DURING SUMMER in south-eastern Australia, with limited rainfall on rain-fed areas of the farm, leaf emergence rates slow, pasture growth rates decline and there is increased grazing pressure on any irrigated areas of the farm.
As a result, the average pasture cover of the farm tends to decrease.
The autumn break occurs when there is a significant rainfall event with follow-up rain that lead into winter.
Sometimes there are “false” autumn breaks when there is a significant rainfall event but no follow-up rain in the following weeks.
In a “false” autumn break, pasture will become green, but there is little growth and once soil moisture becomes limiting again, this growth will stop.
Once the true autumn break does occur, it provides the opportunity to build pasture covers across the grazing platform prior to cooler conditions and slower pasture growth during winter.
To get the greatest benefit from the autumn break consider: grazing management, nitrogen use, pasture renovation and grazing management.
There are three principles to follow to maximise pasture consumption and ensure good pasture quality.
1. Set grazing rotation based on leaf stage
For rye-grass-based pastures, this means grazing at the 2.5 to three-leaf stage or before canopy closure to maximise the amount of pasture grown. The difficulty of achieving this will depend on how the farm was managed during the dry period. If a leaf-stage based rotation was maintained on the rain-fed area of the farm despite there being only a small amount of growth, this should be continued.
If a fast-grazing rotation was used or rain-fed paddocks were not grazed during the dry period there would be a bulk of paddocks at a similar leaf stage. In both circumstances, there will need to be some compromise to establish the right rotation and achieve an orderly feed wedge.
2. Grazing duration
In slowing down the rotation, it is important to ensure an area isn’t grazed for longer than two to three days. If cows are grazing the one paddock for more than three days, they will start to eat the pasture regrowth, which will slow growth rates and reduce pasture yield. Use back fencing to avoid this.
Ensure if young stock or dry cows are following the milkers the grazing is completed within three days.
3. Ensure grazing residual targets are reached
Aim for a post-grazing residual height of four to 6 cm between the clumps, equivalent to 1400–1600 kg DM/ha to maintain quality.
Nitrogen use
Nitrogen fertiliser is generally a cost effective tool for increasing pasture growth and could be considered when extra feed is needed. Nitrogen is only effective on boosting the growth of pasture that is growing — it shouldn’t be applied to dormant pasture and where soil moisture is limiting. Nitrogen can be applied as soon as there is a significant rainfall event (>25 mm) and continue until soil temperature becomes too low. Temperate pasture (e.g. rye-grass) will generally respond to nitrogen when soil temperature is above 4°C. Sub-tropical pasture (e.g. kikuyu) will respond to nitrogen when soil temperature is above 10°C.
— Dairy Australia.