PhD Studentship: Biochar for Soil Health to Boost the Environmental Sustainability of British Hop Production

Applications are invited for this full-time PhD studentship, which for UK home students is fully funded* by the Worshipful Company of Brewers, Asahi, Sainsbury’s, and the Royal Agricultural University.

Background

The UK is aiming to achieve net zero for agriculture by 2040 (NFU). Whilst this is a challenging goal, it presents numerous opportunities for farmers and land managers to not only directly reduce their greenhouse gas emissions, but also engage with actions that will result in greater carbon storage on land.

The management of British hop yards is focussed on overriding concerns with Verticillium Wilt (VW) due to its potential to decimate production, but also yield impacts due to competition from vegetation growing in alleyways between rows of hop bines. As the incidence of VW can be increased through the presence of vegetation in alleyways, growers prefer to maintain alleyways as bare soil throughout the year, which in turn impacts soil health. Regular cultivation and the use of herbicides to keep alleyways bare not only releases soil carbon, it is also carbon intensive.

Good soil health is one of the first lines of defence against soil-borne plant pathogens (Nwokolo et al., 2021), and as such, actions to reduce the incidence of VW in hop yards through vegetation removal can reduce the soil’s capacity to protect against financially important pathogens like VW (Ahmed & Galaup, 2022). Hop growers therefore need to focus on improving and maintaining soil health, especially with regards to the microbial community.

The value of biochar in improving soil health has been demonstrated in a range of crop types although responses are not always consistent (Lévesque et al., 2022). The benefits include more diverse microbial communities (Jenkins et al. 2016) and therefore an increased potential to suppress soil-borne pathogens (Poveda et al., 2021), improvements in nutrient and water retention (Baronti et al., 2014), and more carbon being locked up in the soil (Vaccari et al., 2011).

Biochar can also be used for the remediation of soils contaminated with heavy metals (O’Connor et al., 2018; Gonzaga et al. 2022). This is especially relevant in the case of UK hop yards, where the top soil is often contaminated from the long-term use of copper-based fungicide sprays for downy mildew prevention and control, negatively impacting soil health and plant growth (Görl, et al., 2023). However, the benefits of biochar to support a more sustainable approach to hop production is yet to be explored in this context.

There are only 45 hop growers remaining in the UK, and the hops they produce are highly sought after, enabling producers to differentiate their beers using unique flavours and aromas. To help underpin this sector there is a need to support hop growers with research that will enable them to increase the resilience and viability of their businesses, whilst enabling them to meet sustainability goals.

The opportunity for hop growers to utilise the benefits of biochar is likely to be a game changer for the sector and therefore demands being investigated. Through a programme of controlled pot-based studies and field trials, the overall aim of this project it to investigate whether the application of biochar has the potential to improve soil health and suppress soil-borne plant pathogens (including Verticillium spp.), whilst also boosting carbon storage. A key aim is to provide robust management guidelines for hop growers. This will be achieved through the following objectives.

1. Under controlled conditions (glasshouse), investigate the effect of different types of biochar and application rates on the growth of a commercially important hop variety ‘Fuggle’.
2. Under controlled glasshouse conditions, investigate the efficacy of different types of biochar and application rates to suppress Verticillium spp. in hops.
3. Apply biochar to alleyways in British hop yards and investigate the benefits/impacts on the performance of hop bines.
4. Determine the efficacy of biochar in British hop yards to enhance soil health and suppress soil-borne plant pathogens.
5. Determine the potential for biochar to increase soil carbon storage in the alleyways of hop yards, and its contribution to net zero farming.

Indicative methodology

At the University of Warwick, a pot-based glasshouse experiment will be undertaken to investigate the influence of a range different biochar types and amendment levels on VW disease development on hop bines. The performance of bines under the different biochar regimes will also be investigated to help inform the most beneficial biochar type and its application rate in the field.

Following the glasshouse study, working with the British Hop Association and Charles Faram & Co Ltd, field sites will be selected for study in Gloucestershire, Herefordshire, and Worcestershire. At each site three plots spatially separated for independence will be selected controlling for factors such as hop variety, age etc. One plot will be managed conventionally with alleyways being left bare, one will receive biochar applications only in year one, and one plot will receive biochar in two consecutive years. The best biochar type and application rate identified during the pot-based glasshouse will be applied to alleyway strips.

For the glasshouse study, effects of the different types and amendment levels of biochar on VW disease development will be evaluated by recording disease symptom development over time (yellowing, wilting, plant mortality), while at harvest (at a time when untreated control plants have a high disease incidence), roots and stems will also be assessed for presence of VW disease symptoms. Re-isolation of V. nonalfalfae will be attempted for selected plants to confirm infection. Additionally, at harvest, fresh and dry weight of plants from each treatment will be recorded to determine any stunting effects of VW in inoculated treatments and any effects of biochar on hop growth in uninoculated controls.

Yields of hops will be compared between treatments to investigate whether the addition of biochar influences productivity. At each field site, the number and weight of hop cones from randomly selected bines will be determined for each of the three treatments.