The biological assay outlined as follows does not provide an exact measure of the amount of atrazine present in the soil, but it can show you whether sufficient atrazine remains to harm sensitive crops. The Soil Sample Get a representative sample of soil from the field suspected of having atrazine residue. Take samples from the top two to three inches in several locations. Atrazine residue often occurs in patches in a field. Sample enough places to avoid missing areas of high residue, such as turn-around areas, eroded knolls and terrace channels.
Plants growing in such areas frequently show the most injury.
You should take and analyze separately samples from areas where excessive residue is anticipated. Collect your soil sample from at least six places in each area sampled. Remember that the assay is only as reliable or representative as the sample you begin with. A total of 10 pounds of soil is required for each sample assayed. Assays should be run on the moist samples within two days after they are obtained from the field.