Every gardener knows that their garden soil is where the magic happens. The structure and quality of your soil can dictate harvest size, time it takes for plants to mature, diseases to spread, and even pest control! However, soil is often a mystery to gardeners. There typically aren’t many aspects of our lives where we’re learning to observe the relationship between the soil and the crop (or the pollinator, and the sun, and the water - so on and so forth, a monologue for another time). But, when it comes to soil health, learning to observe this relationship can be one of your strongest tools!  

Understanding Soil Health in Your Garden

You don’t have to be a scientist to understand the basics of your garden’s soil health. Many problems start below ground, and if you just understand what to look for and what tools are at your disposal, you’ll be identifying problems and applying solutions in no time! 

Why Soil Health Matters for Your Garden

If you’ve ever seen a soil profile, you know that there are different layers to soil. The top two layers are typically what we grow in; the organic matter and plant litter layer as well as the top soil layer. These layers are chock-full of organic matter, living organisms, bacteria, and fungi that all help to maintain soil health. Below these layers are the subsoil, substratum, and bedrock. Understanding how our soil functions can contribute to understanding your garden’s overall health. 

Believe or not, healthy soil is very much alive. Just like any other living thing, soil requires air and moisture and input to function well. The more alive and healthy the soil is, the more it can put out into the world in the way of supporting healthy crops and plants! 

The water and nutrients your crops receive all come from the soil. Healthy and evenly balanced soil results in stronger, more resilient plants. Healthy soil can help preserve the health of plants during extreme weather like drought and heat. Certain soil characteristics can even affect how efficiently plants take up nutrients from the soil! Nutrients may be available, but certain aspects of the soil might make them hard to access for many crops. 

What “Soil Health” Actually Means

So, what are the aspects of soil health that you should take into account when considering your own garden? These elements are traits to keep in mind throughout your growing season, but are also what a soil test will help you to evaluate. Understanding these traits of your soil will also help you visually assess your soil quality annually. Understanding what healthy soil in your garden looks like can make it really simple to know how to amend your soil much of the time! 

Soil pH

The pH of the soil measures the acidity or alkalinity of the soil. Climate, mineral content, and topography can all affect the pH of your soil and this can be reflected in crop performance. Most crops will do best with a soil pH between six and seven, so slightly acid of neutral on the pH scale. Now, it does in part come down to what kinds of crops you’re growing. You may want a different pH in the part of your garden where your blueberry or hydrangea bushes are, as these plants love acidic soil. While most plants want this pH between six and seven, certain crops like brassicas, asparagus, and legumes can grow nicely in a slightly alkaline soil. Nutrients tend to be less available in both highly acidic soils and alkaline soils. 

Nutrient Levels

Nutrient levels can be depleted by weather, continuous or overplanting, or just the act of gardening without putting resources and organic matter back into the soil. The macronutrients of soil health include nitrogen, phosphorus, potassium, calcium, and magnesium. These are the main nutrients that contribute to plant growth and health. There are also a series of micronutrients that need to be present, however in smaller quantities. These include zinc, iron, manganese, and more. Certain soil tests can help you determine which of these are missing or need to be bolstered with fertilizers or organic matter. 

Soil Texture

Soil texture varies by topography, region, and the ratios of sand, silt, and clay that are contributing to soil makeup. The perfect soil is considered “loam.” This soil is made up of an equal ratio of clay, sand, and silt, producing a well-draining, moisture and nutrient holding topsoil. Very sandy soils tend to drain well, but are limited in nutrients. Very clay soils tend to be relatively high in nutrients but extremely dense and hold onto moisture - sometimes too well. Silty soils can be extremely fertile, allowing for decent water retention and airflow, however, it is prone to erosion, easily compacted, and may not offer the necessary nutrient availability for the average garden. Loam soil can be naturally present in any garden, but more likely is a result of the gardener tending their soil to reach this natural makeup through mixing in compost and organic matter, aerating their soil, limiting tilling, and more. 

