Improving hop soils through cover cropping

When hops are harvested, the entire plant is removed from the field so the organic matter is not returned to the soil as part of the normal cropping cycle. Some growers import and spread OM, but it may be easier and better to grow it in situ during the autumn and winter, via the use of cover crops.

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Field Lab Timeline

    8/13/2017 11:00:00 PM
  • Initial idea formation

    Initial idea formation
  • 8/20/2017 11:00:00 PM
  • Methods discussed & finalised

    Methods discussed & finalised
  • 9/8/2017 11:00:00 PM
  • Crops drilled

    Crops drilled
  • 11/13/2017 12:00:00 AM
  • Baseline data collection

    Baseline data collection
  • 1/8/2018 12:00:00 AM
  • Initial data evaluation

    Initial data evaluation
  • 2/12/2018 12:00:00 AM
  • First year reflections

    First year reflections
  • 3/5/2018 12:00:00 AM
  • Progress meeting

    Progress meeting
  • 3/9/2018 12:00:00 AM
  • Cover crop termination

    Cover crop termination
  • 8/13/2018 11:00:00 PM
  • Harvest

  • 9/4/2018 11:00:00 PM
  • Second year cover crops drilled

    Second year cover crops drilled
  • 9/23/2018 11:00:00 PM
  • Second year aims & methods meeting

    Second year aims & methods meeting
  • 1/1/2019 12:00:00 AM
  • Establishment of cover crops Year 2

    Establishment of cover crops Year 2
  • 3/30/2019 12:00:00 AM
  • Cover crop termination year 2

    Cover crop termination year 2
  • 8/31/2019 11:00:00 PM
  • Second year review/ third year planning

    Second year review/ third year planning
  • 9/12/2019 11:00:00 PM
  • Third year cover crops sown

    Third year cover crops sown
  • 3/20/2020 12:00:00 AM
  • Third year cover crops terminated

    Third year cover crops terminated
  • 3/29/2021 11:00:00 PM
  • Cover crop termination yr 4

    Cover crop termination yr 4
For further information hover over the above milestone marks
  • Discussion

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  • Achievements

    April 2020

    Crimper rolling of cover crop; delay to soil sampling

    One of the farmers tried using a crimper roller on his oat and rye mix, but reports very poor results. Terminating the cover crop before it was mature meant that it was difficult to achieve sufficient bruising and crimping to damage the cover crop. In order to lay it on the surface, the farmer had to resort to terminating the cover crop with glyphosate. However, it may be that the same degree of damage can be achieved using less glyphosate combined with using a crimper roller.

    The group have relied on a shared xx One farmer fed back that safe to use to kill or remove the crop and a seeder that will only apply seed into the row ie direct drill.

    Soil assessments were intended to take place this April. However, having spent the first two years playing around with seed mixes, timings and seeding rate, the group will postpone soil sampling this year to give more accurate, longer-term readings of the impact on soils.

    Milestone: Third year cover crops terminated

    March 2020

    Third year cover crops terminated

    In the third year, two of the four farmers extended cover cropping to most of their growing area. Cover crop was planted early, following the successes of the second year. Third year crops crops are currently being terminated - either sprayed off with glyphosate or gone over with a crimper roller. The group hope that the mat of foliage left by the terminated cover crop will suppress weed germination in the alleyways; this was an unexpected benefit last harvesting season.

    Some of the group members have reported interest from neighboring farmers, who have started to try cover cropping for themselves.

    Milestone: Third year cover crops terminated

    April 2019

    Cover crops terminated

    The second year of cover crops have now been terminated using a variety of methods as determined by each grower.

