Pale, striped corn that has been common in eastern South Dakota this growing season is likely the result of sulfur deficiency, a specialist says.
In most cases, however, corn will be able to tap into sulfur in the soil about this time of year as it sinks roots deeper and as organic matter decays more rapidly.
Jim Gerwing, extension soils specialist at South Dakota State University, says sulfur-deficient corn has stripes and is also pale or yellow in color. The stripes are more pronounced in the whorl area of five- to seven-leaf corn.
"Some people confuse these stripes with zinc stripes, which are normally on the third and fourth leaf and not across the entire plant," Gerwing says. "Also, zinc deficiencies cause white areas on the leaf and the entire plant isn't as pale as with sulfur deficiencies."
It's also possible to confuse sulfur deficiency with nitrogen deficiency, which causes a pale or yellow color but not striping. Gerwing adds that a nitrogen deficiency will cause the first couple of leaves at the bottom of the plant to turn brown by about the five- or six-leaf stage.
Sulfur deficiency occurs most readily in soils low in organic matter, such as eroded hillsides and coarse, sandy soils. If it persists, the deficiency can reduce yields by 20-34 bu on eroded hillsides and by eight to 12 bu in coarse soils, although such areas typically make up only a small portion of a field.
The good news is that crops in eastern South Dakota usually will grow out of a sulfur deficiency. Gerwing says that's because microbial action increases as the soil warms, making more sulfur available through the decay of organic matter. And as plants sink deeper roots, they're able to find sulfur in eastern South Dakota's glacial till soils at about 2’-3’.
This year has been worse for sulfur deficiencies because the spring was both wet and cold, Gerwing says. The wet conditions leached some of the water-soluble sulfate deeper in the soil. And the cool weather kept the soils from warming up, preventing microbes from breaking down organic material to release more sulfur.
Gerwing says farmers may want to make note of where sulfur deficiencies have occurred this year. Those are areas that may need to have sulfur added early in the year in future growing seasons.
Gerwing says elemental sulfur is not the best choice to apply early in the year because it requires warm soils and microbial action in order to break down and become available to plants.
Instead, he recommends applying a dry granular product, ammonium sulfate, or liquid ammonium thiosulfate. Either product should be broadcast at or before planting at a rate that provides 25 lbs of sulfur per acre, Gerwing says. Another option would be to apply 10 lbs of sulfur per acre as a starter band at planting beside but not in contact with the seed.