Usually, one area is compared to another. Take a set of three samples from the kelp meal area and three from the ammonium nitrate treated area before applying any treatment to determine whether the two areas were started out the same to begin. Both areas should be the same before starting. Also realize that extrapolating results to a different soil or vegetation may not be appropriate. Organisms change with distance from the stem of a plant, or when different plant species are present.
Bare soil has different organisms than areas with litter.
Areas under old logs will have different organisms than areas under new logs. Samples taken without regard to this variability will mask the effects of a management practice from background variation. All samples should be taken from similar areas within one area, e.g., all taken 3 inches from the stem of plants, or from under a log, or at the same soil depth, to reduce variation and increase detection of management effects. For example, if you want to know if your tomato patch has a typical foodweb, randomly sample throughout the tomato area. On the other hand, if you want to know whether soil next to tomatoes contains normal numbers of organisms, sample an inch or two from the tomato stems, but not in the walkways between rows of tomato plants.