Handbook of Forage and Rangeland Insects

ENTOMOLOGICAL SOCIETY OF AMERICA

Handbook of Forage and Rangeland Insects EDITED BY

William O. Lamp Richard C. Berberet Leon G. Higley Craig R. Baird

Entomological Society of America 10001 Derekwood Lane, Suite 100 Lanham, MD 20706-4876 USA Phone: 301-731-4535 Fax: 301-731-4538 www.entsoc.org The Entomological Society of America (ESA) is a not-for-profit organization serving the scientific and professional needs of entomologists and individuals in related disciplines throughout the world.

Formed in 1953 by the consolidation of the American Association of Economic Entomologists (founded in 1898) and the former Entomological Society of America (founded in 1906), ESA is the largest international association of entomologists. It has approximately 6,000 members at colleges and universities, state and federal departments of agriculture, other government agencies, health agencies, private industry, parks, and museums.

This book was published in cooperation with The American Phytopathological Society (APS). APS is an international scientific organization devoted to the study of plant diseases and their control.

The Society was founded in 1908 and has grown from 130 charter members to nearly 5,000 plant pathologists and scientists worldwide. APS provides information on the latest developments and research advances in plant health science through its journals and its publishing arm, APS PRESS.

The American Phytopathological Society 3340 Pilot Knob Road St. Paul, MN 55121 USA Phone: 651-454-7250 Fax: 651-454-0766 www.apsnet.org To Order This Book 1-800-328-7560 or www.shopapspress.org ESA and APS members are entitled to a 10% discount and must reference their membership status at the time the order is placed.

Additional illustrations in the book were made possible by a contribution from BASF.

Front cover: Blue morph of redlegged grasshopper. Photo by Dan Johnson Back cover: Nymph of two-striped grasshopper. Photo by William Lamp COPYRIGHT Š 2007 BY THE ENTOMOLOGICAL SOCIETY OF AMERICA 10001 DEREKWOOD LANE, SUITE 100, LANHAM, MD 20706, USA ALL RIGHTS RESERVED PRINTED AND BOUND IN CHINA ISBN 0-9776209-0-5 LIBRARY OF CONGRESS CONTROL NUMBER: 2006927314

Contents

About the Editors/Contributing Authors .................. iv How to Use This Handbook ........................................ 1 Forage and Rangeland Production .............................. 2 Important Grasses and Legumes .................................. 2 Ecology and Physiology of Forage Crops ................... 12 Production Practices .................................................. 17 Arthropods and their Management ........................... 25 Injury Caused by Arthropod Pests .............................. 25 Integrated Pest Management ...................................... 28 Identification of Arthropods and Diagnosis of Injury ..33 Key to Pest Injury .................................................. 34 Key to Arthropod Pests .......................................... 35 Injurious Arthropods ................................................ 41 Foliar Pests ................................................................ 43 Ants ...................................................................... 43 Aphids .................................................................. 46 Blister Beetles ........................................................ 53 Caterpillars............................................................ 56 Chinchbugs ........................................................... 63 Grasshoppers and Crickets ..................................... 67 Leafhoppers and Planthoppers ............................... 76 Leafminers ............................................................ 79 Mites..................................................................... 81 Plant Bugs ............................................................. 83 Spittlebugs ............................................................. 91 Stem Borers ........................................................... 95

Stink Bugs ............................................................. 99 Thrips ................................................................. 101 Treehoppers ........................................................ 106 Weevils ............................................................... 108 Root Feeders............................................................ 113 Crane Flies .......................................................... 113 Weevils and Root Borers ...................................... 117 White Grubs ....................................................... 121 Flower and Seed Feeders .......................................... 125 Lygus Bugs .......................................................... 126 Seed Chalcid Wasps ............................................ 127 Beneficial Organisms .............................................. 129 Natural Enemies of Insects ...................................... 129 Fly Parasitoids ..................................................... 129 Wasp Parasitoids ................................................. 132 Lady Beetle Predators .......................................... 135 Spider Predators .................................................. 138 True Bug Predators .............................................. 143 Entomopathogens ............................................... 146 Pollinators ............................................................... 153 Weed Biological Control Agents ............................... 155 References Cited ..................................................... 164 Glossary ................................................................. 168 Sources of Local Information ................................. 173 Index ....................................................................... 176

iii

Contributing Authors

About the Editors

Dr. William O. Lamp is an associate professor in the Department of Entomology at the University of Maryland, College Park. He received a B.S. degree in Zoology from the University of Nebraska in 1972, a Master’s degree in Entomology from the Ohio State University in 1976, and a Ph.D. in Entomology and Agronomy at the University of Nebraska in 1980. He served as an Assistant Professional Scientist at the Illinois Natural History Survey until moving to Maryland in 1985. His research spans plant-insect interactions in crop systems, and is currently investigating the impact of herbivory on the persistence and tolerance of forage crops.

He also maintains an active program in aquatic entomology and ecology. He teaches courses and seminars in integrated pest management as well as freshwater biology.

He is the author of eight book chapters and 33 scientific articles. He has promoted regional research involved with forage insect pests, served as editor for the Journal of Agricultural and Urban Entomology and Forage and Grazinglands, and has been active in a number of roles within the Entomological Society of America.

Dr. Richard C. Berberet is a professor in the Department of Entomology and Plant Pathology at Oklahoma State University. He received a B.A. degree in biology from Carroll College in Helena, MT in 1966 and a Ph.D. in Entomology at the University of Nebraska-Lincoln in 1971.

He teaches courses in introductory entomology, insects of field crops, insect morphology, systematic entomology, host plant resistance, and integrated pest manage-

iv

ment. His research areas have included development of pest management programs in peanuts and alfalfa, and for 25 years has been a lead scientist with the Alfalfa Integrated Management Program for Oklahoma and the Southern Great Plains. He has also conducted studies on defense mechanisms of phytophagous insects against parasitoids. He is the author of seven book chapters, over 70 scientific articles, and 130 extension-related publications. He has served on the Editorial Board for Environmental Entomology, Publications Council, and as chair of Section F of the Entomological Society of America. He has received the James A. Whatley Award for Research in Agriculture given by Oklahoma State University and is an Honorary Member of the North American Alfalfa Improvement Conference.

Dr. Leon Higley is a Professor of Entomology at the University of Nebraska-Lincoln, where he teaches and does research.

Besides forage and field crop insects, his research interests include the physiological basis of plant-insect interactions, insect conservation, and forensic entomology. He is the author of over 98 scientific papers, 27 book chapters, and wrote or edited 5 books, including another in the ESA handbook series, The Handbook of Soybean Insect Pests.

Dr. Craig R. Baird is an emeritus faculty member in the Department of Plant, Soil and Entomological Sciences at the University of Idaho. He served for 28 years at the Parma Research and Extension Center in southwestern Idaho. He conducted an integrated research and extension program addressing arthropod pest management issues in urban settings and in numerous crops, including alfalfa, hop, mint and potatoes. He also conducted research on bot flies in the genus Cuterebra and fleas. He authored over 50 refereed journal articles and numerous extension publications.

Contributing Authors

Contributing Authors

Chris Buddle Dept. of Natural Resource Sciences McGill Univ., Macdonald Campus, 21, 111 Lakeshore Road Ste-Anne-de-Bellevue, Quebec H9X 3V9 C. Scott Bundy Dept.. of Entomology New Mexico State Univ.

Las Cruces, NM 88003 G. David Buntin Dept. of Entomology, Univ. of Georgia, Georgia Station Griffin, GA 30223

Wayne Bailey Dept. of Entomology Univ. of Missouri Columbia, MO 65211 Craig R. Baird Univ. of Idaho Parma Research and Extension Center, Parma, ID 83660 James Barbour Dept. of Plant, Soil, and Entomological Sciences Univ. of Idaho Parma Research and Extension Center, 29603 U of I Lane Parma, ID 83660 Frederick P. Baxendale Dept. of Entomology Univ. of Nebraska Lincoln, NE 68583-0816 Richard Berberet Dept. of Entomology and Plant Pathology, Oklahoma State Univ.

Stillwater, OK 74078 Sue Blodgett Dept. of Entomology Montana State Univ.

Bozeman, MT 59717 David H. Branson USDA–ARS, 1500 North Central Avenue Sidney, MT 59270

Alan B. Cady Dept. of Zoology Miami Univ.–Middletown 4200 East Univ. Blvd.

Middletown, OH 45042 John L. Capinera Dept. of Entomology and Nematology, Univ. of Florida Gainesville, FL 32611 Lewis L. Deitz Dept. of Entomology North Carolina State Univ.

Raleigh, NC 27695-7613 James D. DeYoung Kellogg Biological Station 3700 E. Gull Lake Drive Hickory Corners, MI 49060 Galen Dively Dept. of Entomology, Univ. of Maryland College Park, MD 20742 Kathy Flanders Dept. of Entomology and Plant Pathology, Auburn Univ., AL 36849 Ronald B. Hammond Dept. of Entomology Ohio Agricultural Research & Development Center The Ohio State Univ.

Wooster, OH 44691 Dennis C. Heim Agricultural Products Research & Development, BASF Corporation Princeton, NJ 08543 David W. Held Mississippi State Univ.

Coastal Research and Extension Center, 1815 Popps Ferry Road, Biloxi, MS 39532

v

Contributing Authors

Tiffany M. Heng-Moss Dept. of Entomology, Univ. of Nebraska Lincoln, NE 68583-0816

Doo-Hong Min E3774 Univ. Drive PO Box 168, Chatham, MI 49816

Thomas J. Henry Systematic Entomology Laboratory ARS, USDA c/o National Museum of Natural History, Washington, DC 20560-0168

Ron Ochoa Systematic Entomology Lab, USDA–ARS Beltsville, MD 20705

Leon G. Higley Dept. of Entomology, Univ. of Nebraska Lincoln, NE 68583-0816 William D. Hutchison Dept. of Entomology, Univ. of Minnesota 1980 Folwell Ave., St. Paul, MN 55108 Dan Johnson AAFC Research Centre Lethbridge, AB, Canada T1J 4B1 Robert L. Koch Dept. of Entomology, Univ. of Minnesota 1980 Folwell Ave., St. Paul, MN 55108 L. T. Kok Dept. of Entomology Virginia Tech Blacksburg, VA 24061-0319 William O. Lamp Dept. of Entomology Univ. of Maryland College Park, MD 20742 Curt Laub Dept. of Entomology Virginia Tech, Blacksburg, Va 24061-0319 Richard H. Leep Dept. of Crop and Soil Sciences, A464 Plant and Soil Science Building, Michigan State Univ.

East Lansing, MI 48824 Jonathan G. Lundgren Northern Grain Insects Research Laboratory, USDA–ARS, 2923 Medary Avenue Brookings, SD 57006-4267 Robert M. McPherson Univ. of Georgia, Coastal Plain Experiment Station Tifton, GA 31794

vi

Hassan Oloumi-Sadeghi Agricultural Products Research & Development, BASF Corporation Princeton, NJ 08543 Daniel C. Peck Dept. of Entomology NYSAES, Cornell Univ.

630 W. North St., Geneva, NY 14456 Elson Shields Dept. of Entomology Comstock Hall, Cornell Univ. Ithaca, NY 14853 Vinton Thompson Dept. of Biological Sciences Kean Univ., 1000 Morris Avenue Union, NJ 07083-0411 Jeffrey J. Volenec Dept. of Agronomy, Purdue Univ.

West Lafayette, IN 47907-1150 Matthew S. Wallace Dept. of Biological Sciences East Stroudsburg Univ.

East Stroudsburg, PA 18301 A.G. Wheeler, Jr. Dept. of Entomology, Soils, and Plant Sciences Clemson Univ. Clemson, SC 29634-0315 Robert N. Wiedenmann Center for Economic Entomology Illinois Natural History Survey Champaign, IL 61820 Suzanne J. Wold Dept. of Entomology, Univ. of Minnesota 1980 Folwell Ave., St. Paul, MN 55108 R. R. Youngman Dept. of Entomology Virginia Tech, Blacksburg, VA 24061-0319

Forage and Rangeland Production

How to Use This Handbook

Forage and rangeland crops harbor a wide variety of injurious and beneficial arthropods. Distinguishing the members of these two ecological groups is clearly important in the management of crop pests. Furthermore, even among the injurious species, some cause little economic loss, whereas others, often referred to as key pests, cause major loss and are subject to a variety of control practices. The primary goal of this handbook is to help individuals (producers, land managers, consultants, extension personnel, researchers, teachers, and students) to identify these arthropods and to outline methods for the management of both beneficial and harmful species.

