How to Amend Your Soil: Building Better Garden Soil 101

Unlike the many elements of your garden you can’t control: The weather, the weeds that never quit, etc.— the quality of your garden soil is one of the few elements you can change. Not only that, but it’s a relatively straightforward thing to do that can significantly improve your garden’s overall success and bounty. So, if you’ve been wondering how to amend your soil for a healthier garden— you’ve come to the right place. Here’s everything you need to know about soil amendment and structure, plus our step-by-step guide to improving your garden soil. 

What Does it Mean to Amend Garden Soil?

Before we get into the details on how you can best amend your garden soil, it helps to know a bit about what amending soil means. When you amend garden soil, you’re just improving it by adding certain kinds of organic material according to your soil’s specific deficiencies. 

Most garden soils are imperfect and will benefit from adding organic fertilizers or compost mixes. But to truly amend your soil the right way, you’ll need to understand what your soil is lacking (or has too much of) and how you can fix it. Rather than just sprinkling a random fertilizer into your garden, it helps first to take the time to study your soil and come up with a game plan of what you’d like to improve and how you’re going to do it. 

Why Good Garden Soil Matters

Good garden soil matters because it’s the nutritional foundation of your garden. Besides, whatever they may gain from water and sunlight, your plants rely heavily on the quality of your soil to fulfill their nutritional needs. If your soil is lacking in accessible nutrients, your plants will suffer. 

Beyond the nutritional value of soil, you also want to consider the structure of your soil—since this is also important for healthy plant and root growth. We’ll get into some basic soil science next. 

Basic Soil Science 

When talking about good garden soil, the topic is two-fold. The first thing to consider is your soil pH, which determines just how acidic or alkaline your soil is. This bit of soil science is essential as it allows you to understand what kinds of plants will grow best in your garden and which ones won’t. If you’re unhappy with the pH of your soil, you can amend it by adding lime to increase the pH or sulfur to lower it. 

The second bit of soil science you’ll want to understand is your soil’s composition, also called soil structure. This aspect of soil science describes the size of your soil particles and how much space (for air and movement) is in between those particles. It also describes how easily (or not) water gets absorbed into the soil. The main types of soil structure are sand, clay, silt, or some combination thereof. Ideal soil structure is typically described as “loam” which is considered a perfectly balanced soil structure in the middle of the three aforementioned types. 

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Types of Soil Explained

Knowing which type of soil suits a particular plant is extremely important because the soil is crucial to a plant’s survival. It’s the soil that anchors and protects the plant’s roots, allowing it to absorb water from the ground. Soil can also contain lots of nutrients and minerals that help the plant to grow.

Different types of soils have different qualities regarding airflow and moisture retention. Some plants like well-aerated soil that drains water quickly. Others prefer denser soils that hold a lot of moisture for long periods.

Six main types of soil are recognized by most horticulturalists. The size of individual soil particles usually categorizes each type of soil. The smaller each soil particle is, the denser the soil becomes.

Denser soils provide less space for air or water to pass between the particles. Dense soils also compact more quickly, making it harder for a plant’s roots to grow. Soils that have larger particles provide more airflow and drain faster.

Common Types of Soil:

• Chalky soils: These soils vary wildly in density and can be light or dense. Chalky soils typically have a more alkaline pH than most other soils. Chalky soils lack nutrients and often contain a lot of stones.
• Clay soils: Clay soils have the smallest particle size of any soil and are incredibly dense. Clay soils are excellent at retaining moisture and nutrients. However, these slow-draining soils take a long time to warm up enough to plant safely.
• Loamy soils: Often described as the perfect soil, loamy soils combine the qualities of clay, sand, and silt. Loamy soils are easy to dig and drain well yet are still fertile and contain lots of nutrients.
• Peat soils: Although not often found in backyards, peat is used extensively in compost. Peat is mainly comprised of organic matter and retains moisture well. However, peat soils are acidic and lack nutrients.
• Sandy soils: Sandy soils are loose, gritty soils with large particles. This makes sandy soils easy to dig and very well-draining. However, sandy soils lack nutrients and will also start losing what little nutrients they have when it rains.
• Silt soils: Silt is formed from tiny particles of rocks and minerals. These soils are well-draining but can still hold a good amount of moisture and nutrients. However, silt soils can easily become compacted.

