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Sulphur (S) nutrition of crops has received a lot of attention since the advent of high grade phosphates and higher grade NPK fertilizer mixtures which typically contain very low levels of S.

When considering your source of Sulphur (S) containing fertilizer, take time to assess the availability of the S sources that are available. Plants take up S in the Sulphate – SO42- form which is water soluble and immediately available for plant uptake while elemental S is not water soluble and must first be oxidized to the SO42- form by microbial action before becoming available for plant uptake. The oxidation rate of elemental S into the plant available SO42- form is also dependent on the particle size of the elemental S; the finer the particle size the quicker the conversion to the SO42- form.

Granular elemental sources of S have been used in blends to “supply” the crops requirement, these granules don’t supply the crop’s immediate S requirement and can often be found encased in the soil or lying on the soil surface several years after application.

Residual granular sulphur on the soil surface three years after application.

Residual granular sulphur on the soil surface three years after application on sugar cane.

Mark Hawksworth

Author Mark Hawksworth

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