Several experiments were conducted to determine release rates of five oxadiazon-coated fertilizers. Five fertilizers and 4-mm glass beads (nonabsorbent control) were coated with 14C-oxadiazon + formulated oxadiazon, then placed in a separatory funnel and leached with 20 ml of water for 14 days. 14C-oxadiazon was quantified by use of liquid scintillation spectrometry. For glass beads, Nutricote, Meister, and Osmocote, 70% to 80% of the 14C-oxadiazon was recovered in the first two leaching events. Oxadiazon leached from Polyon was 47% during the first two events and remaining oxadiazon was slowly released over the next 12 leaching events. 14C-oxadiazon from the other fertilizers over the last 12 days of leaching was less than that recovered from Polyon. Evaluation of the total surface area of a 50-g sample revealed Polyon had the greatest total surface area of the five fertilizers. Scanning electron micrographs before and after leachingindicated potential erosion of the Polyon surface compared to little or no change in the surfaces of the other fertilizers.
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