Buffer zones to improve water quality: a review of their potential use in UK agriculture

Abstract

A number of possible measures are being considered by the UK government to control the pollution of surface waters. One possible approach to the problem of reducing pollution from diffuse sources is the establishment of buffer zones between the pollutant source areas and the receiving waters. This review assesses the effect of buffer zones, defined as a permanently vegetated area of land which is separately managed from the rest of a field or catchment, on the runoff of various agricultural pollutants. The effectiveness of buffer zones for the retention of nitrogen (N), phosphorus (P) and pesticides varies according to the mechanisms by which these pollutants are transported. A number of research studies have reported positive effects of buffer zones, particularly on loads of sediment and P in surface runoff and on the nitrate content of diffuse subsurface flow. The data suggest that benefits could be obtained from the wider use of buffer zones. However, especially in clay soils where subsurface drains may provide the major flow pathway through riparian areas, it is suggested that the effect on pollution will be minimal unless some additional measures are undertaken. The review has also identified that knowledge on the potential effects of buffer zones appears to be limited in a number of critical areas and that further research would be required in order to maximise the potential improvements in water quality that buffers could introduce.