Tobacco Crops Showing Potassium Deficiency

Source from:  MyNC.com 06/30/2009

JOHNSTON COUNTY, N.C. - Rainfall during the month of June and high fertility levels have resulted in a very rapidly growing tobacco crop in Johnston County. When tobacco grows quickly, it is not unusual to see potassium deficiency, especially on sandy soils. Potassium deficiency can even occur if adequate to excessive fertilizer potassium has been applied. Potassium deficiency causes slight mottling and brownish-yellow spots on leaf tips. Later there are brownish-yellow spots along leaf margins that later turn brown and may even fall out, leaving a ragged appearance. Leaves may be puckered, with the tips and margins curled downward. Symptoms are often noted on rapidly growing plants and may be accentuated by excessive nitrogen rates. Potassium deficiency can be found in many Johnston County tobacco fields at the present time. It can be found in most all varieties and with all fertilizer programs. It is much more severe and noticeable on sandy soils and in some cases it is more severe on field borders where potassium fertilizers were broadcast applied. In most cases, the appearance of potassium deficiency is not an indication that additional potassium fertilizer is needed. It is highly likely that if adequate potassium was applied that adequate levels still remain in the soil. The plant is just growing so fast in some cases that the roots cannot absorb enough potassium to meet the plant needs. If this problem is noted growers should continue to manage the crop as normal. Early topping may be the best remedy, as it will allow the plant to transport necessary nutrients to harvestable leaves and not to a worthless flower. In addition, topping encourages further root development allowing improved nutrient uptake and utilization from the soil. If application errors are found, additional potassium application may help tobacco recover. Enditem