March 9, 2025 • 11 mins
Healthy soil isn’t just dirt—it’s a living, breathing system that relies on air pockets, bacteria, and delicate chemical balances to function properly. In this episode of Where Inches Matter, Allan Piercy breaks down the unseen physics behind soil structure in simple terms, explaining why good soil should be like a well-built card house, full of space for oxygen, water, and thriving microbes.
Allan explores how fertilisers and agrochemicals—many of which are salts—can disrupt this natural balance, causing soil particles to collapse and limiting the availability of essential nutrients. He also demystifies electrical conductivity (EC), a crucial but often overlooked measure of soil health. Using relatable analogies, he explains how EC determines plant growth, why spring brings a natural nutrient boost, and how compacted soils struggle to support crops without costly inputs.
If you’ve ever wondered why some soils naturally sustain plant growth while others require constant fertilisation, this episode will give you the answers. Tune in to learn how to restore your soil’s natural ability to support healthy pastures and crops—without breaking the bank.
🔎 Want to learn more? Visit www.agraforum.co.nz for details on soil testing, fertiliser strategies, and proven methods to improve soil structure and animal health.
See omnystudio.com/listener for privacy information.
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
S1 (00:00):
G'day and welcome to our new podcast that we're calling
Where Inches Matter? And it's probably not what you're thinking.
The inches I'm talking about is the depth. The oxygen
goes down into your soil where it's nice and loose
and holds on to water. So the inches I'm talking about.
Welcome back to this latest podcast of where inches matter.
(00:21):
I'm Ellen Pearce from Agora Forum. In this podcast I'd
like to try and let you understand what good soil
should be and what it should look like. Basically, you've
got to think about this thing or soil structure in
terms of physics, like positives and negatives. So basically most
soils are not sand, but most soils are made of, um,
soil clay, soil colloids made of aluminium and silicon. They
(00:44):
think of them like a dinner plate. If the ratio
of cations around the edge of the dinner plate are correct,
you should have a really strong negative charge on that edge.
And if that's the case, you'll have a strong positive
charge on the flat. And as you know, positives repel
each other and negatives repel each other. So you've got
the edges of the plates trying to push the edge
(01:05):
of another plate away, and you've got the flats of
plates trying to push the other flat away because it's positive.
And then you have positives joining to negatives. So you
think of a card house. The plates are joined flat
to the edge to the flat to the edge. So
you've got a card house type set up. And those
spaces between contain oxygen and you've got bacteria and can
(01:29):
operate in there. Now this should be I don't know
what the number is, but maybe a million of those
all joined like that. And the card house structure, that's
a soil aggregate. And it might be very big. It
might be the size of a match head or something.
But inside that match there's heaps of air. But then
if you imagine those match heads, think of them like
(01:49):
tennis balls or cricket balls, all associated with each other.
But like, if they're in a bag, there's a lot
of air between those balls. Now there's more air spaces.
That's where you've got your water holding capacity of your soil,
you've got where more bacteria can live. It's where the
fungi operate and the feeder roots of the plant. Most importantly,
(02:10):
grow into those spaces and associate with the fungi and
the bacteria. And that's how it's all supposed to work. Now,
if you take away those charges, your card house collapses.
You've got a pile of cards on the table. So
that's been the problem. Prior to the well, after the
Second World War, they had all the spare urea and
(02:31):
people noticed it grew grass around the edge of the pile.
So they figured it was a good idea to grow grass,
which it does because it creates a whole lot of
electrical conductivity. But that should be getting made freely in
the soil. And when they first started using it, it
probably was quite amazing. But because it's a salt and
lots of things since that we've used as fertilizers or
as chemicals, agrochemicals like RPA is not a salt, it's
(02:55):
electrically happy. Lime is not a salt, it's electrically satisfied.
But most of the fertilizers we've been using for the
last 60 years assaults. So that's super super phosphate DAP
crop 20. But then all the other a lot of
other things are salts like round ups of salt. Um,
all your fungicides and pesticides are salts. It's how they work.
(03:19):
They are deliberately salts because they bind with something and
either starve the insect or starve the plant of something,
or starve the fungi of something, so it dies. So
that's how they operate. But the problem is you're obviously
putting them on the soil as well. When you're spraying
for your thistles or whatever it is you're doing. And
when you stick a salt with charges on it into
a nicely flocculated soil structure, it's going to grab some
(03:42):
of those positives and some of those negatives and neutralize
them basically. And so that's why your card house starts
to collapse. And once that happens you're in the poo.
Because most of the bacteria that you want to be
operating in the soil and the fungi, they breathe oxygen
just like us. And if they can't breathe, they're not
going to do much. And so then you've got all
(04:04):
this fertility that you might find on a soil test.
But if you've got no air around your soil, colloids,
the bacteria can't access that fertility and turn it into
a form like phosphorus. They'll turn it into phosphate, which
is just phosphorus joined to some oxygen. And that'll have
a charge and it'll shoot up, up the plant. And
(04:26):
phosphates available or phosphorus is available. And the same with
all the elements potassium nitrate a whole lot all joined
to oxygen. So if you haven't got oxygen, you can't
get access to the fertility or the elements in your soil.