The handbook is divided into four sections, “Forage and Rangeland Production,” “Arthropods and their Management,” “Injurious Arthropods,” and “Beneficial Organisms.”

The introduction at the beginning of the “Injurious Arthropods” section provides general information about arthropods that feed on forage crops as well as a description of the organization of that section. The introduction at the beginning of the “Natural Enemies” subsection of

How To Use This Handbook “Beneficial Organisms” provides an overview of those arthropods that kill or harm arthropod pests. In addition to the information and keys contained in these sections, the handbook includes a glossary to define terms, as well as an index to locate organisms and major topics. A section on sources of local information provides addresses of entomology departments throughout the United States and Canada.

The scope of this handbook covers forage and rangeland crops in the United States and Canada. The wide range of topographic and climatic conditions in this geographic area results in the cultivation of a large number of plant species. Therefore, as a practical matter, this guide only focuses on the major crop species as listed in “Important Grasses and Legumes for Forage and Rangeland Production Systems.” Nevertheless, the scope of injurious and beneficial arthropods covered is broad and the general key and descriptions are suitable for many other crop species aside from forages.

Most of the handbook discusses the identification, biology, and management of the primary groups (or families) of arthropods found in forages and rangelands.

Space limitations, as well as incomplete knowledge about all arthropods associated with these crops, narrowed the focus. Thus, the taxonomic keys only identify arthropods (injurious or beneficial) to the more general family or higher taxonomic groups, and the crop injury keys only describe the more typical symptoms. The injury keys point to the likely arthropod groups that cause the symptoms. The individual discussions following the keys provide guidelines for collection and identification of key pest species, as well as the arthropod groups in general. The subsequent sections describe the biology, ecology, and enhancement of beneficial groups, including natural enemies of arthropods, pollinators, and weed biological control agents.

1

Forage and Rangeland Production

Forage and Rangeland Production

tices of the more important species used for forage and rangeland production are discussed.

History of Forage Production

Important Grasses and Legumes The wide range of topographic and climatic conditions in the United States and Canada results in the cultivation of a large number of plant species for forage and rangeland production systems. There are more than 32 million hectares of land in hay and silage production in North America (Fig. 1) The largest area of production of hay and silage is in the midwestern region of the United States.

The largest area of production of hay and silage in Canada is in Alberta. Species grown in the United States and Canada vary greatly between regions. Cool-season grasses predominate the midwestern, northern, and northeastern portions of the United States and Canada, and forages such as elephantgrass and perennial peanut are grown primarily in the coastal plains in the southern United States.

Alfalfa is widely adapted and is grown in every state in the United States and in all provinces in Canada. However, the most concentrated areas of production of alfalfa are found in the Midwest and Northeast United States and Ontario. This chapter focuses primarily on the major grasses and legumes (Tables 1 and 2). Management prac-

Western 4.5 million ha 32.6 million tonne

North Central 12.1 million ha 62.3 million tonne

North East 2.3 million 11.8 million tonne

Southern 6.1 million ha 27.5 million tonne

Fig. 1. Hay and silage production in North America by region.

2

Forage production has long been important to human civilization. The dawn of civilization found humans grazing sheep and goats in the Fertile Crescent of the Middle East. Following the seasonal rainfall patterns with their herds, herders probably helped establish the trade routes that connected cities and formed the basis for the ancient Assyrian and Babylonian empires. As civilization developed, so did forage and rangeland production systems.

Farmers discovered how to grow crops to sustain their herds of cattle or sheep instead of moving their herds to locate forage. Over the ages, forage production has developed into a fine science in which almost every factor that affects production, from fertility, to species selection, and even water availability, has been brought under human management.

Native rangeland utilization also has been refined. Native Americans living on the plains were known to burn the prairies to improve the grazing. Now rangeland managers can use satellite photos and weather maps to predict where and when to graze their huge tracts of land.

Several significant advances in plant breeding for improvement of forage crops have been made. Forage species are improved for varied soil moisture conditions, fertility, quality, growing seasons, and pest tolerances. Forage producers within regions of the United States and Canada can select the forage crops best suited to their particular conditions. Species, and varieties within species, can be chosen for drought tolerance, greater winter hardiness, or greater pest resistance.

Legumes are characterized by a type of fruit pod that is called monocarpellary (one-chamber) fruit containing a single seed or a single row of seed that dehisces along both sutures or ribs. Legumes can be annual, biennial, or perennial, depending on the lifespan of the plant. Morphology of legumes differs greatly from that of grasses.

There are different morphological characteristics between legume species that help in identification. The leaves of legumes are arranged alternately on the stem and are usually connected to the stem by a petiole. When a single leaf is attached directly to the petiole, it is termed unifoliolate. In compound leaves, (trifoliolate) three or more leaf blades are individually connected to the petiole by a short stalk called a petiolule. The inflorescense of legumes varies between species and is useful in identifying legume species. Morphological characteristics can

Forage and Rangeland Production

Table 1. Major North American Forage Legume Species.

Common name

Cool or Drought warm tolerance season Uses

Species

Longevity

Palatability

Winter Growth hardiness habit

Alfalfa

Medicago sativa L.

Perennial

Very High

Good

Herbaceous, Good 15–36 in.

Cool

Hay, silage, pasture, green manure

Northern half of U.S.

Yes

Red clover

Trifolium Acts as pratense L. biennial

High

Good

Herbaceous, Fair 12–36

Cool

Pasture, shortterm hay

Eastern half of U.S. and Northwest

Yes

Sweetclover

Melilotus spp.

Annual or biennial

Medium

Good

Herbaceous, Good 16–60 in.

Cool

Green manure, hay pasture, silage

Great plains Yes and Midwest.

White clover

Trifolium repens L.

Perennial

Very high

Good

Herbaceous, Poor 3-12 in.

Cool

Pasture because of low yield

Eastern half of U.S.

Yes

Crimson clover

Trifolium Winter incarnatum annual L.

Poor as pasture

Good

Herbaceous, Poor 12–36 in.

Cool

Hay, silage, soil improvement

Southeast U.S.

Yes

Medium to high

Good

Herbaceous

Cool

Pasture

Southeast U.S.

Low

—

Herbaceous, Fair 2–34 in.

Warm

Late-summer pasture or hay.

Southeast U.S.

No

Arrowleaf Trifolium Winter vesiculosum annual clover Lespedeza Lespedeza spp.

Summer High annual but can reseed.

Good

Distribution

Bloat hazard

Sainfoin

Onobrychis Perennial viciifolia Scop.

Medium

Medium

Herbaceous, Excellent 6–12 in.

Warm

Suited to infrequent cutting hay or silage

Western U.S.

No

Birdsfoot trefoil

Lotus Perennial corniculatus L.

Very high

Good

Herbaceous, Fair 15–44 in.

Cool

Pastures with history of low productivity

Upper Midwest, and Northeast

No

Alsike clover

Trifolium hybridum

Perennial acts like biennial

High

Good

Herbaceous, Fair 12–36 in.

Cool

Pasture, hay, best suited to poorly drained sites

Upper Midwest, Central Pacific states

Yes

Crownvetch

Coronilla varia L.

Perennial

Medium

Good

Herbaceous, Fair 12–48 in.

Cool

Conservation, pastures, can become invasive

Upper Midwest, Northeast

No

Cicer milkvetch

Astragalus cicer L.

Perennial

Medium

Good

Herbaceous, High to 24 in.a

Warm

Pasture, soil conservation

Great Plains, Northwest

No

aspreads

by rhizomes

be useful in staging maturity of legumes (Table 3). Staging the maturity of legumes can be useful in predicting the nutritive value of legume forages in the field.

Grasses are either annuals or perennials and vary widely in structure and growth habits. General morphology of grasses includes characteristics such as leaves, of which each consists of a sheath, blade, ligule, and in some cases auricles. The stems of grasses in the seedling and nonreproductive growth stage tend to be very short consisting

of nodes and unelongated internodes.

When flowering occurs in grasses, there is an elongation of the internodes. Inflorescence of grasses consists of a group of spikelets. Spike inflorescense characteristics of wheat and perennial ryegrass are attached directly to the rachis. The raceme differs from the spike in that the spikelets are connected to the rachis by short stalks called pedicels. The panicle is the most common grass inflorescence.

It is branched and has pedicelled spikelets. Examples of 3

Forage and Rangeland Production

Table 2. Major North American Forage Grass Species Common name

Species

Longevity Palatability

Winter Growth hardiness habit

Cool or Drought warm tolerance season Use

Distribution

Wheatgrass

Agropyron spp., Perennial Elymus spp.

Higher early

Good

Bunchgrass, 1–2 ft

Good

Cool

Rangeland, fibrous roots hold soil well

Great Plains, and Southwest

Big bluestem

Andropogon Perennial gerardii Vitman

High

Good

Bunchgrass, 3–8 ft

Good

Warm

High-yielding, warm-season pasture and hay

Great Plains and Midwest

Sideoats grama

Bouteloua curtipendula (Michx.) Torr.

Good

Good

Bunchgrass, Good 3 ft max rarely forms sod

Warm

Native warmseason pasture

Great Plains and Midwest

Buffalograss

Buchloe Perennial dactyloides (Nutt.) Engelm.

High in green Good summer stage

Low growing spreads by stolons

Good

Warm

Native warmseason pasture, lawn, and turf

Central and southern Great plains

Indiangrass

Sorghastrum nutans (L.) Nash

Perennial

High

Good

Sod-forming grass, 4–8 ft

Good

Warm

High-yielding, warm-season pasture and hay

Great Plains and Midwest

Dropseed

Sporobolus spp.

Perennial

Fair early

Good

Bunch grass, 36 in. max

Good

Warm

Cover for other slower developing natives

Great Plains and Upper Midwest

Kentucky bluegrass

Poa pratensis L.

Perennial

Very high

Good

Sod-forming Poor grass, 12–40 in.

Cool

Low yielding, cool-season pasture and turf

All of North America

Smooth bromegrass

Bromus inermus Perennial Leyss.

Very high

Good

Sod-forming Good grass, 20–40 in.

Cool

Medium-to-high- Northern U.S. and upper yield, pasture Midwest and hay

Reed canarygrass

Phalaris arundinacea L.

Perennial

Low

Good

Sod-forming Good grass, 24–72 in.

Cool

High-yielding, pasture, hay, conservation

Northern U.S.

Timothy

Phleum pratense Perennial L.

High

Good

Bunchgrass, 20–40 in.

Poor

Cool

Medium-to-high yield, coolseason pasture, hay

Upper Midwest and Northeast

Orchardgrass

Dactylis glomerata L.

Perennial

Mediumhigh

Fair

Bunchgrass 24-48 in.

Fair

Cool

High-yielding, cool-season pasture

Northeast, Midwest, and Northwest

Tall fescue

Festuca arundinacea Schreb.

Perennial

Medium

Fair

Sod forming bunchgrass 24-48 in.

Fair

Cool

High-yielding, cool-season pasture, hay, conservation

Midwest, Mid-Atlantic, and Southeast

Red fescue

Festuca rubra L. Perennial

Medium

High

Creeping grass High forms dense tufts

Warm

Suitable for dry turf areas

All of North America

Bahiagrass

Paspalum Perennial notatum Flugge

High

Poor

Deep rooted, dense sod

High

Warm

Pasture for beef cattle, hay

Deep South

Bermudagrass Cynodon dactylon Perennial (L.)Pers.

Good

Poor

Sod forming withstands flooding

High

Warm

Hay, or pasture for beef cattle

Southern U.S.

Perennial ryegrass

Lolium perenne Perennial x L. multiflorum Lam.

Very high

Medium Bunchgrass to fair 12-24 in.

Poor

Cool

Low-to-medium Southeast yield, cooland season pasture, Northwest hay, and turf

Festulolium

Festulolium braunii (K.A.)

High

Good

Good

Cool

High-yield pasture

4

Perennial

Perennial

Sod-forming bunchgrass

Northern US

Forage and Rangeland Production

Table 3. Quantifying Alfalfa Development.

Growth stage number

Stage name

Stage definition

0

Early vegetative

Stem length, <6 in.; no buds, flowers, or seed pods

1

Mid vegetative

Stem length, 6–12 in.; no visible buds, flowers, or seed pods

2

Late vegetative

Stem length, >12 in.; no visible buds, flowers, or seed pods

3

Early bud

One or two nodes with visible buds; no flowers or seed pods

4

Late bud

Three or more nodes with visible buds; no flowers or seed pods

5

Early flower

One node with one open flower; no seed pods

6

Late flower

Two or more nodes with open flowers; no seed pods

Source: Kalu, B. A., and G. W. Fick. 1983. Morphological stage of development as a predictor of alfalfa herbage quality.

