Hello! My name is Dan Marzu, I'm the North Central Region Nutrient and Pest Management
Outreach Specialist. I'll be discussing determining sulfur application rates.
Sulfur is a secondary nutrient however, it still plays an important role in crop nutrient needs.
Sulfur is required for protein synthesis, aids in seed production, and in producing chlorophyll,
similar to nitrogen. Sulfur mineralizes in the soil, for every one percent organic matter
it has the potential to release 2.8 pounds of sulfur per acre.
Sulfur can leach but not as readily as nitrates, and it can also be tied in acidic clay soils.
In the past we have received sulfur through atmospheric deposition however,
we currently receive about one-third of the sulfur through this method as we did 30 years ago.
We currently receive 3-10 pounds of sulfur per acre through atmospheric deposition.
The highest amounts are in southeast Wisconsin, decreasing as we go to the northwest corner of
the state. The soil test we have for sulfur is not as precise as phosphorus or potassium, but it will
provide a baseline on how much sulfur might be in the soil. As you scout your fields look for
a light green color or interveinal chlorosis, as shown in the corn picture to the left. If
you see these symptoms take a tissue sample to determine if a sulfur application is needed.
Soil texture and crop need aid in determining if a sulfur application is needed. Here I have a chart
that shows the potential for retaining sulfate in the root zone. Notice how sands have a low
potential and the loamy or organic soils have a high to very high potential for retaining sulfate
in the soil. To the left, there's a list of crops that might be in your crop rotation based on the
need for sulfur fertilization. If the potential of a soil to retain sulfate is low, or medium and no
manure has been applied in the past two years, a sulfur application will most likely be needed
for crops with a medium or high relative need. If the soil is organic or if has a
significant amount of manure was applied then a profitable yield response to sulfur is unlikely.
Most of the manures we apply provide about one pound of sulfur per ton,
or one pound of sulfur per 1000 gallons during the first year. The exception is dried chicken
and turkey manure that will provide two pounds of sulfur per ton. An indoor manure pit from a swine
farrowing barn will provide two pounds of sulfur per 1000 gallons that first application
On the left-hand side, you'll see a chart with fertilizer sources for sulfur. All sulfate forms
are equally effective when surface applied or incorporated. Elemental S, or sulfur,
is insoluble and must be transformed into sulfate sulfur by soil bacteria to be effective. Elemental
sulfur should be incorporated in advance when the crops need it. Also, keep in mind that
ammonium thiosulfate should not be applied in-furrow as it will cause seedling damage.
In the upper right-hand corner, I have a chart for general sulfur fertilizer recommendations. For
forage crops, such as alfalfa, incorporate 25 to 50 pounds of sulfur per acre at seeding if sulfur
is deficient. Sulfur can also be top-dressed on established stands at a rate of 15 to 25 pounds of
sulfur per acre, if sulfur is needed. When applied at these rates sulfate sulfur will last two to
three years. Elemental sulfur, when incorporated in the soil, should last the life of the stand.
For row and small crops, annual applications of 10 to 25 pounds of sulfur are needed in fields
that are deficient in sulfur. Sandy soils may also require annual applications due to
potential leaching. If there is irrigation, there may be enough sulfate sulfur applied through the
irrigation water for the crop. You should be testing your water to see how much sulfur
is included in your water. Applications may be needed during wet years when irrigation is not
used as often. Remember if you apply manure, you might not need any additional sulfur
If you have any other questions on sulfur or other nutrients, please feel free to reach out to me
or one of the other NPM outreach specialists and we'd be happy to answer your questions. Thank you!