How the Steaming Process Works

How the Steaming Process Works

black groundcloth with green stripes covered in pebbly dirt and crispy brown leaves. an orange flag on  a piece of heavy wire is stuck through into the ground. gray wires can be seen disappearing into a spot of freshly disturbed earth.
sensors

Temperature sensors attached to dataloggers are buried in the soil at 5, 15, and 30 cm depths. There is one set of sensors for every 100 sqft of steamed area. Dataloggers are set to record the soil temperature once every 15 minutes. Soil moisture levels are monitored outside the steamed area.

black groundcloth has been stuck down. dead grass surrounds it. a flat black hose is laid on the cloth in a square spiral shape.
Steam hose

A steam sock is overlaid on the plot in a spiral pattern. This conveys the steam to the plot and behaves as a “soaker hose”, allowing even distribution of steam. After installation of sensors and hose placement, the plot is covered with a reinforced PVC tarp and the edges weighted with sandbags to prevent steam escape.

a red trailer holds a large white refillable water tank with a black hose attached to its top. the hose leads to under the corner of a groundcloth with its edges held down and its center blowing upward.
Tank provides water for the steam

The steam sock is connected to the output hose on the steam generator and steaming can begin. The length of time needed for steaming is determined by the size of the steam generator, soil moisture, and soil physical properties such as compaction and particle size.

a small white rectangular device with a digital readout in a ziploc bag
data logger

During the steaming process, the dataloggers are monitored. When all locations have reached the target temperature of 50°C for 30 minutes, the steaming is complete.

Back to: Steam treatment to sanitize soils, pots, and media

WSU Puyallup Research & Extension Center
2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated 9/24/2025