Grass margins as buffer strips

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.

Finding out what natural flora grows in the area 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 or 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.