Before planting: Collect soil from 8 to 12 locations in the area where you intend to plant. Samples should be taken about 6 to 8 inches deep. If the soil is dry, dig down to where there is some soil moisture to collect the samples, and do not include the dry soil. A small handful of soil from each location is adequate. Combine all the soil into a single plastic bag. The total volume of soil from the samples should be about 1 pint. Samples may be taken with a shovel, trowel, or other device. If using a shovel, you can put part of the soil from 8 to 12 shovels full into a bucket. Thoroughly mix the soil in the bucket, and then take out a pint to submit for analysis.

After planting: Often a nematode assay is needed to determine if nematodes are causing a plant to get sick. For this type of sample, both soil and roots are required. Dig soil and roots from underneath the canopy of the symptomatic plants. Soil should be collected from where most of the fibrous roots are. Usually six inches deep is sufficient. Collect roots that are less than 1/4 inch in diameter. If multiple plants are affected, collect some soil and roots from several plants. Place the soil and roots together in the same plastic bag. A minimum of 1 pint of soil and 1 to 2 cups of roots are required.