Let’s talk about a super important garden chore… soil testing. I hate to call it a chore because it’s so much more than just a task that needs to be completed every once in a while. Soil tests are a super helpful tool for investigating problems you see in your plants’ health as well as a way to get ahead of problems before they even begin. 

collage of two photos depicting diy and lab soil testing

It can seem daunting or like a hassle, but it’s pretty easy once you know how to get started. So, that’s what we’re talking about today! Read on to learn how and why to start testing your garden soil this season. You’ll find solutions to your garden woes and unlock a whole new level in your garden this year with the information a soil test will provide!

Why Soil Testing Is Important

Think of your soil as the bank where all the nutrients your plants need are stored. Throughout the growing season, your garden plants will need to withdraw nutrients to create strong root systems, lush foliage, beautiful blooms, and delicious food. If there are insufficient nutrients in your soil, you’ll start to see deficiencies in your plants. This can look like yellowing leaves, wilted greenery, stunted plant growth, or a lack of blooms. 

Testing your garden soil is like getting a statement from this nutrient bank- it provides all kinds of helpful information about the state of your garden below the surface. Here are some reasons you may want to consider testing your soil:

  • Troubleshooting: maybe you see some of these deficiencies appearing… testing your soil can give you answers as to what’s going on below the surface
  • Preventing nutrient deficiencies: it’s always best to get ahead of problems. If you test the soil before planting, you can set your plants up for success.
  • Plant-specific needs: Some plants do best with a higher or lower PH than others, and some need more or less of a specific nutrient. Testing your soil will allow you to tailor your soil to your plants’ needs.
  • Minimize fertilizer use: If you know what your soil needs, you can avoid overdoing it with unnecessary fertilizers. This is good for the environment and your garden budget.

Understanding Soil pH and Nutrient Levels

As I mentioned above, a soil test is almost like getting a bank statement from the nutrient bank in your garden. On that statement, you’ll get several indicators of soil health and conditions. Here’s a quick summary of what you might need to interpret.

collecting garden soil for a soil test

PH Levels

Any basic soil test will tell you the PH, or the acidity level, of your soil. PH ranges on a scale from 1 to 10. The lower the number, the more acidic. Generally, garden soil hovers around (?), but some plants like a higher or lower number- that’s when you may want to pay special attention to the PH level.

Nutrient Levels

A basic soil test focuses on three nutrients- Nitrogen (N), Phosphorus (P), and potassium (K). Here’s a quick summary of their roles in your garden’s health (source):

  • Nitrogen (N):
    • Promotes growth and green coloration in plants through the creation of proteins
    • Essential for photosynthesis and overall plant vigor
  • Phosphorus (P):
    • Supports the development of roots, flowers, seeds, and fruits.
    • Helps the plant to use and store energy
  • Potassium (K):
    • Enhances overall plant health, helping with water and nutrient uptake 
    • Plays a key role in protecting the plant against stressors such as disease, cold, or lack of water

When to Test Your Soil

The factors discussed above could create a reason to test your soil at any point in the year. However, there are certain times when it just makes sense. 

  • When you first start your garden
  • At the beginning of the growing season
  • At the end of the growing season
  • When problems arise 

Choosing a Soil Testing Method: DIY vs Lab Tests

At-home soil tests have their perks. They save time, are cheap, and are generally pretty easy to find (I always find them at Home Depot and Lowe’s). However, they no doubt have their drawbacks as well. The instructions seem straightforward, but completing the steps is often more of a hassle than expected. Half the time, the results are difficult if not impossible to interpret.

soil test kit on a wooden table

A professional lab test has its pros and cons, too. By far the best thing about using a professional lab test is that you know it will be accurate. After all, they are the professionals! What’s more, they then take those super accurate results to provide you with the next steps- details on how to fix or improve your garden soil. With DIY tests, you’ll find yourself reading through the instructions and searching the internet for what to do with your results. However, professional soil tests do require more time to complete, making them a bit less convenient.

When to use a DIY Soil Test Kit:

  • Routine Maintenance: when you don’t have any specific problems and want to check on things below the soil surface.
  • Immediate Results: Need answers now? DIY testing can do that for you.
  • Learning and Education: it’s worthwhile to do a DIY test at least once for the fun science project!

Opt for Lab Testing When:

  • Problem-Solving: When facing persistent issues such as poor plant growth, disease, or nutrient deficiencies that haven’t been resolved through general maintenance.
  • Baseline Testing: If you’re starting a new garden or working with a new plot of land, a lab test can provide a detailed baseline soil analysis to guide your initial amendments.

