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Why Clay Soil Amendments for Sandy Soils Are a Permanent Fix to Water Repellence Issues.




Let's face it, most soils do not provide ideal growing conditions for all plants right away.


And coastal soils around Australia are terrible for the average suburban garden.


Drive around most suburbs and you'll see

  • Dead, dried out & patchy lawns

  • Struggling and straggly plants

  • Dried out leaves, dead branches,

  • Neglected gardens full of weeds because it's become too hard

  • Sick vegetables that are pest infested and don't produce

  • Lost money from dead nursery plants,

  • Gardeners applying repeated dosing's of soil wetting agents. Mostly in vain.

Coastal sandy soils are commonly water repellent and unless you have access to cheap mains water, or a bore for free water to constantly dowse your plants, gardening can be expensive and wasteful.


It generally takes someone who can withstand big water bills and big nursery bills to keep their garden lush, green, thriving, busy with life.


But, have you ever hoped that there might be some way to have a lush and healthy garden without having to poor tons and tons of water onto a water-resistant garden bed?


The short answer to that question is YES, there is a better way using a secret soil amendment known as Kaolin Clay which when blended in the right quantities gives amazing results.


Don't Soil Wetting Agents Make My Sandy Soil Retain Moisture, I Hear You Ask?


Firstly, let me explain why our Sandy Soils are water repellent. Perth and Adelaide like the rest of Australia get very hot in summer and it stops raining.


Funnily enough Perth gets more annual rainfall than Melbourne, Hobart and even London. I bet you didn't expect that. But from mid-October to the end of March - that's four and half months, there is next to no rain at all. And it gets hot, damn hot


And this results in not only our sandy soils drying out, but the fact they become water repellent as well. Water repellent soils are called hydrophobic.


Have you ever soaked a patch of garden for 5 minutes to kick the sand and see heaps of dry patches? You are probably wondering, where did the water go?


Well, it went down lots of little tunnels and far away from where it was intended. The sandy soil has become hydrophobic and channelled the water through it rather than soaking it up like a sponge.


I'm sure you'll agree, having a garden that needs watering once or twice a day is no fun at all. Plus, it's wasteful and it's expensive.


There are solutions and some work better than others. Some work temporarily and some work permanently (We'll get to those).


Let's look at the usual temporary ways we try to solve our dry crispy gardens.


Soil Wetting Agents - Do They Fix Water Repellence?


Soil wetting agents are known as temporary soil treatments as they don't permanently fix the issue, they just mask it for a time. Plus, there are some other environmental issues not always mentioned from run off.


Wetting agents may work quite well initially and if you are diligent and re-apply you will get marginal moisture retention in your soils.


Soil Wetting agents need to be put on regularly to have an effect for a time. You'll need to use them every few months as the wetting agent breaks down.


Regularly, buying soil wetting agents will cost you money several times a year...every year. It's not an ideal solution financially nor environmentally speaking. Soil Wetting agents are like band-aids - they just mask the problem rather than fixing it for good.


The garden conscious consumer could spend about $50 - $80 on wetting agents each year which is about $500 - $800 over 10 years. It would be even more if following label recommendations!


Mulches and Water Repellence - Is This the Solution?


Mulches are great for holding in moisture, but mulch itself can become hydrophobic over time.


According to Mulch tests conducted by researchers you need to get a chunky mulch to reduce moisture evaporation from the soil and to allow moisture to get to the plants from rain and watering.


Water can get into the soil through the gaps in chunky mulch and it reduces moisture loss from evaporation. While fine mulches will stop water from even getting to the soil.


Checkout out this article on choosing mulch for your garden

https://www.sgaonline.org.au/choosing-mulch-for-your-garden/


Mulches will eventually break down in the soil as they are consumed by bacteria, fungi, and insects.


I am always amazed at how areas of thick mulch disappear over time leaving the dry sandy soil exposed again with no long-term benefit to the soil.


Mulches, even from native vegetation, also create a waxy water repellent residue making the problem of soil hydrophobia worse. (Source: https://soilquality.org.au/factsheets/water-repellency).


Adding Compost and Manures - Will this Work?


Compost and Manures are definitely great for plants and are considered soil conditioners.


What you may not realise is that compost and manure get used up and consumed by the organisms and plants until you are left again with the remaining hydrophobic soil; as they also leave the waxy water-repellent residue.


The compost and manure will be taken up by the plants, but the soil structure and composition with not be improved.


In conclusion, the use of wetting agents, mulches, composts and manures are all temporarily helpful but not permanently helpful in improving the capacity of soil to retain water.

So, What do the Scientists Say About Amending Sandy Soils?


With water repellent soils occupying more than 5 million hectares of western and southern Australia (Roper, 2004), you can be sure the CSIRO and universities around Australia have looked at soil amendment solutions.


So, what did they discover?


They found that coarsely textured sandy soils that contain less than 5 % Kaolin clay are very susceptible to becoming water repellent.


And it was found that water repellence only occurred in soils with less than 5% Kaolin clay.

And, this is what was concluded...


Getting more than 5% Kaolin clay content mixed in with your soil and preferably around 15% clay content permanently solves water repellence in sandy soils.

Clay binds water to tiny spaces between the sand particles where it stays there until plants need it.


  • So, water can be stored through Kaolin clay for weeks or months.

  • Kaolin clay sticks to sand and humus to form “peds of soil”, in short “soil”.

  • The clay and humus hold more water in the soil

How Much Clay Should I Amend Into My Soil?


The ideal soil is described as a sandy loam, which is a soil that has a good mixture of both sand and clay.


It simply means that the large particle (sand) have small particles (clay) mixed in.


