Greenhouse pot experiments were conducted to compare responses of corn ( Zea mays L.) and snap beans ( Phaseolus vulgaris L.) to 0 to 1,600 mg of K/pot as KNO 3 , KCl, and K 2 SO 4 on K‐deficient soils (3 kg of soil/pot). Marked responses were obtained to applied K, which were similar among sources, except for a toxic salt effect of 1,600 mg of K as KCl. Marked reciprocal K‐N, K‐P, K‐Ca, and K‐Mg relationships with yield response to rates of applied K were attributed to both dilution and ion antagonism. The latter was most pronounced at higher K rates giving little or no additional yield response and resulting in decreased Ca, Mg, or P uptake. There was a close relationship between total N and total cation concentrations in corn leaves but not in bean leaves. This difference is attributed to absorption of much of the N as NO 3 ‐N by corn and as biologically fixed NH 2 ‐N by snap beans.