Tobacco growers should be on the lookout for potassium deficiency this year. Bryant Spivey, county extension director in Johnston County, N.C., says K deficiency is not unusual where there has been a lot of rain, particularly on sandy soils.
"Potassium deficiency can even occur if adequate to excessive fertilizer potassium has been applied," Spivey notes.
South Carolina tobacco growers have also shared wet field conditions with much of the rest of the Southeast this year. Bob Bett, a Clemson extension agent in Marion County says potassium deficiency on sandy soils is wide spread in his county and in surrounding counties this year.
"The continuous rains we've had have leeched the potash or potassium on down below the root zone, says Bett. "Plus, there is the problem that whenever the tobacco plant is set, if there is adequate moisture at the upper level, it doesn't force the roots to grow down deep. The roots just grow out wide to get moisture. If the rain at the same time is pushing the nutrients down and the roots don't have to go down, then the plant is working against itself."
To handle the situation, Betts has been recommending some additional potassium later in the season than tobacco growers would normally apply it and he believes this strategy is working well to counteract the problem.
However, Spivey notes that seeing the symptoms of potassium deficiency in the field is not necessarily an indication that additional K is needed. The plant may be growing so fast that it can't take up the K it needs, he says.
Potassium deficiency causes mottling and brownish yellow spots on the tips of leaves, Spivey notes. As the season progresses brownish-yellow spots on leaves can turn brown and possibly fall out, "leaving a ragged appearance."
"Leaves may be puckered," Spivey says, "with the tips and margins curled downward."
Spivey points out early topping may help, with more nutrients going to the leaves. It also encourages further root development.
If a grower suspects he has K deficiency in his tobacco, it would be wise for him to seek advice from his county extension agent or other expert. A flue-cured tobacco production guide from N.C. State University can also be downloaded on the Internet from ipm.ncsu.edu/Production_Guides/Flue-Cured/2006/contents.html. Chapter five in the guide addresses nutrient management.