Home Meadmaking Science gives a practical dosing ratio for mead must: about 8 g of diammonium phosphate (DAP) and 4 g of a complex nutrient blend such as Fermaid K, per 19 L (5 gal) batch — scaled linearly to your actual batch size.
Why mead needs nitrogen supplementation more than most fermented drinks
Yeast Assimilable Nitrogen (YAN) covers the forms of nitrogen — ammonia and free amino acids — that yeast can actually use to build new cells and complete fermentation. Grape must and malted grain both naturally contain a reasonable amount of usable nitrogen. Honey diluted with water does not: it's 85-95% sugar by dry weight, with only trace amounts of minerals and amino acids left over.
Without supplementation, mead fermentation runs slow, can stall before finishing, and stressed yeast cells are more likely to produce hydrogen sulfide — a compound with a sharp rotten-egg smell.
What's the dosing ratio?
Rather than back-calculating a dose from a specific YAN target, the book gives a practical starting ratio and says so directly: "calculating the truly ideal dose requires lab analysis of the specific must... the figures given here are a practical starting point, not a rigid formula." That ratio, scaled to batch size:
≈ 8 g DAP + 4 g complex nutrient blend (e.g. Fermaid K), per 19 L
Most published research points to 267 mg/L YAN as the optimal target for mead fermentation specifically — higher than the 150-250 mg/L range typically cited for wine, reflecting how much further honey falls short on its own. That figure is useful context for why mead needs supplementation at all, but getting an exact dose to hit it precisely isn't possible without lab-testing your specific must — which is exactly why the book gives a practical ratio instead. International standards (based on OIV guidelines) cap DAP-derived nitrogen at 300 mg/L; going past that risks excess yeast biomass and a buildup of ethyl carbamate.
Scaling to your batch size
Both amounts scale linearly with volume:
| Batch size | DAP | Fermaid K (or similar) |
|---|---|---|
| 4 L (1 gal) | 1.7 g | 0.8 g |
| 19 L (5 gal) | 8.0 g | 4.0 g |
| 23 L (6 gal) | 9.7 g | 4.8 g |
Why not use DAP alone?
DAP supplies nitrogen, full stop — it doesn't provide the broader range of micronutrients (amino acids, vitamins, minerals) that a complex blend like Fermaid K contributes alongside it. Pairing the two gives yeast a more complete nutritional picture than nitrogen alone.
Why splitting the dose across several days matters
Adding the full calculated amount in one shot at pitch is a common mistake. At the very start of fermentation, the yeast population is still small and can't efficiently take up a large nutrient dose all at once — part of it goes unused, and an overwhelmed, stressed colony is more likely to produce hydrogen sulfide as a byproduct.
Split the total dose into portions added over the first four days of active fermentation — for example, roughly a third at pitch, a third around day two, and the remainder around day four — rather than dosing everything up front.
In a controlled experiment, adding DAP to honey must cut fermentation time at 25°C (77°F) from 10 days down to 4 days, and the finished mead also showed higher concentrations of esters responsible for pleasant fruity aroma notes. Nitrogen deficiency doesn't just slow fermentation down — it measurably hurts the finished drink's aroma.
Skip the manual math
The mead calculator's Nutrient tool applies this ratio directly, plus builds a staggered Day 0/2/4 dosing schedule for your batch size.
For the full comparison of nitrogen sources (DAP, pollen, Fermaid) and the chemistry behind YAN, see Home Meadmaking Science, Chapter 3.
Handle DAP and other fermentation salts as directed on the product label. This is a practical starting ratio, not a lab-precise dose — adjust based on experience from previous batches, and don't exceed the 300 mg/L OIV nitrogen ceiling.