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Sulfur Fertilizer in Elemental Form Rarely a Good Choice in North Dakota
Ammonium sulfate will be the fertilizer of choice in most situations in North Dakota, once a need for sulfur is established by soil testing. Ammonium sulfate is readily available, relatively inexpensive, and it dissolves easily in water--this last is an important advantage over alternatives that dissolve less quickly. Also, ammonium sulfate contains about 20 percent nitrogen, an element often needed by crops. And it can be easily blended with other fertilizers.
Alternative compounds used to get sulfur into soil include calcium sulfate (gypsum), which has a low solubility compared to ammonium sulfate (Sul-Po-Mag) are other choices, but these can be relatively expensive because the potassium and magnesium they contain are not needed in most North Dakota soils.
The one form of sulfur that farmers should avoid when beginning to correct immediate sulfur deficiencies, is elemental sulfur. Elemental sulfur does have some advantages: it is easily handled, won't damage seed, is fairly cheap. The disadvantage is that it must be converted to sulfate by soil microorganisms before plants can use it, and before this happens it must be broken down into small particles.
Some elemental sulfur is powdered or granulated by the manufacturer and made available as fertilizer or fungicidal dust, but its practical use in North Dakota as a fertilizer is questionable. Granules may take years to break down into small enough particles to be converted to a sulfate form, and the dusts are difficult to spread and may stay suspended in the air a long time.
Some elemental sulfurs are blended with a bentonite clay before being granulated and this clay has the property of expanding when wet. If the soil is moist, elemental sulfur blended with bentonite clay may break down into fine particles within days, after which the microorganisms more quickly convert it to sulfate. Yet in North Dakota conversion may take months.
Organisms that convert the sulfur into sulfates work best in warm, moist soil. Elemental sulfur applied in the fall will not be converted to sulfate during the winter.
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