FOREST SOIL SAMPLING EFFICIENCY - MATCHING LABORATORY ANALYSES AND FIELD SAMPLING PROCEDURES

Soil characteristics can be extremely variable, both spatially and temporally, and the cost of sampling to achieve high levels of precision may be prohibitive. Researchers are often faced with the need to obtain the best possible precision within a fixed budget. We present methods of determining the optimal number of field composite samples, the number of field samples per composite, and the number of laboratory analyses per composite. Example problems illustrate methods of obtaining both a desired precision at a minimum cost and the greatest possible precision at a given cost. Calculations to compare and select among alternative laboratory procedures are also illustrated. Often, less precise but inexpensive laboratory procedures may result in greater overall precision than highly precise but expensive procedures.