Common root rot is a major disease of commercially grown snap bean (Phaseolus vulgaris L.) on the irrigated sandy soils of central Wisconsin. The objective of this study was to determine the relationships between soil properties and suppressiveness to common root rot of snap bean (causal agent Aphanomyces euteiches) in soils. The soils had been annually amended for three years in a field trial on a Plainfield sandy loam in Hancock, WI. Soils were amended each year from 1998 to 2001 with three rates of fresh paper-mill residuals (0, 22 or 33 dry Mg ha�����) or composted paper-mill residuals (0, 38 or 76 dry Mg ha�����). Soil was removed from each treatment in April (one year after last amendment) and brought to the laboratory. This was repeated with a field soil sample taken in September, 2001. The soils from the two samplings were incubated at room temperature and periodically assayed (days 9, 44, 84, 106, 137, 225 and 270 for April sampling) (days 13, 88 and 174 for September sampling) for suppressiveness of snap bean root rot (0 to 4 where 0=healthy and 4=dead plant). The same days, incubated soils were characterized for ��-glucosidase, arylsulfatase and fluorescein diacetate activities; microbial biomass C (by chloroform fumigation); water stable aggregation (WSA) and total C. In the first incubation, there were large differences between field amendment treatments in terms of snap bean root rot incidence. The disease was suppressed by both fresh and composted amendments, but compost was most suppressive at high compost rates with disease incidence <40% which are considered healthy plants that can reach full yield potential. In the second incubation, disease severity difference among treatments were similar to the first incubation. This would indicate the suppression was induced prior to initiation of this experiment. Disease severity of bean plants grown in unamended field soil was high but in amended soils tended to decrease in intensity over time. Root rot severity was negatively related to ��-glucosidase, and microbial biomass at the beginning and the end of the first incubation period, respectively. FDA hydrolysis was not correlated with disease severity and WSA moderately correlated with disease. The best indicator of disease severity was arylsulfatase which was significantly and negatively correlated with disease severity in 4 of 5 sampling periods. / Graduation date: 2003