Herbal leys for arable soil health

As part of the monitoring process, the coordinator re-visited the sites in May to re-survey the leys and test the forage, before they were grazed or cut for silage. Forage quality is tested by cutting vegetation down to 7 cm to mimic grazing and sending these samples to the lab for Dry Matter testing.

The Dry Matter testing confirmed observations from May surveys, with Farm C being the most productive field for herbs in the sward. Despite using the same seed mix, and only situated 400 m away from each other, the results from the two sites at Farm B revealed varying species cover. Site B(i) had a significantly higher weed burden (weed defined as unplanted species in the ley).

This farmer group will continue assessing its trial sites over the coming year, monitoring how each site changes as the sward establishes; reducing compaction and erosion as well as increasing soil organic matter.

For more detailed results and images of the sampled areas showing the cover crop establishment, see the Progress Review document in the reports section of the field lab page.

Continuing to look at the four farms (A-D)
Using 1 m quadrats, the species diversity and richness was assessed at each of the 5 field lab sites (across 4 farms with the ratio of herbs: grass: bare soil visually assessed and photographed).
The sites varied dramatically, with cover ranging from 5 % herb to up to 85 % herb, with clover, chicory and plantain most common in the sward. Other less common species including sainfoin, birds-foot trefoil, and salad burnet added to the diversity of the swards. It is this diversity of species that increases the benefits derived from the leys, including carbon capture, nitrogen fixation, food for pollinators and water retention, while increasing populations of nematodes, earthworms, mycorrhizal fungi and other biotic life.

The four farmers will each sow a field with the herbal ley mixes recommended through consultation with their seed companies. Three farms have the same herbal mix applied (one being organic). One farm has a slightly different mix applied. These trial fields will be treated as under each farm’s standard practice in order to ensure comparability to the controls.

Controls
Ideally, half a field would be sown and half a field left to the standard practice to act as a control, however it is not practical for this farming group to do this, and so they will use alternative control methods. Farmer A has agreed to leave a strip of the trial field to the standard grass as a control comparison. Farmer B, C and D will use an adjacent field with similar slope, soil and aspect characteristics sown with their standard grass as a control. Further, Farmer B has decided that he would like to trial two fields of herbal leys and so will sow an extra field than the other farmers’ trialling.

In addition to these control fields / strips, soil tests of the trial fields have been undertaken prior to sowing the herbal leys, in order to add further strength to the comparisons. These include soil organic matter testing (loss on ignition through NRM labs), VESS tests and infiltration

After a morning farm walk looking at wild bird seed mixes with King's Seeds at Harnhill Rural Innovation Centre, the coordinator, researcher and Innovative Farmer field lab officer visited the cover crop plot of one of the triallist's, which was sown in May. The farmer was able to get this sown in a tight gap between a wet Spring and a very dry Summer. The trial plot is on very stony Cotswolds brash, and the triallist hopes to increase the soil and organic matter by using cover crops as part of the arable rotation of wheat, rape, wheat and spring beans. He is currently limiting the trial to part of a field which will half be sown with a wild flower seed mix, to be used as a control in addition to taking soil measurements before and after the cover crops were sown.

The coordinator and triallist commented that the cover crop had looked patchy over the dry weather post-sowing, however with some rain early autumn, the plot is now looking very green and lush.

The researcher used a quadrat to take randomly selected vegetation samples including: 2 for a species count and 3 for forage quality. Photos of the cover crop were also taken.

She showed the coordinator how to do this, who will coming back before the plot is grazed in late December - early January and in Spring around April. For species count, the samples were taken from the base of the crops so that all above-ground parts of the plant can be used for identification. For the forage quality, the crop was cut at 7 cm as would be if grazed.

The coordinator has been out to the triallists farms before the seed is sown to measure soil health to compare as a baseline to measurements after the herbal leys have been sown.

Two of the triallists have bought their seed and two are waiting to get their seeds. One farmer has sown early, however the others have now decided autumn would be best due to the hot dry weather which has parched the soil. The triallists are now busy harvesting and will plan to meet in the autumn to review the methods and measurements to be taken once the seeds are sown. The coordinator will be visiting the triallist who has sown to take measurements and discuss progress.

Soil organic matter (SOM) tests have recently been returned from the trial sites for pre-herbal ley establishment, giving surprisingly high results: 6.9 – 11.7%.

The remaining soil tests will be carried out on control fields, including VESS, aggregation, infiltration and compaction.

