Barley-legumes companion cropping for continuous grain and soil health

Project Description for Find-A-PhD Advert (max 400 words). This will be the text that is advertised to prospective students:

Grain production faces significant challenges associated with soil degradation and an over reliance on the use of synthetic nitrogen (N) fertilisers, of which prices have risen significantly in 2022 (+171% for ammonia nitrate). This poses a considerable challenge: how to maintain yields while simultaneously improving soil health and reducing the input of inorganic nitrogen.

Therefore, a paradigm change, from outsourcing and high inputs to harnessing natural processes in farming systems is required.

Regenerative agriculture proposes to rebuild soil health, introducing "restorative crops" such as cover-crops, and resting the soil under pasture. However, the establishment of cover-crops after harvesting (small temporal-window) and their suppression before sowing are major challenges. In particular, the use of herbicide to clear cover-crops must be addressed in the light of environmental/health risks and potential future restrictions on their use.

Similarly, mixed farming (soil recovery under pasture) limits grain production to few years in the rotation and contradicts the reduction-target in ruminants for climate mitigation.

To overcome the limitations of both conventional (high inputs) and regenerative (unproductive soil resting) agriculture, Restorative Continuous Grain Cropping (RCGC), based on under-sowing cereal crops with short herbaceous-legumes, has recently been proposed for cereal production (e.g., heritage wheat for distilleries). In RCGC, herbaceous-legumes understory has the potential to reduce the requirement of N-inputs and herbicide application by biological N-fixation and over-competing weeds, as well as to limit erosion by continuous soil cover.

Moreover, it can be hypothesized that greater root density and diversity in RCGC may restore soil health and reduce the yield penalty in the transition to a no-tillage system (i.e., fast rebuilding of soil structure). Despite its potential to deliver sustainable cereal production, RCGC is based on complex and variable processes (e.g., inter-species facilitation/competition; soil-structure formation) and lack investigation.

Working with controlled-environment and field experiments, this project aims to understand and quantify the benefits of RCGC and implement its design to improve the resilience and sustainability of barley crop production, as well as mitigate impacts of climate and environmental change. Different legumes (crops and native species) will be grown with different heritage and elite barley varieties of major interest for UK malting sector, to identify optimal companion-cropping systems.

Furthermore, both soil and crop management will be evaluated (e.g., sowing time) to maximise benefits and minimise any negative interaction in companion cropping (e.g., barley-legume competition). Taking advantage on the diverse project team, including experts in soil scientists, plant physiology and microbiology, the project will embrace a holistic system approach and support student-development in different academic fields.