Episode 9: What Native Plants Reveal About Our Soils with Kingsley Dixon

So the real story about our soils is they're old, they're infertile, and they're very sensitive to change.

We know that only so well.

They over-clear, they turn into dust bowls within a year.

They over-clear, the salinity increases.

You over-clear and you quickly lose your A horizon.

And the A horizon, which is of course the fertile horizon we're all after, is very poorly developed in our soils because nothing needs an A horizon because nothing depends upon it in our system.

Annuals do.

We have very few annual native plants.

So they're telling us these soils are ancient.

You've got to treat them with care.

There's other aspects though that we've also discovered.

Many farmers who might listen to this will know about non-wetting soils, the curse of many areas of the wheat bowl.

Why do we have bushland where there's a banksia tree to my left, one to my right, why aren't there more banksia trees here? We're discovering that it's a natural part of our soils to be non-wetting.

That's how you get gaps and you keep openness in bushland.

We've discovered this through our big program that we're just doing on restoring banksias on large corridors just south of Perth, that we kept digging our holes with our big augers, putting in 50,000 banksias over the last two months.

And in some areas that we were looking at, we were getting nine out of 10 holes, even after something like eight inches of rain, they were bone dry.

which is exactly what farmers go.

And we tried to understand why is that? And then we came and audited the natural bushland.

We found it was about four out of 10 holes were naturally dry, which means they've been naturally dry for a few thousand years.

Now they will wet up well late into spring or, when all the recruitment happens.

But we believe it's an important way that nature takes a little bit of water, it sheds into those little areas where the banks of tree is growing, and it acts almost like putting a roof and catching rainfall.

So we think it's a way with very little rainfall in non-water holding soils that you get what we call water gaining microsites.

So it's a whole new concept that we're investigating.

At the same time, we're investigating the magic of soil wetters.

We're doing the first definitive study of eight products to say because we need to do restoration of post-agricultural land, much of the sandy country that was cleared won't grow a crop.