Soil Collection

Abstract

Soils are discontinuous heterogeneous environments that contain large numbers of diverse microbial populations including bacteria, fungi, algae, protozoa, and viruses. These populations vary with depth and soil type. In general, surface soil horizons have more organisms than subsurface horizons. Thus populations are influenced by many factors such as soil depth, soil type, and natural microsite variations. Natural microsite variations can allow very different microorganisms to coexist side by side in the same region of soil. Because of the great variability in soil microorganisms, it is always necessary to consider more than one sample during a microbial analysis of a site. Otherwise, it is not possible to get the complete picture of a selected soil. Thus, the sampling strategy is influenced by the goal of the analyses, the resources available, the site characteristics, and the history of the soil. The most accurate approach is multiple and individual analysis (MIA), which means taking many samples within a given site and performing a separate analysis of each sample. Another approach is composite analysis. An advantages of this approach is reducing time and effort by combining the multiple samples taken to form a composite sample; this in turn limits the number of analyses that must be performed. Thus composite sampling is better than the MIA approach. Another approach often used is to sample a site sequentially over time from a small defined location to determine effects on microbes. Such effects change over time; thus the effects are temporal.