Crop Sci. 23: 1167–1172.

grasses with panicles are smooth bromegrass, Kentucky bluegrass and switchgrass. Morphological characteristics of grasses have been used successfully to quantify grass development stages (Table 4).

Important Forage Legumes in North America Alfalfa (Medicago sativa L.) Alfalfa was first successfully grown in the United States around the mid 1850s. It is now grown intensively throughout much of central United States and Canada, but can be found throughout the entire North American continent (Fig. 2) Alfalfa is well adapted to a wide range of climatic conditions. It grows well under irrigation in dry climates of western North America with well-drained, fertile soils, as well as in the temperate climates with higher humidity found in the eastern United States. Alfalfa has excellent drought tolerance; it becomes dormant during periods of

Fig. 2. Alfalfa, Medicago sativa L.

drought. However, high humidity and abundant rainfall can cause increased incidence of diseases. It is well adapted to varying soil conditions, being relatively tolerant of alkaline soil. Alfalfa is best suited to well-drained, deep loam soils; it does poorly in acidic soils (optimal soil pH 6.8–7.0) unless lime is added. Its perennial nature results in it being an excellent conservation crop that reduces runoff and soil erosion.

Alfalfa produces more protein per hectare than any other forage crop. When harvested at the proper maturity (late bud to early flowering stage), alfalfa can produce nearly as much energy as corn silage. Its high mineral content and synthesis of 10 vitamins make it desirable as a ration component for most farm animals. Knowing the right time to harvest is important in obtaining high-quality forage. In determining when to cut alfalfa, it is helpful to have a knowledge of growing degree-days (GDDs) or the use of an alfalfa quality stick. The Kalu–Fick method of staging alfalfa is used to quantify alfalfa maturity in the field (Table 3). The predictive evaluation for alfalfa quality (PEAQ) is based upon the alfalfa growth stages, as well as alfalfa plant height. GDDs also work well for predicting when to cut first harvest of alfalfa. The ideal harvest time for alfalfa being fed to high-producing dairy cows is when the neutral detergent fiber (NDF) content of alfalfa is about 40%. When alfalfa reaches 750 GDDs, the NDF fiber content is about 40%. Many producers use combinations of these methods for determining when to harvest to achieve forage quality goals on their farms.

Alfalfa is usually harvested multiple times throughout the year, from twice in northern Canada to 6–10 times under irrigation in southwestern United States. Alfalfa cut at a prebud or early bud stage has a higher protein content and greater feed value. However, plants that are continually cut at an early bud stage cannot replenish carbohydrate 5

Forage and Rangeland Production

Table 4. Quantifying grass development Stage

Index

Description

Vegetative-Leaf development VE or V0 V1 Vn

1.0 (1/N) + 0.9a (n/N) + 0.9

Emergence of 1st leaf 1st leaf collared nth leaf collared

Elongation-Stem elongation E0 E1 En

2.0 (1/N) + 1.9 (n/N) + 1.9

Onset of stem elongation 1st node palpable/visible nth node palpable/visible

Reproductive-Floral development R0 R1 R2 R3 R4 R5

3.0 3.1 3.3 3.5 3.7 3.9

Boot stage Inflorescence emergence/first spikelet visible Spikelets fully emerged/peduncle not emerged Inflorescence emerged/peduncle fully elongated Anther emergence/anthesis Post-anthesis/fertilization

Seed development and ripening S0 S1 S2 S3 S4 S5

4.0 4.1 4.3 4.5 4.7 4.9

Caryopsis visible Milk Soft dough Hard dough Endosperm hard/physiological maturity Endosperm hard/seed ripe

aWhere

n equals the morphological event and N equals the number of events within the primary stage. This system consists of a universal set of morphological descriptors for forage and range grasses and a continuous numerical index. The life cycle of individual grass tillers is divided into five primary growth stages (i) germination, (ii) vegetative, (iii) elongation, (iv) reproductive, and (v) seed ripening. Substages corresponding to specific morphological events are defined within each primary stage. Each growth stage consists of a primary and secondary stage and has both a mnemonic code and numerical index associated with it. The codes were designed to be easily memorized and are useful for applying the system in the field. The numerical index is included so that the stages can be expressed quantitatively.

Source: Moore K. J., L. E. Moser, K. P. Vogel, S. S. Waller, B. E. Johnson, and J. F. Pederson. 1991. Description and quantifying growth stages of perennial grasses. Agron. J. 83: 1073â&#x20AC;&#x201C;1077.

and nitrogen reserves, thus weakening the plants and leading to death and more rapid stand depletion. Late-stage cutting reduces quality, but generally means greater yields and longer stand persistence. This tradeoff means that a balance must be created between early and late cuttings as well as animal nutrition needs. More information on the importance of root reserves is provided in the section on ecology and physiology of forage crops.

Bacterial wilt [Clavibacter michiganensis subsp. insidiosus (McCulloch) Davis et. al. = Corynebacterium insidiosum (McCulloch) Jensen], phytophthora root rot (Phytophthora megasperma F. sp. Medicaginis), anthracnose (Colletotrichum trifolii Bain), verticillium wilt (Verticillium albo-atrum), aphanomyces (Aphanomyces euteiches), are some of the diseases that attack alfalfa. Phytophthora and anthracnose cause deterioration in stands by destroying the roots and crowns of infected plants. Verticillium affects older stands of alfalfa restricting the upward flow of water and nutri6

ents to the plant eventually causing death. Aphanomyces root rot often results in reduced yields and stunted chlorotic plants. Planting resistant cultivars is usually the best way to control these diseases.

Red Clover (Trifolium pratense L.) Red clover is a short-lived perennial herbaceous plant, which usually acts like a biennial in the United States and Canada because of disease pressure. It is a prolific seed producer when conditions are right, and it is well adapted where summer temperatures are moderate and adequate moisture is available through the growing season. Stems of varieties grown in the United States are densely pubescent, making them less susceptible to potato leafhopper damage, and leaflets are usually marked with a white â&#x20AC;&#x153;watermarkâ&#x20AC;? V (Fig. 3).

Red clover is grown from northeastern United States, through the Midwest and into North Dakota, down to

Forage and Rangeland Production is insufficient under the cloudy weather. The causal organism can infect wide ranges of legumes, such as alsike clover, white clover, and vetches. When severe, black patch can extend to the entire plant and cause plant death. The causal organism produces the alkaloid, suraflamine, which causes goatâ&#x20AC;&#x2122;s slaver disease and slobbering in horses.

Fig. 3. Red clover, Trifolium pratense L.

Kansas and the upper southern United States. It is also grown extensively in the Northwest. A native of Southeastern Europe, this legume is adapted to a wide range of climates, soil types, fertilities, and management practices. Although it has been replaced by alfalfa as the most commonly grown forage legume in North America, it was once used extensively throughout the United States as a pasture species. It is most often grown in mixed plantings with cool-season grasses (orchardgrass, tall fescue, timothy, or smooth bromegrass) or with warm-season grasses (dallisgrass, johnsongrass) as a forage crop, but it can also be grown by itself. Two types of clover are grown in the United States: mammoth, a single-cut variety, and medium, a multicut variety. Medium is the most commonly used red clover because it can be grazed or harvested several times each year. Indigenous common red clovers are available in the United States.

Compared with other legumes and grasses, red clover seedlings are very competitive and shade tolerant, especially when supplied with adequate moisture under cooler growing conditions. Red clover tolerates a lower soil pH than alfalfa and typically yields well during the establishment year when managed properly. Red clover is one of the most easily established legumes in closely grazed or renovated pastures. Rotational grazing improves the longevity of red clover by allowing plants to recover between grazing events.

Important diseases of red clover include sclerotinia (Sclerotinia trifoliorum Eriksson, Ascomycotina), powdery mildew (Causal organism: Erysiphe trifolii Greville and Ascomycotina), and black patch (Causal organism: Rhizoctonia leguminicola Gough et Elliott, Imperfect fungi) Sclerotinia occurs in cool and wet regions and causes plant death. Powdery mildew occurs severely in the cool, dry conditions; and the damage increases when sunshine

White Clover (Trifolium repens L.) White clover is one of the most widely adapted clovers within the United States and Canada (Fig. 4). It is most often grown in association with cool-season grasses and is grazed as pasture. White clover is generally believed to have originated in the Near East. It can be grown in wet areas of soils with low pH, but it is better adapted to welldrained silt loam and clay soils of pH 6.0 to 7.0. It does not tolerate saline or highly alkaline soils.

Fig. 4. White clover, Trifolium repens L.

Indigenous, or â&#x20AC;&#x153;wildâ&#x20AC;? white clovers have small leaves and are dense, spreading plants that persist well under the environment in which they grow. Ladino white clover was introduced from Italy around 1900. It is larger than the common varieties and tends to grow taller than the smaller indigenous clovers. Ladino white clover grows well on many soil types. Its shallow but dense and prolific root system makes it a good candidate for soil conservation. By producing stolons soon after establishment, a single plant under optimal conditions can cover as much as four square feet.

As a pasture species, Ladino white clover is valuable when planted with cool-season-grasses such as perennial ryegrass.

Like other forage legumes, white clovers can improve the forage quality of pastures and supply pasture grasses with atmospheric nitrogen fixed by symbiotic bacteria.

When grazed in a pasture system, the new varieties of white clover, sown in mixed plantings with grasses, can produce more forage than clover alone. Clovers tolerate grazing quite well, are very palatable and highly digestible.

Major seed companies in the United States are marketing improved white clover varieties developed for greater 7

Forage and Rangeland Production yields, longer persistence, and better pest resistance.

A major concern when grazing cattle on white clover is bloat. Bloat is caused by rumen foam formation that closes a muscle in the animal’s throat, preventing gas from escaping. This creates intense pressure on vital internal organs, crushing them and causing death. Bloat can be averted by interseeding grasses with legumes into a pasture mixture, by not turning hungry animals into lush pasture without first giving them dry forage, and by using antibloat feed additives.

Important diseases affecting white clover include sclerotinia crown rot and root (Causal organism: Sclerotinia trifoliorum Eriksson, Ascomycotina) and powdery mildew (Causal organism: Erysiphe trifolii Greville and Ascomycotina). Sclerotinia can cause plant death in cool and wet regions; whereas powdery mildew affects white clover similar to red clover.

Birdsfoot Trefoil (Lotus corniculatus L.) Birdsfoot trefoil is a leafy, fine-stemmed legume, which usually grows 20–30 in. (50–75 cm) high depending upon soil characteristics and moisture (Fig. 5). Many stems are produced from a single crown. The root system consists of a well-developed taproot with many branch roots. Yellow flowers (4–8 per stem) produce seedpods resembling a bird’s foot, giving the plant its common name. It is well adapted to poorly drained, low pH soils. It is resistant to phytophthora root rot and numerous insect pests; unlike alfalfa and white clover, it does not cause bloat in animals because of higher levels of tannins. Birdsfoot trefoil has traditionally been used in grazing systems, but varieties are now available that are suitable for hay production. It is most productive on fertile, well-drained soils with near neutral pH, but even under optimal conditions birdsfoot trefoil yields about 50–80% lower than alfalfa. However, relatively high yields of quality forage can be maintained on land that is marginal with low soil pH or poor internal

Fig. 5. Birdsfoot trefoil, Lotus corniculatus L.

8

drainage and low soil moisture.

Birdsfoot trefoil requires careful management for successful establishment because of its small seed size and poor seedling vigor. The small seed size necessitates that the seed be placed no deeper than 1/4 in. in the soil to achieve maximum stand density. Firming the soil before and after planting improves seed-to-soil contact, enhancing germination and emergence. Seed needs to be inoculated with Rhizobium lupini bacteria, specific to birdsfoot trefoil.

Its excellent grazing potential and bloat-free characteristics make birdsfoot trefoil an ideal pasture species. To effectively manage birdsfoot trefoil in mixed pastures, heavy grazing pressure may be needed in the spring to reduce lush grass growth and allow trefoil to compete better with grasses. Continuous grazing is not recommended because birdsfoot trefoil regrowth depends on energy supplied by top growth. Birdsfoot trefoil is similar in palatability to alfalfa but produces greater average daily gains for heifers and sheep. To improve winter survival and growth the following spring, a fall rest period is needed to allow root reserves to accumulate.

