Perfusion studies with bromoxynil octanoate in soil

The breakdown of bromoxynil octanoate in 5 different soil types has been studied in a soil perfusion apparatus using herbicide labelled with ¹⁴C either in the cyano group or in the aromatic ring. Even when applied at rates equivalent to 5 to 25 times those used commercially, the herbicide was fairly rapidly and extensively degraded at 15°. After 12 to 13 weeks, up to 80% of the radioactivity in the ¹⁴CN group and up to 63 % of the ¹⁴C in the ring were liberated as carbon dioxide. A small proportion (16 to 19%) of the radioactivity from ring-labelled herbicide remained attached to the soil, probably not as the original herbicide, but in a form not readily leached. Only trace quantities of 3,5-dibromo-4-hydroxy-benzamide (0.5%) and 3,5-dibromo-4-hydroxybenzoic acid (0.1%) were detectable during these soil perfusions.