Direct/Delayed Response Project: Interlaboratory Differences in the Northeastern Soil Survey Data

摘要

Soil samples collected during the Direct/Delayed Response Project (DDRP) northeastern soil survey were analyzed, using the procedures described in the analytical methods manual for the DDRP (Cappoet al, 1986), by four different laboratories. Inconsistencies in results were reported by the different laboratories regardless of use of standardized procedures. Audit samples Oa, A, Bs, Bw, and C Horizons were included in the survey. The audit sample data were used for an interlaboratory comparison to determine if there are significant differences in the audit sample values reported by the laboratories. The analysis compares the laboratories to each other rather than to a true audit value. Such analysis has been completed for each chemistry variable in the DDRP northeast soil chemistry database. Various graphics display the results. If the samples from each sampling class, region, and state were uniformly distributed across all the laboratories, the interlaboratory value differences would likely have little effect on analyses conclusions. However, this is not the case. The significant value differences among laboratories are not consistent across all audit horizons, which makes it even more difficult to assess their effect on data analyses.