Michele Jolliffe, Agriculture Victoria, Hamilton
Autumn is a key time to rebuild perennial ryegrass density and set up pasture production for the year. The dry summer will have weakened individual plants, and some will die despite good management.
By following a few simple tactics, it will be possible to maintain and, in most cases, improve your perennial ryegrass pasture performance into the future.
High density pastures produce more feed
Walk your paddocks before or shortly after the autumn break and identify pastures that have thinner plant density.
Generally, a good ryegrass pasture should have a perennial ryegrass component of 60% or higher, and a low weed content. A poor-quality pasture generally has a perennial ryegrass component of 30% or less and has many bare patches and weeds.
Restore the density by either direct drilling perennial ryegrass or carrying out a full renovation (spray, cultivate and re-sow). Full renovation generally gives a better result but can limit use of these paddocks over winter. It's a good idea to limit the amount of ground cultivated to help manage the risk of pugging or bogging.
Ensure existing plants are able to perform at their best
Begin autumn with a long grazing rotation. Two factors are involved – leaf stage and grazing intensity. Plants weakened by summer growing conditions will be further weakened by repeated hard grazing and will grow less feed in the long run.
South west Victorian research has shown that pastures which have been on a long grazing rotation over summer (45 days or longer) are able to be grazed one rotation earlier following the autumn break than pastures grazed more often.
Consider a sacrifice paddock or two
While pastures in a sacrifice paddock will be further weakened, those not grazed will be strengthened. Most pastures will grow faster compared to paddocks that are grazed before the ideal leaf stage is achieved. To limit any downside from using a sacrifice paddock, choose paddocks that are due for renovation.
Use supplements to optimise re-growth
The importance of pasture residual is often overlooked. Post grazing residuals are a good practical indicator of how well cows are being fed.
A residual after grazing of 4 to 6 centimetres will give highest ryegrass performance. When it is higher than 6 centimetres and uneven it indicates that cows are over fed and are starting to waste pasture. Below 4 centimetres shows cows are still hungry.
If cows graze shorter than 4 centimetres, the damage seen in pastures includes decreased ryegrass plant survival, an increased invasion of weed species, more tiller death and lower overall dry matter yield. Increasing or decreasing supplement feeding is a tool to manipulate grazing residuals when pasture availability is limited.
Control broadleaf weeds
Competition from other species will limit the performance of perennial ryegrass pasture. Strategic control of broadleaf weeds can be easily achieved through spray-grazing at about 6 weeks after germination. This is particularly important if capeweed is a known problem in your area.
