Sand Is Not Soil: The Living Glue That Helps Hold Water, Minerals and Roots
A grower from the coastal strip of Western Australia contacted me recently with a very familiar problem. Poor sandy soil. High pH. Water disappearing almost as quickly as it is applied.
He was building the soil and wanted to know whether Earthfood should be part of that process. My answer was yes, but the reason is much more interesting than simply putting microorganisms into sand.
Because microbes can help make 'soil glue'.
Functioning living soil microorganisms manufacture an extraordinary range of sticky biological compounds around themselves. Scientists call some of these materials extracellular polymeric substances, or EPS.
That sounds suitably complicated. They help hold things together. And on Australia's coastal sands, that matters enormously.
Why sand behaves so differently from good soil
Anyone gardening or farming across much of Perth, knows the problem. Water goes on. Water disappears. Fertiliser goes on. A surprising amount of that can disappear too.
The plant struggles while the person growing it keeps adding more water and more input.
Western Australia's Department of Primary Industries and Regional Development describes the sandy soils of the Perth Sedimentary Basin as difficult to manage because of low fertility, low water-holding capacity, water repellence and susceptibility to erosion. Research on the Swan Coastal Plain has also documented the limited capacity of many sands to retain nutrients such as phosphorus.
This is not just a Western Australian problem.
People growing on coastal sands around Queensland, including parts of South East Queensland, know the same frustration. Queensland Government soil guidance describes sandy soils as having low moisture and nutrient-holding capacity. The reason begins with physics.
A grain of sand is large compared with a clay particle. Put thousands of sand grains together and there are plenty of large spaces through which water can drain, but relatively little fine surface area capable of retaining water and nutrient ions.
Good soil is different. It is not simply a pile of minerals.
Good soil contains mineral particles, organic matter, roots, water, air, fungi, bacteria, protozoa and other organisms arranged into an extraordinarily complex living architecture.
The architecture is the part we keep forgetting.
Microbes manufacture their own building material.
When microorganisms establish themselves around a root or soil particle, many produce extracellular polymeric substances. Think of them as microscopic sticky matrices.
EPS can contain polysaccharides, proteins and other compounds. They help microorganisms adhere to surfaces, create biofilms, protect themselves against environmental stress and trap water and nutrients around the microbial community.
Research reviews describe microbial EPS as important in soil aggregation, moisture retention and nutrient entrapment, particularly because of their ability to bind particles together and create a more stable microenvironment.
That starts changing the way we should think about sandy soil.
We normally try to solve sand by putting something onto it. More fertiliser. More wetting agent. More water. More minerals. But perhaps we should also be asking:
Who is building the soil?
Because biology is not simply consuming what is already there. Biology is physically changing the environment in which it lives.
Then the fungi arrive with their own construction system.
Fungi add another dimension. Their microscopic filaments, called hyphae, travel through the soil and around particles, organic material and roots. Those networks can physically enmesh material and contribute to aggregate formation.
Then there is glomalin. For years, glomalin was popularly described as the great fungal "soil glue", associated particularly with arbuscular mycorrhizal fungi.
There is good evidence connecting what researchers call glomalin-related soil proteins with soil aggregation and aggregate stability. A 2024 Cornell-led review, for example, describes their binding characteristics and association with soil aggregation.
But science has moved on, and this is where we should move with it.
A major 2026 review in Soil Biology and Biochemistry cautions that the material traditionally measured as "glomalin-related soil protein" is actually a chemically mixed fraction and should not automatically be treated as a direct measurement of mycorrhizal fungi.
That doesn't destroy the soil-glue story. It actually makes it more interesting. There isn't one magic glue.
Living soil is held together by a biological construction crew.
Microbial EPS. Fungal hyphae. Root exudates. Organic compounds. Fungal-associated proteins. Decomposed organic matter. Mineral surfaces. Roots themselves. Together they begin building structure.
Why structure changes water?
This is the part that matters to the grower watching irrigation disappear through sand. When soil particles, organic matter and biological materials begin forming stable aggregates, the arrangement of pore spaces changes.
Large pores allow air and water movement. Smaller pores retain water against gravity. Organic matter itself can retain substantial moisture. Microbial films hold microscopic films of water close to organisms and roots. Root growth adds still more structure and carbon.
So the objective is not to somehow coat every grain of sand with magic glue and create instant loam. It is to progressively build a more complex living root zone. That distinction matters.
