Calculator Inputs
Example Data Table
| Scenario | Inputs | Typical outcome |
|---|---|---|
| Fertigation mix | 100 ppm K, 20 L, potassium sulfate, 100% purity | Calculates grams of product and g/L strength |
| Small tank | 60 ppm K, 10 gal, potassium nitrate, 98% purity | Converts gallons to liters, adjusts for purity |
| Bed topdress | 12 g K2O per m2, 8 m2, potassium chloride, 2 splits | Gives total grams and per-application dose |
Examples are illustrative; confirm crop limits and label instructions.
Formula Used
- Solution dosing: Required K (mg) = Target ppm (mg/L) × Volume (L)
- Convert to grams: Required K (g) = Required K (mg) ÷ 1000
- K2O to K: K% = K2O% × 0.8301
- Fertilizer grams: Product (g) = Required K (g) ÷ (K fraction × Purity fraction)
- Soil dosing: Total K (g) = Rate (g per m2) × Area (m2), then convert if rate is K2O
- Safety factor: Final product = Product × (1 + Extra%)
How to Use This Calculator
- Select dosing mode for solution mixing or bed applications.
- Choose a fertilizer source, then override analysis if your label differs.
- Enter purity if your product is not fully active.
- For solutions, enter target ppm K and final volume.
- For soil, enter area, target rate, and split count.
- Press calculate to view results above, then export CSV or PDF.
Professional Notes
Potassium Dosing in Practical Garden Programs
1) Why potassium matters for yield quality
Potassium supports water balance, enzyme activity, and sugar transport that drives flowering and fruit fill. In many crops, improved potassium management is linked with firmer fruit, better color development, and stronger stems. Deficiency often shows as marginal leaf scorch on older leaves, slow growth, and weak flowering under stress.
2) Targets for nutrient solutions and tanks
For fertigation and hydroponic mixes, potassium is commonly expressed as ppm (mg/L) of elemental K. Typical working ranges are often 80–250 ppm K depending on crop stage, water alkalinity, and total salts. This calculator translates a ppm target and tank volume into grams of fertilizer, then reports mixing strength in g/L. Record your ppm setpoints and EC readings to refine recipes across seasons and cultivars.
3) Converting label grades into elemental K
Many fertilizer labels list potassium as K2O. Elemental K is lower than K2O by a constant factor. The calculator uses K% = K2O% × 0.8301, so a 50% K2O source delivers about 41.5% K. Using the correct label value reduces dosing error, especially in concentrated stock solutions.
4) Soil and bed applications with split doses
For beds and field plots, rates are often given as grams per square meter or per square foot. The soil mode converts your chosen rate into total elemental K demand across the area, then back-calculates product mass. Splitting doses into 2–6 applications can improve uptake and reduce salt spikes in container media and raised beds.
5) Mixing safety, compatibility, and data reporting
When measuring small weights, a 1–5% safety factor can cover scale tolerance and transfer loss. Avoid combining calcium sources with sulfate or phosphate concentrates in the same stock to reduce precipitation risk. After calculation, export CSV or PDF to document targets, inputs, and doses for repeatable batch preparation.
FAQs
1) Does ppm here mean elemental potassium or K2O?
The ppm input is elemental potassium (K) in mg/L. If your guideline is in K2O, convert to K using the 0.8301 factor, then enter the resulting ppm K for accurate dosing.
2) Why does the calculator ask for purity?
Purity adjusts for blends, fillers, or lower-active products. If a label indicates the product is not fully active, enter the estimated purity so the calculator increases the required grams to meet your K target.
3) Which fertilizer source should I select?
Choose the source you actually have, then verify its label grade. Sulfate is common for chloride-sensitive crops, nitrate also adds nitrogen, phosphate sources add phosphorus, and chloride sources are economical but may not suit all plants.
4) Can I override the analysis percent?
Yes. Enter your bag’s K2O% or K% in the analysis field. The calculator will use your value instead of the typical defaults, which improves accuracy across different brands and regional formulations.
5) How do I use the soil mode rate field?
Enter a rate as grams per selected area unit, then specify whether that rate is K2O or elemental K. The calculator converts everything to elemental K and calculates total product needed for your full area.
6) What is a safe safety factor value?
Most users keep it at 0–5%. Use the lower end when you have an accurate scale and consistent mixing. Use a small factor when measuring tiny doses or when transferring powders between containers.
7) Why do I see a g per L mixing strength?
It is a practical way to compare recipes and check dissolvability. High g/L values may require warm water, longer mixing time, or split additions. It also helps standardize dosing across different tank volumes.