Barrel Medic (McLeod, 1982).

The scientific name is Medicago truncatula Gaetrn (Mackay and Barnard, 1981).

'Jemalong', 'Sephi', and 'Paraggio' are mid-season-maturing, varieties; the former is an old variety, whereas the latter two are new (Miller et al., 1989). Other commercially-available varieties included 'Hannaford,' 'Cyprus,' 'Cyfield,' 'Borung,' 'Ghor,' 'Akbar,' and 'Ascot' (Weitkamp and Graves, 1988).

The current 1997 varieties used in California are 'Jemalong', 'Sephi', 'Parraggio', 'Parabinga', 'Mogul', and 'Caliph.' The other varieties listed--'Cyprus', 'Cyfield', 'Ghor', 'Akbar', and 'Ascot' are no longer commercially available.

Barrel medic has unique barrel-shaped seed pods (Peaceful Valley, 1988) or burrs, each containing from four to eight yellowish-brown, kidney shaped seeds. Seeds are 2.5 to 4 mm long and 1.5 to 2.5 mm wide and separated from each other in the burr by thin partitions (Quinlivan et al. 1986). For cv 'Cyprus', there are 125,000 seeds/lb (Murphy et al., 1976); for 'Hannaford' there are about 12,700 pods per kg and about 250,000 seeds per kg (Mackay and Barnard, 1981); and 'Hannaford' was estimated as having about 110,000 seeds/lb by Murphy et al. (1976). For 'Jemalong,' there are 110,000 seeds/lb (Murphy et al., 1976); for 'Paraggio' about 220,000 seeds per kg (Mackay and Barnard, 1981); and for 'Sephi' about 7-9 seed per pod and 260,00 seeds per kg (Mackay and Barnard, 1981).

M. truncatula is erect in growth habit, leaflets obvate with deeply serrate upper margin, purple flecked with a prominent blotch on the upper third, slightly hirsute.

'Paraggio' shows better seedling vigor than does 'Jemalong' (Mackay and Barnard, 1981).

The species has hairy stems and leaves; leaves are trifoliate, with oval leaflets, and the widest part towards the apex, which may be truncated or rounded. The leaves may be all green, or have distinctive purple blotches, features which have been used for cultivar identification. There are usually one or two flowers (or up to four in cv. 'Borung') on a hairy stalk which is shorter than the stalk of the corresponding leaf. Lobes of the floral calyx are very long and reach almost to the tips of the petals. The pods or burrs are barrel shaped, coiling clockwise or anticlockwise, and 4.5 to ll mm high, with three to seven coils which are strongly pressed together and thickened at maturity. Young burrs are hairy. Spines are variable: they may be short and thick at the base and pressed against the sides of the burr or longer and thinner and protruded at a slight angle. In cv 'Cyfield' and some naturalized material, the pods are spineless. The burrs have characteristic indentations along the margins of the coils between the spines, the presence of which distinguishes M. truncatula from M. littoralis, but these indentations may be obscured by strong thickening at maturity (Quinlivan et al. 1986). 'Borung' has clusters of three or four flowers, whereas most other cultivars have only two or three, and the burrs are smaller than in the other cultivars (Quinlivan et al. 1986). 'Cyprus' comprises several strains; the dominant strain is identical in appearance to cv 'Hannaford' and forms some 98% of the total in any stand. The main minor strain has, in the center of each leaflet, a dark purple-brown patch which is prominent during the winter but fades as the plants approach maturity (Quinlivan et al. 1986). 'Hannaford' resembles 'Cyprus' in that leaflets are unmarked and pods coil in a clockwise direction (Quinlivan et al. 1986).

'Jemalong' resembles 'Hannaford' and 'Cyprus' but is distinguished by the leaflet's central purple-brown patch which is prominent during the winter but disappears in the spring. 'Jemalong' also differs in that the pod is coiled in an anti-clockwise direction, while those of the other 'Cyprus' and 'Hannaford' coil clockwise (Quinlivan et al. 1986).

Closely resembling 'Hannaford,' 'Paraggio' is a typical representative of the species. Purple leaf flecking does not penetrate to the abaxial surface as in 'Borung' but is similar to 'Hannaford.' 'Paraggio' has clockwise pod coiling and a similar range of pod coil numbers to 'Hannaford' (3.5-5.25). Paraggio pods are slightly heavier (about 10,000 per kg). Pod spininess is rated as equal to 'Hannaford' and 'Jemalong' (Mackay and Barnard, 1981).

