The Effect of Weeds on Rice in Paddy Field (III). Time of Weed Eradication

Abstract

The effect of time of weed eradication on rice was evaluated in both crops in 1970. Average percentages of yield reduction recorded for the first, eradications of weeds were 0, 16.7, 29.4, and 51.6%, respectively.Weeds eradicated at 15, 30, 45, 60, and 10. 20, 30, 40 days after transplanting in the first and second crops reduced yield by 0% , 1.2%, 12.2%, 38.9%, and 8.2%, 32.3%, 46.7%, 64.3%, respectively. Mnochoria vaginalis cused more damage to rice if early eradication was not made while Echinochloa crusgalli and Cyperlts difforims rednced rice yield more severely when they were eradicated until late growing stage of rice. The damage of weeds eradicated at early growing stage of rice appeared heavier in high fertilizer treatment. The time of the weed eradication affected the number of panicles per plant and the number of grains per panicle but not the weight of 100-grain and the percentage of fertility. 嘉義農業試驗分所繼續於民國59年第1、2期作在網室內調查三種之主要水田雜草不同拔除時期對水稻為害之情形。初步結果顯示，第1、2、3與4四種不同處理之雜草拔除時期分別減產稻谷、0、16、29.4與51.6％。第1期作在插秧後15、30、45與60日拔草，而第2期作則在插秧後10、20、30與40日拔草時，分別減產0、1.2、12.2與38.9及8.2、32.3、46.7與64.3％。鴨舌草若不在早期拔除時為害較大，而稗草與三角草則延至後期拔除時較易造成嚴重為害。一般言之，雜草之為害以重肥區較為嚴重。雜草拔除時期之早晚只為害每株穗數與每穗粒數，而百粒重與稔實率則不受影響。