Herbicide Adsorption and Release Properties of Five Oxadiazon-Coated Fertilizers

Abstract

Laboratory experiments were conducted to determine the release of oxadiazon coated on control-release fertilizers. Five fertilizers and glass beads (nonabsorbent control) were coated with 14C-oxadiazon + formulated oxadiazon at a herbicide-to-fertilizer concentration of 0.3 mg ai/g. Coated fertilizers were subjected to 14 consecutive daily water leaching events. For the control-release fertilizers, Nutricote, Meister and Osmocote, 70%–80% of the coated oxadiazon was released in the first 3 leaching events; each leaching event after the 7th leaching event contained less than 1% of total applied oxadiazon. In contrast, 56% of the total applied oxadiazon was leached from Polyon 24N–1.7P–10K (24–4–12) in the first 3 leachings and similar percentages of oxadiazon were leached over each of the last 11 leaching events. Coating the five fertilizers with isoxaben produced similar results. A second experiment evaluated the effects of the addition of Prime Oil, Complex (sticker), Plex (sticker), and Intac (sticker) on release rates of oxadiazon-coated Osmocote 17N–3.1P–10K (17–7–12). Oxadiazon-coated Osmocote alone and oxadiazon-coated Polyon alone were also evaluated. Eighty-five percent of the total applied oxadiazon was leached from oxadiazon-coated Osmocote alone during the first leaching event and less than 1% was recovered with each consecutive leaching after the third leaching. Oxadiazon-coated Osmocote treated with Plex responded similarly to oxadiazon-coated Osmocote. Oxadiazon-coated Osmocote treated with Complex, Intac, or Prime Oil and oxadiazon-coated Polyon lost 21%, 20%, 16%, and 24%, respectively, of the applied herbicide after the first leaching event. Thereafter, nearly equal amounts of oxadiazon (5%) were leached from Complex, Prime Oil, Intac and Polyon alone from the 6th through the 11th leaching events.

Polymeric Resins Adsorb and Release Oryzalin in Response to pH

“…Novel methods of herbicide delivery have been investigated in ornamental container production with varying levels of success. All have been dependent on physical release of the herbicide via dissolving of either tablets (Gorski et al 1989;Koncal et al 1981;Verma and Smith 1978), coatings on encapsulated fertilizers (Crossan et al 1997;Keel et al 1998), coating on tree bark (Mathers 2003), or impregnated mulches (Fretz 1973) and cellulose materials (Fain et al 2003). However, none of these methods has been adopted commercially.…”