Toxicity to Seedlings of Nitrite in Sterilized Composts

SummaryThe nature of damage to seedlings growing in heat-sterilized composts, usually attributed to high levels of ammonia, was studied. Use of a nitrification inhibitor showed that high levels of ammonia did not damage antirrhinum seedlings in the absence of nitrite. Toxicity occurred only in the presence of nitrite which, when the inhibitor was not added, formed after the accumulation of ammonia.Methods of controlling soil levels of ammonia and nitrite by inoculating with various combinations of Nitrosomonas and Nitrobacter cultures were studied, but the conditions for maintaining low concentrations of both NH3 and NO2+ were critical.