Pennsylvania Flower Growers #253
Treatment of soil with free-flowing (212°F) steam has been the most efficient and practical method of eliminating soil borne plant pathogens, insects and weed seeds. However, it has been known for many years that steam treatment of soils can produce conditions which are toxic to certain plants. The many articles that have been published on post-steaming toxicity lead one to conclude that many injurious agents are involved. These agents include an increase of total soluble salts and water-soluble organic matter, modified capacity of the soil for water, gases and salts and accumulation of ammonium and avail able manganese. Total Soluble Salts Soils which are reused tend to accumulate unused salts. When these soils are steamed, some of these salts go into solution more readily because of the high temperature and moist conditions. If there are sufficient quantities of these salts they are toxic. Most type of animal wastes and many organic composts, particularly mushroom composts, contain large quantities of salts which are released by steaming. Leaching is the most common method used in removing soluble salts.
Keywords: Total Soluble Salts Water-Soluble Organics Modified Physical Characteristics Ammonium Accumulation Manganese Accumulation