Weed Control in Dry Direct-Seeded Rice

The experiments were conducted to establish effective weed control methods and to screen promising herbicides in dry direct-seeded rice at the National Yeongnam Agricultural Experiment Station, National Crop Experiment Station and National institute of Agricultural Science and Technology from 1996 to 1998. Cyhalofop-butyl․bentazon ME, cyhalofop-butyl․pendimethalin EC and pyribenzoxim EC were very effective as foliar applied herbicides to control weeds (4～5 leaf stages of barnyardgrass) at 20～25 days after seeding (DAS) in direct seeding. Especially, cyhalofop-butyl․pendimethalin EC can also control barnyardgrass of 7～8 leaf stages by over 95% at application of over 1.5 double rate (7L per ha), but E. oryzicola among Echinochloa species at application of under 6 L per ha was partly revived. In dry seeded rice, permanent flooding is recommended when rice plants reach about 3～4 leaf stage but many farmers are practicing early flooding at 2～3 leaf stage (12 to 15 DAS) due to weed control problem. Accordingly, Treatment of single herbicide such as pyrazosulfuron․molinate GR, cyhalofop-butyl․azimsulfuron․molinate GR, pyrazosulfuron․mefenacet GR and chyalofop-butyl․pretilachlor․pyrazosulfuron GR at 2 days after early flooding (17 DAS) showed low control efficacy of 75～85% but systematic application of butachlor EC at 5 DAS followed by those above mentioned herbicides at 17 DAS displayed excellent control efficacy of 94～98% at 30 days and 91～93% at 60 days, respectively. In addition, the systematic treatments also could control troublesome weeds in dry direct-seeded rice such as barnyardgrass and marsh dayflower very effectively