Applying natural hormone to grass could lift yields 1.2t DM/ha

Applying a natural hormone to grass after fertiliser could help farmers boost yields by up to 1.2t DM/ha, trials have shown.

Pearce Seeds and chemical company Nufarm carried out trials at Plumber Farm near Sturminster Newton in Dorset to investigate the benefit of applying SmartGrass to pasture.

SmartGrass contains Gibberellic acid, a natural plant-growth hormone found in all plants and fungi. It helps to stimulate cell size within the leaves, enabling greater photosynthesis to improve grass growth.

See also: 7 tips to increase grass yield and quality

About the research

The product was applied on 25 April last season to five different grass mixtures and individual varieties. Results showed that application gave an additional 0.5-1.2t DM/ha regardless of variety when compared with swards that had received no product.

The mix that responded the best to the product was the Festulolium red clover mix, growing 1.2t/ha extra grass.

Independent grassland consultant George Fisher who oversaw the trial said this was potentially because the grass responded better to the clover, which is fixing nitrogen little and often.

He says it could be particularly useful this season for farmers that are running short of forage and need to give grassland a boost.

“It should work well this spring, filling the gap in the middle of March, beginning of April before grass growth equals cow demand.”

He estimates the return on investment is 3:1 for grassland farms that are able to substitute concentrate with grass (see costings below).


  • 0.5t DM of grass @12ME contains 6,000 MJ of ME (80% use = 4,800 MJ ME)
  • Grass replaces 0.41t of a 13% ME concentrate costing £245/t or £102/0.41t
  • £102/37 (cost of Gibberellins application per hectare) = 3:1

About the product

  • Gibberellic acid is a natural plant-growth hormone found in all plants and fungi. It helps to stimulate cell size within the leaves enabling greater photosynthesis to improve growth.
  • It is a dry product and needs to be dissolved in water before being applied to grass.
  • 20g of product covers one hectare.
  • It costs roughly £37/ha including application based on National Agriculture Association contractor charges of £16.75/ha.

Dos and don’ts when using the product

  • Do leave three weeks before grazing
  • Do apply after fertiliser – it can be applied straight after. Nitrogen is required to support plant growth
  • Do apply using a conventional ground boom sprayer, either tractor- or quad bike-mounted
  • Don’t apply the product three to five days post-grazing to allow the growing point to recover
  • Don’t cut grass for silage until 21 to 28 days after application
  • Do ensure grass is 3cm to 5cm or 1,500kg DM/ha pre-application

Product downsides

  • Not licensed for use on organic farms
  • Cannot be used after first cut or first grazing. Product cannot be used beyond 30 April due to current product-licensing terms
  • It has no effect on the growth of clover. Gibberellic acid is a growth promoter of grass, not clover.

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