Alfalfa Management in Georgia (B 1350) University of Georgia Extension Alfalfa is a high-yielding, perennial legume that is well-suited to hay, silage, or pasture production. Alfalfa is known as the “Queen of Forages” because it produces an excellent quality, high-protein forage. These properties make alfalfa one of the most widely-grown crops in the world. 2016-01-07 18:38:58.253 2009-01-09 09:25:54.0 Alfalfa Management in Georgia | Publications | UGA Extension Skip to content

Alfalfa Management in Georgia (B 1350)

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Alfalfa Farm Alfalfa growing on a farm in Walker County, GA

Dennis W. Hancock, Extension Forage Agronomist, Department of Crop and Soil Sciences
G. David Buntin, Extension Entomologist, Department of Entomology
Lane O. Ely, Extension Dairy Scientist, Department of Animal and Dairy Sciences
R. Curt Lacy, Extension Livestock Economist, Department of Agricultural and Applied Economics
Gary L. Heusner, Extension Equine Scientist, Department of Animal and Dairy Sciences
R. Lawton Stewart, Jr., Extension Beef Nutritionist, Department of Animal and Dairy Sciences

Introduction

Alfalfa is a high-yielding, perennial legume that is well-suited to hay, silage, or pasture production. Alfalfa is known as the “Queen of Forages” because it produces an excellent quality, high-protein forage. These properties make alfalfa one of the most widely-grown crops in the world.

Acreage in Georgia devoted to the production of alfalfa hay peaked in the late 1950s at around 24,000 acres. Most of this production was concentrated on the Piedmont and Limestone Valley/Mountain regions and provided high-quality forage for the dairy and beef cattle industry in north Georgia. The heavier soils in these areas tend to be more fertile and less acidic, which allows well-managed alfalfa to persist for at least four to seven years.

Although acreage declined in the 1960s because of more cost-effective forages, alfalfa production in Georgia recently has been steadily increasing. Breeding efforts at the University of Georgia and elsewhere have greatly improved stand-life in the Southeast. These new varieties are better adapted to specific soil and climatic regions in Georgia, especially the Coastal Plain region. In these areas, adapted varieties generally produce four to six tons of dry matter (DM) per acre under normal growing conditions. Well-managed stands of adapted varieties should persist for at least three to five years in south Georgia.

The most dramatic increase in alfalfa acreage has been in the Coastal Plain region, where many plantings made on irrigated soils have produced yields ranging from five to eight tons DM per acre. Dryland alfalfa production in the Coastal Plain is riskier, as many soils in these areas are prone to drought. Although, alfalfa is relatively drought tolerant, it will be much less productive under moisture stress.

Establishment

Site and Soil Selection

Alfalfa grows best on deep, well-drained, and fertile soils with a high moisture holding capacity. Alfalfa is a deep-rooting plant if root growth is not restricted by hardpans, high water tables (poor drainage), or acid subsoils.

Sandy loam or clay loam soils in the Piedmont and sandy loam soils in the Coastal Plain may be well suited for alfalfa production. Soils that have been cropped for several years using good management practices are generally more suitable than soils that have recently been cleared and brought into production. Well-managed cropland soils usually have a history of fertilizer and lime applications. As a result, these soils will often be more fertile and have higher pH values at both the soil surface and through the soil profile.

In the Coastal Plain, it is especially important for subsoil acidity to be evaluated before considering planting alfalfa. Subsoil acidity may take years (eight or more) to remediate and should be evaluated by collecting soil samples in one-foot increments down to four feet. The pH in each of these increments should be equal to or greater than 5.5. As pH levels decline below 5.5, aluminum (Al) increases in soil solution. At sufficient concentrations, Al becomes toxic to root growth. Avoiding sites that have subsoil pH values below 5.5 is therefore critical for optimum root development and alfalfa production.

Level land is not necessarily a requirement for alfalfa; however, slopes that are not conducive to tillage, machinery operations, and/or irrigation may not be suitable for alfalfa grown for hay or silage.

Variety Selection

Variety selection is one of the most important considerations in an alfalfa production program. Many alfalfa varieties are on the market, but most were developed for use in other areas of the country and may not perform well in the Southeast. Also, varieties suitable for use in north Georgia may not perform well in south Georgia, or vice versa.

Disease Resistance:

Since many disease and insect pests attack alfalfa, most varietal development has concentrated on improving overall pest resistance. Consequently, many varieties are now available that exhibit resistance to multiple pests. Such a diverse genetic base for resistance to many pests has resulted in a broad array of varieties that out-yield and are more persistent than many old cultivars. For Georgia, specific emphasis should be placed on selecting varieties that are highly resistant to as many disease and nematode problems as possible.

