Arable field margins
Field margins, although generally the least productive areas of a field, can benefit wildlife in many ways.
Arable field margins
Just a metre wide grass strip between the outer edge of the hedge and the crop edge can benefit wildlife in many ways.
- Select areas carefully to ensure they encourage less competitive arable plants and do not become infested with grass weeds.
- If rare species are present, time the cultivation to suit the germination time of the plants.
- Take steps to prevent the drift of pesticides or fertilisers onto the uncropped areas.
Benefits to wildlife
Grass margins can provide nest sites for ground-nesting birds
A tussocky grass strip against a short, thick hedge provides an ideal habitat for ground-nesting bird species such as grey partridges, whitethroats and yellowhammers. Corn buntings may use the same kind of strip alongside hedgeless field boundaries.
Grass margins boost numbers of beneficial insects and spiders on arable farmland
Tussocky grass margins provide essential over-wintering habitat for many welcome insects and spiders, who then feed on crop pests in the spring. They are also used by grasshoppers, sawflies and other insects which provide chick food for birds such as partridges, tree sparrows and reed buntings.
Wild flower strips attract nectar-feeding insects, such as bumble bees, and hoverflies, which lay their eggs where there is an abundant supply of aphids for the larvae to feed on.
Grass margins provide habitat for small mammals
Small mammal populations, such as voles and harvest mice, are able to build up in wide grass margins, providing ideal hunting habitat for barn owls and kestrels. Wide margins away from roadsides can reduce the risk of barn owls being killed by road traffic.
Cultivated margins can help conserve rare arable plant species
Many rare plants are now confined to the edges of arable fields. Careful management of these margins can help them without creating a significant weed burden at the edge of the crop. Cultivated margins on light soils with low fertility can provide seeds for farmland birds. Choose sites carefully to prevent infestations of noxious weeds.
How to create grass margins
The best time to establish grass margins is in autumn, during August and September. If sowing in spring, you will need to use a higher seed rate.
- If a perennial grass sward will develop, leave an area to regenerate naturally, otherwise drill a native seed mix.
- Spray a heavy weed burden with glyphosate or glufosinate before cultivation.
- Cut the sward when it is 10cm tall in the first summer to control weeds and encourage grasses to tiller, this may require three cuts. Swaths of cut grass lying on top of the sward may suppress perennial grasses.
- Avoid herbicides and fertiliser drifting into the margin as these will benefit competitive weeds over perennial grasses. Insecticide drift harms any beneficial insects supported by the field margin.
- Treat barren brome in the grass margin selectively with an application of fluazifop-P-butyl in November (most perennial grasses will recover from this treatment).
- Retain the grass margins and apply no fertiliser when a grass ley forms part of the arable rotation.
- Ideally avoid grazing the margins from March to August.
How to create and manage buffer strips on cultivated land margins. PDF, 132KbBuffer strips on cultivated land advisory sheet (England)
How to manage rough grass margins. PDF, 185KbRough grass margins advisory sheet (Northern Ireland)
How to introduce and manage arable crops. PDF, 207KbArable field margins advisory sheet (Wales)
How to create and manage arable field margins. PDF, 264KbArable field margins advisory sheet (Scotland)
Types of grass margin
Different grass types affect how grass margins work - the tussocky type helps ground-nesting birds and the wild flower type attracts nectar-feeding insects.
You can leave a sterile strip around the crop edge to control weeds, although if you establish a perennial grass margin between a hedge base and the crop this shouldn't be necessary. Where you use such strips, however, they should be positioned between the grass margin and the crop.
Tussocky grass margins for nesting birds and over-wintering insects
- One to two-metre margins, next to short, thick hedges or boundaries with no hedge at all, provide nesting cover.
- Using up to 30 per cent of cocksfoot or timothy grass in the mix will create a tussocky sward ideal for nesting cover and protection for over-wintering insects. The mix should also include fine grasses such as fescues and bents.
- Cut these margins once every three years after the first year and only in the autumn. Avoid cutting all margins during the same year.
- For six-metre margins, cut the three metres abutting the crop edge annually, but only cut the hedgeside margin every three years - this will create a useful mix of grassland structure.
Wild flower margins to attract nectar-feeding insects
- Create wild flower strips within a six-metre margin in a sunny area. Well-used farm tracks and footpaths are good sites as these areas are disturbed often, making them unsuitable for the tussocky margins that suit nesting birds.
- Use a mix of fine grasses, such as fescues and bents. Wild flower seed should comprise between 5-20 per cent of the mix by weight and include native plants such as yarrow, knapweed and ox-eye daisy.
- Where possible, use a local seed source.
- Drill the grass seed and broadcast the wild flower seed before rolling.
- Cut annually in the autumn.
Cultivated margins for rare arable plants
- This type of management is ideal for sites with rare arable plant species or communities. Grass margins on these sites will suppress the germination of these dwindling populations. These plants need cultivation and protection from herbicides and fertilisers.
- Cultivate the margin annually and leave it to regenerate without broad-spectrum herbicides or fertiliser. The germination time of the key plant species present will dictate the cultivation time.
- This type of management can give farmland birds a summer seed source on sites where resultant weeds won't affect the adjacent crop (such as on light, low nutrient soils).