Soil Testing with a DIY Kit

Any test kit you purchase should provide instructions on how to do this, so don’t worry, there will be guidance! For a general idea, these are the steps to test your garden soil yourself:

  • Collect a soil sample: dig about 6 inches deep and collect a cup of soil including a mix of soil from the top to bottom of the hole.
  • Prepare the sample: details here will depend on the type of soil test you use.
  • Conduct the test according to the kit’s instructions.
  • Interpret results according to the kit’s instructions.
  • Amend soil accordingly.
preparing a soil sample for soil testing

How to have your soil tested professionally

Once again, any lab service will provide instructions on how to send in your soil sample for testing. But so you know what to expect, here’s how you’ll go about having your soil lab tested:

  • Find a lab to test your soil: Check your local university extension office, and call around to check pricing- some are much cheaper than others! Click here is a list of cooperative extension offices by state courtesy of Almanac.
  • Collect a soil sample: Follow the same or similar steps to testing with a soil test kit. The lab may ask you to collect soil from various parts of your garden for a complete picture of your soil’s health.
  • Send in the sample: the lab should provide detailed instructions on how to send your sample in for testing.
  • Review results.
  • Amend soil accordingly: here’s where professional testing is very helpful- they will let you know exactly what your next steps are to fix or improve your soil for your gardening needs.
soil being tested in a lab
Photo source: Texas A&M

Amending Based on Soil Testing Results

Once you get your soil test results back, it’s time to do something with the results! You’ll probably need to head to the garden center to pick up some fertilizer and soil amendments. Here’s a quick guide to the types of organic fertilizers you may need to address basic soil nutrient concerns. Remember, there are many secondary nutrients and minerals to consider as well.

Organic Fertilizers for Soil Nutrient Deficiencies

Deficiency TypeFertilizers/Amendments to Fix It
Nitrogen (N)Blood meal, fish emulsion, cottonseed meal, composted manure. *you can also use nitrogen-fixing plants like peas and beans to add nitrogen to the soil
Phosphorus (P)Bone meal, rock phosphate, composted manure, bat guano. 
Potassium (K)Greensand, kelp meal, wood ash (caution: raises soil pH), composted manure. 

Check out this article by Garden Design for more guidance on fertilizing various plants. And remember, there are also lots of valuable nutrients to be found in simple kitchen waste! Check out our post on organic fertilizers you can make for some examples.

How to raise or lower soil PH

pH IssueAmendments to Fix It
Too Acidic (Increase pH)Organic: Hardwood ash, crushed limestone (calcitic lime), oyster shell lime. 
Too Alkaline (Decrease pH)Organic: Sulfur, sphagnum peat moss, pine needles, composted leaves. 

General Advice Beyond Soil Testing

Garden soil will almost always need more nitrogen added. This is the most used nutrient by plants and it dissipates quickly by evaporation and getting rinsed away. So in general, it’s a good idea to fertilize with nitrogen. Some plants, however, do not do as well with high levels of nitrogen and require a bit of caution. 

It’s seldom a bad idea to add a bit of all-purpose fertilizer at the time of planting- don’t overthink it.

Monitoring and Maintaining Soil Health

Though soil tests and fertilizers are all wonderful tools to have at our disposal in the garden, there are plenty of ways to keep soil health in check so that you can avoid having to test and amend soil, to begin with. 

Mulch your Garden

Mulch creates a protective layer over your soil. This helps maintain soil moisture to keep all those good nutrients in place (and helps to water less). Though you can buy mulch, there are lots of ways to mulch your garden on a budget using waste you’re likely to have on hand. Add raked leaves during your fall garden cleanup, or sticks and twigs as you clean up the yard.

Opt for a Homemade Weed Killer Alternative

It’s also always wise to avoid harsh chemicals like weed killers in your garden- these can negatively affect the organisms in your soil that help maintain balance and promote soil health. Stick to gentler, natural, homemade weed killer options and preventative measures instead.

Plant a Cover Crop

Cover crops are plants that help improve your soil. These are typically planted in the off-season or to give your garden a break. Different cover crops serve various purposes, so check out our guide to cover crops in the garden for details.

cover crop grown in a raised bed cut down for green mulch
Photo source: Joe Gardener

Start composting

Make your own soil amendment using simple kitchen waste; compost is a garden essential in my mind. You can never go wrong amending your soil with compost, and it’s super easy to get started. Check out our guide to composting methods to learn more, or find DIY compost bin ideas.

composting materials and finished compost

Ongoing monitoring

You certainly don’t need to test your soil multiple times throughout the growing season, but it’s wise to keep an eye on things so you will notice when things look off. See leaves yellowing, wilting, or shriveling? It might be worthwhile to test your soil again. The sooner you notice, the easier it will be to correct the issue.

The Final Step: Embrace Soil Testing for a Thriving Garden

By uncovering the secrets held in the soil beneath your feet, you’re not just troubleshooting or preventing issues; you’re setting the stage for a garden that’s more vibrant, fruitful, and resilient. Whether you opt for a DIY approach or seek the precision of professional testing, the insights you gain will empower you to make informed decisions, tailor your gardening practices to meet the exact needs of your plants, and ultimately, enjoy the rewards of a healthier garden. So, grab that soil sample, and let’s get to the root of what makes your garden grow! Next, check out our latest post exploring types of snake plants, learn how to harvest vegetables for the best flavor, or explore edible landscaping ideas.

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