Georgia Forages: Legume Species (B 1347)Download PDF
Legume species add significantly to forage systems in Georgia. They are an excellent source of high quality forage, and are generally very digestible and contain high levels of crude protein (CP). Many legumes also provide substantial forage yields. Perhaps most importantly, legumes and the rhizobium bacteria that colonize nodules on their roots provide an important source of biologically-fixed nitrogen (N). This publication presents information about the most important legume species grown for forage in Georgia.
Cool Season Annual Legumes
Cool season (winter) annual legumes are generally planted in the fall and provide forage in late fall and spring. These plants flower and produce seed in late spring and die soon after seeds mature. Cool season annual legumes differ substantially in their preferred soil characteristics, growth distribution, cold tolerance, bloat potential and reseeding potential (Table 1). These species can be used for grazing (typically the best use) or for making hay, silage or grass-legume mixtures. Most cool season annual legumes are susceptible to several disease problems, nematodes and insects. When available, species and varieties with good pest resistance should be chosen to minimize management problems.
|Table 1. Minimum soil characteristics and management traits of selected cool season annual legumes.†|
|Min. pH‡||Texture||Drainage||Maturity||Cold Tolerance||Bloat Potential||Reseeding Potential|
|Arrowleaf clover||6.0||sand, loam||good||late||good||low||high|
|Ball clover||6.0||sand, loam, clay loam||fair||medium||good||high||high|
|Berseem clover||6.5||loam, clay||poor||medium||poor||low||low|
|Crimson clover||5.5||sand, loam||good||early||good||medium||low|
|Medics, annual||7.0||sand, loam, clay||fair||early||poor||high||high|
|Persian clover||6.0||loam, clay||poor||medium||fair||high||high|
|Red clover§||5.5||loam, clay||good||late||good||low||low|
|Rose clover||6.0||sand, loam, clay||good||medium||good||low||high|
|Subterranean clover||6.0||loam clay||fair||medium||fair||medium||low|
|Vetch, hairy||5.5||sand, loam, clay||good||medium||good||low||low|
|Winter pea||6.0||loam, clay loam||good||medium||poor||low||low|
|† Adapted from Evers, 2005.
‡ Minimum soil pH value (water pH equivalent) for acceptable yields.
§ Red clover is a perennial clover species; however, it is often used as a late-maturing cool season annual legume in the Coastal Plain Region. When used as a perennial, it has a medium to high potential for reseeding.
Arrowleaf clover is a highly productive winter annual grown from East Texas to Georgia. It is most productive when grown on well-drained loam or sandy loam soils but can do well on well-drained clay soils. It will not tolerate acid soils. Arrowleaf generally produces less forage in late fall and winter than crimson clover but can usually produce up to six weeks or longer in spring. In most areas of Georgia, it will provide excellent quality grazing until late May. Digestibility remains high until maturity. Arrowleaf is a good clover to include in grazing mixtures since it has a very low bloat potential and its late spring production of excellent-quality forage extends the grazing season.
Arrowleaf is a prolific seed producer, particularly of hard seed. To allow reseeding, remove animals from the paddocks or reduce stocking rates in late April or early May when the clover starts to flower. WARNING: If arrowleaf has been grown in a pasture for several years, its ability to reseed dependably is seriously compromised by a Fusarium spp. disease complex.
Sod-seeding arrowleaf into warm season perennial pastures is an excellent way to achieve spring grazing and to introduce biologically-fixed N into the system. Unchecked vigorous spring growth can reduce early spring growth of the perennial grass. To avoid a full canopy developing over the perennial grass in overseeded pastures, closely graze arrowleaf clover during the spring.
Arrowleaf will continue to produce new leaves and remain productive until late spring or early summer if grazing is managed to keep it between two and six inches tall. This management also will help improve light and air movement into the canopy, thus reducing disease problems. Arrowleaf will often exhibit symptoms of stress (e.g., purpling of the leaves) in response to fertility problems, cold stress or disease.
