Mixing Fertilizer Types / Brands

Nutrients
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1

Note to future self:

ALWAYS avoid mixing Cal-Mag with other fertilizers. Instead, mix it in a separate jug → Apply
Why? When Cal-Mag gets mixed with other fertilizers, it transforms (in a bad way). That’s because Cal-Mag contains chelated iron. Chelates can drop their metal ion (ligand exchange), and the freed ion can precipitate out with phosphate, carbonate, or sulfate.

RISK LIKELIHOOD: Very High
How likely is the nutrient to be displaced or to react?

RISK IMPACT: Very High
If chelated iron is displaced or reacts, how damaging will the result be?

After applying Cal-Mag to the plant,
THEN, adjust pH for a big jug of water that’s gonna be used to prepare each remaining fertilizer component

NEXT, mix each fertilizer using separate containers

THIRD, blend them in correct order → Apply

  • Start with the fertilizer containing the lowest concentration of chelated metals

  • End with the fertilizer containing the highest concentration of chelated metals vulnerable to transformation (being precipitated out)

3

Adjust pH after additives :green_heart::sign_of_the_horns:t2:

4

You’re right, @StonedCold13 . Thank you. Acidifying AFTER mixing H2O & Cal-Mag is optimal.

  • Start with plain water - don’t adjust pH, yet
  • Add Cal-Mag & mix thoroughly
  • Promptly adjust pH to 6.2-6.5 (growing in soil).

Explanation:
Water that’s alkaline (like mine is), usually contains high hydroxide (OH⁻). When Fe-EDTA is exposed to this OH⁻ for too long, that hydroxide can break the EDTA ligand. When that happens, the iron becomes insoluble to my plants. Fe(OH)₃ is that rusty, orange‑brown, insoluble iron that my plants can’t use.