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Plan for Success with Legumes

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Posted Aug. 31, 2008

The old adage
"Just because something can be done does not necessarily mean it should be done" might apply if you are considering planting legumes this fall. September is the time to plant alfalfa and the time to plant clovers comes soon after. Are you really prepared or should you actually be preparing for next year?

To have legumes in your pastures, you obviously need to plant them. But just because you plant them this fall, it does not mean they will be there next spring. What is the probability of success? Have you done everything possible from a pasture management standpoint? Is weather the only variable left to chance? Most crop failures are due to poor preplanting preparation, so the checklist below is a quick indicator of your readiness. If you answer "no" to anything in the list, well, you might not finalize those plans to "roll in the clover" next spring.

Have the soils been tested and show a pH between 6.0 and 8.0?
If lower, you need to apply lime at the required rate to raise the pH to at least 6.0. Additionally, be sure that there are no nutrient limitations that would inhibit legume growth such as low phosphorus and potassium.

Is any herbicide residue present in the soil?
Ideally, pastures to be planted to legumes have had no herbicides applied in the past year or have had only a contact herbicide that has no soil activity. Roundup® (glyphosate), 2,4-D, Weedmaster®, Banvel®, Pastureguard® and Remedy® are examples of herbicides with minimal soil activity to fall-planted legumes at commonly used rates when applied in spring. Herbicides such as Amber®, Cimarron®, Cimarron Max®, Grazon P+D®, Grazonnext®, Tordon® and Milestone® are some of the more common herbicides used that have more soil carryover potential. Consider waiting until the following year to plant legumes if you used herbicides this year with soil carryover potential.

Is the pasture grazed short with a minimal amount of residue or litter on the soil surface?
If you have mowed the pasture recently, or intend to prior to planting, and there is (or will be) a mat of residue covering the area, you do not have a desirable planting environment. Legumes need open space to grow and a mat of thatch prevents that. You need to have some bare or exposed soil for best results.

Has a legume been selected, located and purchased that fits your soil and environment?
Remember that preparation includes an inoculant if seed is not pre-inoculated. As a rule of thumb, the smaller-seeded legumes work best east of I-35 with higher rainfalls, and perennial clovers work best as you move north and east of Ardmore, Okla. If you are west of I-35, you may be limited to the larger-seeded legumes. Alfalfa works best as a monoculture crop whether haying or grazing and is considered the most reliable legume in our region.

Have you prepared a smooth, firm, fine seedbed?
When walking across it, your boot heel, but not the sole, should leave an impression.

Is equipment to plant legumes calibrated and in working order?

Other Things to Remember When Planting Legumes

  1. Plant when soils have good moisture; larger-seeded legumes are more tolerant of drier conditions.
  2. Legumes in pastures will limit spring herbicide options.
  3. Provide bloat prevention safeguards to grazing livestock.
  4. For maximum nitrogen (N) fixation for a summer pasture, allow legumes to grow in the spring (defer grazing). N will not be immediately available in the spring, but will become available over time as legumes decompose.
  5. For reseeding, allow legumes to produce seed by removing grazing livestock during the flowering phase.
  6. Legume-overseeded pastures will require some additional legume seeding in subsequent years, but at a reduced rate.
  7. Legumes are not as reliable as commercial fertilizer. If legumes are the only N source, adjust the stocking rate to a more conservative number (to a stocking rate without N) until a sustainable pasture-legume system is attained.
  8. The probability of legume establishment failure due to weather increases as you move from east to west within the Noble Research Institute's service region.