Healthy Soil – What Is it and How to Build it

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Building healthy soil is the backbone of your vegetable garden and the cornerstone of sustainable living. But healthy soil is not something we stumble upon; we must actively build, cultivate, and nurture it. 

It’s sort of like crafting a masterpiece; creating healthy soil takes time to build. In this article, I aim to deepen your understanding of what defines soil health in an easy-to-understand way and why it is significant for your home garden. 

We will talk about what healthy soil is, its characteristics, how to tell if it is healthy, tips for creating healthy garden soil, and more so you can grow an abundance of nutrient-dense food in your vegetable garden. 

Updated March 2024.

What is Healthy Soil?

My Tennessee Master Gardener handbook defines it as “The naturally occurring, unconsolidated or loose covering of broken rock particles and decaying organic matter on the surface of the earth, capable of supporting life.” 

To me, it sounds complicated to think of it this way.  But, it’s really not once you understand what is in soil, how you can keep it healthy, and what makes up soil health.

A rich healthy soil is teaming with life. It provides an abundance of nutrients to plants through the bacteria, microscopic plants, microbes, organisms, fungi, algae, and all kinds of other animals that live in it.

Its texture holds water but also drains well. Its pH level will range from around 5.5 up to 7 and will contain many visible creatures such as earthworms and other insects.

6 Key Characteristics Of A Healthy Soil

There is difference between dirt and soil. A rich nutrient soil will have

1. Good Soil Tilth

• The physical condition of the soil in relation to suitability for planting or growing crops. Tilth includes moisture, degree of aeration, stability of soil particles, amendments, and more. 

All this said, tilth boils down to the texture of the soil. How it holds water, by too much or too little, how porous it is, which allows plant roots to breathe when it is not tight or compacted, and how well it sticks together to allow growing roots to absorb and consume the nutrients out of it. 

2. Good Drainage

• Healthy soil is porous and holds water but not to the point that it waterlogs to cause root rot. If you gently pour water or rain over rich, healthy soil, it quickly absorbs into it and holds inside the particles.

I’m sure you’ve seen this with soil in containers. They are left and get really dry, and when you water, it runs off to the sides, and the top has to get moist before it can be absorbed.

3. Low Weed Pressure

• Weeds in a garden indicate of soil nutrients. Some grow well in high nitrogen areas, while others indicate compaction or nutrient needs. This article from the Farmers Almanac is helpful for understanding weeds and how to read them to understand soil health.

4. Billions of Microorganisms

• Even though microbes are not seen with the naked eye, healthy soil is full of them. You must use a microscope to see these, but microbes help break down organic amendments and stimulate plant growth.   This article makes it easy to understand and helpful.

5. High Amount of Organic Matter

• Nutrient rich soil has a good supply of dead plant matter, such as leaves, straw, etc., that decomposes and enriches the soil as it is broken down by soil microbes. 

6. Neutral PH Level or Close To It

• pH measures nutrients available in your soil. The scale score ranges from 0 to 14, with 7 being neutral.  0 – 6.5 is acidic soil, and 7.5 – 14 is alkaline soil. 

A soil test is necessary to determine your soil’s pH level. Most vegetables grow best in soil with a pH scale of 6.0 – 6.5.

If the soil is too acidic, plants cannot utilize or take up N, P, K, S, Ca, Mg, or Mo (defined below).

Soil Fertility and Plant Nutrients

Nutrients and key components of healthy soils are divided into three categories. For a plant to be healthy and have all the nutrients it needs, it requires 16 different elements.

Carbon, Hydrogen & Oxygen are provided from air. And then the remaining 13 essential elements are:

• Macronutrients – Primary: Nitrogen (N), Phosphorus (P), and Potassium (K)
• Macronutrients – Secondary:  Calcium (Ca), magnesium (Mg), and sulfur (S) 
• Micro-nutrients – Trace Minor: Zinc (Zn) and manganese (Mn), boron (B), chlorine (Cl), copper (CU), iron (Fe), molybdenum (Mo) 

Though this all sounds complicated, a soil test measure these and can give you exact measurements of each component, and then you can decide what amendments you need to start building your soil. 

You can get a thorough soil test kit by contacting your local agriculture extension office.

Defining Soil Nutrients

Used to, when I heard terms like these above, my eyes would glaze over with no idea what they were talking about. This may or may not be you. If it is, I’m hoping I can shed a tiny light on it to help you better understand.

I can’t go into depth, as I’m not a chemist, but after many years of gardening, I have learned a few things about it.

The primary macronutrients are the THREE numbers found on fertilizer packages: 10-10-10, 5-5-5, etc.

