The potential for buffel grass renewal from seed in 16-year-old buffel grass-sirato pastures in south-east Queensland.
Seed production by Cenchrus ciliaris cv. Biloela and soil seed reserves were studied in two 16-year-old C. ciliaris/Macroptilium atropurpureum cv. Sirato pastures in sub-humid SE Queensland. Ripe fascicles were collected on 6 occasions from summer to late autumn, placed on the soil surface in nylon mesh envelopes and retrieved at intervals for germination and viability tests. Dormancy of caryopses within fascicles remained high until spring and germination on a per caryopsis basis did not exceed 15% until summer. Hull removal increased germination of younger seeds. There were indications of secondary dormancy during winter. High temp. broke dormancy: treatment for 4-12 weeks at 60°C of fascicles which had remained dormant on the soil surface for 51 weeks doubled percentage germination. As soil surface temp. rarely exceeded 50° this explained the protracted fascicle dormancy in the field. Soil reserves of C. ciliaris seeds were <60/m2 despite 490-2300 fascicles/m2. Large numbers of rotten seeds were found. The poor seedling renewal of C. ciliaris was associated with low seed production, high dormancy and soil surface temp. too low to break dormancy rapidly, hence increasing the chance of rotting and predation.