EFFECT OF TILLAGE AND COVER CROP ON FLUOMETURON ADSORPTION AND DEGRADATION UNDER CONTROLLED CONDITIONS

Fluomenturon adsorption and degradation were determined in soil collec ted at three depths from no-till + no cover, conventional-till + no co ver, no-till + vetch cover, and conventional-till + vetch cover in con tinuous cotton. These combinations of tillage + cover crop + soil dept h imparted a range of organic matter and pH to the soil. Soil organic matter and pH ranged from 0.9 to 2.5% and from 4.7 to 6.5, respectivel y. Fluometuron adsorption was affected by soil depth, tillage, and cov er crop. In surface soils (0 to 4 cm), fluometuron adsorption was grea ter in no-till + vetch plots than in conventional-tilled + no cover pl ots. Soil adsorption of fluometuron was positively correlated with org anic matter content and cation exchange capacity. Fluometuron degradat ion was not affected by adsorption, and degradation empirically fit a first-order model. Soil organic matter content had no apparent effect on fluometuron degradation rate. Fluometuron degradation was more rapi d at soil pH > 6 than at pH greater-than-or-equal-to 5, indicating a p otential shift in microbial activity or population due to lower soil p H. Fluometuron half-life ranged from 49 to 90 d. These data indicate t hat tillage and cover crop may affect soil dissipation of fluometuron by altering soil physical and chemical properties that affect fluometu ron degrading microorganisms or bioavailability. Nomenclature: Fluomet uron, N,N-dimethyl-N'-[3-(trifluoromethyl)phenyl]-urea; vetch, Vicia v illosa L.