How does it grow in steamed soil?

Soil steaming is an environmentally friendly method for sterilizing soil, eliminating harmful organisms such as weeds, fungi, and harmful microorganisms. But how does steaming affect plant growth, and what happens to the soil after it has been steamed? The answer is encouraging for those looking to grow plants without the competition of weeds.

Photos 1 and 2: 4000 tons of soil were steamed by Dokka Entreprenør at Jevnaker in Norway during the summer and fall of 2024. In these areas, grass and trees are growing well with no signs of weeds. Photo: Benedikte Watne Oliver, Norwegian Public Roads Administration.

No Weeds in Steamed Soil

Extensive testing of various soil types, including construction soil mixed with sand and peat, has shown that no weeds survive in steamed soil. In a recent experiment conducted by SoilSteam International, the soil was steamed to 70°C and 90°C, and ryegrass was then planted in it. The results clearly showed that weeds did not sprout in the steamed soil, while in the control group (non-steamed soil), significant amounts of weeds began to grow after just two weeks. This highlights that soil steaming effectively eliminates weeds and provides a clean foundation for plants to thrive.

*Photo 3: Full of weeds in untreated soil (left) after just a few weeks. Steamed soil (right) remained weed-free all season.*

Better Growing Conditions in Steamed Soil

But it’s not just the absence of weeds that makes steamed soil advantageous. The tests also revealed that plants grown in steamed soil exhibited much better growth compared to those in non-steamed soil. Specifically, ryegrass planted in steamed soil grew significantly better—in terms of height, density, and color. After about a month and a half, the ryegrass in steamed soil had reached 24 cm in height, while in the non-steamed soil, it only grew to 16 cm.

*Photo 4: Ryegrass planted in steamed soil (on the right) grows much faster and has a “healthier” green color compared to the grass growing in the untreated control (on the left).*

Improved Root Development

Another important finding was that the plants’ roots developed much better in steamed soil. When the ryegrass pots were emptied, the root systems were found to be more extensive and better developed in the steamed soil. This indicates that plants have better access to nutrients and water in steamed soil, which promotes healthier growth.

*Photos 5 and 6: The pictures clearly show better growth in the grass that has grown in steamed soil (on the right in both photos) compared to the untreated construction soil.*

Conclusion

Soil steaming is a highly effective method for eliminating weeds while also providing plants with better growing conditions. In the experiment, ryegrass grew faster and denser in steamed soil, and no weeds survived the steaming process. This makes soil steaming an ideal solution for anyone looking to grow fruits, vegetables, or flowers without worrying about competing weeds.