Nutrient testing can provide you with lots of important information on the health and fertility of your soil, and the key to accurate results is to submit good samples. Taking a soil sample correctly will give you the best information about your garden. So, what are the requirements for soil sample moisture?
Soil does not need to be completely dry for nutrient testing. You should always check the guidelines your local laboratory provides and follow their specifications. If your soil needs to be dry, you should leave it to dry in a thin layer.
This article will discuss how to prepare your soil samples for nutrient testing, including how to dry your soil if necessary. Then you have a brief overview of how to conduct nutrient testing.
Preparing Soil Samples for Nutrient Testing
Most nutrient testing does not require much special preparation of your soil samples. Nutrient testing conducted in a local laboratory will collect your samples at their location or by mail.
Soil does not usually need to be dry to send out for testing. However, you should not send very wet soil. If you can squeeze water out of your soil, it is too wet. Try not to collect your soil samples directly after rainfall to avoid overly saturated soil. On a dry day, your soil should be fine to collect.
Most at-home nutrient tests require you to mix your soil sample in water. For ease, you should collect the soil samples in jars. This way, you can add the water directly to your sample. Follow the instructions on your testing kit for the correct water-to-soil ratio.
How To Dry Soil Samples
Occasionally, some laboratories will ask that you dry out your soil samples before sending them in for testing. Drying out your soil is simple and only has two steps.
- Spread your soil in a thin layer on unbleached white paper. The thinner you spread your soil, the faster it will dry. Clean printer paper is the best option to keep your soil on because it will not contaminate your soil. Newspaper contains ink and chemicals that can spoil your sample.
- Allow the soil to sit for 24 hours. Drying soil takes time. Placing the soil sample in an area with direct sunlight will help to speed up the drying process. If your soil is not spread out thinly enough, it may take up to 48 hours to dry completely.
Make sure to wash your hands or wear gloves when handling the soil sample. If the soil becomes contaminated, your results will not be accurate. Additionally, do not dry your soil outside on humid days. Even if it isn’t raining, the water content in the air will slow the soil’s drying.
How To Test Soil Quality
Testing soil quality isn’t as difficult as it may seem. The following steps offer a guide on how to do it.
Obtain the Necessary Tools
Thankfully, taking soil samples doesn’t require any fancy equipment. You’ll need the following:
- Two digging tools (Shovels, Spades, or Soil Probes).
- Ruler or tape measure.
- Plastic bags or jars (to put your samples in).
- Gloves.
Before you begin, you should ensure that your tools are cleaned properly. Dirt from another area, fertilizer, chemicals, and rust will contaminate the samples you take, and the results of the tests may be inaccurate. Clean gloves and tools will keep your samples usable.
Having two separate digging tools is the best option to avoid the contamination of your soil samples. If you only have one available, you must clean it thoroughly between steps.
Choose Several Places To Take Samples
To get an accurate representation of the soil in your garden, you should take samples from several different areas. Many factors can cause the nutrient levels to differ within your garden. A few areas that you should sample separately are:
- Raised garden beds.
- Areas with full shade and full sun.
- Different elevations.
- Areas that have been amended.
- Locations of plants that require different levels of nutrients.
You can also take several samples from the same area and combine them into one sample to represent the entirety of a similar area.
Dig a Hole 4-8 Inches (10-20 cm) Deep
For each sample area, you will need to dig a hole between 4 and 8 inches deep (10 and 20 cm). Dig down at an angle, creating a wide ice cream cone shape in the soil.
Make sure not to cut corners when it comes to digging your hole. If the hole is too shallow, it will contain more fertilizer and pieces of debris because it is closer to the surface.
Plants absorb nutrients from their roots. Therefore, the most important area of the soil is the depth that the roots will be. You should keep to the 4-inch (10-cm) mark for root vegetables and plants with shallow roots. Conversely, if you have a large plant with deeper roots, aim for a depth of 8 inches (20 cm).
After digging the hole, switch out your tools or clean the ones you used to dig the hole. The tools you just used have come in contact with grass, debris, and sometimes mulch or fertilizer. You need to ensure these materials do not make it into your sample, or it will become contaminated.
Take a Cross Section From the Hole
Your soil sample should come from the bottom of the hole you dug. If you have a tool different from the one you used to dig the hole, switch them out. If not, make sure to clean off your spade or shovel thoroughly. This will prevent sample contamination and ensure more accurate results.
Your sample should contain roughly a cup of soil. Think of a tennis ball or apple to visualize the amount you need.
The soil sample needs to be free of foreign objects, including:
- fertilizer
- grass
- mulch
- rocks
- roots
- sticks
- straw
- worms
Take Several Different Samples
The more soil samples you take, the more information you can gather on the nutrients in your soil.
It’s fine to combine samples from the same area. For example, if you take two samples from the same raised bed, you can mix them together. Then, use just one cup of the combined samples.
Distinct areas should have their own soil samples. Keep samples separate for areas more likely to have different levels of nutrients. This could include:
- Separate garden beds.
- Shaded vs. full-sun areas.
- Areas with different soil textures (For more information on soil textures, take a look at this article: Do All Soils Have the Same Texture?
- Areas of distinct elevation.
Add Detailed Labels to Each Sample
It is essential that you label your soil samples carefully. The nutrient levels may vary in different areas, so you need to know where each sample came from.
If you are sending your soil samples to a laboratory for testing, follow their instructions for what information to include in each sample.
Some laboratories have analysts who can provide specific recommendations for improving your soil. Providing as much detail as possible will allow them to provide more in-depth information and recommendations tailored to your garden. Include the type of plant or grass that you have recently grown in the area and what you plan to sow there in the future.
Perform Nutrient Testing
You have two options for soil testing, at-home or laboratory testing. Often your local government and nearby universities will offer testing services, sometimes free of charge.
There are many different types of home testing kits available. This video from the experts at Home Depot demonstrates the use of a standard soil testing kit:
If you choose testing at a local laboratory, follow their instructions to mail in or drop off your soil samples.
Home kits are often inexpensive and provide a good overview of your soil. They are also very quick, giving you results in hours. However, it does not offer the same level of accuracy as a laboratory test, and laboratories may even provide recommendations based on your results.
Conclusion
You do not need to dry out your soil before nutrient testing. If you are testing your soil at home, you will often need to mix your sample with water so the moisture in your sample does not matter.
If you are using a local laboratory, often through a local government or university, they will provide instructions for how to prepare your sample. Although this sample should not be wet (dripping water when squeezed), you rarely need to dry it yourself unless you collected your sample after rainfall.
