Cabbage stem flea beetle (CSFB) remains one of the biggest barriers to reliable winter oilseed rape (WOSR) establishment. While pressure varies year to year, CSFB is consistently capable of causing significant early plant loss and uneven crops. With fewer effective control tools available, attention is increasingly turning to fundamental changes that can be made during establishment — from prioritising soil health to using integrated approaches that help crops tolerate stress and reduce the impact of early feeding.

Research carried out at NIAB’s greenhouse testing facility in Cambridge has explored whether a fish hydrolysate application could influence CSFB feeding behaviour during the most vulnerable growth stages. The work focused on young, establishing oilseed rape plants and assessed damage to cotyledons, leaves and stems compared to untreated controls.

In the trials, applications of Sea2Soil were associated with reduced feeding damage across multiple plant parts, with NIAB reporting reductions versus untreated plants of 32% on cotyledons, 90% on leaves and 59% on stems.

Importantly, the results suggest timing plays a key role in any potential benefit. Sea2Soil applied at half, full and double field rates, with a full field rate for WOSR referenced as 10L/ha, showed a significant reduction in CSFB feeding on cotyledons within two days of application. The same application rates were also linked to lower cotyledon feeding damage for up to seven days after application, with indications that this cover may last until cotyledons senesce.

Adrian Harris, NIAB Lead Researcher, commented: “Sea2Soil showed a significant reduction in the feeding of cabbage stem flea beetles on cotyledons within two days of application – several different rates showed a reduction in feeding damage up to seven days after application and may convey cover until they senesce.”

The NIAB findings form part of Sea2Soil’s wider research and development programme, which has seen the product involved in collaborative research with a number of leading UK organisations over a four-year period. This long-term trials work has been important in building a clearer picture of Sea2Soil’s wider role in soil health, plant growth and crop resilience.

Guy Gibson, trials agronomist at Enhanced Efficacy, said long-term trials work, high-quality research and key indicators are crucial to assessing the overall success of Sea2Soil as a soil improver and improving understanding of the product’s wider capabilities.

Although this latest work is focused on pest feeding, it sits within a broader conversation about building establishment resilience. Early season crop performance is tightly linked to nutrition availability, root development and soil function, particularly where crops face multiple stresses at once, including drought, waterlogging, pest pressure and disease risk.

Sea2Soil’s wider impact on soil activity and biology is already being explored through indicators such as worm counts, pH, carbon retention, organic matter, soil moisture and porosity. These wider soil-health benefits are particularly relevant as growers look for approaches that can support resilient crop establishment across conventional, regenerative and organic farming systems.

Liz Brown, Sales Manager at Pelagia, added: “We see Sea2Soil as far more than a natural source of nitrogen and amino acids, but as a soil prebiotic that leads to a healthier soil environment, better crop health and confers increased resilience to environmental and other crop stresses which are becoming more prevalent in UK farming season on season.”

With volatility continuing across global markets, disruption to UK fertiliser costs and supply into 2027 remains a live concern. As a UK-sourced and manufactured input that supports nitrogen and amino acid supply as well as soil biology, Sea2Soil offers farmers an alternative solution ahead of the autumn season — not only to help minimise the potential impact of these global issues on yield, but also on input costs and margins.

For growers and Sea2Soil’s UK distribution partners, the NIAB findings offer a useful addition to the evidence base around establishment support in winter oilseed rape. The Sea2Soil team is also planning to extend its research trials in the 2026/27 season, continuing to explore how fish hydrolysate applications can support crop resilience at key establishment timings.

Terrafarmer-run farm trials, funded through an Innovate UK research project, are testing and comparing a range of different biological stimulants applied to grassland. Results so far have shown their potential to reduce inputs and improve grass quality.

How has Sea2Soil performed?

Sea2Soil fish hydrolysate delivers a wide range of plant-available amino acids, macronutrients and trace elements to both the crop and soil. Sea2Soil performed very highly in all trial measurements taken, including giving increases in kilograms of dry matter (DM)/ha, crude protein, trace element availability, and microbial biomass, when compared with a control treatment.

According to regenerative agronomist and soil consultant Will Marris at Terrafarmer, a number of products tested (including Sea2Soil) are improving crude proteins and sugar. “If that goes into a silage clamp, you’ve got more sugars for the fermentation process. If you get a better fermentation, you get better-quality forage.”

Out of 7 biological product treatments tested in the trials (over 7 different farm sites), Sea2Soil ranked No.1 and performed highest for crude protein improvement (at 136.225 g/kg) compared to all other products and the control treatment. Sea2Soil also ranked No.3 out of all treatments for improving microbial biomass in mid-season assessments taken. Each farm trial site used large 20 x 160m strips to test all treatments and baseline analysis measurements were taken for all products tested for comparative purposes.