Dormancy:

Another consideration in selecting a variety is the cultivar’s growth period. Varieties differ widely in how early they initiate regrowth in late winter and when they go dormant in the fall. Alfalfa varieties are rated on a “fall dormancy” scale (Table 1) that rates the timing of when the variety ceases growth in the fall of the year. This is an important trait where winters are long and severe, because cultivars that go dormant earlier in the fall are better able to protect themselves for longer winters.

Less dormant varieties are more appropriate for alfalfa production in Georgia. The fall dormancy rating scale divides varieties into groups 1 through 9, with 1 being extremely dormant (no fall-winter growth) and 9 being non-dormant (active winter growth). For the Limestone Valley/Mountain and the Piedmont regions, varieties with a dormancy rating of 3 to 6 are recommended. Dormancy groups 5 to 9 are more suitable for the Coastal Plain region.

Table 1. Fall dormancy in alfalfa varieties.
Dormancy Group Rating Notes
Very Dormant 1 Very winter hardy, no fall or late winter growth
Dormant 2 and 3 Winter hardy, little fall or late winter growth
Moderate Dormant 4, 5 and 6 Moderately winter hardy; moderate fall and late winter growth
Nondormant 7 and 8 Not winter hardy; good fall and late winter growth
Very Nondormant 9 Very susceptible to any winter conditions; very good fall and late winter growth.

Grazing Tolerance:

Improving grazing tolerance — an important new development — was pioneered by Dr. Joe Bouton, a long-time plant breeder at the University of Georgia. Dr. Bouton’s work resulted in the release of several “grazing” varieties that are tolerant of rotational grazing and “dual-purpose” varieties that are useful for hay and grazing.

Information about Specific Varieties: Most seed companies that sell alfalfa seed are members of the Alfalfa Council. This group provides a list of the varieties that their member companies offer for sale, available online at www.alfalfa.org. The Alfalfa Council's list contains information on nearly 400 distinct varieties segmented by dormancy group. It also includes ratings of each variety’s resistance to seven diseases and seven insect pests, and information on traits such as winter survival, multi-foliate expression rate (leaves with more than three leaflets), and grazing tolerance.

The Alfalfa Council’s list of alfalfa varieties is not completely comprehensive and may not include some information that would be pertinent to variety selection for Georgia producers. Therefore, University of Georgia forage researchers and plant breeders review recent research data on current and new alfalfa varieties and maintain a list of recommended varieties. Usually, the recommended varieties have been evaluated in yield and persistence trials conducted by scientists at the University of Georgia Agricultural Experiment Stations. These varieties are also known to have levels of disease resistance that are appropriate for the locations for which they are recommended. The current list of recommended varieties can be found on the “Forage Species and Varieties Recommended for Use in Georgia” web page at www.caes.uga.edu/commodities/fieldcrops/forages/species.html.

Soil Fertility at Establishment

Lime application prior to soil preparation. Lime application prior to soil preparation.

Assessing soil fertility is the next step in gauging whether or not a site is suitable for alfalfa production. Alfalfa has a high fertility requirement and a soil test will determine the need for lime and fertilizer. Always apply the recommended quantities indicated on the soil test report. Proper fertilization and soil pH adjustment prior to establishment are critical to promoting early growth, disease resistance, and winter hardiness. Maintaining adequate fertility is equally important and is addressed in greater detail in the section titled “Fertilizing and Liming Established Stands”.

When soil analysis indicates a pH below 6.5, apply sufficient agricultural limestone to adjust the soil pH to 6.8 to 7.0. It takes time for lime to neutralize soil acidity, so it should be applied at least six months prior to seeding. If possible, the lime should be incorporated into the soil to allow the amendment to affect deeper portions of the soil. If more than two tons of limestone are needed, apply one-half of the amount and incorporate it by first disking and then turning the soil. Use a plow to uniformly mix the limestone in the plow depth. Apply the remainder and incorporate it into the soil surface by disking.

Phosphorous (P) and potassium (K) are two plant nutrients critical for establishing alfalfa stands. Adequate levels of P and K are crucial for root development and seedling vigor. Boron (B) and molybdenum (Mo) play significant roles in nodule formation and nitrogen-fixation and are essential for alfalfa establishment and production. Only small quantities of these micronutrients are needed. Immediately prior to planting, 1/4 ounce of molybdenum (2/3 ounce of sodium molybdate) should be applied to each bag (60 lbs.) of alfalfa seed in just enough water to slightly moisten the seed. (CAUTION: To avoid Toxicity, do NOT exceed the recommended amount of molybdenum.)