'Sephi' is a mixture of two components, which are morphologically distinguished only by a difference in markings on the abaxial surfaces of the leaflets. Eighty per cent of the plants have a lighter green "watermark" blotch mostly edged with brown on the distal part of the leaflets. The remaining 20% have a brown blotch on the mid-lower part of the leaflets. Both leaf markers disappear later in the life of the plant and may not be expressed during the warmer months of the year. The other main distinguishing feature of 'Sephi' is the pod, which is relatively squat with its length rarely exceeding its width. It contains 3 or 4 clockwise coils. The spines are somewhat longer and larger than those of 'Jemalong', have a rating of 12, but are considerably shorter than those of 'Ascot.' Spines of 'Sephi' have a similar curve to those of 'Akbar' (Mackay and Barnard, 1981).

Barrel medics succeed in Mediterranean climates, with cool, moist winters and long, hot, dry summers (Quinlivan et al., 1986).

For cover crops in the upper Midwest, barrel medics thrive vegatatively when spring sown and allowed to grow with the long day length and cool moist conditions of summer. However, they fail to properly initiate flower production and mature a good regenerating seed crop.

In California, Texas, and Oregon where winter grown barrel medic has been tested, the following general gradient of winter kill can be used as a guide:

Medics: 18°F (killing temperature) Berseem clover: 16°F Subclover sp. (varies): 14°F 'Hykon' rose clover: 10°F Crimson clover: 10°F 'Overton' rose clover: 0°F

Medics originated around the Mediterranean basin, and require long, hot, dry summers, and winter rain (Quinlivan et al., 1986). In general, medics require a Mediterranean climate with 250-500 mm of mainly winter rain (Quinlivan et al., 1986). Barrel medic is widely naturalized in New South Wales, Victoria, and South Australia (Quinlivan et al., 1986).

Rainfall amounts in California are closely related to soil pH. The determination of what will grow is based on the combination of two key factors. The following chart may help.

San Diego County: Acid soil, 8 inches of rain. 'Hykon" rose clover and 'Nungarin' subclover will regenerate and barrel medic will not.

San Luis Obispo County: Alkaline soil, 8 inches of rain. Barrel medic will regenerate 'Hykon' rose clover and 'Nungarin' will not. The only alkaline tolerant subclovers that could tolerate the alkalinity are 'Clare' and 'Koala' but they have a 16-18 inch rainfall requirement to complete their life cycle so they will not regenerate.

Barrel medic is a better choice for areas where rainfall is insufficient for true clovers (Trifolium spp.); that is where rainfall is less than 20" annually (Peaceful Valley, 1988). 'Cyprus' does well in regions receiving 10-16 inches; 'Hannaford', 10 -20" (Murphy et al., 1976). 'Jemalong' and 'Sephi' have shown excellent adaptation to both low and high rainfall (8-21 inches annually) (Weitkamp and Graves, 1988), but 10-17" is considered optimal for 'Jemalong' (Murphy et al., 1976). 'Paraggio' is adapted to rainfall of from 14-20 inches (Mackay and Barnard, 1981).

Clarkson et al. (1989) found that a single application of sulfur and phosphorus (both at 40 kg/ha) to a traprock soil (a shallow gravelly loam, pH 6.7) increased yield of barrel medic five-fold for the three years of the study. Dry matter yields rose from 400 to 2300 kg/ha.

Barrel medic requires neutral to alkaline pH (6.8 to 9.0) (Peaceful Valley, 1988). Murphy et al. (1976) stated that 'Cyprus,' 'Hannaford,'and 'Jemalong' grow well given soil pH of 7-9.

Adapted to alkaline to strongly alkaline soils especially with a high lime content. There is a preference for clay and clay loam soils over sand and sandy loams.

'Hannaford' and 'Cyprus' do well on alkaline soils or soils with a high content of available lime (Quinlivan et al. 1986). Murphy et al. (1976) mentioned that 'Hannaford' prefers medium to light alkaline soils, whereas 'Cyprus' does well on heavy soils and 'Jemalong' on calcareous, sandy soils. 'Jemalong' is considered superior to 'Hannaford' on many light calcareous sandy soils (Quinlivan et al. 1986). 'Paraggio' is adapted to a range of soil types from neutral to alkaline sands and sandy loams to heavy textured clay loam soils (Mackay and Barnard, 1981).

'Cyprus' is somewhat salt tolerant, and 'Hannaford' has done well in Australia on heavy clay loam soils which in their virgin state have a relatively high soil salinity (Quinlivan et al. 1986).

