Keywords: Atmosphere, Deposition, Acid rain, Sulphur dioxide, Leaching, Crop responses
Sulphur emissions increased during the industrialisation of Europe, but by the mid-20th century, the adverse effects of sulphur dioxide on human health and direct effects on crop yields had been recognised. After this, the effects of ‘acid rain’ on natural ecosystems were also documented and legislation was further tightened to severely reduce sulphur emissions in the 1990s. Data on sulphur dioxide in air and sulphate in rain from many Western European countries shows that due to emission controls in the last ten years, the concentrations and potential deposition in all countries is becoming smaller and more similar. During this period the amounts of sulphur in deposition have dropped below the requirements of many crops. Recent evidence shows that most arable soils have not stored the anthropogenic sulphur that was deposited in the past, and that leaching is resulting in decreasing soil sulphur status. This, coupled with the earlier change in Europe to low sulphur fertilisers has meant that crop responses to sulphur-containing fertilisers are now becoming common. There is evidence from the UK that the reduction in sulphur emissions is running almost 10 years ahead of schedule and the occurrence of sulphur deficiency is increasing. The rate of development of sulphur deficiency varies amongst European states, and Eastern European countries are at present less likely to respond. However, with re-structuring of heavy industry in eastern states and the need to abide by EU environmental rules in future, it is likely the same developments will take place throughout Europe. In conclusion, the need for sulphur fertilisers for optimum crop yields, for optimum use of nitrogen and for crop quality is increasing rapidly and will become more widespread in the near future.
Prof. Steve P McGrath, Dr. Fangjie Zhao and Dr. Mechteld M A Blake-Kalff, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
24 pages, 12figures, 2 tables, 20 references.