Sweetclover Production and Utilization in Indiana

C.L. Rhykerd and B.J. Hankins
Agronomy Department, Purdue University
Cooperative Extension Service
West Lafayette, IN 47907

SWEETCLOVER CHARACTERISTICS
SEED SELECTION AND PLANTING
FERTILIZING AND LIMING
SWEETCLOVER FOR USE AS A LIVESTOCK FEED
MINIMIZING PROBLEMS IN FEEDING SWEETCLOVER
OTHER USES OF SWEETCLOVER

Sweetclover is grown by beef and dairymen for forage, by conservationists for soil stabilization and improvement, and by beekeepers as a nectar source. The two species of importance to Indiana, Melilotus officinalis and M. alba are predominantly biennials. Of the several annual sweetclovers, the variety Hubam is by far the most common in the Midwest.

Two species of Melilotus (us are not recommended for growing in Indiana-sourclover (M indica) and Golden Annual sweetclover (M. sauveoten). Sourclover, an annual grown as a green manure crop in the southwestern United States, is not useful here due to low yield and palatability. Golden Annual has sometimes been sold in the Midwest, but has no advantage over Hubam.

This publication deals primarily with the biennial sweetclovers. Discussed are their characteristics; variety selection, planting and fertilizing recommendations; and management if to be used for feed, nectar, soil improvement or seed. Also given are suggestions for minimizing potential problems in the feeding of sweetclover to livestock.

SWEETCLOVER CHARACTERISTICS

Sweetclover is an `undemanding' legume. That is, like lespedeza, it grows where alfalfa, red clover and ladino fail, such as on clay pan soils or on sands; it tolerates low fertility and wet conditions; and it survives drought about as well as alfalfa.

Sweetclover utilizes phosphorous that other forage legumes do not. But it requires a soil pH of 6.5 or more for good root nodulation and maximum growth. Although biennials are by far the most widely grown, annuals can be used in emergencies if for some reason biennials cannot be grown.

Growth Characteristics

Biennials are usually seeded in the spring. During that first year, the above ground growth consists of one main stem having many branches. Late in the season, crown buds form at the base of the stem. After lying dormant over winter, these buds give rise to several stems that produce heavy growth the next spring.

If weed or grass competition is significant in the first year. the crown buds abort, leaving only an undesirable single stem for regrowth.

Biennials usually do not bloom during the seeding year. The following year, the plants should flower, set seed and die. But again, the stronger the competition from weeds or other forages, the less likely they are to bloom.

Visual Appearance

Sweetclover grows 2-6 feet high and produces either yellow or white flowers. The yellow-flowered varieties bloom roughly 2 weeks earlier than the white-flowered ones, and also mature earlier. The yellow varieties are usually less upright, finer stemmed, less productive and less winter-hardy. But they persist better in pastures and tolerate adverse conditions better than white varieties.

Sweetclover looks much like alfalfa. However, the two forages can be distinguished by their leaves. While both have three leaflets per leaf, the margins of alfalfa leaflets are serrated only on the tips; sweetclover leaflets, on the other hand, are serrated around their entire margin.

Other differences are that (1) sweetclover loaves, when crushed, have a distinctive sweetclover odor, and (2) the ear-like stipule at the base of each leaf is much smaller on sweetclover than on alfalfa.

SEED SELECTION AND PLANTING

Table 1 lists and describes most of the sweetclover varieties; consult with your seedsman about others that may be available. Keep in mind when selecting that yellow-flowered varieties tend to reseed themselves more rapidly than white-flowered, and that ones having larger seeds tend to germinate better and produce larger seedlings than smaller seed types. However, regardless of the variety selected, all seeds should be well-inoculated and scarified (scratched) to encourage more rapid and complete germination.

Table 1. Characteristics of Sweetclover Varieties Developed in the U.S. and Canada.