Barrel medic is a cool-season annual (Bugg, pers. comm.).

Peaceful Valley (1988) recommended sowing rates of from 8-15 lb/acre, whereas Miller et al. (1989) suggested 15 to 20 lbs/acre. Barrel medic should be sowed at 15-20 lb/acre for a great cover crop stand.

Peaceful Valley (1988) advised a sowing depth of 1/2-3/4 inches.

Glenn McGourty seeded cv 'Hannaford' barrel medic in a vineyard by disking twice to prepare the seedbed, broadcasting the inoculated seed, and incorporating with a cultipacker (Bugg, pers. comm.).

Seed in fall (Peaceful Valley, 1988).

Inoculation improves seedling emergence, N fixation, and growth (Peaceful Valley, 1988); the inoculant type is "Medicago Special Culture 1" (Nitragin Co.) (Burton and Martinez. 1980). 'Paraggio' nodulates effectively with commercially-available peat cultures of Rhizobium appropriate for barrel medics (Mackay and Barnard, 1981).

Seed of barrel medic is always available and abundant in Australia, except during severe drought years. Selected cultivars may not be available in California after October when the limited import of the cultivar is exhausted.

Days to flowering for several varieties were given by Weitkamp and Graves (1988): 'Akbar', 91; 'Ascot', 100; 'Borung', 95; 'Cyfield', 96; 'Cyprus', 78. Mackay and Barnard (1981) stated that 'Cyprus' flowers approximately 80 days after fall planting, whereas Murphy et al. (1976) stated that it flowers in January, and Quinlivan et al. (1986) that it flowers about 11 weeks after germination. Weitkamp and Graves (1988) state that 'Ghor' requires 90 days, 'Hannaford' 99, 'Jemalong' 105, 'Paraggio' 105, and 'Sephi' 105 (Weitkamp and Graves, 1988). 'Ghor' is mentioned as very early flowering; it begins flowering about two weeks earlier than 'Cyprus' or at about 9 weeks after germination (Quinlivan et al. 1986). 'Hannaford' flowers 3-4 weeks after 'Cyprus' Barrel (Murphy et al. 1976), with the interval from germination to flowering stated as about 14 weeks (Quinlivan et al. 1986). 'Jemalong' was mentioned as flowering 3-4 weeks after Cyprus Barrel (Murphy et al. 1976) and about a week after 'Hannaford', or about 12 weeks after germination (Quinlivan et al. 1986). 'Sephi' flowers up to a week earlier than Jemalong (Mackay and Barnard. 1981).

Barrel medic is regarded as early maturing (February-April) (Peaceful Valley, 1988), with cvv 'Borung' and 'Sephi' maturing about the same time as 'Jemalong' (Quinlivan et al. 1986; Mackay and Barnard, 1981).

For 'Jemalong', seed yields of 300 to 675 lbs/acre were obtained in an established stand in San Luis Obispo County (Weitkamp and Graves, 1988). Mackay and Barnard (1981) found that 'Sephi' is superior in seed yield to aphid-susceptible cultivars under attack by blue green aphids and spotted alfalfa aphid. When compared with 'Jemalong' and 'Paraggio,' 'Sephi' yielded significantly more seed.

Medic produces seed that is often 70-80% hard. To promote rapid germination, this seed is often scarified by the Australian producers so that it will germinate. Most seed for sale will be 75% germ and 25% hard the first season of import, because it was scarified. Raw imported medic seed will drop to 50% total germination in 3 years and 20% germination in 6 years.

Most medics produce hard seed (Quinlivan et al., 1986), which suggests that seed have long-term viability in storage, but no specific information was available on this point.

Medics are low growing (6-16" dependent on species) (Peaceful Valley, 1988). Being winter annuals, they dry up early and re-seed leaving a small amount of mulch for water conservation and weed control (Peaceful Valley, 1988). 'Jemalong' has a semi-erect growth habit that is purported to give it better winter production potential (Quinlivan et al. 1986), and 'Sephi' in turn has a slightly more erect habit than 'Jemalong' (Mackay and Barnard, 1981). 'Paraggio' has a growth habit that is slightly more erect than that of 'Hannaford' (Mackay and Barnard, 1981).

Height of cv 'Hannaford' was 40.01+/-1.91 cm (mean +/- S.E.M.) during early May in an organic vineyard in Hopland, Mendocino County, California (Bugg et al., 1996).

