Agronomic and ecological costs and benefits of set-aside in England

摘要

Around 11% of arable land in England was set-aside in the mid-1990s as part of the Common Agricultural Policy (CAP). The scheme allowed both annual and longer-term exclusion from cropping. The most widespread green cover was natural regeneration, followed by non-food crops and sown grass covers. Impacts of set-aside management on agronomy and ecology were investigated using a questionnaire for farmers and field studies of plants, invertebrates and breeding birds on up to 200 set-aside fields, half rotational and half non-rotational. More detailed studies were conducted on crop diseases, vegetation dynamics and breeding birds. Plant species diversity on set-aside was greater in the west of England than in the east, and, on non-rotational naturally-regenerated set-aside, plant communities became increasingly dominated by grassland species with age. Gradients of powdery mildew and septoria leaf blotch infection levels were observed within cereal fields adjacent to rotational set-aside. Invertebrate pest species were more frequent in crops than in neighbouring set-aside, regardless of type. All groups of birds studied were found least on winter cereals, and most were found preferentially on rotational set-aside. Set-aside (especially rotational) has provided suitable habitats for breeding birds over very large areas, and may have helped to compensate for other changes in the farmed landscape detrimental to birds, without causing major agronomic problems. It is important that any scheme replacing set-aside should be over large enough total areas so that the benefits to farmland birds across landscapes ate not reduced.