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The Perennial Green Manures Project

Trees feeding soil feeding crops


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Ecodyfi is working with local farmers and growers to trial a new technique of crop fertilisation. Perennial green manures are fertilisers made from plant material grown in biodiverse areas of coppice woodland and perennial plantings. Much like the fertility-building clovers and vetches long-used by farmers, nitrogen fixing trees and shrubs such as alder trees and gorse bushes work with bacteria in the soil to convert nitrogen into a form useful to plants.

Using this method, farmers will grow their fertiliser in the form of nitrogen-rich tree leaves which are cut when green and added to cropland. These fertiliser-producing areas will be situated on less productive areas of farms such as steep slopes or boggy ground. They will  also serve as biodiversity reserves and build up carbon stores in roots and soil. It is hoped that the technique will help farmers meet some of the many challenges they are facing, include fast-rising fertiliser costs alongside the need to increase tree cover for habitat restoration and carbon sequestration.

Initial work at Bangor University has given promising results in scientifically controlled and monitored experiments. These include lower greenhouse gas emissions from soil fertilised with alder leaves compared to that fertilised with manufactured fertilisers and traditional clover green manure. The next step is to trial the technique on crops on working farms. Here in the Dyfi Valley there is a growing trend towards re-establishing the cereal and vegetable growing which has historically been part of our agricultural landscape.  ( Ecodyfi has to recruited some of these local producers to trial perennial green manures in comparison to their usual method of fertilisation.

We are teaming up with growers through the Innovative Farmers program to run a perennial green manures (PGM) field lab.

Here we hope to scale up the trials to see whether PGMs are a viable way for commercial producers to fertilise their crops.

If you're interested in taking part in the field lab, or would like to give feedback, please fill in the questionnaire.

Plant species which could be used in the trials include nitrogen fixing trees and shrubs such as alder, broom and laburnum, and perennials including alfalfa, lupins and vetches. Other plants which scavenge the ground for nutrients such as comfrey and willow can also be included, as inter-cropping these with nitrogen fixers maximises efficiency.

The project began in summer 2022. Ecodyfi will identify farmers and growers who want to use perennial green manures to fertilise their own crops, and design bespoke trials with them. The trials will began in spring 2023 and the results obtained - including comparative crop yields and testimony of farmer’s experiences - will be made available to other growers. In winter 2023/4 the participating farms will be funded to plant their own perennial green manures for future use. These will be designed and sited for maximum co-benefits to the farm, for example to act as shelter for crops, nectar sources for pollinators, and habitats for birds and insects which control crop pests.

The Perennial Green Manures project is supported by the Carbon Innovation Fund - a partnership between the Co-op and the Co-op Foundation. It supports food and farming projects that are tackling the climate crisis by reducing greenhouse gas emissions.

Aberystwyth University’s Beacon project are working with the project to process the plant leaves to increase the ease of application to cropland.

Contact us

Clo Ward, Project Researcher

Clo is our researcher, designing and running the trials alongside the growers. She has worked in horticulture for 30 years, specialising in fruit and perennial systems and promoting environmental techniques by display gardening, writing and teaching, in and around the Dyfi Valley.
Seeking answers to climate questions in agriculture, she returned to scientific study in 2013, undertaking an MSc in Food Security at Aberystwyth University. This led to a PhD at Bangor University ‘An evaluation of perennial mobile green manures for climate change mitigation in agriculture’ which forms the basis for the PGM project. 

Tilly Gomersall, Project Manager
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Tilly’s role is in coordinating and communicating the project as well as taking part in some of the practical elements. She has been studying for an MSc in Sustainable Food and Natural Resources at the Centre for Alternative Technology where her focus is on soil health and climate change in agriculture. She has a background in market gardening, and sells fresh produce in the Dyfi Valley and seeds through Wales Seed Hub.

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