A 2-yr field study was conducted to evaluate the response of rice to rotational crop herbicides in combination with rice herbicides in water-seeded culture. Fluometuron, imazethapyr, metolachlor, and norflurazon were applied at 0.5, 0.25, 0.125, and 0.063 times the recommended use rates preplant incorporated (PPI) to simulate herbicide carryover from previous crops. Molinate and thiobencarb at 4.5 kg ai/ha were applied PPI, and quinclorac at 0.43 kg ai/ha postemergence. No interaction between rice herbicides and rotational crop herbicides was observed for rice injury at 4 wk after planting (WAP), plant dry weight, stand, and height at 8 WAP, or rice grain yield. However, rice heading was delayed with some rotational crop herbicide and rice herbicide combinations. Fluometuron at the 0.5 and 0.25× rates injured rice 64 and 21% at 4 WAP, and reduced rice yield 96 and 20%, respectively. At 4 WAP, metolachlor at the 0.5 and 0.25× rates injured rice 93 to 29%, and reduced rice yield 85 to 20%, respectively. An 84 to 100% rice injury at 4 WAP and a 81 to 100% rice yield reduction were observed with norflurazon at the 0.5 and 0.25× rates, respectively. Imazethapyr caused 15 to 26% rice injury 4 WAT and 22 to 41% yield reduction.
Nomenclature: Fluometuron; imazethapyr; metolachlor; molinate; norflurazon; quinclorac; thiobencarb; rice, Oryza sativa L. ‘Maybelle’.
Additional index words: Herbicide interaction, simulated herbicide carryover, water-seeded rice.
Abbreviations: POST, postemergence; PPI, preplant incorporated; PRE, preemergence; WAP, weeks after planting.