Soil steam sterilization

Soil steam sterilization (soil steaming) is a farming technique that sterilizes or partially sterilizes soil with steam in open fields or greenhouses. Steaming leads to a better starting position, quicker growth and strengthened resistance against plant disease and pests. In recent years soil steaming has regained popularity. It is now considered the best and most effective way to disinfect sick soil, potting soil, and compost.

Steam effectively kills weeds, bacteria, fungi and viruses by heating the soil to levels that cause enzyme inactivation or the unfolding and coagulation of vital cellular proteins. Soil steaming is considered a good alternative to bromomethane, whose production and use was curtailed by the Montreal Protocol. Biologically, soil steaming is considered a partial disinfection, since heat-resistant spore-forming bacteria can survive the process and revitalize the soil after cooling.

Soil steaming is also effective for addressing soil fatigue, which is the degradation of soil health and fertility arising from improper agricultural management practices. Steaming the soil has been shown to effectively release nutritive substances blocked within fatigued soil.

Methods like "integrated steaming" can promote a target-oriented resettlement of steamed soil with beneficial organisms. In the process, the soil is first freed from all organisms and then revitalized and microbiologically buffered through the injection of a soil activator based on compost which contains a natural mixture of favorable microorganisms (e.g. Bacillus subtilis, etc.).

In the laboratory, soil steam sterilization via autoclave is an important step in agricultural research, specifically into regenerative agriculture, permaculture, and some ex situ cryopreservation. This process achieves true sterilization, completely disinfecting the soil and rendering all microorganisms, spores, viruses, fungi, and pathogens entirely inactive.