Subterranean Sub clover (ssp. subterraneum) plant
Scientific name
Subterranean Sub clover (ssp. subterraneum) plant
Trifolium subterraneum ssp. subterraneum
Strengths
- Tolerant of heavy grazing under set stocking.
- Vigorous seedlings provide good winter feed.
- Very persistent in medium to high rainfall areas and other areas with infrequent cropping.
Limitations
- Poor persistence on deep sands.
- Insufficient hardseededness for reliable persistence in tight cropping rotations (1 year crop:1 year pasture).
- Susceptible to germination following ‘false breaks’.
- Shallow-rooted, so unable to capture deeper soil moisture and susceptible to premature death in dry springs.
- Some older cultivars have high oestrogen levels contributing to ewe infertility.
Subterranean Sub clover (ssp. subterraneum)
Plant description
Subterranean Sub clover (ssp. subterraneum)
A prostrate self-regenerating annual pasture legume tolerant of heavy grazing that grows from autumn through to spring and buries its burrs.
Pasture type and use
Suited to permanent and semi-permanent pastures and to crop rotations (with at least 2 years between crops). The subspecies subterraneum is best suited to well drained acid soils, with the other subspecies, yanninicum and brachycalycinum, being suited to waterlogged acid and cracking neutral-alkaline soils, respectively
Where it grows
Rainfall
Adapted to winter-dominant rainfall area of southern Australia with annual rainfall 275 -1200 mm. Early flowering varieties suited to lower rainfall zone, later flowering varieties suited to higher rainfall zone. Can also be grown under irrigation.
Soils
Prefers well-drained sandy loams to clay loams of moderate acidity (pHCaCl 4.5-6.5).
Temperature
Widely adapted to the agricultural areas of Western Australia, South Australia, Victoria, Tasmania, New South Wales and parts of south-east Queensland with sufficient winter rainfall. Good frost tolerance.
Establishment
Field of Subterranean Sub clover (ssp. subterraneum)
Companion species
A range of perennial and annual grasses, lucerne, yellow and French serradella, biserrula, rose clover, arrowleaf clover, purple clover and burr medics, depending on soil type. On paddocks with patches prone to waterlogging it can also be sown with balansa clover, gland clover, Persian clover and subterranean clover ssp. yanninicum.
Sowing/planting rates as single species
5-15 kg/ha.
Sowing/planting rates in mixtures
3-8 kg/ha, depending on the number of mixture components.
Sowing time
Sow April-June, into moist soil following good weed control. Shallow sowing (<40 mm) is essential.
Inoculation
Commercial Group C (subterranean clover). Granular clay inoculants can also be used. Subterranean clover fixes about 25 kg of N per tonne of herbage dry matter. As a result it can increase soil nitrogen by about 125-200 kg of N/ha/yr.
Fertiliser
Phosphorus (with potassium on deficient soils) at sowing – levels dependent on soil tests. Trace elements (Cu, Mo, Zn) may be required on very infertile soils.
Management
Maintenance fertliser
Annual applications of superphosphate (with potassium or sulphur on deficient soils) are required to achieve maximum productivity. Levels are dependent on soil tests.
Grazing/cutting
Thrives under set stocking and can be grazed moderately hard while flowering. Likely to be shaded out by more erect plants under lax grazing. Can be cut for hay.
Subterranean Sub clover (ssp. subterraneum) burr
Seed production
Requires vacuum harvesting. Seed yields of up to 1000 kg/ha can be achieved under ideal conditions. Burr burial protects the seed from being eaten by grazing animals.
Ability to spread
Slow spread from site of sowing. Can spread by burrs attaching to wool.
Weed potential
Its slow rate of spread, its preference for moderate-high fertility soils and specific rhizobia requirement gives it low potential as an environmental weed. It is readily controlled by a range of broadleaf herbicides within crop.
Major pests
Redlegged earth mite is a major pest, particularly at plant establishment, where it can kill emerging seedlings, but also causes damage in spring. Timerite® has proved an effective means of control. Lucerne flea and blue green aphids can also cause damage in spring. Refer to chemical labels for suitability and recommended rates for insecticides.
Major diseases
Some cultivars are susceptible to the foliar disease clover scorch (Kabatiella caulivora), found in high rainfall, humid areas. Other foliar diseases in higher rainfall areas include leaf rust (Uromyces trifolii-repentis), powdery mildew (Erysiphe polygonii) and cercospora leafspot (Cercospora zebrina). Several root rots can attack subterranean clover, causing most damage to emerging seedlings and young plants. They include Phytophthora clandestina, Fusarium avanaceum, Pythium irregulare and Rhizoctonia solanii.
Herbicide susceptibility
Refer to chemical labels for suitability and recommended rates for herbicides registered for use on subterranean clover.
Animal production
Sheep grazing on Subterranean Sub clover (ssp. subterraneum)
Feeding value
Excellent as green feed with in vitro digestibility in the order of 70% and crude protein over 20% until mid-flowering. Quality reduces once plants hay off. Dry herbage feeding value over summer is less than maintenance value (often < 50% in vitro digestibility) although animals may be able to obtain sufficient energy and protein by digging up seed burrs.
Palatability
Readily consumed by livestock, either as green or dry feed.
Production potential
Vigorous seedlings provide good early season production. Later flowering varieties are capable of more than 10 t/ha annual production in long-season environments or under irrigation. Herbage production of 4-6 tonnes/ha is achievable in low to medium rainfall environments.
Livestock disorders/toxicity
Some older varieties of subterranean clover contain high levels of phyto-oestrogens, which can affect the sheep reproductive system. The most active isoflavone is formononetin, which can cause a decline in ewe fertility. Two other isoflavones, genistein and biochanin A, are also present in all subterranean clover varieties, but these have less impact. If ewes are mated when they are grazing green, potent subterranean clover their reproductive performance can be temporarily impaired. Continued exposure over several years to high levels of formononetin can lead to permanent infertility. Ram fertility is not affected.
Formononetin is present in subterranean clover only while the pasture is green. However, hay produced from oestrogenic varieties can be almost as potent as green pastures. Formononetin levels drop away during late flowering. Generally, dry subterranean clover pastures that result from normal haying-off are not oestrogenic. However, if there is a very early finish to the season, it is possible for oestrogenic varieties to retain some potency in the dry state. All recently released varieties have low formononetin levels. There have been isolated reports of cattle bloat on very clover-dominant subterranean clover pastures.
Cultivars
Denotes that this variety is protected by Plant Breeder’s Rights Australia
Author and date
Phil Nichols (DAFWA) and Brian Dear (NSW DPI)
July 2007
