BUFFER ZONES TO IMPROVE WATER-QUALITY - A REVIEW OF THEIR POTENTIAL USE IN UK AGRICULTURE

A number of possible measures are being considered by the UK governmen t to control the pollution of surface waters. One possible approach to the problem of reducing pollution from diffuse sources is the establi shment of buffer zones between the pollutant source areas and the rece iving waters. This review assesses the effect of buffer zones, defined as a permanently vegetated area of land which is separately managed f rom the rest of a field or catchment, on the runoff of various agricul tural 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 res earch studies have reported positive effects of buffer zones, particul arly on loads of sediment and P in surface runoff and on the nitrate c ontent of diffuse subsurface flow. The data suggest that benefits coul d be obtained from the wider use of buffer zones. However, especially in clay soils where subsurface drains may provide the major flow pathw ay through riparian areas, it is suggested that the effect on pollutio n 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 t hat further research would be required in order to maximise the potent ial improvements in water quality that buffers could introduce.