When it comes to sampling soil, there are a wide variety of reasons and conditions in which you might want to sample and test it. Unfortunately, the soil does not always present itself in what is perhaps the ideal condition for sampling and testing. For example, can you sample and test frozen soil?
You can sample and test frozen soil, but the sample you collect must be soil with no ice chunks. The ground, similar to water, freezes at a temperature of 32 °F (0 °C). When this happens, if the soil that is being sampled is watery, chunks of ice can appear. Allow the soil to thaw before testing.
Sampling soil can be important in many different climates and for many different reasons. Let’s take a deeper look at why soil is sampled, what it is tested for, how soil sampling and testing work, and how soil can be sampled even when frozen.
Collecting Frozen Samples for Testing
While soil sampling and testing are often easiest when soil is thawed, it is still possible to sample and test soil when frozen.
Using the soil probe, take a number of samples across the site you hope to sample. Since the ground is frozen, it may be difficult to actually get the soil probe in the ground. If the probe is strong enough, you may be able to use a hammer to force the probe into the ground.
Once the soil samples have been taken, bring them to a warm climate so the soil can thaw and undergo testing. While some labs and companies test frozen samples, home gardening kits will not produce accurate results with a frozen sample.
After the soil has had a chance to thaw, mix the numerous samples and undergo the same process used for regular soil sampling.
In some cases, scientists conduct soil samples in extreme climates such as the arctic and antarctic, as well as on mountain tops. In these samples, scientists determine if they are analyzing soil or ice, as this creates two different results. For example, most samples taken in the arctic circle are actually ice samples, not soil samples.
In most cases, however, the testing and sampling of frozen soil are not necessary for backyard gardeners. It is much easier to wait until the ground has thawed to take a sample. In most cases, people who take frozen soil samples can not take any action on the results of the tests until after the soil thaws.
Additional Considerations for Testing Frozen Soil
While it normally isn’t practical or necessary for home gardeners to test their soil at any point when it is frozen, for those who do decide to test their frozen soil, there are a few important points to consider.
Let’s take a deeper look at how you should take and test a frozen soil sample, the benefits of doing so, and the drawbacks that can come with the process.
Should you decide to sample and test frozen soil, the steps to do so are virtually the same as testing an unfrozen sample. The major difference, however, is the fact that you need to let the soil thaw after collecting the sample. Bring the soil into an area warmer than 32 °F (0 °C) for about one hour to let it thaw. Then, follow the steps on the test kit to test the sample.
While testing frozen soil can be difficult, there’s certainly some benefits to testing the frozen soil. One major benefit is the fact that when sampling soil that is frozen, typically, there is less water that you need to contend with that might impact your sample. Additionally, you are less likely to have bacteria or insect life in the soil that might disrupt results.
The biggest issue that many encounter when testing frozen soil is the fact that it is incredibly difficult to actually collect the soil samples. Digging into the ground, either with a probe or with another device, is hard to do when the ground is frozen. This means getting a number of reliable samples is often hard to do – making it largely unfeasible.
Why Do People Sample Soil?
For most people, the importance of having good soil isn’t a thought that crosses our minds all that frequently. While we know that rich dirt is below everything we walk on and is needed to grow plants, that’s about as much interaction people have with the idea.
Yet, without high-quality soil, the world would cease to exist. About 80% of the world’s food comes from small farms, making them incredibly important to maintain our way of life.
Unfortunately, rich, fertile soil ideal for producing plants is not always available. In fact, the majority of the earth’s surface is not hospitable for growing different types of plants. There are many factors that go into plant life, including the acidity of the soil a plant grows in, the number of nutrients available in the soil, the amount of water or other moisture available, and more.
For this reason, scientists and farmers often sample soil to determine if it is acceptable for plant growth. If they find that the ground contains certain substances that are ideal for one plant species, farmers might decide to grow only that plant or treat the soil so that new nutrients and resources are available for other plants to grow.
In recent times, people have also sampled soil for specific chemicals and pollutants to see how damaged an area might be from human pollution. Infamously, after the Chernobyl nuclear accident in the then Soviet Union, scientists used soil sampling to determine how much radioactive material was in the ground and how much needed to be removed during the cleanup in order to prevent further environmental degradation.
Substances Tested for in Soil Testing
When it comes to soil testing, there are two general categories farmers and scientists like to test for: nutrients and pollutants. While each test varies depending on the exact characteristics of the sample, most samples test for one or the other.
Let’s take a deeper look at the actual substances being tested for in each of these tests.
Soil Tests for Nutrients
When testing for nutrients, most scientists look at nine major factors. These are the soil’s acidity, the soil’s salinity (the amount of salt in the soil), the number of nitrates available, and the levels of the elements key for plant nutrients, including phosphorus, potassium, calcium, magnesium, sodium, and sulfur. Some tests also look for zinc, iron, manganese, copper, and boron levels.
Soil Tests for Pollutants
Unlike tests for nutrients, most pollution soil tests do not include a standard barrage of chemicals and substances that need to be identified. With most pollutant tests, scientists specially treat the soil to look for certain substances they believe might be in the soil. This often includes tests for pesticides, antibiotics, petroleum products (i.e., gas, oil, mixed fuel, diesel, etc.), radon, asbestos, lead, and chromated copper arsenate.
Other tests also look for environmental issues more specific to direct human action. Soil radioactivity, the levels of PFAS chemicals, and the release of toxic waste are sometimes used for “forensic soil samples.” These are samples that may be taken to determine if a crime has occurred, like intentional pollution, negligence, or the release of chemicals and substances that are not permitted to be released. These types of tests typically occur in urban environments.
How a Soil Sample Test is Conducted
Now that we understand what exactly a soil sample is, why someone might test it, and what people look for in soil samples, you might be curious as to how these tests actually work.
Is there a certain sensor that determines what chemicals are present? Is there a particular fluid that is added to the soil to reveal what the soil contains?
To conduct a soil sample test, several soil samples are taken from around a site and mixed together to ensure a relatively representative sample of the soil on the site.
To gather these samples, a soil probe is stuck into the ground collecting about 6 to 8 inches (15.24 to 20.32 cm) of soil from the site. Generally, the more samples, the better, depending on the size of the field, but most people use 15 to 25 different samples.
After the soil is collected, it either immediately undergoes a test or is sent to a facility to perform an in-depth test. For most backyard gardeners, you can purchase a small soil sampling kit at the local store, but for industrial farmers or corporations, the soil is sent to a lab that performs a more specific test.
Once ready to test, typically, a small amount of soil is combined with deionized water and a special liquid that will make the water change color depending on the concentration of the chemical present. Similar to a test you might use on a pool, it can be somewhat difficult to read exactly how much of the substance you are testing for is present, but after some time, a clear reading will be produced, allowing you to determine what is in the soil sample.
When it comes to sampling soil, people sample and test soil for several different substances with very different intentions. It is possible to sample and test frozen soil, but it generally is not necessary for individuals using a home testing kit.
Additionally, while possible, sampling frozen soil is often harder than sampling thawed soil. Collecting frozen samples with a probe can be incredibly difficult, and, aside from research, not many actionable steps can be taken from the results of a frozen soil sample. It is possible to sample and test frozen soil, but most people have no need to.
If you’d like to learn more about improving soil quality in your garden, you could check this article out: How to Improve Soil Quality (The Ultimate Guide)