Effects of composts and soil amendments on soil microflora and Phytophthora root and crown rot of bell pepper

Three field tests were established at Boynton Beach, Florida during 1992-1995, to evaluate various composts and soil amendments incorporated into the top 20 cm of beds for control of Phytophthora root and crown rot of bell pepper caused by Phytophthora capsici. Test plots were treated with one of the following: chitosan, crab shell waste, humate, municipal solid waste, perennial peanuts, seed peanuts, sewage sludge-yard trimming (SY), and wood chips. Untreated plots served as controls. Soil populations of five microbial functional groups and total microbial activity were monitored by measuring fluorescein diacetate hydrolysis analysis. Two plantings (11 September and 16 November 1995) of cv. Boynton Belle were evaluated in each test. Chitosan (0.2%, w/v) reduced disease incidence and severity compared with controls in one test. Perennial peanuts reduced disease incidence and severity of Phytophthora root and crown rot in another test. Several treatments, especially SY and wood chips, increased total microbial activity and soil populations of certain microbial functional groups, some of which were negatively correlated with disease incidence and severity.