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• The usual suspects include nitrogen deficiency, disease, or even herbicide burn, but last year in North Carolina some of the yellowing problems came from zinc deficiency, and in some cases on soils that showed adequate amounts of zinc, based on soil samples.
EARLY-SEASON zinc deficiency can hurt grain sorghum yield and lower test weights at harvest time.
There is no doubt grain sorghum acreage will go up this year in the Carolinas, some contend as much as 150,000 acres in the two states, and one problem to watch out for is yellowing of the crop once it gets up and growing.
The usual suspects include nitrogen deficiency, disease, or even herbicide burn, but last year in North Carolina some of the yellowing problems came from zinc deficiency, and in some cases on soils that showed adequate amounts of zinc, based on soil samples.
The rapid increase in grain sorghum in North Carolina has prompted North Carolina State Corn Specialist Ronnie Heiniger to work with the crop. He says he got a number of calls early in the growing season last year about yellowing areas in grain sorghum fields.
“My first thought was it must be a pH problem or nitrogen deficiency. In this one particular field, the pH was good and the grower had used 150-160 pounds of nitrogen per acre in the field. That led us to look at other causes and way down the list was zinc deficiency,” Heiniger says.
Again, based on soil sample results, the field showed zinc in the 30 range, which should have been adequate for grain sorghum at that stage of growth. In this case the soil sample was correct, but not for the grain sorghum in the field.
“We applied six pounds of zinc (two pounds actual ingredient) per acre in a foliar spray on this particular field. Within 7-10 days it had regained its green color and by harvest it was close, if not exactly, caught up to other areas of the field not affected by a lack of zinc,” he adds.
Grain sorghum is a very slow growing, spindly crop in the early stages, and evidently it doesn’t take up zinc very efficiently. And, based on looking at other growers fields, the same seems to be true for sulfur.
Heiniger says there were a number of grain sorghum fields last year that were hurt by either or both zinc and sulfur deficiencies.