SulFer 85 Particle size
SULFER 85 AND TIGER 90 CR
SulFer 85 particle sizes at
Day 1, Tiger 90 particle sizes after 6 months in water
300 micron +
Particles need to be less
than 150 microns to degrade in 12 months
published work is now showing that the oxidation of Sulphur to sulphate in
soils is dependent on a number of factors:
Canola Council of Canada considers that Sulphur fertilizer containing elemental
sulphur must be managed differently than sulphate based fertilizer to achieve
good efficacy--availability is delayed until soil bacteria oxidize it into the
sulphate form. The conversion rate from elemental sulphur to sulphate depends
on the particle size, the degree of dispersion in the soil, and the growing
conditions for the bacteria (moisture, temperature). Common elemental sulphur
fertilizers are formulated as granules or pastilles (split pea shape) for ease
of shipping and handling, each consisting of thousands of individual particles.
The surface area of these individual particles is the access where the soil
bacteria "feed", converting the elemental sulphur to sulphate. Small
particles have the largest surface area and, therefore, the fastest oxidation
Research indicates that particles less than 150 microns in size will
convert quickly if well mixed with soil. Some elemental sulphur fertilizers
have particles consistently smaller than 150 microns such as €œSulFer 85".
Other products consist of a mixture of particles ranging from smaller to larger
than 150 microns such as "Tiger 90CR". Granules that break down
readily and completely will allow quicker oxidation and sulphate availability.
Research in western Canadahas found that break down of elemental sulphur granules is greatest when
the product is applied to the soil surface and exposed to rain/snow and frost.
Subsequent tillage will then further disperse the degraded granule. In
contrast, band and seed row placement, or immediate incorporation following broadcasting,
will reduce the granule dispersion and the oxidation rate
Another factor that influences the oxidation rate is previous use of elemental sulphur in the field. Exposure to elemental sulphur in the past has been shown to increase oxidation rates of subsequent applications, probably due to stimulation of the S-oxidizing bacterial population.