YielixFertigation Injector & Stock Tank Calculator
Calculate the dry soluble product mass for one final stock tank when you know a selected-nutrient ppm target, product analysis and injector ratio. It is for checking a labeled N, P₂O₅ or K₂O concentration at an irrigation outlet—not for choosing a crop fertilizer rate. Record a measured source-water contribution when available, or mark it unknown so the displayed outlet concentration remains clearly conditional.
What the 1:R Injector Ratio Means
This page defines 1:R as one volume of final, mixed stock becoming R volumes of resulting dilute irrigation solution. Thus 1:100 means one litre of final stock corresponds to 100 L of solution after injection, not one litre stock plus 100 L water. Confirm that definition against the injector manual and measure the installed machine: nominal settings, pressure and wear can change actual draw. The Irrigation Runtime Calculator helps plan how much water a zone receives, but it does not verify nutrient concentration.
Use a measured source-water contribution of the same selected label nutrient, including an explicit measured zero. “Unknown” is different: the calculation conditionally assumes zero and does not claim that a water test found zero. A measured outlet EC can be a useful field record, but EC is not converted into a universal nutrient ppm and never changes this mass-balance answer.
Label Analysis Is Not a Field NPK Plan
The product percentage is the labeled mass percentage of the one nutrient selected above: N, P₂O₅ or K₂O. P₂O₅ and K₂O are oxide labels, not elemental P and K. A 20% N product has a nutrient fraction of 0.20; it does not mean that every N-P-K number belongs in this one-nutrient equation.
Use the NPK Calculator for field or greenhouse planning across N-P₂O₅-K₂O targets and several products. Use the Fertilizer Rate Converter when a local recommendation needs an explicit mass-per-area conversion. Neither substitutes for a water test, a product label or injector calibration.
Mixing, Compatibility and Verification
The equation assumes every gram dissolves, the tank is mixed to a uniform final volume and the stock stays uniform while it is injected. It cannot establish solubility, tank-mix compatibility, precipitation risk, water-quality effects or a safe mixing order. Follow the product label and supplier guidance; jar-test only where that guidance permits it, and never treat this calculation as label authorization.
Calibrate with actual tank draw and irrigation volume, then sample or test where your program requires it. Match all tests to the selected nutrient basis and keep EC as a separate verification observation. For hydraulic context, the Pump Sizing Calculator and Drip Emitter Spacing Calculator address flow and layout, not fertilizer compatibility or crop nutrition.
Inputs Explained
- Selected nutrient and target ppm
- Choose N, P₂O₅ or K₂O and enter a finite target at or above 0 ppm (mg/L) on that same label basis. It is your own target, not a crop recommendation.
- Source-water contribution
- Select measured and enter a finite nonnegative ppm, including explicit 0, or select unknown. If it is unknown, the estimate assumes 0 ppm and labels the outlet result as an assumption; confirm it with a water analysis.
- Product name and selected analysis
- Enter a label name if helpful, then the finite selected-nutrient percentage by product weight: more than 0% and no more than 100%. The name never supplies or changes analysis.
- Final stock volume
- Enter a finite volume greater than 0 after product is dissolved and the tank is topped up: L or US liquid gallons. This is not merely the water volume before adding dry product.
- Injector 1:R denominator
- Enter finite R of at least 1. Here 1:R means stock : resulting dilute solution; verify your equipment uses that definition before mixing.
- Measured outlet EC (optional)
- If recorded, EC must be finite and nonnegative in mS/cm. It is a separate verification record—no universal EC-to-ppm conversion is used.
How This Calculator Works
Formula
Added ppm = max(0, target ppm − background ppm)- When background is unknown, zero is an explicit conditional assumption. If background exceeds target, fertilizer cannot lower it, so added ppm is zero.
Nutrient fraction = selected label analysis (%) ÷ 100- Use one label basis: N, P₂O₅ or K₂O. P₂O₅ and K₂O are not silently converted to elemental P or K.
Product g = added ppm × R × final stock L ÷ (1000 × nutrient fraction)- R is resulting dilute-solution volume per stock volume under this page’s 1:R definition.
Stock g/L = product g ÷ stock L; actual ppm = background ppm + product g × 1000 × fraction ÷ (R × stock L)- The inverse mass balance checks the calculated dose; outlet ppm stays conditional when background is unknown.
Source
- Fertilizer Injectors: Selection, Maintenance and Calibration (opens in a new tab), University of Georgia Extension — Use this to confirm how the installed injector defines its ratio and to plan calibration and maintenance.
- Care and Calibration of Injector Pumps (opens in a new tab), University of Maryland Extension — Supports measuring actual injector performance instead of relying only on a nominal ratio.
