Keywords: Atmosphere, Deposition, Acid rain, Sulfur dioxide, Leaching, Crop responses
Sulfur emissions increased during the industrialisation of Europe, but by the mid-20th century, the adverse effects of sulfur 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 sulfur emissions in the 1990s. Data on sulfur dioxide in air and sulfate 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 sulfur in deposition have dropped below the requirements of many crops. Recent evidence shows that most arable soils have not stored the anthropogenic sulfur that was deposited in the past, and that leaching is resulting in decreasing soil sulfur status. This, coupled with the earlier change in Europe to low sulfur fertilizers has meant that crop responses to sulfur-containing fertilizers are now becoming common. There is evidence from the UK that the reduction in sulfur emissions is running almost 10 years ahead of schedule and the occurrence of sulfur deficiency is increasing. The rate of development of sulfur 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 sulfur fertilizers 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.
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