Loss of quality with maturity is less pronounced with birdsfoot trefoil than alfalfa; however, leaf loss during haymaking may be greater than alfalfa. Birdsfoot trefoil is not as resistant as alfalfa to Fusarium-type diseases; therefore, individual birdsfoot trefoil plants will not survive as long as alfalfa. To maintain a stand of trefoil, a management system that allows the trefoil to reseed itself is necessary.

Lespedeza (Kummerowia striata Thunb. and Kummerowia stipulacea Maxim.)

Lespedeza, also known as Japan clover, is an annual forage crop native to Japan and the Far East (Fig. 6). First introduced into the United States in 1919, lespedezas are grown in a wide belt extending from eastern Texas, Oklahoma, and Kansas into southern Iowa and eastward to the Atlantic Coast. Cultivation of lespedeza is limited in the western United States by low rainfall; production in the north is limited by the plants’ inability to set seed before a killing frost. In northern latitudes, the seasonal duration of extended photoperiod is too short for plants to flower properly, and cooler fall temperatures slow seed maturation.

K. striata or “striate” and K. stipulacea or “korean” are fine-stemmed leafy herbaceous legumes with shallow taproot systems. Plants can grow to 40–50 cm tall if not cut during the season. Lespedezas do not store carbohydrate reserves in their roots, instead they rely on their ability to persist through reseeding. Establishment is done through

Forage and Rangeland Production

Fig. 6. Lespedeza, Kummerowia striata Thunb. and Kummerowia stipulacea Maxim.

broadcast seeding without covering in late winter, allowing frost heaving to work the seed into the soil. In properly managed pastures, lespedeza is able to reseed itself.

Lespedezas grow well on eroded, acidic soils that are low in phosphorus under conditions where other legumes cannot survive, making them valuable for low-input pasture systems. They do best, however, on well-drained, properly fertilized soils. They are excellent pasture legumes for summer grazing when cool-season pastures are unproductive. They do not produce large amounts of forage, but the produced forage is high quality and free of bloat hazard.

Lespedezas are susceptible to bacterial wilt [Xanthomonas campstreis pv. lespedezae], which is a problem in the northern extent of lespedezaâ&#x20AC;&#x2122;s range. Root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood], soybean cyst nematode (Heterodera glycines Ichinhoe), and sting nematode (Belonolaimus gracilus Steiner) use this plant as a host as well. In contrast, lespedezas have few insect pests able to cause significant damage.

Important Forage Grasses in North America: Cool-season Grasses Orchardgrass (Dactylis glomerata L.) Orchardgrass is native to Europe, North Africa, and East Asia (Fig. 7). It was introduced to the United States around 1750 and was often found growing in shady areas, including orchards where it probably got its name. It is used throughout the United States and Canada in areas of moderate-to-high rainfall, moderate winters, and warm summers. It is one of the major grass species for pasture in the northeast and north central United States. It is well known for its ability to recover quickly after defoliation from either grazing or mowing.

Orchardgrass tends to grow in clumps to produce an open sod. Its light green to dark green-blue leaves are fold-

Fig. 7. Orchardgrass, Dactylis glomerata L.

ed in the bud and are V-shaped in cross section. Orchardgrass grows up to 2 m tall. Inflorescences are 8â&#x20AC;&#x201C;15 cm long and composed of spikelets bearing 2â&#x20AC;&#x201C;5 florets. Carbohydrates are stored in the lower parts of leaves, tiller bases, and fibrous roots.

Orchardgrass is usually cut at the early-heading stage for hay. Quality declines quickly after heading occurs, so timing of harvest is important for high-quality forage.

Planting orchardgrass with a vigorously growing legume such as alfalfa is an acceptable practice that can lower the need for supplemental nitrogen applications. Ladino or white clovers are also suitable for combining with orchardgrass for pasture. Orchardgrass is better suited to rotational than to continuous grazing. It is easily established when seeded in early spring or late summer. Most diseases of orchardgrass affect the leaves, where part or all of the foliage may be destroyed. The best way to manage diseases is by planting resistant cultivars. Insect damage generally has little importance in orchardgrass production.

Smooth Bromegrass (Bromus inermis Leyss.)

Smooth bromegrass is the most widely used of the cultivated bromegrasses (Fig. 8). Native to Europe and Asia, it is adapted to most temperate climates. Because it can survive periods of drought and extremes in temperature, smooth bromegrass is well adapted to the central United States and northward into Canada. Smooth bromegrass is a leafy, sod-forming, perennial that spreads underground by rhizomes. Forage quality compares well with other cool9

Forage and Rangeland Production

Fig. 8. Smooth bromegrass, Bromus inermis Leyss.

Fig. 9. Tall fescue, Fescuta arundinacea Schreb.

season grasses. With abundant soil nitrogen, crude protein percentage in this grass forage is very high during early plant growth. Protein decreases rapidly with maturity, and digestible dry matter increases until initiation of seed.

Smooth bromegrass is used in hay production and pastures; however, it does not persist as well as orchardgrass in most pastures. A moist, fertile seedbed is required for good establishment. In the eastern and northern regions of the United States and Canada, it is planted in the spring, often in mixed stands with a legume. Seeding is accomplished with a grassland drill with a seed box designed for planting chaffy and free-flowing seed.

The crop responds well to nitrogen fertilization; however, in planting with legumes, the amount of supplemental nitrogen needed is reduced. Older stands can become â&#x20AC;&#x153;sod-bound.â&#x20AC;? Adding nitrogen to sod-bound stands invigorates old stands and improves yields.

Smooth bromegrass is less preferred recently because it may be highly competitive against other forage grasses.

Grasses, such as orchardgrass and perennial ryegrass that tend to produce higher quality forage and have other more desirable traits, have displaced bromegrass as a favored grass species. But when grazed properly or harvested for hay, it can be a suitable forage species.

Tall Fescue (Fescuta arundinacea Schreb) Tall fescue is native to Europe and was introduced into North America around 200 years ago (Fig. 9). Tall fescue is widely adapted, but it grows best in the transition zone that separates the northern and southern regions of the United States. Tall fescue is tolerant of poorly drained 10

Fig. 10. Timothy, Phleum pratense L.

soils, even during winter. It does quite well in wet pastures and is used extensively as the grass constituent of mixtures in irrigated pastures throughout the western intermountain region from southern California to northern Washington. Tall fescue grows best in moist fertile soils that are heavy-to-medium in texture. Despite its adaptation to higher soil moisture conditions, tall fescue does have moderate drought tolerance. Underground stems and thick stands, as well as tough, coarse roots of tall fescue produce an even sod when mowed or grazed. Tall fescue has dark green ribbed leaves that grow to 80 cm tall, and seed stalks that can grow to 150 cm tall, producing five to seven seeds per spikelet.

Tall fescue can provide good pasture when seeded with a legume. Forage quality of the grass is equal or superior to other cool-season grasses grown in the southern United States during spring, fall, and winter if provided with adequate nitrogen. It can also be used for hay when grown with a companion legume. In pastures, tall fescue can be damaged if grazed too soon after planting or if it is trampled while soil is wet and young roots are damaged or torn. Heavy close grazing can be sustained for short periods of time, but stands require time to recover.

A major concern for tall fescue producers is endophyte infection. Endophyte-infected fescue causes fescue foot, bovine fat necrosis, and fescue toxicosis. Fescue foot usually occurs in cattle during winter grazing. It causes constriction of the blood vessels in the extremities of the cattle and leads to tenderness of the hind legs while walking; the condition can develop into gangrene or necrosis (sloughing off) of the tail, ears, and feet. Fescue toxicosis is

Forage and Rangeland Production usually not fatal, but it causes significant economic losses because of poor condition of grazing animals. Growing tall fescue with a legume can minimize endophyte infection. Several varieties are available on the market that are “endophyte free”; other endophyte friendly varieties are also available that are endophyte infected, but do not have ergot alkaloid toxicity.

Timothy (Phleum pratense L.) Timothy is a cool-season forage grass widely grown in cool, moist regions of the United States, Canada, and Europe (Fig. 10). A native of North America, timothy was brought under cultivation in the early 1700s. Timothy does not tolerate drought conditions, but it is one of the most winter-hardy, cool-season forage grasses.

Timothy can reach 1 m in height. Its twisted, flat leaf blades are usually hairless, except around the leaf collar.

The compact and swollen lowest internodes are referred to as haplacorms, or corms. These corms act as a carbohydrate reserve and play an important part in regrowth and persistence. A shallow fibrous root system makes timothy poorly suited for droughty areas. Timothy is not well suited for multiple cuttings (three or more), thus its utility is limited to the northern United States and Canada, where only two cuttings per year are the norm.

Timothy is a popular forage grass in areas where it is adapted and has few insect pests or diseases. It can be planted in the spring or early fall, and works well with other species in mixed plantings. Timothy produces good yields of high-quality forage when harvested at the early heading stage. It is a popular hay crop for horses, and many racetracks pay well for high-quality timothy hay.

Important Forage Grasses in North America: Warm-Season Grasses Switchgrass (Panicum virgatum L.) Switchgrass is a tall, perennial, sod-forming, warmseason grass that is native to North America (Fig. 11). It grows from 0.5 to 2.0 m tall and spreads slowly by short rhizomes. Its roots reach depths of up to 3 m, giving this grass excellent drought tolerance. High yield, vigorous seedling growth, and high seed yield make it one of the easiest native grasses to cultivate. Switchgrass can be grown in poorly drained soils with low-to-medium soil fertility, and it can tolerate a pH range from 5.4 to 8.2. Thus, it may be a good choice for seeding in areas that are not suitable for other forage crops. Lowland ecotypes, found in floodplains, are generally taller and more rust (Puccinia graminis) resistant.

They also grow more rapidly and usually produce more of

Fig. 11. Switchgrass, Panicum virgatum L.

a bunch-type growth than the upland ecotypes.

Switchgrass seed is quite dense and slick, which makes making planting easy. Switchgrass seedlings are vigorous and competitive. When planting switchgrass with other forage species, it is recommended that no more than 20% of the mixture by seed count be switchgrass.

Switchgrass can be grown for hay or used as summer grazing in pasture systems. Switchgrass is also noted for its high productivity. It produces so much biomass so quickly that it has generated interest for the production of bioenergy through fermentation to produce ethanol or co-firing with coals.

Big Bluestem (Andropogon gerardii Vitman) Big bluestem is best adapted to well-drained loams with high fertility levels, but it tolerates a wide range of soil types and has been found throughout the entire Mississippi valley northward into Canada (Fig. 12). Except for one ecotype or subspecies adapted to the sandhills of Nebraska called “sand bluestem,” it does not tolerate dry/ sandy soils. Big bluestem was once the dominant species of the tall-grass prairie of central United States, making up as much as 80% of the vegetation in some sites. Big bluestem can grow 1–2 m tall, and it most often grows in clumps with extensive root systems as deep as 2.5 m. Its grayish blue stems in autumn give this grass its common name. Big bluestem’s other common name “Turkey’s foot” comes from the 2–9 digitate racemes resembling a turkey’s foot formed by the purple inflorescences.

As a pasture grass, big bluestem is highly palatable and very nutritious in the early stages of its growth. It grows vigorously once established, withstands close grazing, 11

Forage and Rangeland Production seeded into native stands of grasses by increasing available forage early in the season. The tolerance of crested wheatgrass to heavy grazing pressure makes it a valuable addition to warm season grass pastures. High forage quality in early vegetative regrowth declines rapidly after early spring due to leaf loss. Heavy grazing during the spring and early summer are recommended for optimal production.

Selected References: 4, 5, 6, 29, 152 Richard Leep, James DeYoung,and Doo-Hong Min

Ecology and Physiology of Forage Crops Fig. 12. Big bluestem, Andropogon gerardii Vitman (Moser, 1995).

and recovers from excessive grazing if protected during the early part of the season. It cross-pollinates to create awned seeds of varying pubescence.

Crested Wheatgrass (Agropyron spp.)

These species are native to the steppe region of western Russia and southwestern Siberia (Fig. 13). Crested wheatgrass was introduced into North America in 1906 and is particularly well adapted to the northern and central Great Plains. Crested wheatgrass is a long-lived perennial that forms erect culms of 15â&#x20AC;&#x201C;100 cm tall. It was used to stabilize the soil of the Dust Bowl region when nothing else would grow on the devastated range and cropland. Crested wheatgrass has excellent drought resistance and excellent seedling vigor. In its area of adaptation, stands of crested wheatgrass remain productive for many years. It produces abundant forage and is used primarily for grazing rather than for hay production. It increases grazing capacity when

Fig. 13. Crested wheatgrass, Agropyron spp.