Several varieties of arrowleaf clover are available in the Southeast. Although many varieties are affected by a virus complex that can drastically reduce yields, some cultivars are now available that have demonstrated improved resistance to these viruses.
Ball clover has long, highly-branched stems that support white to yellowish-white flowered seed heads that look similar to white clover seed heads. Ball clover produces most of its growth about one month later in spring than crimson clover, and generally produces less total forage. However, it is an excellent reseeder, even under close grazing, and produces seed heads close to the ground. It is more tolerant of wet soils than crimson, but does not do well if soil pH drops below 6.0.
Berseem clover, a non-bloating winter annual, is adapted to southern Georgia. Stands in north Georgia are frequently winterkilled. Berseem has a longer grazing season, lower bloat potential and produces higher yields than crimson clover. Berseem is not tolerant of acid soils, but typically does better than many other winter annual legumes in poorly-drained sites. Berseem also has a higher boron requirement than other annual clovers and often does better on soils with more organic matter. Berseem is not a good reseeder.
Crimson clover often serves as a benchmark for other cool season annual legumes. Crimson furnishes some grazing in late fall and winter and abundant grazing in early spring. Crimson matures (flowers) earlier in spring than other annual clovers, has a shorter grazing season and produces high yields even in cool winters. Several varieties are now available that mature very early, allowing it to grow, be used, add biologically-fixed N to the soil and die with minimal competition with warm season perennial grasses. It grows best on well-drained soils and is frequently used in mixtures with ryegrass and small grains for winter grazing. It is also commonly used to overseed bermudagrass and bahiagrass pastures. Unfortunately, crimson produces relatively little hard seed and its seed heads are often damaged by clover head weevils. As a result, crimson clover usually does not reseed well in a grazing system.
Red clover is a short-lived, cool season perennial found in north Georgia and is commonly used as an annual in south Georgia. Red clover is often confused with crimson clover. While crimson clover produces dark red and elongated seed heads, red clover seed heads are typically round and a lighter red or lavender in color. Although it produces good yields (often more than two tons per acre), red clover matures much later than crimson clover. This later maturity fits better with annual ryegrass. Red clover does not recover from defoliation as quickly as arrowleaf and crimson and therefore may be easily damaged by overgrazing or selective grazing. Red clover fits well in management-intensive grazing systems where animals are prevented from grazing it too heavily.
Rose clover is commonly grown in California, and had not been widely grown in the Southeast until recently. It has hairy leaves and stems. It is winter dormant and produces forage and flowers later than crimson (although it matures earlier than arrowleaf). It is more drought-tolerant, more tolerant of acid soil conditions and is a better reseeder than crimson. It generally stands up well under heavy grazing, but animals should be removed in mid-April to allow the stand to produce seed.
Subterranean clover (sub clover) is native to the Mediterranean and the Near East and is well-adapted to areas with relatively warm, moist winters and dry summers. Sub clover is low growing (less than 1½ feet tall), but will create a very dense forage mat.
Its inconspicuous flowers will form burs after fertilization. The stiff-forked bristles of the seed bur allow it to peg or bury itself into the soil (much like peanuts), hence the name “subterranean” clover. It also produces hard seed with a high temperature requirement for emerging from dormancy. Although it is capable of good reseeding, in most management systems it is not feasible to allow the stand to progress to this advanced maturity stage.
Sub clover is best adapted to overseeding on perennial grass pastures. It provides forage in late winter and early spring. In a stocker program, sub clover overseeded on permanent summer pastures can serve as a reserve feed source. The productive season is similar to crimson clover.
Various species of vetch (hairy vetch, bigflower vetch, common vetch) are sometimes used in Georgia forage systems, with hairy vetch the most commonly grown. Their viney stems support compound leaves with narrow leaflets. Species are most easily distinguished by flower color (hairy: purple; bigflower: yellow-white; common: white).
Vetches are usually seeded in combination with a small grain and/or ryegrass on a prepared seedbed for winter grazing or silage. Close grazing will result in the loss of the bud (growing point).
