Steaming (floor disinfection)
Steaming is an alternative sterilization method for soils and substrates in agriculture and horticulture . By introducing hot steam , settled organisms , including pests such as weeds , fungi , bacteria and viruses, are killed through physical degeneration of the cell structures . The process is a partial disinfection from a biological point of view. Important heat-resistant, spore-forming bacteria revitalize the soil after it has cooled down. Soil fatigue is countered by releasing blocked nutrients . Steaming has been shown to lead to a better starting position and faster growth of the plants, whereby their resistance to diseases and pests is strengthened. The use of superheated steam is today unanimously recognized by both practitioners and researchers as the best and most effective means of sanitizing diseased soils, growing soils and composts .
Goals of soil disinfection
The aim is to quickly and safely rid the soil of substances and organisms that are harmful to plants
- Metabolic products
- bacteria
- Viruses
- Mushrooms
- Nematodes and
- other animal pests
Other positive effects should be emphasized:
- All weeds and weed seeds are completely killed
- Significant increase in plant growth
- The elimination of so-called soil fatigue by activating chemical-biological reactions
- Blocked nutrients in the soil are tapped and made available to the plants.
- Replacement of chemical insecticides , herbicides and fungicides such as methyl bromide or basamide
Steam with superheated steam
The modern steaming methods with superheated steam from 180 to 200 ° C achieve optimal floor sanitation. The soil absorbs only a small amount of moisture. The activity of the microorganisms can unfold immediately when the soil cools down. This creates the most favorable conditions for immediate soil cultivation for growing young plants and for growing seeds.
With the process of integrated damping, targeted repopulation of the dampened soil with beneficial organisms can also be promoted. The soil is first freed of all organisms by steaming and then, in a subsequent step , it is revitalized and microbiologically buffered by introducing a compost-based soil activator, which contains a natural mixture of desired microorganisms ( e.g. Bacillus subtilis, etc.).
Different types of use of steam are represented in practice, which includes both substrate damping and surface damping.
Area damping
Several methods are used for surface steaming, including film damping, the steaming hood, the steam harrow, the steam plow and vacuum steaming with drainage pipes or mobile pipe systems.
It is advisable to use the most suitable method for area damping, whereby the required area performance plays the most important role in addition to the nature of the soil and the plant culture. Further combination methods, such as sandwich damping or partially integrated sandwich damping, are currently being developed to increase efficiency in order to be able to save as much energy and effort as possible when steaming.
Foil damping
Surface damping with special foils (foil damping) is a method that has been tried and tested for decades to dampen larger areas of 15 to 400 m² in one operation. If the foil damping is used correctly, this is simple and economical. Heat-resistant and rot-proof insulating fleece saves up to 50% energy, considerably reduces the steaming time and improves the depth effect. Steaming areas of up to 400 m² per work step, in 4–5 hours to a depth of 25–30 cm / 90 ° C, are feasible.
When using heat-resistant and rot-proof synthetic insulation fleece, 5 mm thick / 500 gr / m², the steaming time can be reduced by about 30%. After the film has been laid out and weighed down, the steam is fed under the steam film using a steam injector or a perforated pipe, for example with sandbags.
The area performance in one work step depends on the power of the steam generator (example: steam boiler ):
| Steam output kg / h: | 100 | 250 | 300 | 400 | 550 | 800 | 1000 | 1350 | 2000 |
|---|---|---|---|---|---|---|---|---|---|
| Area m²: | 15-20 | 30-50 | 50-65 | 60-90 | 80-120 | 130-180 | 180-220 | 220-270 | 300-400 |
The steaming time depends on the nature of the floor and the outside temperature and is about 1–1.5 hours per 10 cm steaming depth, with a floor temperature of about 85 ° C being reached. Milling alone to loosen the soil is not recommended, as this will make the soil structure too fine and thus reduce the vapor permeability. Loosening with spading machines is ideal, whereby an optimal damping result can be achieved when the earth has been worked deep. After cultivation, the soil should be coarse in the depth and finely crumbled in the upper layer.
In practice, it has proven useful to steam with at least two foil webs, one foil web being under steam and at the same time the second being prepared for the introduction of steam. This avoids steaming pauses.
Deep damping with negative pressure
Steaming with negative pressure, which is introduced into the area to be treated via mobile or fixed pipe systems, is the steaming method with which the greatest depth effect can be achieved. The permanent installation of drainage systems makes sense for intensively used areas despite high investment costs, whereby a damping depth of up to 80 cm can be achieved.
In contrast to the permanently installed drainage system, the suction pipes in the mobile suction system are laid on the surface. A central suction line, consisting of galvanized quick-release coupling pipes, is coupled in a uniform grid dimension of 1.50 m and the hose ends are inserted into the desired damping depth with a special insert rod.
