Plants don’t eat fertiliser — they absorb nutrients
Plants don’t eat fertiliser — they absorb nutrients
Applying fertiliser is only the first step.
Plants do not take up a bag of fertiliser as it was applied. Their roots absorb nutrients from the soil solution, mainly as dissolved ions. Nitrogen may be taken up as nitrate or ammonium, phosphorus primarily as phosphate, and potassium as potassium ions.
Before many nutrients can enter the plant, they must be released, dissolved or converted into a plant-available form.
That is why the condition of the soil and root zone matters.
Fertiliser supplies nutrients. The soil helps deliver them.
Once fertiliser reaches the soil, several processes influence what happens next.
Soil moisture helps dissolve nutrients. Clay and organic matter can hold some nutrient ions. Roots alter the chemistry immediately around them, while bacteria, fungi and other microorganisms help break down organic material and cycle nutrients.
This active area around the roots is known as the rhizosphere.
Peer-reviewed research describes an ongoing “cross-talk” between plants, roots, microorganisms and organic substances in the soil. Roots are not passive—they release compounds into the rhizosphere and influence the availability and uptake of nutrients. Read the research on soil–root cross-talk.
Where do humic and fulvic substances fit?
Humic substances are naturally occurring components associated with soil organic matter. They contain chemically active groups that can interact with soil minerals and certain nutrients.
Research reviews report that humic substances can support:
- nutrient availability and uptake;
- root branching and root-hair development;
- assimilation of macro- and micronutrients;
- plant metabolic activity; and
- biological processes within the root zone.
Their effects are considered biostimulant effects, rather than the direct supply of large quantities of fertiliser nutrients. This 2021 review explains the chemical structure and biological activity of humic substances.
A separate review of humic substances in agroecosystems examined their wider roles in soil fertility, nutrient cycling and plant growth. Read the review on the structure, function and benefits of humic substances in agroecosystems.
What could this mean in an orchard or crop?
For a horticultural grower, the goal is not simply to apply more fertiliser. It is to provide the right nutrients, in the right form, at the right time—and maintain a healthy root system capable of accessing them.
Humic and fulvic inputs may complement a well-managed nutrition programme by helping support:
- an active and well-developed root zone;
- the availability of certain mineral nutrients;
- efficient nutrient uptake and utilisation;
- balanced plant development; and
- better use of nutrients already present or applied.
They do not replace soil testing, leaf testing, fertiliser or good orchard management. Results can vary with the crop, soil, product source, application rate, timing and seasonal conditions. Research also shows that dose matters: applying more does not necessarily produce a better response.
This is particularly relevant in crops such as kiwifruit, where the objective is balanced growth, not excessive vine growth.
The takeaway
Fertiliser supplies nutrients, but healthy soil and an effective root system help plants access and use them.
Humic and fulvic products are designed to work alongside existing soil-health and nutrient programmes—not replace them.
At New Zealand Humates, we offer liquid and granular humate products for pasture, cropping, orchards and other horticultural systems.
Explore our product range or contact us to discuss which option may best suit your crop and nutrient programme.
Peer-reviewed research
Humic substances: Structure, function and benefits for agroecosystems — a review