Is Biochar the Secret to Better Soil? How to Make & Use This Ancient Soil Amendment in Your Garden

We love our plants. But to grow healthy specimens we often use unsustainable ingredients like peat moss or quick fixes like synthetic fertilizers to get the results we want. But there are plenty of great organic options that are better for the environment and better for our plants, like biochar

Biochar is a unique soil amendment made from charred organic material. It’s been used to boost soil health for thousands of years, yet not many gardeners know about this amazing and sustainable solution.

So what is biochar and what are the benefits of using this particular soil amendment? Keep reading to learn about the pros and cons of this underrated fertilizer. Plus, learn how to make biochar at home and use it in your garden.

What Is Biochar?

Biochar is a fine-grained charcoal created by burning wood and agricultural byproducts slowly at low temperatures with a reduced oxygen supply. This process, called pyrolysis, releases biological oils and gases, leaving behind a solid pore-filled material composed of at least 80% elemental carbon.

The open pores of biochar allow air, water, and nutrients to flow to plant roots while creating a home for beneficial microorganisms. The superheating process also kills weed seeds, pathogens, and other organisms that are harmful to plants. Today, biochar is especially valuable in areas with inadequate water supplies and severely depleted soil.

Although biochar is a new term, its use in gardens is not new. Researchers believe that early residents of the Amazon rainforest used biochar to improve soil health 2,500 years ago.

These ancient peoples produced biochar by burning agricultural waste slowly in trenches or pits. They grew tree fruits, corn, and cassava melons in soil mixed with mulch, compost, and biochar. Evidence of this ancient gardening practice can still be found in the enriched soils of the Amazon Basin.

Biochar can be made from almost any organic material from food processing residue to forestry cuttings to animal manure. The carbon-rich material decomposes slowly, taking hundreds or even thousands of years longer than peat, making it a sustainable alternative to peat moss for gardening.

Benefits of Biochar

There are many environmental benefits of biochar. It can combat climate change by removing harmful carbon from the atmosphere. Plus, the creation of biochar also produces gas and oil byproducts that provide clean, renewable fuel.

Biochar has many benefits for your plants, too. It provides better water retention than perlite, reduces fertilizer runoff and use, reduces the need for annual amendments of organic matter, creates a better microbial activity than compost, neutralizes soil acidity, and increases nutrient content – especially in sandy soil.

There does seem to be a distinct advantage to the use of biochar over organic matter to improve the aeration of dense, poorly draining soil. The use of other organic matter, like compost, emits carbon dioxide, methane, and nitrous oxide.

Disadvantages of Biochar

On the downside, biochar can take years to reinvigorate garden soil and improve crop production, it may be made from any number of organic materials each with its own pros and cons, and it can be pricey to purchase.

Regardless of its use thousands of years ago, biochar is a relatively new soil application. While scientists are still studying its benefits and detriments, it’s important to note there is no industry standard yet and one biochar may vary greatly in composition from another. So it’s important to do your research before purchasing and using biochar.

This biochar from Harris, a heritage garden brand, is a good option that’s made here in the U.S. Or if you’re looking to give your lawn a boost, this mix of biochar and humic acid is a solid choice. Both are available on Amazon. Another alternative is to make your own biochar at home.

How to Make Biochar

You can create biochar in your own garden by burning brush, wood shavings, dry weeds, and other garden debris in a trench. Light a hot fire so the oxygen supply is quickly reduced and then let the fire burn down.

Initially, the smoke from the fire should be white as water vapor is released, then gradually turn yellow as resins and other materials are burned.

When the smoke is thin and grayish blue in color, cover the burning material with about 1 inch (2.5 cm) of excavated garden soil. Allow the material to smolder until it creates chunks of charcoal, then extinguish the remaining fire with water.

How to Use Biochar

You have to “charge” biochar before using it in your garden. Charging the biochar means mixing it with an organic material – usually compost – to introduce a variety of microbes and nutrients. After mixing, leave your biochar to charge or activate for two weeks.

After two weeks, your biochar is ready to use. Use it in the garden as you would compost. You can sprinkle it on top of the soil or amend soil around existing plants by sidedressing plants with biochar. You can also dig the chunks of biochar into your soil or mix them into your compost pile.

Although charcoal briquettes for your grill or barbecue may look similar to biochar, they usually contain solvents and paraffin that can be harmful to your garden. So don’t try to use those. If you don’t want to make your own biochar at home, you can purchase ready-to-use biochar on Amazon.