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How to: understand humates

Humates are prehistoric (20-50 million year old) decomposed organic matter, which is why they are sometimes referred to as ‘dinosaur compost’.

They are increasingly being used by gardeners as a soil additive - with impressive results. In fact you may already be using humates on your garden as they are a component in many high-quality fertilisers.



Humates are increasingly being used by gardeners as a soil additive - with impressive results. Photo - Arno King


When organic matter is composted it breaks down into humus, which we use to enhance soil fertility. As a final part of this decomposition, humic acid is formed, and when humic acid is crystallised it forms humates. Humates help retain essential plant nutrients in the soil; make many nutrients more readily available (as a chelating agent); stimulate biological activity; increase wettability and water-holding capacities of the soil; act as a buffer to harmful elements in the soil, such as high alkalinity, salt or contaminants such as residual herbicide or heavy metals); and help build better soil structure.


Who needs it

Humates are particularly valuable to gardeners in northern and central latitudes of Australia, where the soil is subject to heavy summer rains that leach nutrients and compact the soil. I’ve found using humates increased the vigour, growth and drought and pest resistance of plants.


How to use it

Humates are generally (and most cost effectively) available in dried form and resemble finely crushed charcoal. They can be mixed with water following manufacturer's directions, or sprinkled dry and dug into garden areas. Follow instructions and apply small quantities on a regular basis. I overdosed one bed in my garden by accident, and for a short time the plants there had very upright growth with extremely long internodes.


Where to get it

Humates are contained in many fertilisers, where they help to amplify other components. They are also available as a discrete product. Find them online, at produce suppliers specialising in organic and biological products and at garden centres.

About this article

Author: Arno King