Farmers need to watch for potassium issues in flue-cured tobacco
RALEIGH — This has been a wet spring, with weather affecting some crops early this season, including flue-cured tobacco planted in sandier soils.
Agronomists with the N.C. Department of Agriculture and Consumer Services in and near the coastal plains are reporting some leaching losses of fertilizer from excessive rainfall. Specifically, they are seeing potassium losses in fertilizer that was applied earlier to the flue-cured tobacco crop in these soils.
“Over the past few weeks, tobacco leaves in the mid to upper stalk positions have developed a mottling and brownish-yellow spots on leaf tips, which are classic symptoms of potassium deficiency,” said David Hardy, Soil Testing Section chief with the NCDA&CS Agronomic Services Division. “Farmers should be on the lookout for these conditions, as fertilizer adjustments can help the plants recover.”
Don Nicholson, a NCDA&CS regional agronomist who works closely with tobacco growers in the western edge of the coastal plains, has seen the effects first hand.
“Growers know that tobacco requires high rates of potassium and usually it is not a problem, but this year is unique,” Nicholson said. “I have taken soil samples at different depths to look at potassium levels in the soil, and the results certainly confirm that leaching has occurred. This is also evident in results from plant tissue testing.”
Chris Jernigan, a regional agronomist who focuses heavily on tobacco production in the central coastal plain, confirms those findings, and is offering farmers recommendations on fertilizer management.
“The leaching losses of potassium this year have been worse where fertilizer was broadcast over entire fields in advance of transplanting the crop,” Jernigan said. “This year will likely be a reminder of the importance of placement and timing of fertilizer application. Because broadcast applications are usually made several weeks before the crop is transplanted, it makes it more vulnerable to leaching conditions. Research shows that banding fertilizer about 4 to 6 inches to the side of the plant soon after transplanting produces more consistent yields than broadcast applications.”
Some growers have applied supplemental potassium recently to correct leaching. “As tobacco is reaching topping time in portions of the state, we know this will stimulate root growth and hopefully help this crop root deeper into lower soil depths where additional potassium can be found on the less sandy soil types,” Jernigan said.
Nicholson added that “tobacco is growing rapidly, and with recent drier field conditions, growers may still see some potassium deficiency.” Additional application of fertilizer at this time should be considered carefully on a field-by-field basis, considering the development of the crop, fertilizer applied along with its timing and method of application, and soil type.
Growers with concerns about the development of their crop are advised to contact their NCDA&CS regional agronomists. A list of regional agronomists can be found at www.ncagr.gov/agronomi/rahome.htm. The Agronomic Division offers nematode assay, plant tissue testing, and soil testing that can assist in management of flue-cured tobacco and other crops.