A recent Teagasc webinar focussed on the potential role of biostimulants within Irish crop production systems.

Dr. Pete Berry, from the UK’s Agricultural Development and Advisory Service (ADAS), defined biostimulants as products or microorganisms that will act to stimulate a range of natural processes.

He explained that, from a crop production point of view, they can improve: nutrient uptake; nutrient efficiency; tolerance to sources of physical stress; and crop quality.

Research has also indicated that biostimulants will act to improve crops’ inherent resistance against pests. They can also deliver improved antimicrobial activity within plants.

According to Berry, the end result will be a combination of improved crop growth and yield.

“But the main role of a biostimulants should not be as a fertiliser or pesticide,” he said.

According to Berry, biostimulants can be categorised as being either microbial or non-microbial in nature.

Microbial products include plant-growth-promoting bacteria; non-pathogenic fungi; arbuscular mycorrhizzal fungi; specific protozoa; and fungi.
Non-microbial products include: seaweed products; humic substances; chitin derivatives; free amino acids; specific trace elements; and complex organic materials.

“A lot of the information gathered on biostimulants has been secured from glasshouse experiments and field trials undertaken outside the UK,” he continued.

“Of the 11 products that we reviewed there was some evidence to the effect that nine of them could improve yield.

“Within the trial work looked at there was a strong focus on cereal crops, relative to oilseed rape.”

Berry pointed out that many of the biostimulants reviewed had a role against pests and diseases.

“But their mode of action is still very unclear,” he stressed.

“There was also a general lack of consistency under field conditions.”

Specifically, under UK conditions, seaweed extracts delivered a yield increase in one of the three trials carried out.  

Phosphite and other organic salts improved yields in four out of 15 trials while antitranspirants delivered a positive yield response in seven out of seven trials.

“But these latter results were only achieved under drought conditions,” Berry further explained.

“If water availability is improved, antitranspirants actually have a negative effect on yield.

“For the rest of the product types, we did not find any UK field evidence.”

Commenting specifically on the impact of phosphite on crops, Berry confirmed that it acted to reduce some diseases, for example  mildew, and nematodes.

“Phosphite should not be regarded as a fertiliser. It is a reduced form of phosphate which, in fact, will act to reduce crop growth rates if plant growth phosphate levels are reduced.”