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LCF Australia

Nutrient guide

Humic substances and humate

Humic substances are part of soil organic matter. Humates are concentrated forms, used in some fertilisers to support nutrient efficiency.

What humate is

Humic substances form as organic matter breaks down. Commercial humates are usually extracted from lignite, leonardite or peat. Potassium humate is a soluble form that can be included in compound fertilisers. Products are usually described by their humic acid and fulvic acid content.

What research suggests

  • Nutrient retention: humic substances can hold positively charged nutrients and form complexes with trace elements, which research suggests may help keep nutrients in the root zone and available to plants.
  • Soil structure: as part of soil organic matter, humic substances are linked to better soil aggregation and water holding. Meaningful changes to soil structure generally need large, sustained inputs of organic matter, not small additions in fertiliser.
  • Root growth: controlled studies suggest humic substances can stimulate root growth in some conditions.

Responses vary

Results depend on the soil, the season, the product and the rate. Much of the positive research comes from controlled-environment studies and from farming systems overseas, including China. Australian dryland field results so far have been mixed, and some trials have shown no benefit. Humate complements fertiliser and soil management. It does not replace them.

How humate products are described

  • By humic acid and fulvic acid content, together with the test method used.
  • By source material, such as lignite, leonardite or peat.
  • By the trial evidence available for particular crops and soils.

Crop guides

Where humates come from

  • A dark brown to black lump of leonardite on a white background
    Leonardite, a weathered lignite and one of the materials commercial humates are extracted from. Specimen from North Dakota, USA. Photo: James St. John, CC BY 2.0, via Wikimedia Commons.

Photos may show other crops with the same symptom. Full credits: Image credits.

How LCF products fit

LCF Australia supplies compound fertilisers made by our manufacturing partner Lardmee (LDM), including Urea Plus and zinc and manganese sulphates, on enquiry. We also supply the Field Spears soil testing kit, which reads soil N, P, K and pH in the paddock. Which product suits, how much and when depends on the soil, the crop, the season and how you apply it.