Fire up your soil’s fertility and health with biochar
11/03/2020 / By Leslie Locklear / Comments
Fire up your soil’s fertility and health with biochar

If you feel like your soil is in dire need of nutrient replenishment, you might want to give biochar a try.

Biochar is a carbon-rich form of charcoal formed by burning organic material from agricultural and forestry wastes – also known as biomass – in an environment with very little oxygen.

This process, called pyrolysis, helps stabilize the carbon present in the organic matter stable, thereby ensuring that it can’t easily escape into the atmosphere.

Where did biochar originate?

Biochar, despite its seemingly futuristic nature, actually has its roots in indigenous Amazonian practices.

According to historians, the process of creating it was modeled after a 2,000-year-old practice in the Amazonian basin. Here, indigenous peoples would mix terra preta or “dark earth” – a combination of low-temperature charcoal, rotted plant matter, animal manure and crushed terracotta – into the notoriously infertile Amazonian soil, in order to render it fit for farming.

Recent studies have found that this mixture was so potent that its effects on Amazonian soil are still being felt today. This is likely because of the ability of charcoal – one of its major components – to effectively bind and retain minerals and nutrients and then release them over time.

What is biochar like?

Biochar is a black, highly porous, lightweight and fine-grained material that has a large surface area.

While any organic material can be used to make biochar, experts recommend clean and high-quality organic feedstock or raw material. Ideally, the feedstock that’s chosen is one that has around 10 to 20 percent moisture and high lignin content. This include farm residues, woody biomass such as fallen trees and tree parts and energy crops, such as elephant grass.

These types of feedstock not only store more carbon than other sources but they also help minimize the risk of introducing toxins into the soil or drastically changing its pH, which can prevent plants from absorbing nutrients.

What benefits can we get from using biochar?

Biochar is best known for its ability to enhance the inherent properties in both soil and organic compost — an ability that can be traced to both its chemical and physical properties.

For instance, biochar has an interior layer of bio-oil condensates that act as a food source for both bacteria and fungi, thus spurring rapid decomposition of organic matter present in the soil and ensuring its speedy enrichment. In addition, biochar has a large surface area, which means that it can support large numbers of the said beneficial microorganisms

Aside from that, biochar particles are also quite small, a property that makes its easier for the particles to migrate deeper into the soil.

With that said, here are some of the benefits that biochar can impart on the soil:

  • Biochar can help enhance existing soil structure
  • Biochar can improve the soil’s water retention
  • Biochar can help address soil aggregation
  • Biochar can help reduce soil acidity
  • Biochar can help reduce nitrous oxide emissions
  • Biochar introduction improves soil porosity
  • Biochar introduction can help regulate nitrogen leaching
  • Biochar can help improve soil electrical conductivity
  • Biochar introduction can help improve conditions for microbes

In addition, biochar has also been found to be beneficial for composting, since it helps reduce greenhouse gas emissions as well as prevents the loss of nutrients in the material being composted. It has also been found to help reduce the compost’s ammonia losses, as well as its overall bulk density and even odor.

Using biochar in the soil can also help reduce the need for chemical fertilizers. This, in turn, can result in reductions in groundwater pollution, as well as waste production.

Furthermore, because of its ability to boost soil fertility, it can help increase yields for farmers, thus boosting their farm’s profitability and contributing to their food security.

How can I use biochar?

Using biochar is a pretty straightforward affair, albeit one that is dependent on several factors such as the health of the soil and its type.

As noted by experts, biochar can be applied to the soil in the following ways:

Use biochar as a top dressing – The easiest way to use biochar is to simply sprinkle it on top of the soil and then wet it. To maximize its nutrient retention properties, you can mix your biochar with some organic compost before laying it on top of the soil.

Incorporate biochar into your soil by tilling – One other way to use biochar is to incorporate into the soil by tilling. Simply add a biochar mix on top of your soil and then use a tiller to mix it right in. If you are planting in pots or raised garden beds, you can just use your hands or a small rake to work the biochar into your soil.

In addition, experts often recommend mixing biochar with organic compost and other amendments in order to load it with nutrients and beneficial organisms. This process, called “charging” is especially important if you are working with soil that is not fertile in the first place.

Is it possible for me to make my own biochar?

It may come as a surprise to some but biochar can be easily made in the safety and comfort of your own backyard. This can be done in two ways, both of which are very straightforward and easy:

Trench Method:

  1. Dig a trench or hole and put a mixture of dry wood and other dried plant materials such as cut grass and weeds into it.
  2. Set fire to the material. This will initially give off clouds of white smoke. Do not worry, as this is mainly water vapor. The smoke will then turn yellow as the resins and sugars in the organic material burn.
  3. Once the smoke turns grey, cover the burning material with soil, making sure to leave a small hole for air. This restricts oxygen, thus ensuring that the material will become charcoal and not ash.
  4. Once the material has fully transformed into charcoal, wet everything down with water. This will put the fire out and create micro-pores in the resulting charcoal with the thermal shock.
  5. Remove the covering and dig out the charcoal and prepare it for charging.

Cone Pit Method:

  1. Start by digging a cone-shaped pit around 60 centimeters in diameter.
  2. Cut wood into lengths of around 30 centimeters.
  3. Build a small fire in the base of the cone using dry twigs. Once the fire is going, add more twigs and then the larger pieces of wood.
  4. Add more wood once they start to turn black and develop a thin layer of white ash. Repeat until you run out of wood or until you reach the top of the pit.
  5. Once the topmost layer turns white from the ash, add enough water to fill the pit.
  6. Once everything has cooled down, remove the charcoal and break it up into small pieces. If the chunks are too big, you can place the charcoal into a bag and hit it with a hammer or large mallet. Crush the resulting charcoal until it is fine enough to pass through a garden soil sieve.
  7. Your biochar is now ready for charging.

Biochar is one of the best amendments you can use on your soil. Not only is it natural and safe, but it is also proven to be among the most potent when it comes to restoring soil fertility.

Use biochar and organic compost the next time you till your land or when you are preparing for another growing season.


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