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How to sterilize soil with steam

steam soil

Written by Maarten Casteleijn | 12-05-2021

Soil steaming is done in the greenhouses during crop rotation. In this way bacteria, viruses and other pathogens are killed and the soil is ready for the new cultivation. This is also called soil steam sterilization. To steam the soil, you need different materials to ensure that the steam can enter the soil. In this article our specialist explains soil steam sterilization.

Conditions for soil steam sterilization

In principle, the soil can be steamed in any greenhouse, but there are a few conditions:
  • The soil must not be too wet: the drier it is, the better. Take this into account during the last watering session. 
  • The soil must be well and deeply dug beforehand, so that the steam can penetrate it properly. 
  • The soil pH must be at least 6.5. 

With or without under pressure

There are two methods of greenhouse soil sterilization: with under pressure or without under pressure. The principle of steam is the same with both methods: with a steam boiler, steam is blown through a steam hose under the steam plate so that the steam can enter the soil. The difference between the methods is whether they should be used under pressure or not. When you are using steam under pressure (also called suction steam), you connect a fan to the drain hoses in the soil, which creates under pressure. The advantages are that the steam can penetrate deeper into the soil and that higher temperatures can be reached at this depth. The higher the temperature, the more pathogens will be killed.

Soil steam sterilization equipment

So, steaming soil can be done in two ways. For each way, you need different types of materials. At Royal Brinkman, we have a range with all the steam supplies you need for steaming soil.

Steam equipment

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Working method

Each grower has his own way of soil steam sterilization, using skills he has discovered over the years. However, the most commonly used method is as follows:
  • Roll out of the chains or water hoses.
  • Lay down the steam sheet and place the chains or water hoses on the edges of the steam sheet. Pull the sheet a bit over the concrete path, so that the soil right next to the concrete path is also steamed well. 
  • Check that there are no holes in the steam sheet and if there are holes, repair them. Do not walk on the sheet any further, as this will increase the risk of cracks. 
  • You can choose to cover the steam sheet with isolating foil. This prevents heat loss. 
  • Place the steam hose under the steam sheet and attach it to the steam boiler. It is important to use a steam boiler with sufficient capacity:
  •  o Dry-cleaning without under pressure 600,000 kcal/100m² ~78m³ gas/hour
     o Dry-cleaning process with under pressure 1,000,000 kcal/100 m² ~130m³ gas/hour
  • Connect the steam boiler to a water supply. Use the cleanest water possible, preferably rainwater. Also make sure that the water is evenly pumped into the steam boiler. Never use an irrigation pump for this purpose!Turn on the steam boiler and open the tap completely. Steam from 100 - 130 °C is then pumped under the sheet. 
  • Close the steam tap as soon as the steam sheet is full to prevent the sheet from slipping off. 
  • After about 6 hours the soil is completely steamed. 
  • When steaming with under pressure, leave the fan on for at least 12 hours. This may cause the temperature to rise slightly.

Outsource soil steam sterilization

Soil steaming is heavy and intensive work and also special soil steam mechanical equipment is needad. More and more growers are opting to outsource this work. You can hire different companies for this purpose. They take care of the entire process and (if desired) take care of the steam sheet and other supplies themselves. 


After steaming the soil, good aftercare is of great importance. Leave the soil to rest for a few days - or preferably a week - so that the structure does not deteriorate. When you start working on the soil, make sure that your shoes, clothing and used machines or other tools are disinfected. This will prevent the soil from being contaminated. After planting, it is also important that the soil is not immediately overloaded with water. The soil structure is not yet able to cope with this: it must get used to absorb water again after steaming. Start with small water sessions and build it up slowly. 

Plant resistance after steaming

When making use of plant resistance products, the recovery time for the soil can be shorter. It is important for the soil life, that the soil is cooled after it has been steamed. A possibility to cool the soil quicker, is by drawing in cold air through the pipes. 

“It is of importance to ‘feed’ the soil after steaming it in order to ‘fill’ the soil”, according to our plant resistance specialist. Thanks to ‘filling the soil’, pathogens are given less space to infect and damage the plant. Worms, molds and bacteria, such as mycorrhiza and rhizobacteria can fill the soil. These organisms live in nature and in the root environment of the plant. 

The names rhizobacteria and mycorrhiza indicate that they belong to the root environment of the plant. This because rhizo is the Greek word for ‘root’.

In order to improve the soil structure, you can choose to add several worms. Worms ensure a soil in which all micro-organisms can live. You can create a good environment for positive interactions by keeping out undesired molds and bacteria. 

Questions about soil steaming
Do you have questions about soil steam sterilization, or would you like advice? Then contact product specialist Maarten Casteleijn, or ask your question using the form below.

Maarten Casteleijn About Maarten Casteleijn

Maarten Casteleijn is a product specialist in plant resistance at Royal Brinkman. In addition to experience in horticulture, he also has experience in teaching and coordinating research in the medical sector. By combining his work experiences, he can look at a problem with different perspectives and think out of the box. Maarten says that his passion is reflected in his work experience: receiving and sharing knowledge. "I have a broad interest in innovation and sustainability. Together with the grower, I want to achieve a final zero discharge by increasing plant resilience". 

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