Burley tobacco removes large amounts of potassium (K) from soil. A 2,600 pound/A cured leaf crop removes around 200 lbs K/A/yr, with about 110 lbs of that in the leaf and 90 lbs in the stalk. Because of such a heavy soil demand for K, growers are always concerned that application of fertilizer K be sufficient for top production. The University of Kentucky's Soil Testing Laboratory (Division of Regulatory Services) provides a statewide soil testing service. The Mehlich-3 soil extractant is used by the UK lab, and soil test K values from use of this extractant (reported as lbs K/A) are categorized as follows for burley tobacco: Very High, over 450; High, 450-301; Medium, 300-201; Low, 200-91; Very Low, less than 91. The amount of potash fertilizer (K2O) recommended varies from 400 lbs/A for soil test K levels below 91 to 0 when soil test K levels are above 450.
Wells, Kenneth L.; Dollarhide, James E.; and Shields, Val, "Potassium Soil Test Correlation and Calibration for Burley Tobacco Grown on an Allegheny Loam Soil" (1997). Agronomy Notes. 13.