Don’t be fooled by the green pick
Getting productive and persistent pastures is influenced by how we manage perennial grasses during a hot dry summer and then prepare them for the growing season.
Under-grazing leads to wastage of pasture and dead plant material will restrict new growth and reduce overall quality of herbage. Over-grazing maximises utilisation of pasture, but repeated over-grazing draws down a plant’s reserves and over time reduces its persistence.
There are four introduced temperate perennial grasses that are the backbone of pastures in Southern Australia. These are Phalaris, Perennial Rye Grass, Cocksfoot and Tall Fescue. Being perennial, the same plant can survive from one year to the next, providing stability in production compared to relying on annual germination. But to do this, it must get through the stressful period of summer.
A plant is more likely to survive a single but more than one stress at a time can present a risk to the plant’s ability to persist. The combined stresses of lack of moisture and grazing make summer a dangerous time for perennial grass survival. While sporadic out of season summer rainfall can seem a blessing, it can cause plants to break out of dormancy and cause new daughter shoots to emerge and they need to hang on until the autumn break. Ensuring their survival needs a couple factors to be considered.
- The full quota of live leaves per tiller is regrown (3 for perennial ryegrass and tall fescue, 4 for phalaris and cocksfoot) prior to re-grazing indicating that the plant carbohydrate reserves are sufficient and can recover post grazing.
- The plant cannot be pulled out by grazing stock; root mass can contract with a reduction in carbohydrate reserves during hot, dry summers. Also, annual reduction of roots in cocksfoot can make it at risk of being pulled out, especially in lighter texture soils.
The key strategies for grazing during summer is:
- Short high intensity grazing of summer pick (3 to 5 days followed by long rests) if three or four leaves have regrown – but be careful, there may not be enough moisture to allow the plant to re-grow new leaves and fully replenish fuel reserves leaving it vulnerable.
- Leave some residual feed, (2cm in height), that is don’t allow stock to graze into the white part of the tiller base where carbohydrate reserves are stored or into the plant crown where growing points are located.
- Pinch and pull plants prior to grazing to see if plants pull out.
- Graze to remove reproductive tillers and reduce excessive dry matter by late summer to encourage sub-clover germination at the autumn break.
- Maintain at least 70% groundcover on flat country and 90% on hill country to prevent soil erosion by summer thunderstorms or wind.
Coming soon to the Southern Farming Systems and MLA websites are the latest factsheets on the management of perennial grasses.
Phalaris with Daughter Tillers, Photo Credit: J Brogden, SFS