Sea2Soil fish hydrolysate, as a naturally high source of protein and carbohydrate, is a perfect choice for improving soil biology. “By feeding the beneficial underground livestock in the soil i.e. the bacteria and fungi, these in turn are helping with the mobilisation of vital trace minerals such as boron, manganese, and magnesium,” says Grant James, Business Development Manager, Sea2Soil.

Soil, leaf, and forage tests from the trials show more of those nutrients being readily plant-available moving from the soil into the leaf, and therefore into the forage. “This could even reduce the need to supplement trace minerals given to livestock through licks or drenches,” suggests Will.

How biologicals like Sea2Soil work to benefit plants

Traditional fertilisers such as urea or ammonium nitrate prills have an efficiency rate of about 50%. By contrast, solubilised and foliar-applied alternatives can be almost twice as efficient, so less nitrogen is needed.  “If foliar nitrogen is applied with biologicals such as molasses, fish hydrolysate, and fulvic acid, nitrogen use efficiency is improved, as you’re applying plant-available nitrogen to the leaf, which is a more direct route into the plant. That’s safer for the plant, but also beneficial and safer for the soil,” explains Will. “You’re feeding the plant and the soil at the same time, and the nitrogen doesn’t get lost via volatilisation or tied up in the carbon and nitrogen cycles in the soil.”

By applying biological and soluble fertilisers like Sea2Soil, farmers can build soil function and fertility, carbon and organic matter, all generally at reduced cost. “Biologicals are inherently more sustainable than a manufactured synthetic nitrogen source,” continues Will. “We’re not saying don’t use any, just try to use a bit less and make it more efficient.”

Valuable cost savings being realised

Using biological and foliar fertilisers can also bring significant cost savings. For example, a grass-based, multicut system might use 250kg/ha of nitrogen. Based on a standard urea application, using a 46% urea product, at a cost of 46p/kg, the cost would be £115/ha. Will explains: “Where we have added in two biological products, molasses and fish hydrolysate (Sea2Soil), to the foliar nitrogen mix, we had a saving of £5/ha,” he says. “A total cost of £110/ha to get a more efficient form of nitrogen into the plant, while reducing nitrogen use by 20%, is quite significant – and you’re feeding the soil.” He adds that nitrogen application rates can, over time, be reduced even further.

“You could easily reduce inputs starting at 25% to 50%, but that wants to be done over a few years in a managed reduction,” he advises. In addition, there is the potential for farmers to save on inputs such as mineral supplements because of the improved flow of nutrients from soil to forage with Sea2Soil and other biologicals.

Timing of application is important

The time of day and weather conditions can make a significant difference to the effectiveness of biologicals and foliar nitrogen, Will says: “If you’re looking at foliar nitrogen plus biologicals, it’s important to time your application right. Early in the morning is a good time, because that’s when the stomata are open.”

He adds that in the morning, especially, the plant will not be overly stressed, so is better at taking in the product, leading to greater efficiencies. While temperature is an important consideration, UV index and humidity should be considered first when applying biological fertilisers and foliar applications.

“When you have a high UV index, the plant is conserving moisture, and it’s not going to want to take in any nutrition,” says Will. “So the biological fertiliser or soluble nitrogen will sit on the leaf and can scorch or burn it, particularly if you’ve got urea in there. It’s best to apply these when the UV index is low and humidity is high. Humidity means moisture, and that means stomata are open to take in these products.”

Sea2Soil recommends applying the product to grassland in 2 or 3 split applications in early spring, mid-spring and late-spring or early summer, and it is also worth taking into consideration grazing cycles as well, so product application is timed around those periods, as Grant explains: “For grassland and herbal leys, applying Sea2Soil at 10 L/ha just before the start of the active spring growth period sets a good baseline and then follow-up with at least one repeat application in May.”

Multiple Sea2Soil foliar applications of 5-10 L/ha can be made in the season up to 3-6 times a year, and Terrafarmer trials work is showing that a ‘little but often’ approach to applications can work well in many grassland situations.

For more information about trials work with Sea2Soil or about using the product this season, please contact Grant James directly.

E: grant.james@pelagia.com

T: 07976 879646

Acknowledgments: Sea2Soil would like to acknowledge Terrafarmer Innovate-UK trials work and

FW / FWi 04 Nov 2025 article ‘Biological Stimulants: Are they good for grassland?’, read the full article here.