    To read more about one of the triallists experience of this field lab, check out the blog under the news section of this website, or go to

    "We chose black oats for our cover crop. This is because it is a hardy crop that would grow in the clay. And we can’t use broadleaved plants like legumes because they can carry wilt which could spread disease in the farm. So last year we broadcast it just after harvest and rolled it. It grew very well where we put it in. We tried different seed rates and discovered that it needed a higher rate of 75kg per ha. The higher the better on our soil to get a better establishment, however we had to balance that against seed cost. We let it grow all the way through the winter and just before the hops came through we put glyphosate on it to ensure it was dead, and we just let it fall over naturally. Now it’s mulching down and in a few weeks it will decompose into the soil."

    Milestone: Cover crop termination year 2

    February 2019

    Cover crop establishment

    The group is learning to understand parameters for getting good establishment in hop soil situations, and were able to achieve better establishment in the second year of growing cover crops. One of the growers has sown cover crops on about 6 acres - roughly 10% of the farm, and has already seen benefits such as less erosion, better trafficability, and now the cover crops have been terminated the mulch is adding to soil fertility. Whilst impacts on yield aren't easy to measure, given other variables such as weather, this triallist has deemed the cover crops a great success and has decided to sow them over the whole farm this summer, with the exception of a few small areas they don't want to disturb the soil due to wilt.

    Some new growers have joined the group and are doing their first year of cover crops.

    Soil parameters will not be measured this year, as it is expected to take several years for the cover crops to make a significant impact, but will be measured at the end of the project and compared with the baseline data taken at the beginning of the field lab.

    Milestone: Establishment of cover crops Year 2

    September 2018

    Second year cover crops drilled

    Two triallists have got their cover crops in early (one before harvesting the hops) so they feel that there should be a better establishment than last year. The triallist who drilled before harvest hopes that as the seed is already in the ground waiting to emerge, as soon as the hops are harvested there will be light and more warmth than usual for them to establish much better. The triallists will be recording their observations and taking photos of emergence in order to reflect on these alongside the soil health analysis.

    A new triallist has also joined the group after seeing the first year of methods rolled out.

    After discussions with the researcher last November, the triallists won't be taking yield data as they don't feel this will be able to tell them clearly if the cover crops have had a beneficial effect. There are too many other confounding factors upon yield, such as rainfall, temperature and mildew.

    The group's plan is take soil health measurements again in November 2019, by which time they hope that there are some significant improvements to compare against November 2017 results. They will be meeting later in autumn to verify these plans with the researcher.

    Milestone: Second year cover crops drilled

    July 2018

    Harvest update

    The hop harvest is normally around the August bank holiday but the coordinator thinks that this will probably be a few days earlier this year due to the dry weather.

    The farmers have discussed about potentially drilling in a few of the cover crops before harvest. This wasn’t thought of as a possibility due to the ground being so dry but over the weekend they have had 20 ml of rain in Kent so potentially now possible. Despite this, the farmers plan to drill the majority of the cover crops after hop harvest.

    Milestone: Harvest

    May 2018

    Trial presentation

    Triallist coordinator Rob Saunders gave a presentation about the scope of the trial, including photos from one of the more 'light touch' triallists (growing cover crops but not taking measurements), which shows that their growth is very encouraging.

    Some of the triallists also took part in a panel session at the Innovative Farmers Network Day in May, to explain that in comparison to other research grants this had been much easier to access, and the support from researchers has been positive.

    Milestone: Progress meeting

    February 2018

    Initial lessons from the first year

    From the first year of cover cropping the group has realised a few initial lessons that can be built upon in subsequent years. These include upping the seed rate and creating a better seed bed for good cover crop establishment. The drilling of the cover crop needs to done quicker i.e. earlier in the season, so that there is less time between harvest and drilling. Next Autumn they will also look to cover a wider area with the cover crops at each farm.

    Milestone: First year reflections

    February 2018

    Cover crop termination

    Termination of the cover crops will be undertaken during late February, early March using the method of choice for each farmer, (the majority will be glyphosate this year with the hope in subsequent years the group will use other approaches such as Crimper roller).