Like most legumes, barrel medic has a taproot-dominated root system (Bugg, pers. comm.), and root systems of medics are generally deeper than those of subterranean clovers (Quinlivan et al., 1986)

Glenn McGourty seeded cv 'Hannaford' barrel medic in an organic vineyard in Hopland, Mendocino County, California, by disking twice to prepare the seedbed, broadcasting the inoculated seed, and incorporating with a cultipacker (Bugg, pers. comm.). This was followed by 1 inch of overhead irrigation. Establshment was excellent.

According to Fred Thomas (pers. comm.), medics fare relatively well when there is some early autumn rain followed by a dry spell, because medic root elongation is rapid. By contrast, subterranean clover roots elongate more slowly, and those clovers benefit from more consistent soil moisture.

Crawford and Nankivell (1989) evaluated the annual medics, Medicago rugosa cv 'Paragosa', M scutellata cv 'Robinson', and M. truncatula cvs 'Cyprus' and 'Jemalong' in 3 rotational systems. Medicago spp. re-established better under permanent pasture than under any rotational scheme involving tillage. Seed preservation, however, was better in rotations involving tillage. Medicago rugosa cv 'Paragosa,' in rotation trials, produced a higher seed yield in the year of sowing than did M. scutellata cv 'Robinson' or M. truncatula cvv 'Cyprus' and 'Jemalong'. However, its seed bank persisted only 3 years, and its re-establishment was poor, perhaps due to its higher proportion of permeable seed. Medicago truncatula cv 'Jemalong' maintained higher seed reserves after six years of cropping than M. scutellata cv 'Cyprus' or M. scutellata cv 'Robinson'. Seed banks of all species were exhausted after 7 years. Natural regeneration by 'Paraggio' from residual seed was better than of 'Jemalong' under both sprayed and unsprayed conditions (Mackay and Barnard, 1981).

M. scutellata has very large seeds. To maintain a persistent stand of M. scutellata, they must be planted on alkaline soil, protected from early grazing and lightly incorporated in late summer by disking or harrowing to get the large seed down into the soil every other year.

The growth points of the semi erect presentation by decumbent medics is higher than for subclover. If a medic is 8 inches tall and mowed for the first time, the height should be 4-5 inches so as not to cut off the regenerating buds. If frequently mowed from an early stage 3 inches is fine all season as Miller suggests.

According to Rick Miller (pers. comm.), medics can tolerate close mowing if it is applied consistently. However, if the plants are allowed to grow erect and then mowed closely during spring, seed set can be greatly reduced. By contrast, subterranean clovers can tolerate extremely close mowing, consistent or occasional, and still set seed.

Barrel medic may be incorporated like any other annual cover crop. There are no special requirements, but tillage may place seed too deep to ensure stand regeneration. (Bugg, pers. comm.)

Seed pods can presumably be harvested by sweeping, as with burr medic (Duke, 1981).

The standard machine for medic harvesting is a Horwood-Bugshaw vacuum harvester. Recently, Revell seeds of Dimboola, Australia developed a custom vacuum harvester that is substantially faster.

Planting and growing barrel medic does not require any special equipment, but harvesting requires a vacuum harvester. Medic pods drop to the ground when mature, so a stem of barrel medic can have dropping pods, immature pods, and flowers all at the same time in April. This dehisence of the peduncle prevents swathing as an efficient means of harvesting and has led to vacuuming as the best method to get all the crop.

According to Peaceful Valley (1988), barrel medic is excellent for dryland orchards, vineyards, or crops with limited summer water (e.g., under drip & low volume irrigated crops) and is also suited for overseeding into bermuda grass lawns for winter color. It is credited with having excellent feed value and with being useful for planting in polycultures with grains (Peaceful Valley, 1988). The very early flowering and rapid winter growth of cv 'Ghor' suggest its possible use in dry regions (Quinlivan et al. 1986).

Christensen (1971) proposed winter cover crops for Californian vineyards with the aim of producing a sod-like condition. Cover crops should be low growing, require little or no mowing, and be self re-seeding. Their functions would be to reduce tillage and dust, provide habitat for predators that attack spider mites, improve water penetration, and provide nitrogen. Medics suggestions were California bur clover, 'Cyprus' barrel medic, and 'Harbinger' barrel medic. Medics are recommended in mixture with subclovers in some areas (see subterranean clover section) (Murphy et al., 1976).

Bugg et al. (1996) found that dry above-ground biomass for 'Hannaford' was 7.8+/-0.8 Mg/ha (Mean +/- S.E.M), in Hopland, Mendocino County, California. When weeds were included, the figures were 8.7+/-0.4.