12

Forage and rangeland plant species are grown on approximately one-third of the United States landscape.

These plants form the basis for the ruminant livestock industry in the United States and Canada, providing on average 63% of the nutritional needs of all livestock. The term â&#x20AC;&#x153;forageâ&#x20AC;? refers to the use of high-fiber plant material as livestock feed, and it is not limited to any particular group of species. For example, maize is a forage crop when grown for silage. This chapter focuses on the physiology and ecology of the largest group of forage species grown: the perennial grasses and legumes.

The response of forages to injurious arthropods depends on several things, including the physiological status of the plant, the intensity and duration of infestation, and the prevailing environmental conditions. Perennial forage plants are unique in several ways when compared with annual crop plant species. They have mechanisms that permit them to survive complete defoliation (by mowing for hay or livestock grazing) at monthly intervals during haymaking or grazing. Few plant species possess this tolerance to intensive defoliation. In addition, these perennial forage species must tolerate stresses associated with winter weather, as well as those that occur during summer. The physiological mechanisms that allow perennial forages to survive this array of stresses are complex, and not yet completely understood. A simplified conceptual description of how perennial forages function and grow is used to illustrate some of these mechanisms.

Conceptual Description of Forage Plant Growth and Stress Tolerance To aid understanding of the complex responses of forage plants to various types of stressors, I have simplified the physiology and growth of a perennial forage plant into four primary processes: net photosynthesis (Net Ps), dark respiration (Rd), growth, and stored reserves (Fig. 1). This

Forage and Rangeland Production depiction of plant function is relatively simple: When leaves are present, sugars produced by net photosynthesis are used to support dark respiration and growth, and any excess is stored for later use. After hay harvest or grazing, net photosynthesis is low for a week or two, and stored reserves are used for dark respiration and growth until leaf development on regrowing shoots can meet plant needs.

Reserve storage is a key feature of perennial forages that buffers growth and dark respiration from changes in carbohydrate supply, and ultimately enables these plants to survive stresses like winter weather, defoliation because of harvest, or insect attack.

By understanding these processes and how they interact, it is possible to predict how forages adapt to prevailing or impending stresses including that caused by injurious arthropods. That knowledge can be used to implement management strategies that minimize the consequences of the stress.

Net Photosynthesis More than 90% of plant dry weight is derived from one key process, photosynthesis. The remaining 5–10% of plant dry weight is obtained from the soil as mineral nutrients. Therefore, factors that influence photosynthesis can have a dramatic impact on forage yield. The term “net photosynthesis” describes gross or total photosynthesis minus carbohydrate lost via another process called photorespiration (as the name implies, light-driven CO2 release). This latter process occurs in cool-season forages that have the C3 photosynthetic pathway (described below). Photorespiration decreases gross photosynthesis by an average of 30%, and as a result, reduces forage yield potential of cool-season forages having the C3 photosyn-

Fig. 1. A simple model illustrating how net photosynthesis (net Ps), dark respiration (Rd), growth and reserve storage interact in perennial forage plants. Two scenarios are presented. During late forage regrowth when photosynthesis is high and reserve storage high versus early regrowth when photosynthesis is low and reserves are being used for respiration and growth.

thetic pathway. Warm-season forages that have the C4 photosynthetic pathway do not photorespire and as a result have a very high yield potential. Examples of forage species with these contrasting photosynthetic pathways are provided in Table 1 and underscore the high productivity and warm-season adaptation of forages that have C4 photosynthesis.

It is important to realize that the type of photosynthetic pathway a forage plant possesses greatly influences its seasonal productivity (Fig. 2). Warm-season (C4) forages grow rapidly, are very high yielding in summer, but have reduced forage production in early spring and autumn. By comparison, cool-season (C3) forage species grow rapidly in spring and autumn, with reduced growth in midsummer. This difference in seasonal growth is due primarily to low rates of photosynthesis in C4 forages at low temperatures <50 ºF (10 ºC), and the reduced photosynthesis of cool-season (C3) forages in summer as temperatures exceed 77 ºF (25 ºC).

Dark Respiration (Rd) This process uses oxygen and sugars to produce ATP, the form of energy required by living cells. If either sugars (from photosynthesis or stored reserves) or oxygen become limiting, there is risk of cell (organ or plant) injury or death. For example, flooding in the summer often injures or kills sensitive species such as alfalfa or maize because the excess water prevents oxygen flow to roots and results in plant death.

Dark respiration has two broad functions in plants: Table 1. Representative forage species possessing the C3 (cool-season) or C4 (warm-season) photosynthetic pathways Legumes

Grasses

C3, Coolseason species

Alfalfa Red clover White (Ladino) clover Birdsfoot trefoil Vetch Sweetclover

Tall fescue Orchardgrass Timothy Ryegrass Smooth bromegrass Reed canarygrass Wheatgrasses Kentucky bluegrass

C4, Warmseason species

No C4 forage legumes

Switchgrass Indiangrass Bermudagrass Big bluestem Bahiagrass Maize (corn) Sorghum

13

Forage and Rangeland Production

Fig. 2. Comparison of seasonal growth rates of cool-season (C3) and warm-season (C4) forages in a temperate climate.

first, in growth and development of new cells, tissues, and organs; and second, in providing the energy needed for cell maintenance and repair. This latter function includes repairs required after insect and plant pathogen injury. In addition, perennial plants are alive and respiring throughout winter even though no growth is occurring. Therefore, it is important that these perennial forages accumulate sugar reserves in autumn if they are to survive winter.

Dark respiration can consume an enormous amount of sugar in growth and maintenance processes. On average, 45% of the sugar produced by a plant during the day via photosynthesis is lost as dark respiration each day. Thus, even small increases in dark respiration rate can reduce the amount of carbohydrate that is available for growth and stored reserves (Fig. 2). Increasing temperatures during summer generally result in higher dark respiration rates, which often reduce the amount of sugar available for storage. Low reserve levels can reduce regrowth rates and compromise stress tolerance, which is one reason cool-season (C3) forages in particular die during summer in hot environments.

Growth Dry weight accumulation occurs because of photosynthesis and mineral nutrient acquisition. It results from the coordinated efforts of two processes, cell division and cell expansion, localized in meristems. The location of these meristems differs somewhat between grasses and legumes (Table 2). Understanding which meristems result in growth in each species and where these meristems are located are important concepts for successful forage management.

In grasses and legumes, root elongation occurs as a result of a meristem located at the root tip or apex. Perennial forage legumes, with their carrotlike taproots, also grow in diameter because of a lateral meristem located at the junction of the bark and wood tissues in the taproot.

14

Stem growth in both species occurs in similar meristems. New nodes and internodes are produced by a shoot apical meristem located at the apex of the stem. Most visible stem growth, however, occurs in stem intercalary meristems localized in short, but rapidly growing stem internodes near the stem apex.

In grasses and legumes, new leaves are initiated in the shoot apical meristem, however, most visible growth occurs in different meristems. In grasses, the leaf intercalary meristem is located at the basal 1/2 in. (1 cm) or so of elongating leaves. This places the key meristem involved in growth of forage grasses at or near the soil surface—an ideal location for plants subjected to grazing or close mowing. By comparison, forage legume leaves increase in surface area because of cell division and elongation occurring in a marginal meristem present along the edge (“margin”) of expanding leaves. Because the leaf and stem meristems of legumes are often elevated aboveground, grazing or mowing usually removes them and abruptly arrests forage legume growth and development. The exception is white clover that possesses stolons (Fig. 3), which positions leaf and stem meristems near the soil surface making this species particularly tolerant of grazing.

The final meristem of interest is the axillary meristem located at the leaf–stem juncture. Axillary meristems located near the soil surface on legume crowns or in stem bases of grasses (Fig. 3) are very important because they develop into new shoots and tillers when growth resumes in spring and following haymaking or grazing in summer. The abundance of meristems, their locations, and the manner in which they function are key features that enable forage grasses and legumes to survive winter, to grow in spring, and to regrow after forage harvest in summer. Damage Table 2. Comparison of meristems involved in growth of various organs of forages.

Organ Legumes

Grasses

Root

Apical-root elongation Lateral-increased root diameter

Apical-root elongation

Stem

Apical-initiates new stem tissue Stem intercalaryelongates stem Axillary-branching, new shoots

Apical-initiates new stem tissue Stem intercalaryelongates stem Axillary-branching, new tillers

Leaf

Apical-initiates new leaves Apical-initiates new leaves Marginal-growth in area Leaf intercalary-elongation of grass leaves of dicot leaves

Forage and Rangeland Production to meristems caused by injurious arthropods can reduce growth and compromise plant survival even if high reserve levels are present. Forages need a source of energy (net photosynthesis or stored reserves) and functional meristems to tolerate stress and regrow following stress alleviation.

Cell growth in meristems of forage plants is influenced by many factors, but reduced water supplies often limit shoot growth during the growing season. Growth can be reduced markedly even with well-watered conditions in summer due to mild, mid-day water stress. Photosynthesis usually continues under mild water stress, and the sugars produced accumulate in storage organs for later use (Fig. 11). When the water stress is alleviated (often at night), rapid cell growth occurs using the sugars and other previously stored nutrients as substrates.

Stored Reserves The last component of this conceptual description is stored reserves. During late vegetative and early reproductive development sugars, polysaccharides, storage proteins, and other nutrients essential for survival and subsequent growth of forages accumulate. These stored reserves are used later during periods of time when photosynthesis, nitrogen fixation, or nutrient uptake cannot meet plant needs (i.e., after harvest). These stored reserves accumulate in organs at or below the soil surface. This protects them from damage caused by grazing or haymaking. Examples of storage organs include: taproots and stolons in legumes; and stem bases, stolons, and rhizomes in grasses (Fig. 3).

The type of reserve carbohydrates accumulated varies with species, but they are easily classified into categories depending on whether plants are grasses or legumes, and whether they are cool- (C3) or warm-season (C4) (Table 1).

Cool-season forage legumes accumulate starch in large, carrot-like taproots, or in horizontal aboveground stems called

stolons (Fig. 3). Perennial, warm-season forage grasses also accumulate starch, but in stem bases, stolons, or below-ground horizontal stems called rhizomes. Cool-season perennial grasses accumulate a polymer of fructose called fructan in stem bases, stolons, and rhizomes. Fructan may be preferred over starch in cool-season species because it is thought to enhance winter survival. It is important to note this species-dependent variation in polysaccharide form so that appropriate analytical methods can be used to estimate stored carbohydrate levels. In addition to accumulating stored carbohydrate, certain forages accumulate large amounts of protein in storage organs. For example, in alfalfa, these vegetative storage proteins serve as a source of nitrogen for regrowing shoots when growth is initiated in spring and during shoot regrowth after harvest in summer.

For most perennial forage grasses and legumes a distinct pattern of stored reserve use and re-accumulation occurs after mowing or grazing. Harvesting reduces photosynthesis to values near 0, and with it, nitrogen fixation (Fig. 4). Stored reserves (carbohydrates and vegetative storage proteins) are mobilized over the first 14 d after harvest to provide the sugars and nitrogen needed by regrowing shoots, and the sugars required as energy for dark respiration of roots, crowns and other tissue not removed by mowing or grazing. Between 14 and 21 d after harvest, leaf area increases as shoots regrow and whole-plant photosynthesis is sufficient to meet the carbohydrate needs of growth and respiration. From 21 to 35 d, stored reserve levels rise rapidly as excess sugars from photosynthesis (beyond those needed for growth and respiration) reaccumulate. Harvesting or grazing can occur again after 35 d because reserve levels have returned to high concentrations. After mowing or grazing on Day 35, the cyclic pattern of reserve use and restoration is repeated.

Agronomists often use flower appearance on forage

Fig. 3. Sketches of a forage grass plant and a forage legume plant illustrating the organs involved in reserve storage.

