Two pilot schemes to curb nitrate leaching were established by the Ministry of Agriculture, Fisheries and Food (MAFF) in 1990 (ENDS Report 183, pp 29-30). They were a belated response to a requirement imposed by EC legislation in 1980 to keep nitrate levels in drinking water below 50mg/l.
Ten Nitrate Sensitive Areas (NSAs) were established in England to test farming practices designed to reduce nitrate leaching, and also to gauge whether farmers would adopt such measures voluntarily in return for financial compensation.
In parallel, Nitrate Advisory Areas (NAAs) were established over a larger area totalling 16,000 hectares. Farmers in the NAAs are offered free advice on how to reduce nitrate leaching without cost to their businesses. No compensation is paid.
The first results of the impact of the two schemes were reported by Michael Madden, Under Secretary on Environmental Policy at MAFF, at a conference on land use policy in water catchments at Silsoe College in April.
According to Mr Madden, a "significant minority" of farmers are still applying excessive fertiliser. More than 20% of the land in the NAAs is receiving nitrogen inputs above the optimum for the crop under cultivation. For potatoes, only 25% of the land area received the optimum level of nitrogen or less. Another 33% received up to an extra 30kg/ha, while more than 20% received an excess of over 90kg/ha.
Many farmers participating in both schemes are also failing to allow for the nitrogen content of manures and sewage sludge when calculating how much artificial fertiliser to apply. This is leading to "huge nitrate leaching losses", Mr Madden said. Measurements made by porous pot lysimeters have showed nitrate concentrations in soil water way above the EC limit for drinking water (see table ).
Farmers are wasting money on over-fertilisation, Mr Madden concluded. Studies in the NAAs showed that 70% had not calibrated their fertiliser spreaders - a situation which MAFF believes is replicated throughout the country.
The findings are likely to be worrying the Government as it prepares to implement the 1991 EC Directive on nitrate in water (ENDS Report 205, p 35 ). The legislation obliges Member States to introduce a voluntary code of good agricultural practice aimed at protecting all waters from nitrate contamination, and to introduce stricter controls on nitrogen inputs in "vulnerable zones" draining into waters where the 50mg/l limit is, or is at risk of, being exceeded.
"Possibly as much as two million hectares" in England and Wales, or about one-sixth of the area of agricultural land, will be designated as "vulnerable zones", said Mr Madden. This is much less than in Germany and the Netherlands, which are expected to place all their farmland in this category, and in France, where one-third of the agricultural area is likely to be designated.
Whatever the UK's final figure, farmers will have to make a greater success of the voluntary approach if those operating in "vulnerable zones" are to avoid tougher measures.