Elemental sulfur is essential for crops, provided that the product is used. Let’s find out what elemental sulfur can bring to agriculture and how to use it properly.
What is elemental sulfur?
Sulfur is a macro-element essential to the productivity and quality of crops. It is an element on which particular attention must be paid to improve crop performance and in particular to make the best use of nitrogen.
Elemental Sulfur: The Solution for Effective Nutritional Intake
Nitrogen and sulfur are dependent on each other in plant metabolism. A N/S balance is required, approximately 1 unit of sulfur to 5 units of nitrogen for cruciferous vegetables, 1 to 8 for legumes, and 1 to 10 for cereals.
Crop requirements are expressed in So3 equivalent. Note that, due to molecular weights, 1 unit of sulfur is equivalent to 3 units
of sulfates (So4) or 2.5 sulfites (So3). It therefore takes 2.5 times less elemental sulfur than So3 to meet crop requirements (e.g.: For a cereal, a requirement of 200 units of nitrogen corresponds to a requirement of 20 units of elemental sulfur).
| Requirements | Crops | Elemental Sulfur Requirement (Kg/ha) | So3 equivalent (Kg/ha) |
|---|---|---|---|
| Strong | Crucifers, garlic, onions, alfalfa, clover, forage grasses | 40 à 80 | 200 à 100 |
| Medium to strong | Orchard, vineyard | 40 | 80 |
| Average | Cereals, corn, potatoes, beets | 20 à 40 | 100 à 50 |
| Weak | All other cultures | 8 à 20 | 50 à 30 |
Provides basic “fertilization”
Elemental sulfur requires oxidation by microbial activity to be assimilated by plants. Unlike the So4 form, it is not leachable and remains available during the cycle depending on needs. Note that a supply of a So4 form in February/March is not relevant because crops mainly need Sulfur during the bolting and flowering period (like nitrogen).
Helps preserve organic matter
The So4 form found in fertilizers is a booster of bacterial activity and will have the effect of accelerating the degradation of organic matter at an inopportune moment. The contribution of elemental Sulfur will allow microorganisms to meet the needs of crops without degrading organic matter.
Unlock items
The decrease in pH observed near elemental sulfur allows blocked elements to be dissolved (example: phosphorus, iron in alkaline soil).
💡 Elemental sulfur: two origins not to be confused
Elemental sulfur of fossil origin
It comes from the refining of oil using the Claus process.
❌Since it is not of natural origin, microorganisms (bacteria) perceive this sulfur as a chemical pollutant.
Its effectiveness is much lower than native sulphur from quarries. The recommended doses of use are 150 to 300 kg/ha.
Given its petrochemical origin, it seems surprising that this elemental sulfur is used in organic farming.
Native elemental sulfur from quarries
(Soufrel, Silisoufre)
From traditional extraction: Ore extraction, crushing and grinding
✔️Does not have the disadvantages of sulfur of fossil origin: it is mainly perceived as a natural product by the bacteria which must oxidize it.
More interesting to use in terms of efficiency and cost/ha.
The recommended use doses are 10kg to 80kg/ha.
It can be used in organic farming.
Analysis of 2 elemental sulfurs by an independent laboratory April 2024
Sample analysis 1
Analysis report no. AR-24-AA-044778-02
Ech No. 370-2024-00004780
Requested analyses: AAK Sulfur isotopic value
Conclusion of the analysis : the value of the isotopic deviation
of sulfur measured on this sample is in agreement
with a fossil origin (from oil)
Sample analysis 2 (Soufrel, Silisoufre)
Analysis report no. AR-24-AA-044777-02
Ech No. 370-2024-00004779
Requested analyses: AAK Sulfur isotopic value
Conclusion of the analysis
: the value of the sulfur isotopic deviation measured on this sample is in agreement with a mineral origin
