Biostimulants show potential for UK maize growers

Oxfordshire farmer Mark Viner has seen promising results from using biostimulants to support maize crops under challenging growing conditions.

Smokedown Farm, near Faringdon, moved from dairying into a large-scale calf-rearing system in 2005, finishing more than 800 head a year.

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Mark grows maize annually on 16-20ha as a core part of the forage system, providing a high-energy feed for finishing cattle.

Ensuring consistent yields and quality is, therefore, a priority, particularly in seasons where grass silage can be variable.

Establishment is often the most vulnerable stage, especially where drilling is delayed or soil conditions are less than ideal.

In 2025, late-drilled Pioneer P7179 maize sown in the second week of May at a rate of 111,000 seeds/ha, struggled to establish in poor seed-beds, with dry conditions limiting early growth.

Mark Viner © Lucy Baker

“The crop never really got going early on, seed-beds weren’t great and there just wasn’t the moisture there,” says Mark.

“It was showing a typical stress response; it had purple leaves and was clearly under stress, and it just wasn’t growing away as we would have liked.”

In response, he applied SeaActiv, a foliar biostimulant, at the eight-leaf stage, spraying it directly onto the crop using a conventional sprayer at a rate of 3 litres/ha.

The product, which contains trace elements designed to support plant function under stress, was applied to the worst parts of the field (about 8ha) to help the crop recover during this difficult establishment period.

“We decided to give it a go to try and help the crop through that stress period,” he says.

“Within a week, it had gone back to a healthy green and you could see the difference almost straight away.”

© Lucy Baker

Conditions remained dry for much of the growing season, with minimal rainfall from late February through to early September.

“From where it started, we were really pleased with it,” adds Mark. “It ended up at about 32.5t/ha freshweight, which in a year like that was a very good result – and it held on longer, so we weren’t harvesting until early October.”

Yields last year were widely reported to be much lower than normal, with some crops harvested early and producing as little as 12.5t/ha, so dropping from Smokedown’s usual average in the low 40s to 32.5t/ha wasn’t as bad as initially thought.

“The silage fed out well over winter too, so we were happy with what went in the clamp.”

Understanding the role of biostimulants

According to David Newton, technical product manager at Timac Agro, the role of biostimulants is less about boosting peak yield and more about supporting plants by reducing the impact of environmental stress.

Rather than acting as a direct fertiliser, they work by stimulating natural plant responses, such as root development, nutrient uptake and recovery from stress.

Timac’s seaweed-based foliar biostimulants, produced in Brittany, France, are designed to enhance root growth, improve nutrient absorption, and boost plant resistance to abiotic stresses like drought, temperature extremes and excess water.

At the same time, he suggests conventional fertiliser technologies have reached a plateau in terms of yield response.

“Recent geopolitical events have also highlighted the fragility of global trade. Farming operates in a global marketplace, both for inputs and outputs, which continues to place pressure on pricing.

“There is now a greater argument to include biostimulants in crop programmes,” he adds. “Climate change has been apparent for the past decade, with increasing inconsistency in rainfall, temperatures and seasonal patterns.

“If they’re so effective, people quite rightly ask why we don’t always see statistically significant responses in trials.

“But biostimulants don’t behave like conventional inputs; they tend to show their value in more challenging conditions.”

That can make them harder to assess using standard small-plot trials, where variability between plots can mask responses.

“You might see a clear difference in the field, but when that’s averaged across multiple plots, the effect can get diluted,” David explains. “That’s where some of the scepticism has come from in the UK.”

Instead, he suggests growers should view biostimulants as a tool to improve crop resilience.

With weather patterns becoming more unpredictable, and pressure on input costs continuing, he believes there is a growing case for their inclusion in crop programmes.

“It’s about reducing that growth check when a crop comes under stress and helping it recover more quickly,” he says.

“If you can shorten that period where the plant isn’t growing, that’s where the benefit comes from.

“Growers are already looking at how to get more from what they’re applying.”

If farmers can improve nutrient use efficiency and help the crop cope with stress, that’s where these products can start to justify their place, he adds.

However, David acknowledges that performance is not always consistent, particularly in more favourable seasons.

“In a good year, you may not see a big response,” he says. “But in a difficult one, that’s when they tend to show their value.”