Organic Matter

We’ve name dropped organic matter a few times now, but who is she? When we refer to organic matter, we’re talking about any plant or animal tissue that is in some stage of decomposition. A good example of this is compost. Compost is simply organic matter decomposed, so when you add this to your soils, you’re adding organic matter. The decomposition of organic matter, aided by the living organisms in the soil, adds nutrients into the soil which are then available for plant consumption. 

Presence of Earthworms

The presence of live organisms in your soil is generally a great indicator of soil health - especially so when it’s chock-full of earthworms! But how many should you find? Use a shovel to dig up one cubic foot of soil. Break it up and look for worms! If you find at least ten earth worms, this is a great indicator of soil health. 

The first test of soil health a gardener should do is visually inspect these aspects and qualities of their soil. It can offer a wide range of information! 

How to Test Soil Health in Your Garden at Home

Assessing soil health can come through a number of avenues including observation of crop growth or performance, soil quality or compaction, what lives within the soil, water absorption capacity, and more. However, sometimes it’s helpful to run actual tests to determine the specific causes of your issues and apply specific solutions. 

Tools You Can Use to Test Your Soil

Besides your own expertise on the growth of your garden, there are several tools and avenues you can use to test your garden soil. These tools come in handy when you’re looking for more specific information about your garden soil, or are stumped as to what could be wrong! 

State Extension Agency

One of the great resources in every state! Your local extension agent has a wealth of knowledge and information to help growers of all skill levels - you don’t have to call yourself a farmer to use this resource! But beyond asking questions, your state extension agency will also test your soil. Most states offer free or low cost options for getting your soil tested and get back to you with an extremely in-depth analysis of your soil. More than the typical home-grower needs, but this is by far the best and most accurate way to learn information about your soil health. 

Home Soil Test Kits

If you’re not looking for something quite as in-depth as the state soil tests, then we highly recommend these easy to use soil test kits for gardens. You can read all about how they work on our blog, but the short of it is that this affordable kit can get you quick results that you can act on right away, rather than waiting weeks for an official result from the state. It measures basics like pH, nitrogen, phosphorus, and potassium in your soil, but doesn’t address any micronutrients. 

Digital Soil Meters

There are a range of digital soil meters on the market that digitally measure moisture levels and pH. These can be a useful tool for collecting very broad-range data about your soil. For super accurate information, you’d want a high end digital soil meter, but the more affordable soil meter options can give you a big picture peek into the pH of your soil. These are useful if you’re just keeping an eye on the quality of your soil for any reason. For instance, if your garden bed is built with cement blocks or is against a cement wall, the soil can become more alkaline over time. A digital soil meter can help you keep an eye on this trend generally so that you know when to amend your soils. 

When You Should Test Your Garden Soil  

While you should be observing the quality of your soil throughout every garden season, you don’t necessarily need to test your garden soil every single year. On average, we recommend conducting a comprehensive soil test, like the one the state extension offers, every three to five years. For sandier soils, found most often in gardens along the coast, water and nutrients drain faster, so a soil test is recommended every two to three years. 

This of course is the recommended cadence for gardens that are pretty well-functioning. If you’re having active problems, or find yourself using a lot of fertilizers and amendments to resolve issues, an annual soil test can really help you focus in on what will help in the long term. Basic at-home soil test kits as described above can make a great addition to any garden arsenal and can be a low effort way to check your soil health at the beginning and end of each season! This is not strictly necessary, but can help you narrow in on soil amendments to apply in the fall so they’re available to spring crops. Some other instances where you may consider getting your soil tested are when starting a brand new garden or building a new garden bed, when plants are consistently showing signs of nutrient deficiencies, or when plants struggle to thrive and appear stunted in growth. 

So it’s been a few years and it’s time for a soil test! What time of year is testing most useful? We recommend getting your soil tested in the fall or winter. Knowing the information regarding your soil health ahead of a growing season can help you plan your garden around the needed support. For instance, maybe you learn that your soil is really low in nitrogen. With this information, you can plan to grow a bio-mass building spring cover crop ahead of any planting you do that coming season. This will set your future crops up for success. 

