SOIL ANALYSIS - WESTERN STATES PROFICIENCY TESTING PROGRAM FOR 1996

Under the auspices of the Western States Proficiency Testing Program s oil samples were analyzed for thirty-five constituents and plant sampl es were analyzed for fifteen constituents. Statistical evaluations usi ng robust statistical estimation techniques were provided to individua l laboratory participants. Analysis of samples previously analyzed in other programs indicated that the accuracy of several soil analyses (p H, electrical conductivity, NO3-N, extractable K and organic matter) a re very reliable. Results of soil phosphorus independent of method and soil organic matter by loss-on-ignition were generally unreliable. Pr ecision, measured by a replicated sample, indicated that a majority of laboratory participants are capable of reproducing analytical values within 10% through a twelve month period.