All farms (A-D) will have the following measurements recorded at 3 month intervals during the trial (June, September and December, additionally to those taken pre-sowing) to assess changes as the herbal leys develop:
- Soil organic matter (loss on ignition, NRM)
- VESS (soil structure)
- Aggregate stability
- Earthworm counts
- Infiltration
- Compaction
- Species composition of herbal leys (assessment of which species are performing best in which soils)
- Biomass testing (quadrat cuts to measure and compare fresh and dry control and herbal ley weights)

The above soil tests will also be conducted the following year in early spring to assess changes post herbal ley growth.

The four farmers will each sow a field with the herbal ley mixes recommended through consultation with their seed companies. Three farms have the same herbal mix applied (one being organic). One farm has a slightly different mix applied (see appendix for species).

These trial fields will be treated as under each farm’s standard practice in order to ensure comparability to the controls. Ideally, half a field would be sown and half a field left to the standard practice to act as a control, however it is not practical for this farming group to do this, and so they will use alternative control methods.

Farmer A has agreed to leave a strip of the trial field to the standard grass as a control comparison. Farmers B, C and D will use an adjacent field with similar slope, soil and aspect characteristics sown with their standard grass as a control. Further, Farmer B has decided that he would like to trial two fields of herbal leys and so will sow an extra field than the other farmers’ trialling.

In addition to these control fields / strips, soil tests of the trial fields have been undertaken prior to sowing the herbal leys, in order to add further strength to the comparisons. These include soil organic matter testing (loss on ignition through NRM labs), VESS tests and infiltration measurements.

All farms (A-D) will have the following measurements recorded at 3 month intervals during the trial, additionally to those taken pre-sowing, to assess changes as the herbal leys develop:

Soil organic matter (loss on ignition, NRM)
- VESS (soil structure)
- Aggregate stability
- Earthworm counts
- Infiltration
- Compaction
- Species composition of herbal leys (assessment of which species are performing best in which soils)
- Biomass testing (quadrat cuts to measure and compare fresh and dry control and herbal ley weights)

Soil health assessments were informed with the researcher Becky Willson and are from the Farm Carbon Cutting Toolkit. Due to farmer time limitations these will largely be carried out by the group coordinator:

VESS

Sample at three locations across the field that are representative of the field conditions. GPS log your location so that you can return next year. Extract a soil block using the spade, approximately one spade’s width and depth. Then examine the soil block for structure.
Use the VESS scorecard to record the score for the top soil and the subsoil. Record in the field book.

Aggregate stability

While you have dug the soil up to perform the VESS test, take a fistful of soil and place in a labelled sample bag.
Once back in the lab, remove 4 aggregates from the sample and lay out on a labelled tray to dry for 5 days (airing cupboard or warm place). Once the samples are air dried place the aggregates into rainwater and score them using the Aggregate stability scoring system after 5 minutes and two hours. Record results.

Worms

Sample at three locations across the field that are representative of the field conditions. GPS log locations so that you can return next year.
Extract a soil block one spade depth, and width onto a plastic sheet. Sort through the soil and count the number of worms that you find. Record the data. Return soil.
Infiltration test

Choose 3 sites across the field that are representative of the field conditions, GPS log the locations.

Insert the bulk density cylinder into the soil using the hammer and wooden block to the line on the cylinder (3 inches up).
Measure out 107ml of rainwater into the measuring jar (line on jar as to required volume).

Insert into the cylinder the cling film, making sure the edges of the film are over the cylinder.
Gently pour the water into the cylinder.

Get stopwatch ready. At the same time start the stopwatch and remove the clingfilm. Time how long it takes for the water to infiltrate and stop the stopwatch when the soil glistens (but water has gone).

Record in field notebook.

More details on these methods can be found online here: https://www.farmcarbontoolkit.org.uk/news/carbon-farming-project-update

Initially, information has been gathered from each farmer on the previous farming applications to the trial sites; each farmer filled in a survey that detailed the previous crop, fertiliser applied, topography, susceptibility to drought, flooding issues, and land management issues. This helped to identify the field lab aim, what herbal ley mixes were best for each farm and the tests that need to be carried out in order to establish whether benefits are seen from incorporating them into each farmer’s rotation (satisfy the trial aim).

The range of soil types varies from shallow lime rich soil to slightly acid but base rich loamy & clay and free draining lime-rich loamy across the 4 farms which total 103 Acres.

Farm profiles in brief:

Farm A has been quarried previously and has no quality soil to grow crops on. The soil is compacted, part gravel and dry. The farmer wants to grow wheat, barley and oil seed rape (OSR) in rotation.

Farm B is on flooded land and has been sitting underwater for a considerable amount of time, previous crop miscanthus. The organic matter is visible but no earthworms, the soil is compacted and slightly grey in colour.

Farm C has been over worked, it is Cotswold brash soil which is full of stone, but does have some earthworms present.

Farm D is organic, has had flooding issues in the past and is compacted with few worms observed.