A comparison of soil scientist estimations and laboratory determinations of some Arizona soil properties

Samples of representative Arizona soils were sent to 36 soil scientists who were asked to estimate the sand, silt, and clay percentage; organic matter percentage; cation exchange capacity; carbonate content; and wilting point of each soil. These estimates were then correlated with laboratory analyses of these soils. The mean correlation coefficients for the individual estimations were highest for sand and clay (.88 and .86) and lowest for percent carbonates and cation exchange capacity (.56 and .65). Linear regression equation slopes and intercepts for all estimates differ from 1 and 0, respectively, indicating the absolute agreements were in error. Coefficients of variation show how estimates varied among soil scientists. Information about the soil scientists' degree of confidence, their estimations, and their performance also are presented.