Fire can burn soil, and above 400 C it can even alter the texture of soil. Burning soil can be both beneficial and detrimental when it comes to gardening.
Burning soil can be done by spreading dried leaves or wood chips over the required area and setting it afire. However, the area should be sectioned off to prevent fire from spreading. Burning soil will effectively get rid of weeds and unwanted pests embedded in the soil.
Get ready! Because we are going to discuss everything you need to look out for when burning soil so you and your garden can flourish.
What Happens When you Burn Soil?
As it has been a topic of discussion for many years that it is possible to burn dirt and we have come to know about the following points:
- Burning dirt is almost impossible.
Burning, by definition, is raising the temperature in the presence of oxygen until the substance begins to combine with oxygen in an exothermic reaction.
Dirt is a mixture of finely granulated rocks, organic material, minerals, and naturally occurring elements.
Some of the organic material may combust, but as the entire process is endothermic, dirt is well known for its ability for stopping a fire.
2. Dirt is also non-combustible because mostly it is full of water and other minerals which we can’t burn.
3. The things which are responsible for soil not being able to burn are as follows
Minerals such as Silica, Iron Oxide, etc. (most of which are already oxides and do not burn and can burn on high temperatures)
Although from the above discussion, we know that it is impossible to burn dirt, if this dirt is dry, then there is much possibility that it can burn.
Effects of Fire on Soil Nutrients:
The intense burns many have very destructive effects on the physical properties of soil.
This may be due to the consumption of soil’s organic matter as the macronutrients of soil are essential for the growth of a plant.
Following are some nutrients in soil:
The fire usually decreases and destroys the pool of nutrients by oxidation, ash transport, leaching, volatilization, and erosion.
According to some research, soil fertility increases due to low-intensity fires because fire converts nutrients bound in dead plant tissues and the soil surface to more available forms.
As we understand, soils are directly linked to various vital elements of the ecosystem such as water, floral, and faunal because each one of them are interdependent.
The changes in biological properties are the result of the following changes:
Ø Changes or loss of microbial species and population dynamics.
Ø Reduction or loss of invertebrates.
Ø Partial elimination of plants roots.
Moreover, all the changes occur due to the changes caused by fire in water, floral and faunal components of the ecosystem because they are interdependent.
The effect of fire on soil is also due to the amount of heat released from combusting biomass and the duration in which it is combusting.
Intense burns may have detrimental effects on soil physical properties by consuming soil organic matter.
Intense fires (> 400 C) may also permanently alter soil texture by aggregating clay particles into stable sand-sized particles, making the soil texture coarser and more erodible.
Physical impacts of fire on soil include a breakdown in soil structure, reduced moisture retention and capacity, and development of water repellence, all of which increase susceptibility to erosion.
When fire consumes vegetation and underlying litter layers, hydrophobic or water-repellent soil conditions can form.
How to Burn Soil?
The simple answer is not easy, but yes, soil can burn if the temperature exceeds 280°C, exothermic reactions (those reactions that produce heat).
When soil surface temperature reaches 500 to 600°C, glowing combustion occurs if oxygen is not excluded from the char surface.
The presence of organic matter and the burning of soil
Soils vary from near zero organic matter content to as much as half organic matter or more, so some soil with near-zero organic matter will not burn at all but may smolder a bit if heated to four or five degrees or hotter Fahrenheit
Soils with a lot of organic matter, such as the top layer in some forests, swampy ground, or grasslands, will burn if heated to about the same temperature if the soil is dry.
Ignition may occur at lesser temperatures, but most likely not.
To burn garden soil:
- Spread dried leaves, wood chips or even mulch over the area to be burnt.
- Avoid using gasoline or any other additives that can seep into the soil and cause harm to plants that will be sown afterwards.
- Important NOTE: Cut a clear “trace” around the area so that the fire would not unintentionally spred into other areas.
- Light the fire from more than one point and then watch it do its thing.
Overall, It takes quite a while for damp soil to get hot, so a fire usually just burns very little of the organic material right on top in the case of a fire, unless of course, the soil is very dry.
In that case, the soil generally smolders, which means it is burning but only very slowly, because not much air can get to the organic material in the soil. Therefore, it can’t burn quickly.
See our article on mulched sand catching fire.
Can Burning Soil Prevent Weeds?
Did you know some thieves reside in the soil? Which steal nutrients, sunlight, and water from our food crops. They are non-other than weeds. So how can one get rid of these thieves?
Although there are multiple ways to get rid of weeds, one of the ways related to our topic is the burning of soil.
Burning soil can kill weeds and can also kill the seeds that are retained on the surface of the soil.
Once they are buried below the surface of the soil, then killing them becomes very difficult.
The reason is that soil act as an incubator to protect seeds. Therefore, knowing the temperature, length of time of exposure, and other variables is necessary for each weed species.
Overall, flame weeding may be one of the best options for removing weeds from garden soil.
As an organic process, its benefits are twofold: as it kills weeds and allows crops or other plants to grow, it replenishes the soil of nutrients without any human effort.
Burning Soil to Get Rid of Pests
Burning soil will help prevent pests and get rid of their eggs from the soil by exposing them to high temperatures.
This can be done by either burning dead leaves as explained above or by the use of an acetylene torch.
Using an acetylene torch gives more control over burning but can be tedious.
Note: Although burning soil is effective in removing weeds and unwanted pests, it can also have devastating effects on beneficial microorganisms such as earthworms and nematodes in the soil.
After burning, the soil should be left for some time to rebuild a healthy microbial population. Beneficial nematodes and earthworms can also be added to help speed up the process.
When is the Best Time to Burn soil?
We have already discussed the impacts, tips, and benefits of burning soil, so now it’s time to know which is appropriate to burn land or soil.
As it depends on the purpose, habitat, and geography of the land, there are probably few seasons considered ideal for burning land.
Garden soil should be burned, or flames applied during late evenings on dry days. This ensures that the moisture levels are low enough for the heat of the flame to have the maximum effects on the weeds and pests its being applied for,
Finally, it is believed that the best time to burn is in the late winter or early spring. During this time, new plant growth hasn’t sprouted yet, and existing plant growth is dormant or dead.
In this article, we address the most interesting questions regarding the burning of soil and we come to know that one can burn soil at a very high temperature keeping in mind that there are various harmful effects on the whole ecosystem because it leads to loss of very vital nutrients that are necessary for the growth of plants such as Nitrogen, Potassium, Phosphorus, etc.
There are various benefits of burning soil as low burning increases soil fertility and burns weeds, which steals vital soil components.
While thinking of burning the soil, one should also investigate the details of the temperature and the season of burning soil.
In addition to this, one cannot burn dirt and it is due to the presence of some elements like Silica and Iron Oxides, living organisms, and dead plants that do not burn but on the other hand, dirt can burn at extreme temperatures.