Module 2: Black Gold
How and why to grow good soil.
Introduction
Gardeners call it black gold for good reason. Rich fertile soil is the keystone of a healthy garden. It produces robust and disease-resistant plants that produce food full of flavor and nutrition. Eating this food makes YOU robust and disease-resistant. Fertile soil is able to hold and recycle nutrients over and over, making your garden more productive as time goes on.
Remember, it's not like you can dig up your neighbors' yard when your soil is exhausted. For a truly sustainable way to grow food, you need to grow soil that replenishes itself.
Why do I need to "grow soil" anyway? What about the dirt in my yard?
If you live on an urban or suburban lot, there's a high probability your soil is in pretty dismal straits. See, at some point before your current abode was built, the ground was levelled. The good soil was dug out, trucked away, sterilized, and sold in bags of “garden topsoil.” Yep, that’s right. Some company extracted the black gold, made a few dollars on it, and now you're just supposed to drive on over to the big home improvement store and buy that "garden topsoil" like a good little stooge.
Fight the power. Making your own good soil is right up there with saving seed as an act of peaceful sedition. With all the chemical companies, organic fertilizer makers, and self-proclaimed experts out there vying for your attention and money, deciding to DIY your soil is an act of defiance and self-reliance.
Working with living soil (instead of buying it sterilized in bags) is also an experience that connects us--body, mind and soul--to our place of origin and end. Alpha and Omega. Ashes to ashes/dust to dust.
Philosophical musings aside, I want to emphasize right up front that I'm advocating for simple, practical, and very inexpensive (mostly free) ways to improve your soil.
Building healthy soil is actually a pretty straightforward process. Ironically, millions of people are convinced--by advertising of course-- that it must be very complicated. A Search for “How to Improve Soil” will yield a bit of information and a whole lot of product advertisements! Even if you dismiss the chemical products, the “organic fertilizer” and “natural amendment” dealers can be just as pushy.
What are they pushing? Well, their products of course. First, you have to buy a test for your soil. Then you are advised to amend your soil based on the test result--with the products they sell. They may also try to sell you a soil consultation to inform you which plants require more of each nutrient so you know exactly how to feed the soil for each and every plant.
Hmm, sounds very complicated. Do you really want to spend your time outdoors with little containers and baggies, measuring out powders and potions to each part of the garden?
But the real issue I have with specific prescriptions is that they aren't regenerative--and therefore unsustainable. Bone meal, blood powder, dried kelp, etc might be natural but you still have to buy them and they are often highly processed animal by-products, or extracted from riverbeds and oceans. These soil boosters might come from nature, but it is much more sustainable not to depend completely on store-bought stuff.
How Soil Works
Without getting too technical, it's important to understand what soil is and how it works. Once you know the basics, it's easy to see why simply adding organic matter and compost is the most holistic and long-term effective way to build soil fertility.
Scoop up a little earth. What do you see? A combination of clay, sand, silt, maybe some bits of leaf or twigs. Now, here's what you can't see: One teaspoon of that soil holds a billion bacteria, millions of fungi, and thousands of amoebas.
Soil enriched with plenty of organic matter can hold up to a hundred times as many beneficial organisms. An acre of soil can easily host four tons of worms, ants, millipedes, and mites, a construction crew of soil-builders.
Soil grows because it is pulsating with life. As the inhabitants of this lively underworld carry on their business of crawling, eating, excreting, and dying, pieces of organic matter in the soil (mulch, fallen leaves, pulled weeds) are broken down into nutrients for your plants.
Organic matter in soil doesn't decompose by itself — it is digested.
This natural digestive system is more efficient than anything we’ve devised in a bottle. Plants can access nearly all of naturally occurring organic matter digested by soil organisms without wasteful or toxic by-products. Feed the tiny animals in the soil and they will feed your plants--not only once but continuously.
The Story of terra preta
Even the poorest of soils can be improved. My favorite example of this is terra preta, human-made deposits of rich black fertile earth dotted throughout the hard red clay of the Amazon basin. Terra preta de índio literally means "the black earth of the Indians." They didn't find it already there. They made it.
How did they do it? The first terra preta deposits likely began as "garbage" piles. Amazonians heaped up kitchen waste, bone, and excrement with palm leaves and other vegetation. To reduce the size of the piles, they burned them in controlled smoldering fires. The smolder produced chunks of blackened organic matter called biochar.
