Release Rates of Soluble and Controlled-release Potassium Fertilizers

Abstract

Release rates for 13 commercially available soluble and controlled-release K fertilizers were determined in sand columns at 21C. Potassium chloride, KMgSO4, and K2CO3 were leached completely from the columns within 3 or 4 weeks. Osmocote 0N-0P-38.3K, Multicote 9N-0P-26.7K, the two S-coated K2SO4 products, and Nutricote 2N-0P-30.8K Ty 180 all had similar release curves, with fairly rapid release during the first 20 to 24 weeks, slower release for the next 10 to 12 weeks, and virtually no K release thereafter.