Hairy and common vetch mature later in spring than crimson clover, but are cold-hardy, more tolerant of low soil pH than most clovers, and have a low bloat potential. Some common vetch varieties have been developed that are resistant to root-knot nematodes.
Winter pea (Austrian winter pea) produces a viney stem that will extend from two to four feet in length and produce white, yellow or purple flowers. Winter pea stems are often damaged by treading and are not well-suited for pastures. However, winter peas are frequently seeded with rye, wheat or oats for silage production. Winter peas should not be planted north of the lower Piedmont region because they are not cold hardy. Diseases can also substantially reduce yields.
Information about specific varieties of recommended cool season annual legume species may be found on the "Forage Species and Varieties Recommended for Use in Georgia" webpage.
Other Minor Cool Season Annual Legumes
Hop clover is a small, fine-stemmed winter annual that grows best on upland soils. It reseeds readily and furnishes some grazing in late winter and early spring. Seed are not commercially available, but it volunteers in many pastures. Yields are usually quite low and it contributes relatively little biologically-fixed N to the soil.
Several annual medics, including black medic, are commonly found in forage systems in Georgia. Like hop clover, they are rarely planted intentionally. Medics are excellent reseeders, thus they usually volunteers and fill thin areas of the pasture. Most medics yield less than one-third that of other winter annual legumes. Southern or spotted burclover (a type of medic) grows in late winter and spring, but animals generally do not graze burclover once it begins to mature. Burclover produces seed in abundance and reseeds readily, but has not been used extensively in Georgia because of poor yields.
Despite being a relatively low-yielding cool season annual legume with a short growing season, persian clover performs well under close grazing. It tolerates poor drainage and soil acidity down to pH 5.5, but it has a high bloat potential. Its pink seed head produces a fair amount of hard seed and it has the potential for good reseeding.
Lupine (or Lupin)
Lupines are best adapted to sandy loam and loamy sand soils. Since they generally are not cold hardy, they should not be planted north of the lower Piedmont region. Lupines were used relatively extensively prior to World War II as a supply of nitrogen for cotton in the Coastal Plain region. Lupine grows slowly in fall and winter, but vigorously in spring. Plants will flower from late March to early April. The relatively short productive season limits lupine’s use in forage programs. Lupines also commonly contain bitter alkaloids that make them less palatable to livestock than most legumes, but low-alkaloid “sweet” varieties are available that are suitable for forage use.
Establishment of Cool Season Annual Legumes
Cool season annual legumes can either be established on a prepared seedbed or overseeded on warm season perennial grass pastures. Planting with a drill (using the small seed box) or by broadcasting the legume seed can result in satisfactory stands. However, the seeding rate needs to be adjusted to compensate for the differences in these planting methods (Table 2). Information on broadcasting legume seed is detailed in "Seeding Methods for Small-Seeded Legumes."
|Table 2. Seeding rates for achieving a solid stand of selected cool season annual legumes.|
|(lbs. of pure live seed/acre)|
|† When only one legume is seeded — not in a mixture with grasses or other legumes (e.g., sod-seeding into bermudagrass).|
When planting into dormant warm season grass sod, one or more legumes may be used to achieve a solid legume stand. When planted in a prepared seedbed, these legumes are often mixed with a small grain crop or ryegrass. Seeding rates for the legumes used in such mixtures need to be adjusted to minimize seed costs and prevent excessive competition (Table 3).
Planting too deep is not usually a problem when legumes are broadcast on dormant warm season perennial grass sod. However, when legumes (especially small-seeded species) are being drilled or broadcast onto a prepared seedbed, special care should be taken to ensure that the seeds are not planted more than ¼- to ½-inch deep (see "Seeding Methods for Small-Seeded Legumes"). Large-seeded legumes such as lupine or common vetch can be planted up to one inch deep.
|Table 3. Seeding rates for selected cool season annual legumes used alone or in combination with other legumes in a mixture.†|
|(lbs. of pure live seed/acre)|
|†Use lower seeding rates when planting into a prepared seedbed or no-tilled into existing sod (overseeding). Use higher seeding rates when seed is broadcast.
