What happens when we steam the soil?

A lot of different organisms live in the soil – everything from single-celled animals and microorganisms, such as bacteria, fungi and viruses, to nematodes, arachnids, earthworms and insects. A multitude of organisms in the soil live in symbiosis, meaning they are interdependent.

Courtesy of www.landscapeforlife.org

In untouched soil, there is a whole community of organisms that depend on each other. Plants stand at the beginning of the soil food web. Through photosynthesis they are able to capture the energy of sunlight and manufacture organic molecules that supply the energy for all other organisms. This dynamic system works best if living plants occupy the field year-long, as in nature.  

When we cultivate the soil, especially in monoculture and large-scale production, we can destroy this balance. The result may be a flourishing of often unwanted organisms. Historically, industrial agriculture has paid little attention to soil life, while organic farming has been more concerned with this balance and operated in a way that promotes soil life. Nowadays, more attention is paid to soil life across all types of agriculture.

Monoculture without crop rotation often promotes the development of certain organisms, and if these organisms are harmful, a problem will soon arise. Whether this problem comes in the form of fungal diseases, pests or weeds, when it becomes significant enough, people often resort to pesticides to overcome it. In recent years, there has been a firmer focus on the harmful effects of pesticides on nature and humans than previously, and more and more of these pesticides are now being banned.

This puts farmers in a difficult position. Often, they must resort to pesticides with a worse effect, which may lead to more spraying. In some cases, no pesticides can be used at all. In some areas of the world, the topsoil has now become so depleted and full of harmful organisms that it cannot be cultivated: even when pesticides are used, the pests gain the upper hand.

So, if some soils are impossible to cultivate without pesticides while others are impossible to cultivate even with them, what can be done?

One alternative is to let the lie land fallow for many years and then possibly switch to organic farming.

“In Soil Steam, we have taken the well-known concepts from steaming and combined it with new insight from process control and automation, precision farming, and integrated pest management. The result is a steaming technique that reduces energy consumption, speeds up the steaming process, and reduces negative impact on the soil”.

Another option is to steam. Steaming has long been used as an alternative to pesticides. In Soil Steam, we have taken the well-known concepts from steaming and combined it with new insight from process control and automation, precision farming, and integrated pest management. The result is a steaming technique that reduce energy consumption, speeds up the steaming process, and reduce negative impact on the soil.

When we steam the soil, we send hot steam down into the soil layer. We can control how deep we steam and the temperature the soil reaches.

When the soil reaches the correct temperature, soil-dwelling organisms die. The temperature required for this varies from species to species. Most living organisms die at a temperature of around 70°C over a period. When hot steam also fills the water-saturated air that surrounds the organism, it will be even more lethal.

Lethal temperatures vary from species to species. Some weed seeds can tolerate high temperatures without losing the ability to germinate; killing large tubers also requires longer exposure or higher temperatures. The resting stages of some nematodes, such as cyst-forming nematodes, also tolerate heat well.

The fact that we can kill unwanted organisms is good news, but there are also a lot of organisms that we want to keep in the soil – and the bad news is that some of these will also die during steaming.

We are working to determine the lethal temperatures for both unwanted and desired organisms in the soil. How can we neutralize as many of the unwanted ones as possible but avoid removing those we want to keep?

Encouragingly, it seems that a large part of micro-life returns relatively quickly after steaming. What we do not know, however, is which species re-establish themselves and to what extent. Will the balance be the same as before steaming?

We are also experimenting with different soil additives that can be used after steaming to see whether we can inoculate desired microorganisms.

Soil life is something that we at Soil Steam take very seriously, and it is one of the main priorities on our agenda.

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