N.J. BRANDON and R.M. JONES

Tropical Agriculture, CSIRO, Brisbane, Queensland, Australia

Abstract

The rate and final % emergence of 7 tropical legume species were examined at a range of sowing depths from 0–5 cm in trays of clay soil in a germination cabinet set to day/night temperatures of 30/20°C. The species included are used or have potential for use in leys (Lablab purpureus cv. Highworth; Macroptilium atropurpureum cv. Siratro; Macroptilium bracteatum CPI 27404; and Macrotyloma daltonii CPI 60303) or permanent pastures (Desmanthus virgatus cvv. Marc, Bayamo and Uman; Indigofera schimperi CPI 52621 and CPI 73608; and Glycine latifolia cv. Capella). The ability of soft seed of Indigofera schimperi and Desmanthus virgatus to either emerge as seedlings or retain viability during brief periods (1–4 days) of watering was also examined.
The small-seeded Desmanthus virgatus and Indigofera schimperi successfully emerged only from depths of 2 cm or less. All the larger-seeded legumes emerged from the maximum depth of 5 cm.Indigofera schimperi was much slower to emerge than Desmanthus virgatus and usually required 4 days of good soil moisture to reach 50% emergence of viable seed compared with 1–2 days for Desmanthus virgatus. This resulted in greater emergence of Desmanthus virgatus than Indigofera schimperi given only 1–2 days watering. In some cases, soft ungerminated seed of Indigofera schimperi remained viable following brief wetting and drying of the soil, and germinated on a subsequent watering cycle. Possible implications of sowing depth and rate of emergence are discussed in relation to establishment in the field.