Persistence and productivity of eight accessions of Desmanthus virgatus under a range of grazing pressures in subtropical Queensland

The persistence and productivity of 8 accessions of Desmanthus virgatus were compared under grazing at 5 levels of presentation yield in subtropical subcoastal Queensland from 1989 to 1996. Presentation yields ranged from approximately 0.5 to 5.0 t/ha as measured at the end of the growing season. Apart from the year of establishment, annual rainfalls were below the average figure of 712 mm. Cultivar Marc and a similar line, CPI 78382, were the most productive at all levels of presentation yield. These lines also maintained a higher plant density than the other lines, although their density fluctuated from year to year. Their persistence is attributed to their ability to set seed under grazing, even in dry years. The lines which flowered late, and required a longer period of favourable soil moisture to seed, set only a small amount of seed. Thus, their density declined steadily as seedling recruitment could not compensate for death of original plants. It is suggested that commercial pastures sown to Jaribu desmanthus, which is a mixture of early-, mid- and late-flowering cultivars, could gradually become dominated by the early-flowering cv. Marc under similar rainfall conditions.