Trifolium nigrescens Viv.
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Trifolium nigrescens Viv.
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Leguminoseae Common names Ball clover, small white clover. |
Author:
Dr. John Frame
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Annual, prostrate to erect growing with a crown rosette of stems, 0.75-1.0 m; glabrous, ovate leaflets; membranous, pointed stipules. Inflorescences white or pinkish. Seed small, yellow to dark brown and oval-shaped with 1-4 seeds per pod, constricted between seeds. Pollination by bees. Self-incompatible. Distribution Native to eastern Mediterranean where grown as winter annual. Grown in moist winter areas of south-east USA for cool-season growth. Characteristics Adapted to winter-wet, summer-dry, sandy loam and clay soils (Hoveland and Evers, l995). Good growth on well-drained soils. Produces seed even under severe grazing; seed germinate well in autumn-winter period of cool temperatures. Grows well into spring and seeds then. Not tolerant of shade. Season of growth Late autumn to spring (spring growth continues later than crimson clover). Frost tolerance Not a winterhardy species. Found up to 1500 (rarely 2000) m a.s.l. in Italy. Drought tolerance Moderate. Tolerance of flooding Moderate to good. Under different periods of prolonged flooding after establishment the yield reduction of ball clover was less than 40% compared with 46, 48, 52 and 64% for white, berseem, crimson and arrowleaf clovers, respectively (Hoveland and Mikkelson, 1965). Soil requirements Target soil pH of 6.0 to 6.9 (PLANTS database, 2000) though it is found on soils with a pH range of 6.0 to 10.0 (R. Snowball, pers. comm.). Responds to good soil fertility. Ability to seed naturally Good because of high proportion of hard seed produced. Seeds have a high level survival following ingestion and excretion by grazing animals on account of the small seed size. Sowing depth and soil cover A shallow sowing depth, 8-12 mm, is optimal with a light but firm soil cover. Sowing time and seed rate Autumn-sown at 3 kg/ha but at 1-2 kg/ha when surface seeded onto warm-season grass swards such as bahia grass. Number of seeds per kg 2 200 000 to 3 600 000 (but up to 5 000 000 in wild populatons). Percentage hard seed Can be over 90% of the seed produced. In Australia 70-90% of seed at harvest; seed softening data show that between 20 and 90% of seed remains hard after exposure to field conditions for the first six months (R. Snowball, pers.comm.) Seedling vigour Poor to moderate. Breeding system Chromosome number 2n = 2x = 16 and 2n = 2x = 32. Self-incompatible. Its high level of heterozygosis enhances plasticity and adaptation to different environments. Dry matter yields 1-2.5 t/ha (Knight, l985b). Acceptability Highly acceptable forage for grazing. Feeding value Protein-rich. Seed yields 100 to over 300 kg/ha (Hoveland and Evers, l995). Good seed retention allows efficient seed production. Ecotypes There are a number of local ecotypes from which common seed is produced but there are no cultivars. Pests Seedlings in oversown grass swards may be attacked by the striped field cricket (Nemobius fasciatus). Seed yields can be adversely affected by plant attacks from the clover head weevil (Hypera meles). Main attributes Adapted to wide range of soil pH. Fairly good waterlogging tolerance. Tolerant of hard grazing. Highly acceptable, succulent forage for grazing. Efficient seed producer. High proportion of hard seed produced conferring good self-reseeding characteristics. Very small seeds allow high levels of survival when passing through the gut of grazing animals. Main shortcomings Low forage yield. Risk of bloat (though low). Only ecotypes are available. Links
Main reference Plants Database 2000; Hoveland C.S. and Evers G.W. (l995); Knight W.E. (l985b) . Other references |