As with foil steaming, the area to be damped is covered with a special steaming foil, sealed all around and the steam is guided under the foil with an injector and protective tunnel. For short areas up to 30 m in length, the steam is poured in at the front, for longer areas in the middle of the bed, with a T-distributor on both sides.
As soon as the damping film has been inflated by the steam pressure and the voltage has reached a height of about 1 m, the suction turbine is switched on. The air in the floor is first sucked out through the suction hoses inserted into the floor. A vacuum is created and the steam cushion under the foil is guided downwards.
In the end phase, when the desired steam depth is reached, the fan runs continuously and blows out increasingly hotter steam. So that the extracted steam is not lost, it is led back under the film.
As with all other steaming systems, subsequent steaming is roughly 20 to 30 minutes. required. The steaming times are approx. 1 hour with a corresponding steaming depth. The steam requirement is approx. 7–8 kg / m² steaming surface.
The most important prerequisite is the optimization of the soil structure by loosening the soil. Basically, the depth effect depends on the loosening.
Steaming with steaming hoods
A steam hood is a mobile device made of corrosion-resistant materials such as aluminum that is placed on the surface to be steamed. In contrast to the film damping, the labor-intensive work steps of film laying and weighting are omitted, but the area performance per work step is correspondingly lower depending on the hood size.
In the outdoor area, a hood is moved by hand or, depending on the size, with a tractor on a special pre-tensioned 4-point suspension. The steaming time is 30 minutes for a depth effect of 25 cm depth, whereby a temperature of 90 ° C can be reached. In large glass houses with a stable construction, hoods can be hung on roller rails and lifted and moved with pneumatic lifting cylinders. Small and medium-sized hoods up to 12 m² are moved manually with a rocker arm system or moved electrically with special cable winches.
Combined surface and depth entry of steam (sandwich damping)
An efficient method of bringing superheated steam into the ground is sandwich damping, which is a combination of depth and surface damping. The steam is simultaneously introduced into the earth via the surface and deep down. For this purpose, the crop area to be steamed, which is already equipped with a deep steaming system, is covered with a steaming hood and the steam is introduced from above and below at the same time. The foil cover is unsuitable because this process creates an increased pressure under the cover of up to 30 mm water column .
Sandwich cushioning offers several advantages. On the one hand, the energy input can be increased to up to 120 kg of steam per m² / h, with the result that up to 30% energy and thus fuel (such as heating oil ) can be saved compared to other steam input methods such as foil steaming. The increased energy input also accelerates the heating of the floor, which means that the heat loss can be reduced in line with the energy savings. On the other hand, only about half the steaming time is required for sandwich steaming.
Comparison of sandwich steaming with other steam injection methods in terms of steam output and energy requirement (*):
| Steaming method | Max. Steam output | Energy requirement (*) |
|---|---|---|
| Foil damping | 6 kg / m 2 h | approx. 100 kg steam / m 3 |
| Depth attenuation (foil + vacuum) | 14 kg / m 2 h | approx. 120 kg steam / m 3 |
| Hood damping (aluminum) | 30 kg / m 2 h | approx. 80 kg steam / m 3 |
| Hood damping (steel) | 50 kg / m 2 h | approx. 75 kg steam / m 3 |
| Sandwich cushioning | 120 kg / m 2 h | approx. 60 kg steam / m 3 |
(*) in soil with a maximum water content of 30%
It can be clearly seen that sandwich steaming has the highest steam output with the lowest energy requirement.
Partial integrated sandwich cushioning
The partially integrated sandwich damping is a further developed combination process in which only the areas to be planted are treated with steam while deliberately saving all non-usable arable areas (such as spaces between the rows of plants). In order to avoid the risk of re-infection of the steamed surfaces with harmful organisms from the non-steamed areas, beneficial organisms are introduced into the sanitized soil using a soil activator (e.g. special compost). The partially integrated sandwich damping opens up further potential savings in steaming.
Container / pile damping
Pile damping is used for the thermal treatment of compost and substrate soils such as peat. Depending on the amount to be steamed, the material to be steamed is stacked and covered either in steaming boxes or in smaller tipping trailers up to 70 cm. The steam is introduced evenly via distribution pipes. Steam containers and earth boxes, which are equipped with a suction system to improve the steaming performance, are used for large quantities. Small quantities can be steamed using special small steamers.
The amount of soil should be coordinated so that the steaming time is a maximum of 1.5 hours in order to avoid large amounts of condensate in the lower layers of soil.
| Steam output kg / h: | 100 | 250 | 300 | 400 | 550 | 800 | 1000 | 1350 | 2000 |
|---|---|---|---|---|---|---|---|---|---|
| m 3 / h approx .: | 1.0-1.5 | 2.5-3.0 | 3.0-3.5 | 4.0-5.0 | 5.5-7.0 | 8.0-10.0 | 10.0-13.0 | 14.0-18.0 | 20.0-25.0 |
In the case of light substrate soils, such as peat, the hourly output is much greater.
