This research was conducted in Teutônia, RS, during 1990 of a Purple Structured (Paleudult) Soil. Four areas were submitted to different soil tillage sistems (no till, conventional and natural forest). The number of oligochaetes per area was counted and identified and water stable agregates for each season of the year was determined. The average geometric diameter of the water stable agregates was greater under forest and no tillage. Little variation was observed on the distribuition of water stable agregates for the different soil tillage systems and seasons. The largest oligochaetes populations were observed under no tillage and the majority of the individuals beonged to the genus Pheretima.
oligochaeta; average geometrical diameter; tillage systems; agregates