Alfalfa is a deep-rooting forage crop when unimpeded by soil properties. Fertilizer (particularly phosphorous) should be incorporated into the soil as deeply as possible using conventional equipment. Since alfalfa will survive for several years and fertilizer and lime applications made in subsequent years will be surface-applied, uniform incorporation before establishment provides long-term benefits.

Inoculation

Many companies have begun to market pre-inoculated alfalfa seed that have been coated with an inert material, usually lime, to protect the inoculant. This saves time and helps ensure adequate and appropriate inoculation. No further inoculation before planting should be necessary, unless the inoculated seed has been stored improperly or the inoculant has expired.

Improper Innoculation Improperly inoculating alfalfa seed will likely result in poor nodulation, Permanent stunting, or stand failure.

If there is a question about the viability of the inoculum on pre-inoculated seed, re-inoculate the seed with fresh “Type A Inoculant” (the Rhizobium meliloti bacteria that are specific to alfalfa) just before seeding. Inoculants are usually packaged in plastic bags to protect the bacteria from drying. Protect bags of inoculant from direct sunlight or hot temperatures. One eight-ounce bag of inoculant will generally be enough to inoculate one bag of seed. However, always read and follow the label instructions. Inoculate only the amount of seed that will be planted each day andkeep the inoculated seed in a shady location until it’splaced into the planter.

To inoculate, fill a large metal or plastic tub about half full with seed and apply enough water to moisten the seed (you will need to stir the seed). Sprinkle the recommended amount of inoculant on the moist seed and stir until the seed are uniformly coated. Moist seed tend to stick together, so let the seed dry for a few minutes before seeding.

The inoculant sticks to the seed better if a water-sugar solution or syrup-water solution is used to moisten the seed. Research indicates that a commercial sticker material significantly improves inoculation.

Establishment Methods and Considerations

Prepared Seedbed: For monoculture alfalfa stands, plant alfalfa on a well-prepared, firm, weed-free seedbed. Plowing and disking should be done as needed, incorporating pre-plant applications of lime and fertilizer, and a good, firm seedbed should be ensured. All tillage or heavy disking operations should be completed at least five weeks before the expected seeding date. Smooth the seedbed and disk lightly as needed to control weeds and incorporate pre-emergence herbicides prior to seeding. Use of a heavy roller or culti-packer before seeding will firm the soil and improve seedling establishment and stands. A rule of thumb for determining when the soil is appropriately firm is observing the depth of footprints in the soil. When a boot-heel leaves only a 1/4-inch indention in the soil (assuming the person is of average weight), the soil is firm enough for planting.

Sandy Coastal Plain soils may have compacted layers or hardpans, which can restrict root growth and affect water and nutrient uptake by the plant. Subsoiling or chisel plowing can be beneficial if the soil has a hardpan.

Cultipacker A cultipacker can help firm the soil prior to planting.
Boot Heel Sink Soil that is firm enough for planting will allow a boot-heel to sink no deeper than 1/4-inch.

No-Tillage Methods:

Although conventional tillage and planting into a prepared seedbed is ideal, planting alfalfa with a no-till (sod-seeding) drill can result in satisfactory stand establishment and yields. Some producers are planting alfalfa into existing stands of bermudagrass or other grass sods. This will require no-till establishment.

When planting alfalfa into a bermudagrass sod, ensure that the bermudagrass is dormant and closely mowed (and free of residue) 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 managed as a mixture of bermudagrass and alfalfa with an expectation that it will eventually revert back to solid bermudagrass, use a row-spacing of 21 inches or more.

For no-till seeding into existing cool-season grass sods (e.g., tall fescue, orchardgrass), suppress the grass by closely mowing or grazing before planting with a no-till drill. If the grass is in or will be entering a rapid growth phase, chemical (herbicide) suppression of the grass immediately before planting may be necessary.

Seeding Methods and Rates: Using a cultipacking-seeder or grain drill with a small seed box to plant alfalfa into a prepared seedbed will usually result in satisfactory stands. Alternatively, seed may be broadcast and then incorporated using a double-gang, culti-packer. Regardless of the system used to plant the alfalfa, the seed should not be placed too deep (1/8- to 1/4-inches deep in loamy or clay loam soils; 1/4- to 1/2-inches deep in sandy loam or sandy soils). When seeding with grain drills, accurate depth control may be difficult to obtain. If seeding depth control will be difficult, the grain drill can be used as a broadcast seeder by disconnecting the drop tubes from the small seed attachment box and fixing it in such a way that the seed are discharged about two feet above the soil surface.

