How To Take A Soil Sample
1 spade or shovel, 1 trowel or small scoop, and 1 bucket (holds about 5 gallons or 19 liters)
(All of the above equipment should be clean, not made of brass, bronze or soft metal, or galvanized, and free of rust and flaking paint)
1 plastic bag for each sample (one quart or one liter in size is ideal)
When to take a soil sample?
Soil sampling should be done a few months before you intend to plant your crops. This gives you enough time to adjust your soil’s pH, in necessary according to your Grow Your Soil recommendation, prior to planting.
How many samples do you need to collect?
If you are testing your garden soil, typically one sample is sufficient, unless your garden is quite variable in topography or has sections that have been managed quite differently. For example, if one section of your garden has received fertilizers for years, and another section has received no fertilizers, you will want to make two separate samples for your garden.
An overview of what you will do to create one sample:
For each sample you need, you will dig 10 to 20 holes, take a sample from each hole, mix all the samples together, and take one final sample from the mixture, as described in more detail below. Avoid touching the soil that you will use as a sample.
Selecting where to dig the holes:
Be sure the site of the hole is fairly representative of the area (and is not a place where chemicals were dumped, or water puddles, or is unique in some way to the rest of the area). Each sample will be taken by first cleaning off any surface debris and then digging a V-shaped hole that is approximately 1 foot (30 cm) deep.
Sampling from the hole:
Using a trowel or scoop, scrape away a little from one of the sides of the V-shaped hole. Then, use the scoop, starting at the bottom of the hole and moving upward, to gather soil from the scraped side of the hole. Gather the equivalent of about one handful of soil with the scoop from the side and place it in the bucket.
Sampling the rest of the holes:
Then, repeat steps 4 to 6 for 10 to 20 other locations in the area you are sampling. Put all of the samples you collect into the same bucket.
Creating the final sample:
Thoroughly mix the soil samples in the bucket, using your spade or trowel (not your hands). Be sure that the soil at the bottom of the bucket is mixed with the soil at the top of the bucket. Then, after very thorough mixing, take small samples from different areas on the surface of the bucket and add them to the plastic bag until there is about 1 to 1.5 pounds (0.5 to 0.7 kg) of soil in the bag. You don’t need to dry the sample.
Recommended: Determine texture of the soil you have collected.
Note: To determine the texture, using this video as a guide, any type of water can be used and a spatula is not essential.
Optional: you could make a back-up sample in case anything happens to the original sample.
Seal the bag well, so that there is no chance of the bag opening during transit. You may wish to double-bag your sample, and seal each bag well.
Label the bag very clearly and legibly, with black or blue permanent marker, as specified by the lab to which you are sending the sample.
Collect any other samples you need by repeating steps 3 through 7. Then, after all of the samples are collected, well-sealed, and uniquely labeled, complete the lab’s submission form. Be sure to complete all required information in a very clear, legible and permanent manner.
Place the labeled sample(s), submission form, and payment method into a sturdy corrugated cardboard box. Do not put the submission form inside the plastic sample bags. Seal the box carefully and ship it to the lab.