1. Nitrogen (N)- First Number

Nitrogen promotes green leafy growth of plants and helps with photosynthesis, which is absorption of sun. The photosynthesis process uses the sunlight to produce sugars in the plant that feeds the leaves and stems.

• Deficiency of Nitrogen is yellowing of the leaves and stunted growth.
• Excess of Nitrogen causes excessive leaf growth with poor fruiting and flowering.

The first number of the three. If your soil test shows low nitrogen, and most likely will, since nitrogen is easily lost, you can add natural amendments such as:

• Animal Manures – cow, horse, chicken, bat guano, etc
• Blood Meal (12-0-0)
• Feather Meal (12-0-0)
• Grass Clippings (4-2-1)
• Alfalfa Meal (2-0-1)

Vegetable that need a lot of nitrogen are:

• Broccoli
• Cabbage
• Potatoes
• Leafy green such as Lettuce, Spinach, Kale, etc.

2. Phosphorus (P) – Second Number

Phosphorus, the SECOND number, helps to regulate the amount of water vapor, oxygen and carbon dioxide a plant is able to take up. Which is need for root growth, plant cell expansion, and helps a plant to resist disease. It provides energy to set flowers and fruit.

• Deficiency of Phosphorus leaves appear purple on the underside, the tops will turn yellow, then to brown on the edge and curl. Dead areas appear on the fruits and stems.
• Excess of Phosphorus plants struggle to take up micro-nutrients iron and zinc which result in stunted growth and yellowing of leaves.

When a soil test says that you are low on phosphorus, look for a higher SECOND number, and add organic amendments such as:

• Chicken and horse manure
• Fish Bone Meal (4-12-0)
• Bone Meal (3-15-0)
• Rock phosphate (0-3-0)

Plants that need a lot of potassium are fruiting vegetables such as:

• Watermelons
• Tomatoes
• Squash
• Peppers

3. Potassium (K) – Third Number

Potassium aids with metabolism, absorption of fluids in plant cells, and helps plants to resist disease.

• Deficiencies of potassium is the plant will decline in growth, the roots will be poorly developed and stems/stalks are weak
• Excess of potassium causes issues with uptake of magnesium & calcium

If your soil test says that you need to add potassium, look for the THIRD number and you can use:

• Langbeinite (0-0-22)
• Seaweed (0-0-1)
• Potash from Hardwoods (wood ashes) (0-1-3)
• Greensand (0-0-3)
• Banana Peels (.1-.1-2.3)

Vegetable plants that will use a lot of potassium are:

• Green Beans
• Zucchini
• Carrots
• Blueberries
• Sweet Potatoes
• Cucumber
• Green Peas

Typically, when you use NPK, these also include enough of the secondary macronutrients for plants to grow strong and healthy. If you learn to to understand the basics of NPK, your gardening skills will thrive.

Three Types Soil Texture

Soil health can be tilted to either of these three, but healthy soil will combine all three: 

1. Sandy Soil: Soil that is sandy drains quickly, and much of the nutrients is washed away with it. Too much sand in the soil is not a good thing. 

Lesson Learned:   We once bought garden mix at a local landscape company to fill our new raised beds. It contained way too much sand and wouldn’t hold water. We ended up buying topsoil and ground clay to mix with it. The result was a lot of weed seeds from the topsoil. Not a way you want to start new raised beds. 

2. Clay Soil: We have this in Tennessee. Clay is made up of tiny minute particles that stick together and form a hard, concrete-like texture. Plant roots have a hard time penetrating it to grow. It also holds water which causes water log and root rot. 
3. Loamy Soil: Best soil for gardening!  This is what you should strive to create and build.  Loamy soil is built by adding organic amendments. Loamy soil holds water but drains well. When it is held in your fist, it holds its shape, but easily breaks up. Loamy soil is the destination to strive for. 

RELATED: Even if you’ve never gardened before, this ultimate guide for beginners is for you! Learn everything you need to know from over 60 resources, all in one place, to be a successful gardener, including improving soil, cover crops, warm and cool season crops, organic amendments, fertilizing, watering, and so much more.

How can you tell if soil is healthy?

These are visible ways to indicate rich soil without a soil test. But, this said, I don’t recommend skipping the soil test. The cost is minimal compared to failed gardens. 

With a soil test, you will know exactly what your garden soil is lacking so you can then decide how to best amend it to begin building your rich nutrient soil. 

• Visibility of earthworms – healthy soil is teaming with life you can see and not see. Earthworms are a great indicator. Organic amendments are broken down and attract earthworms. 
• Dark in color – healthy soil tends to be dark and can look much like a chocolate cake. Most often, the darker it is, the richer it is in organic matter.
• Plant roots are well spread – Pull up a plant; if the roots are well-spread in all directions, this is a good indicator of healthy nutrient-rich soil. But the opposite is pulling up a plant with stunted roots, or the soil is a hard clump. Chances are the soil is lacking in nutrients.

