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Mehlich 3 Evaluation

Mehlich 3 Evaluation. Robert O. Miller ALP Technical Director Colorado State University Fort Collins, CO. SERA-6 Meeting, Raleigh, NC, June 21, 2011. Miller, 2011. Observations.

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Mehlich 3 Evaluation

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  1. Mehlich 3 Evaluation Robert O. Miller ALP Technical Director Colorado State University Fort Collins, CO SERA-6 Meeting, Raleigh, NC, June 21, 2011 Miller, 2011

  2. Observations M3 Phosphorus observations across proficiency programs have shown consistent differences between ICP and SPEC P analysis methods on specific soils. Although a majority of soil testing labs utilize ICP for M3 P analysis, many use nutrient calibration models based on SPEC analysis. M3 SPEC – ICP differences have been report to be insignificant and a nonissue, however differences remain relevant. Miller, 2011

  3. M-3 Comparison Proficiency program M-3 P comparisons SPEC vs ICP Correlative soils properties with M-3 P Differences M-3 Solution Instrument Calibration, P and K Miller, 2011

  4. M3 P Spec and ICP Comparisons M3 P methods comparison of proficiency data (NAPT) have suggested method bias difference, however the database lacks intra-lab measurement error. M3 soil data from the ALP Program, with intra-lab error , provides conclusive evidence P analysis method differences, which are soil dependent. Of 70 ALP soils, 32 indicate a statistical significant difference between SPEC and ICP P values. M3 P methods significant different at the 0.05 level, three replications multiple labs Miller, 2011

  5. Mehlich 3 P Spec vs ICP 1:1 line y = 1.15x R2 = 0.957 70 Soils, Collected from Thirty States - ALP ALP Data base 2006-2011 Miller, 2011

  6. Mehlich 3 P Spec vs ICP Relative % Difference 70 Soils, Collected from Thirty States - ALP ALP Data base 2006-2011 Miller, 2011

  7. Mehlich 3 P Spec vs ICP Parse soil pH < 7.3 (0.01 M CaCl2), N = 50 1:1 line ALP Data base 2006-2011 Miller, 2011

  8. Mehlich 3 P Spec vs ICP Relative % Difference Reduced Data Set, pH < 7.3 (0.01 M CaCl2) 50 Soils, pH < 7.3 ALP Data base 2006-2011 Miller, 2011

  9. Mehlich 3 P Spec vs ICP Delta Correlation Reduced Data Set, pH < 7.3 (0.01 M CaCl2) 28 soils 1 Correlations, soil pH < 7.3, phosphorus methods removed. ALP Data base 2006-2011 Miller, 2011

  10. 460 Soils - MN Eliason, Lamb and Rehm, 2001

  11. M3 P Spec and ICP Comparisons Differences in M-3 between SPEC and ICP can be described as Non-Reactive Phosphorous(NRP). Large NRP differences primarily associated with M3 P levels less than 40 ppm. High NRP is identified with soils with low pH, high sand content and low silt contents. Maybe associated with aluminum. Soils with high NRP were collected from Oklahoma, Arkansas, Iowa, eastern Nebraska and eastern Illinois. No-Till soils greater difference. Miller, 2011

  12. Mehlich 3 Standard Solution Evaluation An evaluation of seven M3 solutions was conducted in 2010 of 24 labs. Seven bottles were prepared, #1- #5 from reagent solution standards, #6 - #7 of soil extracts. Reagent standard solutions balanced ionic strength. Laboratories analyzed for P, K, Ca, Mg, Na and Zn each in triplicate in ALP Cycle 12. 1 Submitted ALP Program Cycle 12. Bottles #6 and #7 soil extracts of ALP of SRS-0802 and SRS-0715. Miller, 2011

  13. Mehlich 3 P Calibration Evaluation ICP Labs 12, sorted by low standard Lab #12 has P precision issue across standards An evaluation of M3 3 solutions was conducted in ALP Cycle 12, 12 labs participating. Miller, 2011

  14. Mehlich 3 K Calibration Evaluation ICP Labs, 16, sorted by mid range standard Labs #15 and #16 have high bias issues, all standards An evaluation of M3 solutions was conducted in ALP cycle 12, 16 labs participating. Miller, 2011

  15. Mehlich 3 Phosphorus Calibration Evaluation A performance report for M3 analyses was provided to each ALP participating laboratory. ALP Data base 2006-2011 Miller, 2011

  16. Mehlich 3 ICP Phosphorus Evaluation Calibration Evaluation – 5 standards Ten of twelve reporting labs. Highlighted values indicate deviation from known calibration standards. ALP Data base 2006-2011 Miller, 2011

  17. Mehlich 3 Phosphorus Evaluation Soil extract comparison 1 Bottles #6 and #7 soil extracts of ALP soil SRS-0802 and SRS-0715. Mean values significant different at the 0.05 level based on twelve labs, triplicate. ALP Data base 2006-2011 Miller, 2011

  18. Summary NRP associated with soils with low pH, high sand content and low silt contents. Location specific. Impact on recommendations and P index tool (PLAT). Evaluation of M3 P calibration standards show that 4 of 12 of labs have P calibrations that deviate greater than 5% from the known calibration slope. M3 K show that 5 of 16 labs show K calibration deviations greater than 5% from the known calibration slope. Miller, 2011

  19. Future work ALP will include Mehlich 1 elemental standard calibration solutions for Cycle 16, for P, K, Ca, Mg, Mn, and Zn. Solutions to be analyzed in triplicate for the evaluation of bias and precision. Miller, 2011

  20. Thank you for your time and attention

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