Basis for the Control of Soilborne Plant Pathogens with Composts

Environmental problems caused by disposal of organic wastes in landfills and streams or by incineration have forced man to examine alternative procedures. For example, burning of tree bark was a nuisance because of associated air pollution problems. This waste has now been turned into a resource through development of profitable composting processes and efficient energy retrieval systems. S ludges are removed from waste waters at a major cost to taxpayers and industries to reduce pollution of streams. Compo sting is chosen in­ creasingly as the least objectionable treatment process for these wastes; thus sludges provide another type of compost. Finally, with the increase in size of farms, the composting process has become a practical procedure for treatment of manures because it allows storage of a stabilized product until a time of year when its market value is highest. I n China, Japan, and other parts of the Orient, composts have been used in agriculture with beneficial effects for years (58). In the West, however, utilization of composts is a relatively recent phenomenon. During the past two decades several reports have discussed suppressive effects of composts to a variety of soilborne plant pathogens. Most of this literature is on ornamental crops. Only a few diseases of vegetable and field crops are controlled with