Success Factor Soil Humidity

Simple rules of physics make it clear: the more water soil contains, especially the more humid it is, the more energy is required to heat it up due to increased specific thermal capacity.

Relatively, dry soil saves energy, time and thus money.

Furthermore, dry soil can better absorb humidity created by condensation of steam. Hence there is no danger of siltation caused by big amounts of free water which inhibits steaming later on. From start to finish of the steaming process, soil has to have free capillary tubes to allow transport of steam.

Water is kept in the soil due to capillary forces and organic components.
The ability of soil to absorb water subsequently depends strongly on its consistency. Basically sandy soil is dryer than humus rich compost soil or turf.

In the following we have listed different types of soil and their regular degree of humidity in % in relation to their wet weight:

A) Medium humous sandy soil in green houses: 12 – 20% water content
B) Well humous sandy soil in green houses: 20 – 30% water content
C) Medium humous clayey soil in green houses: 15 – 25% water content
D) Well humous clayey soil in green houses: 25 – 35% water content
E) Very humous soil in green houses: 30 – 50% water content
F) Compost soil: 20 – 40% water content
G) Turf: 50 – 60% water content

It is recommended to only steam relatively dry soil. In practice, desired soil conditions can quickly be met after the removal of the previous culture as long as soil can dry for a couple of days.  However before removal, the area to be steamed should only be sparsely watered.