- Use leaf position to narrow plausible nutritional causes.
- Check measurement, recipe and root faults before supplementing.
- Collect useful records and follow a laboratory sampling protocol.
01 / Record which tissue changed first
Start with plant age and leaf position. Some nutrients can be moved from older tissue to new growth when supply becomes limiting, so symptoms can appear first on older leaves. Less mobile nutrients can show problems near growing points. UF/IFAS explains why magnesium and calcium often produce different symptom locations.
Record the first affected leaves, the distribution across the crop and the timing relative to a top-up, new batch, transplant or equipment fault. Photograph whole plants and close details. A nutrient chart provides candidates; it cannot distinguish every disease, pest, environmental injury or combination of shortages.
Reading: Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida (HS964) ↗
02 / Use this chart as a shortlist
These simplified patterns are not a diagnostic key or a dosing chart. They vary with crop, severity and concurrent problems. A whole-crop pattern can arise from shared conditions, while a local patch may reflect delivery or root differences.
| Candidate | Often noticed first | Useful clue; not proof |
|---|---|---|
| Nitrogen | Older leaves | Broad yellowing and reduced growth |
| Magnesium | Older leaves | Yellowing between greener veins |
| Potassium | Older leaves | Damaged or yellowing margins; salt injury can resemble this |
| Phosphorus | Older tissue / overall growth | Slow growth and sometimes purpling; temperature also matters |
| Iron | Young leaves | Yellowing between veins; pH can restrict availability |
| Sulfur | Young tissue | General yellowing that can resemble other disorders |
| Calcium | Growing points / developing tissues | Distortion or localized tissue death; delivery can be limiting |
| Manganese, zinc and other trace elements | Often young tissue, depending on element | Overlapping patterns require stronger evidence before treatment |
Reading: Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida (HS964) ↗ · Identifying Nutrient Deficiencies of Greenhouse and Indoor Grown Crops ↗
03 / Inspect the system before buying a supplement
Purdue identifies pH, root disease, low root-zone temperature, irrigation problems and fertilizer delivery faults among causes of deficiency symptoms. An element can be absent, present at the wrong proportion, or present but poorly absorbed. Do not assume one of those causes is the usual explanation without evidence from this crop.
Calibrate and read pH and EC; compare with the chosen crop program. Check actual delivery, roots, solution level and recent temperature extremes. EC summarizes conductivity from dissolved ions; an acceptable reading does not prove that nitrogen, calcium, iron and every other nutrient are correctly balanced.
Excess fertilizer can injure margins and roots, so a symptom that resembles potassium deficiency does not justify adding potassium. Similarly, pale young leaves do not automatically justify iron. Check whether a recipe, environment or uptake fault better explains the evidence.
Reading: Identifying Nutrient Deficiencies of Greenhouse and Indoor Grown Crops ↗ · Electrical Conductivity and pH Guide for Hydroponics ↗ · Hydroponic Nutrient Solutions (G6984) ↗
04 / Reconstruct the batch from quantities
Use the fertilizer label and weighed quantities, not a recalled scoop count. Confirm the final mixed volume and every component of a multi-part program. Keep concentrated incompatible parts separate as the manufacturer instructs. Document source-water contributions in the same elemental units as the recipe.
For an illustrative program intended to supply 120 mg/L nitrogen, putting the amount intended for 40 L into 60 L gives 120 × 40 ÷ 60 = 80 mg/L before source-water contribution and other changes. That establishes a dilution error. It does not prove the observed leaf symptom has only one cause.
The site’s mixing calculator accounts for N, P, K, Ca and Mg. Sulfur and micronutrients are outside its readout. Do not treat a five-element total as a certificate that the complete formulation meets the crop requirement.
- List each product, its exact analysis, batch mass and final solution volume.
- Compare the result with the selected manufacturer program and crop stage.
- Check whether water-analysis units require conversion before inclusion.
- Resolve a documented mixing error using the complete program and an appropriate replacement or adjustment plan.
- Record the corrected batch and assess new growth; investigate any continuing symptoms.
05 / Use the laboratory before a trace-element experiment
Contact the laboratory before collecting tissue or solution. Explain the crop, age, growing method, symptoms and recent treatments, and ask which leaves, sample quantity, container and shipping method it requires. Follow that laboratory’s washing instructions; an unsuitable cleaning step can change the result.
UF/IFAS describes tissue testing as a complement to visual assessment. Interpretation depends on the sampled plant part and stage. A leaf concentration should be compared with an applicable reference, not a generic internet ppm table. Tissue and solution results answer different questions and may be useful together.
