Rates of 0 and 5 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) or 2-chloro-4,6-bis(ethylamino)–s-triazine (simazine) were combined with O and 200 lb/A of nitrogen fertilizer as preemergence applications on plots planted to corn (Zea mays L., var. Mo. 880) in May of 1964 and 1965. Soil samples collected in December, 1965, and again in February, 1966, were plated on Difco potato dextrose agar and nutrient agar to determine the growth of fungal and bacterial colonies. There was no difference in the total number of fungal colonies grown on media seeded with soils from the field studies, yet variation in individual species occurred. The number of bacterial colonies increased on plates seeded with soil from plots treated with 200 lb/A of nitrogen plus 5 lb/A of simazine but not from simazine-treated soil without nitrogen.