2007年夏季嘉義試驗分所之甘藷試驗田發生的雜草種類計有15科28種，主要以菊科及禾本科的種數較多，各有6種，約佔全部種數的43%。休耕期間試驗田雜草種類只有10種，以馬齒莧佔絕大多數，亦有香附子發生，其他僅佔少數，顯示馬齒莧是試驗田休耕期間之優勢雜草。根據土壤種子庫在夏季分析調查的結果顯示有15種雜草發生，除了馬齒莧之外，其次是碎米莎草，而禾本科的牛筋草、芒稷和馬唐亦有較高的比例。因試驗期間正值夏季高溫期，田間雜草之密度及生物量，以C4型雜草佔絕對優勢，以牛筋草、馬齒莧、刺莧、及碎米莎草為多。本試驗比較甘藷田常用之萌前除草劑拉草(alachlor)及植保手冊推薦使用之滅草胺(metazachlor)除草效果，結果顯示皆可有效抑制雜草萌發，二種藥劑尤其滅草胺對牛筋草的效果最為顯著。部份雜草雖在第三至四週後陸續再萌發，此時除草劑藥效已逐漸消褪，但仍使生長勢緩慢，因甘藷種植一個月後有中耕培土措施，雜草的威脅亦相對減少。根據藥劑施用後4週之調查結果顯示二種萌前除草劑對雜草的防治效果均佳，在甘藷中耕培土之前，可以抑制雜草大量發生，減少雜草對甘藷的養分等競爭。此外，亦可見滅草胺對禾本科和莧科雜草的防治效果較拉草顯著，但對小葉灰藋和馬齒莧的效果則不如拉草。

Investigation of weed flora in sweet potato field at Chaiyi in 2007 found that 28 weed species, 15 families, occurred in summer, and both Compositae and Gramineae were two dominant families. During the period between two crop seasons, there were only 10 weed species appeared and the major one was Portulaca oleracea. Soil seed bank assay conducted in summer showed existence of 15 weed species, included P. oleracea, Cyperus iria, Eleusine indica, Echinochloa colona, and Digitaria adscendens. Comparing the efficacy of two preemergence herbicides, alachlor and metazachlor, weeds were controlled successfully, and the later one was more effective to control E. indica. Although some weeds rebuilt gradually three weeks later and herbicide effect diminished with time, routine work of field management within one month after transplanting was able to control weeds.