Herbal ley mixes for natural flood management

Summary

Four farmers are investigating whether creating a bespoke herbal ley mix can help reduce flooding in their catchment. They want to test whether water infiltration and storage capacity can be improved in their soil by incorporating a higher percentage of deeper rooting species into the seed mix.

The Wyre Rivers Trust will coordinate the project and the Field Lab will compliment Brock and Calder Landscape Recovery (BCLR) led by Wyre Rivers Trust and its partners.

It is hoped that farmers will also see other benefits from the bespoke mixes, including improvements to their productivity through better drought resilience, potentially extending the grazing season and offering opportunities for them to partake natural flood management schemes.

Background

Most Natural Flood Management schemes tend to focus on field margins and water courses, for example, encouraging riparian tree planting and creating bunds or scrapes.  There is limited focus on field scale management such as manipulating herbal ley species composition for reducing flooding, probably because there is very limited research on the topic.

However some evidence suggests that manipulating species composition to include a greater proportion of deeper rooting species can alter and increase soil-hydrological functions, thereby allowing more water to infiltrate the soil and increase water storage capacity. 

Trial design

Three herbal ley treatments will be tested on each farm:

1. Control; existing grassland,
2. Standard herbal ley seed mix,
3. Enhanced herbal ley seed mix.  

Soil hydrological monitoring will be carried out monthly at each site throughout the two year project. A more comprehensive assessment of soil biological, physical and chemical properties will be taken annually during the growing season.

Data will be analysed to see which soil properties and soil-hydrological functions are significantly affected by the herbal ley treatments. In addition, the annual in-depth analysis will be used to generate a value for soil health using WRT’s soil health model, which gives farmers greater insight in to how their soil performs for a variety of agricultural and environmental outcomes.