Consumer advocacy teardown
Nitrate of Potash alternative & active ingredient dupe
Stop paying £5.99 for Westland. The bulk active is Potassium nitrate 13-0-46 (nitrate of potash) — 25% less per working litre than a typical pack.
- Active
- Potassium nitrate
- CAS
- 7757-79-1
- Dupe
- Potassium nitrate 13-0-46 (nitrate of potash)
- Saving
- 25% / L
Saving is per litre of working-strength mix versus a typical pack price, not versus the DIY kit total. Shop prices move — always check the listing.
The Marketing Claim & The Catch
A typical 1.5 kg box pack of Westland Nitrate of Potash is about £5.99 in lawn & garden. That is a snapshot, not a live Amazon price — listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: High-potash feed for tomatoes, fruit and flowers; and Improves fruit quality and drought tolerance.
The catch: This is not Tomorite (a dilute 4-3-8 bottle) and it is not 20-20-20. Potassium nitrate is 13-0-46: nitrogen plus potash in one salt. The garden-centre 1.5 kg box is agricultural KNO3 with a tomato on the front. Buy it in 5 kg.
- “High-potash feed for tomatoes, fruit and flowers”
- “Improves fruit quality and drought tolerance”
Proprietary Blend & Dosage Breakdown
The labelled active is Potassium nitrate at 100%. Everything else in the pack is none (prills).
Even when the pack is sold as “pure” or ready-to-use, the dose that actually does the work is Potassium nitrate. The rest is how they get it into a bottle you will pick up.
Branded working strength is whatever comes out of the bottle. The bulk alternative is 99% Potassium nitrate 13-0-46 (nitrate of potash), mixed to 1 g/L (weekly fruiting feed).
- Labelled active
- Potassium nitrate
- 100%
- Carrier
- None (prills)
- Retail pack
- 1.5 kg box · £5.99
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Potassium nitrate 13-0-46 (nitrate of potash) at 99% bulk. Indexed as CAS 7757-79-1, formula KNO3. Buy it as 5 kg for about £14.99 from Amazon UK.
Working strength: 1 g/L (weekly fruiting feed). Indicative cost £0.00 per diluted litre — 25% below a typical branded pack on a per-litre basis, before you reuse leftover bulk.
Follow the mixing method and the supplier SDS. Wear the listed PPE. Do not mix incompatible oxidisers, acids or ammonia.
- Oxidiser — keep away from fuels and acids. Gloves if you have broken skin. Store dry.
- Dissolve 1 g per litre of water as a weekly fruiting feed, or follow the 5 kg bag. That is the same salt as the 1.5 kg box.
- 5 kg at 1 g/L is 5,000 litres of feed. A 1.5 kg box is 1,500 litres.
- Oxidising fertiliser: do not mix into homemade fireworks. Garden use only.
Mixing desk
Dilution calculator
Switch between filling a sprayer and covering a measured surface. Figures are educational estimates from the listed ratio — always check the SDS.
Formula
Potassium nitrate 13-0-46 (nitrate of potash)
- Concentrate
- 5 g
- grams of solid
- Water
- 5 L
- carrier volume
- Batch cost
- £0.01
- 5 L working solution
- Saved vs retail
- £0.00
- 25% · retail £0.02
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedWestland | Raw active dupeDupeStack |
|---|---|---|
| Product | Nitrate of PotashAmazon UK search — listing, not a confirmed seller | Potassium nitrate 13-0-46 (nitrate of potash) |
| Pack / unit | 1.5 kg box · £5.99 | 5 kg · £14.99 |
| Active | Potassium nitrate at 100%Carrier: None (prills) | 99% bulkKNO3 |
| CAS number | Not disclosed on pack | 7757-79-1 |
| Working strength | Ready-to-use pack | Dilute 1 g/L (weekly fruiting feed) |
| Cost per litre | £5.99 / pack | £0.00 / L mixed from bulk |
| Headline saving | Baseline | 25% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene) |
Active ingredient and cheaper alternative — FAQ
What is the active ingredient in Westland?
Westland Nitrate of Potash is labelled as Potassium nitrate at 100%. The carrier is None (prills). Pack size: 1.5 kg box. The bulk equivalent we index is Potassium nitrate 13-0-46 (nitrate of potash) (CAS 7757-79-1).
Is Potassium nitrate 13-0-46 (nitrate of potash) safe on lawns?
Used at the listed working strength (1 g/L (weekly fruiting feed)), the dupe is the same chemistry as the branded pack for lawns, beds and pots. That is not a blanket all-clear: read the supplier SDS, wear the listed PPE, keep acids away from hypochlorite, and follow UK HSE/COSHH rules. Wellness teardowns are supplements, not medicines.
Is there a cheaper alternative to Westland Nitrate of Potash?
Yes. The bulk equivalent is Potassium nitrate 13-0-46 (nitrate of potash) (CAS 7757-79-1). Indicative saving 25% per working litre versus a typical £5.99 pack. Working strength: 1 g/L (weekly fruiting feed). Live shop prices move.
How do you mix the Nitrate of Potash dupe stack?
Oxidiser — keep away from fuels and acids. Gloves if you have broken skin. Store dry. Dissolve 1 g per litre of water as a weekly fruiting feed, or follow the 5 kg bag. That is the same salt as the 1.5 kg box. 5 kg at 1 g/L is 5,000 litres of feed. A 1.5 kg box is 1,500 litres. Oxidising fertiliser: do not mix into homemade fireworks. Garden use only.
DupeStack provides chemical concentration data and educational mixing guides. Always review official manufacturer Safety Data Sheets (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Some links on this site are affiliate links.
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DIY stack · 25% / L vs branded
£23.50indicative kit · Amazon cannot add a mixed search kit as one basket