In response to questions being asked by tobacco growers about the effectiveness of sulfate of potash magnesia (SPM; 21% K2O and 11% Mg) as coinpared to sulfate of potash (SP; 50% K2O), field studies were conducted during 1993-1994 to compare the two potassium (K) sources for use on burley tobacco. Any effect of SPM on yield of tobacco should be due to Mg since the only difference between the two sources in kind of nutrient contained is the presence of magnesium (Mg) in SPM. To compare the two K sources, we selected field sites low enough in soil test K levels that normally would result in increased tobacco yields due to application of fertilizer K.
Wells, Kenneth L.; Dollarhide, James E.; and Reese, Mark, "The Effect of Rate and Source of Potassium Fertilizer on Cured Leaf Yield of Burley Tobacco and Leaf Content and Soil Test Levels of Potassium and Magnesium" (1995). Soil Science News and Views. 145.