‡Winter annual clovers are typically grown with one or more winter annual grass.
§Often, two or more clover species will be grown with the grass. The seeding rate of an individual clover species can be reduced if multiple clovers are included in the mix.
Seeding Methods for Small-Seeded Legumes
Ideally, small-seeded legumes should be planted using a cultipacker-seeder (prepared seedbeds only) or the small-seed box on a no-till or conventional drill. This provides the most accurate seeding rate control. However, the use of a no-till or conventional drill often results in small-seeded legumes being planted too deep (i.e., deeper than ½-inch). Some drills cannot be adequately adjusted to maintain a consistently shallow planting depth. Planting depth is harder to control when planting into wet soil, a soft seedbed or rough ground.
If these equipment or condition limitations exist, successful seed placement can occur if the seed are broadcast directly behind the drill’s shoes and in front of the press wheels. To do this, disconnect the tubes from the small seed box where it enters the drill’s shoes and secure the tubes behind the shoes or in front of the press wheels with wire or cable ties. This should allow the seed to be metered out on the soil surface, and the press wheels (with proper down-pressure) should firm the soil around the seed. This practice will ensure that the seeds are not planted too deep.
Accurately broadcasting small-seeded legumes (i.e., legumes with seeding rates less than eight to 10 lbs./acre) is difficult with large spinner-spreaders. If the available equipment cannot be adjusted to apply the low rate that is required, the inoculated seed can be mixed with coarse sand or some other inert material that is similar in size and weight. Smaller seeds should not be mixed with larger seeds in the hopper or seed boxes, since the small seeds will settle to the bottom. Also, legume seeds should not be mixed with fertilizer, since the fertilizer may kill the inoculant.
Broadcasted seed may not have sufficient seed-soil contact. Conventional-till seedbeds should be firmed with a cultipacker before seed are broadcast. Footprints left by an average person on a properly prepared seedbed should not be more than ¼-inch deep. Broadcast seeding on a prepared seedbed should be followed with adequate firming of the seedbed with a cultipacker.
When planting into an existing sod, broadcasted seed should be “scratched-in” to the soil using a chain drag or spike-toothed harrow. Some producers have also successfully used a pasture aerator. However, the aggressive use of a drag, harrow or aerator can damage the sod and/or expose areas to soil erosion or weed encroachment.
Cool Season Perennial Legumes
Cool season perennial legumes are most productive in the spring and fall, when temperatures and rainfall usually provide favorable growing conditions. These species slow down or even go dormant during the summer (especially if not irrigated) and have the potential to survive for more than one year.
Alfalfa is often referred to as the “Queen of Forages” because it produces high yields that are highly digestible and high in protein. Alfalfa can be effectively utilized in managed grazing, hay or silage systems. It is often used in rations when nutritional needs are very high.
Alfalfa requires a combination of proper soil characteristics (deep, well-drained, fertile, low acidity, etc.) with outstanding management (appropriate variety selection, timely harvests, pest control, etc.) to maintain long-lived, productive stands. It develops a deep root system if root growth is not restricted by hardpans, high water tables or acid subsoil.
Alfalfa can be grown in suitable soils throughout the state. In general, well-drained bottomlands in the Limestone Valley/Mountains and Piedmont regions will provide the best results. Within the Coastal Plain region, sandy loam soils provide good sites, especially if irrigation is available. Most sites in the Atlantic Coast Flatwoods and Tidewater areas will not be sufficiently well-drained to successfully produce alfalfa.
Alfalfa requires a relatively neutral soil pH (6.5 to 6.8) and non-limiting levels of essential nutrients. Alfalfa is especially sensitive to potassium (K), phosphorus (P), boron (B) and molybdenum (Mo) deficiencies. Close adherence to soil test recommendations during and after establishment is critical.