How to Collect a Soil Sample Correctly

Different types of soil tests will have specific instructions in regards to how to take a soil sample. Between all of them, they will share that you’ll want to get samples from a range of areas in your garden as well as a range of depths. 

Identifying Locations

If you’re doing a thorough soil test, you should plant the various sections of your garden separately. For example, you have three in-ground garden beds on a flat piece of land. These would be one section. But in the front of your house, slightly downhill and sloped, you’re growing berries. This is a different topography with a different management history, and should be considered a separate section from your vegetable garden, therefore you should take a separate sample. 

Samples and Subsamples

In each area that you indicate for planting, you’ll want to be sure to take subsamples. This means taking soil samples from around your identified area. For instance, in your in-ground garden location, you can take a sample or two from each bed, mix them all together, and take a portion of the mixed soil as your sample to mail in. An average of 15 to 20 subsamples from each section is a good rule of thumb. This ensures that there are no anomalies in the section you choose. 

Tools for Collecting Soil Samples

Folks that are doing a lot of soil sampling may want to consider investing in a soil probe. This is a tool that makes taking soil samples easy - just stick it in the ground to get a nice even core of soil. But the average gardener may not have access to or even need this. A similar process can be done with a shovel or trowel! 

To use a shovel, dig into the earth straight down to six inches deep. A mark can be made on the shovel to indicate this depth - you’ll want to keep it consistent throughout your samples. Tilt the shovel back to remove the shovel-full of soil. The shovel will have left a smooth face behind. Using a trowel, remove a thin slice, about one inch thick and one to two inches wide, of this face. You’ll want there to be equal representation of each layer of soil. Take care to remove any roots or rocks that you may come across in your sampling process. Now, just repeat this step in each of your subsample settings! 

Once your subsamples are collected, use a clean bucket - something that hasn’t come in contact with fertilizers, composts, or other parts of the garden - to mix your samples together. The test you use will tell you what quantity of this mixture you should provide for accurate results. 

Tips for Collecting Your Soil Sample

Avoid anomalies in the landscape.

Sampling your soil in areas with unique attributes can sway the results of your test. Avoid areas where:

• There was recently a compost pile. These spots tend to be very high in nutrients

• There are fence lines or walkways. Sample where you’re planting. 

• You’ve recently applied fertilizer. This will make your soil seem higher in nutrients than it is! 

Use the right tools. 

A soil probe can really improve the process of collecting soil samples, but whether you’re using a probe or a shovel, just be sure to use tools that will get you deep and get you an even sample. Don’t run into the garden with a spoon and butterknife expecting to get what you need! 

Avoid cross-contamination. 

Using clean tools and containers to mix your soil sample will ensure that your results are accurate and do not represent any fertilizer contamination or different areas of your garden. 

Mix your soil samples 

Mix well! For the most accurate results, you’ll want even samples - so don’t just skim from the top! 

Pay attention! 

Incorrect sampling can produce inaccurate results, which makes the process ineffective. 

Simple DIY Soil Tests You Can Do at Home

There are also a few helpful DIY tests that can be done at home with materials you likely already have in your kitchen! While these won’t give you the details an official soil test can, they can help offer a big picture understanding of your soil. 

Soil Texture Jar Test

This simple test will help you determine the rates of sand, silt, and clay content in your soil. Having an idea of what type of soil you have can inform how you care for it and what amendments you might consider mixing in. 

Step 1

Locate a clean, wide mouth, straight-sided, clear jar with a lid such as a peanut butter container or mason jar. Take a soil sample as directed in the previous section, increasing the quantity of the sample to fill the jar one half of the way full. 

Step 2

Fill the jar to the shoulder with water. Set the jar aside with all the soil to soak up the moisture. As it sits, locate a watch or timer and a ruler. Place the lid on the jar and shake vigorously for three minutes. 

Step 3

Set the jar on a flat surface and check your watch or set a timer for one minute. With the ruler, measure the amount of sediment that has collected at the bottom. Record this number. This is the amount of sand in your soil. 

Step 4

Now set the time for five minutes. Measure the height again. The accumulated height is the amount of silt in your soil. Subtract the first number from this number and record. 

