What are Annual Medics?

Gary R. Bauchan
USDA-ARS, Soybean & Alfalfa Research Lab., Beltsville, MD 20705-2350

Medics are annual species of Medicago which are closely related to alfalfa. The annual medics are endemic to the Mediterranean region of the world. The medics are fast growing and true annuals were most of them will complete their life cycle in 65 to 100 days. Medics appear to be best adapted to soils with a pH of 6 and above, however, some species are more tolerant to low pH soils such as M. murex. Medics have been found to produce up to 200 pounds of nitrogen per acre provided effective inoculant is used. Medics should be inoculated with a appropriate Rhizobium as the standard strains used for alfalfa may not be effective. Medics can be cut for hay with an average yield of 1-3 ton/acre with a single cut taken at 60-70 days after planting. Because medics tend to lodge and may be difficult to cut and bale, grazing may be a suitable alternative. If the medics are grazed high with some stems remaining some regrowth may occur. Medics have quality potential similar to alfalfa which is influenced by the stage of maturity. They will cause bloat and need to be introduced slowly as part of a total ration or mixed with grasses. The annual medics are not cold hardy and they will die after a killing frost. Snail (M. scutellata) and gama medics (M. rugosa) have a natural resistance to the alfalfa weevil and the potato leafhopper due to glandular tipped hairs on the stems, leaves and pods. All of the medics have yellow flowers and are self pollinating, therefore they do not require bees for pollination. The seed pods are very unique and distinct with seeds larger than alfalfa. Typically the medics have greater seedling vigor than alfalfa especially the large seeded species. The seeds can remain viable in the soil for long periods of time and are thus able to reseed themselves after a period of time. However, if the medics are grown in areas where there is adequate moisture, softer seed will be produced and a second generation may be produced in a single growing season. The annual medics are used extensively in Australia on over 30 million hectares. They are utilized as a winter annual to improve soil structure, increase soil nitrogen and as a source of forage. The species most widely grown in Australia are: M. littoralis, M. polymorpha, M. trucatula, M. scutellata, M. rugosa, and M. italica (Crawford, 1989). Renewed interest in sustainable agriculture systems has placed renewed interest on legumes. Annual medics may have the potential of being utilized in various sustainable systems. Some potential uses are: 1) pastures, either in a lay farming application or permanent pastures, 2) green manure produced as green fallow or cover crops, and 3) companion or smother crops for weed control. The Australian medic collection contains over 21,000 accessions and the U. S. collection contains 3,000 accessions A core collection has been designated for both collections which is composed of 1705 and 211 accessions, respectively (Skinner et al. 1998 and Diwan et al., 1994) These core collections can be utilized as a small subset of the larger collections which can be evaluated for local adaptation and potential utilization.

References

Crawford, EJ, Lake, AWH, and Boyce, KG. 1989. Breeding annual Medicago species for semiarid conditions in southern Australia. Advances in Agronomy 42:399-437.

Diwan, N. Bauchan, GR, and McIntosh, M. 1994. A core collection for the United States annual Medicago germplasm collection. Crop Sci. 34:279-285.

Skinner, DZ, Bauchan, GR, Auricht G and Hughes, S. 1998. A Method for the Efficient Management and Utilization of Large Germplasm Collections. Proceedings of the 35th North American Alfalfa Improvement Conference.