Sulphur (or sulfur)is also known as the “ignored primary nutrient” since not many people realize that it is one of the macro nutrients and is extremely important. The role of S has been ignored for long times since its effect on plant growth was not known. Researchers inadvertently applied large amounts sulphur through the use of potassium sulphate (K2SO4). The results were quite often misinterpreted as a potassium reaction.
Sulphur form an important part in the production of protein groups (especially amino acid cystine, cysteine and methionine) and alkaloid compounds. These three amino acids contain approximately 90% of the total sulphur found in the plant. Sulphur is also important for the formation of important metabolites such as coenzyme A, which is involved in the oxidation and synthesis of fatty and amino acids. Other substances which are important for the plant such as S-adenosylethionine, lipoic acid, sulfolipid and ferredoxin also contain S. These compounds are responsible for processes such as photosynthesis, nitrate and sulphate reduction and the synthesis of chlorophyll. Carbon dioxide assimilation and the nitrate/nitrogen reduction cycles are also influenced by the concentration of sulphur in the plant. The importance of sulphur cannot be underestimated!