15

Photosynthesis, N Fixation, or Stored Reserves

Forage and Rangeland Production

Harvested

Photosynthesis and Nitrogen Fixation

Stored Reserves

OK to Harvest Again

Days After Defoliation

Fig. 4. Effects of harvesting on photosynthesis, nitrogen fixation, and stored reserve level of a perennial forage legume like alfalfa. Photosynthesis and nitrogen fixation decline immediately after plants are mowed on Day 0. Between Days 0 and 14 stored reserve are used for regrowth and dark respiration. Reserves re-accumulated rapidly after Day 21 as excess sugars from photosynthesis are stored for later use. Plants can be harvested again on Day 35 or later because reserve levels are sufficiently high for regrowth to occur. The impact of defoliation on photosynthesis, and reserve use and reaccumulation in forage grasses is similar, but grases do not fix nitrogen.

legumes as an indication that high reserve levels have accumulated in storage organs, and the plants will tolerate mowing or grazing. Although allowing plants to grow extensively until flowers appear has a positive impact on reserve accumulation, this advanced maturity reduces forage quality, a topic discussed in more detail below.

Although reserve storage occurs in almost all perennial forages in autumn because reserves are required for winter survival, not all forage species accumulate high reserve levels in summer as shown in Fig. 4. As a result, certain species must be managed carefully during the growing season to prevent injury or plant death. For example, birdsfoot trefoil does not reaccumulate stored reserves in summer, and producers must mow or graze these plants leaving a tall (4â&#x20AC;&#x201C;6 in. [10â&#x20AC;&#x201C;15 cm]) stubble above the soil surface. This tall stubble has leaves whose photosynthesis provides the sugars needed for dark respiration and shoot regrowth. Close grazing or mowing completely defoliates trefoil, and plants are weakened or die because neither photosynthesis nor stored reserves are available to provide the energy needed by dark respiration and growth.

Factors that interfere with reserve reaccumulation can have practical consequences for forage regrowth and persistence. For example, reserve levels are often very low between 7 and 21 after mowing or grazing because of the extensive harvest-induced reserve depletion (Fig. 4).

Stands can be severely weakened or even lost if grazed 16

close to the soil surface at weekly or even biweekly intervals because few reserves are present to provide the sugars needed for growth and respiration. Certain forage species, including white clover, birdsfoot trefoil, and Kentucky bluegrass tolerate frequent mowing or grazing, in part because they have leaves near the soil surface with continued photosynthesis and are not completely dependent on stored reserves after harvest.

Information about stored reserve accumulation patterns also influences how legumes and grasses are combined to form forage mixtures. Planting species in mixtures so that reserve use and reaccumulation are in synchrony, and that can be managed to the benefit of all species, works well for persistence. However, using forage mixtures with species where reserve use and accumulation are not in synchrony often results in one or more species in the mixture being eliminated.

Translocation Translocation is the movement of sugars, amino acids, and other constituents within specialized cylindrical cells (phloem) in leaves, stems, and roots of plants. This energy-consuming process is very important to forages because of the need to move materials from sites of synthesis called sources (i.e., sugars from leaves) to sinks where they are needed for growth, respiration, or where they are stored. The translocation process is represented in Figure 1 as arrows.

During late regrowth, sugars flow from leaves (the primary source) to other components of the plant as depicted in the model that are sinks for sugars and other nutrients. During early shoot regrowth after forage removal sourceâ&#x20AC;&#x201C;sink relationships change, and stored reserves now become the primary source of sugars until leaves regrow and photosynthesis resumes.

Certain injurious arthropods, most notably leafhoppers, interfere with translocation by feeding directly on the phloem and blocking vascular channels. This prevents the transport of sugars and other nutrients to storage organs and causes sugars to accumulate to high levels in leaf tissues. Ultimately sinks are deprived of the sugars and other nutrients they need, and growth and stored reserve accumulation can be reduced.

Forage Quality Forage quality is an important consideration to ruminant livestock managers and forage producers. Whether measured as high digestibility or low fiber, or as improved animal performance, forage quality characteristics can vary considerably because of plant species and cultivar

Forage and Rangeland Production selected, stage of growth, biotic and abiotic stresses, and management practices. In general, legumes have higher forage quality than do grasses, and quality of cool-season (C3) grasses usually exceeds that of warm-season (C4) grasses. Under most circumstances, forage leafiness is positively associated with high forage quality. With advanced maturity, the leaf:stem ratio of forages declines, leading to reduced forage quality. The highest forage quality is obtained with immature forage (i.e., harvested or grazed every 2â&#x20AC;&#x201C;3 wk), but forage yield at this stage of growth is low and plant persistence is poor because stored reserve levels are low (Fig. 4). Managers often must find a compromise between yield, quality, and persistence by harvesting legumes at the onset of reproductive growth (buds present, first flower appears) when forage quality is good, yield is good, and reserves are high enough for plants to persist.

Injurious arthropods can alter forage quality. Those that remove leaf area reduce the leaf:stem ratio and generally result in lower forage quality. In contrast, leafhopper feeding on stems often reduces stem growth more than leaf growth. Under these circumstances, forage digestibility may increase because the leaf:stem ratio is increased.

Injurious Arthropods and Forage Physiology The simple conceptual description in Fig. 1 aids understanding of how forage plants grow, adapt to harvesting, and survive abiotic stresses such as winter. It also can improve understanding of how plants respond to injurious arthropods, and in certain cases, fail to grow and/or persist. For example, clover root curculio and clover root borers damage taproots of clovers and alfalfa. This leads to several problems for these forage legumes. First, there is the direct feeding damage to the surface and interior of taproots, the primary organ where stored reserves accumulate. This may interfere with accumulation of nutrient reserves during late forage regrowth and subsequently limit the availability of reserves after mowing or grazing.

Second, feeding wounds allow bacteria and fungi direct access to root tissues normally protected by the root surface. This can result in root rot and other diseases that reduce taproot function and storage capability. Taken together these biotic stresses can lead to severe injury and plant death.

The simple description of forage plant physiology (Fig. 1) also can explain the effect of aboveground injury caused by injurious arthropods. For example, alfalfa weevils reduce forage yield and quality by consuming leaf

tissues. Weevils also can damage the axillary buds that develop into new shoots. The negative impact of this insect extends beyond these direct effects, however, because sugar production via photosynthesis is reduced in proportion with leaf area loss. Less sugar production can reduce root reserve accumulation, slow subsequent shoot regrowth after mowing or grazing, and lead to reduced forage yields at later harvests. Severe defoliation by weevils may result in extensive use of stored reserves and injure or kill plants.

Selected References: 5, 6, 77 Jeffrey J. Volenec

Production Practices Forages are produced on more than 1 billion acres (430 million ha) of rangeland, cropland, and pastureland land in the United States and Canada contributing an estimated $24 billion of agricultural income to the national economy of the United States alone. Forages are the primary nutrition base for North American livestock industry supplying about 90, 80, and 60% of the nutrients consumed by sheep, beef cattle, and dairy cattle, respectively. Forages supply about 60% of the total intake required for the production of poultry. Hay and silage are produced on about 73 million acres (30 million ha) in the United States including 6.4 million acres (2.6 million ha) of corn and sorghum silage, 6 million acres (2.4 million ha) of alfalfa haylage, 25 to 28 million acres (10 to 12 million ha) of alfalfa hay is produced on another, and 33 to 36 million acres (13 to 15 million ha) of other grasses and legumes in monoculture and mixed species stands that are harvested for conserved forage. More than 15 million acres (6 million ha) of hay and silage are produced annually in Canada. These conserved forages provide a reliable supply of nutrients for livestock during periods when grazing is not possible.

Although livestock production is a traditional and valued used of forages, other uses also are important. Perennial forages in pastures and rangelands contribute to more rural landscapes than do intensive agricultural systems by reducing soil erosion, lowering agrochemical usage, and providing and enhancing wildlife habitats. Forages on rangelands and pastures provide food and habitat for numerous wildlife species, including deer, pronghorn antelope, elk, bison, many smaller game and nongame mammals, and birds. Forage plants play an important role in enhancing water quality and maintaining adequate supplies of clean water for urban areas and irrigated agriculture. Meeting the environmental needs of the diverse landscapes in which they grow 17

Forage and Rangeland Production is a critical function of many forage-producing ecosystems.

Forage production on rangelands and pastures plays a role in maintaining and improving biodiversity. Associated with these functions is an array of additional demands placed on these natural resources, including camping, hiking, fishing, hunting, and other recreational activities.

Forage crops considered in this discussion include various species and cultivars of grasses and legumes produced on lands receiving periodic cultivation and annual inputs such as fertilizers and irrigation to establish and maintain introduced forage species. This includes lands classified elsewhere as pasturelands (including permanent pasture) and croplands (and cropland pastures). Rangeland is land on which indigenous or introduced plant species, including forages, are managed as a natural system. Rangelands are characterized by their reliance on grazing to fulfill management goals. Forage seed production is a specialized industry that provides sufficient seed of good quality to ensure continued production of forages for all required uses.

Each forage species has optimal requirements for establishment, growth, persistence, and yield of biomass. However, because few environments provide ideal conditions, the impact of existing conditions on forage production may vary, and decisions made by producers concerning management and utilization are fundamental to achieving consistent economic returns. The following is a discussion of establishment and production practices used in forage, rangeland, and seed production systems (see outline in Table 1). Information for production of particular species in specific regions or under a given set of conditions should be sought from local experts.

Forage Production Establishment Practices The initial step in the management program of any crop species is establishing a healthy, vigorous stand.

Establishing productive forage stands is dependent on a combination of interacting factors including species and cultivar selection, site cropping history and preparation, soil fertility, and planting method and scheduling.

Species and Cultivar Selection. Selecting the forage species and cultivar, or the mixture of species and cultivars, for production is an important early consideration that affects all future production and management decisions. To establish a high-yielding, persistent stand, the adaptations of the forage species planted should be matched as closely as possible to the climatic conditions, moisture availability, soil characteristics, and the intended use of the crop.

Forage yield is an important consideration in species 18

Table 1. Outline of production practices.

Forage Production Establishment practices Species and cultivar selection Seeding Soil fertility Post-establishment practices Water management Weed and disease management Harvest Forage Seed Production Establishment practices Species and cultivar selection Seeding Soil fertility Post-establishment practices Water management Pollination management Weed disease management Harvest Rangeland Production Establishment Practices Species and cultivar selection Seeding Post-establishment Practices

and cultivar selection. Other factors such as market considerations and seed availability must be investigated. Other important factors include forage palatability and ability to meet nutritional requirements of grazing species; the ability to withstand the expected grazing intensity, and to provide forage in sufficient quantities when needed; and the desired competitive ability and persistence.

Because constraints on forage production are often magnified when soil moisture is limited, seasonal moisture availability must be a consideration in selecting which species to plant. What is the expected seasonal precipitation?

Lack of moisture can be overcome if irrigation is available.

Too much moisture however, is difficult to overcome in high rainfall areas and can be a limiting factor for species adapted to dry conditions and/or well-drained soils.

Forage species should be compatible with the intended use. Is the primary goal of planting to increase forage production, to increase forage quality, to accommodate a particular seasonal or longer term grazing need, or to provide erosion control? Is the forage to be grazed or will it be harvested for hay or silage? If it is to be grazed, what is the grazing schedule? What species, kind (e.g. beef vs. dairy cattle), age, and stocking levels will be used in the grazing regime?

Establishing mixed stands is more difficult than establishing pure stands because more management is required to maintain the desired grass/legume balance. Weed

Forage and Rangeland Production management is more difficult because fewer herbicides are available for use in grass–legume mixtures. Harvesting forage for hay or silage may be difficult if the component forage species do not mature synchronously. Harvest by grazing may also be more difficult as a result of differential palatability of component species.

Despite the difficulties that grass–legume mixtures offer, many potential advantages are possible over pure stands. Mixed stands, when established, are more competitive and fill more of the available space than pure stands. This reduces invasion of weeds and need for weed control. Forage yields of mixed stands can be as high as or higher than pure stand yields, particularly in nonirrigated rangeland conditions. Adding legumes to grass can improve forage nutritional content. Adding legumes to grasses also can reduce the amount of nitrogen fertilizer requirements as a result of nitrogen fixation by legume species. Grass–legume mixtures reduce bloat problems associated with pure legume stands and may have greater adaptability to a range of soil and moisture conditions.

Mixed stands consisting of single legume and single grass species are easier to establish and maintain than more complex mixes. Simple mixtures tend to be grazed more uniformly and show little or no yield penalty compared with complex mixes. In addition, because of selective grazing pressure and competitive interactions among component species, complex mixtures tend to revert to simple mixtures within a few seasons after establishment.

Seeding. Seedbed preparation is critical; it provides the environment in which seeds germinate and in which the resulting seedlings grow and develop. A firm, weed-free seed bed provides good seed–soil contact, good moisture distribution near the soil surface, good root penetration to support young seedlings; and it helps to control seeding depth. For conventional plantings, a suitable seedbed can be obtained by plowing to bury surface debris, followed by disking and harrowing to produce a smooth, firm surface with particles no larger than ½ in. (1.3 cm) in diameter.

