Quizalofop-p-tefuryl Application Rates and Timing in Straw Burning and No-Burning Soybean Grown After Rice

Abstract

Field experiment was carried out from December 1995-May 1996 at Chiang Mai University to determine the efficacy of herbicide quizalofop-p-tefuryl [(±)-tetrahydrofurfuryl(R)-2[4-(6-chloroquinoxalin-2-yloxy)propanoate] on annual grass weed control in straw burning and no-burning soybean grown after rice. Glyphosate (N-(phosphonomethyl)glycine) was treated to general weeds at the rate of 2.0 kg(ae)/ha 7 days before planting in no-buning plot, rice straw and general weeds were burned at 7 days before planting in burning plot. Quizalofop-p-tefuryl at the rate of 45 and 60 g (ae)/ha was applied for annual grass weed control 21 dnd 38 days after soybean planting. It was found that soybean and weeds in the straw burning plot were able to emerge and grow better than that of no-burning plot. Quizalofop-p-tefuryl at the rate of 45 g (ae)/ha showed excellent control of annual grass weeds; Digitaria adscendens, Echinochloa crus-galli and Eleusine indica in no-burning plot when applied at 21-38 days after planting. In the straw burning plot, the annual grass woods were effcctively controlled by quizalofop-p-tefuryl at the rate up to 60 g(ae)/ha when applied at 21 days after planting. If applied at 32 days after planting, the rate of herbicide was needed more than 60 g(ae)/ha. Quizalofop-p-tefuryl caused slight phytotoxicity in soybean after application. The use of quizalofop-p-tefuryl for annual grass weed control produced significantly higher soybean grain yield when compared to non-treated plot.