Trifolium semipilosum Fres.

Leguminosae

Synonyms

T. johnstonii auct., non Oliver. Common name. Kenya white clover.

A perennial legume with a strong taproot and prostrate, pilose stems, often rooting at the nodes. Stipules whitish, the falcate-triangular tips usually longer than the base. Petiole pilose, much longer than a leaflet, except sometimes in stunted plants. Leaflets glabrous above, pilose at the margins and on the midrib beneath and also (except sometimes in var. glabrescens) on the undersides of the lower (outer) half of the two lateral leaflets. Inflorescence more or less globose, 10- to 25-flowered, about 2 cm across. Peduncle longer than the leaves, pilose. Pedicels pilose, reflexed in fruit, the outer up to 2 mm long, the inner up to 5 mm. Corolla white or pale pink. Standard 8 to 9 mm long. Pods 5 to 6 x 2.6 mm. Two to six seeds, dull yellow or light brown, sometimes mottled, irregularly discoid, about 1.5 mm across.
There are two varieties. Var. semipilosum Gillett, which now includes var. microphyllum Choiv. and var. kilimanjaricum Baker; and var. glabrescens Gillett (syn. T. johnstonii sensu Edwards, non Oliver and T. repens sensu Baker, non L.) (Gillett, Polhill and Verdcourt, 1971).

Var. semipilosum occurs in Yemen, Ethiopia, Kenya and Tanzania, in upland grasslands, especially near the drier types of upland evergreen forests at 1 400 to 3 000 m elevation, usually in places where there is much mist and annual rainfall in the range of 550 to 1 400 mm.
Var. glabrescens occurs in southern Ethiopia, Uganda, Kenya, Tanzania and in Malawi, where it is perhaps not native. It occurs in rather moister habitats than var. semipilosum and is more variable. Sites are upland grasslands, often abundantly associated with Pennisetum clandestinum at 1 500 to 2 250 m elevation, occasionally 1 200 to 2 700 m, with an annual rainfall of 900 to 1 200 mm (Gillett, Polhill and Verdcourt, 1971).

T. semipilosum has a long growing season. It is somewhat less tolerant of frost than T. repens cultivars but shows more vigorous summer growth. The main growing season is spring and autumn, with better summer than winter growth.

It is cut by heavy frosts, but resumes slow growth as soon as frosts cease.

Cv. Safari has grown from sea level to 700 m elevation in Australia.

In Australia, cv. Safari has been useful in areas with between 800 and 1 600 mm mean annual rainfall.

Lines of T. semipilosum grown in various areas of Australia have all shown greater drought tolerance than control lines of T. repens.

Cv. Safari is regarded as less tolerant of waterlogging than T. repens, but in laboratory flooding studies by Whiteman et al. (1984) it was placed in the second of four groups together with Lotononis bainesii and Desmodium heterophyllum, all of which developed medium to large adventitious roots under simulated flooding.

T. semipilosum grows in soils of pH 5.0 to 7.7. It is also more tolerant of the aluminium ion than T. repens or Medicago spp.

One of the disappointments with cv. Safari to date in Australia has been its slow to non-existent rate of spread from planted areas. This is possibly due to the lack of spread of the specific Rhizobium.

Seed is small and expensive and seedlings often grow slowly owing to rugose leaf curl. As a result, a well prepared, fine, firm, weed-free seed bed is necessary.

Can be sown with conventional seed drills and combines, especially if fitted with a small seed box. Rolling after sowing is desirable.

Sown on or near the surface and covered with trailing harrows, then rolled.

In southern Queensland, Australia, sowing is generally in autumn, as rainfall then is more reliable. Further north, sowing immediately after the start of the wet season is recommended. Recommended rates are 2 to 3 kg./ha, but because of the high cost of seed, lesser rates are sometimes used in the hope the stand will thicken with age.

Cv. Safari ranges from 700 000 to 1 000 000.

Higher than for T. repens.

Normal mechanical harvesting and processing techniques appear to soften enough seed so that no special treatment is required. Hand-harvested samples may require scarification.

T. semipilosum has a high nutrient requirement; in south-eastern Queensland, up to 500 kg./ha Mo superphosphate is recommended at planting. For the next two years, 250 kg./ha of superphosphate a year is recommended, and subsequently this amount every second year.

