An Optimum Control Time of Alopecurus aequalis var. amurensis Ohwi in No - tillage Dry Seeded Rice

벼 무경운(無耕耘) 건답직파재배시(乾畓直播栽培時) 둑새풀 방제적기(防除適期) 구명(究明)

  • Hwang, C.D. (National Yeongnam Agriculture Experiment Station, RDA.) ;
  • Park, S.T. (National Yeongnam Agriculture Experiment Station, RDA.) ;
  • Kim, S.Y. (National Yeongnam Agriculture Experiment Station, RDA.) ;
  • Lee, K.Y. (National Yeongnam Agriculture Experiment Station, RDA.) ;
  • Kim, S.C. (National Yeongnam Agriculture Experiment Station, RDA.)
  • Received : 1997.10.29
  • Published : 1997.12.30

Abstract

A field experiment was conducted to determine an optimum control time of water foxtail(Alopecurus aequalis var. amurensis Ohwi), a most troublesome weed, in no-tillage dry seeded rice. Paraquat, a non-selective herbicide, was applied at 1.5 days interval from March 15 to May 15 at a concentration of 3,000ml per hectar and its control efficacy to A. aequalis was recorded before and after seed sowing. In addition. other characters such as decayed injury of A. aequalis to rice seedling, and its influence of seedling stand were also investigated in relation to rice grain yield. Dry weight of A. aequalis was rapidly increased with delay in control time from 42g/$m^2$at March 15 to 237g/$m^2$ at May 15. The amount of its regrowth at seeding time was highest with 68.3g, when paraquat was applied at March 15, then decreased thereafter and it was less than 6.2g when paraquat was applied after April 15 which indicates above 98% control rate. The control rate of A. aequalis, at 30 days after paraquat application way likewise similar to that the seeding time. Rice seedling stands in the plot treated with paraquat before April 15 were not affected by decayed injury of A. aequalis while decayed injury of 3 to 4 degree for those after April 30 application was noted. Dwarf virus disease on rice seedling due to occurrence of A. aequalis was not observed when A. aequalis was controled from March 30 to May 15 while it was occurred in the plot of March 15 application and the untreated control. The control plot of A. aequalis at April 15 had the highest grain yield with 4.79ton/10a. Based on control rate of A. aequalis, seedling stands of rice, virus disease, and rice grain yield, the most suitable control time of A. aequalis in no-tillage dry seeded rice is considered to be about April 15.