Diverse roots revealed at cover crop champion site in Essex

Our first post-emergence video shows clear evidence of diverse rooting of a multi-species cover crop mix at a farm site in Essex.

The farm in East Anglia is one in a network of eight cover crop champions set up by AHDB Cereals & Oilseeds to provide practical case studies on the impact of cover crop approaches.

Following on-farm trial design principles, each of the champions has established a cover crop ahead of various cash crops for harvest 2025.

Jonathan and Jane Clarke’s farm (Bury Farm) is in Great Canfield, Essex.

Trial approach

The farm’s rotation provides plenty of opportunities for short-term cover ahead of spring crops.

As cover crops are only being grown on the farm for the second time, they are still experimenting to identify what works best in their system. This year, the Clarkes are testing three establishment techniques:

1. Direct drilled into stubble.
2. Broadcast followed by harrowing over the top (lightly scratching under the stubble).
3. Broadcast with a light cultivation.

They have opted for a six species cover crop mix that contains buckwheat, crimson clover, hairy vetch, linseed, phacelia and a specialist fodder radish (Smart Radish).

The cover crops were sown in late August, with the plants established via broadcast methods slower to get going, due to poorer seed-to-soil contact.

Early assessments

Harry Moffat, from Oakbank Game & Conservation Ltd (which part-funded the trial), dug up samples on 4 October and placed them side by side (on a spade) to reveal the rooting characteristics:

• The buckwheat was already going deep
• The radish had long, thick roots
• The linseed had long, thin roots
• The vetch had many thin roots, which were reluctant to let go of the soil
• The phacelia was just getting going

At the time of assessment, clover was sparse, with no good samples available for sampling.

Interestingly, the most impressive roots were from volunteer borage. Borage was cropped in the field two years ago, with its offspring taking up residence in the field’s seedbank.

Compared to the cover crops, it had a head start and featured the thickest roots of the bunch. Jonathan isn’t too concerned as it all adds roots to the mix and it should be knocked back by the first hard frosts.

Although not unexpected, where the land was lightly cultivated, borage’s growth was clearly subdued – unlike where the cover crop was direct drilled into the stubble of the previous crop, where borage was already waist height.

The presence of diverse roots should help maximise the benefits of the cover. For example, it will improve the overall structure of the soil and mine nutrients deep within the soil profile. The legumes will also fix nitrogen (with nodulation already visible on the vetch).

The buckwheat is already flowering, which is offering something for the pollinators too. Once again, it should break down at the first good frost.

We will now assess the development of the cover crop’s biomass before terminating it and establishing a spring cereal crop next year.

Cover crop roots on display

Above: Plants from the cover crop trial field in Essex showing diverse rooting characteristics. Left to right: volunteer borage, radish, linseed, phacelia, vetch and buckwheat.

Unlike the other cover crop champions, Anthony Becvar is using more year-round cover crops on his very heavy Wealden clay soils, which are prone to slumping and compaction (especially when in winter cereals). The ground was hard prior to establishing the cover.

• A multi-species mix* was drilled in the third week of August
• It will stay in the ground until next autumn
• It came up well and is providing good ground coverage
• The hope is that the deep tap roots will break soil pans naturally and support strong biomass
• The soil is already aggregating nicely from the surface down
• The buckwheat shot away quickly but was knocked back by early frosts (at the end of September)
• The two types of radish are taking advantage of the space (and soaking up water)
• Worm activity is clearly picking up around the roots (counts were low before establishment), with ground beetles present too
• The untreated control strip (no cover crop) is much tougher to break with a spade, with little signs of aggregation and life
• A second, contrasting mix* (heavily weighted towards forage rye) is also being trialled
• The rye has been nobbled by slugs (which were not a problem elsewhere)
• The cover was in sown into a mulched rape-based cover crop (which contributed to the slug pressures)
• Once again, radish is taking advantage
• This cover is not as effective as the first mix
• There are still compacted areas (but not as many as in the no-cover control)
• An option in the spring is to patch up the crop with some quick-growing cover

*The first mix comprises: buckwheat (35%), linseed (15%), daikon radish (15%), fodder radish (12%) crimson clover (12%), gold of pleasure (6%) and phacelia (5%). The field’s weed populations add more roots. The second mix comprises: forage rye (60%), winter vetch (30%), fodder radish (7%) and white mustard (3%).

The challenging conditions led Ian Matts to deviate from his usual approach to getting cover in the ground.

• Usually cover crops are established with a Väderstad carrier disc cultivator with a mounted drill
• The challenging, late harvest and dry conditions meant a Sumo Trio cultivator was used to exploit its deep loosening legs to prepare the land to receive the seed and the slug pellets
• The trial was not drilled until very late September (with other parts of the farm, on more forgiving soils, prioritised first)
• The farm uses a cover crop mix from Oakbank: buckwheat, crimson clover, phacelia, linseed, fodder radish and vetch (seed rate 12.5kg/ha)
• The soil should still have enough heat and, hopefully, moisture to get the trial established
• Ian is taking advantage of some real-time nutrient uptake and moisture monitoring technology (Paul-Tech probes) to compare the cover crop trial with an unsown (but cultivated) control in the field opposite
• The late drilling may reduce the differences but it hoped it will still be possible to detect treatment effects

In October, Jason Hendy visited Bob King’s trial and saw a clear tale of two stories in the two treatment fields.

• The treatments used the same seed mix, drilled at the same time, in the same soil type (the fields are one hedge apart) with a similar soil health (including nutrition)
• One field was cultivated and drilled, the other seeded with a scratch-harrow regime
• The scratch-harrowed crop emerged but never really got moving, which made the crop game for flea beetles (which feasted on the many brassica species in the mix)
• The cultivation improved the seed-to-soil contact, helping the cover take and grow away (with flea beetle damage limited), producing healthy growth
• It is interesting to note that the region’s winter oilseed rape was largely unscathed by beetles in the autumn
• An undrilled control strip has some limited, natural regeneration (mainly from groundsel and grass weeds, with a few volunteers)
• The plan is to graze the trial from mid-to-late October but there is a dichotomy: there is much more fodder on the cultivated side, but the soil on the scratch-harrowed side is in a much better condition to carry the animals

About the cover crop champions

First pioneered in the USA, cover crop champions tackle the complexity associated with cover cropping and share their experiences with other farmers.

Supported by AHDB, the champions will record core measurements and observations to help assess the impact of their varied approaches.

We plan to release post-establishment updates for all champions over the next few weeks.

You can follow their journeys on the cover crop champions web page.