Humic and fulvic acids

What is humic and fulvic acids?

Humic substances are the complex, heterogeneous organic molecules remaining after microbial decomposition of plant and animal material. They are operationally rather than chemically defined: humic acids are the fraction soluble in alkali but precipitating in acid, fulvic acids remain soluble at all pH values, and humins are insoluble. Commercial material comes mostly from leonardite, a soft oxidised lignite.

Because the definition is operational, humic acid is a class of molecules rather than a compound, and no two sources are identical.

What they do

Cation exchange capacity is the clearest mechanism: humic substances carry abundant carboxyl and phenolic groups that hold cations, buffering nutrient availability and reducing leaching. Chelation of micronutrients, particularly iron, keeps them plant-available in soils where they would otherwise precipitate.

Soil physical effects are also well established: improved aggregate stability, water-holding capacity and structure.

Direct biological effects on plants - enhanced root initiation and elongation, and hormone-like signalling - are reported consistently but are harder to attribute mechanistically, partly because humic preparations are so variable. Fulvic acid, being smaller and more mobile, is the fraction more often associated with direct uptake and foliar activity.

Reading the evidence honestly

The literature is large, positive on average, and heterogeneous - with variable source material, application rates, soil types and endpoints. Meta-analyses generally find modest positive effects on growth and yield, larger under stress and in poor soils, smaller in already fertile, well-managed systems. Presenting humic acids as transformative in a high-fertility soil would not be supportable; presenting them as beneficial in degraded, low-organic-matter or stressed conditions is.

What does humic and fulvic acids not do?

They are not fertilisers and supply negligible nutrients themselves. They will not correct a nutrient deficiency directly, only improve availability of what is present. They do not substitute for organic matter inputs at field scale - the quantities applied are small relative to soil organic carbon. And high application rates can immobilise some micronutrients rather than release them.

Where does humic and fulvic acids appear in the range?

Root Boost includes humic acid with L-tryptophan and seaweed extract. Charge BioBoost carries its microbial consortium in a 30% organic humic and fulvic, amino-acid and kelp base - where the humic fraction is functioning both as a biostimulant and as a carrier supporting microbial survival.