CROPS PROFITABLY Crop Systems planting will tend to increase stand. Band-seeding In the moderately dry regions of the central and sweetclover over the row with an insecticide box northern Great Plains, “green fallow” systems with at sunflower planting proved more successful in water-efficient legumes can be substituted for the trial. The method also permits between-row bare-ground or stubble mulch fallow. In fallow cultivation (153). years, no cash crop is planted with the intent of Even though legume green manures in another recovering soil moisture, breaking disease or North Dakota study used about 2.8 inches (rain - weed cycles and maximizing yields of following fall equivalent) more water than fallow, they led cash crops. The retained residue of “brown” fal- to a 1-inch equiva- low lessens the erosion and evapo ration of tillage- lent increase over Sweetclover is the intensive “black fallow,” but “green fallow” offers fallow in soil water even more benefits in terms of soil biological life, content in the top 3 best producing biodiversity, beneficial insect habitat, possi ble har- inches of soil the fol - warm- season forage vestable crops and alternate forages. lowing spring (14). Rapeseed (Brassica campestris) is a summer One green fallow legume, even annual cash crop in the dryland West that can option is planting serve as a nurse crop for sweetclover. A yellow sweetclover topping alfalfa. Saskatchewan study of seeding rates showed opti - with spring barley mum clover yield came when sweetclover was or spring peas. This sown at 9 lb./A and rapeseed was sown at 4.5 is challenging, how ever, because barley can be lb./A. The mixture allows an adequate stand of overly competitive while herbi cide compatibility sweetclover that provides soil protection after the is a concern with the peas. low-residue rapeseed (255). Further north into the Canadian Great Plains, Sole-cropped oilseed species (rapeseed, sun - sweetclover depleted soil moisture by September flower, crambe and safflower) require herbicides of year 1, but by May of year 2, soil moisture was for weed control. Many of these materials are greater due to snow trapping, increased infiltra- compatible with legumes, offering a post-emer - tion and reduced evaporation (32). gent weed-control option if the covers do not ade - Fred Kirschenmann of Windsor, N.D., controls quately suppress weeds. The covers greatly spring weed flushes on his fallow after sunflow - reduce the erosion potential after oilseed crops, ers with an initial shallow chisel plowing then a which leave little residue over winter (153). rod weeder pass or two before planting sweet- Interplanting works with tall crops. A clover with a nurse crop of buckwheat or oats Wisconsin researcher reported success drilling (or millet, if there is less soil moisture). He har- sweetclover between the rows when corn was 6 vests buckwheat, hoping for a 900 lb./A yield, to 12 inches tall. Overseeding sweetclover into then lets the clover grow and overwinter. In sweet corn works even better due to greater light early summer, when he begins to see yellow penetration. blossoms, he disks the cover, lets it dry, then runs Soil water availability at cover crop planting a wide-blade sweep plow just below the surface and depletion during growth are always a con- to cut apart the crowns. The biomass contribu- cern in semi-arid regions. The potential benefits tion of the sweetclover fallow builds up organic must be balanced against possible negative effects matter, he says, in contrast to the black-fallow on the cash crop. route of burning up organic matter to release N. Sweetclover overseeded into sunflowers at last Preventing humus depletion holds back the cultivation succeed about half the time, North dreaded kochia weed. Dakota trials show. Dry conditions or poor seed- In temperate areas you can overseed spring to-soil contact were the main reasons for not get - broc coli with HUBAM annual sweetclover, let the ting a stand. A heavier seeding rate or earlier cover grow during summer, then till it in before

SWEETCLOVERS 177 planting a fall crop. Alternatively, you can allow it COMPARATIVE NOTES to winterkill for a thick, lasting mulch. In Pennsylvania, Eric and Anne Nordell seed Sweetclover and other deep-rooted biennial and sweetclover after early vegetables (in June or July) perennial legumes are not suited for the most and allow it to grow throughout the summer. It severely drought-prone soils, as their excessive puts down a deep taproot before winter, fixes soil moisture use will depress yield of subsequent nitrogen and may bring nutrients to the soil sur- wheat crops for years to come (163). face from deep in the soil profile. See Full-Year When planting sweetclover after wheat har - Covers Tackle Tough Weeds, p. 38. vest, weeds can become a problem. An organic farmer in northeastern Kansas reports that to kill Other Options cocklebur, he has to mow lower than the sweet- First-year forage has the same palatability and clover can tolerate. Annual alfalfa can tolerate low feeding value as alfalfa, although harvest can mowing (205). reduce second-year vigor. Second-year forage is of After 90 days’ growth in a North Dakota dryland lower quality and legume comparison, a June planting of yellow Sweetclover becomes less palatable as sweetclover produced dry matter and N compara- plants mature, but may tolerates a wide ble to alfalfa and lespedeza (Lespedeza stipulacea total 2 to 3 tons per acre Maxim). Subclover, fava beans (Vicia faba) and range of harsh (120). field peas had the best overall N-fixing efficiency in Growers report seed the dryland setting because of quick early season environments, yield of 200 to 400 lb./A growth and good water use efficiency (331). poor soils and in North Dakota. Minimize shattering of seedpods Cultivars. Yellow cultivars include MADRID, which pests. by swathing sweetclover is noted for its good vigor and production, and its when 30 to 60 percent of relative resistance to fall freezes. GOLDTOP has its pods are brown or excellent seedling vigor, matures two weeks later, black. Pollinating insects are required for good provides larger yields of higher quality for age and seed yield (183). has a larger seed than MADRID (361). Yellow com- Hard seed that escapes harvest will remain mon and YUKON joined GOLDTOP and MADRID—all in the soil seed bank, but organic farmer high-coumarin types—as the highest yielding culti- Rich Mazour of Deweese, Neb., sees that as a plus. vars in a six-year North Dakota test (269). A 20- to 30-percent stand in his native grass pas - Leading white biennial cultivars are DENTA, tures comes on early each spring, giving his cattle POLARA and ARCTIC. POLARA and ARCTIC are adapt- early grazing. Once warm-season grasses start to ed to very cold winters. Best for grazing are the grow, they keep the clover in check. In tilled lower-producing, low-coumarin cultivars DENTA fields, sweep cultivators and residue-man agement and POLARA (white) and NORGOLD (yellow). tillage implements take care of sweetclovers with other tap-rooted “resident vegeta tion,” Mazour Seed sources. See Seed Suppliers (p. 195). says.

178 MANAGING COVER CROPS PROFITABLY WHITE CLOVER Trifolium repens

Also called: Dutch White, New Zealand White, Ladino

Type: long-lived perennial or winter annual legume

Roles: living mulch, erosion protec - tion, green manure, beneficial insect attraction

Mix with: annual ryegrass, red clover, hard fescue or red fescue

See charts, pp. 66 to 72, for ranking and management summary.

hite clovers are a top choice for “living The best of 36 varieties tested in north-central mulch” systems planted between rows Mississippi for cover crop use were ARAN, GRASSLAND Wof irrigated vegetables, fruit bushes or KOPU and KITAOOHA. These ranked high for all traits trees. They are persistent, widely adapted peren- tested, including plant vigor, leaf area, dry matter nial nitrogen producers with tough stems and a yield, number of seed-heads, lateness of flowering dense shallow root mass that protects soil from and upright stems to prevent soil contact. Ranking erosion and sup presses weeds. Depending on the high were ANGEL GALLARDO, CALIFORNIA LADINO and type, plants grow just 6 to 12 inches tall, but thrive widely used LOUISIANA S-1 (392). when mowed or grazed. Once established, they White clover performs best when it has plenty stand up well to heavy field traffic and thrive of lime, potash, calcium and phosphorus, but it under cool, moist conditions and shade. tolerates poor conditions better than most clovers. Its perennial nature depends on new Three types: Cultivars of white clover are plants continually being formed by its creeping grouped into three types by size. The lowest stolons and, if it reaches maturity, by reseeding. growing type (Wild White) best survives heavy White clover is raised as a winter annual in the traffic and grazing. Intermediate sizes (Dutch South, where drought and diseases weaken White, New Zealand White and Louisiana S-1) stands. It exhibits its perennial abilities north flower earlier and more profusely than the larger through Hardiness Zone 4. The short and inter - types, are more heat-tolerant and include most of mediate types are low biomass producers, while the economically important varieties. The large the large ladino types popular with graziers can (Ladino) types produce the most N per acre of produce as much biomass as any clover species. any white types, and are valued for forage quality, especially on poorly drained soil. They are gener - BENEFITS ally less durable, but may be two to four times taller than intermediate types. Fixes N. A healthy stand of white clover can pro - Intermediate types of white clover include many duce 80 to 130 lb. N/A when killed the year after cultivated varieties, most originally bred for forage. establishment. In established stands, it also may

WHITE CLOVER 179 Tough, low-growing provide some N to root each season. Reseeding increases the number and shade tolerant, growing crops when of new plants if you allow blossoms to mature. it is managed as a liv- this perennial ing mulch between Fits long, cool springs. In selecting a fall-seed - crop rows. Because it ed N-producer, consider white clover in areas is often used as a contains more of its with extended cool springs. MERIT ladino clover living mulch in total N in its roots was the most efficient of eight major legumes than other legumes, evaluated in a Nebraska greenhouse for N2 fixed vegetable systems. partial tilling is an per unit of water at 50° F. Ladino clover, as well as especially effective hairy vetch and fava beans (Vicia faba) were the way to trigger N only legumes to grow well at the 50° F tempera- release. The low C:N ratio of stems and leaves ture (334). causes them to decom pose rapidly to release N. Overseeded companion crop. Whether frost- Tolerates traffic. Wherever there’s intensive seeded in early spring into standing grain, broad- field traffic and adequate soil moisture, white cast over vegetables in late spring or into sweet clover makes a good soil covering that keeps corn in early summer, white clover ger minates alleyways green. It reduces compaction and dust and establishes well under the primary crop. It while protecting wet soil against trauma from grows slowly while shaded as it develops its root vehicle wheels. White clover converts vulnerable system, then grows rapidly when it receives more bare soil into biologically active soil with habitat light. for beneficial organisms above and below the soil surface. MANAGEMENT

Premier living mulch. Their ability to grow in Establishment & Fieldwork shade, maintain a low profile, thrive when repeat - Widely adapted. White clover can tolerate wet edly mowed and withstand field traffic makes soil—even short flooding—and short dry spells, intermediate and even short-stemmed white and survives on medium to acid soils down to pH clovers ideal candidates for living mulch systems. 5.5. It volunteers on a wider range of soils than To be effective, the mulch crop must be managed most legumes, but grows better in clay and loam so it doesn’t compete with the cash crop for light, soils than on sandy soils (120). Ladino prefers nutrients and moisture. White clover’s persistence sandy loam or medium loam soils. in the face of some herbicides and minor tillage is Use higher seeding rates (5 to 9 lb./A drilled, 7 used to advantage in these systems (described to 14 lb./A broadcast) when you overseed in below) for vegetables, orchards and vineyards. adverse situations caused by drought, crop residue or vegetative competition. Drill 4 to 6 Value-added forage. Grazed white clover is lb./A when mixing white clover with other highly palatable and digestible with high crude legumes or grasses to reduce competition for protein (about 28 percent), but it poses a bloat light, moisture and nutrients. risk in ruminants without careful grazing manage - Frostseeding of small-seeded clovers (such as ment practices. alsike and white) should be done early in the morning when frost is still in the soil. Later in the Spreading soil protector. Because each white day, when soil is slippery, stand establishment will clover plant extends itself by sending out root-like be poor. Frostseed early enough in spring to allow stolons at ground level, the legume spreads over for several freeze-thaw cycles. time to cover and protect more soil surface. Late-summer seeding must be early enough to Dropped leaves and clipped biomass effectively give white clover time to become well estab- mulch stolons, encouraging new plants to take lished, because fall freezing and thawing can read -

180 MANAGING COVER CROPS PROFITABLY ily heave the small, shallow-rooted plants. Seeding about 40 days before the first killing frost is usu - ally enough time. Best conditions for summer establishment are humid, cool and shaded (120, 361). Legumes suffer less root damage from frost heaving when they are planted with a grass. In warmer regions of the U.S. (Zone 8 and warmer), every seeding should be inoculated. In cooler areas, where N-fixing bacteria persist in the soil for up to three years, even volunteer wild white clover should leave enough bacteria behind

to eliminate the need for inoculation (120). Sarrantonio Marianne Mowing no lower than 2 to 3 inches will keep white clover healthy. To safely overwinter white WHITE CLOVER (Trifolium repens— clover, leave 3 to 4 inches (6 to 8 inches for taller intermediate type) types) to prevent frost damage. Crop Systems Killing Living mulch systems. As a living mulch, white Thorough uprooting and incorporation by chisel clover gives benefits above and below ground or moldboard plowing, field cultivating, undercut - while it grows between rows of cash crops, pri - ting or rotary tilling, or—in spring—use of a suit - marily in fruits, vegetables, orchards and vine- able herbicide will result in good to excellent kill yards. Living mulch has not proved effective in of white clover. Extremely close mowing and par- agro nomic crops to this point. To receive the tial tillage that leaves any roots undisturbed will multiple benefits, manage the covers carefully suppress, but not kill, white clover. throughout early crop growth—to keep them from compet ing with the main crop for light, Pest Management nutrients, and especially moisture—while not Prized by bees. Bees work white clover blos - killing them. Several methods can do that effec- soms for both nectar and pollen. Select insect- tively. management measures that minimize negative impact on bees and other pollinators. Michigan Hand mowing/in-row mulch. Farmer Alan blueberry growers find that it improves pollina- Matthews finds that a self-propelled 30-inch tion, as does crimson clover (see Clovers Build rotary mower controls a clover mix between Soil, Blueberry Production, p. 182). green pepper rows in a quarter-acre field. He uses 40-foot wide, contour strip fields and the living Insect/disease risks. White clovers are fairly tol - mulch to help prevent erosion on sloping land erant of nematodes and leaf diseases, but are sus - near Pittsburgh, Pa. In his 1996 SARE on-farm ceptible to root and stolon rots. Leading insect research, he logged $500 more net profit per acre pests are the potato leafhopper (Empoasca fabae), on his living mulch peppers than on his conven - meadow spittlebug (Philaenis spumarius), clover tionally produced peppers (259). leaf weevil (Hypera punctata), alfalfa weevil Matthews mulches the transplants with hay, 12 (Hypera postica) and Lygus bug (Lygus spp.). inches on each side of the row. He hand-seeds the If not cut or grazed to stimulate new growth, the cover mix at a heavy 30 lb./A between the rows. buildup of vegetation on aged stolons and stems cre- The mix is 50 percent white Dutch clover, 30 per - ates a susceptibility to disease and insect problems. cent berseem clover, and 20 percent HUIA white Protect against pest problems by select ing resistant clover, which is a bit taller than the white Dutch. cultivars, rotating crops, maintaining soil fertility and He mows the field in fall, then broadcasts medium employing proper cutting sched ules (361). red clover early the next spring to establish a hay

WHITE CLOVER 181 Clovers Build Soil, Blueberry Production

In the heart of blueberry country in the to two farms: Double-R Blueberry Farm and leading blueberry state in the U.S., Richard Wind Dancer Farms, jointly operated by RJ James “RJ” Rant and his mother, Judy Rant, are and his mother, Judy. breaking new ground and reaping great Michigan blueberry farmers have been rewards. Thanks to cover crops such as white using cover crops for many years, and top- and crimson clover taking center stage on producing Ottawa County farmers are no their two family farms, the blueberry crop is exception. Growing blueberry bushes on thriving and the farmers are reaping significant ten-foot centers, there is a lot of space rewards. between rows that farmers try to manage The Rants’ soil is also on the receiving end as economically and efficiently as possible. of the multiple benefits of white and crimson Seeking something that will not compete with clover cover crops. the cash crop, most farmers choose rye or Judy and her husband, Richard Rant, planted sod. Both require significant management in their first bushes in the early 1980s while both terms of time and labor, not to mention seed were still working full time off the farm. They and fuel costs to plant and kill. managed the farm until retirement without RJ Rant took a different tack. Their sandy going into debt—something of an loam soils were decent but not excellent, and accomplishment during that period—but the his research led him to focus his efforts on operation never really took off. Still in high improving the soil by reducing tillage and school when his father passed away, RJ Rant planting cover crops. While rye, an annual stepped into the operation during college. cover crop, required tillage in fall before Choosing farming over graduate school, RJ planting and in spring to kill and incorporate, began a quest to improve the blueberry perennial white clover could be grown for operation and its bottom line. His focus on two or more years without tilling. Because it is soil-building and cover crops proved key to low-growing, the clover required less labor in the success of their operation, now expanded planting and mowing. field and replace the berseem, which is not win- The research showed that in dry years, mowing terhardy (259). alone won’t suppress a living mulch enough to New Zealand white clover provided good keep it from competing for soil moisture with weed control for winter squash in the wetter of crops in 16-inch rows. Further, weeds can be even two years in a New York trial. It was used in an more competitive than the clover for water dur - experimental non-chemical system relying on ing these dry times (282). over-the-row compost for in-row weed control. A California study showed that frequent mow- Plants were seeded into tilled strips 16 inches ing can work with careful management. A white wide spaced 4 feet apart. Poor seed estab lishment clover cover reduced levels of cabbage aphids in and lagging clover growth in the drier year creat- harvest ed broccoli heads compared with cleaned weed problems, especially with perennial cultivated broccoli. The clover-mulched plants, in competitors. The living mulch/compost system strip-tilled rows 4 inches wide, had yield and size yielded less than a conventionally tilled and comparable to clean cultivated rows. However, fertilized control both years, due in part to only intensive irrigation and mowing prevented delayed crop development from the in-row com - moisture compe tition. To be profitable commer- post (282). cially, the system would require irrigation or a less

182 MANAGING COVER CROPS PROFITABLY “There are so many positive things I could Soil-building remains a primary objective of say about cover crops,” Rant says. “The reason I Rants cover crop program. Compacted soils keep using them is because they save me time are a problem for blueberries, which prefer and money.” loose, friable soil. To build better soil structure, Although he started his research and Rant is working with MSU’s Mutch to improve planted his first Alsike clover crop on his own, soil organic matter with cover crop mulches RJ soon found research partners at Michigan and manures. State University. He cooperates with researcher Mutch and Rant are studying crimson clover Dale Mutch to fine-tune cover crop selection, reseeding, another cost-saving measure, planting methods and management options. comparing mowing and tilling the crimson “I get really excited when I think about clover after it has set seed. They are also improving my soils,” Rant says. “I see my fields studying pH ranges for the clovers, which prefer as one unified system, and the biology of the a higher pH than the blueberry cash crop. soil in the inter-rows is as important as the soil Mutch and Michigan State researcher Rufus and fertility up and down my blueberry rows.” Isaacs are helping to elucidate other Early screening of different cover crops led management aspects of clover cover crops, Rant to further test crimson clover, a winter such as whether honeybees and native bees annual cover crop that not only grows well in such as mason bees and sweat bees are fall and spring, but also shows great potential attracted to clovers. to reseed itself, further reducing costs. They “The clovers work really well for blueberry have also tested red clover, small white clover, production, rather than needing to fit system mustard, rye and spring buckwheat. Rant says to cover crop. If you really want to do this, you white clover is his favorite because it is low can make it work,” says RJ. growing and out-competes weeds. —Andy Clark thirsty legume, as well as field-scale equipment the clover. Leaf smut Healthy stands able to mow between several rows in a single caused less problem on the pass (93). living-mulch corn than on can produce Chemical suppression is unpredictable. An the clean-cultivated check 80 to 130 lb. appli cation rate that sets back the clover suffi- plot (170). ciently one year may be too harsh (killing the N/A when killed clover) or not suppressive the next year due to Crop shading. Sweet the year after moisture, temperature or soil conditions. corn shading can hold white clover in check establishment. Partial rotary tillage. In a New York evaluation of when corn is planted in mechanical suppression, sweet corn planting strips 15- inch rows and about 15 20 inches wide were rotary tilled June 2 into white inches apart within the row. This spacing yielded clover. Although mowing (even five times) didn’t higher corn growth rates, more marketable ears sufficiently suppress clover, partial rotary tilling at per plant and higher crop yields than conven- two weeks after emergence worked well. A strip tional plots without clover in an Oregon study. of clover allowed to pass between the tines led to Corn was planted into tilled strips 4 to 6 inches ample clover regrowth. A surge of N within a wide about the same time the clover was chemi- month of tilling aided the growing corn. The loss cally suppressed. Adapted row-harvesting equip- of root and nodule tissue following stress from ment and hand picking would be needed to make tillage or herbicide shock seems to release N from the spacing practical (139).

