- Calculate stock mass from final g/L and dilution.
- Separate calcium from incompatible concentrates.
- Verify real injector drawdown and output.
01 / A stock is concentrated inventory
A stock solution stores fertilizer at a higher concentration for later dilution. The injector ratio tells you how much stock enters the final solution, but manufacturers may express ratios differently. Establish whether 1:100 means one unit in 100 final units or one plus 100 water units. This chapter uses one unit of stock in 100 units of final solution.
At that definition, 1 L of stock contributes to 100 L of finished solution. To supply a product at 0.6 g/L final, a 100× stock contains 60 g/L of that product. Solubility and compatibility determine whether that concentration is practical; arithmetic alone does not prove it can be stored.
Reading: Nutrient Solution Formulation for Hydroponic Tomatoes in Florida (HS796) ↗
02 / Separate A and B
Calcium-containing fertilizer belongs apart from concentrated sulfate and phosphate. Use separate labelled stock tanks and dedicated measuring tools. A and B labels are not universal chemical identities; document their ingredients for your own system.
Never mix two concentrates together before dilution. Supply each into enough moving water according to the equipment instructions. Keep lids, pickup screens and service access usable, and keep concentrated fertilizer, especially calcium nitrate, away from acids, cleaners and organic material, and follow the product safety data sheets.
03 / Work backward from delivered concentration
Suppose the final recipe requires 0.6 g/L base, 0.375 g/L Epsom salt and 0.6 g/L calcium nitrate. With each stock stream metered at 1 L per 100 L final solution, a 10 L A stock would contain 600 g base plus 375 g Epsom; a separate 10 L B stock would contain 600 g calcium nitrate. This is a dilution exercise based on the 40 L recipe, not a manufacturer-approved stock solubility specification.
The injector’s final water volume includes all injected streams. Do not prepare 100 L of water and add 1 L A plus 1 L B while calling it 100 L final. Either calculate the actual 102 L concentration or adjust water to obtain the intended final 100 L.
- Write the final product rates in g/L and define the injector ratio explicitly.
- Multiply each final rate by the stock dilution factor, then by the stock volume. Check label solubility at the storage temperature.
- Prepare compatible stock groups separately, bringing each to its final stock volume. Record date, ingredients and concentration.
- Measure actual stock drawdown and collected final output during a timed test. Compare their ratio with the setting.
- Check the delivered solution against a manually mixed reference batch and verify EC/pH. Recheck after injector or pressure changes.
04 / Prevent silent dosing drift
Keep stock pickup lines submerged, check for precipitate and record tank consumption. If A is being consumed much faster than B while settings are nominally equal, investigate the injector before adjusting the crop.
A conductivity alarm can detect a large dosing failure but cannot prove balanced A/B delivery. Use separate consumption records and periodic analysis for a long-running installation. Label concentrate containers so a future operator can reproduce the recipe without relying on memory.
FIELD QUESTIONIs “100×” enough information to prepare a stock?
No. You need the final recipe, definition of the injector ratio, volume of each stock, chemical compatibility, solubility and actual injector delivery.
Parts & buying criteria
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Showing drip / dutch buckets. 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 pump intake or lower roots; freeboard is deliberate.
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.02Pump & supply1 · illustrated quantity+
Moves nutrient solution from the reservoir to the growing area.
Inspect: Trace installed lift and branching; the pump label does not prove delivered flow.
Maintain: Measure output after service and inspect intake, filter and minimum water level.
Pump curve matched to installed head, required pressure and service needs.
Check size, materials and operating conditions with your chosen supplier before ordering.03Dutch buckets3 illustrated · illustrated quantity+
Contain a large root-zone medium with a defined drainage outlet.
Inspect: Inspect the outlet height, any internal water reserve and the drain screen on each bucket.
Maintain: Verify each bucket drains freely after an event and inspect moisture at several depths in representative buckets.
Rigid, opaque, food-safe buckets with screened outlets on a supported gravity return.
Check size, materials and operating conditions with your chosen supplier before ordering.04Root-zone mediumFor illustrated containers · illustrated quantity+
Stores moisture and air around the roots in the illustrated containers.
Inspect: Compare the medium surface with irrigation and drainage.
Maintain: Inspect wetting at several depths; prevent fines from reaching drains and emitters.
Prepared, stable grade matched to the irrigation method and crop.
Check size, materials and operating conditions with your chosen supplier before ordering.05Drip emitters3 illustrated · illustrated quantity+
Distribute solution separately to each container.
Inspect: Trace the manifold and the small outlet above each plant position.
Maintain: Collect equal-time samples and compare output; flush the main line before installing emitters.
Emitter pressure requirements matched to pump and filter; flushable connections.
Check size, materials and operating conditions with your chosen supplier before ordering.06Gravity return1 · illustrated quantity+
Collects each bucket outlet into a supported return line to the reservoir.
Inspect: Follow each bucket outlet into the shared return and check the continuous fall to the reservoir.
Maintain: Test pump-off drain-back and keep roots and medium out of the outlet.
Accessible fittings and verified capacity under normal and fault conditions.
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 ExtensionNutrient Solution Formulation for Hydroponic Tomatoes in Florida (HS796) ↗
Elemental ppm by fruit-cluster stage in Florida greenhouse tomato production.
- University of Missouri ExtensionHydroponic Nutrient Solutions (G6984) ↗
Solution preparation, elemental nutrition and measurement.
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