As of July 1, 2005, Spectrum Analytic began reporting P, K, Ca, and Mg results as unadjusted Mehlich 3 (M3) values in parts per million (ppm). Prior to this date, samples were extracted with the Mehlich 3 solution, and the results mathematically converted to their equivalents in the older tests of Bray P1 for soil P, and 1Normal ammonium acetate (1NAoAc) for K, Ca, and Mg.
The table below shows the correlation formula we used to convert M3-ppm to the lbs/a values.
|Table 1: Correlation Formulas|
|M3-P||(Mehlich-3 ppm x 0.7) x 2||Bray P1 in lbs/a|
|M3-K||(Mehlich-3 ppm x 0.84) x 2||1NAoAc K in lbs/a|
|M3-Ca||(Mehlich-3 ppm x 0.75) x 2||1NAoAc Ca in lbs/a|
|M3-Mg||(Mehlich-3 ppm x 0.88) x 2||1NAoAc Mg in lbs/a|
For a complete explanation, see the original announcement of the change in Spectrum Analytic Reporting Conversions