Grass margins as buffer strips

Grass margins as buffer strips

Maintaining a network of grass buffer strips and other wildlife-friendly margins around arable fields and ponds will provide vital terrestrial habitat for many species.

What

Margins next to watercourses buffer them from farm inputs and surface run-off and help to ensure compliance with legal obligations.

These buffer strips are the last line of defence where other measures to prevent soil erosion and run-off have not been successful: consider soil management, crop rotations, winter cover crops and in-field grass areas to further protect soils and water.

 

buffer next to watercourse 2 R Winspear

Why

Tussocky grass margins provide essential over-wintering habitat for many welcome insects and spiders, which will feed on crop pests in the spring. They are also used by grasshoppers, sawflies and other insects that provide chick food for birds such as partridges, tree sparrows and reed buntings. Grass margins also provide useful terrestrial habitat for amphibians and reptiles for feeding, shelter and migration, and can provide connectivity in the landscape allowing wildlife to move through it.

Floristically-enhanced grass margins can provide greater plant species diversity and provide a rich source of nectar and pollen for a variety of invertebrate species.

Populations of small mammals, 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.

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 field boundaries with no hedgerows.

A 6m buffer strip next to watercourse means that a Local Environmental Risk Assessment for Pesticides (LERAP) is not required when applying pesticides. It protects the watercourse from input applications and can filter out sediment from surface run-off before it enters the watercourse.

Harvest mouse Micromys minutus, adult in vegetation, Hertfordshire, August, (captive)

How

It is important to establish whether or not a grass margin is the most appropriate option. In areas where there may be scarce arable plants it is better to create uncropped cultivated margins to encourage arable plants. This will also determine whether to establish a grass margin by sowing or natural regeneration. Sown grass margins can also be enhanced with more competitive wildflowers to provide forage for pollinators.

Creation

To benefit wildlife, select a location that links habitats or that is next to a watercourse, hedgerows (especially those with mature trees), adjacent to remnants of trees on former boundary lines, near groups of trees in fields and along a woodland edge.

Check for the presence of scarce arable plants – these require regular cultivation and are lost if a permanent grass sward is created. Where these occur, consider using uncropped cultivated margins as an alternative.

Assess whether the margin can be established by natural regeneration: if the seedbank contains perennial grasses and wildflowers and low levels of pernicious weeds such as blackgrass, brome and cleavers, then this would provide a cheap and often more valuable wildlife habitat.

Autumn (August/September) is the best time to establish grass margins. A higher seed rate will be needed if sowing in spring. Spray a heavy weed burden with an appropriate herbicide before cultivation.

Mixes should be discussed with a local seed merchant to ensure the mixtures are appropriate for the local soil conditions. Up to 10% of cocksfoot or timothy grass in the mix will create a thick sward ideal for trapping sediment in surface run-off, providing nesting cover and protecting over-wintering insects. The mix should also include fine grasses such as fescues and bents.

In the first summer, cutting the sward when it is 10cm tall will help to control weeds and encourage grasses to tiller. This may require three cuts. Removing the cut vegetation is desirable where this is possible, as swaths of cut grass lying on top of the sward suppress establishing plants. If possible, piling up cuttings away from sensitive areas to decompose can be useful egg-laying sites for grass snakes; such features are often limiting for the species and are therefore particularly valuable.

To deliver greater benefit for pollinators and pest predators, consider enhancing grass mixes by seeding with flowering plants such as knapweeds, selfheal, yarrow, ox-eye daisy, lady's bedstraw, bird's foot trefoil, wild carrot and sainfoin. Low fertility soils with a low P index (below 2) are most suitable for this option.

To maximise benefits for watercourse protection, create the buffer strip alongside the watercourse or across the slope on long steep slopes to intercept run-off. For watercourse protection, spreading the buffers across all down slope edges of fields will have a greater benefit than a single localised wide buffer.

Management

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.

Avoid herbicides and fertiliser drifting into the margin as it will benefit competitive weeds over perennial grasses. Insecticide drift harms any beneficial insects supported by the field margin.

Treat any noxious weeds with an appropriate herbicide as soon as possible to avoid them becoming established. You may prefer to 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 should not be necessary. Where you use such strips, they should be positioned between the grass margin and the crop.

Mowing will provide space and light for less competitive species, it also provides a practical and low cost method of management.

Cut margins once every three years, after the first year, and only in the autumn.  Avoid cutting all of the margins during the same year, instead cutting on rotation around the farm or in thirds within a large margin so that there are plenty of rough areas with seed heads through the winter for hibernating insects.

Ideally cuttings should be removed to reduce impact upon less competitive species and prevent increased soil fertility. Avoid cutting when the soil is moist to prevent compaction.

Grass margin Richard Winspear

In practice

Here are some useful case studies and articles about how farmers are putting Farm Wildlife into practice on their farms

Case Study: Establishing a nectar mix on chalk in the Yorkshire Wolds

By Kathryn Smith | 2nd September 2013

Author: Chris Tomson Farm: Towthorpe Manor Farm Aims: Towthorpe Manor Farm is a 242ha arable farm with chalk dales grazed with native breed cattle. There is a small shoot with cover crops of mustard and triticale privately funded. Winter cropping includes oilseed rape, winter wheat, winter barley and oats for Jordans. Spring beans are also […]

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Case Study: Buffer strips on intensive grassland

By Kathryn Smith | 4th July 2013

Author: Robert Kynaston Farm: Great Wollaston Farm, Shropshire Aims: Two and six metre grass margins have been established in fields with arable cropping as part of the rotation. Margins were established for a number of reasons: – Buffer water courses with 6m margins to meet LERAP requirements – Buffer hedgerows and hedgerow trees to develop wide […]

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