Roots should be placed in the same plastic bag as the soil and separated by the laboratory. Placing them in a separate bag, they are likely to dry out and be unuseable. Wrapping in wet paper towels encourages the growth of fungus prior to arrival at the laboratory. It is often more desirable to sample at the outer edge of an unhealthy area rather than at the center, because nematodes tend to migrate to healthier areas as roots deteriorate. Alternatively, the sample can be placed in a double plastic bag with a label written in pencil placed between the bags.
Laboratories typically process about half a quart or half a liter of soil.
Providing the extra soil will permit reprocessing if the sample is accidentally spilled or another calamity occurs. There is no one correct number of subsamples to take. Generally, the potential for maximizing the detecion of the number of species present increases as the number of subsamples increases. For a diagnostic sample, a useful rule of thumb would be to collect as many subsamples as can be taken in a half hour. The number of subsamples that can be taken in this time will vary depending on a number of factors including the sampling device used, depth of roots, soil texture, and soil moisture level.