    Milestone: Cover crop termination

    November 2017

    Baseline data collection

    The two Kent trial sites have undertaken their baseline data collection. The data recorded included a visual assessment of the soil, pH profiles, earthworm counts and SOM measurements. In December the two Hereford trial sites will undertake baseline data collection. These initial sets of data will be available online in the new year.

    Milestone: Baseline data collection

    October 2017

    Confirmation of soil measurements

    The group decided that the following soil parameters will be measured:
    • Earthworm counts
    • Water infiltration rate
    • Visual evaluation of soil structure
    • OM content
    • Soil Mineral Nitrogen content
    • Solvita test (CO2 release as an indicator of biological activity) - if practical

    Milestone: Methods discussed & finalised

    September 2017


    The proposed method is to measure relevant soil parameters – water infiltration rate, earthworm population, OM content & soil mineral nitrogen content, to establish a baseline, then areas of cover crops in alleyways, carry out follow-up evaluations to identify effects in the spring, and share best practice.

    Cover Crop Options
    A number of parameters must be met by any candidate cover crops:
    • Suitable for late summer/autumn sowing
    • Easy to establish, tolerant of ‘poor’ seedbeds
    • Fast growing
    • Easy to kill, or manage in such a way that it does not, in itself, become a problematic weed.
    • Ideally, exerts allelopathy, thereby reducing the germination of other weeds.
    • Mixed stands may be more successful and resistant to pest and disease than single species.

    In gardens where wilt-susceptible varieties are grown, the cover crop must not become a reservoir or nursery for wilt. Further research and consultation are needed, but this may restrict the options to monocots.

    • Rye: excellent leaching prevention, useful OM useful soil structure improvement.
    • Black Oat: excellent leaching prevention, excellent OM, excellent soil structure improvement
    • Rye/Black Oat mix

    In less wilt susceptible varieties, the list of candidate plants is potentially less restricted.

    Candidate plants as above, plus:
    • Buckwheat: excellent OM, not frost hardy so ‘self-destructs’, said to promote P availability.
    • Rye/Vetch/Phacelia mix: useful leaching reduction, excellent OM, useful soil structure improvement.
    • Black Oat/Vetch mix
    • Rye/Vetch mix
    • Rye/Mustard mix

    Crop Destruction Options:
    • Leave to degrade
    • Spray off in spring
    • Spray off and roll flat / roll flat and spray off (a ‘bracken roller’ with serrations to promote bruising and breakdown) may be advantageous). This approach is preferred as it potentially promotes/preserves allelopathy (inhibition of weed germination).
    • Spray off and cultivate (least preferred as promotes breakdown of OM and creates a new weed seedbed).

    Milestone: Methods discussed & finalised

    September 2017

    Drilling of the cover crops

    The cover crops have been sown after harvest in alternative rows to help avoid any soil cooling effects of the cover crop in Spring which may affect soil health.

    After drilling the farmers have concluded future cover crops need higher seed rates and the two Kent sites have expressed their desire to sown their cover crops just before hop harvest (August) next year.

    Milestone: Crops drilled

    August 2017

    Trial methods

    There will be three tiers to this farming group and field lab:
    • Primary Hosts: 4 ‘full evaluation’ sites where changes to all relevant soil parameters will be measured during the course of the field lab.
    • Additional Hosts: ‘light touch’, ‘observation’ sites where growers will establish and manage various mixes according to their own requirements, sharing their experiences but not taking detailed data beyond what is practical for them.
    • Observers: the remainder of the group will follow the trials and learn from the outcomes at regular meetings.

    Milestone: Methods discussed & finalised

    August 2017

    Initial meeting consultation

    Discussion with Hop specialists regarding which cover crops to use within the trials.

    The specialists expressed that, depending on the cover crops used, there could be a risk of increasing verticillium wilt in the following Hop crops. Following consultation the trial farmers have chosen to use a cereal monoculutre cover crop this year, including forage rye, triticale and oats.

    Milestone: Initial idea formation

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