Increasing the value of silvoarable agroforestry using understory crops in the tree rows

ilvoarable agroforestry is gaining recognition as an innovative method to address the biodiversity and climate crises. It involves integrating tree rows (commonly fruit, nut or timber trees) through arable fields. Compared to arable farming, this increases structural complexity, plant diversity, and carbon sequestration, which can promote pest control, pollination, soil health, and food production. For example, a UK study found 10 and 4.5 times greater bee diversity and fruit set in silvoarable vs arable sites. Silvoarable systems can also be more resilient to climate-induced extreme weather due to enhanced microclimatic buffering, biodiversity, and soil health.

Recognising this, the UK government made a statutory commitment to increase silvoarable area more than tenfold by 2050, an increase that is 55% the size of Wales . From 2024, farmers will be paid to adopt silvoarable farming by DEFRA's new agricultural schemes and private sector (e.g. construction) payments to meet biodiversity net-gain regulation. These schemes mirror growing interest globally, including from the European Commission. Therefore, silvoarable research can contribute directly into emerging policy and markets.

However, significant knowledge gaps remain for silvoarable systems, and identifying best management of the tree row understory (e.g. species, width) is an urgent priority for UK stakeholders [5]. Tree rows can use 25% of the field area depending on planting arrangement, with understories mostly under natural regeneration or flower planting. Planting can promote pest control and pollination, or arable weeds if poorly managed [6,7]. We propose that further benefits to biodiversity, ecosystem services, production, and profits could be achieved by planting the row understory with high value crops, such as herbs, mushrooms, or perennial vegetables or fruits (e.g. berries). We have found one study that tested this in the UK with cut flowers and rhubarb [5]; it showed that crops could help to offset establishment costs, a primary barrier to silvoarable adoption.
Silvoarable tree row understory could increase by 285,000 ha in England by 2050 according to tree planting targets. Maximising its potential value is therefore urgent.

Hypothesis
Designing silvoarable systems with understory crops can provide production, profitability and environmental benefits, and a pathway to overcome prohibitive establishment costs.

Objectives
1. Create a longlist of potential UK silvoarable understory crops and quantify their likely (dis)benefits to production, biodiversity, ecosystem functioning, profits, and farm management (e.g. labour) in different contexts (e.g. soil, canopy cover) through a systematic review on temperate understory crops and expert interviews (e.g. farmers, suppliers).
2. Test up to eight understory crops vs natural regeneration over a two-year replicated field trial across the University of Reading's network of young and mature silvoarable systems. Select crops from the longlist with farmer and researcher input and measure biodiversity (e.g. pollinators), ecosystem functions (e.g. pest damage), yield (understory and adjacent crops), profits, and management impacts, with specific measures determined following the final crop selection.
3. Disseminate findings to the scientific community, the farming industry, and policy makers via high-impact publications, reports, conferences, and various media.
4. Contribute to agroforestry policy design via a 3-6 month placement with the Department for Environment, Food, and Rural Affairs (DEFRA), co-funders of this studentship.
Outcomes
This study will enhance food security by increasing and diversifying food production in silvoarable systems. Silvoarable agroforestry provides many environmental and production benefits, and this study will promote its uptake by identifying pathways to offset establishment costs, which are a primary barrier to adoption