Sulphur – A Major Nutrient
Sulphur (S) is classified as a secondary element, along with Calcium (Ca) and Magnesium (Mg), but it is sometimes called “the 4th major nutrient”. Some crops can take up as much S as P. Sulphur has become more important as a limiting nutrient in crop production in recent years for several reasons. These include higher crop yields that require more S, less S impurities in modern fertilizers, less use of S-containing pesticides, reduced industrial S emissions to the atmosphere, and a greater awareness of S needs.
Sulphur Supports Many Functions in Plants
It is used in the formation of amino acids, proteins and oils. It is necessary for chlorophyll formation, promotes nodulation in legumes, helps develop and activate certain enzymes and vitamins and is a structural component of 2 of the 21 amino acids that form protein.
Sulphur Deficiency Symptoms in Plants
Sulphur-deficient plants often are pale green, yellowish green to completely yellow. These characteristics, which are like characteristics of nitrogen-deficient plants, are first observable in the younger leaves. Deficient plants are small with small and often narrow leaves.
Sulphur is Closely Associated with Nitrogen (N) for Fulfillment
The relationship between S and N is not surprising since both are components of protein and are involved in chlorophyll formation. They are also linked by the role of S in the conversion of nitrate to amino acids. Crops having high N need will usually also have high S needs.
Most of the Sulphur in Most Soils is Contained in Organic Matter
Organic S must be mineralized to the inorganic sulphate anion before it can be taken up by crops. Organic matter decomposition and the resulting S release is affected by temperature and moisture and generally conditions that favor crop growth also favor mineralization and release of S, although this may be less likely with cool season crops. Sulfate, like most anions, is somewhat mobile in soils and therefore subject to leaching. Soil conditions where S is most likely to be deficient are low organic matter levels, coarse (sandy) texture with good drainage and high rainfall conditions. But these are generalizations and S can be deficient under other conditions as well.
Points to be Considered When Making Sulphur Fertilization Decisions
Among these are crop and yield goal, soil and plant analysis, organic matter content, soil texture and contribution from other sources such as irrigation water and manure. High yielding forage crops such as alfalfa and hybrid bermuda grass remove more S than most grain crops and tend to be relatively responsive. Soil test S is usually a measure of sulfate-S and as with nitrate-N samples should be taken deeper than normal (0 to 2 feet) because of sulfate mobility in the soil.
Soils containing less than 2% organic matter are most commonly S deficient; however, deficiencies do occur in soils with higher organic matter. Coarse textured soils are more apt to need S, but finer textured soils can also be deficient. Sulphur content of irrigation water should be determined since in some cases it can deliver significant amount of S.
Source:
https://www.cropnutrition.com/nutrient-knowledge/sulfur