Promoting Biodiversity by Optimizing Field Margins

Technical articles

Management of cover crops in arable farming Soil cover Biodiversity

Field margin reseeded with an adapted cover, making it favorable to all wildlife and beneficial insects of these margins. Photo credit: Charles Boutour

A field margin is the vegetation zone between the crop and the adjacent environment: path, road, etc.

Objectives

Well-maintained outer field margins constitute refuge areas for all small wildlife of the plain (insects, birds...) and are essential during the breeding period. These semi-natural elements provide many ecosystem services when managed and protected sustainably : 90% of auxiliaries require a semi-natural habitat at some point in their life cycle.

Source: Hommes et Territoires/Agrifaune

Expected benefits

A functional outer field margin allows the development of reservoirs of beneficial insects favorable to crops. A well-preserved margin does not consist of weeds and therefore does not require mandatory annual maintenance. The risk of contamination of the adjacent cultivated plot is greatly reduced. Besides maintenance cost savings in normal pest pressure years, it is possible to consider reducing insecticide costs.

Expert opinion

"On a 120 ha farm, the average surface area of field margins is about 2 ha. These linear features are essential to the biodiversity of cultivated plains. To reconcile all issues, it is important to manage them appropriately and sustainably." David Granger, Project manager for agriculture, wildlife, and game damage at the French Office for Biodiversity.

What is a functional margin?

• It is composed of perennial, diverse, and nectariferous species while being free of weeds.
• It must be at least 1 meter wide.
• It must be preserved from mechanical and chemical disturbances. Thus, a functional and diverse margin does not require maintenance during the summer period.

Source: Hommes et Territoires/Agrifaune

Methodology

The Agrifaune program has developed diagnostic tools to determine the functionality of field margins in arable farming areas via:

• The Ecobordure tool validated for the southern Paris basin and Armorican massif areas (under validation for other regions of France).
• The typology of field margins in cereal plains.

These two tools determine the ecological status of margins. A management plan is co-constructed with the farmer following this diagnosis to improve margin quality. A margin in "moderate degradation" status means there is a moderately diverse flora and presence of weeds. It is then recommended to manage this margin to destroy weeds before seed set (about 20 cm above ground), thus limiting competition of weeds with wild plants. After a few years, the composition stabilizes and optimizes.

Conversely, a margin in "poor condition" means it is mainly composed of nitrophilous and pioneer plants (weeds). Field margins generally less than one meter wide favor these species. These margins are also unfavorable to biodiversity due to very low floral diversity. For these overly degraded margins, reseeding with a mixture adapted to pedoclimatic conditions should be considered.

The Agrifaune program has developed a mixture of perennial plants for reseeding field margins. It consists of plants from different families: red Fescue, Common bentgrass, Yarrow, Brown knapweed, Oxeye daisy, St John's wort, Ribwort plantain, Alfalfa lupuline... This mixture will remain effective for many years if undisturbed.

Advice

To maintain a good biological status of the margin, avoid any disturbances: soil work drift, fertilization, or treatment are detrimental to its structure and composition.

How to implement this practice on my farm?

To improve the agroecological quality of field margins, work can be done at the farm level or territorial level (municipality or community of municipalities scale). In the latter case, it is beneficial for the project leader to involve the local authority, the departmental hunting federation, the chamber of agriculture, or the departmental hikers' association...

Regulatory limit (orders of April 9, 2018, and April 17, 2020) This type of field margin can be considered effective from 1 meter wide and most often ranges between 1 and 2 meters, the acceptability limit for farmers. However, since the April 9, 2018 order, the minimum width for eligibility of field margins under Ecological Focus Areas (EFA) is 5 m. This French overtransposition is the main obstacle to their implementation.

Ecobordure diagnostic tool and typology of outer field margins

• Training for farmers, technicians from O.S. or C.A. or F.D.C. volunteers: Outer field margin typology training Ecobordure training
• Training contact: Chloé Swiderski, Agroecology study officer at the Hommes et Territoires Association. email: c.swiderski@hommes-et-territoires.asso.fr

Reseeding

• A specific 1.5 m seeder has been developed for reseeding field margins. This seeder is available on request from the partners of the Agrifaune program.

• Contact: Bruno Heckenbenner, National GTNA Machinery Referent. bheckenbenner@chasseurdefrance.com

Seeds

• The Agrifaune field margin seed mix costs about €18 per 100 linear meters (mL): highly effective, very favorable to overall biodiversity, and reasonable impact on production. This mix has been validated for the southern Paris basin and the Champagne chalky region. It is under validation for other regions of France.

Agrifaune mix composition: CLICK HERE

Maintenance

See the page Maintenance of grassland areas.

Further reading

A cover labeled végétal local will ensure that plants are adapted to the auxiliaries of the biogeographical region.

Seeding cost (Agrifaune Field Margin mix) may vary depending on seed type and planting date:

Seed type	Autumn sowing (25 kg/ha)	Spring sowing (20 kg/ha)
Normal: €75/kg	€18 per 100 mL	€15 per 100 mL

Sources

• Cereal growers and biodiversity: A synergy to reaffirm - The technical portal of the OFB

Annexes

1. Redirect Modèle:Pages liées