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Humic and fulvic acid (potassium humate)

Potassium humate is a soil amendment combining humic and fulvic acids extracted from leonardite, a soft oxidised brown coal. It is sold in powder, flake, granular and liquid grades for drip and broadcast application and is notified under the FCO biostimulant schedule.

Composition

  • Active substances: humic acid (the higher-molecular-weight, alkali-soluble fraction) and fulvic acid (the lower-molecular-weight, fully water-soluble fraction); see Humic Acid and Fulvic Acid.
  • Typical analysis: 50-70% total humic substances plus 8-12% K2O (as potassium counterion).
  • Source: alkaline digestion of leonardite (oxidised brown coal).
  • Form: free-flowing black powder, flake or liquid concentrate.

Mode of action

Humic substances act on three concurrent fronts. They chelate cations and micronutrients, holding them in plant-available form across a range of soil pH; they raise the cation-exchange capacity of the rhizosphere, reducing leaching losses; and they stimulate root proliferation and membrane activity, increasing the active root surface area. The fulvic fraction is preferentially absorbed through the cuticle and is the active component in foliar formulations, while the larger humic-acid molecules anchor in the soil and condition aggregate stability.

Target use and dose

Typical drip application rate is 0.5-1 kg per acre per season, distributed across the crop cycle in several smaller doses rather than a single shot. Common use cases include sugarcane fertigation, banana drip programmes, intensive vegetable cultivation and heavily cropped paddy soils (see Humic Acid Paddy). The product is also added to FYM or compost stacks to enrich the humic content of the finished material.

Safety and regulatory status

FCO-notified plant biostimulant/soil conditioner. Compatible with most water-soluble fertilisers. Should be kept dry in storage; humidity causes caking and reduces solubility.

See also: Humic Acid, Fulvic Acid, Humic Acid Paddy, Leonardite Soil Conditioner, Gypsum In Groundnut.

References

  1. Potassium Humate Technical Reference. humicacid.org.
  2. Humic Acids Crops Technical Report. USDA Agricultural Marketing Service.