How to steam soil

How to steam soilIn greenhouses where the crop is grown in the open, the soil is steamed during crop rotation. In this way bacteria, viruses and other pathogens are killed and the soil is ready for the new cultivation. To steam the soil, you need different materials to ensure that the steam can enter the soil. In this article our specialist explains how to steam soil.

Conditions for soil steaming

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 steaming soil: 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.

Working method

Each grower has his own way of steaming soil, 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 steaming

Soil steaming is heavy and intensive work. 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. 

Aftercare

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. 


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



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