Scientific name(s)

Medicago orbicularis

Strengths

• Early flowering and seeding and well adapted to marginal climatic conditions
• High seed production
• High levels of hard seed and a slow breakdown pattern ensure large seed reserves
• Good nutritive value with high protein, palatable
  

Limitations

• Productive in good seasons but not as productive as barrel and strand medics in average seasons
• Regeneration not as reliable as other medics
• Aphid susceptible
• Seedling regeneration from the resilient seed reserve could pose a problem in crop rotations though readily removed by herbicide
  

Plant description

Plant: Prostrate with trailing runners

Stems: Trailing up to 50 cm long

Leaves: Trifoliolate; leaflets oval; leaflets 9-18 mm long, 6-14 mm wide, toothed almost to base, upper surface glabrous; lower surface glabrous or hairy.

Flowers: Inflorescences 1-5 mostly yellow, sometimes with mauve markings

Pods: Pod light straw coloured, spineless, flattened with papery edges, 3.5-7 mm long, 13-17 mm diam., coils 3-7, seeds 10-26

Seeds: Triangular to square in shape, flattened, yellowish brown

Pasture type and use

A self regenerating winter growing annual ley legume in dryland cereal growing regions in the Upper Eyre Peninsula and Mallee of southern Australia and in pastoral systems in subtropical Australia.
Used in marginal cropping and grazing environments owing to the resilience of the hard seed reserve.

Where it grows

Rainfall

Requires an annual rainfall of 200-650 mm/ann in southern Australia and 300-650 mm/ann in the subtropics.

Soils

Adapted to a wide range of alkaline soils, from sands and loams (southern Australia) to loams and heavy textured soils (subtropics).

Temperature

Winter growing, can withstand frosts.

Establishment

Companion species

In the subtropics it may be sown with any of the adapted tropical and temperate grasses, other adapted medics (particularly early flowering barrel and spineless burr medics) and Desmanthus and Caatinga stylo; in southern Australia, it may be sown with early flowering cultivars of hybrid disc medic, strand medic, spineless burr medic and barrel medic.

Sowing/planting rates as single species

2-3 kg/ha of scarified seed.

Sowing/planting rates in mixtures

Sow at a rate depending on the proportion in the mix.

Sowing time

Early autumn to early winter.

Inoculation

Group AM

Fertiliser

Where soils are low in nutrients, particularly P and/or S, it would be beneficial to apply 10-15 kg P and 10 kg S/ha annually, and Cu, Zn Mo if they are deficient. Soil tests will determine the need and appropriate rates.

Management

Maintenance fertliser

Ongoing applications of P and S as required. Soil tests will determine the need and appropriate rates.

Grazing/cutting

In the establishment year, delay grazing until plants are well established. Graze leniently until flowering then remove stock to maximise seed set.
Makes more production when rotationally grazed. Does not respond well to crash grazing.

Seed production

100-500 kg seed/ha, with 1200 kg/ha measured experimentally.

Ability to spread

Rate of spread slow but, because of its high hard seed levels, could be spread through livestock

Weed potential

Low weed potential owing to slow hard seed breakdown pattern. It is palatable and readily eaten. In ley systems, it could be a weed of cereal and grain legume crops

Major pests

Susceptible to redlegged earth mite,blue-green aphid, spotted alfalfa aphid and Cow-Pea Aphid

Major diseases

It is susceptible to powdery mildew

Herbicide susceptibility

Susceptible to residual herbicides from a cropping phase, particularly sulfonylurea on alkaline, sandy soils

Animal production

Feeding value

High levels of crude protein (17-22%), energy (8-10 MJ/kg ME) and digestibility (55-75% DMD) in leafy growth.

Palatability

Readily eaten by livestock. Anecdotal evidence is that pods are not readily sought by livestock.

Production potential

Button medic has a lower dry matter production potential than the barrel medics, but has produced 7 t/ha DM in a good season in the subtropics.

Livestock disorders/toxicity

Bloat can be issue with cattle.
Inoculate to prevent pulpy kidney

Cultivars

Further information

Forages of Texas - North Central Species (Button medic)
Oklahoma Forages (Button medic)

Acknowledgements

Jake Howie, SARDI

Author and date

Brian Johnson and David Lloyd

5 December 2008