Image: Peter Thompson
Conservation headlands are headlands of cereal crops that are sprayed selectively to allow small populations of broad-leaved weeds and their associated insects to develop.
Headlands should be chosen carefully to avoid encouraging a flush of highly competitive weeds.
Management involves avoiding the use of broad-leaved herbicides in the crop, and avoiding the use of insecticides after 15 March. There are no restrictions on the use of fungicides or plant growth regulators. Conservation headlands can be funded by some agri-environment schemes.
Conservation headlands allow a sprinkling of broad-leaved plants in the cereal crop margin
Conservation headlands in appropriate places will contain small populations of broad-leaved plants, which have little competitive impact on a crop. This management is ideal for sites with rare arable plant populations, but is also appropriate along field margins in areas with light soils that are unlikely to be infested with highly competitive weeds such as barren brome or cleavers.
Conservation headlands boost insect numbers in the crop margin
Broad-leaved arable plants support a high diversity of insects that do no harm to the crop and, in turn, support populations of predatory insects, which help to control crop pests. Tussocky grass margins provide an ideal over-wintering habitat for many such insects. They move into the crop in the spring and, as a result, need protection from insecticides after 15 March. The overall effect of conservation headland management is to boost the numbers of beneficial insects in the crop margin.
Conservation headlands provide an ideal feeding habitat for partridge chicks and other farmland birds
Many farmland bird species feed their chicks on insects for the first few weeks of life. Grey partridge chicks, in particular, forage on the ground in cereal crops, which give them shelter without being so dense that they impede their movement or soak them in wet weather.
An abundance of insects in the crop margin is essential to the survival of these birds. The seed food may also benefit some species. Other birds that may benefit include turtle dove, tree sparrow, yellowhammer, reed bunting and corn bunting.
Where to site conservation headlands
The ideal location for conservation headlands is alongside tussocky grass margins or beetle banks that provide over-wintering sites for a wide range of insects.
Conservation headland management is most suited to light soils in locations that do not suffer from high weed infestations or problems with cleavers or barren brome.
You should only practise this type of management when the field contains a cereal crop. The aim is to achieve a sprinkling of broad-leaved weeds in the headland and to encourage the insects that live on these.
If you find that an unexpected infestation of weeds develops, and you cannot control this with selective herbicides, then select a more appropriate location in following years.
Managing conservation headlands
The width of a conservation headland can be between 6 and 24 metres. The sprayer boom is switched off when spraying the headland of a cereal crop with any insecticide after 15 March or herbicides that target broad-leaved weeds.
You should check conservation headlands in February/March, and again in May, for any significant weed problems. If cleavers become a problem then they can be selectively treated using amidosulfuron in February or March. If other broad-leaved weeds create a significant problem then you should seek advice from a BASIS trained agronomist and your project officer (if doing this under an agri-environment scheme).
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, however, they should be positioned between the grass margin and the crop.
Reduced fertiliser use within the conservation headland would benefit the less competitive arable plants and reduce the problem of invasive weeds such as cleavers; although it would also incur a further yield loss. This approach is most appropriate on sites that are home to rare arable plants.
Use appropriate sprayer technology and weather conditions to minimise spray drift into conservation headlands.
If necessary, a pre-harvest desiccant can be used to enable harvesting, but wildlife benefits are greater if none is used, especially if the subsequent stubble can be left over winter to provide weed seeds for birds.
Where acceptable weed contamination thresholds are low, conservation headlands may be harvested separately for animal or game feed (or see unharvested option below).
Less competitive arable plants benefit from the exclusion of fertilisers and manure, and this can also reduce the burden of invasive weeds such as cleavers. The more open crop structure also benefits some bird species.
Acceptable sprays for conservation headlands
All plant growth regulators
Cleaver control: amidosulfuron
Grass weed control: tri-allate, diclofop-methyl, difenzoquat, flamprop-m-isopropyl, fenoxaprop-ethyl, fenoxaprop-p-ethyl, tralkoxydim, clodinafop-propargyl
Unharvested Conservation Headlands
Some agri-environment schemes pay for unharvested conservation headlands. Some farmers find these easier to manage as they are paid to leave the crop unharvested. They can be drilled as a cereal headland in the same location each year, even when the interior of the field is a different crop. The added wildlife benefit is the provision of a seed-rich cover crop for seed-eating birds through the winter.
Insecticide use on crop margins
Even where the placement of conservation headlands is inappropriate due to a high weed burden, you may consider leaving margins unsprayed whenever insecticide is used on a cereal crop after 15 March. A reduction in spraying of this type will increase the food available to birds and buffer the insect-rich field margins from the effects of spray drift.
Last updated: 4 September 2009
How to site and manage conservation headlands.
How to manage conservation cereals.