Today, soil scientists are studying and documenting the remarkable abilities of biochar to hold nutrients in soil. The existence of terra preta has exciting implications for regenerative agriculture today. Terra preta is an outstanding example of how careful human intervention can improve soil fertility, in contrast to extractive farming methods that destroy it.
The techniques that produce terra preta are relatively simple, accessible, very inexpensive, and often free. Anyone from the backyard organic gardener to the large-scale regenerative farmer can do it--including you!
How-To Instructions
2.1 How to Make your own terra preta (Dig down method)
If you're going to plant in the ground, following the terra preta model is definitely a good way to go. Many terra preta deposits in the rain forest are more than a thousand years old and are still actively farmed today — without adding additional fertilizers. Those who can learn from the past will be rewarded with healthy plants and abundance.
Open up the Ground
With a spade or mattock, open up the surface (just the top 4-5 inches) of your chosen spot. Remove any remaining grass sod. Patches of clover, violet, and wildflowers don't need to be removed, just cleave into the soil with your tool to unearth them a bit. They'll rebound, not to worry. Don't pulverize the dirt into powder. Leave the soil full of clods (aggregates) to hold nutrients and house earthworms.
Add Compost & Manure
The first terra preta deposits likely began as big compost piles. Amazonians heaped up kitchen waste, bone, and excrement with palm leaves and other vegetation. They noticed that the seeds germinating in these piles grew into bigger healthier plants.
You can make compost too. Believe me, it's easier than you think. We'll get to all the different composting methods in an upcoming module--once we get our first wave of seeds and starters in the ground!
For a quick natural soil boost, you can't beat manure. If your town or city has mounted police, it's very likely you can get stable bedding for free. Aged manure mixed with straw won't have a bad smell, just an earthy horsey scent. Also, a little goes a long way. Two large sacks of stable bedding is enough to fertilize a good 100 sq feet.
Gently fold the compost and manure into the opened soil surface, not too deep. The roots of most cultivated plants (excepting some mature perennials) are rather shallow and best access nutrients in the top 4-5 inches of soil.
Fire it up
In addition to kitchen waste and poo, the key ingredient in terra preta was charcoal or charred wood. Amazonians burned their waste in low temperature controlled fires. Because these fires smolder rather than burning hot, essential carbon is retained in the soil instead of going up in smoke. The resulting "biochar" boosts long-term soil fertility because it binds with soluble nutrients that otherwise wash out of soil before organisms can get them.
To make your own home-scale biochar, you will need a wood burning grill, or a fire pit. Add the blackened chunks of wood remaining after a fire directly to your garden along with lots of composted organic matter. You can also add the ashes as a soil booster.
2.2 Making a Sheet Mulch
Also known as a "no dig" or "no till" garden bed, sheet mulch is like a big multi-layered lasagna of organic materials, topped with a spread of compost-enriched soil. You simply pile up the layers and let nature do the rest. Over time, the bulkier matter in the layers of the pile break down by composting in place into a rich, fertile growing medium.
Benefits of sheet mulch
Cultivates long-term soil fertility
Smothers and suppresses weeds
Shelters beneficial insects over the winter
Provides an ideal medium for microbes to flourish
No digging or soil turning required
Easier on the body. Organic materials, while bulky, are light and easy to pile up and mix
The ideal time to start a sheet mulch bed is in the fall so the microbes in the pile can work on the bulky matter over the winter. Also, dry leaves--one of the best materials to add in bulk to the pile--are readily available as bags of raked leaves sprout from sidewalk curbs (No, you're not "stealing" if you claim the "yard waste" for your mulch pile).
However, it's still very possible and beneficial to start a sheet mulch at any time. There's just two additional considerations:
You will need to source the materials from a bit farther away than your own curbside. They are still readily available--and often free. See 2.5 Organic Material Resources
You will also need a top dressing of compost enriched soil to plant seeds and starters.
Intrigued? Ready to give it a go? Here's how.
Source the organic materials.
Search your local resources and find out where you can get bulk materials inexpensively or for free. Many services, like landscape companies, will deliver various cuttings and clippings right to your door.
Get your materials in roughly the right proportions.
