本研究係於1993年二期作及1994年一期作在臺灣省農業試驗所農場進行田間試驗，以探討水稻對稗草生長及繁殖之抑制效應。水稻行株距為0.3×0.5m，稗草植株採相同行株距以1：1比率插植於水稻行間，另以全區栽植稗草植株者為對照。根據試驗結果，當同時生活在可相互影響的空間內，稗草將因水稻的競爭受到生長限制。對二期作而言，水稻的壓制效應於稗草生育早期即已呈現，一期作則彰顯於生育後期，包括葉片重，莖稈重、及穗重均低。收穫時，一期作之稗草穗重明顯下降。由(葉片/莖`稈)重量比得知，在無水稻壓制狀況下稗草生育期間莖稈增加速率高於葉片，尤其自移植至水田後30天起快速累增。惟在二期作生育早期，稗草因水稻的競爭而大量生產葉片。結果亦顯示，水稻的競爭壓力似能促進稗草穎果的生產，尤以二期作者顯著。對照植株穎果生產量則以一期作之稗草較高。

Field experiments were conducted in the experimental farm of Taiwan Agricultural Research Institute to study the suppressing effect of rice (Oryza sativa L. cv.Tainung NO.67) on growth and productivity of barnyardgrass [Echinochloa crus-galli (L.) Beativ.] plants of Barnyardgrass were grown interlined to rice with the same plant distance and in the ratio of 1:1,and with pure stands as checks in the second crop of 1993 and the first crop of 1994. It was shown that generally growth of barnyardgrass was suppressed by rice when grown together in the paddy field. Rice exerted a strong suppressing effect from the early growth stage for the second crop while such effect became significant in the later growth stage for the first crop. Dry weights of leaves, sheaths (with stems) and panicles (with caryopses) were decreased by the competition of rice during growing period. At harvest, the suppression of panicle weight of barnyardgrass was significant only in the first crop. Productivity of sheaths was higher than of leaves in barnyardgrass without the competition of rice as indicated in the decreasing leaf sheath weight ratio. The proportion of sheaths to leaves increased greatly from 30 days after transplanting.When competed with rice in the second crop,barnyardgrass built up their leaves significantly in the early growth stage. Barnyardgrass was tended to produce more caryopses in competition with rice, especially in the second crop. Without rice competition, the reproduction capability was prevailing in the first crop.