WHITE CLOVER 183 Unsuppressed white Dutch clover established COMPARATIVE NOTES at asparagus planting controlled weeds and provided N over time to the asparagus in a Wisconsin • White clover is less tolerant of basic soils study, but reduced yield significantly. Establishing above pH 7 than are other clovers. the clover in the second year or third year of an • In a Wisconsin comparison, ladino clover bio - aspara gus planting would be more effective mass was similar to mammoth red clover (312). when spring-seeded (402). • White clover stores up to 45 percent of its N Other Options contribution in its roots, more than any other Seed crop should be harvested when most seed major legume cover crop. heads are light brown, about 25 to 30 days after • Ladino and alsike are the best hay-type full bloom. legumes on poorly drained soils. Intermediate types of white clover add protein • Spring growth of fall-seeded white clover and longevity to permanent grass pastures with - begins in mid-May in the Midwest, about the out legumes. Taller ladino types can be grazed or same time as alfalfa. harvested. Living mulch fields can be overseeded with grasses or other legumes to rotate into pas - Seed sources. See Seed Suppliers (p. 195). ture after vegetable crops, providing IPM options and economic flexibility.

184 MANAGING COVER CROPS PROFITABLY WOOLLYPOD VETCH

Vicia villosa ssp. dasycarpa

Also called: LANA vetch; also spelled woolypod vetch

Cycle: cool-season annual

Type: legume

Roles: N source, weed suppressor, erosion preventer, add organic matter, attract bees

Mix with: other legumes, grasses See charts, p. 66 to 72, for ranking and management summary.

pecialty vetches such as woollypod and pur - In Zone 5 and colder and parts of Zone 6, wool - ple vetch (Vicia benghalensis) are faster- lypod vetch can serve as a winterkilled mulch— Sgrowing alternatives to hairy vetch (Vicia or as a quick, easy-to-mow spring cover—for villosa) in Hardiness Zone 7 and warmer. weed control and N addition to vegetable trans - Requiring little or no irrigation as a winter cover plants. It’s a good choice as an overwintering in these areas, they provide dependable, abundant cover before or after tomato crops in Zone 6 and N and organic matter, as well as excellent weed warmer. In California, LANA provided the most N suppression. and suppressed the most weeds during two con- Many growers of high-value crops in California secutive but distinctly different growing seasons, rely on one or more vetch species as a self-reseed - compared with purple vetch and other legume ing cover crop, beneficial insect habitat and mixtures (413, 414). mulch. They can mow the vetch during winter and in late spring after it reseeds. BENEFITS Some vineyard managers seed LANA woollypod vetch each year with oats or as part of a legume N Source. A first-year, overwintering stand of mix—common vetch, subterranean clover, a woollypod vetch easily will provide more than medic and LANA, for example. They plant the mix 100 pounds of N per acre in any system when in alternate alleyways to save on seeding costs allowed to put on spring growth. The popular and reduce moisture competition, while ensuring LANA cultivar starts fixing N in as little as one sufficient cover that they can mow or disk. LANA’s week after emergence. climbing tendency (even more so than purple or LANA can contribute as much as 300 pounds of common vetch) and abundant biomass can N its first year or two, given adequate moisture become problems in vineyards and young and warm spring growing conditions (273, 396). orchards, but can be readily managed with regular Fall-planted LANA incorporated before a corn crop monitoring and timely mowing. can provide a yield response equivalent to 200 lb.

WOOLLYPOD VETCH 185 N/A, a California study showed (273). Similar MANAGEMENT results have been seen in tomato research in California (396). In western Oregon, a yield Establishment & Fieldwork response equivalent to 70 lb. N/A for sweet corn Woollypod does well on many soil types—even has been observed (364). poor, sandy soil—and tolerates moderately acidic to moderately alkaline conditions. It’s well-adapted to Plenty of soil-building organic matter. most orchard and vineyard soils in California (422). Woollypod typically produces more dry matter It establishes best in recently tilled, nutrient- than any other vetch. LANA shows better early deficient fields. Tillage helps enhance the reseed- growth than other vetches, even during cool late ing capability of vetches (63). LANA woollypod fall and winter weather in Zone 7 and warmer. vetch hasn’t done as well in some no-till sys tems LANA shows explosive growth in early spring in as it was expected to. the Pacific Northwest (364) and in late winter and Given adequate moisture, however, broadcasting early spring in California LANA even at low to moderate rates—and with light Woollypod vetch when moisture is ade- incor poration—can give satisfac tory results from fall is often used quate. It can provide up seedings, especially if the stand is allowed to grow to 8,000 lb. DM/A, which through mid-spring. If your goal is to shade out com- in mixes in breaks down quickly and petition quickly, however, broadcast at medi um to improves soil structure high rates and incorporate lightly. California (63, 273, 396). You might not recognize the emerging plant orchards and without its characteristic multiple leaflets, says Frost protectant. Some Glenn Anderson. “You should spot it within two vineyards. orchard growers have weeks of planting, three at the latest, depending found that keeping a thick on temperature and soil conditions. Even at 6 floor cover before the inches, it’ll still look spindly. It won’t really leaf out blossom stage can help prolong a perennial crop’s until late winter and early spring, when more dormant period by up to 10 days in spring. “This aggressive growth kicks in.” That may continue reduces the risk of early frost dam age (to the blos- until maturity in mid- to late May. soms, by delaying blossoming) and lengthens the blossoming period of my almond trees,” notes Fall planting. Most growers seed at low to medi - almond grower Glenn Anderson, Hilmar, Calif. um rates, regardless of seeding method. If drilling, 1 /2 to 1 inch deep is best, although up to 2 inches Smother crop.Woollypod’s dense spring growth will work for early seedings. If broadcasting, fol - smothers weeds and also provides some allelo- low with a cultipacker or a shallow pass of a pathic benefits. Of 32 cover crops in a repli cated spike-toothed harrow. study at a California vineyard, only LANA com- Seedbed preparation is crucial for establishing pletely suppressed biomass production of the a healthy cover crop stand in vineyards. California dominant winter annual weeds such as chick - viticulturist and consultant Ron Bartolucci rec - weed, shepherd’s purse, rattail fescue and annual ommends making two passes with a disk to kill ryegrass (422). existing vegetation and provide some soil distur - bance. He cautions against using a rotary tiller, Beneficial habitat. Woollypod vetch attracts which can pulverize the soil and reduce its water- many pollinators and beneficial insects. In some holding capacity (211). orchards, these beneficials move up into the tree Bartolucci prefers to drill rather than broadcast canopy by late spring, so you can mow the floor cover crops, saving on seed costs and ensuring cover after it reseeds and not worry about loss of seed-to-soil contact. He recommends the eco - beneficial habitat (184). nomical, alternate row planting that also ensures easy access for pruning grape vines.

186 MANAGING COVER CROPS PROFITABLY Don’t wait too long in fall to seed woollypod ing over vine cor- vetch in Zone 7 and warmer, however. If you wait dons. In vine- until the soil starts getting cold, in mid-October in yards without Oregon and early November in parts of central sprinklers for California, germination will be poor and the stand frost protection, disappointing. Seed too early, though, and you some growers miss the early moisture benefit of the Central incorporate Valley’s fog season and will need to irrigate more legume mixes in before the rainy season. spring, before the Regardless of your planting method, seed wool - soil becomes too lypod vetch into moist soil or irrigate immediate - dry for disking. ly after seeding to help germination (273). If Where sprinklers are irrigation is an option but you want to conserve used, the covers might water costs, try seeding just before a storm is fore - be allowed to grow for a

cast, then irrigate if the rain misses you. longer period and pro- Sears Elayne vide additional N. Timing is WOOLLYPOD Spring planting. Planted in early spring, woolly- important when disking, VETCH pod vetch can provide plowdown N by Memorial however, as you don’t want (Vicia villosa ssp. Day for a summer annual cash crop in the Northeast. to make equipment access dasycarpa) difficult or compact soil Mowing & Managing during wet spring condi- Woollypod vetch can survive freezing conditions tions (211). for days, but severe cold can markedly reduce its Given the high dry matter production from dry matter and N production (212, 273). woollypod vetch when it’s allowed to grow at In most cases, main challenges for an estab - least until late March, two or three diskings or lished woollypod vetch stand include managing mowings will encourage rapid decomposition. its abundant growth and viny tendrils and ensur- Power spaders can reduce soil compaction when ing adequate moisture for your primary crop. In incorporating vetches in spring conditions, com - wet environments such as western Oregon, how - pared with heavier disk harrows (421). ever, LANA vetch can retard spring soil drying and seedbed preparation for summer crops (364). Moisture concerns. Many orchard and vineyard Woollypod responds well to mowing, as long as growers find it helpful to drip irrigate tree or vine you keep the stand at least 5 inches tall and avoid rows if they are growing an aggressive cover crop mowing during the two-month period just before such as LANA between the rows for the first time. it reseeds. “I can mow as late as mid-March and In California vineyards where irrigation isn’t used, still see good reseeding,” says Glenn Anderson, an a few growers report that vines seem to lose vigor organic almond grower in California’s Central faster when grown with cover crops. Others Valley. “After that, I may mow if I want to prevent haven’t observed this effect. After a few years of some frost damage, but I know I’ll lose some of grow ing leguminous covers, many find that their the vetch through reduced reseeding.” soil is holding moisture better and they need less Anderson usually mows the floor cover once or water to make the system work. twice before mid-March and after it reseeds. He cuts in the direction of prevailing winds—which Reseeding concerns. Vetch mixtures often fail can be on a diagonal to his tree rows—to facilitate to reseed effectively, especially if they have been air movement throughout the orchard, especially mowed at the wrong time or soil fertility is high. when he anticipates moist air heading his way. Some vineyard managers expect low persistence In vineyards, “high chopping” legume mixes to and reseed a vetch mix in alternate rows every a 12-inch height can help keep them from trellis - fall, or reseed spotty patches.

WOOLLYPOD VETCH 187 Regardless of mowing regime, LANA’s persis - tuce drop incidence the summer after LANA had tence as a self-reseeding cover diminishes over been incorporated, but wasn’t as problematic the time, and other resident vegetation starts to take following year. Woollypod vetch probably isn’t a over. That’s a sign that the cover’s water-holding, good choice if you’re growing crops susceptible fertility- and tilth-enhancing benefits have kicked to this pathogen. in, says Glenn Anderson. It’s natural to expect a change in the resident Other Options vegetation over time, observes Anderson. After a Seed. Woollypod vetch is a prolific seed produc- few years of reseeding itself—and providing er, but its pods are prone to shattering. You can abundant dry matter and increase seed harvest by raking the field (without LANA woollypod nitrogen—the LANA he mowing, if possible) to gather the crop into vetch shows had clear seeded at low windrows for curing, before combining with a rates between orchard belt-type rubber pickup attachment (421). explosive growth rows on half his acreage eventually diminished to Forage. Like most vetches, LANA is a somewhat in early spring about 10 percent of the bitter yet palatable forage when green, and the in the Pacific resident vegetation, he palatability increases with dryness (421). It is a notes. Subclovers and nutritious forage for rangeland use (421). Northwest. other legumes he intro - For hay, it is best cut in full bloom. The leaves duced have become dry rapidly and swaths can be gathered within a more prominent. Those day or two (421). legumes may have better self-reseeding capability than LANA, other growers note. COMPARATIVE NOTES

Pest Management • Woollypod has slightly smaller flowers than Woollypod vetch outcompetes weeds and will hairy vetch, and its seeds are more oval than quickly resolve most weed problems if seeded at the nearly round seeds of hairy vetch. LANA high rates. Woollypod also provides some allelo- also has a higher proportion of hard seed than pathic benefits. A root exudate can reduce growth hairy vetch (422). in some young grasses, lettuces and peas, however. •LANA shows more early growth than common Hard seed carryover can cause LANA to become vetch, although both increase their biomass a weed in subsequent cash crops and vineyards, dramatically by midspring. however (102). Its strong climbing ability can •LANA and purple vetch are more cold-sensitive cover grape vines or entwine sprinklers. In than common vetch or hairy vetch. Once orchards, it’s fairly easy to cut or pull LANA vines out estab lished, LANA can tolerate early frosts for of the canopy of young trees. Mowing or “high a few days (especially if the temperature chopping” may be needed, especially in vineyards, doesn’t fluc tuate widely or with some snow even though this can reduce LANA’s reseeding rate. cover) and is hardier than purple vetch, which Insects pests aren’t a major problem with wool- is more sus ceptible to early spring dieback lypod vetch, in part because it attracts lady bee- (149). tles, lacewings, minute pirate bugs and other •LANA flowers about three weeks earlier than beneficials insects that help keep pests in check. purple vetch and has a better chance of set - LANA can be a host of Sclerotinia minor, a soil - ting seed in dryland conditions (273). borne pathogen that causes lettuce drop, a fungal •LANA and LANA mixes suppress weeds better disease affecting lettuce, basil and cauliflower than purple vetch (149). crops. In a California study involving cover crops that were deliberately infected with S. minor, the Seed sources. See Seed Suppliers (p. 195). pathogen levels were associated with higher let -

188 MANAGING COVER CROPS PROFITABLY Appendix A TESTING COVER CROPS ON YOUR FARM by Marianne Sarrantonio

To find your best cover crops, you needn’t you use field-scale machinery, establish field- become Dr. Science or devote your life to length plots. For row crops, use plots at least four research. It’s not hard to set up valid, on-farm tests rows wide, or strips based on your equipment and make observations. Follow these steps: width. Keep in mind the subsequent crop’s management needs. A. Narrow your options. Aim for a limited-scale trial of just two to five species or mixtures. You D. Design an objective trial. Plots need to be as can test the best one or two in a larger trial the uniform as possible, randomly selected for each next year. Unsure of the best place and time in option you’re testing, and preferably replicated (at your rotation? Start with small plots sep arated least two or three plots for each option). If parts from cropped fields and plant over a range of of the field have major differences (such as poor- dates, under optimal soil and weather condi tions. er drainage or weedy spots), put blocks or groups If you’re sure where and when to plant and have of plots together so each treatment has equal rep- just two or three covers to try, put the trial right resentation in each field part, or avoid those areas in your cropped fields, using your normal seedbed for your trial entirely. Label each plot and make a prepara tion. This method provides rapid feedback map of the trial area. on how the cover crops fit into your cropping sys - tem. Keep in mind management may need some E. Be timely. Regard the trial as highly as any tweaking (such as seeding rate or date) to get the other crop. Do as much or as little field prepara- best results. tion as you would for whole fields, and at an appropriate time. If possible, plant on two or B. Order small seed amounts. Many compa - more dates at least two weeks apart. In general, nies provide 1- to 10-pound bags if you give them seed winter annuals at least six weeks before a advance notice. If 50-pound bags are the only killing frost. Wheat and rye can be planted later, option, arrange to share it with other growers. although that will reduce the N-scavenging signif- Don’t eliminate a species just because seed price icantly. seems high. If it works well, it could trim other costs. You could consider growing your own seed F. Plant carefully. If seeding large plots with eventually, and perhaps even selling it locally. Be tractor-mounted equipment, calibrate your seed - sure to obtain appropriate inoculants if you’ll be ing equipment for each cover crop. This can testing legumes, which require species-specific prevent failures or performance differences due rhizobial bacteria so the cover can cap ture and to incor rect seeding rates. Keep a permanent “fix” N efficiently. See Nodulation: Match record of drill settings for future reference. A Inoculant to Maximize N (p. 122). hand-crank or rotary spin seeder works well for small plots getting less than five pounds of seed. C. Determine plot sizes. Keep them small Weigh seed for each plot into a separate con - enough to manage, yet large enough to yield ade - tainer. To calculate seeding rates for small plots, quate and reliable data. Plots two to four rows use this formula: 1 lb./acre = 0.35 oz (10 grams)/ wide by 50 to 100 feet could suffice if you grow 1000 ft2 area seeded. If your cover crop seeding vegetables for market. If you have 10 or more rate calls for 30 lb/acre, multiply 0.35 oz by 30. acres, quarter- or half-acre plots may be feasible. If You will need 10.5 oz (300 grams) of seed for

TESTING COVER CROPS 189 each 1000 ft2 you seed. Put half the seed in the H. Choose the best species for the whole seeder and seed smoothly as you walk the length farm system. Not sure which covers did best? of the field and back, with a little overlap in the Whatever you found, don’t be satisfied with only spread pattern. a single year’s results. Weather and management Then seed the remainder while walking in per - will vary over time. pendicular directions so you crisscross the plot in Assess performance by asking some of the a gridlike pattern. If broadcasting by hand, use a questions you answered about the cover niche similar distribu tion pattern. With small seed, mix (see Selecting the Best Cover Crops for your in sand or fresh cat litter to avoid seeding too Farm, p. 12). Also ask if a cover: much at a time. • was easy to establish and manage • performed its primary function well G. Collect data. Start a trial notebook or binder • avoided competing excessively with the pri - for data and observations. Management informa- mary crop tion could include: • seemed versatile • field location • is likely to do well under different conditions • field history (crops, herbicides, amendments, • fits your equipment and labor constraints unusual circumstances, etc.) • provides options that could make it even • plot dimensions more affordable • field preparation and seeding method • planting date and weather conditions In year two, expand the scale. Test your best-per- • rainfall after planting forming cover as well as a runner-up. With field • timing and method of killing the cover crop crops, try one-acre plots; stick with smaller plots • general comments for high-value crops. Also try any options that might improve the cover stand or its benefits. Growth data for each plot might include: Entries for the major cover crops in this book • germination rating (excellent, OK, poor, etc.), include some management tips that can help. seven to 14 days after seeding Record your observations faithfully. • early growth or vigor rating, a month after establishment I. Fine-tune and be creative. Odds are, you • periodic height and ground cover estimates, won’t be completely satisfied with one or more before killing or mowing details of your “best” cover. You might need to • periodic weed assessments sacrifice some potential benefits to make a cover • a biomass or yield rating work better in your farm system. For example, killing a cover earlier than you’d like will reduce Also rate residue before planting the next crop. the amount of biomass or N it provides, but could Rate survival of winter annuals in early spring as ensure that you plant summer crops on time. In they break dormancy and begin to grow. If you most cases, fine-tuning your management also plan to mow-kill an annual, log an approximate makes it more affordable. Lowering a seeding rate flowering date. Regrowth could occur if most of or shifting the seeding date also could reduce the the crop is still vegetative. Rate overall weather tillage needed. Narrower rows in your cash crop and record dates such as first frost. Note anything might hinder establishment of an overseeded you think has a bearing on the outcome, such as legume but reduce weeds and bump up the cash weed infestations. If time allows, try killing the crop yield. Don’t expect all of a cover’s benefits cover crops and continuing your expected rota- to show up in yearly economic analyses. Some tion, at least on a small scale. You might need hand benefits are hard to assess in dollars. tools or a lawn mower. Use field markers to Your best covers may seem well-suited to your identify plots. farm, but there could be an up-and-com ing

190 MANAGING COVER CROPS PROFITABLY species or management technique you haven’t enough tips to start test ing cover crops. You also thought of testing. See Up-and-Coming Cover can collaborate with others in your region to pool Crops (p. 191) for a few examples. Overwhelmed? resources and share findings. There’s a good You needn’t be. Initiative and common sense— chance others in your area could benefit from traits you already rely on—are fundamental to any your cover cropping wisdom! on-farm testing program. As a grower, you already [Adapted and updated in 2006 from Northeast test varieties, planting dates and other manage- Cover Crop Handbook by Marianne Sarrantonio, ment practices every year. This section offers Rodale Institute, 1994.]

