Agriculture Reference
In-Depth Information
How to Take a Soil Sample for a Lab
Farmers will separately test different parts of their field, but this gets too costly for most
home gardeners, so you need only do one test, but you do want to combine at least three
samples from different parts of your garden. If you're primarily interested in growing food,
take three or more samples from your vegetable gardens and combine them. Skip the areas
in your yard that have obviously different soil conditions, or test them separately.
Most labs suggest your shovel should go down 6 or so inches to get a soil sample. Mar-
ket gardeners looking for a complete analysis often go down as far as 3-4 feet, being care-
ful to take different samples perhaps every 12 inches in depth, in order to evaluate what's
going on in the various subsoil layers.
Home gardeners will want to get soil from the surface down to at least 6 inches. The
easiest way to do this is to dig a hole first and then you can use your shovel to take a nice
vertical slice of soil from the side of that hole that will include all depths. What I mean is,
you don't want all of the sample to come from 6 inches down, and you don't want it all to
come from near the surface. You want soil right from the surface, excluding coarse mulch
but including any soil crust, down to your testing depth.
When you're taking these samples, be sure to keep everything very clean. The shovel
should not be rusty. The pail needs to be sparkling clean and cannot previously have con-
tained fertilizers. After the samples have been thoroughly combined in a pail, usually 2
cups are placed in a new, clean bag or container to be shipped to the lab. Some labs are
happy with 1 cup. Most labs don't care if the sample is wet or dry.
The results are only as accurate as the sample you send, so be sure to combine samples
from several different places in the garden, to the correct depth. Don't include much organ-
ic debris, and keep the whole process uncontaminated. Sample from the exact same spots
each year. Mark them in your journal or with scarecrows, birdhouses or pet rocks on site.
