Abstract: Research was conducted to determine the effects of tillage on fluometuron and norflurazon loss in runoff when applied preemergence in cotton. Cumulative water loss and norflurazon and fluometuron concentrations in runoff were not affected by tillage systems. In 1992, the no-till system had less sediment loss in runoff than the conventional tillage system. Tillage systems did not affect sediment loss in 1993. The highest amount of total fluometuron loss occurred with the conventional tillage system in 1992, whereas the reduced tillage system had the lowest amount in 1993. There were no differences in cumulative norflurazon loss between tillage systems in 1992, and as with fluometuron loss, norflurazon loss in runoff was less with the reduced tillage system in 1993. This research indicates that, while conservation tillage may reduce sediment loss, it may not necessarily be the best management tool for decreasing the loss of herbicides in runoff.

Nomenclature: Cotton, Gossypium hirsutum L. ‘DES 119’.

Additional index words: Conventional tillage, no-till, rainfall simulation, reduced tillage, stale seedbed, surface runoff.

Abbreviations: CT, conventional tillage; DAT, days after herbicide treatment; GC, gas chromatography; HPLC, high-performance liquid chromatography; K_oc, soil organic carbon sorption coefficient; NT, no-till; RT, reduced tillage.