Phytotoxicity of Bensulide and Trifluralin in Several Soils

Abstract

Seedlings of 19 plant species were grown in soils containing 0 to 1,000 ppm ofO,O-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl)benzenesulfonamide (bensulide) or 0 to 100 ppm ofa,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) to determine phytotoxicity. Standard growth curves were constructed. The concentration of bensulide required to reduce the growth of shoots 50% (GR₅₀) ranged from 1 ppm with barnyardgrass (Echinochloa crusgalli(L.) Beauv.) to more than 1,000 ppm with carrot (Daucus carotaL., var. Long Imperator). Several plant species were more sensitive to bensulide in a Hidalgo sandy loam (pH 8.1) than in other soils including a Delfina loamy fine sand (pH 6.0). The concentration of trifluralin required to reduce the growth of shoots 50% (GR₅₀) was not markedly affected by soil texture and ranged from 0.1 ppm with German millet (Setaria italica(L.) Beauv.) to more than 100 ppm with Long Imperator carrot. The standard growth curves have been used to quantify herbicidal activities in field soils.