Appendix B UP-AND-COMING COVER CROPS

Balansa clover Trifolium balansae or Trifolium michelianum Identified as a promising new cover crop in subsp. balansae. A landrace of balansa clover col- screening trials throughout the Southeastern U.S., lected in Turkey in 1937 was released in 1952 by balansa clover (Trifolium michelianum Savi) is a the Alabama office of NRCS with the name MIKE. small-seeded annual legume with superior reseed- Small amounts of seed of this accession are avail- ing potential compared with other legumes, able from the Plant Introduction station in Athens, including crimson clover. Well-adapted to a wide GA. range of soil types, bal ansa performs particularly Balansa clover seed is quite small, so planting well on silty clay soil with a pH of about 6.5. only 5 lb./A gives a dense stand. Seed is produced Established stands tolerate waterlogging, moder- commercially only in Australia. Balansa clover ate salinity, and soil pH from 4.5 to 8.0. It does not requires a relatively rare inoculant, desig nated do well on highly alkaline soils (30). It is consid- “Trifolium Special #2” by Liphatech, Inc., manu- ered marginal in Zone 6B. facturer of “Nitragin” brand inoculants. Kamprath Balansa and other reseeding legumes were Seed Co. imports balansa seed (See Seed screened in Zones 6, 7, and 8 (from the Gulf Coast Suppliers, p. 195). Some seed suppliers offer coat- to northern Tennessee, and from Georgia to west- ed seed that is pre-inoculated. The price per ern Arkansas). TIBBEE crimson clover (Trifolium pound of coated seed is about the same as bare 1 incarnatum) was used as a phenological check. seed, but /3 of the weight is coating so the seed- Growth was terminated 2 to 3 weeks after TIBBEE ing rate for coated seed should be increased to 8 bloomed at each location to identify adapted lb./A. cover crops that reseed earlier than TIBBEE. PARADANA is the cultivar that has been most Spotted burclover (Medicago arabica) and bal- widely tested in the U.S. It was released in 1985 ansa clover were the best reseeding legumes that by the South Australia Department of Agriculture. were hardy throughout zone 7A. Of these, only It was derived from Turkish introductions crossed balansa clover is commercially available. and tested at Kangaroo Island, NSW, Australia. Balansa clover is open pollinated. Flowers vary Seed yields over 550 lb./A have been obtained. from white to pink and are attractive to bees. BOLTA is 1-2 weeks later than PARADANA and Ungrazed, it grows up to three feet high and produces FRONTIER is 2-3 weeks earlier. FRONTIER, a selection thick hollow stems that are palatable and of good feed out of PARADANA, has replaced its parent in the value. It becomes more prostrate when grazed. seed trade in recent years. Balansa clover was named Trifolium miche- While PARADANA seed matures slightly earlier lianum Savi in 1798. It is sometimes called than crimson clover, it often does not produce as

UP-AND-COMING COVER CROPS 191 much biomass. Nitrogen accumulation in above bet ter than rye, important for nitrogen manage- ground biomass is about 60 lb./A at full bloom. ment in conservation tillage systems. It breaks dis- Balansa can reseed for sever al years from a single ease cycles for wheat and soybean and is resistant seed crop, due to its relatively high amount of to root-knot nematodes. It is very resistant to rusts hard seed. It reseeded for four years fol lowing and has excep tional allelopathic activity for weed maturation of a seed crop in 1993 in Senatobia, control. It is easy to kill mechanically. Miss., and for at least two years in no-till systems Black oat is adapted for use as a winter cover at several other locations in Alabama, Georgia and crop in the lower Coastal Plain of the USA, includ- Mississippi. Neither TIBBEE nor AU ROBIN crimson ing Zones 8b-10a. It has done well in fall plantings clover reseeded for more than one year at any in Zone 8b, but winterkilled one year of six at location in those tests. Balansa clover does not some locations within this zone, dependent on reseed well after tillage, probably because the planting date. small seeds are buried too deeply. Planting dates are similar to common oat. If Allowing balansa clover to grow for 40 days planted too early, it is more susceptible to win- past first bloom every 3 to 4 years will allow terkill and lodging. Planting in late winter (early stands to persist indefinitely in no-till systems. February) yielded good biomass and ground Reseeded stands are denser, bloom 5 to 7 days ear- cover for late planted cash crops in the lower lier, and are more productive than planted stands Coastal Plain. because growth begins as soon as conditions are Seed 50-70 lb./A for use as a cover crop, 40 favorable and seedling density is higher. However, lb./A for seed production. In the Southeast, fall seed cost is minor compared to opportunity cost plantings (November) result in seed ripening in and risk associated with delaying main crop plant- mid May through early June. Seed yields range ing. Waiting past the optimum planting date to from 800 to 1400 lb./A. Seed is available commer- encourage reseeding is only practical in rotations cially in limited amounts. that include main crops optimally planted in May One cultivar, SOILSAVER, was selected for in the Southeastern U.S. increased cold tolerance and released by Auburn Balansa is less likely than crimson clovers to University and IAPAR (Institute of Agronomy of host root-knot nematodes (Meloidogyne incog - Paraná, Brazil). Auburn University and USDA-ARS nita, race 3). Gary Windham, USDA- ARS, Starkville, researchers developed it from a population of Miss., found that balansa had egg mass index IAPAR-61-IBIPORA, a public variety from the scores between 2.3 and 2.9. For comparison, a Institute of Agronomy of Parana, Brazil (IAPAR) very resistant white clover scored 1.5, most crim- and the Parananese Commission for Evaluation of son clovers score between 3 and 3.5 and very sus- Forages (CPAF). ceptible crops like REGAL white clover score 5 SOILSAVER black oat has several advantages as a on a scale from 1 to 5. cover crop. It tillers well, producing good soil cov- —Seth Dabney erage in relation to total biomass produced. It sup- USDA-ARS National Sedimentation Lab presses broadleaf weeds extremely well. In one P.O. Box 1157 Oxford, MS 38655-2900 study, weed control in conservation tillage cotton 662-232-2975; [email protected] (Gossypium hirsutum L.) averaged 34% with black oat compared to 26% for rye, 19% for wheat, Black oat and 16% with no cover crop. Black oat (Avena strigosa L.) is the No. 1 cover —D.W. Reeves crop on millions of acres of conservation-tilled Research Leader soybean in southern Brazil, and has potential for USDA-ARS, J. Phil Campbell Sr. Natural Resource use in the southern USA (Zones 8-10). Conservation Center Black oat produces large amounts of biomass, 1420 Experiment Station Road similar to rye. It maintains a narrower carbon to Watkinsville, GA 30677 nitrogen (C:N) ratio than rye so it cycles nitrogen

192 MANAGING COVER CROPS PROFITABLY 706-769-5631 ext. 203 white lupin and TIFBLUE-78 blue or narrow-leaf fax 706-769-8962 lupin were both released by USDA’s Agricultural [email protected] Research Service in the 1980s. These two varieties, and other modern varieties, are “sweet” Additional Information: types as opposed to “bitter” types that were wide- SoilSaver—A Black Oat Winter Cover Crop ly grown in the South prior to 1950. Sweet vari- for the Lower Southeastern Coastal Plain. 2002. eties have a low concentration of naturally USDA-ARS National Soil Dynamics Lab. occurring alkaloids. Sweet lupin is favored by Conservation Systems Fact Sheet No. 1. wildlife, especially deer. Sweet lupin cover crops www.ars.usda.gov/SP2UserFiles/Place/64200500 may act as a trap crop for thrips (Frankliniella /csr/FactSheets/FS01.pdf spp.) in cotton plantings, but this has yet to be confirmed by research. Lupin AU HOMER bitter white lupin is a new release by Lupins are cool-season annual legumes that pro- Auburn University derived from Tifwhite-78. It vide plenty of N and can be grown widely in the was selected for increased alkaloid content for USA and southern Canada. Lupins have aggressive use as a cover crop. Alkaloids make lupin seed taproots, especially the narrow-leaf cultivars. You and forage unpalatable for livestock, but also play can kill lupins mechanically or with herbi cides. a major role in resistance to disease, insects and Their hollow stems crush or break readily, making nematodes. it easy to plant cash crops using conser vation Lupins are susceptible to many fungal and viral tillage equipment. diseases and should not be grown in the same White lupin (Lupinus albus L.) and blue or nar- field in successive years. Rather, rotate lupin cover row-leaf lupin (Lupinus angustifolius L.) species crops with a small grain cover crop, ideally in a were originally named after their flower colors, rotation that allows three years between lupin but both species now have cultivars with white, plantings. Lupin are intolerant to poorly drained blue or magenta/purple flow ers. Blue lupin is soils. adapted to the lower Coastal Plain and is more readily identified by its narrow leaflets (about 0.5- For information about lupins and seed sources, inch wide) rather than flower color. contact: Edzard van Santen, Professor Crop As a fall and winter cover crop in the southeast - Science, Agronomy & Soils Dept., 202 Funchess ern USA, white lupin is the most cold-tolerant. Hall, Auburn University, Auburn, AL 36849; Some cultivars overwinter as far north as the 334-844-3975; fax 334-887-3945 Tennessee Valley. They typically produce 100 to [email protected] 150 lb. N/A when fall-planted and killed in early spring. Sunn Hemp Seed spring cultivars in early April in the north- A tropical legume, sunn hemp (Crotalaria juncea ern U.S. and southern Canada. Kill in June when L.) can produce more than 5,000 lb. dry matter/A they’re at peak biomass (early-bloom to early-pod and 120 lb. N/A in just nine to 12 weeks. It can fill stage). a narrow niche between harvest of a summer For use as a cover crop, drill lupins no deeper crop and planting of a fall cash or cover crop and than 1 inch at 70 lb./A for small-seeded blue vari- is especially fitted to vegetable production. Sunn eties to 120 lb./A for larg er-seeded white varieties. hemp sown by September 1 following a corn At $30 to $40 per acre, the seed is relatively crop in Alabama, for example, can produce an expensive. Be sure to inocu late lupin seed with average of 115 lb. N/A by December 1. compatible rhizobia. Sunn hemp is not winter hardy and a hard Three winter-hardy lupin cultivars are readily freeze easily kills it. Sow sunn hemp a minimum available on a commercial scale. TIFWHITE-78 of nine weeks before the average date of the first

UP-AND-COMING COVER CROPS 193 fall freeze. Seed at 40 to 50 lb./A, with a cowpea- A management caution: Many Crotalaria type inoculant. species contain alkaloids that are poisonous to Sunn hemp seed is expensive, about $2.25/lb., livestock. However, the sunn hemp variety TROPIC so the cost may be prohibitive for large-scale SUN, developed jointly by the University of Hawaii plantings. Seed can be produced only in tropical and USDA-NRCS, has a very low level of alkaloid areas, such as Hawaii, and currently is imported and is suitable for use as a forage. only by specialty seed companies. Research suggests that sunn hemp is resistant and/or suppressive to root-knot (Meloidogyne A New Alternative for South Florida spp.) and reniform (Rotylenchulus reniformis) Producers nematodes. A study by the NRCS Plant Materials Center —D.Wayne Reeves (see p. 192) (PMC) in Brooksville, Florida, concluded that sunn hemp seed can be a viable alternative cash crop Additional Information: for southern Florida growers. Sunn hemp is an Mansoer, Z., D.W. Reeves and C.W. Wood. 1997. annual legume that suppresses some types of Suitability of sunn hemp as an alternative nematodes and can produce over 5,000 pounds late-summer legume cover crop. of biomass and 100 pounds of nitrogen per acre Soil Sci. Soc. Am. J. 61:246-253. within a few months. Because of its potential use in alternative pest management systems and as a Balkcom, K. and D.W. Reeves. 2005. Sunn sustainable biological source of nitrogen, sunn hemp utilized as a legume cover crop for corn hemp is a promising cover crop for rotation with production. Agron. J. 97:26-31. vegetables throughout the Southeastern U.S. Unfortunately, its use has been limited by the Sunn Hemp: A Cover Crop for Southern and high seed cost—most is shipped from Hawaii as Tropical Farming Systems. USDA-NRCS Soil seed production requires a tropical climate. Two Quality Technical Note No. 10. May 1999. years ago, the NRCS PMC in Brooksville initiated Available at: http://soils.usda.gov/sqi/files a study to determine which zones in Florida /10d3.pdf could most economically produce sunn hemp seed. Seed was distributed to 15 growers through- K.-H. Wang and R. McSorley. Management of out Florida and although many locations lost their Nematodes and Soil Fertility with Sunn Hemp crop to frost, sunn hemp stands in coastal coun- Cover Crop. 2004. University of Florida ties below the 27th parallel consistently pro- Cooperative Extension. Publication #ENY-717. duced up to 370 pounds of seed per acre. http://edis.ifas.ufl.edu/NG043 Growers in more southern areas, such as Homestead, obtained even higher yields. Valenzuela, H. and J. Smith. 2002. ‘Tropic Sun’ Your contact is Clarence Maura, Manager, Sunnhemp. University of Hawaii Cooperative NRCS Brookville Plant Materials Center, at Extension. Publication #SA-GM-11. 352-796-9600 or [email protected]. www.ctahr.hawaii.edu/sustainag/GreenManures/ tropicsunnhemp.asp

194 MANAGING COVER CROPS PROFITABLY Appendix C SEED SUPPLIERS

This list is for information purposes only. Inclusion does not A.L. Gilbert—Farmers Warehouse imply endorsement, nor is criticism implied of firms not mentioned. 4367 Jessup Rd. Ceres, CA 95307 800-400-6377 or 209-632-2333 Adams-Briscoe Seed Co. [email protected] P.O. Box 19 www.farmerswarehouse.com 325 E. Second St. forage, grass, clovers, alfalfa, pasture Jackson, GA 30233-0019 770-775-7826 Ampac Seed Co. fax 770-775-7122 P.O. Box 318 [email protected] Tangent, OR 97389 www.abseed.com 800-547-3230 clovers, winter peas, vetches, cowpeas, wheat, fax 541-928-2430 rye, oats, grasses, sorghums, legume inoculants [email protected] http://ampacseed.com Agassiz Seed & Supply forage grasses, legumes, annual ryegrass, turnip, 445 7th St. NW rapeseed West Fargo, ND 58078 701-282-8118 Barenbrug fax 701-282-9119 33477 Hwy. 99 East www.agassizseed.com Tangent, OR 97389 sorghum, sudangrass, millet, ryegrass, clovers, 541-926-5801 or 800-547-4101 oats, wheat, vetch, legume inoculants fax 541-926-9435 forage legumes, grasses Agriliance-AFC, LLC. P.O. Box 2207 The Birkett Mills 905 Market St. Transloading Facility Decatur, AL 35609 North Ave. 256-560-2848 Penn Yan, NY 14527 fax 256-308-5693 315-536-2594 [email protected] [email protected] www.agri-afc.com www.thebirkettmills.com native grasses, wheat, rye, winter peas, vetch buckwheat Albright Seed Company Byron Seeds, LLC 6155 Carpinteria Ave. 9820 N. 750 E. Carpinteria, CA 93013-3061 Marshall, IN 47859 805-684-0436 765-435-7243 fax 805-684-2798 fax 765-435-2759 [email protected] cover crops, small grains, legumes, grasses www.SSSeeds.com Specializing in native California summer dormant perennial grasses & wild flowers, handles all seeds used in western cover crops

SEED SUPPLIERS 195 Cache River Valley Seed, LLC DLF Organic Hwy. 226 East P.O. Box 229 Cash, AR 72421 175 West H St. 870-477-5427 Halsey, OR 97348 [email protected] 800-445-2251 www.crvseed.com [email protected] wheat, oats www.dlforganic.com red/white clover, forage peas, organic cover crop Cal/West Seeds mix P.O. Box 1428 Woodland, CA 95776-1428 Doebler’s Pennsylvania Hybrids, Inc. 800-824-8585 202 Tiadaghton Ave. fax 530-666-5317 Jersey Shore, PA 17740 [email protected] 800-853-2676 or 570-753-3210 www.calwestseeds.com fax 570-753-5302 clovers, alfalfa, sudangrass, sorghum [email protected] www.doeblers.com Cedar Meadow Farm clovers, grasses, legume inoculants 679 Hilldale Rd. Holtwood PA 17532 Elk Mound Seed Company 717-575-6778 308 Railroad Street fax 717-284-5967 Elk Mound, WI 54739 [email protected] 800-401-SEED (7333) or 715-879-5556 www.cedarmeadowfarm.com fax 715-879-5057 forage radish, hairy vetch [email protected] www.elkmoundseed.com The CISCO Companies Oats, barley, wheat, rye, ryegrass, legumes, daikon 602 N. Shortridge Rd. radish, buckwheat, brassicas, forage grasses Indianapolis, IN 46219 800-888-2986 ext. 319 Ernst Conservation Seeds fax 317-357-7572 9006 Mercer Pike www.ciscoseeds.com/nvest.php Meadville, PA 16335 N-Vest cover crop mixes, annual ryegrasses, 800-873-3321 clovers, winter peas, radishes, turnips, vetches, fax 814-336-5191 cowpeas, wheat, rye, oats, winter barley, triticale, [email protected] grasses, sorghums, legume inoculants and more www.ernstseed.com oats, clovers, buckwheat, ryegrass, alfalfa, barley, Discount Seeds winter peas, rye, wheat, hairy vetch, Japanese P.O. Box 84 millet, foxtail millet 2411 9th Ave SW Watertown, SD 57201 Fedco Seeds 605-886-5888 P.O. Box 520 fax 605-886-3623 Waterville, ME 04903 grains, forage/grain legumes, forage grasses 207-873-7333 fax 207-872-8317 www.fedcoseeds.com grains, forage/grain legumes, grasses, clovers, legume inoculants

