Competitiveness and Yield Loss Prediction of Water-seeded Rice by Densities of Scirpus juncoides Roxb

Abstract

This study was conducted to predict the rice yield loss and determine the economic threshold levels for water direct seeded rice from competition of the most serious weeds, Scirpus juncoides Roxb. (bulrush) and Echinochlor crusgalli L. (barnyardgrass) in Daegu of Korea. To predict crop yield as a function of weed density used a rectangular hyperbola, and determine their economic threshold levels used the equation developed by Cousens. The rice yield loss model of S. juncoides was predicted as y = 466 / (1+0.00188x), R 2 = 0.933 and that of E. crusgalli was y = 458 / (1+0.02402x), R 2 = 0.973. In comparison of the competitiveness represented by parameter β, it was 0.001884 in S. juncoides and 0.02402 in E. crusgalli. Economic threshold calculated using Cousens' equation was negatively related to the competitiveness of weed. So that the economic threshold of S. juncoides was 13.4 and that of E. crusgalli was 1.07 plants per m 2 .

Prediction of Rice Yield Loss by Aneilema keisak and Aeschynomene indica Competition in Flooded Direct-Seeded Rice

“…al., 2006;Song et. al., 2006;Won et. al., 2010) 담수직파재배에서 사마귀풀과 자 귀풀 발생밀도에 의한 벼 수량감소를 예측한 결과는 보고 되지 않았다.…”

“…al., 2006;Song et. al., 2006;Won et. al., 2010) (Lee, 2006;) 건답직파재배에서는 파종 후 70일에 사마귀풀은 경 합밀도가 m 2 당 5~100본일 때 4~34%정도 감소되었다고 보 고 (Cho et.…”