As the stolons can scramble up through tall-growing companions and, unlike T. repens, are not confined to the soil surface, T. semipilosum combines better with the taller tropical pasture plants, and is more tolerant of lax pasture management for its maintenance in mixtures.

Appears tolerant of 2, 4-DB at normal rates and of dalapon at 5 kg./ha.

Healthy seedlings are quite vigorous, but once infected with rugose leaf curl, vigour falls drastically. Survival depends on freedom from weeds and favourable growing conditions.

Maximum growth rates are achieved in late spring and from late summer through autumn.

T. semipilosum withstands heavy grazing well, forming a dense, prostrate, short sward.

While able to climb to some extent, it still performs better if growth of the taller species is controlled. Heavy summer grazing for this purpose is therefore recommended. This ensures that the stolons stay close to the ground and gives rise to more adventitious roots from the nodes. These replace old crowns, which die after about one year.

Burning in spring appears to do little or no harm and can in fact soften hard seed and improve seedling regeneration.

Cv. Safari is cross-pollinating and self-sterile but does not cross with T. repens. Chromosome number 2n = 16.

Third-year dry-matter yields of 8 500 kg./ha have been recorded in the Bundaberg-Maryborough District of south-eastern Queensland in wallum soils (Evans, 1967).

There is no reason to expect that T. semipilosum will not make hay or silage as readily as T. repens.

Because of its long growing season and greater drought tolerance, T. semipilosum provides feed longer into difficult periods than T. repens. It does not, however, stand into frosty periods as well.

In vitro organic matter digestibility is in the order of 71 to 75 percent and crude protein around 25 percent, levels similar to those of T. repens. Sodium content can be as low as 0.05 percent.

There is no evidence of oestrogenic activity with T. semipilosum, but bloat can occur in cattle. However, the risks may be less than with T. repens.

Harvesting methods vary from collection of material with a forage harvester for thrashing through a stationary header, to prior windrowing and pick-up thrashing with the header, to direct heading of the standing crop. The seed heads of the main crop are carried well above the ground but those of succeeding crops are much closer to the ground. The machinery available often determines the harvesting technique. Harvested seed needs drying before final cleaning.

Yields of up to 400 kg./ha have been recorded from small areas, but commercial yields rarely exceed 300 kg./ha and are usually much lower than this. Two harvests per year are possible under some circumstances.

Cv. Safari was released in 1973 by the Queensland Herbage Plant Liaison Committee. This derives from CPI 27218. received by CSIRO in 1960 from the Kitale Seed Co., Kenya. It is a representative of var. glabrescens Gillett.
At one stage, cv. Kabete 4, a mixture of four clones selected for vigour and persistence (Bogdan, 1965), was available in Kenya, but it is no longer believed to be available.

The most serious problem is rugose leaf curl, which delays establishment of new stands. Plants that survive this phase show subsequent immunity to further infection. At times, slugs can be a problem, especially after prolonged wet weather, while occasionally Amnemus sp. weevils and root knot nematodes (Meloidogyne sp.) attack the roots. Unlike T. repens, T. semipilosum, is not attacked by clover rust or pepper spot.

Essentially a tropical white clover, T. semipilosum exhibits the same main attributes as T. repens and in addition can thrive in hotter and drier districts. It better tolerates tall growth of associated species, while retaining T. repens' tolerance of heavy grazing.

The main deficiency of T. semipilosum is the slow and unreliable early growth of new stands due to rugose leaf curl syndrome. It is still only essentially a subtropical and high altitude, mild-climate tropical species, not adapted to hot, humid or lowland tropics.

Requires specific Rhizobium; CB 782 is used on cv. Safari in Australia.

• The true clovers: Exploration, preservation, evaluation and enhancement
• Clovers: Cultural specification and management of several species
• Insect pollination of clover species: Chapter 3 of the Virtual Beekeeping Book
• Sorting Trifolium names: Database of synonymes and common names
• Cover crops: Rich information with links to species, references and photographs

Gillett, Polhill and Verdcourt (1971); Shaw and Quinlan (1976); Jones and Cook (1981).

T. semipilosum is not as readily overtopped by taller weeds as T. repens but still needs careful handling.

Not particularly suitable for this method of establishment at this stage.

The most recent standards in Queensland are minimum germination 60 percent, which can include the hard seed component; minimum pure seed 96.5 percent; and maximum other seeds, 2.5 percent.