Nutrient Deficiency Symptom Guide

Identify nutrient deficiencies by visual symptoms. The classic mobility-based diagnosis: where on the plant matters as much as what it looks like.

Diagnose by symptoms

Where on plant? — Select location — Lower / older leaves Upper / new growth Middle leaves / both Whole plant Roots / stem

Primary color change? — Select — Yellow (uniform) Yellow with green veins (interveinal) Brown / burnt tips or edges Purple stems / leaf undersides Red / purple leaves Dark blue-green White / pale spots Dark / dead spots Curling / cupping Distorted / twisted growth

Other indicator? — Optional — Stunted growth overall Floppy / weak stems Brittle leaves Tip die-back / hooking Blossom-end rot on fruit Poor flowering / fruiting

All deficiencies, by mobility

Mobility = whether the plant can move the nutrient from old leaves to new growth when the supply runs short. Mobile nutrients (N, P, K, Mg) get pulled out of older leaves first, so deficiencies show on lower / older leaves. Immobile nutrients (Ca, Fe, Mn, Zn, Cu, B) stay where they were placed, so deficiencies show on new / upper growth.

Mobile nutrients (deficiency on lower leaves first)

Nutrient	Symptom	Distinguishing feature
Nitrogen (N)	Lower leaves uniformly yellow, then drop. Plant pale and stunted.	Veins yellow too (no contrast). Whole-plant pale green to yellow.
Phosphorus (P)	Lower leaves dark blue-green to purple, especially on undersides and stems. Stunted growth.	Purple stems and leaf undersides; not yellow. Often cold-related (P uptake fails at low root temp).
Potassium (K)	Lower leaves yellow at edges; tip burn; brown necrotic edges. Dead spots between veins later.	Edge / margin burn rather than uniform yellow. Floppy plants.
Magnesium (Mg)	Interveinal yellowing on lower leaves — green veins, yellow between. Edges curl.	Classic interveinal pattern. Often confused with iron (Fe) — but Mg is on lower leaves; Fe on upper.

Immobile nutrients (deficiency on new / upper growth first)

Nutrient	Symptom	Distinguishing feature
Calcium (Ca)	New growth distorted, twisted, hooked tips. Brown spots on new leaves. Blossom-end rot on tomato/pepper.	New growth is the giveaway. Often a transpiration / VPD problem rather than solution-Ca shortage.
Sulfur (S)	Upper leaves uniform yellow. Looks like N deficiency but on upper leaves.	Upper-leaf location distinguishes from N (lower) and Mg (interveinal lower).
Iron (Fe)	Interveinal yellowing on UPPER / new leaves. Veins stay green; tissue between turns yellow.	Upper-leaf interveinal pattern. Often pH-lockout (high pH locks Fe). Root zone above 6.5 = Fe drops.
Manganese (Mn)	Interveinal yellowing on upper leaves with darker veins than Fe; small dead spots eventually.	Veins remain darker green than Fe deficiency; finer interveinal pattern.
Zinc (Zn)	New growth small, distorted; "rosetting" of new leaves. Yellow stripes.	Tight clustering of new leaves; smaller-than-normal new growth.
Copper (Cu)	New leaves dark blue-green, wilted. Tips die back.	Dark coloration with wilt. Rare in cultivation; usually a pH lockout or ultra-low source.
Boron (B)	New growth thick, brittle, distorted. Tips die back; "stuck" growing tips. Hollow stems.	Distorted thick new growth + brittle texture. Often confused with Ca.
Molybdenum (Mo)	Marginal yellowing on older leaves first; upper leaves cup; rare in cultivation.	Most plants need very little; rare deficiency outside acidic soils.

Beneficial elements (not strictly deficient, but helpful)

Element	Effect of low supply	Notes
Silicon (Si)	Weaker cell walls; more pest susceptibility; less heat / drought tolerance	Not technically essential but supplementing improves stress resistance and yield. Used in serious cannabis + greenhouse.
Cobalt (Co)	Reduced N-fixation in legumes	Trace; rarely deficient in normal soils
Selenium (Se)	Lower antioxidant capacity in tissue	Trace; some health/quality applications

Common confusions

Looks like	Actually probably	How to distinguish
Mg deficiency (interveinal yellow)	Iron deficiency	Where on plant? Mg = lower leaves. Fe = upper / new leaves.
Calcium deficiency (twisted new leaves)	Boron deficiency	B = thicker / more brittle. Ca = thinner, hooked, often blossom-end rot on fruit.
N deficiency (yellow lower leaves)	Sulfur deficiency	N = lower leaves yellow. S = upper / whole-plant yellow.
Nutrient deficiency in general	pH lockout	Solution may have plenty; uptake fails at wrong pH. Test substrate pH FIRST.
Deficiency-looking symptoms	Nutrient TOXICITY	Overfeed produces tip burn, dark green, leaf curl. Test runoff EC.
Yellowing	Light burn	Light burn typically affects only top leaves nearest light; bleached/white not yellow.
Yellowing	Root rot	Check roots: brown, slimy = Pythium; healthy white roots rule out root issues.

Diagnostic protocol

1. Confirm pH first. Most "deficiencies" are pH lockouts. Test substrate pH (slurry test) and runoff pH. Target 5.8-6.5 for hydroponic / coco; 6.0-7.0 for soil.
2. Test runoff EC. If runoff EC is much higher than feed EC, you have salt buildup — flush or reduce feed.
3. Sample tissue. A $30-50 lab test is the only definitive diagnosis. Mail a representative sample of recently-affected leaves (not the worst, not the healthiest) to a lab like Logan Labs or Spectrum Analytic.
4. Check for cultural issues. Heat, light burn, water schedule, root health — all can mimic deficiencies.
5. Apply targeted correction. Foliar application gives fast feedback (3-7 days); root-zone correction is more durable.

Free under CC BY 4.0. Cite as "OAT Deficiency Symptom Guide (openagriculturetechnology.com)". Symptoms synthesized from peer-reviewed agronomy literature, university extension publications, and Reams / Albrecht-school references.