Nutrient release from combustion residues of two contrasting herbaceous vegetation types

► N and P forms were evaluated in ash and char produced by muffle and flame combustion. ► Fire residues are mixtures of N and P forms not created at a single muffle temperature. ► HCO3− extracts only ~ 50% of initial P from flame-combusted, herbaceous biomass. ► Only 5% of initial N is extractable from herbaceous flame combusted biomass. ► Estimating muffle temperature for fire residues depends highly on parameter chosen.