Gibberellins are naturally present hormones found in all plants, they help to increase cell size and numbers enabling greater photosynthesis, plant metabolism and in turn, increased growth in stems, leaves and roots. Gibberellins can provide a solution both for extra grazing at spring turnout as well as boosting first cut silage swards.
Spraying grass with gibberellins before the season warms up – in conditions between 5oC and 10oC when growth is limited, will encourage growth and in turn, enhance dry matter production.
Sprayed once using a conventional ground boom sprayer, either tractor or quad bike mounted for small paddocks, the gibberellin application has a three-week impact on the sward, after which its growth rate will return to normal.
Gibberellins are available from Nufarm branded Smartgrass.
Boosting first cut silage swards
Perry Beard is planning to reintroduce gibberellins this season to 30ha in an attempt to mitigate delayed first cut and introduce flexibility to grassland management at Manor Farm, Whitminster, Gloucester which supports a 120-cow autumn block calving herd.
“We are a relatively high input high output unit and believe in making the most from forage which currently amounts to 39% of the herd’s average 9,000 litres; this spring we’ll be resetting that figure to over 40%,” explains Perry.
Last season he carried out his own trial on a 10ha field split in two; gibberellins were applied in mid-April, 31 days prior to cutting, on half the field, whilst the remainder acted as a control. “We found gibberellins have a place for us; they helped out tremendously enabling us to achieve over 1t DM/ha extra first cut more than the control, a figure representing a 20% boost in yield together with significant cost benefits.” See Fig 1.
“Land is our biggest limitation – the unit is fenced by three major roads, consequently the gibberelins proved to be a bit like an insurance policy to bulk up first cut and achieve that extra 1t/ha made which all the difference – they’ve given me the flexibility to extend the grazing area and shut up less area for silage. Alternatively, if I’d chosen, I could have cut one week earlier.”
He adds: “Whilst we would like to introduce the gibberellins to give the early spring grazing a boost, we farm such heavy clay land that is not suited to early spring turn-out.”
Fig 1: Independent grassland consultant, Dr George Fisher discusses the costs benefits of that extra
1.036t DM/ha first cut
Assuming an 11.5 MJ ME/kg DM and a 70% utilisation rate of the silage, this gives Perry an extra 8,340 MJ ME/ha to work with.
Treating first cut silage swards with gibberellins in replicated trials last season resulted in an extra grass yield of between 500kg and 1.2t DM/ha, The trials which were carried out by Pearce Seeds/Nufarm, featured short, medium and long term cutting mixtures and individual grasses to determine the impact of the gibberellin. Regardless of mixture and grass type, the treated swards demonstrated a benefit. See table 1.
Table 1: Gibberellin impact on spring grass swards – extra DM and ROI*
average extra kg DM/ha/day
average extra kg DM/ha
21 day cumulative
Grass growth for
extra milk production
for reduced conc. use
|UK Pearce Seeds
Boosting spring grazing
In the UK, we recommend farmers apply SmartGrass to paddocks measuring 3cm to 5cm (1,500kg DM/ha). If the paddocks have been grazed, apply five days after removing the stock, and then reintroduce to graze 21 to 28 days after application.
If first cut has been taken exceptionally early – before 25 April, then an application can be made on the aftermaths three to five days later resulting in an extra yield benefit for either cutting or grazing purposes, again 21 to 28 days after application.
Nufarm agronomy manager, Brent Gibbon
New Zealand dairy farmers have been using gibberellins for over a decade to boost spring grazed grass – an integral part of low cost forage based spring block calving systems. So far, gibberellins have featured in 52 replicated trials resulting in an extra 30% to 60% pasture dry matter within a three-week period, compared with the control. See table 2.
The NZ trial findings were mirrored by UK livestock producers with 10 on-farm trials located throughout the country. Each farmer sprayed SmartGrass gibberellins to grazing swards in the early growing season to conclude that the treated swards achieved an additional average 22kg DM/ha/day over the control.
Last season, Pearce Seeds/Nufarm carried out replicated trials featuring short, medium and long term cutting mixtures and individual grasses to determine the impact of the gibberellin on first cut silage yields. Regardless of mixture and grass type, the treated swards resulted an extra 500kg to 1.2t DM/ha.
Table 2: Gibberellin impact on spring grass swards – extra DM and ROI *
Extra kg DM/ha/day
Extra kg DM/ha
Grass growth for
extra milk production
for reduced conc. use
|UK on farm||22||460||7:1||3:1|
|UK Pearce Seeds/
The findings from the three sets of trials concluded that introducing gibberellins to the spring regime can be cost effective. Take one single spring application resulting in an additional 500kg DM/ha (grazing), or 700kg DM/ha (silage) that yield can lead to an 8:1 ROI for turning the extra grass energy into milk yield, or a 3:1 ROI for using the extra grass energy to reduced concentrate fed. See table 3.
Table 3: Gibberellin ROI: return gained from producing extra DM/ha
|System||Additional DM Value||Farmer
|Grazing based dairy farmer replacing concentrate feed||0.5t DM at 12ME = 6,000MJ ME||80||0.41t of a 13MJ ME concentrate @£250/t = £102||3:1|
|Silage or grazing based dairy farmer increasing stocking rate||0.7t DM at 11.5 ME = 8,050MJ ME||75||1,120 litres/ha @ 29ppl = £324||8:1|
Boosting grazing in New Zealand
Boosting grass growth with gibberellins plus liquid nitrogen is a ‘no-brainer’ for Dan and Abbie Hinton who farm a 550-cow block calving herd at Eureko, Waikato. The couple are using the natural pasture growth promoter to produce as much seasonal milk as possible from the unit’s tetraploid Italian ryegrass swards instead of feeding more expensive supplements.
“The growth rates we are achieving are 30% higher than the untreated paddocks, so we’re getting more high quality grass on a faster round,” Dan explains. “After 26 to 30 days, Smartgrass treated paddocks actually look grazeable compared with the paddocks that haven’t been sprayed, which don’t.
“In fact ,the best way to evaluate the gibberellins’ potential is to spray half or a whole paddock. Once it’s been applied there is no secret, you just watch and the magic is in front of your eyes plain to see within days. If you can see it, it’s 300kg DM/ha. Also, once the treated pastures are grazed, they instantly send out a new tiller. However, timing is everything, so we use a contractor for the work and strictly follow the recommended application time of within five days post grazing.”
The Hintons say regardless of the payout, they need to feed their herd with the most economic feed available to minimise loss of body condition score between calving and mating.
“This is important because if we don’t achieve a good six-week in calf rate, the bad year will flow into subsequent years, with larger repercussions. In that context, we evaluate feed inputs not so much as to whether each is imported or home grown, but on the basis of cost and return, with the aim being to utilise each type of feed to its fullest before moving onto the next most expensive source.”
With no feed pad, their economic feed spectrum thus ranges from naturally grown grass to N boosted pasture to pasture treated with Smartgrass plus N, followed by harvested surplus, home grown crop if pasture renewal is required and finally bought-in feeds.
“Surplus spring New Zealand grass if managed properly is 1MJ ME/kg DM higher than some other feeds you can buy, at a fraction of the cost,” says Dan.