Carpetweed (Trianthema portulacastrum L.) and barnyardgrass (Echinochloa colona L.) control in soybean (Glycine max).

Field experiments were conducted during rainy seasons of 1993 and 1994 to evaluate the efficacy or soil and foliage applied herbicides on carpetweed and bamyardgrass in soybean. Pre-plant incorporation of tritluralin at 1500 g/ha provided an average 90% carpetweed and 80% harnyardgrass control. Pendimethalin at 1500 g/ha provided an average 87% carpetweed and 49%, barnyardgrass control. Chlorimuron at 12 and 24 g/ha gave better control of carpetweed when applied 20 days after sowing (DAS) rather than 30 DAS. The density and dry matter acculliulation by these two weeds exhibited similar response to tritluralin and chlorimuron rates Number of branches and pods per plant of soybean and consequently grain yield with trifluralin or pendimethalin each at 1500 g/ha were statistically at par with weed free situations. Chlorimuron at 12 and 24 g/ha caused 15 to 25% soybean yield reductions due to its phytotoxicity.