Soil sterilization. I.—Ammonia and nitrate production in some glasshouse soils following steam sterilization

Ammonia production and subsequent nitrate formation have been followed in several types of glasshouse soils after partial sterilization by steam. If soil is steamed in situ and left undisturbed ammonia production continues for a considerable time and nitrate formation is negligible, despite the fact that the soil is open to any aerial and other fortuitous infections. If the same soil is incubated in bulk after steaming and disturbed periodically by sampling, ammonia concentration falls comparatively quickly and nitrification proceeds rapidly. This method of sampling apparently stimulates nitrification and has the same effect as deliberate contamination of the steamed soil by unsteamed soil. Results are adduced to show that a second or subsequent steaming is not so effective as the first one in stimulating ammonia production. There is some evidence that increase in ammonia production is accompanied by a reduction in the nitrate concentration at the same time.