An injector stock tank contains a stronger solution than the final irrigation stream. To calculate that stock, the target nutrient concentration, product analysis and injector ratio need to describe the same delivery basis.
Use Fertilizer Injector Stock Calculator when those values are known. In this worksheet, ratio means final solution volume divided by stock volume. A ratio of 100 therefore means one litre of stock serves 100 litres of final delivered solution, rather than one litre being added to 100 litres of water.
A thousand litre final batch
Suppose the target addition is 100 mg/L of one nutrient and the soluble product contains 20% of that nutrient. The required product concentration in the final stream is 0.5 g/L.
With an injector ratio of 100, stock product concentration is 50 g/L. A 10 litre stock tank therefore needs 500 g of product. Delivering 1,000 final litres draws 10 litres of stock and supplies 500 g of product across that batch.
| Quantity | Example result |
|---|---|
| Final product concentration | 0.5 g/L |
| Stock product concentration | 50 g/L |
| Product in 10 L stock tank | 500 g |
| Stock drawn for 1,000 L final batch | 10 L |
Stock tank size is separate from concentration
Changing the tank volume changes the product needed to prepare that tank and the final volume it can serve. It does not alter the required stock concentration for the same target, product and ratio.
If the final batch needs more stock than the entered tank contains, the calculator states that one tank is insufficient. It does not silently assume the injector can keep drawing after the prepared stock has been used.
The stock dilution relationship is discussed in Virginia Tech’s fertilizer calculation publication.
Calibration and solubility still need checking
Enter the actual calibrated ratio for the injector arrangement, not an unverified dial interpretation. The tool does not measure injector draw, evaluate product solubility at the required stock concentration or approve mixing incompatible products.
The target here is an added nutrient concentration. It is not a complete recipe, and other nutrients in the product still enter the final stream. Use Nutrient Solution PPM Calculator when you want to subtract a known background concentration for a directly prepared batch, and keep the target basis consistent.
Save the product analysis and ratio with the stock worksheet. A stock preparation label showing only 500 g would lose the tank volume and delivery assumptions that make that number useful.