Mackay and Barnard (1981) found that early winter herbage production for 'Paraggio' was significantly greater than for 'Jemalong', approximately 2,910 kg/ha. compared to 1,140 kg./ha. 'Paraggio' produced more herbage than 'Jemalong' and the mean of 56 other genotypes and was expected to increase the annual medic content of pastures over all except the lowest rainfall areas (less than 300 mm). 'Sephi', when compared with all currently available annual medic cultivars over a wide range of environments and herbage yield, was equal to or better than 'Jemalong,' 'Cyprus,' 'Paraggio' and 10 other aphid-resistant lines (Mackay and Barnard, 1981).

For burr medic, mean protein content is 19% by weight (Duke, 1981) and 6.3% of the protein is assumed to be N. Projecting from the biomass figures observed by Bugg et al. (1996) for cv 'Hannaford' barrel medic, 7.8+/-0.8 Mg/ha, the N yield probably was about 92.4 +/- 9.4 kg N/ha.

Materon and Danso (1991) found that in northern Syria, cv 'Jemalong' at the high seeding rate (500 seeds/m-2) yielded a mean nitrogen content of 89.3 kg N/ha (75.5 obtained from fixation, herbage yield 4.6 Mg/ha) when seed was inoculated with Rhizobium strain WSM244, and 71.8 kg N/ha (57.1 obtained from fixation, herbage yield 3.7 Mg/ha) with strain CC169. Uninoculated 'Jemalong' contained 30.4 kg N/ha (18.7 obtained from fixation, herbage yield 1.4 Mg/ha). The inferred N-fixation figures were based on data from control plots seeded to annual ryegrass (Lolium multiflorum). On the whole, cv 'Jemalong' produced only about one-third as much biomass as did Medicago rigidula L., selection 716. The latter derived on average about 91% of its N from fixation, and at high seeding rates contained 93.1 kg N/ha (WSM244), 112.6 kg N/ha (CC169), and 100.7 kg N/ha. Respective herbage yields were 5.5 Mg/ha, 5.4 Mg/ha, and 5.1 Mg/ha

No specific information is available on the effects on water by barrel medic. With their deeper taproots, medics might be expected to deplete soil moisture at depth more than do subterranean clovers (Bugg, pers. comm.).

Solid stands of barrel medic can lead to bloat in cattle, but it may not be as bad as with M. polymorpha which is smooth, glabrous. There is ample observation of bloat by medic.

Most medics have low concentrations of oestrogenic compounds. However, leaves and pods of cvv 'Cyprus,' 'Jemmalong,' and 'Hannaford' sometimes contain coumestan, especially 4-methoxy coumesterol, an oestrogenic compound that may induce abortions in sheep (Quilivan et al., 1986).

Egyptian alfalfa weevil is a pest on medics. Some of the newer cultivars show improved resistance. Here are ratings from Weitkamp and Graves (1988): Good tolerance - 'Sephi;' Fair tolerance - 'Jemalong,' 'Ghor,' 'Ascot,' 'Paraggio;' Poor tolerance - 'Hannaford,' 'Cyprus,' 'Cyfield,' 'Borung,' 'Akbar.'

'Sephi' has high levels of resistance to both the spotted alfalfa aphid and blue green aphid but is susceptible to pea aphid. Its resistance to blue green aphids is equal to or greater than that of any other cultivar of barrel medic in field and green tests (Mackay and Barnard, 1981).

'Paraggio' shows good field tolerance of the spotted alfalfa aphid beyond the seedling stage, is tolerant to very tolerant to blue green aphid, but is susceptible to pea aphid (Mackay and Barnard, 1981).

Whitehead (1992) stated that in a pot study, burr medic and several other annual Medicago spp. (e.g. barrel medic) showed good resistance to the lucerne (alfalfa) race of stem nematode (Ditylenchus dipsaci). Subterranean clover was deemed very resistant, rose clover resistant, and berseem susceptible.

Weed dry above-ground biomass (chickweed, shepherd's purse, rattail fescue, and annual ryegrass) in plots seeded to 'Hannaford' was 1.0+/-0.5 Mg/ha, Mean +/- S.E.M. in an organic vineyard at Hopland, Mendocino County, California. Vegetational cover by the medic was 95.0+/-2.0 % based on visual inspection in early May (Bugg et al., 1996).

Rabbits regularly graze barrel medic on rangeland and can deplete young stands when forage is short.