196 MANAGING COVER CROPS PROFITABLY Genesee Union Warehouse Johnny’s Selected Seeds P.O. Box 67 955 Benton Ave. Genesee, ID 83832 Winslow, ME 04901 208-285-1141 877-564-6697 fax 208-285-1716 fax 800-738-6314 www.geneseeunion.coop [email protected] Oriental mustard, winter peas www.johnnyseeds.com buckwheat, rye, oats, wheat, vetch, clover, field Harmony Farm Supply & Nursery peas, green manure mix, sudangrass, inoculants 3244 Hwy. 116 North Sebastopol, CA 95472 Kamprath Seeds, Inc. 707-823-9125 205 Stockton St. fax 707-823-1734 Manteca, CA 95337 [email protected] 209-823-6242 www.harmonyfarm.com fax 209-823-2582 clovers, grains, grasses, legumes, legume vetches, bell beans, small grains, brassicas, subterranean clovers, balansa clover, medics, High Mowing Seeds perennial clovers, grasses 76 Quarry Rd. Wolcott, VT 05680 Kaufman Seeds, Inc. 802-472-6174 P.O. Box 398 fax 802-472-3201 Ashdown, AR 71822 www.highmowingseeds.com 870-898-3328 or 800-892-1082 buckwheat, vetch, oats, rye, peas, clover, legume fax 870-898-3302 [email protected] Hobbs & Hopkins Ltd. wholesale grains, forage/grain legumes, grasses, 1712 SE Ankeny St. summer annuals, sunn hemp Portland, OR 97214 503-239-7518 Keystone Group Ag. Seeds fax 503-230-0391 RR 1 Box 81A [email protected] Leiser Rd. www.protimelawnseed.com New Columbia, PA 17856 grasses 570-538-1170 alfalfa, forages, forage radish Horstdale Farm Supply 12286 Hollowell Church Rd. King’s Agriseeds, LLC Greencastle, PA 17225-9525 96 Paradise Ln. 717-597-5151 Ronks, PA 17572 fax 717-597-5185 717-687-6224 or 866-687-6224 barley, wheat, rye, oats, crimson clover, winter forage radish, forages, alfalfa, clovers vetch Little Britain AgriSupply Inc. Hytest Seeds 398 North Little Britain Rd. 2827 8th Ave. South Quarryville, PA 17566 Fort Dodge, IA 50501 717-529-2196 800-442-7391 [email protected] [email protected] oats, barley, wheat, rye, triticale, intermediate rye- www.hytestseeds.com grass, perennial ryegrass, annual ryegrass, red alfalfa clover, sorghum & sudangrass (other cover crops available by special order)

SEED SUPPLIERS 197 Michigan State Seed Solutions Plantation Seed Conditioners, Inc. 717 N. Clinton St. P.O. Box 398 Grand Ledge, MI 48837 Newton, GA 39870 517-627-2164 229-734-5466 [email protected] fax 229-734-7419 www.seedsolutions.com lupin, rye, black oats forgage/grain legumes, grains, grasses P.L. Rohrer & Bro. Inc. Missouri Southern Seed Corp. P.O. Box 250 P.O. Box 699 Smoketown, PA 17576 Rolla, MO 65402 717-299-2571 573-364-1336 or 800-844-1336 fax 717-299-5347 fax 573-364-5963 [email protected] wholesale (w/retail outlets): grains, forage www.rohrerseeds.com legumes, grasses, summer annuals grains, clovers, grasses, brassicas, vetch, rye, wildlife mix Moore Seed Farm, LLC 8636 N. Upton Rd. Rupp Seeds, Inc. Elsie, MI 48831 17919 County Rd. B 989-862-4686 Wauseon, OH 43567 rye 877-591-7333 fax 419-337-5491 North Country Organics [email protected] P.O. Box 372 www.ruppseeds.com Bradford,VT 05033 grains, grasses, forage legumes, vetch 802-222-4277 fax 802-222-9661 Seed Solutions [email protected] 2901 Packers Ave. www.norganics.com Madison,WI 53707 buckwheat, ryegrass, oats, rye, wheat 800-356-7333 fax 608-249-0695 Peaceful Valley Farm & Garden Supply [email protected] 125 Clydesdale Ct. www.foragefirst.com P.O. Box 2209 oats, wheat, rye, hairy vetch, sweetclover, Grass Valley, CA 95945 berseem clover, red clover, crimson clover, forage 888-784-1722 peas, cowpeas, ryegrass, buckwheat, millets, fax 530-272-4794 sorghum, sorghum-sudangrass, cover crop mixes [email protected] www.groworganic.com Seedway, LLC. clovers, grasses, legumes, grains, vetches, custom P.O. Box 250 cover crop mixes, legume inoculants Hall, NY 14463 800-836-3710 Pennington Seeds fax 585-526-6391 P.O. Box 290 [email protected] Madison, GA 30650 www.seedway.com 800-285-7333 ryegrass, orchardgrass, clover [email protected] www.penningtonseed.com grains, grasses, forage legumes

198 MANAGING COVER CROPS PROFITABLY Siemer/Mangelsdorf Seed Co. The Wax Co., Inc. 515 West Main St. 212 Front St. N. P.O. Box 580 Amory, MS 38821 Teutopolis, IL 62401 662-256-3511 217-857-3171 annual ryegrass, forages fax 217-857-3226 [email protected] Welter Seed & Honey Co. 17724 Hwy. 136 www.siemerent.com Onslow, IA 52321-7549 grasses, vetch, wildlife 800-728-8450 or 800-470-3325 Southern States Cooperative, Inc. fax 563-485-2764 P.O. Box 26234 [email protected] Richmond, VA 23260-6234 www.welterseed.com 800-868-6273 oats, brassicas, rye, spring wheat, winter wheat, wholesale (retail outlets in 6 states): grains, buckwheat, hairy vetch, sweet clovers, alfalfa, a forage legumes, cowpeas, summer annuals, wide variety of other seeds, legume inoculants rapeseed, clover, buckwheat, rye Wolf River Valley Seeds Sweeney Seed Company N2976 County Hwy M 110 South Washington St. White Lake, WI 54491 Mount Pleasant, MI 48858 800-359-2480 989-773-5391 fax 715-882-4405 grasses, forages, legumes [email protected] www.wolfrivervalleyseeds.com Talbot Ag Supply clover, brassicas, grasses, annual forage, grain, P.O. Box 2252 legume inoculants Easton, MD 21601-8944 410-820-2388 INOCULANT SUPPLIERS [email protected] Many of the seed suppliers listed above sell inoculated seed wheat, barley, rapeseed, rye and/or legume inoculants. Tennessee Farmers Co-op 200 Waldron Rd. Becker Underwood 801 Dayton Ave. P.O. Box 3003 Annes, IA 50010 LaVergne, TN 37086-1983 800-232-5907 615-793-8400 [email protected] [email protected] www.beckerunderwood.com www.ourcoop.com alfalfa, grains, clover, grasses, legume inoculants HiStick 801 Dayton Ave. Timeless Seeds, Inc. Ames, IA 50010 166 Sunrise Ln. 800-892-2013 P.O. Box 881 www.histick.com Conrad, MT 59425 click ‘Where to Buy’ for dealer locations 406-278-5722 fax 406-278-5720 LiphaTech Inc. (Nitragin division) [email protected] Manufacturer of Nitragin inoculant. http://timelessfood.com www.nitragin.com dryland forage/grain legumes click ‘Recommended Links’ at bottom of page.

SEED SUPPLIERS 199 Appendix D FARMING ORGANIZATIONS WITH COVER CROP EXPERTISE

This list is for information purposes only. Inclusion does not SARE Northeast Region Office imply endorsement, nor is criticism implied of organizations not mentioned. Note: CC denotes cover crop(s) or cover crop- University of Vermont ping. 655 Spear St. Burlington,VT 05405-0107 802-656-0471 ORGANIZATIONS—NORTHEAST fax 802-656-0500 The Accokeek Foundation [email protected] 3400 Bryan Point Rd. www.nesare.org Accokeek, MD 20607 301-283-2113 ORGANIZATIONS—NORTH CENTRAL fax 301-283-2049 Center for Integrated Agricultural Systems [email protected] (CIAS) www.accokeek.org University of Wisconsin-Madison land stewardship & ecological agriculture 1535 Observatory Dr. using CC Madison,WI 53706 Chesapeake Wildlife Heritage 608-262-5200 P.O. Box 1745 fax 608-265-3020 Easton, MD 21601 [email protected] 410-822-5100 www.cias.wisc.edu fax 410-822-4016 CC for fresh market vegetable production; rele- [email protected] vant publication “Grower to grower: Creating a www.cheswildlife.org livelihood on a fresh market vegetable farm” CC in organic & sustainable farming systems; available on website. consulting & implementation in mid-shore Md Conservation Technology Information area as they relate to farming & wildlife Center (CTIC) Pennsylvania Association for Sustainable 1220 Potter Dr. Agriculture (PASA) West Lafayette, IN 47906 P.O. Box 419 765-494-9555 114 W. Main St. fax 765-494-5969 Millheim, PA 16854 [email protected] 814-349-9856 www.conservationinformation.org fax 814-349-9840 CTIC is a trusted, reliable source for information [email protected] & technology about conservation in agriculture www.pasafarming.org on farm CC demonstrations

200 MANAGING COVER CROPS PROFITABLY Leopold Center for Sustainable Agriculture Educational Concerns for Hunger Iowa State University Organization 209 Curtiss Hall ECHO Ames, IA 50011-1050 17391 Durrance Rd. 515-294-3711 North Ft. Myers, FL 33917 fax 515-294-9696 239-543-3246 [email protected] fax 239-543-5317 www.ag.iastate.edu/centers/leopold [email protected] support research, demos, education projects in www.echonet.org Iowa on CC systems provides technical information & seeds of tropical cover crops; maintains demonstration Northern Plains Sustainable Agriculture plots on the farm of many of the most important Society tropical cover crops. P.O. Box 194, 100 1 Ave. SW Lamoure, ND 58458-0194 The Kerr Center for Sustainable 701-883-4304 Agriculture Inc. fax 701-883-4304 P.O. Box 588 [email protected] Highway 271 South www.npsas.org Poteau, OK 74953 CC systems for organic/sustainable farmers 918-647-9123 fax 918-647-8712 SARE North Central Region Office [email protected] University of Minnesota www.kerrcenter.com 120 Bio. Ag. Eng. CC systems demonstrations & research 1390 Eckles Ave. St. Paul, MN 55108 SARE Southern Region Office 612-626-3113 University of Georgia fax 612-626-3132 1109 Experiment St. [email protected] Room 207, Stuckey Building www.northcentralsare.org Griffin, GA 30223-1731 770-412-4786 ORGANIZATIONS—SOUTH fax 770-412-4789 [email protected] Appropriate Technology Transfer for Rural www.southernsare.org Areas (ATTRA) P.O. Box 3657 Texas Organic Growers Association Fayetteville, AR 72702 P.O. Box 15211 800-346-9140 Austin,TX 78761 http://attra.ncat.org/ 877-326-5175 ATTRA is a leading information source for fax 512-842-1293 farmers & extension agents thinking about [email protected] sustainable farming practices www.tofga.org TOGA is helping to make organic agriculture viable in Texas & offers a quarterly periodical.

ORGANIZATIONS 201 ORGANIZATIONS—WEST Small Farm Center University of California Center for Agroecology & Sustainable Food One Shields Ave. Systems Davis, CA 95616 University of California 530-752-8136 1156 High St. fax 530-752-7716 Santa Cruz, CA 95064 [email protected] 831-459-3240 www.sfc.ucdavis.edu fax 831-459-2799 serves as a clearinghouse for questions from [email protected] farmers, marketers, farm advisors, trade associa - www.ucsc.edu/casfs tions, government officials & agencies, & the aca- Facilitates the training of organic farmers demic community & gardeners, with practical hands-on & academic training University of California SAREP One Shields Ave. SARE Western Region Office Davis, CA 95616-8716 Utah State University 530-752-7556 4865 Old Main Hill fax 530-754-8550 Room 322 [email protected] Logan, UT 84322-4865 www.sarep.ucdavis.edu 435-797-2257 [email protected] www.westernsare.org

Appendix E REGIONAL EXPERTS

These individuals are willing to briefly respond to specific Jim Crawford questions in their area of expertise, or to provide referral to New Morning Farm others in the sustainable agriculture field. Please respect their schedules and limited ability to respond. Note: CC 22263 Anderson Hollow Rd. denotes cover crop(s) or cover cropping. Hustontown, PA 17229 814-448-3904 fax 814-448-2295 NORTHEAST [email protected] Andy Clark www.newmorningfarm.net SARE Outreach 35 years of CC for vegetable production 1122 Patapsco Building University of Maryland College Park, MD 20742-6715 301-405-2689 fax 301-405-7711 [email protected] www.sare.org technical information specialist for sustainable agriculture; legume/grass CC mixtures

202 MANAGING COVER CROPS PROFITABLY Eric Gallandt Stephen Herbert Weed Ecology & Management University of Massachusetts Dept. of Plant, Soil & Environmental Sciences Dept. of Plant Soil Insect Sciences University of Maine Bowditch Hall 5722 Deering Hall Amherst, MA 01003 Orono, ME 04469 413-545-2250 207-581-2933 fax 413-545-0260 [email protected] [email protected] www.umaine.edu/weedecology/ www.umass.edu/cdl CC & weed management CC culture, soil fertility, crop nutrition & management & nitrate leaching Steve Groff Cedar Meadow Farm Jeff Moyer 679 Hilldale Rd. The Rodale Institute Holtwood, PA 17532 611 Siegfriedale Rd. 717-284-5152 Kutztown, PA 19530 fax 717-284-5967 610-683-1420 [email protected] fax 610-683-8548 www.cedarmeadowfarm.com [email protected] CC/no-till strategies for vegetable & agronomic crops www.newfarm.org CC management in biologically based no-till Vern Grubinger systems, CC in grain crop rotations, CC as a University of Vermont Extension weed management tool, rolling CC 11 University Way Brattleboro, VT 05301-3669 Jack Meisinger 802-257-7967 ext. 13 USDA/ARS [email protected] BARC-East www.uvm.edu/vtvegandberry/Videos/ Bldg. 163F Rm 6 covercropvideo.html 10300 Baltimore Ave vegetable & berry specialist Beltsville, MD 20705 301-504-5276 H.G. Haskell III [email protected] 4317 S. Creek Rd. nitrogen management in CC systems Chadds Ford, PA 19317 tel/fax 610-388-0656 Anne & Eric Nordell cell 610-715-7688 3410 Rte. 184 [email protected] Trout Run, PA 17771 rye/vetch mix for green manure & erosion 570-634-3197 control; uses winter rye CC on all land; 70% no-till rotational CC for weed control Zane R. Helsel Marianne Sarrantonio Rutgers Cooperative Extension University of Maine 88 Lipman Dr. Dept. of Plant, Soil & Environmental Science 313 Martin Hall 5722 Deering Hall New Brunswick, NJ 08901-8525 Orono, ME 04473 732-932-5000 x585 207-581-2913 fax 732-932-6633 fax 207-581-2999 [email protected] [email protected] www.rce.rutgers.edu effects of CC on nutrient cycling & soil quality CC in field crops in diverse cropping systems

REGIONAL EXPERTS 203 Eric Sideman NORTH-CENTRAL Maine Organic Farmers & Gardeners Assoc. P.O. Box 1760 Rich Bennett 13 Lakeview Dr. Unity, ME 04988 Napoleon, OH 43545 207-946-4402 419-592-1100 fax 207-568-4141 [email protected] [email protected] CC for soil quality & herbicide/pesticide reduc tion www.mofga.org CC in rotation with vegetables & small fruit on John Cardina organic farms Ohio State University Dept. of Horticulture & Crop Science John R. Teasdale 1680 Madison Ave. USDA/ARS Wooster, OH 44691 BARC-West 330-263-3644 Bldg. 001 Rm 245 fax 330-263-3887 10300 Baltimore Ave [email protected] Beltsville, MD 20705 CC for no-till corn & soybeans 301-504-5504 fax 301-504-6491 Stephan A. Ebelhar [email protected] University of Illinois, Dept. of Crop Sciences CC mgmt./weed mgmt. using CC Dixon Springs Agricultural Center Rte. 1, Box 256 Donald Weber Simpson, IL 62985 Research Entomologist 618-695-2790 Insect Biocontrol Laboratory fax 618-695-2492 10300 Baltimore Ave. [email protected] Bldg. 011A, Rm. 107 www.cropsci.uiuc.edu/research/rdc/dixon- BARC-West springs Beltsville, MD 20705 CC for no-till corn & soybeans 301-504-8369 fax 301-504-5104 Rick (Derrick N.) Exner, Ph.D. [email protected] Iowa State University Extension CC & pest management (vegetable crops only) Practical Farmers of Iowa 2104 Agronomy Hall, ISU David W. Wolfe Ames, IA 50011 Cornell University 515-294-5486 Dept. of Horticulture fax 515-294-9985 168 Plant Science Bldg. [email protected] Ithaca, NY 14853 www.practicalfarmers.org 607-255-7888 on farm CC research for the upper Midwest fax 607-255-0599 [email protected] www.hort.cornell.edu/wolfe CC for improved soil quality in vegetables

204 MANAGING COVER CROPS PROFITABLY Carmen M. Fernholz Todd Martin 2484 Hwy 40 MSU Kellogg Biological Station Madison, MN 56256 Land & Water Program 320-598-3010 3700 E. Gull Lake Dr. fax 320-598-3010 Hickory Corners, MI 49060 [email protected] 269-671-2412 ext. 226 minimum tillage, general cover crops, seeding fax 269-671-4485 soybeans into standing rye [email protected] www.covercrops.msu.edu Walter Goldstein CC for corn, soybeans, vegetables, blueberries in Michael Fields Agricultural Institute Michigan P.O. Box 990 East Troy, WI 53120 Paul Mugge 262-642-3303 ext. 112 6190 470th St. fax 262-642-4028 Sutherland, IA 51058-7544 [email protected] 712-446-2414 www.michaelfieldsaginst.org [email protected] CC for nutrient cycling & soil health in Iowa farmer using CC for corn & soybeans biody namic, organic & conventional systems Dale R. Mutch Frederick Kirschenmann MSU Kellogg Biological Station 3703 Woodland Land & Water Program Ames, IA 50014 3700 E. Gull Lake Dr. 515-294-3711 Hickory Corners, MI 49060 fax 515-294-9696 269-671-2412 ext. 224 [email protected] 800-521-2619 CC for cereal grains, soil quality & pest mgt. fax 269-671-4485 [email protected] Matt Liebman www.covercrops.msu.edu Iowa State University general CC information provider Dept. of Agronomy 3405 Agronomy Hall Rob Myers Ames, IA 50011-1010 North Central Region SARE 515-294-7486 University of Missouri fax 515-294-3163 238 Ag Engineering Bldg. [email protected] Columbia, MO 65211 www.agron.iastate.edu/personnel/userspage. 573-882-1547 aspx?id=646 fax 573-884-5650 CC for cropping system diversification, soil [email protected] amendments, weed ecology & management, www.northcentralsare.org crop rotation, green manures, intercrops, animal CC & crop diversification manures, composts, insects & rodents that consume weed seeds

