The most important element in your garden is one that is often overlooked, ignored, and forgotten. And it’s right under your feet. Learn how to build a soil with our guide.
- Soil Science
- Steps to Building a Live Soil
- Consistent Application Will Lead to a Healthy Soil
All life on earth depends on soil. But only 10% of the earth’s surface is soil, and topsoil is only about 10 inches deep. This tiny sliver of the earth’s crust took billions of years to create and is one of the world’s most valuable resources.
Today, you will learn how to make the perfect soil for your lawn and garden.
Soil science is the study of soil formation, classification, and ecology(1). It tells us that soil consists of the following components:
- Mineral content – this is the inorganic part: the sand, silt, and clay. Sand particles are much larger than silt, which is larger than the tiny clay particles. These particles determine your soil structure and texture. Soil type impacts how well your soil drains and how nutrients are made available to the plants.
- Soil organic matter – this is dead plant material – roots, stems, leaves, etc., in various stages of decomposition.
- Soil organisms – the animals and insects, bacteria, and fungi that feed on the organic matter and cycle the nutrients that are in the plant material back into a usable form for other plants.
- Nutrients – Plants need about 20 nutrients for good health. Plants use these chemicals to complete life functions – from growing the first root to setting seeds at season’s end, these nutrients provide what a plant needs to live. And most of them come from the soil.
- Macronutrients – These are needed and used in large amounts and include hydrogen, oxygen, nitrogen, phosphorus, potassium, carbon, calcium, magnesium, and sulfur.
- Micronutrients – These are needed in smaller amounts: boron, chlorine, manganese, iron, zinc, copper, molybdenum, nickel, sodium, cobalt, and silicon.
The macronutrients nitrogen (N), phosphorus (P), and potassium (K) are the N-P-K that you see on a fertilizer bag and are needed the most after hydrogen and oxygen, which are provided by air and water.
Steps to Building a Live Soil
Step 1: Soil Testing
Soil tests help gardeners know what’s going on down in the ground. A test can reveal your soil’s type and structure, nutrient analysis, pH level, and amount of organic matter.
A Quick DIY Test To Determine Your Soil Type
To determine your soil type, examine its texture. A simple soil test anyone can do involves a clear glass jar, a few tablespoons of soil samples from around the garden, and water.
- Fill the jar half full with soil, then add water.
- Put the lid on the jar tightly and shake vigorously.
- Let settle for a few days.
The sand, silt, and clay in your soil will separate into layers, which will allow you to see your soil’s profile easily. Sand will be at the bottom, silt in the middle, and clay on top. If each section is equal in size, you have the gold standard of soils – loam!
Testing for pH, Fertility, and Health
To determine your soil’s pH, fertility, and health, it’s a good idea to do a soil analysis test every few years.
There are DIY soil tests you can buy online. However, if you want a more accurate and complete analysis of your soil, you can consider getting a professional test from your county extension service or a commercial soil testing company.
Take three to five soil samples from a few different spots in the garden and label the location – for example, “vegetable garden'” or “lawn.” If you have different areas you want to be tested, please try to keep samples from each different location separate. This way you can have specific recommendations for each area tested.
If you will be sending into a lab, take your collected samples and either drop it off or mail it to a lab. In a few week, you should have your report.
Soil test results will tell you:
- Soil pH level. pH stands for “potential for Hydrogen” and tells you how alkaline or acidic the soil is. Zero is highly acidic, fourteen is highly alkaline, and seven is considered neutral. Most plants like a pH around six or seven. The pH of soils is determined by mineral content, soil texture, climate, and water. Most of these elements are impossible to change – it’s better for growers to choose plants that will thrive in the soil they have rather than to try to change the soil pH!
- Soil fertility and health. Soil tests tell growers what nutrients are available in the soil and whether a nutrient is missing or lacking. Soil tests will also tell us if soil is lacking in organic matter.
- Recommendations. Soil analysis tests offer growers advice on what to add. The lab won’t call out a specific product, but the recommendations will let you know how much of a particular nutrient or element your soil needs.
Almost always, a soil analysis is going to recommend adding organic matter! Healthy soils have a good loamy texture, are nutrient-dense, hold water but are well-draining, and support root growth. We call these soils living soils, and we can build them.
Step 2: Understanding The Nutrient Cycle – Essential to Building a Living Soil
It may look like plain old dirt, but healthy soil is rich and diverse and very active(2).
Healthy soil life teems with organisms, all busily recycling dead garden material back into nutrients. Healthy soil needs protection and continuous replenishment. It needs organic matter and organisms to break the organic matter down.
When you feed the soil, you feed the plant.
Living soil is an ecosystem consisting of:
- Inorganic material that makes up a soil’s structure
- Organic matter in various stages of decomposition
- Insects, centipedes, worms, nematodes, microbes, fungi, and bacteria that feed on that organic matter. These tiny creatures are building soil.
Soil organisms release the nutrients back into the soil in a form that plants can access. This process is called nutrient cycling.