Step 5

Let your mixture sit for 24 hours. The difference between the second measurement and the third measurement taken at 24 hours is the amount of clay in your soil. 

Step 6

Divide each of these recorded measurements by the total height. This will give you decimals that you can multiply by 100 to find the percentage of each that is in your soil. It should add up to 100%. 

The highest quality soil is made up of 20% clay, 40% silt, and 40% sand. With this test, you’ll determine the makeup of your own soil and can amend as needed.

Vinegar and Baking Soda pH Test

With just a couple of pantry staples, this simple test can help give you a general idea of your soil pH. While it won’t give you a dialed in perspective, it can be a quick way to determine some basic information. 

Step 1

Collect a soil sample as directed above. Mix your sample well. 

Step 2

Locate two bowls and a tablespoon. Put two tablespoons of your soil sample in each bowl. 

Step 3

In the first bowl, add ½ cup of vinegar. If the mixture starts to fizz, you have alkaline soil. 

Step 4

In the second bowl, add two tablespoons of distilled water and a ½ cup of baking soda. Mix, and if the mixture fizzes, your soil is acidic. If the soil has not reacted to either test, it is neutral. 

As you can see, this kitchen-counter experiment can give you a basic understanding of approximately where your soil pH lies. 

How to Interpret Soil Test Results

Every test result is going to come in a different format. Particularly if you’re getting a professional test! The lab or tester should include or have access to the directions to interpretation. Once you understand the results, here’s how to interpret the facts. 

Understanding Soil pH

Your soil pH results will indicate if your soil leans more acidic, alkaline, or near a neutral pH of seven. Most crops are partial to a slightly acidic to neutral soil pH of between six and seven. If your soil is more acidic or alkaline than this, there are a few things you can do. First of all, your soil pH doesn’t have to be perfect to grow crops. See how crops perform if your results come back slightly higher or lower than ideal! It may be just right. If your test is particularly slanted, you may also consider growing crops that prefer acidic or alkaline soil. If one section of your garden is particularly acidic, that is a great location for your blueberry bushes! 

If you decide to adjust your soil pH, you’ll want to plan ahead. Changing the pH can take time, so we recommend starting this process in the late summer or early fall with the hopes that you’ve reached your desired results by the springtime. The process of changing the pH of your soil is that of manually mixing in lime to increase alkalinity or sulfur to increase acidity (bring the pH up or down, respectively). These amendments are not water-soluble and must be mixed into the soil by hand or with a tiller to a depth of six to ten inches. This process can take weeks or months. When looking to change soil pH by a point or more, we recommend planning for even more time. This may require a year or more for a dramatic change. The amount of amendment required will depend on the amount of land you’re looking to adjust as well as your soil type. Take care to do your research so that you don’t waste your time or money! 

Recognizing Nutrient Deficiencies

Nutrient deficiencies can often be recognized by poor plant growth or slowed maturation, but discovering these deficiencies in a soil test can mean that you’ll be saving your future harvest the hassle! Here are some common deficiencies to watch out for. 

Macronutrients

There are several macronutrients in the soil but these are the major players. You’ll find them represented on fertilizers with the letters N (Nitrogen), P (Phosphorus), and K (Potassium), and their aligning numbers 5-5-5 or 10-10-10 or otherwise in that order. If you are deficient in one you may look for a fertilizer that is high in one but lower in the others. For a nitrogen deficiency, blood meal (12-0-0) is a great tool because it is high in nitrogen and has none of the other two. 

Nitrogen

A nitrogen deficiency often shows up as a pretty uniform yellowing of the older, more mature leaves. Typically the lower leaves. Nitrogen supports foliage production and is essential for many leafy green crops but also heavy feeders like tomatoes and corn. Too much nitrogen can result in a lot of lush foliage but no fruit or flower production. 

Phosphorus

A phosphorus deficiency often presents as weak and stunted plants that are slow to mature. Leaves can present as dark green or even purple. This can occur as frosts come in as well so this is especially important to watch out for in warmer weather. 