Alfalfa stands eventually thin to a point where the land must be rotated out, often due to insufficient soil fertility. Disease pressure, insect damage, poor weed control, overgrazing and improper cutting management also contribute to poor persistence. Stands in the Coastal Plain region generally have a shorter life (two to five years) than stands on the heavier soils in north Georgia. It is not uncommon for stands to persist for four to seven years (or longer) in the Piedmont and Limestone Valley/Mountains regions.
For monoculture stands, it is best to seed alfalfa on a well-prepared, firm seedbed. On prepared land, plowing and disking operations should be done as needed to incorporate pre-plant applications of lime and fertilizer and to ensure a good, firm seedbed. A preemergence application of a labeled herbicide such as EPTC (Eptam) or benefin (Balan) is desirable (for currently labeled herbicides, see the Georgia Pest Management Handbook. Alfalfa may be seeded with a cultipacker-seeder (best) or a grain drill with a small seed attachment. Cultipacking or rolling before and after seeding will give a firm seedbed and improve stands.
When seeding alfalfa with a grass such as tall fescue or orchardgrass, drill the grass in rows and immediately overseed the alfalfa with a cultipacker-seeder. For seeding into existing cool season grass sods (e.g., tall fescue, orchardgrass), suppress the grass by closely mowing or grazing, follow with a contact herbicide, and then plant with a no-till drill.
When planting alfalfa into a bermudagrass sod, ensure that the grass is dormant and closely mowed or grazed. If the stand is to be primarily an alfalfa stand, use a row spacing of 15 inches or less. If the stand is to be managed as a mixture of bermudagrass and alfalfa, use a row spacing of at least 21 inches.
Alfalfa should be seeded at a rate of 18 to 25 lbs. per acre (Table 4). Rates at the high end of this range should be used when planting with a no-till drill. Regardless of the system used to plant the alfalfa, the seed should not be placed too deep (⅛- to ¼-inch in loamy or clay loam soils; ¼- to ½-inch in sandy loam or sandy soils). Soil should be firm around the seed to provide proper seed-soil contact. An insecticide application after initial germination may be needed to control insects such as field crickets.
|Table 4. Seeding rate of selected cool season perennial legume species when broadcast, drilled, or planted with a cultipacker-seeder (CPS).|
(lbs of pure live
seed per acre)
|Drilled or CPS||18-25|
|Drilled or CPS||6-8|
|Drilled or CPS||2-3|
In the Limestone Valley/Mountains region and the upper half of the Piedmont, a fall seeding between mid-September and late October is recommended. In the lower two-thirds of the state (Lower Piedmont and Coastal Plain), a mid-October to late November seeding is recommended. Plantings made from early March to mid-April are much less desirable, but may be successful in north Georgia if there is a very aggressive defense against weeds and if irrigation is available. When planting into cool or warm season perennial grass sods, do not plant in the spring.
Additional information about the management and use of alfalfa can be found in “Alfalfa Management in Georgia.” Specific information about alfalfa varieties that are currently recommended may be found on the “Forage Species and Varieties Recommended for Use in Georgia” web page (http://www.caes.uga.edu/commodities/fieldcrops/forages/species.html).
White clover is one of the most widely-grown forage legume crops in the world. It is adapted to a wide range of soils and climates and is grown for forage from Florida to the northeastern United States. White clover is a relatively low-growing legume that spreads by stolons and can tolerate close grazing. It furnishes grazing in fall, late winter and spring. Yields of white clover are usually not sufficient for it to be grown alone or in a hay crop, but it contributes a substantial amount of high-quality forage when produced with cool season perennial grasses such as tall fescue. When grown in pastures, white clover is also compatible with some bermudagrass varieties.
White clover grows best on moist, fertile soils (especially along streams) and can die during hot, dry summers. However, some new varieties of white clover are more persistent and will either survive these conditions or return from seed. In the upper Piedmont and Limestone Valley/Mountains region, white clover does well on upland soils.
There are three basic types of white clover: large (e.g., Ladino clover, “Patriot,” “Regal”), intermediate (e.g., “Durana,” “Osceola”) and low-growing (e.g., Dutch clover). Large or ladino types are higher-yielding than other types, but they do not reseed as well and are generally shorter-lived.
