SUPPRESSION OF SEEDLING DAMPING-OFF DISEASE IN POTTING MIX CONTAININGANIMAL MANURE COMPOSTS

Broiler litter, dairy manure, and steer/horse manure were separately c ocomposted with other organic residues, and the resulting composts inc orporated into potting mixes. All the compost-amended potting mixes we re suppressive to damping-off caused by Pythium and Rhizoctonia relati ve to disease conducive controls. The type of manure in the compost ha d a greater influence on damping-off of Pythium than of Rhizoctonia. C omposts differed in the relative amounts of suppression of Pythium dam ping-off as follows: dairy manure greater than or equal to steer manur e 2 poultry litter. However, dairy manure compost contained phytotoxin s generated in anaerobic zones of the windrow. There was no statistica lly significant association between disease suppression and compost ag e. Comparisons between disease losses in nonautoclaved and autoclaved potting mixes provided evidence that disease suppression was microbial ly mediated. There was also some evidence that low levels of NO2- - or NO3- - nitrogen were associated with suppression of Pythium damping-o ff.