REGIONAL EXPERTS 205 Sieg Snapp Nancy Creamer W.K. Kellogg Biological Station North Carolina State University Michigan State University Center for Environmental Farming Systems 3700 East Gull Lake Dr. Box 7609 Hickory Corners, MI 49060 Raleigh, NC 27695 fax 269-671-2104 919-515-9447 [email protected] fax 919-515-2505 www.kbs.msu.edu/faculty/snapp [email protected] using CC to enhance nitrogen fertilizer use effi- www.cefs.ncsu.edu ciency & nutrient cycling in row crops CC management for no-till organic vegetable production Richard Thompson Thompson On-Farm Research Seth Dabney 2035 190th St. USDA-ARS Boone, IA 50036-7423 National Sedimentation Laboratory 515-432-1560 P.O. Box 1157 [email protected] 598 McElroy Drive CC in corn-soybean-corn-oats-hay rotation Oxford, MS 38655 662-232-2975 SOUTH fax 662-232-2915 [email protected] Philip J. Bauer legume reseeding & mechanical control of CC USDA/ARS in the mid-South Cotton Production Research Center 2611 West Lucas St. Greg D. Hoyt Florence, SC 29501-1241 Dept. of Soil Science, NCSU 843-669-5203 x137 Mtn. Hort. Crops Res. & Ext. Center fax 843-662-3110 455 Research Dr. [email protected] Fletcher, NC 28732 CC for cotton production 828-684-3562 fax 828-684-8715 J.P. (Jim) Bostick, Ph.D. [email protected] Southern Seed Certification Assoc. CC for vegetables, tobacco & corn P.O. Box 357 Headland, AL 36345 D. Wayne Reeves 334-693-3988 Research Leader fax 334-693-2212 USDA/ARS [email protected] J. Phil Campbell Sr. Natural Resource specialty CC & seed development Conservation Center 1420 Experiment Station Rd. Watkinsville, GA 30677 706-769-5631 ext. 203 cell 706-296-9396 fax 706-769-8962 [email protected] CC management & conservation tillage for soybean, corn, cotton, peanut, & integrated grazing-row crop systems

206 MANAGING COVER CROPS PROFITABLY Kenneth H. Quesenberry Jorge A. Delgado University of Florida Soil Scientist P.O. Box 110500 Soil Plant Nutrient Research Unit Gainesville, FL 32611 USDA/ARS 352-392-1811 ex. 213 2150 Centre Avenue, Building D, Suite 100 fax 352-392-1840 Fort Collins, CO 80526 [email protected] [email protected]; forage legume CC in S.E. USA [email protected] CC in irrigated potato, vegetables and small grain Jac Varco systems Mississippi State University Plant & Soil Sciences Dept. Richard P. Dick Box 9555 Professor of Soil Microbial Ecology Dorman Hall, Room 117 Ohio State University Mississippi State, MS 39762 School of Environment & Natural Resources 662-325-2737 Columbus, OH 43210 fax 662-325-8742 614-247-7605 [email protected] fax 614-292-7432 CC & fertilizer/nutrient management for cotton [email protected] production nitrogen cycling & environmental applications of CC WEST Shiou Kuo Miguel A. Altieri Washington State University University of California at Berkeley Dept. of Crop & Soil Sciences 215 Mulford Hall 7612 Pioneer Way East Berkeley, CA 94720-3112 Puyallup,WA 98371-4998 510-642-9802 253-445-4573 fax 510-643-5438 fax 253-445-4569 [email protected] [email protected] http://nature.berkeley.edu/~agroeco3 CC & soil nitrogen accumulation & availability to CC to enhance biological pest control in corn peren nial systems John M. Luna Robert L. Bugg, Ph.D Oregon State University U.C. Sustainable Agriculture Research & Dept. of Horticulture Education Program 4107 Agricultural & Life Sciences Bldg. University of California at Davis Corvallis, OR 97331 One Shields Ave. 541-737-5430 Davis, CA 95616-8716 fax 541-737-3479 530-754-8549 [email protected] fax 530-754-8550 CC for integrated vegetable production & [email protected] agroecology www.sarep.ucdavis.edu CC selection, growth & IPM

REGIONAL EXPERTS 207 Dwain Meyer Fred Thomas North Dakota State University CERUS Consulting Loftsgard Hall, Room 470E 2119 Shoshone Ave. Extension Service Chico, CA 95926 Fargo, ND 58105 530-891-6958 701-231-8154 fax 530-891-5248 [email protected] [email protected] yellow blossom sweetclover specialist CC specialist for tree & vine crops, row crops, field crops, vegetable crops & summer CC Clara I. Nicholls University of California Dept. of Environmental Science Policy & Management Division of Insect Ecology 137 Hilgard Hall Berkeley, CA 94720 510-642-9802 fax 510-643-5438 [email protected] CC for biological control in vineyards

Appendix F CITATIONS BIBLIOGRAPHY

The publications cited in the text (in parentheses) are listed 5 Alabouvette, C., C. Olivain and C. Steinberg. here by reference number. 2006. Biological control of plant diseases: the European situation. European J. of Plant Path. 1 Abdul-Baki, A.A. et al. 1997. Broccoli produc- 114:329-341. tion in forage soybean and foxtail millet cover crop mulches. HortSci. 32:836-839. 6 Alger, J. 2006. Personal communication. Stanford, Mont. 2 Abdul-Baki, A.A. and J.R. Teasdale. 1993. A no-tillage tomato production system using hairy 7 Al-Sheikh, A. et al. 2005. Effects of potato-grain vetch and subterranean clover mulches. HortSci. rotations on soil erosion, carbon dynamics and 28:106-108. properties of rangeland sandy soils. J. Soil Tillage Res. 81:227-238. 3 Abdul-Baki, A.A. and J.R. Teasdale. 1997. Snap bean production in conventional tillage and in 8 American Forage and Grassland Council no-till hairy vetch mulch. HortSci. 32:1191-1193. National Fact Sheet Series. Subterranean clover. http://forages.orst.edu/main.cfm?PageID=33 4 Abdul-Baki, A.A. and J.R. Teasdale. 1997. Sustainable Production of Fresh-Market 9 Angers, D.A. 1992. Changes in soil aggregation Tomatoes and Other Summer Vegetables with and organic carbon under corn and alfalfa. Soil Organic Mulches. Farmers’ Bulletin No. 2279, Sci. Soc. Am. J. 56:1244-1249. USDA/ARS, Beltsville, Md. 23 pp. www.ars.usda.gov/is/np/tomatoes.html

208 MANAGING COVER CROPS PROFITABLY 10 ATTRA. 2006. Overview of Cover Crops and 20 Barker, K.R. 1996. Animal waste, winter cover Green Manures. ATTRA. Fayetteville, Ark. crops and biological antagonists for sustained http://attra.ncat.org/attra-pub/PDF/covercrop.pdf management of Columbia lance and other nematodes on cotton. SARE Project Report #LS95- 11 ATTRA. Where can I find information about 060.1. Southern Region SARE. Griffin, Ga. the mechanical roller-crimper used in no-till pro- www.sare.org/projects duction? http://attra.ncat.org/calendar/question.php/2006/05/08/p2221 21 Barnes, R.F. et al. 1995. Forages: The Science of Grassland Agriculture. 5th Edition. Iowa State 12 Arshad, M.A. and K.S. Gill. 1996. Crop produc - Univ. Press, Ames, Iowa. tion, weed growth and soil properties under three fallow and tillage systems. J. Sustain. Ag. 22 Bauer, P.J. et al. 1993. Cotton yield and fiber 8:65-81. quality response to green manures and nitrogen. Agron. J. 85:1019-1023. 13 Ashford, D.L. and D.W. Reeves, 2003. Use of a mechanical roller-crimper as an alternative kill 23 Bauer, P.J., J.J. Camberato and S.H. Roach. method for cover crops. Amer. J. Alt. Ag. 18:37-45. 1993. Cotton yield and fiber quality response to green manures and nitrogen. Agron. J. 85:1019- 14 Badaruddin, M. and D.W. Meyer. 1989. Water 1023 use by legumes and its effects on soil water status. Crop Sci. 29:1212-1216. 24 Bauer P.J. and D.W. Reeves. 1999. A comparison of winter cereal species and planting dates 15 Badaruddin, M. and D.W. Meyer. 1990. Green- as residue cover for cotton grown with conser- manure legume effects on soil nitrogen, grain vation tillage. Crop Sci. 39:1824–1830. yield, and nitrogen nutrition of wheat. Crop Sci. 30:819-825. 25 Baumhardt, R.L. and R.J. Lascano. 1996. Rain infiltration as affected by wheat residue amount 16 Bagegni, A.M. et al. 1994. Herbicides with and distribution in ridged tillage. Soil Sci. Soc. crop competition replace endophytic tall fescue Am. J. 60:1908-1913. (Festuca arundinacae). Weed Tech. 8:689-695. 26 Baumhardt, R.L. 2003. The Dust Bowl Era. In 17 Bailey, R.G. et al. 1994. Ecoregions and subre- B.A. Stewart and T.A. Howell (eds.) Encyclopedia gions of the United States (map).Washington, of Water Science, pp. 187-191. Marcel-Dekker, NY. DC: USDA Forest Service.1:7,500,000.With sup- plementary table of map unit descriptions, com- 27 Baumhardt, R.L. and R.L. Anderson. 2006. Crop piled and edited by W. H. McNab and R. G. Bailey. choices and rotation principles. In G.A. Peterson, www.fs.fed.us/land/ecosysmgmt/ecoreg1_home. P.W. Unger, and W.A. Payne (eds.) Dryland html Agriculture, 2nd ed. Agronomy Monograph No. 23. pp. 113-139. ASA, CSSA, and SSSA, Madison, 18 Ball, D.M. and R.A. Burdett. 1977. Alabama WI. Planting Guide for Forage Grasses. Alabama Cooperative Extension Service, Chart ANR 149. 28 Baumhardt, R.L. and R.J. Lascano. 1999. Water Auburn Univ., Auburn, Ala. budget and yield of dryland cotton intercropped with terminated winter wheat. Agron. J. 91:922- 19 Ball, D.M. and R.A. Burdett. 1977. Alabama 927. Planting Guide for Forage Legumes. Alabama Cooperative Extension Service, Chart ANR 150. 29 Baumhardt, R. L. and J. Salinas-Garcia. 2006. Auburn Univ., Auburn, Ala. Mexico and the US Southern Great Plains. In G.A. Peterson, P.W. Unger, and W.A. Payne (eds.) Dryland Agriculture, 2nd ed. Agronomy Monograph No. 23. pp. 341-364. ASA, CSSA, and SSSA, Madison, WI.

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BIBLIOGRAPHY 223 335 Price, A.J., D.W. Reeves and M.G. Patterson. 346 Reddy, K.N., M.A. Locke and C.T. Bryson. 2006. Evaluation of weed control provided by 1994. Foliar washoff and runoff losses of lacto- three winter cover cereals in conservation-tillage ben, norflurazon and fluemeteron under simulat- soybean. Renew. Agr. Food Sys. 21(3):159-164. ed conditions. J. Agric. Food Chem. 42:2338-2343. 336 Przepiorkowski, T. and S.F. Gorski. 1994. 347 Reeves, D.W. 1994. Cover crops and rota- Influence of rye (Secale cereale) plant residues tions. In J.L. Hatfield and B. A. Stewart (eds.). on germination and growth of three triazine- Advances in Soil Science: Crops Residue resistant and susceptible weeds. Weed Tech. Management. pp. 125172. Lewis Publishers, CRC 8:744-747. Press Inc., Boca Raton, FL. 337 Quesenberry, K.H., D.D. Baltensperger and 348 Reeves, D.W. and J.T. Touchton. 1994. Deep R.A. Dunn. 1986. Screening Trifolium spp. for tillage ahead of cover crop planting reduces soil response to Meloidogyne spp. Crop Sci. 26:61-64. compaction for following crop. p. 4. Alabama Agricultural Experimental Station Newsletter. 338 Quinlivan, B.J. et al. Medics, general. Univ. of Auburn, Ala. www.ars.usda.gov/SP2UserFiles/ Calif. SAREP Cover Crops Resource Page. Place/66120900/Reeves/Reeves_1991_Deep www.sarep.ucdavis.edu/ccrop Tillage.pdf 339 Ramey, B.E. et al. 2004. Biofilm formation in 349 Reeves, D.W., A.J. Price and M.G. Patterson. plant-microbe associations. Current Opinion in 2005. Evaluation of three winter cereals for weed Microbiol. 7:602-609. control in conservation-tillage non-transgenic 340 Rajalahti, R.M. and R.R. Bellinder. 1996. cotton. Weed Tech. 19:731-736. Potential of interseeded legume and cereal cover 350 Reynolds, M.O. et al. 1994. Intercropping crops to control weeds in potatoes. pp. 349-354. wheat and barley with N-fixing legume species: Proc. 10th Int. Conf. on Biology of Weeds, Dijon, A method for improving ground cover, N-use effi- France. ciency and productivity in low-input systems. 341 Rajalahti, R. and R.R. Bellinder. 1999. Time of J. Agric. Sci. 23:175-183. hilling and interseeding of cover crop influences 351 Rice, E.L. 1974. Allelopathy. Academic Press, weed control and potato yield. Weed Sci. 47:215- Inc. N.Y. 225. 352 Rife, C.L. and H. Zeinalib. 2003. Cold toler- 342 Ranells, N.N. and M.G. Wagger. 1993. Crimson ance in oilseed rape over varying acclimation clover management to enhance reseeding and durations. Crop Sci. 43:96-100. no-till corn grain production. Agron. J. 85:62-67. 353 Riga, E. et al. 2003. Green manure amend- 343 Ranells, N.N. and M.G. Wagger. 1996. ments and management of root knot nematodes Nitrogen release from grass and legume cover on potato in the Pacific Northwest of USA. crop monocultures and bicultures. Agron. J. Nematol. Monographs & Perspectives 2:151-158. 88:777-782. 354 Robertson, T. et al. 1991. Long-run impacts of 344 Ranells, N.N. and M.G. Wagger. 1997a. Grass- cover crops on yield, farm income, and nitrogen legume bicultures as winter annual cover crops. recycling. pp. 117-120. In W.L. Hargrove (ed.). Agron. J. 89:659-665. Cover Crops for Clean Water. Soil and Water 345 Ranells, N.H., and M.G. Wagger. 1997b. Winter Conservation Society. Ankeny, Iowa. annual grass–legume bicultures for efficient 355 Robinson, R.G. 1980. The Buckwheat Crop nitrogen management in no-till corn. Agric. in Minnesota. Station Bulletin 539.Agricultural Ecosyst. Environ. 65:23–32. Experiment Station, Univ. of Minnesota, St. Paul, Minn.

224 MANAGING COVER CROPS PROFITABLY 356 Rogiers, S.Y. et al. 2005. Effects of spray adju- 366 Schmidt, W.H., D.K. Myers and R.W. Van vants on grape (Vitis vinifera) berry microflora, Keuren. 2001. Value of legumes for plowdown epicuticular wax and susceptibility to infection nitrogen. Ohio State Univ Extension Fact by Botrytis cinerea. Australasian Plant Pathol. Sheet AGF-111-01. 34:221-228. http://ohioline.osu.edu/agf-fact/0111.html 357 Rothrock, C.S. 1995. Utilization of winter 367 Sholberg, P. et al. 2006. Fungicide and clay legume cover crops for pest and fertility manage - treatments for control of powdery mildew influ- ment in cotton. SARE Project Report #LS94-057. ence wine grape microflora. HortSci. 41:176-182. Southern Region SARE. Griffin, Ga. 368 Schomberg, H.H. et al. 2005. Enhancing sus- www.sare.org/projects tainability in cotton production through reduced 358 Roylance, H.B. and K.H.W. Klages. 1959. chemical inputs, cover crops and conservation Winter Wheat Production. Bulletin 314. College tillage. SARE Project Report #LS01-121. Southern of Agriculture, Univ. of Idaho, Moscow, Idaho. Region SARE. Griffin, Ga. www.sare.org/projects. 359 Saini, M., A.J. Price and E. van Santen. 2005. 369 Schonbeck, M. and R. DeGregorio. 1990. Winter weed suppression by winter cover crops Cover crops at a glance. The Natural Farmer, in a conservation-tillage corn and cotton rota- Fall-Winter 1990. tion. Proc. 27th Southern Conservation-Tillage 370 Scott, J.E. and L.A. Weston. 1991. Cole crop Conf. pp. 124-128. (Brassica oleracea) tolerance to Clomazone. 360 Sarrantonio, M. 1991. Methodologies for Weed Sci. 40:7-11. screening soil-improving legumes. Rodale 371 Shaffer, M.J. and J.A. Delgado. 2002. Essentials Institute. Kutztown, Pa. of a national nitrate leaching index assessment 361 Sarrantonio, M. 1994. Northeast Cover Crop tool. J. Soil and Water Conserv. 57:327-335. Handbook. Soil Health Series. Rodale Institute, 372 Shipley, P.R. et al.1992. Conserving residual Kutztown, Pa. corn fertilizer nitrogen with winter cover crops. 362 Sarrantonio, M. and E. Gallandt. 2003. The Agron. J. 84:869-876. role of cover crops in North American cropping 373 Sheaffer, C. 1996. Annual medics: new systems. J. of Crop Prod. 8:53-74. legumes for sustainable farming systems in the 363 Sarrantonio, M. and T.W. Scott. 1988. Tillage Midwest. SARE Project Report #LNC93-058. effects on availability of nitrogen to corn follow- North Central Region SARE. St. Paul, Minn. ing a winter green manure crop. Soil Sci. Soc. www.sare.org/projects Am. J. 52:1661-1668. 374 Sheaffer, C.C., S.R. Simmons and M.A. 364 Sattell, R. et al. 1999. Cover Crop Dry Matter Schmitt. 2001. Annual medic and berseem clover and Nitrogen Accumulation in Western Oregon. dry matter and nitrogen production in rotation Extension publication #EM 8739. Oregon State with corn. Agron. J. 93:1080-1086. Univ Extension. http://extension.oregonstate. 375 Shrestha, A. et al. 1996. “Annual Medics.” edu/catalog/html/em/em8739 In Cover Crops: MSU/KBS (factsheet packet). 365 Sattell, R. et al. 1998. Oregon cover crops: Michigan State Univ. Extension. East Lansing, rapeseed. http://extension.oregonstate.edu/cata- Mich. log/html/em/em8700 376 Shrestha, A. et al. 1998. Annual medics and berseem clover as emergency forages. Agron. J. 90:197-201.

