Weeds can provide clues about soil conditions, from nutrient availability and pH to compaction, drainage and organic matter. Weeds as Bioindicators: A Farmer’s Field Guide, developed by Chris Maughan and Dominic Amos at the Centre for Agroecology, Water and Resilience (CAWR), presents a practical approach for farmers and growers in the British Isles to use non-crop plant communities as an additional source of information for assessing soil health.

The guide sets out a participatory field methodology that combines plant identification, estimates of ground cover, interpretation of bioindicator species and visual soil assessment. Participants first record the non-crop plants present across a field, then estimate their abundance at 10 sampling points. The five most abundant species are assessed using a scoring system, and their associated soil indications are combined to identify patterns that warrant further investigation. The guide recommends comparing these indications with direct observations of soil structure, using the Visual Evaluation of Soil Structure (VESS) method, and repeating surveys in spring, summer and at harvest to monitor changes over time.

Inspired by the work of French botanist Gérard Ducerf and adapted through a participatory study with farmers in June 2021, the resource includes botanical survey sheets, an analysis template and a species guide covering common non-crop plants and their possible associations with soil properties. It presents bioindicators as a relatively accessible and low-cost complement to other assessment methods, supporting farmer knowledge-sharing and longer-term monitoring of soil management practices.