To evaluate herbicide phytotoxicity in rice, rice plants were
counted at 14 DAS from four randomly selected 1-m row lengths in
each plot and the reduction (%) in plant stands was calculated by
comparing with the non-treated check. The non-uniformity of
plant establishment due to herbicide toxicity was determined as
the coefficient of variation of means of the 12 rows (4 rows 3
replicates) for each treatment combination. To evaluate the performance
of herbicides on individual weed species, weed density
and weed biomass were measured at 40 DAS by randomly placing
two quadrats, measuring 40 cm by 40 cm, in each plot. Weeds were
separated by species, counted, and their biomass was measured
after oven drying the samples at 70 C for 72 h. To evaluate the
effect of weeds on rice, weed and rice biomass were measured from
two 40 cm by 40 cm quadrats at 50% flowering. At harvest, rice
panicles were counted from four randomly placed 1-m row lengths
in each plot. Rice grain yield was determined from a harvested area
of 4.0 m 2.2 m. Grain yield was converted to t ha1 at 14%
moisture content.