When identifying lucerne cultivars for true grazing tolerance, ensure you choose cultivars that are evaluated here in Australia under the internationally recognised Standard Test Protocol for grazing tolerant lucerne.
Remember that there is lucerne that tolerates grazing and there is grazing tolerant lucerne.
Numerous studies recommend a minimum spell period of around 35 days with a short grazing period. These practices should provide a reasonable balance between persistence, quality, yield and animal safety. Nevertheless, many Australian producers find ideal grazing management techniques impracticable and will often graze stands continuously and overgraze paddocks.
There are a number of contributing factors for the low rate of adoption for ideal grazing rotations. Paddocks are often too large and there are high costs associated with subdividing and watering in broad acre pasture systems; additional management is required and the benefits of rotational grazing are not well understood or demonstrated clearly enough in Australian pasture systems.
However, perhaps the greatest obstacle to adoption is that over a very long dry summer, when the only green feed on the farm is lucerne, producers will often and understandably leave their valuable stock on the lucerne for extended periods despite the known consequences.
Continuous grazing or set stocking of a lucerne stand through hot and dry periods subjects the plants to a magnitude of stresses such as trampling, tugging, pulling, waste excrement and daily defoliation. These continual effects will most likely lead to a rapid decline in stand persistence.
There is a strong correlation between winter dormancy and grazing tolerance, but there are also other both morphological and physiological traits that contribute to differences in lucerne persistence under grazing.
Improved persistence also results from reduced weed invasion of the stands. Further benefits of grazing tolerance (GT) cultivars are portrayed in hay production through continually producing high yields and strong stand density, high quality in maintaining stem density, as well as improved traffic tolerance (another source of stress on the crowns of plants) through hay-making and silage processes.
Trials around Australia and other published literature have clearly shown that through maintaining stand density, improved persistence, quality and yield can be achieved in lucerne cultivars that have been selected for grazing tolerant characteristics.
In a 2012-2020 grazing tolerant lucerne trial at Leigh Creek, Victoria, showed Torrens GT8, a Stamina® grazing tolerant lucerne, had higher ground cover in years 2 and 3 compared to all dormancy 7-10 and some dormancy 6 varieties.
After all cultivars were trialled under the internationally recognised Standard Test Protocol for grazing tolerant lucerne, it was evident that:
Producers should be cautious of purchasing cultivars claiming grazing tolerance in the market, which have not been subjected to the standard test protocols under Australian conditions.
For true grazing tolerance ensure you choose cultivars that are evaluated under standard test protocol by Smith & Bouton in 1998.
NOTE: Refer to PGG Wrightson Seeds Lucerne Management Guide for full trial results inclusive of dormancy 3-5 varieties