Unlike fertilisers, which provide plants with nutrition, the role of biostimulants is to stimulate the plant’s metabolism, improving its ability to use nutrition to tolerate stressors.
But a deeper understanding of biostimulant products is needed in order to utilise their efficacy, says Don Pendergrast, head of technical services for UPL UK & Ireland.
The biggest risk for growers in terms of biostimulant use is selecting the wrong product for the situation they are facing, suggests Mr Pendergrast.
He says: “Growers must look at it [the biostimulant] likes it’s a chemical, what’s in it, and what it’s intended to do.
“This could be improving rooting, quality, or photosynthetic material, but there’s no point in thinking ‘my crop looks poor, so I’ll add a biostimulant’.”
With a reputation for working only on sickly crops, historically it was thought a response to biostimulants would only be seen where conditions were less than perfect, says Mr Pendergrast.
“Contrary to this belief, options like oligosaccharides [concentrated complex sugars extracted from seaweed] tend to work better on soils where there is moisture and nutrition available,” he says.
“It’s not a case of applying a biostimulant in a poor scenario will benefit you, but give you nothing in a good scenario.
“Think of it like fungicides. There are scenarios where you apply a whole fungicide programme, but environmental situations will be less or more favourable to fungal infection.”
While oligosaccharides help the plant to manage stress, their key role is to help it establish a good rooting system and good access to nutrition within the soil.
The value from amino acids in cereals tends to come later and they are more aligned with fungicide timing applications, from early spring through to T3, says Mr Pendergrast.
“Amino acids have also shown benefits in helping early establishment of OSR going into winter,” he says.
“In trials, we saw increased leaf development, and reduced grazing from cabbage stem flea beetle.
“This was significant in all scenarios with and without starter fertiliser, early and late drilled.”
Dr Syed Shah, agronomist and researcher at NIAB, has seen variable responses from products across a number of biostimulant trials, and says the greatest challenge for growers is the lack of quality parameters for product registration, meaning some products can lack consistency, or active ingredients can vary.
He says: “The main problem we have is the quality of biostimulants.
“Companies are producing these products, but how do you ensure what they’re claiming is in there? In fungicides you know the exact amount of each active ingredient and it’s very easy to verify.
“But for biostimulants they will say there are 14 amino acids, but there’s no quality check to ensure this.”
Dr Shah believes the lack of consistency could be responsible for the mixed responses he has seen in his own trials and studies.
“The quality is sometimes questionable, and 90% of the time you don’t see any significant statistical results across a product, because there is such huge variation,” he says.
In a bid to harmonise definitions and quality standards of biostimulants, from July 2022, biostimulants will fall under the same regulatory framework as all other types of fertilising material.
Changes to the European Union’s Fertilising Products Regulation mean manufacturers will need to prove a product has the effects that are claimed on the label if they want to place their products on the single market.
“The new rules mean if a manufacturer is claiming a product improves nutrient use efficiency for example, they will have to produce data from field or glasshouse conditions to support that claim,” Dr Shah says.
Oligosaccharides work by using a hormonal effect to increase reductases in the plant’s root system which increases its ability to access nutrition and to move water through the plant.
“Where it has turned drier later on in the season, there’s been more benefit from having that good rooting system on soils that have some moisture retaining capacity, whereas on light soil I don’t think you’ll get a vast benefit,” Mr Pendergrast says.
“The models done suggest this doubles the plant’s ability to uptake and utilise nutrients, resulting in one to two more winter tillers per plant in cereal crops.”
In lab trials, this has shown a 50% increase in the physical growth of the root in the root zone, which translates to more like 15-20% in the field, he adds.
Like any crop input, application timing is vital, and using biostimulant products as a ‘top-up tonic’ is unlikely to reap any obvious benefits, he says.
“It’s more likely to be beneficial in an organised or programmed way, and not ‘chuck it on once and expect it to work’.”
To boost early growth in the root zone and early establishment going into winter, for cereal crops Mr Pendergrast advises oligosaccharides work best applied at post-
emergence, from leaf 2 onwards.
“That will hopefully increase tillering potential. They can also be used coming out of the winter very early though, no later than GS30, to stimulate the initial boost,” he says.
In spring cereals, a single application at 2-3 leaves can boost early growth and increase tillering, he adds.
Amino acid products have a different mode of action, presenting the plant with a pre-formed set of core amino acids which it can use to produce proteins, allowing it to ‘skip’ a step in amino acid production.
Compared to oligosaccharides, which focus on root growth, amino acids have the potential to boost foliar growth and increase photosynthetic potential.
However, while biostimulant products may be effective, it is also important to consider whether they are likely to deliver sufficient yield or quality improvements to be cost-effective, cautions Dr Shah.
Biostimulants do have a place, such as in potatoes and sugar beet where improved rooting translates to increased crop yield, says Dr Shah, but there needs to be more robust data to support such claims.
“There is so much information, but it is often not scientifically proven,” he adds.
“In my replicated tramline trials, Terra-Sorb and Bridgeway are showing some benefits, and trends for higher yields, but the data is not yet good enough to be considered robust.
“More replicated trials work is required.”