Wood ash

Mineral residue left after burning wood, alkaline and rich in calcium and potassium.

Characteristics

Contains about 25% calcium and 5% potassium, plus phosphorus and magnesium.
Alkaline: its carbonates and oxides raise soil pH.
Nitrogen and sulfur are lost during combustion.
Traditionally added to bokashi, biol and compost as a mineral source.

Role in the preparation: Supplies minerals and raises pH in bokashi, biol or mineral mixtures.

Caution: It is caustic: wear gloves, goggles and a dust mask, use only ash from clean unpainted, unvarnished wood, and never mix it with urea or ammonium fertilisers.

Sources: UNH Extension - Guide to Using Wood Ash as an Agricultural Soil Amendment · Oregon State University Extension - Use fireplace ash sparingly to boost garden soil

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.