The Mobility Rule & Per-Nutrient Signatures
The one rule that tells you where to look — mobile nutrients fail bottom-up, immobile fail top-down — plus the full per-nutrient leaf signature table and the pH-lockout trap that fakes a deficiency.
Before color or pattern, ask where on the plant the symptom is. That single question splits the nutrient world in half, because of how the plant relocates nutrients under scarcity.
Mobile nutrients (N, P, K, Mg, Mo) can be pulled out of old leaves and relocated to new growth — so deficiency shows in the old/lower leaves first (bottom-up). Immobile nutrients (Ca, S, Fe, Mn, Zn, B, Cu) can't be relocated — so deficiency shows in the new/top growth first (top-down). Old-leaf problem → suspect a mobile nutrient. New-growth problem → suspect an immobile one. This rule alone eliminates half the candidates before you look at color.
The rest of this lesson is for members
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