A field study was conducted in 2002 and 2003 to evaluate tolerance of eight rice cultivars to clomazone at 896 g ai/ha impregnated onto urea fertilizer. Rice foliar bleaching was 16 to 20% at 14 d after rice rooting (DAR) for long-grain cultivars ‘Ahrent’, ‘Cheniere’, ‘Cocodrie’, ‘Cypress’, ‘Francis’, and ‘Wells’ and 23 and 30% for medium-grain ‘Bengal’ and short-grain ‘Pirogue’, respectively, when clomazone was impregnated onto urea. Clomazone reduced the number of tillers/ m2 21 DAR for all cultivars. Early season height reductions occurred for all cultivars; however, Pirogue was the only cultivar shorter than the nontreated at harvest. There were no yield reductions with regard to the medium and long-grain cultivars when compared with respective nontreated cultivars. However, yield of short-grain Pirogue treated with clomazone was 1,740 kg/ha less than the nontreated.
Nomenclature: Clomazone; herbicide-coated fertilizer; rice, Oryza sativa L., ‘Ahrent’, ‘Cheniere’, ‘Cocodrie’, ‘Cypress’, ‘Francis’, ‘Wells’, ‘Bengal’, ‘Pirogue’.
Additional index words: Herbicide tolerance.
Abbreviations: DAE, days after emergence; DAPRE, days after preemergence; DAR, days after rice rooting; DAT, days after treatment; DPRE, delayed preemergence; ME, microencapsulated.
