[[abstract]]嘉義農業試驗分所與國際稻米研究所合作，於民國 53 年第二期作舉辦水田殺草劑治草試驗，應用十三種不同配合之殺草劑，從事水田治章效果觀察，玆將初步所得結果，簡述於後： Ametryne與Simetryne殺草效果最佳，尤對紫背浮萍，青萍及田字草等水生濶葉雜草，具有特效。惟一般殺草劑對大株雜草效果較差，Propanil在本試驗之治草效果最差。 Ametryne，PCP與Simetryne對水稻毒害較強，MCPCA有抑制水稻發育現象，僅Propanil和Swep對水稻未有毒害作用。 水稻生育初期，稻田雜草大都為水生濶葉草，中、後期則以稗草類之雜草為最多，水生濶葉草在水稻生育後期逐漸自滅，故收穫前所得雜草乾重以稗草所佔比例最大，而三稜葱草，鴨舌草及水蜈蚣等所佔比例較少。 雜草叢生可促進水稻抽穗，但對每穗粒數似有減少之趨勢，水稻受殺草劑強性毒害則延遲抽穗。殺草劑可抑制水稻生育早期之株高及分蘗，但不影響穗長，千粒重。 DBN , MCPCA , PCP , Swep , Simetryne , Hydram 以及 Swep + MCPA 處理區稻谷產量超過慣行除草區。 DBN 處理區每公頃產量較慣行除草區多出 563 公斤（12%）比不除草區高1,320公斤（34%），後者差異達1%顯著值，不除草處理比慣行除草者減產757公斤達19%，其差異遠超5%顯著水準，由此概見水田雜草為害，使稻谷減產之一斑。 Ametryne 因具有強性毒害，致使部份水稻被害，呈顯缺株，其產量乃受影響。 Field investigation was made on the second crop (wet season) of 1964 at Chiayi Agricultural Experiment Station to evaluate the effectiveness of 13 herbicides and herbicide mixturers together with weedy and weeded checks for controlling weeds in rice. A total of 15 treatments were arranged in randomized complete blocks with four replications. The effects of herbicide treatments on rice were evaluated by weed counts, cover estimates, weed control ratings, phytotoxicity estimates, weed weight, agronomic eharacters and grain yield. Some findings of this investigation may be summarized as follows: Ametryne and Simetryne gave best control of weeds, particularly of aquatic floating broadleaves which were apparently not killed by other chemicals. When weeds, especially grasses were rather large at time of treatment, they were not controlled by PCP-Na, MCPA and 2, 4-D. Propanil gave poor control of weeds under the conditions of this experiment. Rice was injured severely by Ametryne, PCP-Na and Simetryne. MCPCA was also found to have certain inhibitory effects on the growth of rice. Propanil and Swep were not toxic to rice under flooded condition. Broadleaved weeds, especially those of aquatics dominated the weed population of the experimental plots at the early stage of rice growth, but their position was apparently taken over by grasses at the late stage. The change in weed population was clearly reflected in weed weight which was primarily contributed by grasses. Sedges were not an important problem. Weeds hastened the heading of rice while chemical injury delayed it. Plant height and tillering ability of rice was significantly reduced at the early stage of growth. Panicle length and grain weight were not affected by herbicide treatments but weeds seemed to reduce number of grains per panicle. DBN, MCPCA, PCP-Na, Swep, Simetryne, Hydram and a mixture of Swep+ MCPA produced more grain yields than weeded check. DBN yielded 563 kg or 12.0% more than weeded check and 1,320 kg or 33.6% more than weedy check, the latter being significant at 1% level. Weedy check reduced grain yield by 757 kg or 19.3%, a difference exceeding the 5% level of probability, when compared with weeded check, indicating a serious loss of yield by weed competition. Ametryne gave the lowest yield due to the reduction of stands caused by its toxicity to rice.