Archive for the ‘Soil Sterilization’ Category

Steam is also a hot thing for vine plants

Montag, April 30th, 2012

Last year the Service Center for Rural Areas (DLR) Rheinlandpfalz (Rhineland-Palatinate) has steamed vineyards for the very first time, in order to research the effects of this soil sterilization method on young vine.

Recently the results were presented. It was shown, that steam significantly increases the growth of plant shoots:

Steaming significantly increases the growth of vine shoots (Source: DLR Rhineland-Palatinate, Schifferstadt)
Steaming significantly increases the growth of vine shoots (Source: DLR Rhineland-Palatinate, Schifferstadt)

Steaming significantly increases the growth of vine shoots (Source: DLR Rhineland-Palatinate, Schifferstadt)

It remains to be clarified, if hot steam significantly improves the sprouting of vine. In particular where soil is both highly contaminated with diseases (such as fungus, bacteria, nematodes) and highly affected by soil fatigue, steaming could be developed to a profitable sanitation method for vine nurseries.

Under the leadership of Matthias Zink the DLR in Schifferstadt started a research study together with the steaming specialist MSD (Möschle-Seifert-Dämpftechnik – Steaming Technology) this year. Results are expected next year.

More research trials with steam at DLR & Agroscope

Freitag, März 9th, 2012

Also in 2012 renowned research institutes plan to do more research on hot steam..

The Service Center for Rural Areas (DLR) Rheinlandpfalz (Rhineland-Palatinate) will do more field studies in tree nurseries in the end of March 2012. In the process the focus will be on the optimization of steaming methods, in order to find out the most effective use of steam.

The preferred method is Sandwich-steaming. Hereby steam is injected simultaneously from the surface and in the depth through a steaming hood with pikes. The goal is the efficient use of hot steam at cost less than 5,000 EUR per hectare.

Besides the DLR, the Agroscope Institute of the University of Wädenswil in Switzerland will do another study on steaming. Hereby hot steam is used to kill a special kind of grass.

This grass has become a pest in Switzerland and causes increasing problems in agriculture as it hampers the growth of cultures. Hot steam shall help to sanitize these infested areas.

Fully Automated Steaming Robot Is Fully Developed

Sonntag, April 10th, 2011

The steaming robot, which has been developed last year, has left prototype status. End of March MSD Corp., the developer of the steaming robot which received the Indega and Taspo RAM innovation awards , announced that the system has been fully developed and that the German government safety association has approved the machine.

Approval by the government safety organization required further safety measures. Besides optimization of the driver’s console an automatic barrier recognition system has been installed (e.g. for kids) which leads to an emergency stop once activated.

Hence the steaming robot, which is manufactured by the Swiss German company Fobro-Kress, is the first approved robot for outdoor areas in Germany, which permanently can be operated without human control.

Steaming robot - BG-approved in 2011
Steaming robot – BG-approved in 2011

Hot steam finds its way into Kenya

Samstag, November 13th, 2010

Even where labor and land is cheap, hot steam is needed to sterilize arable land. In September 2010 a big Dutch flower grower started to use its steam generator in its Kenyan green houses.

Area steaming in Kenya – Flower growing
Area steaming in Kenya – Flower growing

Steam is mainly used to sterilize volcanic substrate so the material can be reused several times. The substrate gets steamed in steam boxes which are equipped with a vacuum steaming system. Vacuum steaming systems are highly energy efficient. The steam generator was manufactured by MSD Corp., Durbach.

Soil decontamination with hot steam

Dienstag, Dezember 22nd, 2009

Decontaminating and disinfecting soil with hot steam has been applied for more than 100 years and is well proven. The Swiss Friedrich Miescher Institute in Basel has made use of this method.

The institute will decontaminate the soil of several green houses completely without chemicals. The goal is to free soil from sproutable plant parts such as seeds and roots as well as restore the original condition of the soil before cultivation without residues of chemical products. Hence steaming was the first choice.

A contractor is responsible for steaming. First soil is loosened down to 20 cm depth, after that the area is gradually covered with steaming sheets which get weighted. Steam generated with a low pressure steam boiler, is induced via a steam injector underneath the sheets.

After 2-4 hours of steaming the desired results are achieved: The soil is completely sanitized and without weeds and diseases.

