本試驗採用四種殺草劑：krovar I, glyphosate, dalapon及paraquat,於1977年三月至1979年四月，分八次噴洒以殺柑桔園之雜草。並在各次施藥前後採土樣若干次，於實驗室中測定土壤中之細菌與真菌之總數、硝化菌類Nitrosomonas與Nitrobacter之概數。在最後一次施藥前後更測定土壤中之蔗糖分解酶與酸性解磷酶之活性。試驗結果顯示，上述各項微生物含量及活性均因採樣時間不同而有差異，且施藥組與對照組均在一定之範圍內起伏。此等變化似非由殺草劑之施用所引起，而可能為自然環境變遷之影響。

Herbicides krovar I, glyphosate, dalapon and paraquat were applied 8 times to control the weeds in a citrus orchard during the period of March, 1977 to April, 1979. Soil samples were taken for microbiological analyses, before and after each application from the four treated and two control soils, i.e. a hand weeding and an unweeding areas. The analyses included total counts of bacteria and fungi, and most probable numbers of nitrifying bacteria. Shortly before and after the final application, invertase and acid phosphatase levels were also assayed in addition. The results show that the microbial populations changed at various sampling dates; however, the changes were within the same ranges. The enzymes levels also changed similarl y . It is like I y that the changes were caused by the environmental factors rather than the effect of the herbicides.