14 February 2023
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FERA Science, M&S and growers look at sustainable control and soil assessments.
FERA Science has been working together with Marks & Spencer and some of the country’s leading potato growers to demonstrate how nematode numbers can provide an assessment of soil health, and how pest species, such as potato cyst nematode (PCN), can be controlled in a sustainable manner.
Based near Holbeach in South Lincolnshire, Worth Farms grows 350 hectares of potatoes across 2,600ha of Grade 1 silt soils, together with cereals sugar beet, vining peas and maize. Land is also let to growers of vegetable and salad crops. The main varieties grown include Maris Piper, Melody, Marfona, Desiree and Nectar.
Farm manager Simon Day has had a longstanding focus on sustainability – the current potato rotation is one-year-in-eight, and the maize crop is used in an anaerobic digester, with digestate returned to the land to improve organic matter. For the last two years, Worth Farms has been working with M&S as part of the retailer’s Farming with Nature initiative, which is aimed at reducing greenhouse gas emissions from vegetable and livestock suppliers.
As part of the project Fera Science has assessed nematode populations on the farm as an indicator of biodiversity and soil health. Fera’s Senior Nematologist Rebecca Lawson said:“As nematodes cover different parts of the whole food chain within the soil web, they are very good indicators of soil health.”
Fera has used this principle to develop a biological-based measure of soil health which can be used to give management insights into the functioning of a soil.“This approach in using bioindicators including both plant-parasitic and in-soil nematode groups applied to practical on-farm management practices in the UK, provides a holistic approach to quantify what is currently in the soil,how current farm management is affecting the soil biology, and how you can influence and manage this going forward to maximise yields,” she adds.
The longer rotation has enabled the farm to reduce its use of nematicides. It currently uses fosthiazate on 60-70% of the potato land and average yields have increased from just over 50t/ha a few years ago to 55t/ha today, although some crops of Nectar can reach 80t/ha.
A farm soils currently have a good balance of nematodes (including beneficial species), and Rebecca says that as a result, the use of nematicides could be further reduced in the future:
“There could be a future outcome where the soil health improves and the nematode balance is good, and then we might be able to do without a nematicide,” she explains. “We have seen improvements in diversity from autumn 2021 through to spring 2022, largely from the use of cover crops and reduced cultivations.”
Most of the potato crop is grown after vining peas. Once the pea crop has been harvested, a subsoiler-discpacker-roller combination is used to cultivate and sow a cover crop, then in the spring another cultivation pass is followed by a combined rotavator planter which plants the potatoes.
In the past the farm has tried biofumigant cover crops with mixed results, while other cover crop mixtures containing vetch, phacelia and radish grew too big on the farm’s fertile soils.
“We are on a learning curve with cover crops,” says Simon, who hopes that once a successful mixture is identified, will allow nitrogen rates on the potatoes to be reduced by as much as 18%. “We want to be in the situation where, if fosthiazate disappeared tomorrow, we would still be able to grow potatoes,” he adds.
