The foliar absorption of potassium from organic and inorganic potassium carriers

Using excised trifoliate leaves of 3 week‐old Glycine max ‘Bragg’ seedlings, a total of 31 organic and inorganic potassium compounds were tested for their efficacy of foliar potassium absorption at 10 mM K (using 86Rb as a tracer for K) and pH 6.3. Of the 14 inorganic K compounds screened, potassium bicarbonate, nitrite and several phosphate compounds yielded the highest % K absorption. Five of the inorganic K compounds caused slight leaf burn. Most of the 17 organic K compounds yielded higher % K absorption than the inorganic K compounds. Potassium acetate had the highest % K absorption without causing leaf burn. Monocarboxylic K compounds had greater % K absorption than the di‐ and tricarboxylic compounds. Chemical groups which increased polarity tended to decrease absorption. The absorption data for all K compounds tested could be partially explained by considering molecular weights and drying characteristics on the leaf surface. There was a positive correlation between total % K absorption and the degree of translocation away from the treated area for the inorganic K compounds, but not for the organic K compounds.