Why Do I Need More Sulfur?
Sep 06, 2011
Question: I thought I had a nitrogen deficiency in my corn this season, but tissue tests actually showed I didn’t have enough sulfur present to make the nitrogen available to the corn. What’s the deal with that?
Answer: That is a problem we’re seeing increasingly and that many farmers don’t realize. You need sulfur to metabolize nitrogen and make it available to the corn plants. A bushel of corn contains 0.08 lb. of sulfur in the grain and 0.09 lb. in the stalk, for a total of 0.17 lb. That means a 200-bu. per acre corn yield removes 34 lb. of sulfur, or 102 lb. of sulfate—the form of sulfur taken up by plants per acre. Those higher yields we’re seeing today require more sulfur, and there’s not as much available. Reasons: the old single superphosphate your grandpa used contained 12% sulfur, plus today’s pesticides contain less sulfur. We also don’t burn crop residue anymore, which released sulfur into the atmosphere. Your challenge is to maintain the proper ratio between nitrogen and sulfur. Corn needs about 1 lb. of available sulfur per 14 lb. of available nitrogen. You need to pay special attention to sulfur levels in soils that have less than 3% organic matter. Organic matter is your main supplier of sulfur. In soils with more than 3 % organic matter, sulfur probably can take care of itself.
Sulfur’s role in plants includes producing lignin and pectin, producing chlorophyll and metabolizing nitrogen. Here are ideas on how to make sulfur work harder in your fields.