Crop biostimulant efficacy debated at Huggate Monitor Farm

The world of biostimulants is complex and fascinating. Philip Dolbear, an AHDB knowledge exchange manager, reports on a recent Monitor Farm discussion that looked at their role in the production of cereals and oilseeds.

Last month, I facilitated the AHDB Huggate Monitor Farm meeting in Yorkshire. It aimed to help people get the most out of biostimulants in cereals and oilseed rape. Over 40 farmers, from across the region, attended the event.

• Gary Shipley, Huggate monitor farmer
• Kate Storer, ADAS crop physiologist
• Angus Gowthorpe, a regenerative farmer from the Vale of York

Soaring fertiliser prices, increasing pressure to reduce synthetic inputs, tightening enforcement of regulation (including around the use of organic matter) and more frequent weather extremes, combine to make biostimulants an attractive prospect, for some. But do they do what some claim they do? That was the question from host AHDB monitor farmer, Gary Shipley.

While an official definition is still up for debate, biostimulants are generally agreed to be materials which contain substances – including microbes – that stimulate natural processes. They may enhance nutrient uptake, nutrient efficiency, and/or tolerance to environmental stress. However, the main role of a biostimulant should not be to provide fertilisation or pesticidal activity.

There’s a wide range of products in this category and this presents a challenge for researchers and growers. From the non-microbial seaweed extracts, humic substances, inorganic salts and protein hydrolysates, to the microbial plant growth promoting bacteria, non-pathogenic fungi and arbuscular mycorrhizal fungi, the modes of action and potential benefits vary significantly.

Isolating and assessing their effects within farming systems is some undertaking, yet it is essential – for both effective regulation and use. However, our 2016 research (Research Review 89) highlighted how little data we have for biostimulants and their effects in cereals and oilseeds.

With much of the data coming from outside of the UK and from glasshouse trials, we didn’t know how they perform in the field or under UK conditions.

Current research is very much ‘work in progress’. ADAS-led work, for example, has only been able to test a small proportion of the hundreds of biostimulant products on the market. So far, few have shown consistent statistically significant positive effects on crop performance.

Despite research over the last five years, we still lack evidence and require a better understanding on pretty much everything – from timing to rates, as well as their interactions within cropping systems.

Next year, manufacturers will have to supply evidence on the efficacy and safety of products to justify their claims and sell their products across Europe. It should help UK growers identify biostimulants with proven benefits.

While the jury is still out, Kate recommends farmers conduct small in-field trials to help determine biostimulant efficacy, before making significant investments. ADAS’ Agronomics Guide to Farmers Crop Trials contains advice – from design through to analysis – to help improve the accuracy of any trials.

Angus Gowthorpe farms in the Vale of York. He has transitioned to regenerative agricultural systems and maintained gross margins across his rotation. As part of the approach, he uses biology to farm with nature. Biostimulants form an important part of his crop management. In the last eight years, he has also seen organic matter content double.

When it comes to nutrition, Angus focuses on microbiology. In particular, he keeps nitrogen rates low – to avoid exceeding 180kg/ha of nitrogen – to prevent a shutdown of soil biology activity. He also applies urea, which is thought to be less harmful to soil biology than ammonium nitrate.

Soil microbes need energy in the form of carbon to process nitrogen. Angus uses a form of fermented molasses to deliver carbon (otherwise microbes tend to use soil carbon), as well as non-microbial biostimulants (humic and fulvic acids).

He also uses microbial biostimulants, as part of efforts to replace fungicides and plant growth regulators (PGRs). He uses products that contain plant growth promoting bacteria (Bacillus spp.) and non-pathogenic fungi (Trichoderma spp.) Foliar applications include the plant growth promoting Rhizobacteria and orange oil.

Left: Philip Dolbear, an AHDB knowledge exchange manager.

Right: Kate Storer, ADAS crop physiologist.

Gary Shipley, Huggate monitor farmer.