K in Missouri Subsoils
Soil samples to a 3-foot depth show that the subsoil is a greater reservoir of K than the topsoil over most of Missouri.
Current University of Missouri fertilizer recommendations have a target level of 280 lb K/acre (140 ppm K) for a typical silt loam soil with CEC = 12. Soil K is measured with ammonium acetate extraction and atomic absorption photometry. Measurements of soil K in 180 deep soil samples across Missouri show that the subsoil usually contains more than three times this much K in most of Missouri.
