A comparison of agricultural water pollution incidents in Northern Ireland with those in England and Wales

Agricultural pollution incidents in Northern Ireland declined by 51% between 1987 and 1995. This decline resulted from a steady decrease in the largest category of farm pollution, silage effluent, which declined by 78%. The decline in silage pollution was most evident in the months of May and June and may be related to an observed increase in grass wilting, which reduces silage effluent volumes, and favourable weather during these months. Non-silage related incidents were 49% greater in 1995 than in 1987 and showed no particular trend with time nor the distinct annual cycle that was observed for silage pollution. Silage effluent represented 51% of all pollution sources, followed by a general category of farm effluent (27%) and cattle slurry (12%). No other source contributed more than 4% of the total. An analysis of pollution cases showed that, while incidents associated with leaking and overflowing effluent tanks and leaking silos all declined, incidents where no effluent collection facilities were found increased. This increase was considered to be the result of a change in detection efficiency rather than an absolute increase in the number of farms without effluent collection facilities. Farm pollution statistics from Northern Ireland and England and Wales demonstrated similar trends for both silage and non-silage related incidents, with no evidence to suggest that increases in financial penalties for causing pollution or different levels of grant aid had impacted on long-term trends. Trends in pollution statistics from catchments in Northern Ireland targeted for pollution advice by agriculture advisory staff did not differ from the area as a whole.