R.M. Jones

CSIRO, Division of Tropical Crops and Pastures, Cunningham Laboratory, Cnr. Carmody Rd. and Chancellors' Place, St. Lucia, Qld. 4067.

Abstract

Freshly harvested seed of Siratro (Macroptilium atropurpureum) was hand broadcast into, short subtropical pastures (< 10 cm high) in south-east Queensland. The fate of these seeds was determined as part of a population study on Siratro.
Emerging seedlings were counted regularly and removed. Twenty-one per cent of viable seed oversown in 1973 was recovered as seedlings, and a further 15% as seed in the soil seed bank after 6 years. Sixty-one per cent of this soil seed was recovered in the top 2.5 cm of soil, 32% from 2.5–5.0 cm and 7% below 5.0 cm. Nine per cent of seed oversown in 1974 was recovered as seedlings. Recovery of seed was greatest from seed lots with a higher percentage of hard seed. The persistence of Siratro seed in soil for several years confirmed the results from other demographic studies with Siratro.
There was very little predation of seed after oversowing hard seed into short (1–6 cm high pastures). During the cooler months 70% of the hard seed broadcast into these pastures was still hard four weeks after oversowing, but in the warmer months only 17% was still hard.