By performing these nutrient cycles, the soil is able to continue sustaining life. In a sense, the soil is a living thing itself. That’s how it gets its name – living soil.
Soil Can Be Depleted of Its Nutrients
A soil can become depleted when people break the nutrient cycle.
Take this all too common example:
A home gardener plants flowers and vegetable in his or her garden. The plant takes nutrients out of the soil. At the end of the season, dead plants are removed from the garden to make it tidy and as a garden “clean up”. The dead garden plant is tossed out and the soil is raked clean and smooth. There are now fewer nutrients in the soil.
Repeat this for a few growing seasons, and you no longer have healthy soil. And it shows: root development is not robust, growth stalls, and vigor is lessened. Insect and disease problems develop.
Many people then resort to chemical fertilizers and pesticides, but there is a better way. We can build soil!
Step 3: Protect and Improve the Soil That You Already Have
Before we move onto to building a living soil, let’s first talk about the soil you already have.
Maintaining or protecting your soil is just as important as building a living soil. To keep your soil in the best shape possible consider the following:
- First, do no harm. Try not to compact your soil – avoid driving on it with heavy equipment, walking on it, or working it when it’s wet.
- Feed your soil organisms, and microorganisms, too. Allow organic matter – also known as dead plants, leaves, stems, and roots – to remain in the garden to decompose. (“Decompose” means something is eating it.)
- Put back what you take out. Start a compost pile or bin where dead plants can be recycled and broken down by microbes. You can then add the compost back into your garden’s soil.
- Grow cover crops. Also known as green manure, cover crops are grown to be incorporated into the soil at the end of their growing season. Plants like annual ryegrass, winter wheat, and clover help replenish both macro-and micronutrients, and convert nitrogen in the air into a plant-usable form (this process is called fixing nitrogen). Cover crops can also help prevent erosion, and their roots create space for air and water to move through the soil.
Step 4: Living Soil Recipe
Natural soil building can take decades, but we can make our own garden soil mix that is rich in organic matter and feeds the worms, fungi, and bacteria that return the nutrients to your plants.
The Base Mix
- ⅓ part sphagnum peat moss
- ⅓ part perlite or pumice for aeration – this allows for air and moisture to travel through the soil, as well as room for root systems to grow
- ⅓ part high-quality compost and/or worm castings (aka/ worm poop)
You can also add any of the following amendments, depending on your garden’s needs.
- Wood ash – high in potassium and phosphorus, calcium, zinc, manganese, and iron. Useful for reducing acidity; a little goes a long way.
- Kelp meal – dried seaweed brings nutrients from the ocean to your garden – nitrogen, potassium, and phosphorus (N-P-K) plus trace amounts of micronutrients – especially calcium, zinc, manganese, iron, sulfur, copper, and magnesium.
- Crustacean meal – also known as crab meal is another gift from the ocean and provides nitrogen and phosphorus.
- Green manure – cover crops that help fix nitrogen in the soil.
Mix Your Ingredients
Gently mix the ingredients, then let your living soil sit – or “cook” – for at least two weeks, or longer if you can. This gives the microbes time to begin breaking down the organic matter and for their colonies to increase.
A word of caution about kelp meal and crustacean meal: raccoons and other gardens marauders might be attracted to the subtle fishy smell. It may be subtle to you, but it is strong to them. Until these products are broken down, keep them where animals can’t get them. Otherwise, they will dig, looking for the fish!
Use this newly built soil in trough planters, containers, raised beds, or as a top dress in your flower beds and vegetable garden.
Keep you’re the organic matter in your soil in tip top shape by continuing to make more compost.
Step 5: Make Your Own Compost
It’s not all that hard to make your own compost. And making compost is the easiest method of building soil.
There are lots of articles out there about the ratio of brown to green and rules about how often to turn it, but nature has been composting since plants first began and will do it for you over several months.
What to Put in Your Compost
- Garden waste, fallen leaves, and cut up twigs.
- Scraps of kitchen vegetables.
- Coffee grounds and tea bags.
- An occasional live earthworm.
What Not to Put in Your Compost
- Meat and bones, eggshells, cooking oils (these attract rodents and other animals)
- Noxious or poisonous weeds (like poison ivy)
- Diseased plants (diseases can be spread when you spread the compost!)
- Weeds that have already gone to seed
The smaller the pieces, the quicker the microbes will break them down.
It often takes several months to a year for compost to be “finished.” Finished compost looks like dark, rich, healthy soil.
You can then mix the compost into your garden at the rate of ¼ to 1 cup finished compost per cubic foot of soil.
Consistent Application Will Lead to a Healthy Soil
With consistent applications of compost and organic soil amendments, poor soil can become a healthy one. Returning dead plant material to the soil where organisms can recycle it keeps the nutrient cycle going and keeps your soil alive.
You will soon see improvements in garden health and vigor.
So don’t neglect your soil. Treat it like the living thing it is.