Fertilisers in the Environment – Seventeenth Francis New Memorial Lecture

Keywords: Fertilisers, Environment, Pollution.

CONCLUSION:

The environmental aspect of fertiliser use is confused and complex. The decision on the importance of any one issue is influenced by opinion, partisan interest and appreciation of risk and hazard. It is useful to distinguish between the effects of fertilisers on the ‘environment’ in a strict sense, and on human health. The former could almost certainly be dealt with effectively by the extension of the various administrative measures that already exist for the protection of the countryside. However, marine nitrate pollution may be less easily dealt with. The issue of organically grown food I do not address at all, because it is not an environmental problem in a strict sense, but rather one of perception of food quality.

The most immediate and explosive issue is quite certainly the health implications of nitrate in water. Even though the health hazard in any situation is very difficult to quantify – if indeed it exists at all – there is as yet little public understanding of the impossibility of avoiding all risk. The 50 mg/litre NO₃ limit is likely to remain, and the fertiliser and agricultural industry could probably accept this if it were applied to the water supply only, so that blending and treatment were acceptable. It is indeed difficult to see why sources should be below the chosen level all the time. It is therefore the marginal interpretation of the danger, rather than the 50 mg NO₃ /litre itself, which causes such problems. The full and strict interpretation of the draft EC Directive seems over-cautious, to say the least, and it is generally accepted that it would cause almost insuperable problems for agriculture in the Eastern part of the UK and elsewhere in Europe. Fortunately, there are indications that this position may be relaxed.

I find it difficult to visualise ways in which we could handle anything like the present amounts of fertiliser nitrogen without exceeding the 50 mg/litre limit in the drier parts of the country. The inaccuracy of farming operations, the unpredictability of weather, and the variability of soils pose apparently insuperable obstacles to complete success, though considerably better control than at present is certainly possible.

The problems that are in the ascendant relate to the composition of the atmosphere. The large amount of ammonia produced from agricultural operations is becoming the dominant quantity in nitrogen deposition. The release of nitrous oxide is likely to receive steadily greater attention, especially if an international convention on greenhouse gases is developed, and is likely to prove a very difficult problem in due course.

At present, there is little doubt that the fertiliser industry feels itself beleaguered by these environmental complaints, and it feels aggrieved that praise for the productivity gains from fertilisers should so soon have been replaced by criticism. I believe that if the industry analyses this criticism with care, and separates the genuine from the false, it can come to terms with most of its critics, and show the rest to be unreasonable. The result will in any event be a limit to fertiliser use in agriculture. The problem is to find where that stable limit lies.

Dr P B Tinker, Natural Environment Research Council (NERC), Terrestrial and Freshwater Sciences, Swindon, UK.

24 pages, 5 figures, 5 tables, 43 references.