Controlled-Environment Agriculture (CEA), Hydroponics & Venturi/Dosatron Fertigation
Hydroponic Fertigation Injector Stock Tank & ppm Formula
Calculate Dripper-Line Fertilizer Salt Concentration (mg/L), Concentrated Stock-Tank Salt Concentration (g/L), Total Dry Fertilizer Bag Charge (kg), and Cold-Water Solubility Utilization (%).
Weighing 150 mg/L of Calcium Nitrate salt instead of 150 ppm Elemental Nitrogen starves tomato crops by 84.5%!
Commercial greenhouse hydroponic recipes specify elemental nutrient targets in `ppm` (`mg/L` of pure Nitrogen `N`, Potassium `K`, or Calcium `Ca` at the dripper emitter), whereas fertilizer bags contain only a fraction `P_elem` (%) of that element (e.g. greenhouse-grade Calcium Nitrate `15.5-0-0` carries `15.5%` elemental `N` and `19.0%` `Ca`) AND proportional Dosatron/Venturi injectors dilute A/B stock barrels by Injector Ratio `R_inj` (`1:100` -> `R_inj = 100`, `1:200` -> `R_inj = 200`)! First divide Target Elemental `ppm` by Elemental Purity Fraction to get Dripper-Line Salt Concentration `C_line = ppm_target / (P_elem / 100)` (mg/L); next multiply by Injector Ratio `R_inj` and divide by `1,000` mg/g to obtain Stock-Tank Salt Concentration `C_stock = (C_line * R_inj) / 1,000` (g/L); finally multiply by Stock-Tank Volume `V_tank` (L) / `1,000` to weigh exact Dry Fertilizer Charge `M_bag` (kg)—checking that `C_stock` stays safely below cold-water salt solubility!
Verify on a 200 L Tank-A Calcium Nitrate Stock Recipe—Target_Dripper_Nitrogen = 150.0 ppm N (B2), Calcium_Nitrate_Elemental_N_Pct = 15.5% (B3 -> Dripper-Line Salt = `967.74` mg/L in E2), Proportional_Injector_Ratio `1:100` = 100 (B4 -> Stock Concentration = `96.77` g/L in E3), and Stock_Barrel_Volume = 200.0 L (B5): Weigh exactly `19.35` kg of Calcium Nitrate into Tank A (E4), utilizing `8.06%` of its `1,200` g/L cold-water solubility limit (E5)!
| CEA Fertigation Stock-Tank KPI (150 ppm N, 15.5% Ca(NO3)2, 1:100 Injector, 200 L) | Formula | Verified Output |
|---|---|---|
| Dripper-Line Salt Conc. (mg/L) | Target_Element_ppm / (Purity_Pct / 100) | 967.74 mg/L |
| Concentrated Stock Tank (g/L) | (Line_Salt_mg_L * Injector_Ratio) / 1000 | 96.77 g/L (193.55 g/L @ 1:200 injector) |
| Total Dry Salt Charge (kg) | (Stock_Conc_g_L * Tank_Vol_L) / 1000 | 19.35 kg (38.71 kg @ 1:200 injector) |
| Ca(NO3)2 Solubility Used (%) | (Stock_Conc_g_L / 1200) * 100 | 8.06% (16.13% @ 1:200 injector) |
Proportional Fertigation Injector Dilution & Elemental Salt Mass Formula
Validate `Target_ppm > 0`, `Elemental_Purity` in `(0%, 100%]`, `Injector_Ratio >= 1` (`1` = direct batch tank without injector; `50–500` = proportional injector), and `Stock_Tank_L > 0`!
=LET(pp_m, B2, pu_p, B3, ir_t, B4, vt_l, B5, IF(OR(pp_m <= 0, pu_p <= 0, pu_p > 100, ir_t < 1, vt_l <= 0), "Invalid Fertigation Input", LET(cl_m, pp_m / (pu_p / 100), cs_g, (cl_m * ir_t) / 1000, ROUND((cs_g / 1200) * 100, 2))))High-Ratio 1:200 Injector Upgrade Check (Set Injector Ratio R_inj = 200)
Dial the proportional injector from `1:100` (`0.5%` -> `1%`) to `1:200` (`0.5%` injection, set B4 = 200) so Tank A lasts twice as many irrigation cycles: Dripper-Line Salt E2 stays `967.74` mg/L (`150` ppm N), while Stock Concentration E3 doubles to `193.55` g/L, Bag Charge E4 doubles to `38.71` kg, and Solubility Used E5 reaches `16.13%`!
=IF(ISTEXT(E5), E5, LET(cl_m, B2 / (B3 / 100), cs_g, (cl_m * B4) / 1000, ROUND((cs_g * B5) / 1000, 2)))Try the example
Use the original values or change them to test your understanding.