Masters Mix is a supplemented hardwood substrate — hardwood sawdust plus soy hull — and it is the highest-yielding bulk substrate in common use for wood-loving mushrooms. We supply it pre-blended at 60% oak / 40% soya hull, by the tonne, at £750 including VAT and UK mainland delivery.
What it is and why it works
Plain hardwood is a good substrate but a nutritionally poor one. It gives the fungus carbon in abundance and very little nitrogen. Growth is reliable but yields are modest.
Soy hull is the opposite — high in nitrogen, readily accessible, and cheap. Combining the two gives a substrate with both the structure and carbon of hardwood and the nitrogen to actually build fruiting bodies. Growers commonly report substantially higher yields than plain hardwood, particularly on oyster species and lion’s mane.
The formulation is generally credited to T.R. Davis of Earth Angel Mushrooms, and the original published ratio is 50:50 hardwood to soy hull by dry weight.
Our ratio is 60:40, not 50:50
Worth knowing before you order. Ours runs 60% oak to 40% soya hull — slightly hardwood-heavier than the published formulation.
The practical effect is a marginally lower nitrogen load. That cuts both ways. A lower nitrogen fraction means slightly less fuel for a maximum-yield flush — but it also means less readily available nitrogen for competitor organisms to exploit if your sterilisation is imperfect. Growers who have fought contamination on a full 50:50 in a less-than-ideal setup often find a hardwood-heavier blend noticeably more forgiving.
If you are running a validated 50:50 process and hitting your numbers, do not switch a whole farm on our say-so. Test a small batch against your existing substrate before committing a pallet.
Sterilise. Do not pasteurise.
This is the single most common way people fail with Masters Mix, and it is worth being blunt about.
Plain hardwood can be pasteurised because there is little in it for contaminants to eat. Supplemented substrate is different — the nitrogen that drives your yields is equally attractive to Trichoderma, bacteria and competitor moulds. Pasteurisation leaves survivors, and in a nutrient-rich substrate those survivors win.
Standard practice is full pressure sterilisation in filter-patch bags — typically around 15 psi for 2 to 2.5 hours depending on bag size and load, then cooled fully before inoculation. Follow your own validated process; treat these figures as orientation, not instruction.
Hydration
Roughly 1:1 by weight is the usual starting point — but supplemented substrate holds water differently to plain hardwood, so trust the squeeze test over the ratio.
At field capacity, a firm squeeze should produce a few drops of water and no more. Too wet is worse than too dry: waterlogged substrate goes anaerobic, invites bacterial contamination, and will not colonise. Err dry and adjust up.
Species it suits
- Oyster (Pleurotus spp.) — blue, pink, golden, king. The classic application, and where the yield difference is most obvious
- Lion’s Mane (Hericium erinaceus) — responds very well to supplementation
- Shiitake (Lentinula edodes) — works, though it needs a longer colonisation and browning period
- Reishi (Ganoderma spp.)
Not appropriate for species that want a composted or manure-based substrate.
Why pre-blended
You can absolutely blend your own from oak pellets and separately bought soy hull, and if you want to tune the ratio yourself you should.
The case for pre-blended is consistency. Blending in-house means two stock lines, two deliveries, weighing at every batch, and a ratio that quietly drifts as bags run down and someone eyeballs the last scoop. Pre-blended pellets remove the most common source of variation between one production run and the next — which matters a great deal when you are trying to work out why this batch underperformed.
Specification and ordering
- Composition: 60% oak, 40% soya hull
- Diameter: 6mm
- Moisture: below 10%
- Packaging: 15kg sealed bags, approximately 1 tonne per pallet
- Price: £750 per tonne inc VAT (£625.00 ex VAT), UK mainland delivery included
Prefer plain hardwood? See our HWFP substrate guide. Running a commercial farm and need four pallets or more? Request bulk pricing.