Soil -


This is not a trick question.

They really do have something in common and it's potentially not good.

If you use an anti-perspirant (as opposed to deodorant) you will likely find it contains aluminium in a salt form.

When you spray the anti-perspirant under your arm the aluminium salts dissolve into the pores of your skin, effectively blocking them and stopping the perspiration.

There is some debate about aluminium and whether there are health issues arising from it's use in anti-perspirant's.

Mostly this is centered around the risk of breast cancer. It is also thought that it may affect estrogen.

Some studies show that the amount actually absorbed is tiny and won't cause a problem, but there may be a cumulative effect over time.

There seems to be a lot of conflicting information on this issue, but when it comes to plants and aluminium there is no question at all.

It's definitely bad.

Read on in this blog on soil pH to discover why....



The pH of your soil is critical in achieving optimum plant health and vigour.

Soil pH is a measure of how acidic or alkaline a particular soil is.

Why is this so important?

Because soil pH is a key factor that dictates nutrient availability.

The variability of nutrient availability based on pH is shown in the table below where one can clearly see the 'sweet spot' for nutrient availability is around the pH 6.5 to 7.0 mark.

This is the ideal soil pH for a great majority of ornamental plants although there are a few exceptions to this.

The table also clearly shows the effect on nutrient availability as you stray too far from the pH sweet spot.

Especially, note how (on the left side of the table) too low a soil pH has major implications for availability of just about everything.

And not only that, it raises the risk (particularly below pH 5) of solubilising aluminium in the soil which can become toxic to plant roots.



So, let's say you've tested your soil pH (see also our blog 'Soil testing Kits - a pass or a fail?') and it comes out as well outside the sweet spot.

How do you fix that?

Raising pH is relatively simple and is usually done using agricultural lime or dolomite.

The calcium in these products (and both calcium & magnesium in the case of the dolomite) has an acidity neutralising effect.

In both products the nutrient is in a carbonate form, which in practical terms means it's slow release.

So, how much should one use?

The answer is - how long is a piece of string?

I say this because it will vary based on soil type (sandier soils need less to raise soil pH and heavier soils will need more) and also the actual % of nutrient in the product which can vary significantly dependent on the source.

Refer to the instructions for use for a particular product. 

You will probably find the recommendations are around 50-200g/m2, with heavier rates for higher clay content soils.


And what if my soil is very high pH?

This is a bit trickier.

Usually elemental sulphur is used.

But to understand this product we need to get a little technical...



Elemental sulphur, which is essentially 100% sulphur (S), is mostly produced as a by-product of petroleum manufacture.

In terms of what's available here in Australia:



Yates sell 'Liquid Sulfur' Soil Acidifier. It's basically 50% elemental-S.

Being in liquid form means there is no dust to contend with.

This is important because elemental-S is unpleasant stuff to handle.

A good option for the home gardener.



I found some available on Ebay and it was marketed as being "ultra high surface area"

This means it is extremely fine particle sizing, which is a pre-requisite for good performance.

The acidifying effect from elemental sulphur only occurs after specialised Thiobacillus soil bacteria convert the elemental form of sulphur to a sulphate form in the soil.

And the rate of conversion is directly proportional to the surface area of the product ie; the finer the product the greater the surface area.

But be aware:

As previously stated if the particle sizing is fine this can be unpleasant stuff to work with. IF you are considering using this fine particle sulphur we strongly recommend wearing PPE, especially eye, nose and mouth protection.


Searles market 'Sulphur Powder' which is also effectively pure elemental sulphur @99.9%.

Interestingly, as opposed to being a petroleum by-product, the Searles product is mined. 

Technically, being naturally sourced, this means their product is a permitted material for fertilising and soil conditioning under the National Standard For Organic & Bio-dynamic Produce.



Personally, I would avoid the granular 100% sulphur's that I also saw advertised on Ebay.

Feel free to check for yourself but I would suggest they are probably way too big a granule size to be effective ie; insufficient surface area

You could consider using (especially if you have large areas to treat) prilled sulphur that is 90% S and 10% bentonite clay.

Very low dust content and easy to apply but can be harder to source.

Plus, whenever we have sourced this product ourselves, we could only do so in larger 25kg bags which is probably a little bit of overkill for the average garden!


ONE FINAL NOTE (sorry, two final notes. No, three!)

Firstly, with elemental sulphur the soil bacteria that convert it to the sulphate form shut up shop as the soil temperature cools going into winter.

Below 5C or 'biological zero' they pretty much just hibernate. So elemental-S in winter applications, even though the product won't leach, won't have any major effect until soil temps start to rise again in spring.

And second, irrespective of whether you are seeking to raise or lower your soil's pH or just want to maintain it make sure you pH test your soil reasonably regularly, perhaps quarterly, to detect any trends over time (generally, the trend will be downward)

And also (last point, I promise).

Even lab pH tests have a margin for error (+/- 15%) so if you are comparing results over time, allow for this and look for the trend rather than considering the results 100% accurate.


Back to the top