Weeds may be removed using tillage either alone, or in conjunction with the application of herbicides. Land cultivated before planting should be packed to preserve moisture, and to help regulate seeding depth.

Planting in conventional seedbeds may be accomplished by either broadcasting or drilling the seeds into the prepared seedbed. Broadcast seeding disperses the seed over the seedbed, using spin broadcast, dribble, or pneumatic spreaders. With all three types of broadcast seeding equipment, it is a common practice to mix the seed with a carrier, such as sawdust or rice hulls to give a more uniform seed distribution. After the seed has been broadcast, it is

incorporated into the soil by a shallow tillage operation (1.5–2.5 in. [4-6.5 cm]), followed by harrowing, or pressing the seed into the seedbed with a corrugated roller.

Drilling seed into conventional seedbeds usually provides more uniform distribution and higher percentage of germination than broadcast seeding; it involves shallow planting using a grain drill equipped for small seed. Best results are obtained if drills are equipped with depth regulators and press wheels. Using a culti-packer, or brillion-type, seeder provides good results. A culti-packer seeder consists of a metering seed box mounted between two corrugated rollers. The first set of rollers firms the soil forming shallow corrugations into which the seed is dropped. The second set of rollers covers the seed and firms the soil by splitting the ridges of corrugates formed by the first set of rollers.

For band seeding, a grain drill with a seed box is used.

Hoses from the seed box carry the seed to the soil surface, trailing the drill disks. The drill is used to apply phosphorus fertilizer 1–2 in. (2.5–5 cm) below the soil surface.

The fertilizer is then covered with soil, and the seeds are placed on the soil directly above the fertilizer band. The press wheels, following directly over the seed, then press the seed into the soil surface. Band seeding is particularly advantageous when soil is low in available phosphorus or when planting early into cold wet soils.

No-till seedings can help to reduce soil erosion, conserve moisture required for seedling germination, and reduce fuel and labor costs. In addition, no-till fields provide a preexisting, firm seedbed. Cost may be greater because specialized equipment, such as no-till seed drills, may be required. Late-season seeding into wheat or barley stubble is common because of the flexibility it allows in regard to matching seeding dates to soil and weather conditions.

Before no-till seedbeds can be planted, existing vegetation must be killed using a contact herbicide such as glyphosate or paraquat. No-till seedings are best accomplished using specialized no-till planters (e.g., no-till sod-seeders) that have tools (coulters) for displacing existing crop debris and cutting furrows into which the seed is placed.

These planters may also have press wheels and discs for banding fertilizers with seed.

For most species, seeding depth should not exceed 0.5 in. (1.25 cm) on loamy soils or 1 in. (2.5 cm) on sandy loams or sandy soils or in more arid conditions where drying of the soil surface is a concern. Deeper plantings require an increase in the seeding rate to compensate for increased seedling mortality.

Recommended seeding rates vary among locations and are often provided as a range, based on differences in soils, climate, and establishment methods. Selecting a specific 19

Forage and Rangeland Production rate from the provided range depends on several factors, including soil type and fertility, amount and distribution of moisture, seed bed condition and planting method, and seed quality. Recommended seeding rates for particular forage species and cultivars can best be obtained from local seed dealer representatives, land grant university personnel, and other federal agencies. Some examples are given in Table 2. For broadcast seedings (except culti-packer seeding), the rate recommended for drill seeding should be doubled to account for uneven distribution and planting depth.

The quality of seed is often expressed as pure live seed (PLS) and can be calculated as follows: PLS =% purity × % germination × 100. When seed purity and germination are less than 100%, an adjusted seeding rate, calculated as recommended seeding rate × 100/(PLS).

Several factors affect seeding schedules, including vernalization requirements, climate in the growing area, availability and type (precipitation vs. irrigation) of moisture, soil characteristics, and crop rotation schemes. Cool-seaTable 2. Examples of seeding rates for pure stands of legume and grass when grown as a forage crop or a seed crop.a Forage Seed plantings, plantings, Crop kg/ha kg/ha Legumes Alfalfa, Medicago sativa L. 10–34 Red clover, Trifolium pratense L. 9–11** White clover, T. repens L. 2–5 Birdsfoot trefoil, Lotus corniculatus L. 5–12 Crimson clover, Trifolium pratense L 12–28 Sanfoin, Onobrychis vicifolia Scop.

20–30*** Sweetclover, Melilotus officinalis Lam. 6–9 & M. alba Medik.

Grasses Timothy, Phleum pretense L. 2–10 Smooth bromegrass, Bromus inermis 11–22 Leyss.

Tall fescue, Festuca arundinacea Shreb.

10–18 Kentucky bluegrass, Poa pratensis L. 6–12**

1–2* 2.5–3* 2–5 1–2* 9 5–8* 2–4*

1–1.5* 3–3.5* 3.5–6 1–4*

Seeding rates are provided in kg/ha (=lb/a) Pure Live Seed covering a wide variety of conditions. Actual seeding rates depend on several factors including seedbed condition, soil moisture and availability of irrigation, expected percentage of germination, and method of seeding. aUnless marked with asterisks, data in table is from Barnes et al. 1995. Volume 1. * Anonymous. 1999. Manitoba Forage & Grass Seed Production Guide 1999.

Manitoba Dept. of Agriculture and Food Forage Seed Production Fact Sheet: http:/www.gov.mb.ca/agriculture/crops/forages/bjb00s24.html. ** K. D. Johnson, et al. 1991. Indiana Forage Selection and Seeding Guide for Indiana. Purdue University CES publication AY-253. Agronomy Department, Purdue University, Cooperative Extension Service West Lafayette, IN: Available online at the Purdue Forage Information Website: http://www.agry.purdue. edu/ext/forages/publications/ay253.htm. *** Alberta Agriculture, Food and Rural Development. Establishing Perennial Hay and Pasture Crops. 1994. Fact Sheet 120/22-2 http://www1.agric.gov. ab.ca/$department/deptdocs.nsf/all/agdex130

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son forages are planted primarily from February to early May (late winter to spring) or August to October (late summer to fall). Spring seedings are most common in the northern half of the United States because good moisture is available. Planting too early in this period can expose seeds and seedlings to cool, wet conditions and lead to reduced stands. Planting too late in this period can lead to stand reduction as a result of poor germination and seedling desiccation from summer heat and lack of moisture.

Late summer–fall seedings are common in irrigated areas with long growing seasons or areas with <12 in. (30.5 cm) of rainfall annually. Late summer–fall plantings usually result in less weed competition than winter–spring seedings and can be made after early harvested crops so that full production can be achieved in the following year. Late summer–fall seedings generally have less risk of stand loss due to damping-off diseases; however, seedings should be made early enough to allow at least 6 wk growth after germination before a killing frost.

All legume seeds must be inoculated with the proper Rhizobium spp. before planting. Some seed may be purchased preinoculated, but it must be used before the expiration date. If the seed is beyond the expiration date, it should be reinoculated with a fresh culture before planting. Successful legume inoculation requires coating the seed with large amounts of inoculant that remains on the seed until the seedlings become infected during the germination process.

A number of materials, including water, sugar water, milk, and colas, can be used to coat seeds with inoculant. However, commercial stickers that are much more effective at coating seeds with inoculant are available. Rhizobium cultures purchased for inoculation are degraded by heat and sunlight and should be stored in a refrigerator until use.

In many areas, legumes such as alfalfa are typically planted in pure stands. However, companion crops including several legume and small grain species often are used to give rapid ground cover that prevents erosion and to compete with weed species in new forage seedings. Companion crops, however, also compete with the planted forage for water, light, and nutrients, reducing stand and subsequent yields. Peas, barley, oats, and spring wheat are most commonly used as companion crops. Peas mature early, compete less with forage seedlings than cereal crops, and can be planted at normal seeding rates. Competition from cereals used as companion crops can be minimized by selecting early maturing varieties of short to medium height, planting at reduced rates, and harvesting the companion cereal early. Fertilization practices that promote rapid early growth of the companion crop may increase competition between the companion and forage crops.

Forage and Rangeland Production Soil Fertility. Forages remove large amounts of nutrients from the soil. In grazing situations, many of these nutrients are returned to the soil. In hay and silage production, however, little or no nutrients are returned. Fertility needs of particular soils are best evaluated by using cropping history in combination with analysis of representative soil samples that provide the pH and the nutrient status of the soil. Soil pH is a major determinant of nutrient availability and should be between 6.5 and 7.5 for legume forage species. Most grass forage species are more tolerant of acid conditions and pH should be between 5.5 and 7.0. Liming on acid soils adjusts acidity (raises pH) and supplies essential nutrients (calcium [Ca] or magnesium [Mg]), thereby increasing nutrient availability and increasing forage productivity. Lime should be applied and incorporated before planting. In no-till situations, surface applications of lime may need to be made 1–2 yr before seeding to allow movement into the soil.

Phosphorus (P) and potassium (K) are relatively immobile in the soil and must be worked into the seedbed before or at (e.g., banding) planting. Direct contact between P and seed can inhibit germination and should be avoided.

Demand for P and K is higher for legumes than for grasses. Levels of available P and K should be about 50 ppm and 350 ppm, respectively. Nitrogen (N) is generally not needed in effectively inoculated legumes, but can be applied at 24–48 lb/acre (11–22 kg/ha) to support seedlings until they can synthesize their own N. The demand for N is higher for grasses, and 24–100 lb/acre (22–45 kg/ha) should be applied at planting and top dressed as needed.

Post-establishment practices Water Management. In dry regions, new seedings need irrigation to prevent crusting of the soil surface that could prevent seedling emergence. Because the root zone of newly emerged seedlings is shallow (8–12 in. [20-30 cm]), post-emergence irrigations should be light and frequent to promote root development. Established crops should begin the season with the entire soil profile moist. The amount and frequency of irrigations depend on the crop, soil characteristics, and temperature and wind conditions affecting evapotranspiration levels. Production may be maintained with deep-rooted forages (e.g., alfalfa and tall fescue) with as few as two irrigations during the growing season. Fall irrigation of alfalfa stimulates plant growth that can deplete carbohydrate reserves and is not recommended. Shallow rooted grasses require an even supply of moisture for optimum yields and should receive frequent light irrigations. Forage crops should be irrigated immediately after removal of the crop to insure rapid regrowth.

Weed and Disease Management. The primary focus of weed management for most forages is to reduce initial infestation level by preplant use of mechanical (cultivation) and/or chemical control measures and the use of certified seed. Post-establishment control consists largely of chemical control because broadcast and narrow row seedings often preclude cultivation. Mowing to remove early season growth can be effective in new forage seedings if done 1–2 mo after seeding when most weeds are higher than forage seedlings and have produced flower stalks.

Proper crop rotations help to reduce disease problems by preventing build-up of disease causing organisms in forage fields. Planting disease-free seed and disease-resistant forage varieties (i.e., fusarium wilt or bacterial wilt-resistant alfalfa) will also help to reduce or eliminate many disease problems. Established diseases that threaten crop yield or stand persistence may require treatment with appropriate fungicides.

Harvest. Harvest by grazing of newly established pastures should be avoided until risk of damage from trampling and pulling by livestock is over. It may be possible to graze spring-seeded forages in the late summer or fall, if irrigation is available or summer rains are sufficient to establish a dense vigorous stand. In arid regions without irrigation, grazing may need to be delayed one or more years to ensure a sustainable forage crop.

Established stands may be harvested mechanically for storage or immediate feeding or harvested by grazing. In either case, proper harvest management not only ensures good yields of high-quality forage, but it is also essential for good stand persistence. For optimal forage quality, mechanical harvest is best conducted before the plants are reproductively mature. Harvesting mature plants results in substantial decreases in forage quality compared with earlier growth stages and with minimal gain in forage yield.

For mechanical harvest, forages are generally swathed (cut) and rolled into windrows for curing and baling.

Freshly cut forages contain between 50 and 80% moisture and can be baled when the moisture level is between 15 and 20% depending on the bale size. Under normal conditions, forage can lose up to 30% of its nutritional value while drying in the field. Delays in drying time caused by adverse weather can increase nutritional loses. Use of drying agents and conditioning (i.e., crimping) reduces drying time and increases yield quality potential. Mechanical harvest also includes green-chopping forage for immediate feeding to animals. Forages harvested for silage can be harvested later (at a more mature stage) than forages harvested for hay because more mature forages have reduced moisture content and are more easily fermented.

