Is it M3 or Bray?

With the transition of Indiana, Michigan and Ohio university fertilizer recommendations moving to Mehlich 3 (M3) data the question of, “How do you tell if the ALGL soil test results are in M3 or Bray-P/AA-K?” comes up often.

Internally we refer to the grouping of Bray-P, ammonium acetate (AA) K/Ca/Mg/S/Na, hydrochloric acid (HCl) Mn/Fe/Cu/Zn, and hot water (HW) B as NCR or North Central Region. From a soil testing perspective, the country is divided into regions based on the soil characteristics in that region. Researchers in those regions have identified the tests that are appropriate for the soils and climate of the region. While M3 it utilized by almost all regions of the country, the traditional methods of AA, HCl, and HW are also appropriate for most of the corn belt.

ALGL publishes over 50 different report formats to meet customer needs that vary in appearance. Reports that show M3 values will have “M3” in the column header for that nutrient. If “M3” is in not in the column header for that nutrient the value reflects NCR methods. This does not apply to pH or OM. The values displayed on the report are those used to calculate the CEC and cation saturation percentages.

When looking at electronic data files for uploading to software, this may not be as clear depending on the software used. Some uploads for software do not identify the units nor the method for each column of data. If unsure, your ALGL regional agronomist can help.