Do not add boron, copper or other micronutrients from a symptom photograph. Keep the current evidence and get crop-specific interpretation of an identified shortage, excess or uptake problem. Severe wilting or failing roots also require prompt attention while analytical results are pending.
Reading: Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida (HS964) ↗
06 / Close the record with evidence
Separate observations, test results and the working explanation. For example: older leaves yellowed; batch records showed a dilution error; a correctly prepared batch was introduced; subsequent leaves were assessed after a documented interval. That record is more useful than labeling every yellow leaf as nitrogen deficiency.
If several conditions were corrected at once, say so. Recovery supports the management decision but does not isolate a single cause. Preserve photographs and results for the next crop and seek help when the original explanation does not fit the response.
FIELD QUESTIONEC is in range, but young leaves are pale between veins. Is the next action an iron dose?
No. Iron availability is one candidate. Verify pH and calibration, roots, recipe and individual nutrient supply; use crop-specific tissue or solution analysis when the cause remains unclear. EC alone cannot settle the question.
Parts & buying criteria
Build your own parts & cost worksheet →
Showing aerated deep water culture. Quantities describe the teaching model. Specify real working volume, support, fittings and instruments for your installation.
01Nutrient reservoir1 · illustrated quantity+
Stores the measured nutrient solution beneath or beside the growing area.
Inspect: Compare the surface with the diffuser and the lower roots; freeboard is deliberate. There is no pump intake in this single-vessel example.
Maintain: Record level before refilling, keep light out and verify temperature, EC and pH.
Opaque, cleanable, intended-use container with volume marks and service access.
Check size, materials and operating conditions with your chosen supplier before ordering.02Lid & root support1 · illustrated quantity+
Holds the plant above the chamber or reservoir without pinching its crown.
Inspect: Separate the cover and inspect the basket or collar opening.
Maintain: Check fit as plants grow and keep unused openings covered.
Rigid compatible support with removable, correctly fitted baskets or collars.
Check size, materials and operating conditions with your chosen supplier before ordering.03Air pump & diffuser1 · illustrated quantity+
Delivers air below the water surface in this aerated DWC example.
Inspect: Trace the thin line from the dry pump to the diffuser. Bubbles are illustrative.
Maintain: Check actual delivery and dissolved oxygen; preserve backup air and prevent back-siphoning.
Rated output at the installed depth and diffuser resistance; accessible replaceable parts. Power it through ground-fault protection (GFCI/RCD) and keep the pump and its plug above the water line.
Check size, materials and operating conditions with your chosen supplier before ordering.Evidence beside the lesson.
Source checks: September 2026. The geometry, inspection exercises and worksheets are original teaching material. The named organizations have not endorsed or reviewed this site.
Published recipe rates and planning ranges retain their source context. Calculator equations are accounting tools; they do not predict uptake, yield, toxicity or safe stocking. Model dimensions, water speeds, roots and fish counts are illustrative. Verify species, crop, source water and product labels for a real system.
- University of Florida IFAS ExtensionPlant Tissue Analysis and Interpretation for Vegetable Crops in Florida (HS964) ↗
Nutrient mobility, visual symptom limitations and tissue sampling and interpretation.
- Purdue University, K. NemaliIdentifying Nutrient Deficiencies of Greenhouse and Indoor Grown Crops ↗
Symptom location and nutritional, root-zone and environmental causes. Does not validate diagnosis from a photograph.
- Oklahoma State University ExtensionElectrical Conductivity and pH Guide for Hydroponics ↗
Water analysis, salinity, pH and monitoring.
- University of Missouri ExtensionHydroponic Nutrient Solutions (G6984) ↗
Solution preparation, elemental nutrition and measurement.
The next useful connections.
Nutrient mixing: from grams to elemental ppm
Scale two documented fertilizer examples, read the bag analysis and calculate what actually enters the final solution.
Interactive tool · 6 min + guided practice →Nutrients & mixingReservoir management and solution replacement
Use a water-and-nutrient ledger to distinguish top-ups, rebalancing and a complete batch change.
Interactive tool · 6 min + guided practice →Nutrients & mixingWhy pH drifts up in hydroponics: measure the cause before adding acid
Separate source-water alkalinity, nutrient uptake, mixing changes and meter error with a repeatable measurement log.
6 min + guided practice →Nutrients & mixingReading fertilizer labels: N-P-K, the analysis panel and nitrogen form
A soluble fertilizer label states nitrogen, phosphate and potash by mass, then an analysis panel and a derived-from list; read all three before a gram goes into a recirculating tank.
Interactive tool · 7 min + guided practice →