HEADING INTO spring, it is crucial that we maximise pasture growth to ensure that we are able to produce and conserve as much high-quality forage as possible.
Setting paddock rotations to maximise pasture quality
Through most of winter, pasture quantity was far more limiting on most farms than quality.
Normally, in early spring, as pasture growth and leaf appearance rates increase, our focus needs to shift to managing for quality.
Paddock rotation length generally needs to be shortened to help maintain grazing pressure and ensure high quality pasture is available by reducing the rotation length.
Whether soils are drier than average or still moist, pastures will be in a much better position to give greater yield responses if they have not been over-grazed.
Try and maintain a rotation based on leaf stage; the focus should be on grazing at the 2 to 2.5 leaf stage and leaving 4 cm to 6 cm residual pasture after grazing. This will ensure that pasture quality is maintained and shading at the base of the sward is minimised.
Locking up paddocks — how many and which ones?
As spring progresses, it is important to only drop paddocks out of the rotation for conservation that are surplus to the herd’s requirements.
In most years on a majority of farms, pasture growth will generally exceed herd requirements in early to mid-September.
This year, however, depending on climatic conditions and management — for example, if your pasture has been continually over-grazed (that is, grazed before the two-leaf stage and the grazing residual is below 4 cm) or if pastures have been moisture stressed or too wet — the spring surplus will be unpredicatable and will likely have reduced yields.
A simple strategy to determine how many paddocks to lock up is to graze paddocks in the same order each rotation, and if the next paddock is beyond the ideal leaf stage, skip it and drop it out of the rotation until it is ready to be cut for silage or hay.
If pasture growth slows and you need more grazing area, use the ‘dropped out’ paddock with the least mature pasture (or, alternatively, increase the rate of supplements fed per day).
Other things to consider when deciding which paddocks to lock up include:
How easy will it be to get machinery into and onto this paddock if it rains heavily?
Pasture composition — is it a rye-grass or rye-grass/clover mix with minimal weeds?
Is the paddock to be used for a follow-up summer crop and when does it need to be sown in relation to soil temperature, soil moisture and trafficability?
Is the paddock close to sources of water for irrigation?
Are potassium levels in soil excessive? Silage from these paddocks may be undesirable for feeding to transition cows.
• Maintain pasture quality by grazing at the 2 to 2.5 leaf stage.
• Keep post-grazing pasture residuals at 4 cm to 6 cm.
• Lock up the true surplus for conservation and cut at canopy closure to ensure quality.
• Consider using nitrogen (N) fertiliser at rates between 20 and 60 kg N/ha to improve pasture growth rates.
• This is an excerpt from a Dairy Australia article called ‘Making the most of spring feed’. Go to the Dairy Australia website for more information.