Establishing Birdsfoot Trefoil in Bluegrass Sod
Howell N. Wheaton
Department of Agronomy
Birdsfoot trefoil and Kentucky bluegrass will produce three times as much beef as unimproved bluegrass. Even heavily fertilized bluegrass will produce only 65 percent as much animal product as trefoil-bluegrass combination. See Table 1.
Performance of steers grazing birdsfoot trefoil (1964-68).1
|Treatment||Average daily gain||Steer days per acre||Beef per acre|
|Unimproved grass||1.18 pounds||67||80 pounds|
|Improved grass plus N, P and K||1.29 pounds||187||238 pounds|
|Birdsfoot trefoil plus P and K||1.70 pounds||215||362 pounds|
1Iowa State Data from Albia Experiment Station
Trefoil is especially adapted to Shelby and Grundy soil types and other similar soils of northern Missouri. A major problem has been the difficulty of obtaining good trefoil stands. Its high requirement for light during the first 60 to 90 days after seeding is largely responsible for this. This can be overcome by band-seeding well inoculated trefoil seed in a partially tilled bluegrass sod during late February or early March.
- Overgraze the old sod
During the late summer and fall months prior to spring seeding, graze to remove all the top-growth and weaken the sod as much as possible.
- Take soil tests
Take soil tests in the fall and apply needed lime, phosphate and potash as soon as possible. Lime, if needed, should be fall applied. Trefoil will grow and establish itself if the salt pH is as high as 5.5. But applying lime to raise the salt pH above 6.0 before establishment is a sound management practice. The lime will be worked into the top 4 or 5 inches of soil and it will not be necessary to relime for a number of years.
- Partially tear up the old sod
This can be done any time during the fall or winter prior to seeding. A disc, field cultivator or similar tool may be used to destroy about 60 percent of the grass. Don't work it too deep or drive too fast. Leave the old litter on top. A rough seedbed absorbs moisture and prevents erosion. There will be enough tillers and clumps of bluegrass remaining for a quick stand of grass. The old sod will also act as a mulch to hold back weeds.
Seed 4 to 6 pounds of Dawn or Empire trefoil in late February or early March. Damage from frost is not as severe a threat to the new seedings as competition from weeds if the trefoil is seeded later.
- Use the right seeding method
The key to successful seeding of trefoil in bluegrass sods is band seeding. Use 50 to 100 pounds of phosphate as a starter. Do not use nitrogen; it also is not necessary to have potash in the starter. A grain drill may be cheaply and easily converted to band seeding. The short tubes of the grass seed box are replaced by longer ones and fastened just behind the grain fertilizer tube outlets. This will place the trefoil seed directly above the bands of phosphorus fertilizer.
Band seeding places the seed directly over the phosphate fertilizer where seedling roots can easily reach the fertilizer. This seeding method usually results in a 30 to 50 percent increase in seedling survival, more vigorous plants and higher initial yield. (A) Legume seed. (B) companion crop seed. (C) fertilizer
Seeds placed over bands of phosphorus will grow rapidly and develop strong root systems. They will survive competition from grass, weeds and drought better than broadcast seedings.
Take off the drag chains; they scatter the seed away from the fertilizer. The new seeding may be packed or rolled, but if the seeding is made early, it is not necessary. Freezing and thawing will soon cover the small trefoil seed with soil.
- Management of the new seeding
As soon as the grass begins to grow in the spring and the sod is dry enough so that trampling will not occur, graze the renovated field. The early grass must be grazed to make renovation successful. The new seedings may be controlled grazed throughout the season to remove the grassy growth.
Let the new trefoil rest throughout the month of September and early October. This is a critical time in the life of a trefoil plant. The growth that occurs during this period may be used during late October and November.
- Don't forget to inoculate
Never seed trefoil without using the specific inoculant needed by trefoil. Follow directions and use plenty of inoculum. Always use water or some sticky liquid to make sure the culture sticks to the tiny trefoil seeds.
- Use chemical weed control
Chemicals may be especially helpful because trefoil is not a strong early competitor. This has been the most successful method in establishment. Some of the chemicals used to control weeds in new trefoil seedings are:
Don't work into the soil too deeply
Eptam will control weedy grasses and in most years will control broadleaf weeds.
- Balan (1-1/4 to 1-1/2 pounds of active ingredient per acre). Use same procedure as with Eptam. Balan will control weedy grasses and most broadleaf weeds except ragweed.
- 2,4-DB (ester 1/2 to 3/4 pound or amine 3/4 to 1 pound of active ingredient per acre). These are to be used post-emergence to control broadleaf weeds. Apply when the weeds are small but the trefoil should be at least 2 inches tall.
Chemical weed control is excellent for successful seeding trefoil in an established grass sod. However, Eptam or Balan will kill new seedlings of other grasses such as timothy or orchardgrass if seeded with the trefoil. Post-emergence 2,4-DB may be safely used on grass-legume mixtures for broadleaf weed control without harming the new seedlings.
- Some other considerations
Volunteer lespedeza and summer annual weeds such as crabgrass and foxtail are fierce competitors for young trefoil seedlings. Fields severely infested with these species may be seeded in late summer to avoid competition. However, the sod will have to be tilled to a greater degree than if spring seeded and seedings should be made before the first of September.
- Seeding in other areas
Birdsfoot trefoil may be used as a companion crop to most grasses or in areas being removed from cultivation. However, it is better adapted for use with bluegrass, orchardgrass or timothy.
Seeding rates for such permanent pasture mixtures are: five pounds birdsfoot trefoil and two pounds timothy (or three pounds orchardgrass) per acre.
Avoid using oats or wheat when seeding trefoil unless the companion crop can be removed by grazing.