Edward Twidwell | 2/18/2009 10:47:25 PM
Alfalfa is commonly known as the “queen of the forage crops.” If managed properly, this deep-rooted perennial legume species produces forage which is extremely high in digestibility and protein and also contains a good supply of minerals and vitamins. In addition, alfalfa is extremely palatable and, therefore, is readily consumed by livestock.
Alfalfa is, however, a demanding crop which requires a high level of management if it is to reach its production potential. A producer growing alfalfa should be prepared to control weeds and insects, to lime and fertilize properly and to harvest at the right stage of maturity. In Louisiana it is possible to harvest a stand three to five times per year, and hay production can range from two to five tons per acre.
The primary problem with growing alfalfa in Louisiana is a lack of persistence. Although stands frequently last five years or more in northern areas, they may last no more than two years in Louisiana. This is probably due to a combination of harmful insect and disease pests that are favored by Louisiana’s warm, humid climate. These include diseases that can destroy the root system and insects that can defoliate the alfalfa plants.
Alfalfa requires a deep, fertile, well-drained soil that has both good surface and internal drainage. One of the most frequent mistakes producers make in establishing alfalfa is planting it on poorly drained soils. A soil test should be taken because it is the most economical investment in an alfalfa fertility program. A soil test should be used as a guide to determine rates of lime, phosphorus and potassium to apply. Alfalfa grows best and maintains stands the longest on soils with a pH of 6.0 to 7.0, with 6.5 being about optimum.
Begin seedbed preparation for alfalfa plantings anywhere from 30 to 60 days prior to planting. This allows time for rains to firm the soil and build up a moisture supply. Lime and fertilizer can be applied during these tillage operations to correct any pH and/or nutrient deficiencies as indicated by a soil test. A firm seedbed, which will hold moisture close to the seed for rapid germination and prevent the new roots from drying out, is an important factor in successful establishment of new stands. The seedbed should have enough fine, granular soil to cover the seed. Alfalfa can be planted successfully with a cultipacker-seeder, with a seeding attachment on a cultipacker, by broadcasting followed by rolling or harrowing lightly or seeding with a drill. Seeding on a firm seedbed and cultipacking is generally the most successful method. Regardless of seeding method, the seed must not be planted deeper than ¼” in heavy soil or ½” in light soil.
Seeding Dates and Rates
A major factor to consider in selecting a date for planting alfalfa is to make sure it is planted early enough to become somewhat established before the first freeze in the fall. When alfalfa is in the young seedling stage, even a slight freeze may cause severe damage. The optimum seeding date for alfalfa in Louisiana is October 5-15. Alfalfa can be seeded as late as November 15 if conditions preclude plantings in October. Recommended seeding rates for alfalfa are 20 to 30 pounds of seed per acre.
Louisiana does not have an alfalfa variety testing program, so it is therefore difficult to recommend specific varieties. Several private companies have developed varieties specifically for the southern region of the United States. Individuals interested in planting alfalfa should contact their local extension agent or local seed supply company for more information about specific alfalfa varieties for their locale.
Harvest timing in alfalfa is important. Yields tend to increase as the crop grows and matures to a late-flowering stage. Forage quality, however, declines as the crop matures. The time of harvesting also influences rate of regrowth, since regrowth occurs from crown buds that tend to develop in cycles rather than continuously. Frequent cutting (every four weeks or less) may weaken a stand and shorten persistence. In more northern states, alfalfa harvesting is generally timed by the stage of flower development. In Louisiana, stage of flower development is not always a good indication of readiness of crown buds to begin development, so the following cutting schedule is suggested.
On first-year stands of alfalfa, initial cutting should be made in the spring when the crop reaches the half-bloom stage (when half of the plants are flowering). On established stands of alfalfa, the first cutting should be made in the spring when the crop reaches the late-bud to 1/10 bloom stage. Second and subsequent harvests each year should be made when elongation of the crown buds begins but before they become long enough to be clipped during harvest. This should result in a harvest interval of about five to six weeks during rapid plant growth. The last cutting before frost each fall should be made early enough to allow 12 to 18 inches of regrowth before frost. Harvesting at least four weeks before frost generally allows regrowth and buildup of plant reserves for good winter survival. After a hard freeze in the fall, the top growth may be removed without serious damage to stand survival.
Alfalfa should be cut at a time and at a stubble height that leaves new growth from crown and axillary buds intact. A cutting height of 2 to 4 inches is usually satisfactory. The forage can be stored as hay, haylage, balage or silage.
Fertilizing Established Stands
Vigorous alfalfa stands must have adequate soil fertility. Alfalfa does not require nitrogen fertilizer, but lime, phosphorus and potassium must be added as soil tests indicate. Alfalfa, like any other high-yielding crop, utilizes soil nutrients heavily. Each ton of alfalfa contains about 100 pounds of lime, 15 pounds of phosphorus, 60 pounds of potassium and 2 pounds of boron. Fertilizer can be applied at any time during the year. However, a good time to lime and fertilize for stand maintenance and production is after the last harvest in one growing season and before growth begins in the next growing season. Soil tests should be taken every year.
Weeds can be a problem during initial stand establishment and during the entire lifetime of an alfalfa stand. The most important weed control factor is a dense, vigorous stand of alfalfa, which will crowd out weeds. Close mowing (2- to 3-inch stubble height) will not injure alfalfa but will kill or reduce the vigor of many weeds. Many weed species can become a problem in alfalfa, including chickweed, henbit, pigweed, lambsquarter, curly dock, mustards and other broadleaf and grassy weeds. Refer to Louisiana’s Suggested Chemical Weed Control Guide (publication #1565) for specific herbicide recommendations.
Insect and Disease Control
The major insect pests that negatively impact alfalfa in Louisiana are alfalfa weevils, three-cornered alfalfa hoppers, aphids, armyworms and potato leafhoppers. All of these insects can negatively impact alfalfa yield, quality and stand persistence. Refer to the Louisiana Insect Pest Management Guide (publication #1838) for specific control recommendations.
Bacterial wilt, leaf spot, anthracnose and phytophthora are diseases that generally cause the most serious damage to alfalfa stands. The severity of some of these diseases can be enhanced when alfalfa is grown in wet soils, so avoid planting alfalfa into poorly drained soils if at all possible. Refer to the Louisiana Plant Disease Management Guide (publication #1802) for specific control recommendations.