See the diagram below for an approximation of what you will need. The pile will work best with approximately 70-80% dry "brown" materials like leaves or straw and 20-30% fresh "green" materials like manure or grass clippings. Don't worry about being very precise. Nature is flexible and you can always make adjustments when needed.
Be sure to err on the side of excess when ordering or picking up material. It takes quite a bit to make a 1 foot pile!
Return to the spot where you are shading out the grass.
Leave the materials (cardboard, newspaper etc) right where they are! They will continue to decompose in place. You can pile your materials right on top.
Using the diagram below as a guide, build up your sheet mulch.
Wet down each layer so it stays in place and kicks off the composting process. A well-stacked sheet mulch will hold its shape. Be creative with the shape. Why be square? Ovals, circles, and serpentine patterns all work and make for a nature-inspired garden.
2.3 More Soil Builders
Spread Mulch in Your Garden
Thick mulch is good for suppressing weeds. A generous layer of organic mulch also provides food and cover for crucial soil critters. Worms tunnel up to the surface to chomp on moist bark chips, straw, or leaves, creating aerated spaces in the soil and leaving their nutrient dense casings for your plants. Fungi and bacteria dine on the remains, boosting fertility even more.
Note: You don't have to buy mulch! Most towns and cities have free leaf/yard waste pickups and landscaping companies are often glad to drop off huge amounts of tree clippings for a small delivery fee. See 2.4 Organic Material Resources
Mulch also protects your soil from wind erosion and prevents nutrients from being washed out by hard rain. Remember, bare soil is bad soil.
Chop and Drop
Soil organisms are opportunistic scavengers and will eat anything in the garden you don't. Not all the nutrients plants take from soil goes into the parts we eat. The stems, foliage, and root hairs are all excellent food for soil life. When you harvest vegetables, don't "clean" the "debris" — the carrot tops, squash leaves, or cucumber vines. Sure, you can put it in the compost bin, but it's easier to complete the cycle by chopping it up and leaving it on the soil. Insects and microbes will make short work of chomping it down into digestible nutrients and your remaining plants get a noticeable boost.
Cultivate Diversity
Finally, even the soil scientist types are starting to agree on one important thing: the plants growing in soil matter just as much to soil health as what you add to it. Grow plants of different sizes, root depths, nutrient needs, and types of foliage, fruit, and seeds.
A diversity of plants will work in myriad ways underground to build soil fertility by feeding microbes, interacting via sugars and enzymes, and networking with fungi. Plant an exuberance of life and yield an abundance of benefits for you and the soil.
2.4 Organic Material Resources
In a pinch, of course you can usually find bags of leaf compost and "top mulch" (shredded bark) at a large home supply center. But if you think outside the big box store, you can discover a wealth of free or at least VERY cost-effective resources for all sorts of organic materials.
Particularly if you are going to make sheet mulch or fill above-ground containers/raised beds, you will need a real abundance of organic materials. I recommend doing a Search online for the resources available to you locally.
Here is a quick guide to assist you in your search.
Leaves & shredded bark
Check the website of your local government. Many cities and towns have free piles where you can pick up as much as you can take with you. If you don't have a vehicle, consider borrowing or renting one to make the trip. Or, offer to pay or trade with a willing neighbor.
Note: For sheet mulch, make sure you get shredded bark and not the large wood chips. Larger chips are good for walking paths, but take a very long time to compost down in a pile.
Stable bedding (straw & manure)
A horse stable is the obvious, but also check with the local police. If your city has a department mounted police, those horses have to sleep somewhere! Check for pick-up hours, you can usually take as much as you're willing to shovel. This combination of brown and green material is ideal for sheet mulching and well worth the effort. If you have kids, they can help!
Tree cuttings, grass clippings & other "yard waste"
Call any local arborist or landscape company. They will deliver sacks of future black gold to your door for a modest fee.
Brainstorm Exercises
Go outside and do a "sensory soil test." Scoop out a little earth from your ground space.
Look. What observations can you see?
Feel. Pinch a clod of dirt and rub it between your thumb and fingers. What does it feel like? Grainy? Gritty? Clay-ey?
Smell. How would you describe the smell of earth?
Take note of your impressions; write in your journal if you have one.
There's no "right" or "wrong." Observe and be with what is.
Reflect on the word humus. Think of all the closely related words: humble, humility, humanity. Human. Be with these relationships of language and our material world. Immerse yourself in the revelation of connection.