Cultipack Seeder Cultipacking-seeder planting into a firm seedbed.
Cultipacking after Seeding Soil that is firm enough for planting will allow a boot-heel to sink no deeper than 1/4-inch.

Cultipacking after planting with a grain drill will improve seed-soil contact.

Soil should be firm around the seed to provide proper seed-soil contact. Cultipacking or using a heavy corrugated roller after seeding will aid seed-soil contact and improve stands. An insecticide application after initial germination may be needed to control insects such as field crickets. If the seedbed is weedy (especially with ryegrass), spray with a non-selective, translocated herbicide (e.g., glyphosate) a day or two before seeding, or immediately after seeding.

When alfalfa is planted with a cultipacking-seeder or grain drill, the seeding rate should be 18 to 25 lbs. of pure live seed per acre. Higher rates should be used when seeding conditions are marginal, such as when planting with a no-till drill. When planting coated seed, some adjustment in seeding rate may be made to account for the coating weight.

Seeding Dates:

In the Limestone Valley/Mountains region and the upper half of the Piedmont, a fall seeding in mid-September to 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 between early March and mid-April may be successful in both locations but will likely require irrigation and a very aggressive defense against weeds. When planting into cool- or warm-season perennial grass sods, do not plant in the spring.

Always plant alfalfa when soil temperature and moisture conditions will allow rapid seed germination and establishment. This is critical for later seedings. Alfalfa seedlings need six to eight weeks of good growing conditions before the first hard freeze (temperatures below 25° F) occurs. Alfalfa seeds germinate much slower in cold soils and may benefit from a low application of N when the rhizobia are relatively inactive in cold soil.

Weed Control during Establishment: Weed competition can cause poor stands. Treatment with a pre-emergence herbicide, such as EPTC (Eptam) or benefin (Balan), that controls winter annual grass and broadleaf weeds is recommended. Common bermudagrass must be eliminated from the field before planting alfalfa. This grass is often extremely difficult to control in alfalfa stands. Further information about weed control during establishment and during the life of the stand are presented in the “Weed Control” section of this publication. Additional up-to-date information about specific herbicide options during alfalfa establishment can be found in the “Alfalfa Weed Control” section of the Georgia Pest Management Handbook.

Crop Rotation Requirement:

Alfalfa is an excellent addition to a crop rotation, particularly for crops that require high nitrogen fertilization. However, rotating out of alfalfa eventually must be done. Alfalfa produces compounds from its leaves and flowers that are autotoxic (i.e., they prevent alfalfa seed from germinating and growing). Once fully established (six to eight months), these autotoxic compounds prevent the “thickening-up” of a stand by planting more seed. This prevents alfalfa from being successfully planted into an existing or recently destroyed (within eight to 12 months) alfalfa stand. Do not plant alfalfa into a field that contains or contained alfalfa within the last eight to 12 months. Always allow a full growing season of another crop(s) before replanting alfalfa.

Fertilizing and Liming Established Stands

Maintaining adequate fertility is essential for successful alfalfa production, since nutrient deficiencies lead to yield losses, poor disease resistance, pest problems, and short-lived stands. If any nutrient is deficient, problems in any one or all of these areas can be expected. Thus, it is critical that a good soil fertility program be the basis of any alfalfa production system. This section briefly presents information on several aspects of soil fertility management.

Soil pH

It is critical that a soil pH of 6.5 to 7.0 be maintained in areas were alfalfa is grown. When soil pH is kept at this level, the nutrients stored in the soil will be most available to the alfalfa, and the alfalfa’s ability to use applied fertilizer nutrients will be improved. Maintaining the appropriate soil pH also promotes nodulation and more efficient nitrogen fixation. Soil test each fall and apply limestone as needed.

Low soil pH Low soil pH in this area of an alfalfa field in South Georgia has resulted in a thin stand.

Maintaining proper soil pH also prevents toxic elements such as Al and manganese (Mn) from becoming soluble in the soil. When soil pH drops below 5.5, Al dissolves in the soil solution. Soluble Al is toxic to alfalfa roots and drastically inhibits root growth. Addiing of lime raises soil pH, and the Al returns to a solid form.