Use of superheated steam
- in horticulture and tree nurseries for the sterilization of cultivated soils and substrates.
- in agriculture for the sterilization and processing of food waste for pig fattening and heating of molasses etc.
- in mushroom cultivation for pasteurization of the culture areas, sterilization of the culture soil, combined use as heating.
- in wineries as a combination boiler for sterilizing and cleaning storage tanks, temperature control of mash , for hot water production.
- in cities and municipalities for partial as well as extensive control of invasive neophytes
history
Ancient cultures, such as the Indians and Egyptians, used a similar method in which the arable land was sanitized and revitalized through the targeted use of solar radiation on watered cultivated soils.
In the Indian wisdom (Veda, 4000 years old) the heating process is called "rab" (HL Francis).
The ancient Egyptians practiced this culture method in the Nile Delta and called it "sheraqui". The uppermost soil layers were flooded with water from the Nile. The solar radiation then warmed the wet soil layers to temperatures of 70 ° C and sometimes even more (JA Prescott).
Virgil described the fertility-increasing heating process among the ancient Romans (source: Dissertation by the Hungarian Dr. Georg Boros, Eidgenössische Technische Hochschule Zürich, 1954).
literature
- Hans-Joachim Labowsky: Robot steams completely on its own - Vegetables magazine: 6/2014, pp. 50–51
- Dr. Norbert Laun: Steam up the weeds - Vegetable magazine: February 2011, pp. 18–22
- Hans-Christian Gudehus, Osnabrück University of Applied Sciences : Steaming in Horticulture , Osnabrück Contributions to Horticulture 6/2005.
- Reinhard Böhm: Investigations of practical thermal processes for soil disinfection using the example of selected microorganisms . FKZ: 020E150, University of Hohenheim, see forschung-oekolandbau.info - BÖL report ID 14886, 2004
- Hanns-Henning Horn: Recommendations for the efficient use of steam for floor damping in steel-glass and steel-plastic greenhouses . Humboldt University of Berlin, Horticulture Section. IGA short documentation 5/81
- Michael Böhme, Reinhard Schmidt: Possibilities of using stationary underfloor pipe systems in greenhouses for floor damping and heating . Humboldt University of Berlin, Horticulture Section. Arch. Gartenbau, Berlin 29 (1981) H. 7, pp. 357-373
- Friedrich Konrich: Basics, technology and areas of application of disinfection and sterilization using heat . Ferdinand Enke Verlag, Stuttgart 1963
- Hermann Hege, Helga Roß: The steaming of soils and earths . KTBL paper 153, Darmstadt 1972
- R. Koblet, H. Deuel: Studies on the effect of heating on the germination capacity of weed seeds and on physical and chemical properties of the soil . Georg Boros, Zurich 1954
- Klaus Pröttel: Use of a hood damper using a new steam boiler with a high degree of efficiency and low flue gas emissions . Steinbeis Transfer Center, Federal Ministry of Food, Agriculture and Forests - 89 UM 08, Offenburg March 1994
- Anne Hahnenstein: Well-engineered steaming technology for soil disinfection - Vegetables 7/1994 (specialist conference in Friesenheim)
- Hans-Joachim Labowsky: Steaming techniques in horticulture - Taspo-Magazin: 3 / March 1990
- Hans-Joachim Labowsky: Use of steaming hoods - GbGw 28/1991 (Gärtnerbörse / Gartenwelt)
- Hans-Joachim Labowsky: Steaming for soil disinfection . German horticulture 24/1994 (symposium in Friesenheim)
- Friedrich Merz, State Institute for Plant Protection Stuttgart - German Horticulture 10/1990
- Norbert Belker, Chamber of Agriculture Westphalia-Lippe - German Horticulture 10/1990
Individual evidence
- ↑ Research report Service Center Rhineland Palatinate, September 2010: Weed control in seed crops, especially rocket (PDF; 1.8 MB), Author: Dr. Norbert Laun, Queckbrunnerhof Research Institute, Schifferstadt. Retrieved February 14, 2011.
- ↑ Research report Service Center Rhineland Palatinate, January 2011: Elimination of soil fatigue, especially on tree nursery areas ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , Author: Gerhard Baab, Rheinbach. Retrieved January 18, 2012.
- ↑ Website of the Federal Ministry of Food, Agriculture and Consumer Protection: Winner of the German Horticultural Innovation Prize 2011 ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. . Retrieved September 3, 2011.
