模擬溫暖化情境對水稻田雜草相之變化及其管理

Abstract

水田雜草族群的變動受稻作生產環境影響甚大，氣候條件及栽培管理等改變皆能使雜草相消長呈現動態分布，尤其隨著全球溫暖化情境，此一動態變化料將持續發展，而且亦將影響雜草與水稻間的競爭關係。本研究藉由不等栽植期來模擬暖化情境，藉由調查雜草在不同氣象條件下之生長，探討在溫暖化環境下溫度、日照時數及日射量對水稻田雜草相之異動。經分析雜草科別數、種別數及密度與氣象變因之關係後發現，雜草數量明顯隨著累加溫度及日射量的增加而上升(P < 0.05)，因此可預期水稻田雜草族群將在高溫及高日射量下快速繁衍。又發現其中闊葉類雜草較尖葉類雜草適應高溫，推估將有可能成為暖化趨勢下水稻田的優勢雜草種類，吾人對此雜草種類需要多加注意。經選取雜草種類分布最多的2個栽植期探討不同溫度梯度下之雜草管理，綜合試驗結果建議，一期作立春(SS)栽植期可於插秧後7週前、二期作大暑(MS)栽植期可於插秧後6週前進行雜草管理措施，將可減少雜草干擾對稻株生長的影響。 Changes in population and density of weeds in paddy field are influenced by growth environment, as well as climatic conditions and management practices. The dynamic variation of weeds in paddy field will continue under global warming trend and will be affecting their competition with rice. By using different cropping seasons to mimic warming trend scenario, this study was aimed at investigating effects of air temperature, sunshine hour and irradiance on changes in population and density of weeds in paddy field. Results showed that weed density increased with increasing accumulated values of daily mean air temperature and daily irradiance (P < 0.05) so that weeds propagation in paddy field can be expected to be increased under the conditions of warming temperature and high irradiance. Numbers of broadleaf weeds were higher than those of narrowleaf weeds under warming conditions and therefore may become dominant weed species in paddy field that need to be taken into account in the future. By selecting two cropping seasons (SS and MS) that had more weed distribution in the fields for weed management experiments, results indicated that weeding before 7 weeks after transplanting would reduce weed influence on rice growth for the cropping season of ‘Lichun’ (SS), while it was before 6 weeks after transplanting for the cropping season of ‘Dashu’ (MS).