Warm Season Legumes in South Florida Pastures

August, 2014
Aaron Stam, Ag/4H Extension Agent, Seminole Tribe

Legumes are a family of plants that are able to take nitrogen from its inert molecular form (N2) from the atmosphere and convert it into nitrogen-based compounds that are available to plants in the soil. This nitrogen conversion takes place through a process known as nitrogen fixation.  Nitrogen fixation leads to the forming of ammonium in the plant’s root nodules (NH4+). Microorganisms in the soil and root nodules act upon the ammonium and it is broken down into nitrate and nitrite.  Plants use the nitrates created during the nitrogen cycle to create the proteins and enzymes that plant cells use to store and transfer energy.

Legumes can offer a second benefit in pastures. Besides adding nitrogen back into the soil, they offer an extremely nutritious feed source. Legumes can also be very site and soil specific. A soil test is the easiest and most effective way to insure you are working with all the facts prior to planting. A legume that works well in one pasture may not flourish in another nearby pasture. Producers may need to research and experiment with legumes to find the right forage for their pasture. There are many variables that can affect legume production, so producers must stay open minded and continually evaluate the value of their legumes. Many producers favor legumes in creep pastures for their calves, while others mob graze pastures with legumes for short periods of time. Finding the right forage for your grazing system and pasture will require research and patience, but in the end, high quality forage is worth the effort. Proper grazing management with legumes can avoid large fluctuations in forage quality during the year.

In the warm season, there are three prominent, cattle palatable legumes that can be grown in South Florida pastures. They are:  Florida Carpon Desmodium, Aeschynomene, and Alyceclover.
There are other cool season legumes that offer the same benefits as the warm season legumes, but for the purpose of this article I am only dealing with warm season legumes.

Carpon desmodium is a perennial warm season legume that has adapted well to Florida flatwoods soil. Seedlings are susceptible to both draught and flooding failure, but after the plants have become established they can tolerate excessive moisture and severe spring draught.  Most of the plant’s growth takes place from summer to early fall. The plant’s foliage can contain between 12-20 percent crude protein. By fixing nitrogen in the soil, carpon desmodium has the ability to add the equivalent of 30 to 75 lb./A of nitrogen to the soil.

There are several options for the establishment of carpon desmodium; the first is planting in a cleaned and tilled seedbed. Soil should be rolled, seeded and then rerolled. This insures the small seeds are no deeper than one half inch deep, while also insuring there is good soil to seed contact.  This is an excellent method for planting along with bahiagrass during bahiagrass establishment.  Planting into an established sod requires heavy grazing prior to a light disking to prepare the soil to receive the seed.  A third method of seeding would involve the burning of the pasture in late February, and broadcasting seed into the ash, followed by a light disking and rolling.

The ideal pH for carpon desmodium is 6.0. Fertilizing should be based off soil tests of the pastures where it is being grown. Nitrogen fertilization is not recommended.
More information can be found in the EDIS SS-AGR-112 publication UF/IFAS Florida Carpon Desmodium.

The second, warm season legume is common aeschynomene. It is an annual plant with the ability to reseed itself for several years after its initial establishment. Common aeschynomene is best suited for fertile, moist soils, and prefers wet conditions to draught. The ideal pH of aeschynomene is between 5.5-6.0. No nitrogen fertilization is recommended. Aeschynomene seed can be purchased with or without seed hulls attached. There are twice as many seeds per pound when the seed hull has been cleaned (removed) from the seed.  Seeding date of aeschynomene is critical. It is typically planted in the summer to insure adequate moisture. It is recommended that if there have not been legumes of the cowpea group in the pasture, the seed should be inoculated prior to planting.  If seeding into established bahiagrass pastures several steps should be taken to promote success. The first is burn off excess bahiagrass in late winter, the second is no application of nitrogen during spring planting, and the third is to remove bahiagrass immediately before planting by grazing or chopping. Aeschynomene is best suited for grazing. It does not perform well when cut for hay.

If self-seeding of the established aeschynomene is desired, remove all cattle from mid-August through November to allow the plant to flower and set seed.
For more information see the EDIS SS-AGR-61 publication UF/IFAS Aeschynomene.

The third warm season legume is Alyceclover. It is a late season, annual legume native to the tropics in Asia, but has adapted well to south Florida pastures. It can re-establish itself through self-seeding, if the crop is allowed to make seed in the fall. Alyceclover is suited for well-drained soils, and does not perform well on soils that flood. It is also highly susceptible to rootknot nematodes.  For the establishment of alyceclover, sod should be grazed closely and cut with a chopper. The chopping exposes soil and allows seeds to come into direct contact with the soil for better germination. Seeds may also be established through drilling, which eliminates chopping, but sod should still be grazed low prior to planting. Seeds can be inoculated with cowpea type inoculant (N fixing bacteria) prior to seeding. Alyceclover prefers a pH of 5.5-6.0. Soil tests should be done to determine if fertilization is required. It can be heavily grazed in the pasture, and makes excellent hay, if cut before it’s overly mature. Cuttings should be made when it is 18-24” tall, leaving 3-4” of stubble. Alyceclover can be grazed when plants are around 12” tall. Significant gains of .3-.5 lbs per day were seen in four-month-old calves that were allowed to graze alyceclover in a creep pasture. For additional information about alyceclover see the EDIS SS-AGR-47 publication Alyceclover-Summer Annual Legume.

By selecting the right legume for addition to your pasture, you can reduce the amount of nitrogen fertilizer needed, reducing your expenses. Legumes also provide quality forage for your cattle.  Choosing the right legume or legumes for your pasture will take time and effort, but in the end legumes can add value to your pasture, and money to your wallet.

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