Variety and biennial (B)
      or annual (A)   Flower color          Origin and brief description
-----------------------------------------------------------------------------------------------------------
Common* (B)              Yellow     Generally the most available `variety'
Madrid (B)               Yellow     Drought tolerant; somewhat later than Common yellow
Goldtop (B)              Yellow     Matures 2 weeks later than Madrid yellow; forage yield 
				    and quality better than Madrid.
Erector (B)              Yellow     From Canada; first year's growth more erect than Common yellow.
Yukon (B)                Yellow     Canadian selection from Madrid yellow; forage and seed yield 
				    as good as or better than Madrid.
-------------------------------------------------------------------------------------------------------------
Common*   (B)            White      Generally the most available `variety'
Spanish    (B)           White      Good forage yield the first year; medium maturity
Evergreen   B)           White      Coarse, tall, late maturity.
Sangamon   (B)           White      From Illinois; flowers 2 weeks later than Common white.
Grundy  County (B)       White      From Illinois; low forage yield; early maturity.
Willamette (B)           White      From Oregon, similar to Spanish white.
Cumino      B)           White      From Canada, low coumarin content (nonbitter); early maturity.
Denta (B)                White      Low coumarin content (nonbitter); 3-4 weeks later than Common white.
Brandon     B)           White      From Canada; early maturity
Arctic (B)               White      Not adapted in U.S.; very winter hardy; early maturity.
Polara B)                White      Not adapted in U.S.; similar to Arctic white except low coumarin.
Alpha (B)                White      From Canada; not adapted in U.S. except northern border
-------------------------------------------------------------------------------------------------------------
Hubam (A)                White      From Iowa; blooms from late summer until frost.
Israel (A)               White      Similar to Hubam but newer; grown in southern U.S. as winter annual.
Floranna (A)             White      Similar to Hubam but produces more winter growth in southern U.S
-------------------------------------------------------------------------------------------------------------
* "Common' is the name applied to seed harvested locally from an unspecified variety

      

Plant sweetclover seed at the rate of 10-15 pounds per acre and at a depth of 1/4 - 1/2 inch. Spring seeding is preferred; late summer seeding tends to die the following July, with second year production reduced by about 25 percent.

Spring seeding should be done in March or April (about oat planting time), because sweetclover requires a good supply of moisture and cool temperatures for germination and early seeding growth. These conditions are lacking when seeding is delayed until after small grain harvest.

Oats at no more than 45 pounds per acre or wheat at 1 1/2 bushels per acre may be seeded as a companion crop, or herbicides used instead. Oats is a better companion crop because it offers less competition than wheat.

When the companion crop is harvested for grain or forage, leave a stubble of 6-14 inches high. Lower clipping may reduce crown development of the sweetclover.

If sweetclover remains unattended beyond flowering, the seed produced may fall to the ground and account for volunteer stands in future years. Much of the seed is hard, some so hard that it may remain viable in the soil for 20 years or more before germinating.

FERTILIZING AND LIMING

Sweetclover should be fertilized similar to alfalfa. Follow soil test recommendations to determine fertilizer rates needed. As a rule, each ton of forage produced removes 10-15 pounds of P₂O₅ and 40-60 pounds of K₂0; so the same amounts must be returned to the soil in the form of fertilizer.

If an oat or wheat companion crop is used, fertilizer for the sweetclover may be applied when the field is fertilized for the small grain. While a heavy amount of nitrogen applied to the companion crop encourages tillering {stooling) and vigorous top growth, it can also damage the sweetclover stand. Therefore, limit nitrogen fertilization to no more than 40 pounds per acre, and apply no nitrogen to the sweetclover in its second and succeeding years.

Sweetclover demands a `sweet' soil; therefore, lime it to a pH of at least 6.5. If more than 4 tons of lime are needed, at least half the recommended rate should be plowed down 6-12 months ahead of planting, with the other half applied just prior to planting and disced into the soil.

MANAGING SWEETCLOVER FOR USE AS A LIVESTOCK FEED

This section suggests how to manage a sweetclover stand for pasture, hay and silage.

Pasture

For livestock, sweetclover is best as a pasture and will likely produce enough growth for grazing if no companion crop is used. In the first year, it can be lightly grazed once it reaches 12-14 inches high, but must be rested during September and early October when buds are forming. If grazed again after bud formation, make sure cattle leave at least a 6-inch stubble. Closer grazing within the seeding year markedly decreases second year production.

In the spring of its second year, sweetclover is a prolific producer, and animal performance may equal that on alfalfa. As a summer forage, however, it is less dependable than in spring and seldom produces much after July.

Because second year spring growth is so rapid, start grazing when plants are 6-8 inches tall. If cattle keep this spring growth grazed down, the grazing season can be extended into July and August. A grazing pressure of 3-4 head per acre may be needed to prevent the crop from flowering and becoming woody.

The best grazing on sweetclover in Indiana is from early May to late July. But some farmers have gotten as many as 110 days off such pasture. Their secret is to graze it enough that the plants don't flower but not so much that regrowth is killed.

Hay

Sweetclover is not a good hay species because it tends to be stemmy. If used for hay, however, a nonbitter variety, if available, is best in order to avoid `sweetclover disease' (see below). Yellow-flowered varieties generally produce finer stems than white-flowered varieties, but the trade-off is usually lower yields,

If 19-24 inches of growth accumulate the first year, biennial sweetclover could be cut for hay. However, this may kill many of the buds and reduces second year production. To minimize that problem, cut after the root storage period of growth (early October) and leave at least a 6-inch stubble for winter protection. Although difficult, it is possible to get more than one cutting from second year sweetclover, provided the first cutting is made in the bud stage. If the crop is cut in full bloom, the hay will be stemmy and difficult to cure, and the remaining stand will likely die.