How to Improve Your Garden Soil (Step by Step)

Assess your soil

The first step in amending your garden soil is to determine precisely what it needs and your goals. These will partly depend on what you plan on growing in your soil. If, for example, you want to prepare a garden bed for veggies, this might be slightly different than if you want to prepare your soil for planting a large shrub. Remember that most plants thrive in slightly acidic, rich, well-draining soils (i.e. loam). If you’re unsure of the specifics of what your garden lacks, this can be a good general goal to aim for. 

Test your soil

If you genuinely want to get into the technical aspects of your soil and its needs, now’s a good time to order up a soil test. You can get one by looking up your local USDA extension office to see their soil test protocols. Most have online instructions and an address to mail in your samples, and they cost anywhere from $7 to $10. Alternatively, you can also try this basic at-home testing using vinegar and baking soda to get a rudimentary understanding of your soil’s pH. 

If you can’t tell the structure of your soil just by looking at it (or asking a fellow gardener), try this easy-at-home test to get an idea. 

Buy the necessary amendments

Once you understand what your soil needs (and how you’d like to improve it), it’s time to purchase a soil amendment. This will vary depending on what kind of soil you already have and what you plan on using your garden space for, but again— a good rule of thumb is to always add in nutrient-rich, organic material. If you can sync up with a local farmer to purchase some of their aged manure (make sure it’s been sitting for a while; otherwise, it will be too strong for direct use) or some of their compost mix—even better. 

When in doubt, “garden soil mixes” sold by local nurseries, manure mixes from turkeys, goats, or chickens, or even lightly processed compost will do just fine. Make sure you buy enough amendment material to be able to adequately mix it into the first 16 inches of topsoil at a ratio of ⅓ amendment to ⅔ native soil. 

Gather your tools

With your amendment materials ready, it’s time to gather up the other tools you’ll need for the job. For this, you essentially want tools that allow you to dig and mix your soil easily. A hand trowel and wheelbarrow might be enough. As an alternative (particularly in rocky or clay-soil gardens), digging might require a pick-ax and much larger shovels. 

My personal favorite tools to have on hand include garden gloves, a pick ax, large shovel, a hand trowel, a small hand rake, and a bucket. With these tools, I’m able to dig into the topsoil, remove it into my bucket, mix in the amendment, then add it back to the soil. Having the pick ax and larger shovel on hand help with digging, but also if you run into any large rocks (a near certainty in my garden)!

Break up the ground

The first step in amending your soil is to break up the topsoil. If you have mulch, be sure to rake it aside before starting this step, as you don’t avoid mixing mulch into your soil as much as possible. This is also an excellent time to remove any unwanted rocks, debris, or weeds from your garden soil. 

Add in your soil amendments

Once you’ve broken up the soil, you can add your amendments in several ways. The first way (my personal favorite) is to use a bucket or wheelbarrow, scoop your native soil into the vessel, and add in your amendment. Using a ratio of ⅓ amendment to ⅔ native soil seems to work well and will significantly change your soil without shocking the root systems of your established plants. This method allows you to get a good look at the state of your current soil and stir things up with your hands. You can also sift out any rocks or weeds you didn’t catch previously. 

If you don’t have a wheelbarrow or bucket on hand, you can still do the same process directly in your garden soil by adding in enough amendment and stirring it up with your hands or tools. 

Cover your soil

While this isn’t strictly part of soil amendment, it’s a good final step to ensure your soil’s ongoing health. The reason? One of the worst things you can do for your soil (especially when you’re trying to improve it) is to leave the top layer bare— which leads to dried-out, nutrient-deficient soil.

So before you pack up your gardening tools and call it a day, add a bit of mulch to your newly amended soil. This can be natural mulch around your yard (like leaves or pine needles) or the fancier stuff you get from the garden store. Alternatively, if you’re not a neat freak gardener, you can also consider planting some cover crops that will enrich your soil, add nutrients back into it, and can make for tasty toppers on your summer salads. Some favorite and easy-to-grow cover crops include clover, arugula, mustard greens, and alfalfa. 

The final word

While it does take a bit of time and effort, amending your soil is a worthy endeavor for any gardener. By improving the nutrition and composition of your soil, you’re almost guaranteed to have healthier, stronger plants—without the use of added chemicals or synthetic fertilizers. Prioritize amending your garden with organic materials, and you’ll be amazed at how intelligently your garden adapts to these nutritious additions and how happy your plants are.

To learn even more about soil science, check out the book Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web by Jeff Lowenfels.