Tuesday, July 5, 2022

Study supports gibberellic acid use

A recent study has found using the plant hormone gibberellic acid as an alternative or complement to nitrogen fertiliser in late winter and early spring can significantly improve pasture growth. The study compared gibberellic acid and nitrogen and found drymatter could be increased by 300 – 400kg/ha by one application of gibberellic acid at the start of August.

Gibberellic acid naturally occurs in plants to activate and control growth, increasing in concentration as days get longer. While exact numbers are not known, it’s not widely used by New Zealand dairy farmers because, till now, there has been very little research and information about how to manage pastures that have had gibberellic acid applied.

Dr Racheal Bryant from Lincoln University, who was involved in the study, said gibberellic acid works differently to nitrogen by increasing the size of each grass plant (tiller) rather than increasing the number of grass plants.

“Whereas nitrogen will increase the density of tillers in the pasture, gibberellic acid makes each tiller bigger by elongating the leaf and stem. Applying either nitrogen or gibberellic acid can increase the amount of pasture in spring but when gibberellic acid and nitrogen are applied together you get the benefits of both increased tiller size and tiller numbers, which equates to more grass.”

However, Bryant said there were also downsides to gibberellic acid such as reduced grass growth after grazing because of more leaf area being removed during grazing.

“Until this study there wasn’t a solution to this particular problem. Now we know the best way to manage this con is by applying nitrogen before or with the gibberellic acid and allowing the grass to sufficiently regrow before being grazed again.”

The findings of the study will be shared with Southland’s dairy farmers at the DairyNZ Farmers’ Forum in Invercargill.

Registration is essential and free to levy-paying farmers and their staff – there is a $50 charge for all others. The Farmers Forum is on May 15 at the Ascot Park Hotel in Invercargill and runs 9.30am-2pm. Lunch is provided.

Farmers can view the Southland forum programme and register to attend online at www.dairynz.co.nz/farmersforum.

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