Remember, the older the plants are when first harvest is made, the higher the stubble height should be in order to encourage regrowth. Since it is the buds along the stem base rather than from the crown that give rise to the regrowth, the stubble must be high enough to have buds on it--i.e., at least 6 inches.

If annual sweetclover is used for hay, it should also be cut before flowering.

Silage

If to be used for silage, cut sweetclover before it blooms. Since the silage may contain dicoumarol, which causes sweetclover disease, wilt it to 65 percent moisture at ensiling, add 200 pounds of corn or 100 pounds of molasses per ton, and pack firmly.

MINIMIZING PROBLEMS IN FEEDING SWEETCLOVER

There are several potential animal health problems associated with the feeding of sweetclover. But each can be prevented or minimized as follows:

Sweetclover Disease

Sweetclover plants contain the chemical coumarin, which reaches its highest levels in the late bud or early flower stage of growth. Most of the material is concentrated in the leaves and flower buds.

Excessive moisture in the forage may lead to the formation of a chemical compound called dicoumarol, which reduces the ability of blood to clot. Cattle that eat spoiled sweetclover hay or silage can die from the bleeding disease that results. Unfortunately, spoilage may not always be detectable.

Younger animals are more susceptible to sweetclover disease than older ones. The disease is less of a threat in sheep and almost negligible in horses. Also, there is little danger of the problem occurring when sweetclover is pastured.

To help prevent the disease, dilute sweetclover hay or silage with twice as much non-sweetclover forage. Or feed sweetclover no longer than 10 days at a time, then switch completely to another forage for a while before returning to it. Still another preventive measure is to use a non-bitter sweetclover non-bitter varieties do not become toxic.

Bloat and Scours

Cattle may scour or bloat on sweetclover pasture, although the problem is more likely on alfalfa, red clover or alsike clover. The usual preventive measure is to feed dry hay or an anti-bloat material to the animals while on pasture.

Off-Flavors in Milk

Coumarin in sweetclover may, on occasion, impart a bitter flavor to milk when cattle are on pasture. The flavor is no more undesirable than that from feeding corn silage. A common precaution is to remove the animals from pasture several hours before milking.

Palatability

Cattle first turned onto sweetclover pasture may refuse to graze because of the bitter coumarin taste. However, they generally become accustomed to it in a short time. Sweetclover is least bitter in the spring.

OTHER USES OF SWEETCLOVER

Sweetclover is also grown for nectar in honey production, for plowdown to improve soil and for seed production.

Nectar for Honey Production

Sweetclover is an excellent source of nectar; in fact, `while-flowered sweetclover is considered by many to be the best honey plant. A good bee pasture usually consists of several varieties of both yellow and white-blossom biennials to stretch the flowering season.

Flowering in any given field may be extended by mowing a portion of it in the late bud stage of growth; but be sure to leave at least 6 inches of stubble for regrowth. In addition, the annual white variety Hubam, if spring seeded, will begin to flower in late summer and continue until frost.

One hive of bees per acre is considered adequate for good pollination.

Plowdown for Soil Improvement

Sweetclover plowed down can significantly benefit succeeding crops and improve the drainage, aeration and physical condition of soil. The Ohio data in Table 2 show when dry matter accumulates and how much nitrogen is produced by plowdown.

Table 2. Average Dry Matter Yield and Nitrogen Production of Sweetclover When Plowed Down at Various Stages of Growth (Ohio Data).

 
               Air dry yield   Nitrogen produced
                ------------  --------------------
  Date          Tops   Roots  Tops   Roots  Total
--------------------------------------------------
                pounds/acre pounds/acre
  Seeding year
   July 1        516     -     16     2      16
   September 1  1431   577     41    16      59
   November 1   1616  2115     39    74     113

  Second year
   April 1       420  2130     19    92     111
   May 1        1930  1360     75    49     114
   June 1       4940  1200    133    29     162
----------------------------------------------------
      

Sweetclover is most often plowed down in the spring of its second year, usually when the new growth is about 6 inches high. However, it could be plowed in the fall of the first year without losing much of the nitrogen that accumulates over a 2-year period. If the crop is to be plowed down in the seeding year, an annual type is best. The reason is that fall plowing does not always successfully kill the crowns of biennial varieties; thus they become weeds in successive crops.