Pure sand gives biology very little construction material to work with. Give that same biological community plant roots, decomposing organic matter, compost, mulch, carbon-rich habitat and minerals, and suddenly it has far more to build with.
This is why I keep saying:
"Carbon doesn't build soil. Biology builds soil. Carbon becomes stable because living microbial communities create the architecture that holds it". Bronwyn Holm
Sand makes that statement particularly easy to understand. You can add carbon to sand. But unless a functioning biological community begins cycling it, colonising it and integrating it with roots and minerals, you still don't have the same living architecture we call healthy soil.
High pH adds another problem.
The WA grower who contacted me also mentioned high pH. That is significant. Some Western Australian coastal sands are calcareous and naturally alkaline. Western Australian soil references describe calcareous coastal sands occurring over limestone or calcrete and having alkaline pH throughout the profile.
High pH changes nutrient chemistry.
Queensland Government guidance notes that alkaline soils can develop deficiencies in zinc, copper, boron and manganese, while Australian soil resources also identify reduced availability of iron, manganese, zinc and copper in moderately to highly alkaline conditions.
This is another reason simply adding more fertiliser can become a very expensive habit. The mineral may be present. The plant still has to access it. And that brings us straight back to the root zone.
Microorganisms participate in nutrient transformation, mineral weathering, organic acid production and the constant exchange of compounds occurring immediately around roots.
"Nutrients don't feed plants. Soil biology unlocks them. Without the living workforce beneath the surface, minerals can remain largely unavailable". Bronwyn Holm
That does not mean Earthfood instantly corrects a severely alkaline soil. It means that soil chemistry and soil biology should not be treated as separate worlds. They meet at the root.
So where does Earthfood fit?
Earthfood Life is a living soil microbial system. We are not trying to turn sandy soil into clay. We are trying to rebuild biological function in a soil that often has very little biological infrastructure.
That means establishing living microorganisms in the root zone where they can participate in nutrient cycling, organic matter processing, root interactions and the biological processes involved in soil structure.
And there is an important practical point here. Biology needs habitat.
On extremely poor sand I would not think of Earthfood as replacing compost, mulch, plant residues or other organic inputs. Quite the opposite. Those materials give biology something to work with.
And this is precisely why biochar becomes interesting in sandy soils as well. A good porous biochar can provide carbon-rich habitat and physical surfaces within which biological communities can establish.
Our Earthfood principle for this is simple:
BIOCHAR BUILDS THE HABITAT. BIOLOGY MAKES IT WORK.
That is not a slogan pulled from nowhere. It describes the partnership we are trying to create. Minerals provide raw material.
Carbon provides habitat and energy pathways.
Roots feed microbial communities.
Microorganisms process nutrients and organic compounds.
Fungal networks extend the biological architecture.
Microbial polymers help bind and stabilise material.
Water occupies the spaces that architecture creates.
And the plant sits in the middle of the entire living system.
Don't wait for winter. Follow the moisture.
Our WA grower also asked whether Earthfood should only be applied during winter because his sand dries quickly during summer.
No. The calendar is less important than the conditions.
Microorganisms need moisture. This is not 'wet' it is structurally moist to hold the sides of a hole as an example. Putting living biology onto scorching bone-dry sand and leaving it there without moisture makes little sense.
Summer application can work perfectly well when it is timed with irrigation, rainfall or an already-moist root zone.
Water is the carrier. Soil is the home.
What we want is to move the microorganisms into that root environment and give them the conditions needed to establish and function.
That may happen during a wet WA winter. It might equally happen beneath an irrigated orchard in January. The objective is not seasonal application. The objective is biological establishment.
Perhaps we have been asking the wrong question about sand.
For decades the question has been: What should I add to my sandy soil?
Perhaps there is a better one. What needs to start living there?
Because the difference between sand and functioning soil is not simply the quantity of fertiliser poured onto it. It is structure. Organic matter. Roots. Water. Minerals. And an enormous unseen workforce capable of connecting all of them.
A handful of living functional soil is not merely ground-up rock. It is habitat. It is architecture. It is chemistry being constantly rewritten by biology. And some of the smallest organisms in that handful are literally manufacturing the substances that help hold the whole thing together.
That is why rebuilding sandy soil is not simply about feeding plants.
We need to start building soil.