Summer Pasture Management

December 5 2019

Adjusting rotation length now will set your farm up for a smoother run when the summer dry arrives, says DairyNZ’s Kieran McCahon.

Proactive and reactive management

How you manage pasture during summer can affect your farm’s annual pasture production and utilisation, which influences milk production and profitability.

That’s why it’s important to make decisions now (proactive management). By the time dry conditions start to affect pasture covers and you’ve identified a pending feed deficit, you’ll have few options for climbing out of a feed hole. Proactive decisions will determine your pasture supply before dry conditions hit, and can prevent or delay the onset of other, more expensive, management decisions (e.g. culls and supplementary feed).

However, it’s also important to think now about the reactive management decisions you’ll make if a feed deficit arrives later. Smart reactive decisions will limit the effect of a deficit on future pasture production and persistence.

Ryegrass leaf stage

Ryegrass tillers maintain only three live leaves, and about 40 to 50 percent of potential growth happens between the two- and three-leaf stages. So, time your grazing for between the 2.5-leaf to three-leaf stage to maximise growth and quality, while ensuring plants have replenished enough energy to regrow.

In dry conditions when soil moisture is limiting growth, ryegrass tillers require more time to grow three leaves. You’ll need to extend your rotation length (see below) to maximise growth and ensure energy reserves are restored before grazing.

What does good proactive management look like?

  1. Increase your rotation length toward 30 days before dry conditions arrive. It can be difficult to extend the grazing rotation during a feed deficit as both pasture allowance and pasture covers decline.
  2. Consider a tactical application of nitrogen (N) fertiliser (30kg N/ha) before soil moisture levels fall. This will:
    • provide a greater response than to N applied in dry conditions
    • increase pasture covers, making it easier to lengthen the rotation
    • promote ryegrass tillering, potentially improving persistence.
  3. Pregnancy test early and develop a list of planned culls.

What does good reactive management look like?

Good reactive decision-making builds on the proactive decisions you’ve made in late spring/early summer.

  1. Graze between the 2.5-leaf and three-leaf stage and set your rotation accordingly.
  2. Ensure your paddocks are grazed to the same grazing height achieved in the previous round (1500 to 1600kg DM/ha). Grazing below this height risks removing the tillers’ growing points, located near the base of the plant.
  3. Once target residuals have been met, and if supplementary feed is not being offered, consider standing cows off to limit over-grazing damage.

This article was originally published in Inside Dairy December 2019

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