BIBLIOGRAPHY 225 377 Sideman, E. 1991. Hairy vetch for fall cover and 388 Smith, R.F. et al. 2005. Mustard cover crops nitrogen: A report on trials by MOFGA in Maine. to optimize crop rotations for lettuce produc- Maine Organic Farmer & Gardener 18:43-44. tion. California lettuce research board. Annual Report. pp. 212-219. http://ucce.ucdavis.edu/ 378 Sims, J.R. 1980. “Seeding George black files/filelibrary/1598/29483.pdf medic,” “George black medic in rotation,” “George black medic as a green manure.” In Timeless 389 Smith, S.J and A.N. Sharpley. Sorghum and Seeds. Conrad, Mont. sudan grass. Univ. of Calif. SAREP Cover Crops Resource Page. www.sarep.ucdavis.edu/ccrop 379 Sims, J.R. 1982. Progress Report. Montana Ag. Extension Service. Research Project #382. 390 Snapp, S. et al. 2005. Evaluating cover crops Bozeman, Mont. for benefits, costs and performance within cropping system niches. Agron. J. 97:1-11. 380 Sims, J.R. 1988. Research on dryland legume-cereal rotations in Montana. Montana 391 Snapp, S. et al. 2006. Mustards—A Brassica State Univ. Bozeman, Mont. Cover Crop for Michigan. Extension Bulletin E-2956. Michigan State Univ. 381 Sims, J.R. et al. 1991. Yield and bloat haz ard of berseem clover and other forage legumes in 392 Snider, J. et al. 1994. Cover crop potential of Montana. Montana AgResearch 8:4-10. white clover: Morphological characteristics and persistence of thirty-six varieties. Mississippi 382 Sims, J.R. 1995. Low input legume/ cereal Agricultural and Forestry Experiment Service rotations for the northern Great Plains- Research Report 19:1-4. Intermountain Region dryland and irrigated systems. SARE Project Report #LW89-014. 393 Soil Science Society of America.1997. Western Region SARE. Logan, Utah. Glossary of soil science terms. Madison, WI. www.sare.org/projects 394 Stark, J.C. 1995. Development of sustainable 383 Sims, J. 1996. Beyond Summer Fallow. potato production systems for the Pacific NW. Prairie Salinity Network Workshop, June 6, 1996, SARE Project report #LW91-029. Western Region Conrad, Mont. Available from Montana Salinity SARE. Logan, Utah. www.sare.org/projects Control Association, Conrad, Mont. 59425. 395 Stiraker, R.J. et al. 1995. No-tillage vegetable 384 Singer, J.W., M.D. Casler and K.A. Kohler. production using cover crops and alley crop ping. 2006. Wheat effect on frost-seeded red clover pp. 466-474. In Soil Management in Sustainable cultivar establishment and yield. Agron. J. 98:265- Agriculture. Proc. Third Int’l Conf. on Sustainable 269. Agriculture. 31 August to 4 September 1993. Wye College, Univ of London, UK. 385 Singer, J.W. et al. 2004. Tillage and compost affect yield of corn, soybean, and wheat and soil 396 Stivers, L.J. and C. Shennan. 1991. Meeting fertility. Agron. J. 96:531-537. the nitrogen needs for processing tomatoes through winter cover cropping. J. Prod Ag. 386 Singer, J. and P. Pedersen. 2005. Legume 4:330-335. Living Mulches in Corn and Soybean. Iowa State Univ Extension Publication, Iowa State 397 Stoskopf, N.C. Barley. Univ. of Calif. SAREP Univ, Ames Iowa. http://extension.agron.iastate. Cover Crops Resource Page. edu/soybean/documents/PM_mulches_2006.pdf www.sarep.ucdavis.edu/ccrop 387 Singogo, W., W.J. Lamont Jr. and C.W. Marr. 398 Stute, J.K. 2007. Personal communica tion. 1996. Fall-planted cover crops support good Michael Fields Agricultural Institute. East Troy, Wis. yields of muskmelons. HortSci. 31:62-64.

226 MANAGING COVER CROPS PROFITABLY 399 Stute, J. 1996. Legume Cover Crops in 411 Teasdale, J.R. and C.L. Mohler. 1993. Light Wisconsin. Wisconsin Department of Agriculture, transmittance, soil temperature and soil moisture Sustainable Agriculture Program. Madison, Wis. under residue of hairy vetch and rye. Agron. J. 27 pp. 85:673-680. 400 Stute, J.K. and J.L. Posner. 1995a. Legume 412 Teasdale, J.R. 1996. Contribution of cover cover crops as a nitrogen source for corn in an crops to weed management in sustainable oat-corn rotation. J. Prod. Agric. 8:385-390. agri culture systems. J. Prod. Ag. 9:475-479. 401 Stute, J.K. and J.L. Posner. 1995b. Synchrony 413 Temple, S. 1996. A comparison of con - between legume nitrogen release and corn ventional, low input or organic farming systems: demand in the upper Midwest. Agron. J. 87: Soil biology, soil chemistry, soil physics, energy 1063-1069. utilization, economics and risk. SARE Project Report #SW94-017. Western Region SARE. Logan, 402 Stute, J.K. and J.L. Posner. 1993. Legume Utah. www.sare.org/projects cover crop options for grain rotations in Wisconsin. Agron. J. 85:1128-1132. 414 Temple, S. 1995. A comparison of con - ventional, low input and organic farming 403 Sumner, D.R., B. Doupik Jr. and M.G. Boosalis. sys tems: The transition phase and long term 1981. Effects of reduced tillage and multiple viability. SARE Project Report #LW89-18. cropping on plant diseases. Ann. Rev. Western Region SARE. Logan, Utah. Phytopathol. 19:167-187. www.sare.org/projects 404 Sumner, D.R. et al. 1983. Root diseases of 415 Theunissen, J., C.J.H. Booij and A.P. Lotz. cucumber in irrigated, multiple-cropping systems 1995. Effects of intercropping white cabbage with pest management. Plant Dis. 67:1071-1075. with clovers on pest infestation and yield. Ento - 405 Sumner, D.R. et al. 1986. Interactions of mologia Experimentalis et Applicata 74:7-16. tillage and soil fertility with root diseases in snap 416 Tillman, G. et al. 2004. Influence of cover bean and lima bean in irrigated multiple-crop - crops on insect pests and predators in conserva- ping systems. Plant Dis. 70:730-735. tion tillage cotton. J. Econ. Entom. 97:1217-1232. 406 Sumner, D.R. et al. 1986. Conservation tillage 417 Townsend, W. 1994. No-tilling hairy vetch and vegetable diseases. Plant Dis. 70:906-911. into crop stubble and CRP acres. SARE Project 407 Sumner, D.R., S.R. Ghate and S.C. Phatak. Report #FNC93-028. North Central Region SARE. 1988. Seedling diseases of vegetables in conser - St. Paul, Minn. www.sare.org/projects vation tillage with soil fungicides and fluid 418 Truman, C. et al. 2003. Tillage impacts on soil drilling. Plant Dis. 72:317-320. property, runoff, and soil loss variations from a 408 Sumner, D.R. et al. 1991. Soilborne pathogens Rhodic Paleudult under simulated rainfall. J. Soil in vegetables with winter cover crops and Water Cons. 58:258-267. conservation tillage. Amer. Phytopathol. 419 Truman, C.C., J.N. Shaw and D.W. Reeves. Soc. Abstracts. 2005. Tillage effects on rainfall partitioning and 409 Sustainable Agriculture Network. 2005. sediment yield from an Ultisol in central Manage Insects on Your Farm: A Guide to Alabama. J. Soil Water Conserv. 60:89-98. Ecological Strategies. Beltsville, MD. 420 Tumlinson, J.H., W.J. Lewis and L.E.M. Vet. www.sare.org/learning-center/insect 1993. How parasitic wasps find their hosts. Sci. 410 Teasdale, J.R. et al.1991. Response of weeds American 26:145-154. to tillage and cover crop residue. Weed Sci. 39:195-199.

BIBLIOGRAPHY 227 421 Univ. of California Cover Crops Working 432 Weil, R. 2007. Personal communication. Univ Group. March 1996. Cover Crop Research and of Maryland, College Park, MD. Education Summaries. Davis, Calif. 50 pp. 433 Weil, R. and S. Williams. 2006. Brassica cover 422 Univ. of Calif. SAREP Cover Crops Resource crops to alleviate soil compaction. Page. www.sarep.ucdavis.edu/ccrop www.enst.umd.edu/weilbrassicacovercrops.doc 423 Unger, P.W. and M.F. Vigil. 1998. Cover crops 434 Welty, L. et al. 1991. Effect of harvest manage- effects on soil water relationships. J.Soil Water ment and nurse crop on production of five Cons. 53:241–244. small-seeded legumes. Montana Ag Research 8:11-14. 424 van Bruggen, A. H. C. et al. 2006. Relation between soil health, wave-like fluctuations in 435 Weitkamp, B. 1988, 1989. Medics, general. microbial populations, and soil-borne plant dis- Univ. of Calif. SAREP Cover Crops Resource Page. ease management. European J. of Plant Path. www.sarep.ucdavis.edu/ccrop 115:105-122 436 Weitkamp, B. and W.L. Graves. Medics, gener- 425 van Santen, E. 2007. Personal communica- al. Univ. of Calif. SAREP Cover Crops Resource tion. Auburn Univ, Alabama. Page. www.sarep.ucdavis.edu/ccrop 426 Varco, J.J., J.O. Sanford and J.E. Hairston. 1991. 437 Wendt, R.C. and R.E. Burwell. 1985. Runoff Yield and nitrogen content of legume cover and soil losses for conventional, reduced, and crops grown in Mississippi. Research Report. no-till corn. J. Soil Water Conserv. 40:450-454. Mississippi Agricultural and Forestry Experiment 438 Westcott, M.P. et al.1991. Harvest manage - Station 16:10. ment effects on yield and quality of small-seeded 427 Wagger, M.G. 1989. Cover crop management legumes in western Montana. Montana and N rate in relation to growth and yield of no- AgResearch 8:18-21. till corn. Agron. J. 81:533–538. 439 Westcott, M.P. 1995. Managing alfalfa and 428 Wagger, M.G. and D.B. Mengel. 1988. The role berseem clover for forage and plowdown nitro - of nonleguminous cover crops in the efficient gen in barley rotations. Agron. J. 87:1176-1181. use of water and nitrogen. p. 115–128. In W.L. 440 Weston, L.A., C.I. Nimbal and P. Jeandet. Hargrove (ed.). Cropping Strategies for Efficient 1998. Allelopathic potential of grain sorghum Use of Water and Nitrogen. ASA Spec. Publ. 51. (Sorghum bicolor (L.) Moench) and related ASA, CSSA, SSSA, Madison, Wisc. species. In Principles and Practices in Chemical 429 Wander, M.M. et al. 1994. Organic and con- Ecology. CRC Press, Boca Raton, Fla. ventional management effects on biologically 441 Weston, L.A. 1996. Utilization of allelopa thy active soil organic matter pools. Soil Sci. Soc. Am. for weed management in agroecosystems. Agron. J. 58:1120-1139. J. 88:860-866. 430 Washington State Univ. 2007. Mustard green 442 Wichman, D. et al. 1991. Berseem clover manures. WSU Cooperative Extension. seeding rates and row spacings for Montana. www.grant-adams.wsu.edu/agriculture/cover- Montana AgResearch 8:15-17. crops/green_manures 443 Willard, C.J. 1927. An Experimental Study of 431 Weaver, D.B. et al. 1995. Comparison of crop Sweetclover. Ohio Agricultural Station Bulletin rotation and fallow for management of No. 405, Wooster, Ohio. Heterodera glycines and Meloidogyne spp. in soybean. J. Nematol. 27:585-591.

228 MANAGING COVER CROPS PROFITABLY 444 William, R. 1996. Influence of cover crop and 453 Wright, S.F. and A. Upadhaya. 1998. A survey non-crop vegetation on symphlan density in veg- of soils for aggregate stability and glomalin, a etable production systems in the Pacific NW. glycoprotein produced by hyphae of arbuscular SARE Project Report #AW94-033. Western Region mycorrhizal fungi. Plant Soil 198:97-107. SARE. Logan, Utah. www.sare.org/projects 454 Yenish, J.P., A. D. Worsham and A.C. York. 445 Williams, W.A. et al. 1990. Ryegrass. Univ. of 1996. Cover crops for herbicide replacement in Calif. SAREP Cover Crops Resource Page. no-tillage corn (Zea mays). Weed Tech. 10:815- www.sarep.ucdavis.edu/ccrop 821. 446 Williams, S.M. and R.R. Weil. 2004. Crop 455 Yoshida, H. et al. 1993. Release of gramine cover root channels may alleviate soil com- from the surface of barley leaves. Phytochem. paction effects on soybean crop. Soil Sci. Soc. 34:1011-1013. Am. J. 68:1403-1409. 456 Zhu, Y. et al. 1998. Dry matter accumulation 447 Williams, W.A. et al. 1991.Water efficient and dinitrogen fixation of annual Medicago clover fixes soil nitrogen, provides winter forage species. Agron. J. 90:103-108. crop. Calif. Ag. 45:30-32. 457 Zhu, Y. et al. 1998. Inoculation and nitrogen 448 Wingard, C. 1996. Cover Crops in Integrated affect herbage and symbiotic properties of annu- Vegetable Production Systems. SARE Project al Medicago species. Agron. J. 90:781-786. Report #PG95-033. Southern Region SARE. 458 Larkin, R.P. and T.S. Griffin. 2007. Control of Griffin, Ga. www.sare.org/projects soilborne potato diseases with Brassica green 449 Wisconsin Integrated Cropping Systems Trial manures. Crop Protection. 26:1067-1077. (WICST). www.cias.wisc.edu/wicst http://dx.doi.org/10.1016/j.cropro.2006.10.004 450 Wolfe, D. 1994. Management strategies for 459 Larkin, R.P., T.S. Griffin and C.W. Honeycutt. improved soil quality with emphasis on soil 2006. Crop rotation and cover crop effects on compaction. SARE Project Report #LNE94-044. soilborne diseases of potato. Phytopath. 96:S48. Northeast Region SARE. Burlington, Vt. 460 Larkin, R.P. and C.W. Honeycutt. 2006. Effects www.sare.org/projects of different 3-year cropping systems on soil 451 Wolfe, D. 1997. Soil Compaction: Crop microbial communities and Rhizoctonia disease Response and Remediation. Report No. 63. of potato. Phytopath. 96:68-79. Cornell Univ., Department of Fruit and Vegetable Science, Ithaca, N.Y. 452 Worsham, A.D. 1991. Role of cover crops in weed management and water quality. p. 141–152. In W.L. Hargrove (ed.). Cover Crops for Clean Water. Soil and Water Conservation Society. Ankeny, Iowa.

BIBLIOGRAPHY 229 Appendix G RESOURCES FROM SARE

SARE’s print and online resources cover a range of The New American Farmer 2nd Edition, topics, from tillage tool selection to interpreting a 200 pp, $16.95 soil test for your conditions. Most publications Profiles 60 farmers and ranchers who are renew- can be viewed in their entirety at www.sare.org/ ing profits, enhancing environmental stewardship learning-center. and improving the lives of their families and communities by embracing new approaches to agri- BOOKS culture.

Building a Sustainable Business, 280 pp, $17 The New Farmers’ Market, 272 pp, $26.95 A business planning guide for alternative and sus- Covers the latest tips and trends from leading sell- tainable agriculture entrepreneurs that follows ers, managers, and market planners to best display one farming family through the planning, imple- and sell product. (Discount rates do not apply.) mentation, and evaluation process. Steel in the Field, 128 pp, online only Building Soils for Better Crops, 294 pp, $20.95 Farmer experience, commercial agricultural engi- How ecological soil management can raise fertili- neering expertise and university research com- ty and yields while reducing environmental bine to tackle the hard questions of how to impact. reduce weed management costs and herbicide use. Crop Rotation on Organic Farms: A Planning Manual, 154 pp, $24 Youth Renewing the Countryside, An in-depth review of the applications of crop 171 pp, $24.95 rotation, including improving soil quality and Shares stories of young people in each state health, and managing pests, diseases and weeds. changing the world through rural renewal.

How to Direct Market Your Beef, How to Order Books 96 pp, $14.95 Visit www.sare.org/WebStore; call (301) 374-9696 How one couple used their family’s ranch to or specify title and send check or money order to launch a profitable, grass-based beef operation Sustainable Agriculture Publications, PO Box 753, focused on direct market sales. Waldorf MD 20604.

Manage Insects on Your Farm: A Guide to Shipping & Handling: Add $5.95 for first book, Ecological Strategies, 128 pp, $15.95 plus $2 for each additional book shipped within Manage insect pests ecologically using crop diver- the U.S.A. Call (301) 374-9696 for shipping rates sification, biological control and sustainable soil on orders of 10 or more items, rush orders, or management. international shipments. Please allow 3-4 weeks for delivery. MD residents add 5% sales tax. (Prices are subject to change.)

Bulk Discounts: Except as indicated above, 25% discount applies to orders of 10-24 titles; 50% discount for orders of 25 or more titles.

230 MANAGING COVER CROPS PROFITABLY BULLETINS tion, guarding riparian areas, winter grazing and multi-species grazing to manage weeds. Clean Energy Farming, 20 pp. Strategies to improve energy efficiency, produce SARE Report from the Field, 20 pp. and use renewable fuels, and save energy while Biennial report featuring cutting-edge SARE protecting natural resources. research about profitable, environmentally sound farming systems that are good for communities. Diversifying Cropping Systems, 20 pp. Helps farmers design rotations, choose new Smart Water Use on Your Farm or Ranch, 1 6 crops, and manage them successfully. pp. Strategies for farmers, ranchers and agricultural How to Conduct Research on Your Farm or educators who want to explore new approaches Ranch, 12 pp., online only to conserve water. Outlines how to conduct research at the farm level, offering practical tips for both crop and live- Transitioning to Organic Agriculture, 20 pp. stock producers. Lays out promising transition strategies, typical organic farming practices, and innovative market- Marketing Strategies for Farmers and ing ideas. Ranchers, 20 pp. Offers creative alternatives to marketing farm What is Sustainable Agriculture?, 1 2 pp. products, such as farmers markets, direct sales, Defines sustainable agriculture by providing snap- and cooperatives. shots of different producers who apply sustainable principles on their farms and ranches. Meeting the Diverse Needs of Limited Resource Producers, 1 6 pp. A Whole Farm Approach to Managing Pests, A guide for agricultural educators who want to 20 pp. better connect with and improve the lives of Lays out ecological principles for managing pests farmers and ranchers who often are hard to in real farm situations. reach. How to Order Bulletins Profitable Pork, Strategies for Hog Visit www.sare.org/WebStore; call (301) 374-9696 Producers, 16 pp. (También disponible en or e-mail [email protected]. español.) Standard shipping for bulletins is free. Please Alternative production and marketing strategies allow 2-5 weeks for delivery. Rush orders that for hog producers, including pasture and dry litter must be received within three weeks will be systems, hoop structures, animal health and soil charged shipping fees at cost. All bulletins can be improvement. viewed in their entirety at www.sare.org/learning-center prior to placing your order. Bulletins Profitable Poultry, Raising Birds on Pasture, are available in quantity for educators at no cost. 1 6 pp. Farmer experiences plus the latest marketing Visit SARE Online ideas and research on raising chickens and SARE’s web site at www.sare.org identifies grant turkeys sustainably, using pens, moveable fencing opportunities available through the Sustainable and pastures. Agriculture Research and Education (SARE) program, reports research results, posts events and Rangeland Management Strategies, 1 6 pp. hosts electronic materials such as a database-dri- Methods for managing forage and other vegeta- ven direct marketing resource guide.

