The sulfur cycle in agriculture Sulfur is one of the 6 main nutrients for crop growth. It is an essential part of amino acids, co-enzymes and vitamins. Protein content and quality of crops rely on sufficient supply of sulfur. Since environmental measures have improved air quality in industrialized countries, depositions of sulfur have dropped. At the same time, yield and quality expectations have increased. Both factors together account for the rising attention to sulfur fertilization in the las