Potassium

Potassium deficiencies can mean limited production of fruits and flowers and can later result in burnt-looking leaves and browning tips.

Micronutrients

Micronutrients can be treated with specialized amendments just as macronutrients are! 

Boron

A boron deficiency often presents as chlorotic leaves and the main growing point dying back. Leaves can become misshapen and curled and plants may be stunted overall. 

Copper

Copper deficiency looks very similar to boron deficiency. These plants can be highly susceptible to diseases and fungal spread. 

Zinc

Zinc deficiency will often present as yellow to white striping on leaves and stems. 

Using Results to Improve Soil

Once you have your results, it’s time to put them into action. A soil test from the state may have some recommendations including lime applications or otherwise. This makes it easy as you’ll know exactly what to do next. 

But if your results don’t come with detailed recommendations, you’ve still got work to do! If there are signs of nutrient deficiencies of any kind, a hefty application of compost is always a good failsafe. If there are specific nutrients that need attention, there are amendments that can be added to the soil to improve the availability. Blood meal, as previously recommended, is great for boosting nitrogen. Fish Bone Meal is a great source of phosphorus and calcium. Kelp Meal is a great source of potassium. These amendments can be applied to and mixed into the soil at the rates recommended on the box. 

It’s best to apply organic matter or other non-water soluble amendments in the fall. This gives them enough time to decompose and become available for spring planting without leaching out of the soil. 

DIY Testing vs Professional Soil Testing

DIY test results range from fairly accurate and reliable to somewhat telling and vague. However, if your goal is just to gain a better understanding of your soil or check in on it each year, the DIY options of observations and kitchen counter tests should do you well. Using these tools, you can track soil health, makeup, and pH. If you are facing ongoing problems with no apparent solution; this is when we recommend getting a professional soil test done. However, our recommendation still stands to get a soil test done through the extension agency every three to five years. Home tests are a great starting point, but don’t hesitate to use the resource that is a professional soil test! 

Building a Routine for Monitoring and Preserving Soil Health

Monitoring and preserving your soil health will naturally become a regular part of your garden maintenance overtime. Each time you’re out weeding, simply take a moment to assess the visual features of your soil. Count how many earthworms you come across. Keep an eye on what’s performing well and what can be improved.

Soon enough, you’ll be testing new gardens before ever planting - saving you time and money. You’ll be able to track how soil changes over time and see that the effort you’re putting into maintaining your soil health is making a difference! 

FAQ

How often should you test garden soil?

Always be visually assessing your soil health and perhaps do some at-home tests once per year, but you only need to get a professional soil test done every three to five years unless you’re facing ongoing issues in the garden.

What is the easiest way to test soil pH at home?

We recommend using an at-home soil pH kit or doing the DIY test recommended above! 

What does soil pH mean for plant growth?

Most plants will grow best in slightly acidic soil between a pH level of six and seven. Other plants prefer more acidic soil or otherwise. PH affects plant nutrient uptake so if the soil isn’t a fitting pH level then the plant will struggle to get the food it needs. 

How deep should you take a soil sample?

Your soil sample should be six inches deep. 

Can you test soil nutrients at home?

There are at-home soil test kits that are affordable and can give you a general idea of your soil nutrient availability. For more detailed information, you’ll need to get a professional soil test. 

What are the signs of unhealthy garden soil?

Some common signs of unhealthy garden soil are severely compacted soil, a lack of presence of live organisms like earthworms, plants having trouble maturing, and water struggling to drain. 

Should soil be tested before planting vegetables?

Soil testing should be one of the first steps when establishing a garden so that you don’t waste time planting a garden that doesn’t have what it needs to thrive. However, it is not necessary to test your soil every single year ahead of planting vegetables.

When is the best time of year to test garden soil?

The best time of year to test your soil is in the fall. This gives you enough time before the spring growing season to amend as needed before planting.

Ready to get growing? Check out Sow True Seed’s range of soil amendments and testing supplies available and shipped right to your door!

 

	Article Written by: Hannah Gibbons
	About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has over a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.