RESOURCES FROM SARE 231 Reader Response Form YOUR TURN: STRAIGHT TALK ABOUT THIS BOOK

We want to know what you think about this book. 6. What topics would you like to see SARE cover Please take a few moments to complete the follow- in future books or bulletins? ing evaluation. Your suggestions will help shape future SARE publications.

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232 MANAGING COVER CROPS PROFITABLY INDEX A planting of, 70, 78–80 comparative notes, 89–90 Agroecosystem, 25 in rotation, 42 in dairy, 14 Alfalfa, 10, 42, 110, 118, 119, Barrel medic. See Medics management of, 87–89 124, 137 Bees, 131, 136, 173, 181 nematicides for, 83 Allelopathy Biennials. See specific crops overview of, 81 berseem clover, 122 Biofumigation, 39, 86 planting of, 87–88, 89 black oats, 192 Biological farming, 96 precautions, 89 brassicas, 82 Biomass. See also Organic in rotation, 10, 37 buckwheat, 91 matter; Residue soil erosion protection, 11 conservation tillage and, balansa clover, 192 species of, 84–85 49–50 barley, 78, 79 turnips, 85 cowpeas, 126 berseem clover, 119, 120, 124 as vegetable greens, 85 oats, 94, 95 black oats, 192 Bromegrass mosaic virus, 76 rye, 32, 99, 103 brassicas, 81 Buckwheat sorghum-sudangrass hybrids, buckwheat, 93 advantages of, 19, 31, 32, 71 107 cereal grains, 73 benefits of, 90–91 subterranean clover, 168 in conservation tillage, 45 comparative notes, 93 sweetclover, 176 cowpeas, 125 cultural traits, 69 woollypod vetch, 186, 188 crimson clover, 130–31 disadvantages of, 72 Alsike clover, 163 field peas, 135–36 management of, 91–92 Annual Ryegrass. medics, 157 overseeding, 13 See Ryegrass, annual mustards, 84 overview of, 90 Annuals. See specific crops oats, 93, 94 performance and roles, Atrazine, 121, 161 red clover, 160, 161 67–68 Austrian winter peas. rye, 99 planting of, 70, 91–92 See Field Peas sorghum-sudangrass hybrids, in rotation, 39–40, 42 Avena sativa. See Oats 13, 106 Burclover. See Medics Avena strigosa. See Oats, black sunnhemp, 194 Burr medic. See Medics sweetclover, 13, 172, 177 B winter wheat, 115 C Bacteria. See Diseases Birdsfoot trefoil, 163 Calcium, 19, 91 Balkcom, Kipling, 58 Black medic. See Medics California. See also West, 61 Barley Black oats. See Oats, black Canadian field peas. advantages of, 32, 71 Blackeye peas. See Cowpeas See Field Peas benefits of, 78 Blando brome, 14 Canola. See Rapeseed comparative notes, 80 Blueberries, 182–83 Carbon, 73, 116, 140, 143, 144 cultivars, 80 Brassica hirta. See Mustards Cash crops cultural traits, 69 Brassica juncea. See Mustards brassicas, 85–86 disadvantages of, 72 Brassica napus. See Rapeseed in conservation tillage, 55–56 killing and controlling, 80 Brassica rapa. See Rapeseed cover crops and, 11, 34–43 management of, 78–80 Brassicas. See also Mustards; establishing in conservation overview of, 77–78 Radishes; Rapeseed system, 55–56 performance and roles, benefits of, 82–84 overseeding, 13 67–68, 77 carbon content, 73 rapeseed, 177

INDEX 233 in rotation, 15, 26–27, 34–43 for fertilizer reduction, 9–10 red clover, 160 winter wheat, 112 management of, 161–63 rye, 99 Cereal grains. See Small grains, overseeding, 12 white clover, 180 specific crops overview of, 159 Conservation tillage. Cereal rye. See Rye performance and roles, See Tillage, conservation Chlorsulfuron, 76 67–68 Corn belt. See Midwest Choppers/chopping. planting of, 70, 161 Corn cropping systems See also Rolling stalk in rotation, 36–37, 160, berseem clover, 123–24 chopper, 108, 121, 145 162–63 brassicas, 83, 85, 88 Clover, alsike, 163 Clover, rose, 14 in conservation tillage, 55 Clover, balansa, 170, 191–92 Clover, subterranean crimson clover, 132–33 Clover, berseem advantages of, 26, 31, 71 field peas, 141 advantages of, 71 benefits of, 165–66 hairy vetch, 142–43, 145 benefits of, 118–19 comparative notes, 170 medics, 156 comparative notes, 124 cultivars, 165, 170 oats-rye, 96, 103 cultural traits, 69 cultural traits, 69 red clover, 159, 160, 161, 162 disadvantages of, 72 disadvantages of, 72 in rotation, 9, 10, 142 management of, 119–24 management of, 166–70 with soybeans, 34–37, 41, 44, overview of, 118 in orchards, 14 53, 96, 112 performance and roles, overview of, 164–65 subterranean clover, 165–66, 67–68 performance and roles, 169, 170 planting of, 70, 119–20 67–68 white clover, 183 in rotation, 36–37, 123–24 planting of, 70, 166–67 winter wheat, 112 Clover, crimson reseeding, 13 Costs advantages of, 26, 30, 71 in rotation, 41 in corn rotation, 162 benefits of, 130–31 Clover, white cover crops, 9, 50 comparative notes, 134 advantages of, 71 fertilizer cost reduction, 9–10 cultivars, 133 benefits of, 179–80 lupins, 193 cultural traits, 69 comparative notes, 184 medics, 156 disadvantages of, 72 cultivars, 179 pesticides, 10, 27 in orchards, 14 cultural traits, 69 red clover, 160 overseeding, 12 disadvantages of, 72 reducing, 27 overview of, 130 living mulch, 13 seed, 64, 70, 189 for pasture and hay, 134 in orchards, 14 sorghum-sudangrass hybrids, performance and roles, overseeding, 12 106 67–68 overview of, 179 sunnhemp, 194 planting of, 70, 131–33 performance and roles, Cotton in rotation, 35, 36, 41 67–68 in conservation tillage, 55 soil erosion protection, 11 planting of, 70, 180–81 in no-till system, 149–50 winter cover, 15 in rotation, 37 rotations for, 40–42 Clover, red Collins, Hal, 60–61 soil erosion protection, 11 advantages of, 71 Companion crop. and soybeans, 126 benefits of, 159–61 See also Nurse crop Cover crops. comparative notes, 163–64 berseem clover, 119, 124 See also specific crops cultivars, 160–61, 164 cowpeas, 126 advantages of, 64–65, 71 cultural traits, 69 field peas, 138 benefits of, 9–11, 16, 57, 58, disadvantages of, 72 oats, 95 59, 60, 61

234 MANAGING COVER CROPS PROFITABLY comparative notes, 77, 80, 93, corn, 9, 10, 142 lupins, 193 105 corn-soybean, 34–37, 41, 44, medics, 157 for cotton, 40–42 53, 96, 112 oats, 97 cultural traits, 63–64, 69 crimson clover, 132–33 red clover, 163 disadvantages of, 65, 72 mustards, 83 rye, 99, 104 drawbacks, 57, 58, 59, 60, 61 planning, 12–15 sorghum-sudangrass hybrids, economics of, 50 potato/wheat, 86–87 107 for grain and oilseed, 34–36 reducing pesticides and her- subterranean clover, 166, 168 legumes, 116 bicides, 10, 24 white clover, 181 management of, 57, 58–59, rye in, 99 winter wheat, 115 59, 60, 61 sorghum-sudangrass hybrids, woollypod vetch, 188 nonlegumes, 46, 73–74 107 Disking. See Tillage performance and roles, soybeans, 10, 96, 108 Drought. See Soil moisture 62–63, 67 winter wheat, 112 Dry matter. See Residue for pest management, 25–33 Crop systems. Dryland production planting of, 13, 64, 70 See also Crop rotations cereal-legume crop rotations, promising species, 191–92 berseem clover, 123–24 42–43 regional species, 62, 66 in conservation systems, 45 field peas, 136, 138 rotation of, 15, 96 cowpeas, 129 medics, 153 selecting, 12–15, 57, 58, 59, crimson clover, 132–33 Pacific Northwest, 60–61 60, 61 field peas, 138–41 and soil moisture, 48 soil erosion and, 11, 16 hairy vetch, 142–43, 144, sweetclover, 176 summer covers, 13, 15 149–50 Duiker, Sjoerd, 57–58 sweetclover, 45–48 nematodes and, 31–32 Dutch white clover. testing on farm, 189–91 sorghum-sudangrass hybrids, See Clover, white for vegetables, 37–40 109–11 winter covers, 12–13, 15 subterranean clover, 169 E Cowpeas sweetclover, 177–78 Eberlein, Charlotte, 114 advantages of, 71 white clover, 181–84 Egyptian clover. benefits of, 125–27 Crotolaria juncea. See Clover, berseem comparative notes, 129 See Sunnhemp Erosion. See Soil erosion cultivars, 126–27 Crowder peas. See Cowpeas Experts, regional, 202–8 cultural traits, 69 disadvantages of, 72 D F management of, 127–29 Dairy farming, 14 Fagopyrum esculentum. in mixtures, 108 Damping off, 30, 129 See Buckwheat overseeding, 13, 15 Delgado, Jorge, 59 Fallow overview of, 125 Denitrification, 94 cover crops for, 12–13, 37 performance and roles, Diseases field peas, 138 67–68 annual ryegrass, 76 medics and, 153 planting of, 70, 126, 127 balansa clover, 192 sweetclover, 175–76, 177 in rotation, 40, 41 barley, 80 Farm systems, regional Crop rotations. berseem clover, 122–23 California, 61 See also Crop systems brassicas, 82 Midwest, 57 berseem clover, 123–24 in conservation tillage, 49 Northeast, 58 buckwheat, 92 cover crops and, 10, 29–31 Northern Plains, 59 cash crops, 15, 26–27, 34–43 crimson clover, 133 Pacific Northwest, 60 in conservation tillage, 45 field peas, 138

INDEX 235 Southeast, 58 Farmer accounts Farmer accounts Southern Plains, 59 Gies, Dale-potato/wheat Sheridan, Pat-No-till farming, Farmer accounts rotation, 86–87 52–53 Abdul-Baki, Aref-hairy vetch Granzow, Bill-sweetclovers Stevens, Will-wheat as winter as mulch, 150 for grazing and green cover, 115 Alger, Jess-perennial medic manure, 174 Thompson, Dick and for soil quality, fertility, 153 Groff, Steve-incorporating rye Sharon-hairy vetch and Anderson, Glenn-woollypod seed, 100 nematodes, 32 vetch as frost protectant Groff, Steve-killing rye, 101 Farming organizations, 200–202 and recognizing seedlings, Groff, Steve-no-till vegetable Fava beans, 78 186 transplanting, 103 Fernholz, Carmen, 97 Anderson, Glenn-woollypod Kirschenmann, Fred-sweet- Fertilizer vetch reseeding, 187–88 clover with nurse crops, and cover crops, 46 Bartolucci, Ron-establishing 177 for fallow systems, 139 woollypod vetch, 186 LaRocca, Phil-barley in red clover, 161, 162, 163 Bennett, Rich-frostseeding vineyard mix, 79 reducing, 9–10, 53 red clover, 162–63 Lazor, Jack-barley in subterranean clover, 169 Bennett, Rich-rye for weed mixtures, 79 Fescue, 13, 107, 144 management in soybeans, Maddox, Erol-rye, 105 Field Peas 104 Martin, Barry-managing rye, advantages of, 71 Beste, Ed-subterranean clover 102–3 benefits of, 135–37 with corn, 170 Matthews, Alan-white clover comparative notes, 141 Brubaker, John-crop rollers in contour strips, 181 cultural traits, 69 for no-till, 146 Mazour, Rich-managing disadvantages of, 72 Brutlag, Alan-lightly seeding sweetclover escapes, 178 for fertilizer reduction, 10 barley, 79–80 Moyer, Jeff-crop rollers for management of, 137–41 Burkett, Ben-winter peas for no-till, 146–48 overview of, 135 disease suppression, 138 Nordell, Eric and Anne-cover performance and roles, Carter, Max-wheat crops for weeds, 38–39 67–68 production, 113 Nordell, Eric and Anne-early planting of, 70, 136, 137–41 Davis, Bryan and Donna-oats seeding sweetclover, 178 in rotation, 42 and rye in corn/bean Phatak, Sharad-cover crops winter cover, 15 rotation, 96, 103 for pest related benefits, Forage de Wilde, Rich-killing rye, 101 30–31 annual ryegrass, 75 de Wilde, Rich-rye for mulch, Phatak, Sharad-cover crops to barley, 80 103 control pests in cotton, berseem clover, 119 de Wilde, Rich-spring seeding peanuts, 26–27 field peas, 136, 137 rye, 100 Podoll, David-sweetclover grasses, 73 Dunsmoor, Dan-sorghum weevil cycle, 176 medics, 155, 156 sudangrass nematicidal Quigley, Ed-managing rye, mixed seedings in, 117 effect, 109 103 rapeseed, 84 Erisman, Jack-timing rye kill, Quigley, Ed-seeding after red clover, 163 101 corn harvest, 35 rye, 105 French, Jim-cowpeas in Rant, Richard-clover in sorghum-sudangrass hybrids, rotation, 128 blueberries, 182–83 107 French, Jim-field peas, 140 Sheridan, Pat-managing rye, sweetclover, 173, 178 102

236 MANAGING COVER CROPS PROFITABLY white clover, 180 oats, 94, 95 crimson clover, 133–34 winter wheat, 115 red clover, 159 hairy vetch, 149 woollypod vetch, 188 subterranean clover, 165 medics, 154, 157 Freedom to Farm Act, 128 sweetclover, 172, 174 oats, 95 Frostseeding, 161, 162, 175, 180 predators, 25–29, 80, 149, Fruits. See also Orchards; H 166, 188 Vineyards, 99, 182–83 Hairpinning, 53, 56 rye, 99, 103–4 Hay sorghum-sudangrass hybrids, G annual ryegrass, 77, 80 109 Glomalin, 19 berseem clover, 119 subterranean clover, 166 Glycine max, 108 cowpeas, 126 suppression of, 78 Glyphosate crimson clover, 134 sweetclover, 38–39, 176 medics and, 153 medics, 157 white clover, 181 rapeseed and, 88 oats, 97 winter wheat, 115 ryegrass and, 76 sorghum-sudangrass hybrids, woollypod vetch, 188 sorghum-sudangrass hybrids 111 Integrated Pest Management and, 107 sweetclover, 173 (IPM), 28, 104, 138 subterranean clover and, 170 Health and safety issues, 11 Interseeding. Grasses Herbicides. See also Killing and See also Seeding/Seeds carbon content, 73 controlling berseem clover, 120 forage, 73 atrazine, 121, 161 cover crops and, 36 mixed seedings using, 117 glyphosate, 76, 88, 107, 153, hairy vetch, 144 for moisture conservation, 11 170 subterranean clover, 169 in orchards, 14 paraquat, 88, 107, 170 sweetclover, 177 Grazing reducing, 10 Irrigation annual ryegrass, 75, 76 sethoxydim, 107 barley, 79 berseem clover, 119 Hordeum vulgare. See Barley for overseeding, 12 crimson clover, 134 Hubam. See Sweetclovers potato/wheat, 114 field peas, 140 Humus. See Organic matter subterranean clover, 168 hairy vetch, 150 Hyphae, 19 woollypod vetch, 187 livestock poisoning, 89, 107, Italian ryegrass. 172, 194 I See Ryegrass, annual medics, 153, 155, 156 Inoculants oats, 97 for balansa clover, 191 K red clover, 161, 163 for cover crops, 70 Kaspar, Tom, 57 rye, 105 for cowpeas, 127 Killing and controlling. sorghum-sudangrass hybrids, for legumes, 20, 122–23, 189 See also Herbicides 107 for white clover, 181 barley, 80 subterranean clover, 166, 168 Insecticides, 154 berseem clover, 121 sweetclover, 173, 175, 176 Insects brassicas, 83, 88–89 winter wheat, 115 annual ryegrass, 76 buckwheat, 92 Great Lakes, 66 barley, 78 in conservation tillage, 51, Green manures berseem clover, 122–23 53–55 berseem clover, 118–19, 120 brassicas, 82, 89 cowpeas, 127 brassicas, 82, 83, 86–87 buckwheat, 91, 92 crimson clover, 132, 133 cowpeas, 126, 127 in conservation tillage, 48–49 field peas, 138 field peas, 136, 139 cover crops and, 10, 25–28 hairy vetch, 145, 148 nitrogen and, 21, 23–24 cowpeas, 126, 127–29 medics, 156

INDEX 237 oats, 95 Lupins, 19, 193 Midwest red clover, 162 Lupinus angustifolium L.. berseem clover, 120 roller-crimpers, 54 See Lupins buckwheat, 92 rye, 35, 100–101, 102 cover crops for, 34–37, 41, ryegrass, 76 M 57, 66 sorghum-sudangrass hybrids, Malting barley, 10 cowpeas, 129 108 Mammoth clover. hairy vetch, 145 subterranean clover, 167 See Clover, red medics, 155, 157 sweetclover, 175–76 Maura, Clarence, 194 oats, 94 white clover, 181 McGuire, Andy, 86, 87 rye, 100, 101 winter wheat, 115 Medicago. See Medics strip tillage, 56 Ladino clover. See Clover, white Medicago arabica, 154 sweetclover, 172, 173 Lana vetch. See Vetch, Medics weed problems, 75 woollypod advantages of, 71 Millet, 13, 163 Leaching. See also Nitrogen, 11, benefits of, 152–55 Mishanec, John, 108 18–19, 24, 45, 94, 100 comparative notes, 157–58 Mitchell, Jeffrey, 61 Legumes. See also specific crops cultivars, 158–59 Mixed seeding/Mixtures in conservation tillage, 47 cultural traits, 69 advantages/disadvantages of, grass mixtures and, 47 disadvantages of, 72 117–18 lentils, 11, 139 management of, 155–57 annual ryegrass, 76 moisture conservation, 11 for moisture conservation, 11 barley, 78, 79 nitrogen and, 9, 47, 94 in orchards, 14 berseem clover, 120 nodulation, 122–23 overview of, 152–53 brassicas, 88 in orchards, 14 performance and roles, cowpeas, 108 overview of, 116 67–68 crimson clover, 131, 133 in rotation, 9, 42–43, 139 planting of, 70, 155–56 grass/legume, 47 and rye mixtures, 40–41, 99, in rotation, 42, 156–57 hairy vetch, 99, 144 101, 103 Medium red clover. oats, 94 soil erosion protection, 11 See Clover, red red clover, 160 Lentils, 11, 139 Melilotus officinalis. rye, 99, 100, 101 Ley cropping subterranean See Sweetclovers rye/legume, 40–41, 99, 101, clover, 155 Meloidogyne hapla. 103 Living mulches See Nematodes sorghum-sudangrass hybrids, advantages of, 13 Meloidogyne javanica. 108 in conservation tillage, 55 See Nematodes subterranean clover, 165, 169 perennial ryegrass, 13 Microorganisms. See also winter wheat, 114–15 rodents and, 76 Biomass; Organic matter; Mowers/mowing turfgrasses, 13 Residue, 17, 21, 31 barley, 79 for weed management, 33 Mid-Atlantic berseem clover, 120–21 white clover, 180, 181 cover crops for, 66 brassicas, 88 Lolium multiflorum. crimson clover, 132 in conservation tillage, 55 See Ryegrass, annual field peas, 138, 141 cowpeas, 127–28 Louisiana S-1 clover. hairy vetch, 143 crimson clover, 133 See Clover, white rye, 101 fescue, 144 Lupin albus L.. See Lupins weed problems, 75 flail, 108, 120, 145 hairy vetch, 145

