Sheet steaming

This method is the most traditional and therefore the most common surface steaming technique.

If used properly, sheet steaming is easy and still profitable despite its high energy
requirements, especially in small and specialised horticultural farms.In one working cycle, you can easily treat up to 400 sq.m surface with 85°C steam at 25-30cm depth in 4-5 hours.

The advantages of this steaming system are its relatively low primary cost and easy
application. Moreover, you can work step by step very efficiently. The steam should, however, be applied for up to four hours or even longer, if needed. This means energy loss is unavoidable and this method is thus the most energy-intensive.

Depending on the steaming time and soil characteristics, you need 0.5 litres of heating oil per square metre to reach 7-10 cm steaming depth (or 2 litres of oil to reach 25-30cm depth). You will achieve up to 85°C soil temperature with this method.

The following rules of thumb apply:

1. The longer the steaming time, the higher the energy losses (hence the high energy demand per square metre).
2. The steaming time for 10cm steaming depth is about 1 -1.5 hours.

Using a heat-resistant and non-rotting insulation mat can save up to 35% in energy. The steaming time can be significantly reduced and the depth of effect can be improved.

The steaming sheet is made of special heat-resistant plastic.

It is necessary to sufficiently weight down the sheet edges. Ideally, weights should be sandbags of dia. 10cm, or twin-bags of dia. 10cm each, at least 10kg/running metre. For large surfaces, this is indispensable. If you use insulating mats above the sheets, weight them down together with the sheets.

Please observe the following basic principle: in all surface steaming methods, the soil must be loosened first.

Rotary tillage alone is not the best solution, especially in sandy soils, because the soil structure is too fine and too tight for the steam. The ideal method for loosening the soil is with a spade machine - the deeper the better!

When you loosen the soil, adhere to this basic rule: there should be coarse clods at depth and fine clods at the surface, i.e. tillage should be to max. 10 cm depth.

Under the sheet, the steam is introduced into the soil gently by means of a special steam injector. The latter is covered and elongated with a protective tunnel made of wood (2m long x 30cm wide).With our special MSD steam injectors, you can generate the optimum mixture of steam and air. The sheet is inflated straight away and is protected with an air cushion at a lower temperature. At its injection point, the steam sheet is protected against burns with jute bags.

In sheets wider than 4m, it is absolutely necessary to put an additional row of sandbags in the middle. Otherwise, the sheet tunnel will be too high and the sheet will slip away from the lateral side of the line of weights.

The lower the sheet tunnel, the better the depth effect. Soil moisture content is also very important. Dry soil has poor thermal conductivity. Plant humidity is the ideal soil humidity.

Like in all methods of soil and substrate steaming, it is important that the steamed product is not wet. Wetness causes enormous energy consumption and closes the pores, so the steam cannot penetrate everywhere it is needed.

With sheets longer than 50m, the steam should be injected not from the far side, but from the middle of the sheet. It is better, however, to apply the steam across the entire width and to make up for it by halving the length.

Sheet steaming is also suitable for special plant beds and tables. If you have a sufficient quantity of steam with 6-7kg/sq.m density, 2-3 hours of steaming time will be enough (depending on the soil structure, temperature and moisture content in the substrate). The faster the air can escape, the shorter the steaming time will be.

After steaming, leave the sheet for about 30 min. to let the heat act for as long as possible. The longer the heat remains in the soil, the better the result of the sanitisation.

The sheet heating system can be equipped with an extraction system (see below), so you can reduce the steaming time or increase the steaming depth to 50-80cm.

The surface performance per working cycle depends on the size of the steam boiler.

Depending on the soil properties and the ambient temperature, the steaming time is 1-1.5 hours to reach 10cm steaming depth and about 80°C soil temperature.

You can reduce the steaming time by covering the steaming sheet with a special insulation mat.