Lucerne survival in south-east Queensland in relation to grazing management systems

Abstract

Survival of lucerne plants and changes in the row cover of lucerne in relation to grazing management were studied in an experiment at Lawes, south-east Queensland, from 1971 to 1977. There were six grazed treatments (resting for 32 or 44 days combined with grazing for 4 or 16 days, resting for 56 days with grazing for 4 days, and resting for 40 days with grazing for 8 days) and three mown treatments (mown every 36,48 or 60 days). All grazing was with sheep, at a stocking rate equivalent to 20 ha-1 on a year round basis. The experiment was irrigated when necessary to ensure that moisture at least equivalent to the long-term average monthly rainfall was received. There were about 42 lucerne plants m-2 in November 1971 and about 13 plants m-2 in October 1977; thus lucerne survival was good in all treatments, with stands losing about five plants m-2 annum-1. Management effects were small, with survival and row cover becoming slightly better as the interval between grazings or mowings increased from 32 to 60 days. Grazing for four days gave poorer survival than either grazing for 8 or 16 days or mowing. Perennial grass cover was much greater with four-day grazing than in the other treatments. Inspection at the end of the experiment showed nearly all crowns to have moderate symptoms of crown rot caused by Colletotrichum trifolii. The need for critical attention to the interaction between moisture supply, grass invasion and disease accumulation in maintaining lucerne stands in sub-tropical environments is discussed.