Neutralizing soil acidity deep into the soil profile is difficult. As a result, the soil surface may be neutral while the subsoil is very acidic. In this situation, the addition of gypsum (CaSO4) may be helpful. Although gypsum does not alter the soil pH, it can infiltrate the soil profile and reduce the amount of soluble Al. Research with alfalfa has shown significant yield increases in response to gypsum application on some soils with acidic subsoils. A subsoil sample (soil from deeper than 15 inches) must be tested to determine whether gypsum is needed and if it will decrease toxic levels of Al.

Fertilization

Alfalfa has a high nutrient requirement, especially when the nutrients are removed from the field as hay or silage. For example, each ton of alfalfa hay may remove as much as 15 lbs. of phosphate (P2O5) and 60 lbs. of potash (K2O). Productive, high-yielding stands require that these nutrients be returned to the soil through fertilizer, manure, or other sources in order to maintain yields and persist. Thus, annual alfalfa field soil sampling and testing is critical for tracking soil fertility levels and nutrient needs. Soil samples should be taken at the same time each year. It is also recommended that the soil test information be supplemented with occasional plant tissue analyses (See the “Plant Analysis” section.)

Nitrogen:

In well-managed stands, the nitrogen-fixing bacteria that colonize nodules on the alfalfa roots will meet the crop’s nitrogen requirement. Nitrogen-deficient alfalfa is commonly a symptom of a soil pH that is too low. Soil pH markedly affects the activity of the rhizobia bacteria that fix nitrogen. Nitrogen deficiencies will also occur if the seed was not inoculated properly before planting or if, for some other reason, nodules have not developed. When this occurs in soils that have a pH of 6.5 to 7.0, the poor nitrogen fixation may be the result of other nutrient deficiencies such as boron, calcium, magnesium, molybdenum, etc.

To diagnose nitrogen deficiencies, dig up suspect plants and check the nodules. Active nodules, when cut in half, are dark pink or red in color. A brown, black, green, or pale pink color denotes an inactive nodule. Also, determine the soil pH and analyze the plant tissue for nitrogen. Nitrogen-deficient plants turn pale green with a slight yellowish tinge. Later, leaves may become distinctly yellow.

Phosphorous:

Phosphorus is an essential element for many vital alfalfa processes (e.g., root development, energy transfer, etc.). Soil phosphorous levels should be adjusted by fertilization prior to seeding and sufficient phosphorous should be applied in subsequent years to maintain adequate soil test levels. This element does not leach from the soil, so one application per year is sufficient.

Phosphorus levels in most of Georgia’s soils are naturally low. Phosphorus deficiency symptoms are not as well-defined as those of many other nutrients. In general, P-deficient alfalfa stands will be stunted, the leaves may be upward-tilting and much smaller than normal, and older leaves may be stunted and dark green or purple. Symptoms may also include a decreased growth rate, reduced nodulation, and delayed maturity. Phosphorus-deficient plants may appear grayish-green and resemble drought stress, even with adequate soil moisture.

Potassium (K):

For alfalfa, potassium is essential for high yields, persistent stands, and disease resistance. This element, which is second only to nitrogen in concentration in the plant, affects plant vigor, forage quality, winter survival, and stand life.

For most sites in Georgia, K deficiency will be the most common and most problematic issue. Potassium deficiencies in alfalfa are easily recognized. White spots appearing along the margins of older leaves are an early indication of K deficiency. In time, tissue between the spots turns yellow and dies. Since potassium is a mobile nutrient in plants, symptoms first appear on leaves that are lower in the canopy, and the severity of yellowing increases from the top to the bottom of the affected shoots.

Potassium deficiencies can be prevented and stand life prolonged by a good K fertilization program. Soil test K levels should be high or supplemented with K2O fertilizer when alfalfa is planted. Annual soil testing and recommended K fertilizer applications will be crucial to ensuring that this critically important nutrient is not deficient. Tissue analyses taken prior to early summer harvests will help verify that K levels in the plant are maintained at or slightly above sufficiency levels (1.8 to 2.0 percent).

Potassium graphic

Multiple K applications will be more efficiently used by plants and will ensure that an adequate supply is available throughout the growing season. On heavy soils in the Piedmont and Mountain regions, two (spring and fall) or three (spring, summer, and fall) applications during the growing season are recommended. Sandy soils in the Coastal Plain do not hold K as well as the heavier soils in north Georgia. As a result, more frequent K applications are recommended. Four applications (late winter, early summer, late summer, and fall) should be suf

Status and Revision History
Published on Jan 9, 2009
Reviewed on Jan 9, 2012
Reviewed on Jan 23, 2015