A combination of good moisture retention and soil that is light well aerated and easy to dig.


Loam is usually broken down something like this.

  • 40% Sand

  • 40%Silt

  • 20%Clay

Sandy loam is much better at retaining nutrients such as fertiliser and minerals. Sandy soils alone do not do this, so more fertiliser is used than in a good sandy loam.


Researchers have discovered that adding the right type of clay and silt to your sandy soil in the right proportions will permanently amend your soil to never be hydrophobic again.


Because your soil is no longer hydrophobic your soil can now develop a healthy biology of organisms and fungi (like Mycorrhizal fungi) that create the environment needed for a thriving plant root system.


Why is Kaolin Clay Better Than Bentonite Clay for Sandy Soil Amendment?


Professor Dan Carter in his research on amending sandy soils found that not all clays work equally well.


Australia has both Kaolin clay and Bentonite clays.


When you buy kitty litter for your cat to wee in, the product used is a clumping clay that sticks together. This is Bentonite clay.


When you go out to rural areas. Many of the farmers dams have bentonite clay as their base because the clay is excellent at stopping the water seeping out.


Bentonite is an “absorbent and a sealing clay”. This means it tightly holds minerals, making it harder for plants to get the minerals and water.


Bentonite also binds with only other bentonite particles, not sand or humus, hence the reason it's used as a dam sealer and bore sealer.

You might think this is a good thing, but researchers found that the bentonite clay did not spread evenly throughout the soil because of its clumping nature.


You can in fact get clumps of bentonite clay sitting in your water repellent sandy soil.


Kaolin clays on the other hand is a dispersive clay meaning it will disperse in sand.


Kaolin clay does not have the same clumping tendency as bentonite clay and has been found to spread more evenly through the soil. This provides greater water absorbency in the soil and more evenly improves the soil structure. It becomes the structure of the soil.


How do I Fix My Water Repellent Sand Soil With a Kaolin Clay Soil Amendment Then?


Most garden plants and lawns will thrive if the top 20-30cm of sandy soil is amended with a scientifically blended Kaolin clay, silt and rock minerals mixture, mixed in with your sandy water repellent soils.


Which means it is definitely easier if you amend your soil before you lay your turf. Something landscapers, turf providers and new home builders should take into consideration.


While garden beds not under grass, can have Soil Solver’s clay- based soil amendment products added to the sandy soil much more easily to amend them.


A clay mix can be blended with the existing poor-quality sand for front and rear lawns without having to take away the existing sand. This sand becomes quality soil due to the addition of the clay- based amendment to the right percentage range.


Your sand is 100% of the problem, but 85% of the solution.

Landscapers therefore do not need to truck in the equivalent amount of landscape mix which still does not contain enough clay content to keep the soil water absorbing in the long term.


The investment in the clay amendments is commonly more than offset by not having to remove topsoil, and not having to bring in landscape mix.

This means it can be cost positive to amend your garden.


From here you will be saving money weekly on reduced water usage, fertiliser needs, and there will be no need for soil wetting products ever. Plus you'll be enjoying a healthier garden. Therefore, a healthy environment for you and your family.


We have found that blending an Australian Standard kaolin clay, silt and scientifically blended rock minerals mixture through the sandy soil at a specific rate per square meter gets the clay and silt content to levels that promote a substantially healthier soil and plant growth.


As evidence, Perth's Garden Gurus producer Trevor Cochrane planted two lime trees next to each other.


With one tree as he planted it, he added Soil Solver® Clay Plus Minerals, a kaolin clay based clay-based soil amendment. It has grown to twice the size of the other.


You can check his TV Show video reel here to see the effect: https://www.thegardengurus.tv/story.php?country=0&id=5457


Perth's Garden Gurus Presenter Trevor Cochrane has stated on air that he amends all his landscaping projects that have sandy soils with the Kaolin based Soil Solver® product which contains clay, silt and rock minerals.



Reference: (https://www.thegardengurus.tv/story.php?country=0&id=5472)


How Much Clay Based Soil Amendments Should I Use on My Sandy Soil to Amend Water Repellence?


It is important that your soil amendment has enough clay to provide water absorption for plants for months of low rainfall. The most effective rate is 15kg per sqm.


This works to get the clay percentage in the soil to between 10%-20%4%-8%for most Perth and Adelaide Australia’s sandy soils.


The silt content product disperses throughout the soil giving it a light fluffy feel while allowing aeration in between particles so roots can breathe easily.


The rock minerals add vital nutrients that are essential to plant growth promoting healthy plants.


Getting the rock minerals into the soil and in the right balance alongside the moisture retaining clay has been described as a game changer by gardening experts for abundant healthy gardens.


Soil Amendments Versus Soil Conditioners & Treatments - What's The Conclusion?


Soil treatments such as soil wetting agents are extremely short-term solutions.


Adding compost and manure are medium- term solutions treatments that ultimately do not permanently change the soils composition, leaving you back where you started.


Your sandy soil will revert to holding less moisture and nutrients as the compost and manure is used up.


However, a permanent soil amendment that adds clay to the soil in the form of kaolin clay will permanently change the structure of the soil.

Once clay is added, it never disappears. Whereas manure and compost will disappear. This allows for longer term moisture retention and means the soil biology can flourish and feed the plants root systems.


Soil Solver® Clay Plus Minerals is a Kaolin clay- based soil amendment product with added rock minerals and silt to create a permanent solution for west and southern Australia’s sandy soil conditions.


If you are a home gardener, you can find our soil amendment products on our outlets page. For landscapers and busy gardeners we can deliver in bulk to your location.


Checkout the results of using a quality soil amendment product.








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