How to make the greatest soil on Earth

Trivia fun fact: Everybody knows avocados are a fruit. Few people realize they're classified as single-seeded berries. Another berry? Bananas. Raspberries? Not a berry (botanically).

In today's newsletter:

• 🔥 The Big Idea: How to make (literally) the best soil on Earth

• 🌎 Natural wonders: How it looks when volcanoes erupt blue and other epic phenomena.

👨🏼‍🌾 Creating the best soil on Earth

Roughly 2500 years ago, villagers in remote stretches of Amazonian rainforests pioneered broad-scale use of one of the greatest soil-producing tools existing today.

The areas in which these tribes lived starkly contrast with their surroundings.

While the Amazon has no shortage of trees, it's one of the worst environments for growing edible crops. In many cases, the soil is so devoid of critical nutrients and concentrated with metal oxides that researchers consider it toxic.

Once inside the domain of these ancient tribes, soil tells a different story. Deep, rich pockets of black soil create islands of food productivity. Red, sickly-looking clay has disappeared, replaced by lively organic matter with worms and fungi.

So how did these tribes convert some of the worst soil into some of the most treasured? Was it a piece of technology you'd expect to find in an Indiana Jones movie?

The secret to Amazonian Dark Earths, as they are now known, has nothing to do with high-tech solutions and everything to do with the most basic of human tools: fire, wood, and bacteria.

These highly productive Dark Earths have a distinctive color attributed to a special kind of charcoal called "biochar".

Unlike the charcoal you throw on your grill for an afternoon BBQ, the charcoal tucked beneath the soil in the Amazon was first inoculated with bacteria, fungi, and loads of nutrients to sustain plants for thousands of years. On many plots, archaeologists have also discovered animal bones and large amounts of pottery chips, suggesting alternative sources for a wide spectrum of micronutrients.

In a minute, we'll talk about how you make this black gold called biochar. But first, how is biochar different from standard fertilizer?

Biochar vs Fertilizer

The Evolution of Fertilizer

Fertilizer in developed countries has evolved into a controversial product. Before the industrial revolution, fertilizers were typically made from animal dung, potash, and other upcycled byproducts of daily life.

These home-grown compounds helped to close the loop between production and consumption, making them an awesome tool for self-sustainable farms. To this day, small-batch fertilizer production is a must for any farm hoping to reach long-term sustainability.

After the industrial expansion in the mid-1900s, fertilizer transitioned into a highly manufactured product with a net-negative ecological impact.

In other words, most of the fertilizer used nowadays does more harm than good. Synthetic fertilizer production releases substantial volumes of greenhouse gases, and the end product tends to isolate the bare minimum of what plants require.

When synthetic fertilizers are over-sprayed, the chemicals are easily washed into waterways with the next rain. When these nutrients concentrate in rivers and streams, algae chokes out all other aquatic life.

Between chemical production and aquatic destruction, synthetic fertilizers constitute >2% of global carbon emissions yearly. Because fertilizers are short-lived, the emissions caused by these chemicals won't slow down.

Fertilizers are not ALL bad, and I can see how my writing looks a little jaded. It's important to know the downsides of a short-term solution, especially when the proven history of something as long-lived as biochar exists.

Now that we know more about fertilizer, let's talk biochar.

Biochar: Black Gold

Biochar, unlike fertilizer, lasts for thousands of years. And that isn't hyperbole — the soils Amazonian tribes treated with biochar are still loaded with compounds plants love.

Why is biochar so special?

Biochar combines charcoal, bacteria, fungi, and micronutrients to create a miniature fertilizer factory in the soil.

How?

During production, biochar converts the carbon found in trees and plants to a more stable structure. This new structure has tiny little pockets of air that provide a home for aerobic bacteria and fungi.

When inoculated with more nutrients, such as nitrogen from urine or compost, the bacteria transform an inanimate piece of burnt wood into a microscopic workshop that churns out fertilizer and nutrients for plants. The special form of stable carbon in biochar protects the system from decomposition, enabling the bacteria-powered factory to survive for millennia.

Another mind-blowing fact about these Amazonian Dark Earth soils: they regenerate themselves at a rate of over 1 cm per year without any human assistance.

Here's a comparison of Terra Preta (Amazonian Dark Earth) soil and regular Amazonian soil:

So how is biochar made?

The '-char' part of biochar comes from the main ingredient: charcoal. The charcoal for biochar is made by burning biomass like trees, woody perennials, or dung in the absence of oxygen.

Without oxygen, very little carbon is lost as carbon dioxide in the air, making biochar a powerful carbon-sequestering (net carbon negative) technique.

How do you burn in the absence of oxygen? Burn your wood in an in-ground pit or in a Kon Tiki Kiln. If you see ash forming on your pile, you have too much oxygen in your burn pit.

Note: If you find a little ash in your burn, hold onto it. Ash adds a nice bolus of potassium to garden soil, so it's not a complete waste if your charcoal isn't perfect.

Once you have charcoal, don't add it to the soil yet. Unactivated charcoal (fresh from burning) will leach nutrients from your soil and starve your plants.

To become fully-fledged biochar, charcoal must be activated with bacteria, fungi, and nutrients. This step is called charging.

There are a couple of methods to charge biochar:

Option 1: In the burn pit, soak the charcoal in urine for 2-3 days. While it might initially be a little gross, you can pee in a bucket for a day or two to secure enough liquid to completely submerge the charcoal.

Once sufficiently soaked, create a pile of biochar layered with cow or chicken dung. Let the pile sit for approximately two weeks to one month, occasionally turning the pile to spark organic activity.

Option 2: Soak the charcoal in compost tea or water for 2-3 days. Once soaked, layer the charcoal with finished compost, starting with a 10:1 compost: charcoal ratio. Let sit for 10-20 days, occasionally turning the pile for mixing.

After you've prepared your biochar, it's time to add it to your garden.

Activated biochar should be applied at root level (8-24 inches deep, depending on the plant) for maximum benefit. Instead of digging up large swaths of your garden, I recommend digging isolated holes between your plants and letting plant roots find their way to the treasure trove.

If you're a super-sized science nerd like me, you might enjoy experimenting with your garden to verify the benefits of biochar. If that sounds like you, split your garden beds into "control" (no biochar) and "experimental" (with biochar) groups. Grow the same plants in each group and compare your yields.

Bon gardening and biocharring!

🌎 Natural wonders for your eyeballs (10/10 guarantee):

• 😍 A shiny blue mushroom sprouting from a log

• 🕊 A flock of birds shaped like a giant bird

• 🌋 When a volcano bursts with blue lava

That's it for this week's newsletter.

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