本研究以生物檢測方法，偵測硫醯尿素類除草劑在水田田水中之殘留活性。依據藥劑對測試作物種子胚根伸長之50%抑制劑量，將作物歸類為耐、中、感三種藥劑忍受性等級；玉米及高粱高於400 ppb，綠豆及胡瓜在100 ppb上下，萵苣及甘藍低於 10 ppb。由中、感等級作物劑量反應趨勢所估算之50%抑制劑量理論值，與田區水樣之藥劑實測值頗為相近，但耐性作物反應則顯示理論值較實測值高估之結果。施藥後0-4日採集之水樣，噴施於2-3葉齡之測試植株，由受害程度、發生之起始天數及恢復天數結果顯示，萵苣及甘藍亦最為敏感，達到70-80%之受害程度，且0-2日之水樣會導致萵苣發生不可恢復之傷害。對藥劑有不同忍受等級之作物組，在特定除草劑處理下，胚根伸長受到明顯抑制之敏感品種，其植株亦表現出具有發生藥害之潛力。

Sulfonylureas are widely used in field crops for control of broadleaf weeds. In Taiwan, sulfonylureas are mainly registered and used in paddy field. This class of herbicide is merited with low application rate and low mammalian toxicity. However, strong activities and residual activities often result in phytotoxicity of non-target species. In these studies, we evaluated phytotoxicity potential of sulfonylureas on local crops and investigated the bioactivities of these herbicides in paddy water. Bioassay used involved planting pre-germinated seeds of tested species in filter papers soaked in herbicide solutions and measuring the radicle length after 5 days. I50 of pyrazosulfuron on radicle elongation enabled classification tested species into three response groups. Lettuce and cabbage, I50 less than 10 ppb, were highly sensitive; Cucumber and mungbean were moderate sensitive with I50 around 100 ppb; Corn and sorghum were tolerant showing I50 above 400 ppb. Water sampled from paddy field resulted in various degree of phytotoxicity when sprayed on seedlings of tested species. Lettuce and cabbage were injured severely by paddy water containing tested herbicides at 0-2 days after herbicides application. Sensitive plants showed symptoms of leaf chlorosis, leaf crinkling and reduction of leaf size. Residual activity in paddy water was highest at the day of application, and lasted for 4 days. It seemed injury occurred to test bioassay species, the potential existed for significant crop plants injury.