The intermediate types are well-adapted to most sites throughout Georgia. They are prolific reseeders and may act as annual plants in south Georgia. Some improved intermediate white clovers are exceptionally tolerant of grazing and persist very well, even in some drought-prone and infertile sites.
Low-growing types are commonly seen on roadsides and in yards. Although they also are prolific reseeders, they are not planted for forage because of low yields and a poor ability to compete with grasses.
Red clover, a short-lived perennial legume, is adapted to a fairly wide range of soils. It is deep-rooted and, like alfalfa, does best on well-drained sites. It tolerates lower fertility and soil acidity than alfalfa, but persists better under good fertility. Red clover stands generally start to thin the second year. Some stands in Georgia have persisted for several years (most likely as a result of reseeding). Red clover is best adapted to heavy, fertile soils in north Georgia and can be seeded into tall fescue or orchardgrass stands with white clover. Red clover does not tolerate close grazing and will not produce or survive well in continuously-stocked pastures. Diseases also may limit stand life during cool, moist springs.
In some areas of south Georgia, red clover is used as an annual to overseed pastures or mix with a small grain or ryegrass. Some varieties are available that are resistant to root-knot nematodes and well-adapted to sandy loam and loamy soils in the Coastal Plain. These varieties are usually less winter dormant and produce more spring and autumn forage than other varieties, making them well suited to south Georgia. However, they may be less winter hardy than other varieties and not as well suited for north Georgia. Regardless, red clover should not be planted on droughty soils such as deep sands.
Establishing White and/or Red Clover
White clover and red clover are both well-suited for use as a companion to tall fescue or orchardgrass. These clovers can be planted with cool season perennial grasses in new plantings or can be established into existing grass stands (Table 4).
When planted with grass seed, both clovers can compete with grass. Therefore, clover seeding rates should be reduced by 25 percent when used in new plantings with a cool season perennial grass. In most cases, it is best to interseed the legumes after the grass stand is well-established.
Seeding rates are two to three lbs. of white clover per acre (drill or broadcast), six to eight lbs. of red clover per acre when drilled, or 12 to 15 lbs. per acre when broadcast. When seeding into tall fescue sods in the fall, closely graze or clip the grass before planting. On thick sods, some seedbed preparation (mild disking) may be needed to improve the vigor of the clovers during establishment. Contact herbicides may also be used to retard the fescue in the fall to help obtain a good stand of clover. Using a no-till drill, which can cut through the sod and place the seed into the soil, is the preferred seeding method (especially for red clover). Broadcasting and dragging seed onto a rough prepared seedbed can also be successful (see “Seeding Methods for Small-Seeded Legumes”).
White clover and red clover should be seeded in the fall (September to October). In the Limestone Valley/Mountains region, either clover can be planted in the winter (late January to early March). For a late-winter seeding (sometimes called “frost seeding”), the seed may be broadcast or drilled into a closely-grazed sod. Where the soil is exposed, the freezing and thawing of soil moisture during the winter will allow broadcast seed to work down into the soil. Many farmers in the Limestone Valley/Mountains region have had better results with late winter seedings due to better moisture conditions and fewer insect problems.
Information about red clover and white clover varieties that are currently recommended may be found on the “Forage Species and Varieties Recommended for Use in Georgia” web page (http://www.caes.uga.edu/commodities/fieldcrops/forages/species.html).
Other Cool Season Perennial Legumes
Several other cool-season perennial legume seeds (e.g., alsike clover, birdsfoot trefoil, etc.) are available, but are not commonly used. In general, these species are relatively expensive, difficult to establish, provide relatively low yields, and are disease-prone and/or not very persistent. This relegates them to minor production niches rather than extensive use.
Warm Season Perennial Legumes
Warm season perennial legumes are capable of producing substantial yields of high-quality forage during late spring and throughout the summer when temperatures and rainfall usually provide very stressful growing conditions (e.g., drought, disease pressure, etc.).
