Gardening experts everywhere recommend that you test your soil before doing anything else. If your garden is suffering, you are just starting out as a gardener, or you are a continuous fertiliser, I recommend this.
Knowing your soil’s nutrients and pH can help you troubleshoot and properly fertilize, which can have a big impact on your garden’s overall health and productivity. But how exactly do you test your soil?
Well, you probably shouldn’t – the pros should.
Store-bought kits are available everywhere, but the accuracy of these is questionable at best. Especially if the pH is only off by a certain amount in either direction, any change you make will do more harm than good. While kits are relatively inexpensive, and you can often get more than one use out of them, you’ll need to interpret the results and make a plan yourself.
However, more accurate results are guaranteed if you send your samples to a laboratory for professional analysis. Not to mention that you are usually given advice on fertilization and changes depending on the type of plants you plan to use.
Read on to learn how to test soil, how to get a sample for them, and what to do with the results.
Who Are the Pros?
The best way to have a professional analysis of your soil is to contact the local counseling office in your state or county.
If you don’t know what I’m talking about when I say “local branch”, you’re not alone. This is one of those often-cited, rarely explained, general recommendations.
In short, the USDA National Institute of Food and Agriculture (NIFA) supports an effort called the Cooperative Extension System (CES).
NIFA describes CES as “a national, non-credit educational network that serves the needs of the public by providing informal higher education and learning activities to farmers, ranchers, communities, youth and families across the country.”
Basically, your local extension is created for you. So use it!
For a small fee (usually between $5 and $25), your local counseling office will do a soil test for you.
In some areas, county offices may also provide services. For example, in Cincinnati, Ohio, the Hamilton County Soil and Water Conservation District provides soil testing services to its residents.
No matter which service you use, the procedure is very similar.
How To Test Soil Sample
A kit will be sent to you with instructions on how to obtain high quality samples. Usually it looks like this:
Step 1 – Create a Wedge
Use a trowel to form a V-shaped wedge in the soil about 2 inches wide and 6 inches deep.
Step 2 – Remove and Cut
Remove the wedge from the bottom and cut a piece two inches from the center of the sample.
Step 3 – Set Aside
Place the sample in a clean, non-metallic bucket or bowl of some sort.
Step 4 – Repeat
Depending on the size of the area you are sampling, repeat Steps 1 through 3 in 8 to 12 more spots. This will give you a more comprehensive picture of the area you’re testing.
Step 5 – Combine
Mix the samples together thoroughly and allow the mixture to dry completely.
Put the desired amount (usually less than a cup) into the designated container, most likely a plastic bag.
Step 6 – Document and Mail
Complete the required information forms (one should be included) and submit samples.
If you are sending multiple samples, be sure to note where each sample was collected.
Most of the action happens near the surface, so don’t worry about getting deeper samples.
Organic matter, nutrients, organisms, and plant roots are most concentrated in the top 4 to 6 inches of the soil.
Nor should you send samples every season. Every three to five years is enough. Stay in the same lab every time for the most consistent results.
Autumn is the best time to send samples, but early spring is also good. That way, any changes you make, like adding organic compost or lime to raise the pH, have time to take effect.
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Good to Know
Don’t assume the test will be all-encompassing.
In general, essential nutrients such as phosphorus, potassium, calcium and magnesium are tested along with pH and organic matter.
All plants use the macronutrients nitrogen (N), phosphorus (P), and potassium (K) in the highest amounts, which are nutrients found in commercial fertilizers.
However, nitrogen is usually not tested because it moves in and out of the soil easily and changes rapidly with each reading.
Providing adequate organic matter, crop rotation and the use of cover crops will help ensure that plants have adequate nitrogen levels.
Many tests will also give you an idea of the texture, recording the percentages of sand, silt and clay. This is great for drainage, hydration and air circulation.
The ideal fertile texture for planting recommended by gardening articles is composed of equal parts silt, sand and clay, making up 45% of the total volume.
Believe it or not, up to 50% of pores should be open. At any given point, half of the open pore space should be occupied by water and the other half by air.
Organic matter, which is nothing more than rotting branches, leaves, grass clippings, animal waste, etc., should usually be around 5% in a healthy garden.
Before you send out your samples, call your branch and talk to someone and ask what’s included in the standard test. If you have specific questions, you may need to make specific requests.
For example, if you want to test for heavy metals like lead, you may need to ask (and pay more), or even go through a private lab. However, if you plan to grow an edible garden, especially in urban areas, the extra cost and effort is usually worth it.
What to Do with the Results
Once you receive your test results, the information may be accompanied by recommendations on fertilization and changes, especially on nutrients and pH.
Remember that recommendations are different for different plants. Therefore, it is important to provide the lab with information about what you will be growing.
For example, lawns, vegetables, flowers, and shrubs have different general soil requirements.
I prefer to fertilize with organic compost. It’s as good as gold.
But newly added compost requires more processing by the organism before it can get its nutrients. So think of compost as a long-term slow-release fertilizer.
Add a few inches of fresh organic compost once or twice a year and the soil should be well nourished.
that’s right. The soil should be well nourished. It’s a self-contained ecosystem where bacteria, fungi and insects and many other organisms work together.
Most commercial fertilizers are designed for plants, not soil. They usually contain only man-made forms of nitrogen, phosphorus, and potassium, which are readily absorbed by plants but have little effect on underground life.
Overuse of synthetic fertilizers can even damage soil life in the long run. Some organisms prefer certain nutrients over others, so diversity can become an issue.
And, at least in the short term, chemical fertilizers are known to reduce nematode populations and destroy fungi.
They also ooze out of the garden quickly, which means you have to keep reapplying them throughout the growing season.
In this context, I recommend the use of short-term chemical fertilizers in cases of acute nutrient deficiencies. Test results and recommendations are especially useful for correcting nutritional imbalances.
A pH adjustment may also be recommended. Typically, this is accomplished by adding lime when conditions are too acidic and sulphur when conditions are too basic.
Most plants grow best in slightly acidic to slightly alkaline conditions. If the pH is below 5.5 or above 7.5, adding lime or sulphur may be recommended.
For general gardening, a pH of 6.0 to 7.0 is ideal. In this region, nutrients are readily available and underground life flourishes.
Build a Healthy Foundation
Understanding nutrients and pH, as well as texture and organic matter, makes it easier to maintain a healthy, thriving garden.
You’re also less likely to overfertilize, which can save you some money depending on how much fertilizer you use each year.
Once your plants are healthy and growing in the short term, put fertilizer aside and focus on nourishing the soil.
Healthy, diverse, nutrient-rich soil produces healthy, nutrient-rich plants.
Even if you don’t want to eat the plants you grow, they’ll be stronger and more resistant to pests and diseases when the soil is well established.
Add two inches of organic compost to your garden at a time in the spring and fall, just as you would with any other organic mulch. Worms and other organisms process it and convert it into nutrients usable by plants.
Planting cover crops like clover and winter rye is another great way to keep your soil healthy.
Often planted out of season between fallow fields or orchards, they prevent erosion and weeds and support underground life.
Maintain a healthy rotation schedule of annuals each season to further encourage variety and maintain nutritional balance. You should avoid tilling and compacting your garden as much as possible.
Consider plowing the soil before planting and you’ll be well on your way to a beautiful, productive and healthy garden. Have you tested your soil? What was your experience? Let Answer The Question know what you learned along the way in the comments section below!