Research was conducted in 2009 and 2010 to evaluate the effects of various potassium rates and application methods on yield and quality of flue-cured tobacco. Locations were the Upper Coastal Plain Research Station in Rocky Mount, NC and the Oxford Tobacco Research Station in Oxford, NC. The purpose of this research was to evaluate current potassium rate recommendations and alternative application methods.

The first study evaluated the effects of various potassium rates on the yield and quality of flue-cured tobacco. Rates applied were 0, 75, 100, 125, 150, 175, 200, 225 lbs K₂O per acre, banded beside the plant at transplanting using 0-0-22 (K Mag). In 2009, when tobacco was grown on relative fine textured soils (sandy loam and clay loam) at the Rocky Mount and Oxford locations and with high potassium indices, no yield or quality response to potassium rate was observed. In 2010, plots were selected with more coarse textured soils with only slightly lower potassium indices. Under those conditions, yield and quality was reduced when less than 75 pounds of K₂O per acre was applied. When the potassium index was high, which is common in tobacco producing areas of NC, results from the rate studies indicate that soil texture is still an important factor in determining the amount of potassium required for optimum yield and quality. Potassium rate recommendations in NC range from 90 to 160 lbs of K₂O per acre depending upon K index and soil texture. Under the environmental conditions of these experiments, current potassium rate recommendations appear to be higher than necessary for finer textured soils with a high potassium index, but may be accurate for coarse textured soils in tobacco producing areas of NC.

The second study evaluated the effects of various potassium rates and application methods on the yield and quality of flue-cured tobacco. Potassium rates applied were 75, 125, 175, 225 lbs K₂O per acre. Application timings were: broadcast one month before planting, broadcast one week before planting, banded at planting, and two bands (1/2 after planting and 1/2 at layby). Based on yield and quality data only, it appears that under the conditions of these experiments, 75 lbs per acre of K₂O applied broadcast one month before planting, broadcast at planting, banded at planting, OR applied in split applications, provided adequate amounts of plant available potassium to optimize yield and quality. It is likely that early broadcast applications of K₂O with current rate recommendations would only be of concern with combinations of conditions that included coarse soil textures, low potassium indices, and/or excessive leaching rainfall.