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Forage and Rangeland Production Forage can be harvested by grazing using several systems. In continuous grazing (i.e., continuous stocking), animals have continuous unrestricted access to forage throughout the grazing period. Continuous grazing is not recommended because it results in reduced yields, increased invasion by weeds, and loss of the more productive forage plants. In rotational grazing, two or more areas within a grazing unit are subjected to alternating periods of grazing and rest throughout the period. When appropriate numbers of animals are used, this system allows uniform grazing of forage in grazed areas, while also allowing plants in rested areas sufficient time for regrowth.

Compared with continuous grazing, rotational grazing allows increased yield and quality of forage for grazing.

Strip grazing is a form of rotational grazing in which animals are confined to an area to be grazed for a relatively short time; for example, when an electric fence is used to confine animals to an area with enough pasture to graze efficiently for one day. The fence is moved each day to allow animals access to additional pasture. In deferred rotational grazing, three or more pasture units are designated and a different unit is grazed first each year. The last unit to be grazed each year is often allowed to set seed before grazing is initiated.

Forage Seed Production Establishment Practices The factors needed to establish and produce profitable forage seed stands are similar to those required for establishing productive forage stands. However, a number of important considerations and requirements are unique to producing seed of forage plant species. Seed is generally produced under certification programs to ensure cultivar identity, genetic purity, and high quality. Certification programs are administered by state departments of agriculture, seed/crop improvement associations, Cooperative Extension Services, or other agencies designated to carry out the requirements of a certification program.

Certification requirements include restrictions on varieties, production areas, crop rotations, and other crop management practices.

Forage crops also are selected for agronomic and quality characters related to their value as forage. These desirable forage characteristics often conflict with seed production needs. For example, a valuable characteristic of a seed crop would be the ability to produce abundant flowers and high seed yields. Because forage crops are selected for their ability to be grazed or harvested for hay or silage, and because they lose nutritional value as plants begin to flower and set 22

seed, some cultivars may be poor seed producers.

Species and Cultivar Selection. Available seed supplies and potential for profitable production must be primary considerations when selecting species and cultivars to plant. Once these requirements have been satisfied, agronomic factors that may affect production must be considered. The species and cultivar/variety selected must be matched to the environmental conditions of the region in which it is to be grown. For example, in species grown in the more northern latitudes or at higher altitudes, the degree of winter hardiness is a primary consideration, as is the ability to produce flowers and mature seed. Crops adapted to shorter days and longer nights that are typical of southern production areas may produce few flowers or produce flowers too late to be of value when planted in northern production regions where during summers, the nights are shorter and days longer.

Seeding. Seedbed preparation for seed crops is similar in most respects to seedbed preparation for forage crop production. It is essential to eliminate weeds in seed production, not only to ensure establishment success, but also to prevent contamination of the future seed crop with weed seeds that could reduce the value of the seed crop or even prevent its sale under certification programs. Seeding methods and equipment described for forage production apply in general to seeding forage crops grown for seed, with a few modifications. Although seed crops are sometimes broadcast seeded (e.g., aerial seeding of white clover in California), most forage seed crops are planted in rows 6–48 in. (15–122 cm) apart using conventional grain drills. Row planting facilitates seed crop growth by allowing better light penetration and a more upright growth form. Row seeding also facilitates cultivations for weed control, roguing operations, application of pesticides for control of weeds, insects and disease pests, and application of irrigation water and post-plant fertilizers.

Seeding depth for forage seed crops is similar to when the crop is grown for forage, requiring burial ¼–½ in. (0.6 to 1.25 cm). Small-seeded species with very small seeds (e.g., timothy) should be buried about ¼ in. (0.6 cm), but can be planted ½ in. (1.25 cm) deep in sandy soils. Larger seeded species (e.g., alfalfa) should be buried about ½–¾ in. (1.2–1.9 cm) deep to as deep as 1 in. (2.5 cm) in sandy situations.

Seed yield rather than plant biomass is the desired end product of seed crop production. For that reason, seeding rates vary depending on the species and variety planted, the time of planting, the presence or absence of a companion crop, and the environmental conditions and soil characteristics of the land to be planted. However, rates are always

Forage and Rangeland Production much lower than those for the same species when grown for forage. For example, alfalfa stands for seed production are planted at 1–2 lb/acre (1–3 kg/ha). When grown for forage production, seeding rates range from 10 to 30 lb/ acre (11–34 kg/ha), depending on the production area.

Companion crops are not usually recommended in seed production because of the increased difficulty involved in establishing a successful stand in the presence of a second plant species. However, in conditions where wind or water erosion of soil is a problem or where weeds are especially difficult to control, companion crops may be considered, especially if moisture and soil fertility are not limiting. Nurse crops can provide additional income as a cash crop that can be beneficial as long as the potential for seed yield is not greatly reduced.

Soil Fertility. Grasses grown for seed have higher nitrogen requirements than do legumes. First-year seeding of grasses in summer fallow may not require additional nitrogen, but first-year grasses in conventional situations and second-year crops usually require additional nitrogen to produce adequate seed yields. It is important that nitrogen not be limiting during bud formation because this is when the number and size of seed heads is determined. Grasses that produce flower buds in the summer will respond to a single nitrogen application, whereas grasses producing flower buds in the fall (i.e., cool-season grasses) generally benefit from split nitrogen applications.

Although properly inoculated legumes require little additional nitrogen, additional phosphorus, potassium, and sulfur are frequently needed. Soil tests to determine residual nutrient levels should be used.

Post-establishment practices Water Management. The goal of water management is to reduce production of nonreproductive (vegetative) growth by using properly timed irrigations in the appropriate amounts. Many of the native and introduced warmseason grass seed crops are produced in the Great Plains where moisture is supplied by precipitation, and water management by irrigation is not effective. In the more arid seed-producing areas of the western United States, where much of the seed for forage crops is now produced, water is often supplied by irrigation except in those areas with sufficient spring and summer rain. The amount and timing of irrigations will depend on the crop species or variety, the depth and ability of soil to hold water, and temperature and wind speed as they affect the evapotranspiration rate.

Pollination Management. A few forage species are apomictic and can reproduce and set seed without fertilization; however, most forages require fertilization. Fer-

tilization is accomplished by pollination—the transfer of pollen from the stamen (the male reproductive structure of the flower) to the stigma (the female reproductive structure) of the same or a different plant, and subsequent fertilization of the ovule. Many annual grasses and some legumes are self-compatible so that the ovule may be fertilized by pollen originating from the plant on which the stigma resides. However, for optimal seed production, most perennial grasses and legumes require cross-pollination, or the transfer of pollen from the stamen of a flower from one plant to the stigma of a flower from another plant. Plants that require cross pollination can be pollinated by the action of wind, as is common in most grasses, or by the activity of insects.

Growers are not able to influence seed set accomplished through apomixis, self-pollination, or wind pollination. For cross-pollinated legume species, managing insect pollinators is important for ensuring maximum seed yields. These species are pollinated most frequently by populations of honey bees (Apis mellifera) or alfalfa leaf cutting bees (Megachile rotundata) (see description in “Beneficial Organisms: Pollinators”). Honey bees are used most commonly in legume seed crops (e.g., alfalfa and white clover) grown in California; they are also used in clover, vetch, and birdsfoot trefoil production in other seed production areas. Four to nine hives per acre are usually recommended. Honey bees work best in large field where competition from flowers of other crop plants and weed species can be minimized.

Leaf cutting bees are most commonly used to pollinate legume crops in the northwestern states of the United States and in Canada. These bees are provided nesting sites in shelters that can be moved within and between fields as necessary to provide maximum pollination or to protect bees from pesticide applications. Nesting sites consist of grooved, laminated boards or drilled wood or Styrofoam blocks. The number of bees required to effectively pollinate a forage seed crop varies with the insect and crop species.

Each female leaf cutting bee can set about ¼ lb (0.10 kg) of alfalfa seed). Based on this figure, 4,000 to 10,000 female bees are require to effectively pollinate an acre of alfalfa.

Weed and Disease Management. Weeds are more competitive in seed production because these stands have low plant populations compared with stands grown for forage production. Certification requirements also limit the amount of foreign seed allowed in the harvested crop.

In instances such as the parasitic plant dodder (Cuscuta spp.), weed seeds are not allowed in seed lots to be sold.

Use of effective rotational strategies can limit infestations by weed species that are difficult to control by other means such as herbicides. Once a vigorous stand has been 23

Forage and Rangeland Production established, weeds can be suppressed using a combination of cultural and chemical management tools. Preemmergence herbicides can be used to ensure a good initial crop stand. Post-emergence herbicides are important in the selective removal of weeds in established stands. Cultivation to remove weeds can be a very effective weed management tool for crops planted in rows. Mowing, grazing, or harvesting of early spring or winter growth of weeds can be an effective method of removing early maturing weed species in established perennial seed crops.

Harvest. Forage seed crops are harvested using combines similar to those used for harvesting grain crops, but which have been specially designed or adjusted to maximize seed yield. Timing and method of harvest are important considerations in reducing the amount of seed lost. Many forage species have seeds that tend to shatter when mature.

Because there can be considerable variation in seed maturity in a given field, timing harvest to avoid harvest losses caused by shattering is essential. Direct combining can be effective, particularly for small fields that tend to mature evenly. Swathing and then combining the windrowed material may be more effective for large fields or fields that mature unevenly because the crop can be harvested early before shattering has started, and moisture levels in the windrows can help to reduce shattering.

Rangeland Production By definition rangelands, and therefore the forage species produced in rangelands, receive minimal management inputs by comparison with those produced in pasture, cropland, and seed production systems. Rangeland vegetation is manipulated with two objectives in mind. The first is to maintain vegetation according to a desired set of plant characteristics (e.g., species composition, plant density, and foliar growth). The second is to alter the existing vegetation to achieve the desired plant composition and characteristics that are to be maintained. In recent years, manipulation of rangeland vegetation using fertilizers, herbicides, and mechanical control has been deemphasized in favor of adjusting grazing schedules. However, because manipulation of vegetation may be the only option for increasing forage for livestock and improving habitat on some ranges, these methods are discussed.

Establishment Practices Species and Cultivar Selection. Once it has been determined that seeding is necessary, and that the terrain is amenable to seeding, plant varieties are selected that are suitable for the intended use and adapted to the local cli24

mate, precipitation, soil, and topographic conditions. This is particularly important in rangeland situations where inputs after establishment may be minimal.

Seeding. Rangelands selected for overseeding may have overly competitive, undesirable species that must be removed to reduce competition with new seedlings. Several methods can be used. Mechanical removal using hand grubbing, disking, harrowing, root plowing with chain cables or even bulldozing can be used depending on the nature and extent of the vegetation to be removed and the terrain being seeded. Herbicide applications can suppress unwanted vegetation, and chemicals can be applied using ground or air equipment. Prescribed burning also can be used to remove unwanted vegetation. A firm seedbed that holds moisture near the surface, provides control of seed depth, and a good substrate for seeding establishment is desirable.

In rangeland seedings, plant mixtures are often recommended to increase the chance of stand establishment in heterogeneous rangeland environments. Where possible, drill seeding is superior to broadcast seedings because it provides better control of seed depth, distribution, and planting rate. Special seeders, called rangeland drills, are available for seeding rangelands. In situations where drill seeding is impractical or not possible, broadcast seeding can be done.

Broadcast seedings require higher seeding rates to ensure acceptable stand establishment. Even with higher seeding rates, seed distribution is often poor and seed predation higher, in broadcast seedings compared with drill seeding.

Seeding depth is a function of the forage species being planted, but ranges from 0.25â&#x20AC;&#x201C;1.5 in. (0.6â&#x20AC;&#x201C;4 cm) depending on soil type and condition and the species being planted. Seeding rate should be between 125 and 250 PLS for drill seedings and 500 PLS for broadcast seedings.

Seeding in nonirrigated land should precede the season with the most reliable rainfall. Rangeland seedings are frequently accomplished without fertilization. Where water is not limiting, supplemental fertilization applied in bands near the seed may be helpful.

Post-Establishment Practices Post-establishment weed management in rangeland systems is achieved primarily through grazing management. However, where grazing is ineffective, chemical control, mechanical control, and prescribed burning can be used to increase stands of desired vegetation. Proper grazing of established stands of desired forages can help to ensure stand vigor and persistence, reducing or eliminating infestations of unwanted plants.

Selected References: 5, 6, 50, 69, 77 J. D. Barbour