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Vertical Farm Nutrient Rate Estimator

This estimator calculates the mass of a nutrient product needed to raise a defined nutrient concentration in a vertical farm's solution reservoir. The model uses reservoir volume, the difference between target and current concentration, and the product's active nutrient percentage.

It is useful for planning a correction after testing or for checking a dosing worksheet, but it does not determine the appropriate nutrient target for a crop. Real fertigation programs may be specified by electrical conductivity, multi-part stock solutions, elemental ratios, or injector settings, so use the calculator only when a single nutrient concentration and product analysis are the intended basis.

Inputs

gal
mg/L
mg/L
%
Result
—
g
Concentration increase—
Active nutrient required—
Solution volume—

1. Enter solution volume
Enter the water or nutrient-solution volume that will actually receive the dose, in U.S. gallons.

2. Enter the target concentration
Use the desired concentration in mg/L on the same nutrient basis as your test result.

3. Enter the current concentration
Enter the measured concentration before dosing. A value at or above the target produces a zero addition.

4. Enter product analysis
Enter the percentage of the product that is the active nutrient being calculated.

5. Review the dose
Use the product mass as a calculation check and follow your normal staged dosing, mixing, and verification procedure.

Product required (g) = Volume (gal) × 3.78541 × max(Target − Current, 0) ÷ 1000 ÷ (Active % ÷ 100)

Where:

  • Nutrient solution volume: entered in gal
  • Target nutrient concentration: entered in mg/L
  • Current nutrient concentration: entered in mg/L
  • Product active nutrient: entered in %

Assumptions: inputs describe the same system, batch, or planning period, and units are used exactly as labeled. The model is intentionally simple and does not add unentered losses, fees, or biological effects.

What the result means

The result is the approximate product mass needed to supply the entered concentration increase to the stated solution volume.

The calculation assumes the stated active percentage refers to the same nutrient basis as the target and current measurements.

Given:

  • Solution volume = 4,200 gal
  • Target = 175 mg/L
  • Current = 125 mg/L
  • Product active nutrient = 18%

Calculation:
4,200 × 3.78541 × 50 ÷ 1000 ÷ 0.18 = 4,416.31 g

Result:
Nutrient product required ≈ 4,416.31 g

Interpretation:
The concentration gap corresponds to about 4.42 kg of an 18% active product, subject to the farm’s normal dosing and mixing procedure.

Why is the dose zero when current concentration exceeds the target?

The model only calculates an addition needed to raise concentration. It does not calculate dilution or removal when the current level is already above target.

Can I use ppm instead of mg/L?

For dilute water solutions, ppm is often treated approximately as mg/L, but the units and test basis should be checked. Enter values on one consistent concentration basis.

What should I enter for active nutrient percentage?

Use the product analysis for the same nutrient represented by the concentration target. Do not substitute a different elemental or compound basis.

Does the result account for precipitation or biological uptake?

No. It assumes the added active nutrient disperses into the stated solution volume. Chemical reactions, plant uptake, filtration, and other losses are not modeled.

Should the full calculated amount be added at once?

The calculator only provides the arithmetic amount. Actual dosing should follow the operating procedure appropriate to the crop, water chemistry, organisms, and product, with mixing and re-testing as needed.