238 MANAGING COVER CROPS PROFITABLY medics, 155 New Zealand white clover. rye, 100 red clover, 163 See Clover, white sorghum-sudangrass hybrids, sicklebar, 108, 126, 148 Nitrogen 107, 108, 110 sorghum-sudangrass hybrids, annual ryegrass, 75, 77 Northeast Organic Network, 39 108 balansa clover, 192 Northern Plains subterranean clover, 168, 169 barley, 78 berseem clover, 121 sweetclover, 175–76 berseem clover, 118–19, 121 cover crops for, 59, 66 white clover, 181, 181–82 black oats, 192 crimson clover, 132 woollypod vetch, 187–88 brassicas, 81–82, 89 field peas, 135, 137, 138–39 Mulch. See Living mulches; cover crops, 9, 11, 18–24, 34, grain cropping systems, 42 Winterkilled mulches 36–41, 42, 45–47 medics, 152–53 Mustards. See also Brassicas cowpeas, 126 subterranean clover, 170 advantages of, 32, 71 crimson clover, 130, 131 sweetclover, 171, 173, barley and, 80 in dryland systems, 43 175–77 cultural traits, 69 estimating need for, 22–23 Northwest. See Pacific disadvantages of, 72 field peas, 136, 140–41 Northwest overview of, 84–85 fixation and release, No-till. See also Tillage performance and roles, 20–21, 35 barley, 78 67–68 hairy vetch, 142–43, 145 buckwheat, 92 planting of, 70 immobilization and and conservation tillage, 56 in rotation, 37 mineralization, 46, 47 corn, 9, 35, 83, 142–43, 145, weeds in, 84 legumes, 19, 20–21 156 Mutch, Dale, 183 medics, 153–54 cotton, 11, 149–50 Mycorrhizae, 19, 172 mixed seedings and, 117 cowpeas, 127 mustards, 84 crimson clover, 132 N nodulation, 122–23 farming, 52–53 Natural Resources nonlegumes, 19, 73–74 hairy vetch, 149–50 Conservation Service, 16 oats, 93–94 nitrogen and, 24 Nematodes red clover, 159–60, 161, 162 oats, 95, 96 balansa clover, 192 rye, 98, 100, 101 roller use, 146–48 barley, 80 sorghum-sudangrass hybrids, rye, 96, 99, 105 berseem clover, 123 109 soybeans, 104 black oats, 192 subterranean clover, 168 vegetable transplanting, 103, brassicas, 82–83, 86–87 sunnhemp, 194 148 in conservation tillage, 49 sweetclover, 38–39, 172, 176 Nurse crop. cover crops and, 10, 31–32 white clover, 179–80 See also Companion crop cowpeas, 129 winter wheat, 112, 113 annual ryegrass, 75 crimson clover, 133 woollypod vetch, 185–86 barley, 80 hairy vetch, 149 Nodulation, 122–23 berseem clover, 119 nematicides use, 83 Nonlegumes, 19, 46, 73–74 buckwheat, 91, 92 oats, 97 Northeast medics, 156 pin, 76 brassicas, 82 oats, 94 rye, 99 buckwheat, 92 rapeseed, 177 sorghum-sudangrass hybrids, cover crops for, 57–58, 66 winter wheat, 114–15 107, 109 crimson clover, 132 Nutrients. See also Nitrogen; subterranean clover, 168–69 field peas, 135 Phosphorus; Potassium, sunnhemp, 194 hairy vetch, 142, 144 18–24, 45–47 sweetclover, 176 oats, 94

INDEX 239 O small grains, 13 R Oats sorghum-sudangrass Radishes. See also Brassicas advantages of, 71 hybrids, 13 advantages of, 24, 71 benefits of, 93–94 sweetclover, 177 cultural traits, 69 comparative notes, 97 white clover, 180 overview of, 85 cultural traits, 69 performance and roles, disadvantages of, 72 P 67–68 management of, 94–97 Pacific Northwest planting of, 70 overview of, 93 brassicas, 80, 82 in rotation, 10, 83 performance and roles, cover crops for, 60–61, 66 Rapeseed. See also Brassicas 67–68 erosion control, 78 advantages of, 71 planting of, 70, 94–95, 96 Paradana clover. cultural traits, 69 in rotation, 9, 37, 40 See Clover, balansa disadvantages of, 72 Oats, black, 46, 97, 192–93 Paraquat, 88, 107, 170 overview of, 84 Orchards. See also Fruits; Paratylenchus projectus. performance and roles, Vineyards See Nematodes 67–68 annual ryegrass, 74 Perennials. See specific crops planting of, 70 barley, 78 Pests. See Diseases; Insects; Reseeding cover crops and, 14 Weeds balansa clover, 191, 192 medics, 154 Phosphorus barley, 79 rye, 99 brassicas, 89 crimson clover, 133, 183 subterranean clover, 164, buckwheat, 91 medics, 155, 156 165, 167, 169 cover crops, 19–20 subterranean clover, 168 woollypod vetch, 185, 186 crimson clover, 131 sweetclover, 173 Organic matter. hairy vetch, 144 white clover, 180 See also Biomass; Residue oats, 93–94 woollypod vetch, 187–88 cover crops and, 96 red clover, 163 Residue. See also Biomass; medics, 154–55 sweetclover, 172 Organic matter overview of, 17 winter wheat, 112 berseem clover, 122 rye, 99 Pisum sativum. See Field Peas brassicas, 83–84 winter wheat, 112 Planting. See Seeding/Seeds, buckwheat, 39–40 woollypod vetch, 186 specific crops in conservation tillage, 44–45 Overseeding. Plastic mulch, 150 hairy vetch, 143–44, 145 See also Seeding/Seeds Polysaccharides, 17–18 medics, 154–55 annual ryegrass, 12, 76 Potassium rye, 99, 101, 103, 104 barley, 79 crimson clover, 131 small grains, 36 berseem clover, 120 hairy vetch, 144 sorghum-sudangrass hybrids, in crop rotation, 12 oats, 93–94, 97 108 field peas, 141 rye, 98 subterranean clover, 168 hairy vetch, 12, 144 sweetclover, 172 sweetclover, 176 medics, 156, 157 winter wheat, 112 Rhizobia, 20 millet, 13 Potatoes, 81, 82, 83, 84, Riga, Ekaterini, 83, 87 oats, 94 86–87, 88 Rodale Institute, 146, 148 red clover, 161 Predators. See Insects rye, 12, 98, 100 Prussic acid, 96, 111

240 MANAGING COVER CROPS PROFITABLY Rolling. See also management of, 75–77 Sethoxydim, 107 Choppers/chopping; Rolling in orchards, 14 Sinapis alba. See Mustards stalk chopper overseeding, 12 Small grains berseem clover, 121 overview of, 74 cover crops for, 13 brassicas, 88 performance and roles, in dairy, 14 hairy vetch, 148 67–68, 74 for fertilizer reduction, 10 in no-till system, 146–48 planting of, 70, 75–76 overseeding, 13 roller-crimpers, 54 in rotation, 38, 39–40 in rotation, 36 for weed management, 33 soil improvement and, 10 soil erosion protection, Rolling stalk chopper. See also Ryegrass, perennial, 13 11, 36 Choppers/chopping; Rolling for weed suppression, 32–33 crimson clover, 133 S Smith, Gerald Ray, 169 hairy vetch, 145 Safflower, 40 Snail medic. See Medics red clover, 162 Secale cereale. See Rye Snap beans, 88 rye, 100, 101 Seed suppliers, 195–208 Soil. See also Soil erosion; for weed management, 33 Seeding/Seeds. See also Soil fertility and tilth; Soil Roundup. Frostseeding; Interseeding; moisture See also Glyphosate, 104 Mixed seeding/Mixtures; California, 61 Rye Overseeding; Reseeding; spe- compaction, 18, 24, 110 advantages of, 18–19, 26, 30, cific crops; Underseeding Midwest, 57 31, 32, 71 annual ryegrass, 70, 75–76 Northeast, 57–58 benefits of, 98–99 balansa clover, 191–92 Northern Plains, 59 comparative notes, 105 barley, 70, 78–80 overview of, 16–18 in conservation tillage, 52–53 berseem clover, 70, 119–20 Pacific Northwest, 60 cultural traits, 69 black oats, 192 Southeast, 58 in dairy, 14 brassicas, 87–88, 89 Southern Plains, 59 disadvantages of, 72 buckwheat, 70, 91–92 subsoil loosener, 66, 71–72, management of, 99–105 in conservation tillage, 50–51 106–7 moisture conservation cowpeas, 70, 126, 127 temperature, 48, 56 and, 11 crimson clover, 70, 131–33 Soil erosion. See also Soil; for mulch, 103, 104 field peas, 70, 136, 137–41 Soil fertility and tilth; Soil overseeding, 12, 35 hairy vetch, 70, 144, 148–49, moisture overview of, 98 151 annual ryegrass, 74 performance and roles, lupins, 193 barley, 78 67–68 medics, 155–56 brassicas, 82 planting of, 70, 99–100, 102 oats, 70, 94–95, 96 in conservation tillage, 45 in rotation, 10, 35–36, 37, 96, red clover, 161 cotton, 11 99 rye, 35, 70, 99–100, 102 medics, 155 soil improvement and, 10 sorghum-sudangrass hybrids, prevention, 11, 16 Ryegrass, annual 70, 108 rye, 98, 104 advantages of, 71, 74–75 subterranean clover, 166–67 subterranean clover, 166 benefits of, 74–75 sweetclover, 173, 175 winter wheat, 112 comparative notes, 77 white clover, 180–81, 184 Soil fertility and tilth. See also cultivars, 77 winter wheat, 70, 113–14 Soil; Soil erosion; Soil cultural traits, 69 woollypod vetch, 186–87, moisture disadvantages of, 72 188 annual ryegrass, 74 killing and controlling, 76 Sesbania exaltata, 108 barley, 78

INDEX 241 buckwheat, 91 medics, 154 Sunnhemp, 108, 127, 193–94 in conservation tillage, 45 strip tillage, 56 Sweetclovers cover crops, 11, 16–24, 39 sweetclover, 171 advantages of, 24, 71 field peas, 136 Southeast benefits of, 172–73 hairy vetch, 143 berseem clover, 120 comparative notes, 178 improving, 10–11, 13 cover crops for, 58–59, 66 cultivars, 178 red clover, 160 field peas, 135, 138, 139–40 cultural traits, 69 rye, 104, 105 medics, 154 disadvantages of, 72 ryegrass, annual, 74 Southern Plains management of, 173, 175–76 small grains, 36 cover crops for, 59–60, 66 overview of, 171–72 sorghum-sudangrass hybrids, crimson clover, 132 performance and roles, 13, 106–7 rye, 101 67–68 subterranean clover, 166, 167 weed problems, 75 planting of, 70, 173, 175 sweetclover, 172, 176 Southwest, 66 in rotation, 37, 176 white clover, 180, 182–83 Soybeans winter wheat, 112 berseem clover, 123–24 T Soil moisture. See also Soil; Soil brassicas, 85 Tillage. See also No-till erosion; Soil fertility and tilth in conservation tillage, 55 brassicas, 84 cover crops, 11, 24, 35–36, cotton intercropping, 126 conservation, 27, 29, 30, 42, 47–48, 96 crimson clover, 53 44–61 field peas, 136 crop rotation systems, 34–36, effect on organic matter, 18 medics, 155–56 41, 44 mustards, 84 nitrogen and, 21 field pea overseeding, 141 nitrogen and, 21–24 oats, 95 hairy vetch overseeding, 53, sorghum-sudangrass hybrids, rye, 101, 104 144 108, 109 sweetclover, 172, 177, 178 nematodes and, 32 strip tillage equipment, Sorghum-sudangrass hybrids red clover, 161–62 56–57 advantages of, 24, 32, 71 in rotation, 10, 96, 108 white clover, 183 benefits of, 106–7 rye, 52, 98, 104 Trials on farm, 189–90 comparative notes, 111 winter wheat, 53, 112 Trifolium alexandrinum. cultivars, 109, 111 Strip cropping See Clover, berseem cultural traits, 69 annual ryegrass, 77 Trifolium balansae. disadvantages of, 72 berseem clover, 124 See Clover, balansa management of, 108–11 in cotton, 41 Trifolium brachycalcycinum. moisture conservation and, cowpeas, 129 See Clover, subterranean 11 equipment, 56–57 Trifolium incarnatum. overseeding, 13 nematodes and, 32 See Clover, crimson overview of, 106 rye, 99 Trifolium michelianum Savi. performance and roles, white clover, 181, 182 See Clover, balansa 67–68 Subclover. See Clover, Trifolium pratense. planting of, 70, 108 subterranean See Clover, red in rotation, 37, 40 Sudax. See Sorghum-sudangrass Trifolium repens. soil improvement and, 10 hybrids See Clover, white Sorgoleone, 107 Sudex. See Sorghum-sudangrass Trifolium subterraneum. South hybrids See Clover, subterranean cover crops for, 66 Sugarbeets, 10, 80 Trifolium yanninicum. crimson clover, 132 Sulfur, 89, 144 See Clover, subterranean

242 MANAGING COVER CROPS PROFITABLY Triticum aestivum. Vetch, hairy medics, 154 See Wheat, winter advantages of, 71 sorghum-sudangrass hybrids, Turfgrasses, 13 benefits of, 142–44 111 Turnips, 85 comparative notes, 151 woollypod vetch, 185, 186, cultivars, 151 187 U cultural traits, 69 Undercutters, 32, 167 disadvantages of, 72 W Underseeding for fertilizer reduction, 9, 10 Weeds berseem clover, 120, 121 management of, 144–45, annual ryegrass, 75 cowpeas, 126 148–49 barley, 80 legumes, 97 as mulch, 150 berseem clover, 119 red clover, 111 overseeding, 12 brassicas, 83–84 sweetclover, 112 overview of, 142 buckwheat, 90–91, 92 Undersowing. See Overseeding performance and roles, in conservation tillage, 49–50 67–68 cover crops and, 10, 15, V planting of, 70, 144, 148–49, 32–33, 38–39 Vegetables 151 cowpeas, 125–26 annual ryegrass, 74 in rotation, 10, 35–36, 37, 41 hairy vetch, 143 berseem clover, 122, 124 soil erosion protection, 11 medics, 154 brassicas, 81, 85, 86 winter cover, 15 mustards, 85 cowpeas, 122 Vetch, purple, 40, 188 oats, 94, 95, 97 crimson clover, 132, 133 Vetch, woollypod rye, 99, 103, 104 in crop rotations, 37–42 advantages of, 71 sorghum-sudangrass hybrids, disease management, 29–31 benefits of, 185–86 107, 108–9 establishing in conservation comparative notes, 188 subterranean clover, 165, 169 system, 57 cultural traits, 69 suppression of, 78, 90–91, 95 hairy vetch, 35–36, 37, 148 disadvantages of, 72 sweetclover, 176, 178 insect management, 25–28 management of, 186–88 white clover, 182 mustards for, 84, 86 overview of, 185 winter wheat, 112, 115 nematode management, performance and roles, woollypod vetch, 186, 188 31–32 67–68 West rye for, 99, 103 planting of, 70, 186–87 barley, 79 sorghum-sudangrass hybrids, in rotation, 40 berseem clover, 120 107, 111 winter cover, 15 buckwheat, 92 subterranean clover, 164, Vicia benghalensis. cover crops for, 66 165–66, 168, 169, 170 See Vetch, woollypod cowpeas, 126 sunnhemp, 194 Vicia faba. See Fava beans crimson clover, 132 sweetclover, 177–78 Vicia villosa. See Vetch, hairy crop rotation systems, 40 weed management, 32–33 Vicia villosa ssp. dasycarpa. erosion control, 78 white clover, 179, 180, 181, See Vetch, woollypod field peas, 137 182 Vigna unguiculata. hairy vetch, 142 woollypod vetch, 185 See Cowpeas medics, 154, 156, 158, 159 Vetch, annual, 14 Vineyards sorghum-sudangrass hybrids, Vetch, cahaba, 26, 31, 41 annual ryegrass, 74–76 111 Vetch, common, 40, 139, 188 barley, 78, 79 subterranean clover, 164–67 buckwheat, 92 woollypod vetch, 185–87 cowpeas, 126

INDEX 243 Wheat, winter Windham, Gary, 192 advantages of, 30, 71 Winter rye. See Rye benefits of, 112–13 Winter Wheat. for cash and cover crop, 112 See Wheat, winter cultural traits, 69 Winterkill mulches disadvantages of, 72 annual ryegrass, 75 management of, 113–15 buckwheat, 92 moisture conservation and, crimson clover, 130 11 hairy vetch, 144 overview of, 111–12 medics, 156, 157 performance and roles, oats, 93–94, 95 67–68 sweetclover, 178 planting of, 70, 113–14 Wolfe, David, 110 in rotation, 10, 36–37, 38, 42–43 Y soil erosion protection, 11 Yellow mustard, 110 White sweetclover. Yellow sweetclover. See Sweetclovers See Sweetclovers Wild white clover. See Clover, white

244 MANAGING COVER CROPS PROFITABLY Ecoregions of the United States

Divisions The areas within each Division are Provinces. 1. Tundra 2. Subarctic 3. Warm Continental 4. Hot Continental 5. Subtropical 6. Marine 7. Prairie 8. Mediterranean 9. Tropical/Subtropical Steppe 10. Tropical/Subtropical Desert 11. Temperate Steppe 12. Temperate Desert 13. Savanna 14. Rainforest Mountains with Altitudinal Zonation Source: R.G. Bailey (see p. 209).

Source: Bailey, 1994 $19.00

Managing Cover Crops Profitably Third Edition

Farmers across the U.S. are using cover crops to smother weeds, deter pests and slow erosion. They find that cover crops help them cut costs and boost profits while improving their soil and protecting natural resources.

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