- The Basics of Fertilizer Calculations for Greenhouse Crops (opens in a new tab), Virginia Tech / Virginia Cooperative Extension — Explains fertilizer-label analysis and concentration calculations for greenhouse crops.
Assumptions
- Dry product fully dissolves and the final stock tank is uniformly mixed; final stock volume is the volume after topping up.
- The installed injector uses stock : resulting dilute solution = 1:R and actually operates at the entered, calibrated ratio.
- Source-water nutrient contribution is additive and uses the same selected label basis. Unknown contribution is not measured zero.
- The selected label analysis is representative of the product. No crop rate, nutrient uptake, pH, alkalinity, EC conversion or water chemistry adjustment is inferred.
- Inputs accept finite nonnegative ppm/EC, analysis over 0% through 100%, final stock volume over 0 and R at least 1. Unit switching changes physical volume/mass display only.
Worked Example
H03 worked example: 150 ppm N target, measured 0 ppm N background, 20% N dry soluble product, 10 L final stock and a 1:100 injector.
- 1. Determine N to add
max(0, 150 − 0) = 150 ppm N. The 20% N label gives a nutrient fraction of 20 ÷ 100 = 0.20.
- 2. Calculate dry product mass
150 × 100 × 10 ÷ (1000 × 0.20) = 750 g product.
- 3. Read stock concentration and outlet check
750 ÷ 10 = 75 g/L final stock. At 1:100, product dosing is 0.75 g/L resulting solution and the inverse equation gives 150 ppm N.
- 4. Verify before applying
Dissolve and top up only as the product label allows, calibrate actual stock draw, and compare the outlet with your water/nutrient monitoring plan. EC alone does not confirm 150 ppm N.
Under these stated assumptions, mix 750 g of the 20% N product into 10 L final stock for a 1:100 injector to calculate 150 ppm N at the outlet.
How to Interpret Your Results
| Condition | What It Means |
|---|---|
| Calculated actual outlet equals target | The selected-nutrient mass balance closes under the entered analysis, final volume, ratio and source-water assumption. It is not proof of dissolution, compatibility or injector accuracy. |
| Unknown source-water contribution | The displayed actual outlet is conditional on zero background. Obtain a water analysis on the selected nutrient basis before treating it as a measured total. |
| Background is above target | The calculated product mass is zero and actual outlet remains at the background concentration. Fertilizer addition cannot reduce concentration. |
| Higher R or final stock volume | With target and analysis unchanged, required product mass increases proportionally. Recalculate after every physical change rather than scaling a rounded display value. |
Limitations and Cautions
- This calculator does not choose a crop fertilizer rate, substitute for soil or water testing, or prepare a field N-P₂O₅-K₂O plan. It only converts your chosen one-nutrient ppm target into stock-product mass.
- Solubility, compatibility, precipitation, label restrictions, handling requirements, water chemistry, backflow protection and safe mixing order are outside the equation. Follow the product label and local requirements.
- Injector performance can differ from a nominal setting with pressure, flow, wear and maintenance. Calibrate actual draw and verify the delivered solution; do not use the calculated ppm as a laboratory result.
- The answer is for a final stock tank volume and a uniform solution. It does not calculate irrigation scheduling, zone uniformity, crop response, runoff or environmental compliance.
Common Mistakes to Avoid
Treating 1:100 as one part stock plus 100 parts water
This page uses one final stock volume in 100 resulting dilute-solution volumes. Confirm the injector’s own convention; do not rely on the punctuation alone.
Entering a complete N-P-K grade for one analysis field
Enter only the percentage corresponding to selected N, P₂O₅ or K₂O. Use a complete nutrient-planning tool separately.
Calling unknown water contribution zero
Choose measured only after a value, including explicit zero, is known. Unknown output is conditional and should prompt water testing.
Using EC as a direct proof of selected-nutrient ppm
EC responds to all dissolved ions and water conditions. Keep it as a separate verification record; do not use a universal EC-to-ppm factor.
References
- Fertilizer Injectors: Selection, Maintenance and Calibration (opens in a new tab), University of Georgia Extension — Use this to confirm how the installed injector defines its ratio and to plan calibration and maintenance.
- Care and Calibration of Injector Pumps (opens in a new tab), University of Maryland Extension — Supports measuring actual injector performance instead of relying only on a nominal ratio.
- The Basics of Fertilizer Calculations for Greenhouse Crops (opens in a new tab), Virginia Tech / Virginia Cooperative Extension — Explains fertilizer-label analysis and concentration calculations for greenhouse crops.
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