Perennial peanut is a rhizomatous peanut species that produces high-quality forage and persists well in the area in which it is adapted. This tropical legume is native to a South American region that mostly lies north of the 30° S latitude. As a result, perennial peanut generally does not survive well north of the 31.5° N latitude (roughly a line from Albany to Jesup). Within these locations, it is best suited to well-drained sandy or sandy loam soils. Varieties that are currently available do not have good cold tolerance and may winter-kill during severe winters.
Perennial peanuts are established by planting rhizomes between December and early March at 80 bushels per acre (up to 120 bushels per acre if sprigs are inexpensive or freely available). Perennial peanut may require two years or more to develop a solid stand after sprigging. The establishment phase will be minimized under irrigation. Once established, the stands do not generally tolerate close or continuous grazing. As a result, perennial peanut is primarily recommended for hay production. As a high-quality legume, perennial peanut is an excellent hay and baled silage crop.
Sericea lespedeza is a long-lived, deep-rooted, drought-resistant perennial that will grow on heavy, well-drained soils throughout the state. It grows erect, with stems two to four feet tall, and can be used for grazing, hay or soil conservation. Sericea is frequently used for cover on road banks to prevent erosion. Sericea can be grown on soils too acidic and infertile to support other forage legumes; however, it will not be very productive unless it is well fertilized.
Sericea can provide moderate-quality forage; however, as the plant matures, the stems become taller, highly lignified and very woody. Late maturity will result in very poor forage quality that most animals will increasingly avoid. Therefore, sericea should be managed to keep the plants growing vigorously. Grazing should begin when plants are eight to 15 inches tall and should not be grazed closer than four inches. Hay harvests should be taken when plants reach 15 to 24 inches. Sericea provides good quality forage in summer when dry weather has reduced the growth of other forage crops.
Sericea lespedeza also contains high concentrations of condensed tannins, which will reduce forage digestibility. However, research at Fort Valley State University has shown that these tannins can act as an anthelmintic (dewormer) to help control parasitic worms in small ruminants (e.g., goats, sheep). The use of sericea for this purpose holds significant promise as producers seek ways to reduce the buildup of anthelmintic-resistant populations of internal parasites. Low-tannin, more palatable varieties of sericea lespedeza are also available.
Sericea lespedeza can be seeded on a prepared seedbed in the spring as soon as the last frost has passed. A cultipacker-seeder should be used to seed 15 to 20 lbs. of inoculated, hulled, scarified seed per acre. Sericea stands are slow to establish, so it is essential to apply a pre-plant incorporated herbicide. Do not cover the seed with more than ¼-inch of soil. Generally, sericea should not be grazed or cut for hay in the establishment year unless excellent weather conditions have resulted in rapid growth.
Information about perennial peanut and sericea lespedeza varieties that are currently recommended may be found on the "Forage Species and Varieties Recommended for Use in Georgia" web page (http://www.caes.uga.edu/commodities/fieldcrops/forages/species.html).
Warm Season Annual Legumes
Warm season annual legumes are also productive during late spring and summer. They are not frost tolerant and do not survive winters; however, these species can produce high-quality forage during the summer when it is needed.
Annual lespedezas used for forage in the South consist of two species (striate lespedeza and Korean lespedeza) that were introduced from Korea and Japan. They are adapted to a wide range of soils and fertility levels and are used in pasture mixtures to provide good quality grazing from late spring until fall. Annual lespedezas can be cut for hay, but yields are relatively low. High levels of soil fertility will result in lespedezas being crowded out by warm season perennial grasses.
Striate lespedeza is commonly called “Kobe” or “Marion.” Striate is the most useful of the annual lespedezas in the South. It provides significant grazing and can be cut for hay. Striate has narrower leaflets than Korean varieties and produces seed in the axils of branches directly along the stem. Varieties of this species are prolific seed producers and will reseed in pastures. Improved varieties have superior reseeding potential, yields and disease resistance.
