18-8-23 Australian phalaris - gibb acid

Improving Winter Pasture Growth Rates

Is it worth improving the old established but semi dormant Australian Phalaris pasture or resow using a newer winter active variety of Phalaris? Is the aim of one trial at the SFS Rokewood Pasture Site.

The Winter active cultivars sown include: Holdfast GT, Confederate, Horizon and GT070 (an unnamed cultivar).

In late July, separate strips of urea and gibberellic acid were applied to see if they would boost the growth rate of the phalaris.

Research has shown in slow growing pastures response rates to Urea of 5:1 – 5kg dry matter (DM) of feed grown for every kilogram of nitrogen applied.

The trial received 87kg/ha, which we expect to produce an additional 435 kg DM/ha compared to nil  applied using the 5:1 response rate. It is important to note that stock need to be kept off the paddock for 21 days after application to avoid nitrate toxicity.

Gibberellic acid is a naturally occurring plant hormone that can help boost production during cold winter months, producing the best responses when daytime temperatures are at their coldest. When daytime temperatures are averaging above 15°C gibberellic acid application will not increase growth rates as the plants will have sufficient levels for growth. Growth stimulation is usually seen within seven days of application and ceases after 3-4 weeks.

Visually, the results speak for themselves, see images below.

The response to gibberellic acid strip saw nearly twice the amount of growth compared to the nil treatment across all phalaris varieties, including the original Australian phalaris. This will be measured quantitatively by mowing to record dry matter production, which will occur in late August, approximately 4 weeks after the applications.


1. Australian phalaris treated with Gibberellic Acid.

2. Australian phalaris untreated.

Source: J Wettenhall, SFS

18-8-23 Australian phalaris - gibb acid 18-8-23 Australian phalaris - untreated

By Jessie Wettenhall, Research & Extension

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