Why a fish-based soil improver may help plant growth
© GNP Reducing reliance on synthetic inputs while meeting environmental targets is the aim for most arable farms as they prepare for life without the Basic Payment Scheme and far greater scrutiny of farming practices.
In Lincolnshire and Yorkshire, four regenerative farmers are putting a new fish hydrolysate soil improver through its paces, following its approval by the Soil Association and the refining of the product by manufacturer Pelagia to make it suitable for sprayer applications.
See also: How arable farmers can turn things around this spring
Originating from the Scottish salmon farming industry, the nutrient-rich by-product known as Sea2Soil is increasingly forming part of their approach to maximise nutrient delivery, as well as help to feed soil biology and improve soil function.
What is it?
A by-product of the fish industry, fish hydrolysates contain amino acids and fatty acids, as well as micronutrients, in a bio-available form.
The hydrolysis process breaks down complex proteins into their component amino acids.
Using the symbiotic relationship between plant roots and soils, the farmers’ goal is to get nutrient cycling working well, while producing healthier plants that can withstand pest and disease attack and environmental stresses.
The ability of plants to absorb nitrogen via foliage is also being investigated, as they look to improve uptake efficiency.
James Walgate – Market Rasen, Lincolnshire
Now in his third year of using Sea2Soil, James Walgate says the initial plan was to use it to feed soil biology, rather than the plant.
He has been applying it at drilling, at a rate of 5 litres/ha, along with a carbon source, seaweed extract and humic acid.
“We are building up the soil biology so it can play a role in feeding the plant and keeping crops healthy,” he says.
Having had good results with the product as a seed drench, he is now starting to look at foliar applications, also at 5 litres/ha.
“I’m only just starting down this route, but providing the nutrients in an available form is key to their uptake.”
Restrictions
Sea2Soil cannot be applied to any edible part of the plant and has a withdrawal period of 21 days when used on grass before animals are turned out.
Colin Chappell – Hibaldstow, Lincolnshire
Stimulating soil health is the reason Colin Chappell decided to try some Sea2Soil on his heavy clay soils with a high magnesium content.
Given the farm’s proximity to the River Ancholme, his soils are often waterlogged and soil structure takes a hammering when flooding occurs, so Colin has been working on making them more resilient.
He has seen a yield benefit from using Sea2Soil, with a peri-emergence application on spring beans giving a 0.4t/ha uplift, while canary seed increased by 1t/ha. In 2023, he achieved an extra 0.5t/ha with spring peas.
“I am applying it at 5 litres/ha with a carbon source known as Carbon N Balancer,” he reports. “My understanding is that as it’s in a form readily available to the plant, its uptake is better.”
Jonathan Hodgson – South Frodingham, East Yorkshire
East Yorkshire grower Jonathan Hodgson is in his third year of using Sea2Soil, having used the product via the liquid system on his drill.
Applied at a rate of 6 litres/ha with humic acid as crops are drilled, Jonathan’s aim has been to improve soil biology while also being able to replace the use of seed treatments.
In addition, he is in the early stage of foliar applications. “I put some onto the oilseed rape this autumn to see if it could help with flea beetle control. The jury is still out on whether it’s worked or not.”
Paul Davey – Market Rasen, Lincolnshire
Combinable crops, herbal leys and cover crops all receive Sea2Soil at Paul Davey’s farm in Lincolnshire.
At a cost of about £800/t, he uses up to 35 litres/ha on wheat in four applications, with 10 litres/ha applied to the soil in the autumn, a further 10 litres/ha used in the spring and the remaining 15 litres/ha going in with his sprays.
That comes to a total cost of £31/ha, he calculates. “If it’s going down the spout at drilling at a rate of 5 litres/ha, it costs £4.30/ha.”
He has found that it helps crops cope with drought stress, especially those drilled in late spring, and is investigating how it helps reduce synthetic nitrogen fertiliser applications.
How does it work on nitrogen uptake?
Growing bigger root systems, combining inorganic and organic forms of nitrogen and supplying trace elements will all help crops to improve their uptake of nitrogen, according to independent educator Joel Williams.
This combination helps with nutrient capture in the roots, provides the plant with the building blocks it needs to metabolise nitrogen fertiliser applications, and ensures that the process is working well, he explains.
“It’s not just about applying fertiliser and getting it into the plant, the efficiency of nitrogen utilisation also matters.”
Nitrogen efficiency
Organic forms of nitrogen come in various guises, he notes, including proteins, peptides and amino acids, all of which are more efficient forms of nitrogen for plant growth.
This is because they also have carbon embedded in them, which he views as a bonus, as the plant expends less energy converting them compared with inorganic forms.
While they are the most efficient, they tend to come with a greater cost per unit of nitrogen, acknowledges Joel.
In contrast, inorganic forms of nitrogen, such as nitrate, are the least efficient, as they induce a greater demand for other nutrients needed as enzymatic co-factors.
They also draw down higher amounts of photosynthetic carbon to convert them into organic forms. “It’s more costly for the plant to use them,” he points out.
From an economic perspective, a balance of both types is advised, says Joel.
“Inorganic forms trigger the early stages of the metabolic pathway, while organic forms work on the later stages. There are benefits to including a combination of forms.
“Ensuring the right trace elements are present means the metabolic pathway for protein synthesis works well.”
Amino acid-based N
As fertilisers applied as either ammonium or nitrate require the plant to convert them into the amino acids it needs for this pathway, using an amino acid-based nitrogen has the potential to bypass this process and speed up nitrogen use.
It also allows foliar applications to take place. “Soil applications of nitrogen are vulnerable to losses from volatilisation and leaching and we know that plants can absorb nitrogen via the foliage.
“This is where protein hydrolysates, which can be plant- or animal-based, can have a role.
“As well as being good for rooting characteristics and growth, they supply the amino acids that are essential for plant health and are absorbed most rapidly.”
Foliar applications of urea are also more favourable as the nitrogen enters the plant as urea, an organic form, he adds.
“These organic forms of nitrogen have a metabolic shortening effect and saves the plant’s energy.
“So there’s an efficiency gain to be had where they are being used in an integrated approach.”