Korean lespedeza matures earlier than the striate varieties and provides earlier grazing in summer. However, the growth of Korean varieties declines earlier in the fall than striate varieties. Korean does not volunteer well in south Georgia and is less tolerant of acidic soils than the Striate varieties.
Annual lespedeza can be sown from mid-winter until early spring. Adequate stands in pastures, fallow land or overtop of small grain crops will normally be achieved by broadcasting seed without covering. When planting in late spring on prepared seedbeds, use a grain drill or cultipacker-seeder to cover seed with about ¼-inch of soil. For a pure stand, broadcast 25 to 30 lbs. or drill in 15 to 20 lbs. of inoculated, unhulled seed per acre.
Forage soybeans are typically harvested for hay or silage; however, they can be used for late summer temporary grazing. Since they do not regrow once defoliated, strip-grazing (or frontal grazing) is the most efficient use. Soybean forage is fairly digestible (up to 60 percent) and moderately high in CP (17 to 19 percent). Stem size can be reduced, thus increasing digestibility, if seeding rates of 90 to 120 lbs. of seed per acre are used. Planting late-maturing varieties (maturity groups 6, 7 or 8) from early May to early June will result in forage soybean production best suited for high yields. Shorter periods of growth, such as part of a double- or triple-crop system, can be accommodated with early-maturing varieties. However, productivity is expected to be substantially less.
Other Warm-Season Annual Legumes
Several other warm-season annual legumes are available but not commonly used. A partial list of those that could provide acceptable forage yields and quality include: alyceclover, annual peanut, cowpeas, hairy indigo, joint vetch, kudzu, lablab (sweet hyacinth bean) and velvetbean. In general, these species can be relatively expensive and difficult to establish, provide relatively low yields and/or are not very tolerant of grazing. This relegates them to minor production niches, such as wildlife food plots, rather than extensive use.
Quantity of Nitrogen Fixed
Each of the aforementioned legumes can fix appreciable but substantially different quantities of nitrogen (N) (Table 5). In addition to species differences, the amount of fixed N also depends on the rate of plant growth, total forage yield, growing season length and grazing or harvesting methods.
|Table 5. Estimated range in nitrogen fixing potential of several legume crop species.†|
|Legume Species||Amount of Nitrogen Fixed‡
(lbs. of N/acre)
|† Adapted from Johnson et al., 1997; Havlin et al., 1999; Ball et al., 2007.
‡ The lower end of this range in nitrogen fixation is expected when the legume species makes up approximately 25 percent of the stand. The upper end of this range should only be expected in pure stands under excellent growing conditions.
Since N-fixation requires so much energy from the plant, it is critical that the plant is able to maintain a rapid growth rate. Nitrogen fixation will be drastically reduced by factors that slow crop growth and seasonal yield totals (e.g., drought, water-logged soils, unfavorable temperatures, low light conditions/shading, low soil fertility, low soil pH, competition from weeds or other plants, insect damage, disease, etc.).
The legume growing season also impacts the amount of N that is fixed. Legumes with a long growing season, such as alfalfa, will typically fix more N than annual legumes that have a shorter growing season and produce less total forage.
Johnson, J.T., R.D. Lee, and R.L. Stewart. 1997. Pastures in Georgia. Extension Bulletin 573. University of Georgia. Athens.
Havlin, J.L., S.L. Tisdale, and W.L. Nelson. 1999. Soil Fertility and Fertilizers: An Introduction to Nutrient Management. 6th Ed. Prentice Hall, Inc.
Ball, D.M., C.S. Hoveland, and G.D. Lacefield. 2007. Southern Forages. 4th Ed. International Plant Nutrition Institute. Norcross, GA.
The authors wish to acknowledge and express their appreciation to Drs. Don Ball, Carl Hoveland, and Garry Lacefield, authors of Southern Forages, 4th Edition, and to Don Armstrong of the International Plant Nutrition Institute for their willingness to allow the reproduction and use of copyrighted (2007) photographs of forage legume species.