example that can cause crop losses. Excessive boron can be introduced with feedstocks like coal ash and cellulose insulation, etc. Much already has been done in the U.S. to prevent these toxicity problems. Compost standards will resolve these issues. Compost should be tested for specific minerals if the mix of feedstocks indicates that phytotoxic concentrations may result. High pH Perhaps the worst chronic problems are caused by lime-stabilized composted sewage sludges or compost products that have been treated with minerals that gradually increase the pH of treated soils. These problems often are not detected in blends of composts containing materials that gradually raise the pH. Although many agricultural crops benefit from liming, most landscape plants do not and prefer a soil pH of 5-6. Lime stabilized products should be applied at rates that do not exceed the need for the crop and this frequently is not realized until it is too late. It is all but impossible to lower the pH of some affected soils and crop failure is the result. In summary, only purchase composts if performance data are supplied as well.
Answer by: Harry Hoitink, professor of plant pathology, Ohio State University, and Robert Rynk, BioCycle.