Soil-Steaming and Steam-Boiler Blog – for healthy soil and plants

A special source of danger of reinfecting soil with pathogens after steaming is deeper soil. Depending on the root depths of the planted culture, phytopathogenic organisms can reach and contaminate deeper layers of soil. It can happen that steamed higher layers of soil are reinfected by such deep lying pathogens.

Hence when soil is heavily contaminated it is recommended to take soil samples from different soil depths depending on the root depth of the planted crop and check on diseases in order to identify the necessary steaming depth.

Furthermore the injection of beneficial active micro organisms after steaming into the soil can significantly strengthen the resistance against intruding pathogens and immensely inhibit recontamination.

The danger of recontamination on the surface by carry over e.g. when using foreign substrates or planting contaminated plants can be limited through the injection of beneficial microorganisms.

In contrast to other agents (such as air) water has the ability due to its high specific heat to absorb a tremendous amount of energy at a constant temperature of 100°C when transforming from water to steam. This energy is released in the soil for disinfection.

As a result this method obtains a particularly high degree of efficiency with which all organic pathogens are killed at sufficient time of exposure.

Due to the relatively low temperatures of just up to 100°C during the condensation process, soil is prevented from damage. In contrast to the usage of dry heat (e.g. hot air) soil can not be burned and its fertility harmed.
Compared to other chemical agents, water vapor has a comprehensive sterilization effect on soil. All organic pathogens are affected by the humid heat and even killed after sufficient exposure.

Chemical agents only partially take effect, since they are focused on single pathogens only. If soil suffers from different diseases a chemical cocktail is necessary which can lead to enormous risks for the health and environment.

Even by burning down arable land, heat reaches down to up to 10 cm depth. In early times this method was used for intensive farming, in particular on plantations to cure root diseases and control weeds. At the beginning of the last century soil roasters were used in which substrate was filled and heated over open fire.

Today hot air devices are used for dry soil heating.

With dry soils the roasting method can lead to heat damages and destroy the organic components of the soil, which are essential for the growth of the plant. Therefore one has to pay attention that the soil is sufficiently humid and treatment does not last too long when using dry heat.

Heat has been used to control pests and weeds since the very beginning of agriculture.

Until today fields are burned down in order to create and improve soil fertility. Ancient civilizations such as the Indians or the Egyptians also systematically used sun radiation on irrigated agricultural soil to disinfect and revive arable land.

At the end of the 19th century the application of heat for soil sterilization is documented whereas two methods were developed simultaneously: the roasting of agricultural soil over an open fire and the steaming of soil with water vapor.

At the beginning steam was induced into the soil through drainage pipes. Later steaming hoods and harrows were used. The development of heat resistant sheets made the treatment of large areas with steam easy to handle.

Chemical compounds for soil sterilization are easy to use and need little time for application.
Modern compounds have a relatively low effect range, only one or a few specific diseases or pests are overridden. Furthermore the application of chemical agents always comes with a long period of rest which is necessary to degrade or flush them out.

In particular if chemical means for soil sterilization are not applied properly harmful residues might stay in the soil and concentrate in plants which have still unknown effects on plants and man.
Besides the risk of resistance formation can not be ruled out when applying chemical agents which can even aggravate the symptoms of a disease.

Due to the uncertainty of bad side effects chemical agents for soil sterilization should only be applied very carefully, in particular when it comes to vegetable foods.