Recent increases in conservation tillage, price increases in the cost of potassium (K) fertilizer, reductions in K application rates, new crop rotations with increased K removal, poor corn fertility programs, and a move towards high yielding soybean cultivars have all created concern about K fertilizer recommendations and critical soil levels. Unlike nitrogen, potassium does not move in most soils except for sandy, low cation exchange capacity locations. Previous work on soybean K fertilization has caused Iowa to upwardly revise K recommendations to 170-200 ppm. Additional data have suggested no correlation between K removal rate and soil test K values. While some data show elevated K levels...