The effect of carriers and carrier additives on the short term persistence of trifluralin

Abstract

It is currently recommended that a,a,a-trifluoro- 2,6-dinitro-N,N-dipropyl-P-toluidine (trifluralin) be mechanically incorporated within 8 hr after application to prevent loss of the herbicide from the soil surface. Various carriers and carrier additives were evaluated for their effectiveness in delaying the loss of trifluralin from an undisturbed soil surface. In the laboratory, significantly more trifluralin remained on the surface of a Miller clay soil after a 24 hr period when applied in diesel oil or paraffin oil than when applied in water. Field studies indicated that paraffin oil significantly increased the persistence of the herbicide after 24 hr on the surface of Lufkin sandy loam soil at 60% field capacity. After 48 hr there was no difference in paraffin oil and water. Paraffin oil and diesel oil decreased the persistence of trifluralin on the same soil at 13% field capacity. Two surfactants and three free radical inhibitors were ineffective in increasing trifluralin persistence when used as carrier additives. Studies conducted to determine the relative effects of volatilization and photodecomposition on trifluralin loss indicated that UV light was of minor importance when water was used as a carrier. UV light caused a significant loss of trifluralin from a wet (80% field capacity) Miller clay soil when the herbicide was applied in paraffin oil but failed to have the same influence on dry soil. Volatilization was found to be the major means of trifluralin loss from wet Miller clay soil.