The danger of recontamination

Sonntag, August 23rd, 2009

A special source of danger of reinfecting soil with pathogens after steaming is deeper soil. Depending on the root depths of the planted culture, phytopathogenic organisms can reach and contaminate deeper layers of soil. It can happen that steamed higher layers of soil are reinfected by such deep lying pathogens.

Hence when soil is heavily contaminated it is recommended to take soil samples from different soil depths depending on the root depth of the planted crop and check on diseases in order to identify the necessary steaming depth.

Furthermore the injection of beneficial active micro organisms after steaming into the soil can significantly strengthen the resistance against intruding pathogens and immensely inhibit recontamination.

The danger of recontamination on the surface by carry over e.g. when using foreign substrates or planting contaminated plants can be limited through the injection of beneficial microorganisms.

Reactivation of decontaminated soil

Sonntag, August 16th, 2009

After decontamination of soil with hot steam a quick reactivation with microorganisms takes place. At the beginning, harmful as well as beneficial organisms resettle. But beneficial bacteria and fungi find better conditions and gain a considerable head start. In general beneficial organisms will prevail. The quick revival can be traced back to many different reasons: Most important is low competitive pressure from other species as well as the availability of nutrients and other beneficial chemical substances which were dissolved by steaming.

The first wave of reactivation comes from heat resistant species e.g. spore forming bacteria. The effect of heat shock on the termination of latency is well known in particular for bacteria and fungi. Furthermore microorganisms from deeper areas which were untreated move up.

Furthermore germinable spores arrive by air, most of them come from fungi. In most of the cases a new barrier against the spread of pathogens is formed quickly and naturally.

In rare cases, pathogenic organisms may prevail after steaming due to unbeneficial circumstances, which can lead to enormous damage. In order to prevent the spread of pathogenic organisms it’s recommended to seed beneficial microorganisms into the soil right after steaming.

Water vapor for soil steam sterilization

Samstag, August 15th, 2009

In contrast to other agents (such as air) water has the ability due to its high specific heat to absorb a tremendous amount of energy at a constant temperature of 100°C when transforming from water to steam. This energy is released in the soil for disinfection.

As a result this method obtains a particularly high degree of efficiency with which all organic pathogens are killed at sufficient time of exposure.

Due to the relatively low temperatures of just up to 100°C during the condensation process, soil is prevented from damage. In contrast to the usage of dry heat (e.g. hot air) soil can not be burned and its fertility harmed.
Compared to other chemical agents, water vapor has a comprehensive sterilization effect on soil. All organic pathogens are affected by the humid heat and even killed after sufficient exposure.

Chemical agents only partially take effect, since they are focused on single pathogens only. If soil suffers from different diseases a chemical cocktail is necessary which can lead to enormous risks for the health and environment.

Soil sterilization against soil born diseases in agri- and horticulture

Montag, August 10th, 2009

The intense cultivation of agricultural crops challenges nature, since it has a negative impact on the biological equilibrium and strongly promotes the spread and growth of organisms harmful to plants. The culture of resistant high-yielding varieties alone does not solve the issue.
Therefore plant protection and pest control is essential in order to ensure high yields and guarantee the food supply of a steadily growing world population.

Thus soil plays a central role. Under extensive use soil is disabled to control pests though its balanced biological activities. In particular in green houses, soil is exposed to many different diseases which leads to an increased occurrence of wither and root sicknesses, nematodes and weeds.
Soil sterilization is a highly effective treatment method in the area of plant protection.
Two different methods are in use at present: The chemical and the physical/thermal treatment of soil.

The chemical sterilization of soil

Montag, August 10th, 2009

Chemical compounds for soil sterilization are easy to use and need little time for application.
Modern compounds have a relatively low effect range, only one or a few specific diseases or pests are overridden. Furthermore the application of chemical agents always comes with a long period of rest which is necessary to degrade or flush them out.

In particular if chemical means for soil sterilization are not applied properly harmful residues might stay in the soil and concentrate in plants which have still unknown effects on plants and man.
Besides the risk of resistance formation can not be ruled out when applying chemical agents which can even aggravate the symptoms of a disease.

Due to the uncertainty of bad side effects chemical agents for soil sterilization should only be applied very carefully, in particular when it comes to vegetable foods.