The Global Sulphur Cycle and Its Links to Plant Environment

The fundamental importance of sulphur as one of the three philosophic essentials goes back to alchemy. The production of sulphuric acid was a gauge for the industrial state of a nation at the start of the 20th century. Less than 80 years later sulphur was stigmatised as the yellow poison after being identified as one of the major reasons for the acid rain problem. Later, after clean air acts came into force, severe sulphur deficiency became a major nutrient disorder in agricultural production. An insufficient sulphur supply reduces crop productivity, diminishes crop quality, impairs the nitrogen utilisation efficiency and thus increased the undesired nitrogen losses to the environment. Understanding the mechanisms and processes involved in the sulphur cycling at different scales and its links to the plant environment is an important contribution to sustainable agricultural production and environmental protection. Significant advances in plant nutrition and soil science can be expected by establishing site-specific sulphur balances for improving fertilizer strategies, by identifying regulatory mechanisms in the sulphur metabolism of plants for enhancing the natural resistance against pathogens, and by determining the sulphur cycling in the edaphon for promoting soil life.