Rice response to fluridone following topsoil removal on a precision-leveled field

Furrow-irrigated rice (Oryza sativa L.) production requires additional management options without the cultural strategy of a flood. In 2023, fluridone (Brake) was registered for use in rice production. Precision-leveling land is an important aspect of maintaining an effective irrigation flow path; however, the removal of topsoil can severely impact crop response from residual herbicides. The objective of this study was to evaluate the impact of fluridone on rice response when applied to a precision-leveled field following topsoil removal. An on-farm field study was conducted in 2023 near Osceola, AR, with a Sharkey-Steele clay complex soil texture. The study consisted of six herbicide treatments applied at the rice three-leaf stage. These treatments included clomazone, quinclorac, and fluridone at three rates (0.5×, 1×, and 2× of a label rate) and a nontreated control. Across evaluation times, maximum visual rice injury was greater than 25% and 65% for the fluridone 1× and 2× treatments, respectively. Rice canopy coverage was reduced in the fluridone 1× and 2× treatments compared to all other treatments from 6 to 10 weeks after application (WAA). Rice heading in the fluridone 2x treatment was delayed by more than 60 and 30 percentage points at 11 and 12 WAA, respectively, compared to all other treatments. Rough rice yield in the fluridone 2× treatment was reduced by 21% compared to all other treatments. Overall, fluridone 1× and 2× rates caused substantial rice injury and would not be recommended on a precision-leveled field.