THRESHOLD LEVEL OF WEEDS IN WET-SEASON TRANSPLANTED RICE (ORYZA-SATIVA)

An experiment was conducted during 1988 and 1990 to determine minimum weed density of mixed weed population beyond which control measures ar e essential for wet-season transplanted rice (Oryza sativa L.) Hoorah grass [Fimbristylis miliacea (L.) Vahl] was the most dominant weed. Ho orah grass and bog bulrush (Scripus mucronatus L.) represented 60-80% of the total weed population. The weeds reduced grain yield of rice by 7-25%, depending on the density. Weed density @ 17-42 weeds/m2 with 1 4.1-22.3 g/m2 dry-matter accumulation by weeds reducing the grain yiel d by 10%.