Legume species are important for economical production of pasture. Alfalfa, clovers, and birdsfoot trefoil all provide high-quality forage for grazing and do so without nitrogen fertilizer. These plants tend to be deep-rooted and more tolerant than grasses of summer moisture shortages. From these three standpoints, legumes are a very important component of productive pasture programs.
Legumes in pasture programs call for more careful management than do pure grass stands. Most legumes do not persist under continuous grazing and must be grazed rotationally. Pure stands of legumes, except birdsfoot trefoil, tend to cause bloat in cattle and sheep. Fertility (phosphorus and potassium) requirements are slightly higher for legumes than for grasses. Mixtures of legumes and grasses make excellent pastures. Because of competition between grass and legume, however, managing grass-legume pastures is more complicated than managing pure stands of either one alone. Pasture management practices usually should be designed to favor the legume in the mixture.
Alfalfa is a highly productive legume suited for harvesting or grazing. Animal gains are excellent, but care must be exercised to prevent bloat. Bloat control compounds (e.g., Poloxalene) must be used where pure alfalfa is grazed. Mixing a palatable grass, such as orchardgrass or perennial ryegrass, with alfalfa reduces bloat problems.
Alfalfa can be grazed starting in the late prebud stage in spring. Alfalfa pastures or grass-alfalfa mixtures must be rotationally grazed. The maximum grazing period for one subdivision pasture should be 10 to 14 days. After a subdivision pasture is grazed down, it should be given about 35 days to recover while other subdivision pastures are being grazed; therefore, three to five pasture subdivisions must be available. Clipping the pastures after grazing is important, particularly in spring when companion grass growth is stemmy. Pure alfalfa pastures are subject to severe trampling damage during prolonged wet periods. Adding grass to the mixture helps reduce this problem. When harvested during periods of grazing surplus, alfalfa and alfalfa-grass pastures produce excellent-quality hay or silage. For more information, refer to Agronomy Facts 42: Grazing Alfalfa in Pennsylvania, available from your local Penn State Cooperative Extension office.
Red clover forage is high in protein and energy, and animals eat it readily. Gain rates on red clover are excellent, but bloat can be a problem in pure clover stands. Palatable grasses in the mixture (timothy, brome, orchardgrass, and perennial ryegrass) decrease the risk of bloat.
Red clover can be grazed at the vegetative stage in spring. Clover/grass mix pastures should be rotationally grazed. Subdivision pastures should be grazed down in 10 to 14 days and then given 28 to 35 days to recover before grazing again. As clover stands begin to thin out during the second or third year, pastures can be managed like pure grass stands. Red clover seedlings are vigorous and can be reseeded in “run-out” pastures to maintain the legume without destroying the sod (see “Pasture Establishment, Renovation, and Maintenance,” below). Quality hay or silage can be made from clover/grass pastures during periods of pasture surplus.
Forage is of excellent quality and does not cause bloat. Trefoil forage does not decrease rapidly in quality with maturity as do cool-season grasses, alfalfa, and red clover. Because of this, spring growth of trefoil may be “stockpiled” for grazing in late June and July when other pastures are growing slowly.
Trefoil may be grazed starting at the bud stage in spring. For long persistence, trefoil should be rotationally grazed (10 to 14 days or less, followed by 28 to 35 days for recovery). To maintain sufficient stubble for quick regrowth, trefoil pastures should not be grazed under 3 inches. In emergencies, trefoil may be continuously grazed (up to 6 to 8 weeks), as long as 3 to 4 inches of stubble are maintained and time for recovery growth is allowed prior to a killing frost (4 to 5 weeks). Allowing the plants to go to seed (i.e., “stockpiling” spring growth until July 1) every 2 to 3 years aids in keeping dense stands of trefoil in pastures.
White clover (common and ladino types) is widely grown in pastures. Its forage quality is excellent; beef cattle, sheep, and horses eat it readily. Bloat can be a problem in pure or predominantly white clover stands. Ordinarily, there is plenty of grass in the mixture to minimize this problem.
White clover may be grazed continuously or rotationally. White clover may be grazed closely (1 to 2 inches) without serious damage to stands, but closely grazed pastures must be given time to recover. If grazed rotationally with tall-growing grasses, the pastures should be grazed at intervals of 3 weeks or less to prevent the grass from shading out the clover.