What does poor-quality soil look like?

Though hard to describe, poor soil looks lifeless. It is most often hard and dry and will not hold its shape, it will not hold moisture when water is applied and often immediately run off. It can be hard to break apart in your hands.

Tips for Building Healthy Soil

Never Use Chemicals

• Use No chemicals – at all costs – chemicals kill everything, good and bad. The use of herbicides and pesticides kills the fungus, microbiomes, etc.  And it is dispersed by rain so it doesn’t stay in one place. Chemicals are not able to distinguish between beneficial insects, such as bees and other pollinators, and pests, therefore killing everything. Chemicals, organic or not, should be a last resort.

Often, gardeners are told to use organic fungicides to control pests, but again, these fungicides also kill beneficial insects that we need for pollination and growth. 

Limited Soil Disturbance

• Limit soil disturbance – creating healthy soil takes time, but any soil can be amended, no matter its state. Tilling makes it easier to work but destroys soil structure and function.

Tilling or soil disturbance immediately destroys soil aggregates (organic matter and soil minerals that form organized units that hold the soil together) reduces water’s ability to infiltrate into the soil and speeds up organic material breakdown. All of which have negative effects on soil.

You’ve heard the terms no-till or no-dig. This is what these refer to and why you shouldn’t disturb the soil if at all possible. 

Keeping Soil Covered

• Keep Soil Covered – nature does not like being naked! Bare soil always grows weeds to cover the surface anytime it is tilled.  When your garden soil is not growing a vegetable crop, always cover it with a cover crop to prevent weeds, and keep the soil’s microbes fed. Healthy soil always contains live-growing roots on it, not bare to keep the microbes and fungi fed.

Avoid Compacting

• Avoid Soil Compaction – For soil to be healthy, it has to be porous and have pore space (space between soil particles) to allow water and air infiltration and nutrients to get to plants.  

Soil compaction is caused by walking or stepping on the soil in planting rows.  To avoid this, never walk or step on garden rows. I use woodchips between rows/beds as walking paths. They break down over time and add additional nutrients to the soil.  Using raised beds is a great advantage for not walking on the soil.

Another way to break up soil compaction is to plant daikon radishes (*affiliate link) as a cover crop. Learn more about the best cover crops for home gardens.

Using Organic Amendments

• Add organic matter (carbon) – Always be proactive in your garden to build healthy soil. The more carbon the soil has, the healthier it will be. Here on our farm, this thought is always at the forefront of our minds. 

When organic amendments are added to soil, they break down and add additional nutrients. The dead above-ground breakdown of natural materials adds biomass to the soil surface that is absorbed by the soil and used as nutrients. 

Some recommended Organic amendments include

• kitchen scraps
• grass clippings
• leaves
• clean animal manures

This fun printable PDF list from the Tennessee Environmental Council will help with additional ideas for making compost to add to the soil.

Keeping Moist

• Keep Moisture Levels Consistent – plants need water to survive and thrive.  All too often, garden soils are left too dry, which causes plants to struggle. Maintaining moisture is key to a healthy soil. The less rainfall your area has, the more you need water.   

We use rainwater catchment and irrigation from Drip Depot to water (*affiliate link) our now 7,000-square-foot garden space. 

Some plants require more water than others. Fruiting plants like cucumbers, tomatoes, and peppers need more water than leafy plants like lettuce, broccoli, and cabbage. 

NOTE: The more organic matter your soil has, the more it will retain moisture. Knowing how and when to water is key to growing food and maintaining healthy soil. 

How to Care for Healthy Soil Once You Build It

Maintaining healthy organic soil once it is built is not difficult but necessary. Doing so only continues to improve your soil.  

These four easy tips will help:

• Each year, add 2-3 inches of organic well-rotted manure or finished compost
• To help retain moisture – mulch around plants with leaves or wood chips. These will break down and add nutrients to the soil
• Add at least 2 inches of organic matter or compost to your soil each year to replace what has been lost
• Grow a cover crop on your soil when it is not being used for gardening.  

The time frame for building nutrient-rich soil varies. But as you add to it each year, it only continues to improve.

More Gardening Articles You’ll Like:

• How to Use Eggshells to Build Calcium to Garden Soil
• How to Improve Soil Quality Naturally
• How to Make & Use Compost Tea
• Spring Gardening Checklist
• How Soon You Can Plant Garden in the Spring
• How to Create a Garden Map to Save Time
• What are Heirloom Seeds and Why Grow Them

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