And so what we've finished up doing is buying it
in a sack and putting it on. But in actual fact,
a lot of soils, particularly in the North Island, have
(04:48):
got heaps of fertility because they've got a lot of
volcanic ash in there, which has caught a lot of
the soluble phosphate and sulphur or sulphate particularly, that wasn't
used in the South Island. It's leached and it's finished
up in the rivers and out to sea. But in
the North Island. These guys I know up there, that
won't have to put any phosphorus on if they get
their soil structure right for at least 200 years, probably longer.
(05:12):
A healthy flocculated soil. And by flocculated I mean, uh,
soil that's made up of aggregates, which are made up
of clay colloids which are joined so that these spaces
of air between them and then the aggregates are like
the cricket balls. I was saying again, except the cricket
balls is full of air, because you've got that card
house structure that's flocculated soil, so it's got plenty of
(05:34):
air in it and plenty of water holding capacity so
that your plants can get CO2 out of the atmosphere
and the soil and also water and photosynthesize. There's another
thing that you need to know about. If you're a
hydroponics guy, you live and die by what they call
electrical conductivity. So it's actual electricity that they measure. And
(05:57):
so when they poke their water containing salts to create
a certain level of electrical conductivity for their the tomatoes
or strawberries or whatever they're doing. Growing sucks their nutrients
out to grow in a hydroponic situation. They measure the
EC going in and the EC of that water going out,
and they know how much the plants use, and they
keep it at certain levels in in the soil. It's
(06:19):
exactly the same in the soil to get vegetative growth,
like for growing pasture or before wheat gets to flag
leaf and things. You want to ec of the soil
of around three 350 micro-siemens. Now ideally when that wheat
goes past flag leaf and it's got some fruit to fill,
(06:41):
or trees falling apples or whatever, they like to have
EC closer to 700, they'll still grow fruit, but not
as well if it if it's much below that, and
if it gets too low, if it gets down below 150,
odd things will stop growing vegetatively. But also, when you're
filling seed like wheat in it, you'll get pinch seed.
(07:01):
And if it gets low enough, if it's a fruit tree,
it'll just drop the fruit off the tree. That's what's
happening in Florida with the with that greening. So this
electrical conductivity in the soil, you can create it artificially
with salts, which is what we do with urea and
all those other salts. We make electrical conductivity in the soil,
the fertility, you know, the fruit that you're putting on
(07:22):
a lot of it's not actually the element that you're
putting on. It's the EQ you're creating in a vacuum.
Because if your soil is compacted, you don't have much EQ,
and the reason for that is the electrical conductivity in
the soil should be coming from bacteria. Now, bacteria, when
it's cold, like in the winter, especially down south here,
(07:42):
they don't do anything. They just they're sleeping. Basically, they've
laid spores and they just sit there. When the ground
temperature warms up, they start hatching and they breed like crazy,
but they don't live long. And when they die, they
split open and release. I suppose you'd call them natural salts,
and that creates electrical conductivity, if you want to know
(08:03):
what I mean. If you could find electrical Electrical conductivity
meter somewhere, and you got some water out of the
cowshed or somewhere that there's clean water anyway. And then
you put an EQ meter and it probably measures 20
or 30 or something, but then you get a pinch
of salt, just normal table salt, and put it in
and see what happens. That's that's what I'm talking about.
(08:24):
That's the electrical conductivity. Plants want at least 150 micro-siemens
ideally more than that to grow. So anyway, when these
bacteria die they release salts. So when they're breeding faster
or coming out of the winter, there's more and more
of them being born. There's more and more of them dying.
That's why your EQ comes up. That's where your spring
growth comes from. And that's what they used to call
(08:45):
the spring flush, because associated with that spring flush. Apart
from the EQ coming up, there was also a big
store of ammonium nitrate sitting there. And that's because in
the soil you've got bacteria and they've got a carbon
to nitrogen ratio of ten carbons to one nitrogen. And
when they die, the bodies or the skins of the
(09:06):
dead bacteria get eaten by protozoa and bigger bugs in
the soil, but they've got a carbon to nitrogen ratio
of 1 to 100. So when they have a big
feed of dead bugs, they've got way too much nitrogen
in their body, so they pull it out in the
form of ammonium nitrate. And then the bigger critters that
eat the protozoa have got an even higher carbon to
(09:29):
nitrogen ratio, and they also poo out the excess nitrogen
in the form of ammonium nitrate. Now ammonium nitrate doesn't leach.
And it also turns out it acts like the gas
in your fridge. So it buffers soil temperature. So if
you've got a lot of ammonium nitrate, your soil doesn't
get as hot in the in the heat of the
summer or as cold in the winter. Or basically your
(09:51):
springs come earlier and your autumns last later. So you've
got a longer growing period. But that spring flush was
it's warms up. The bug start breeding like crazy. They
die because they don't live long. And you had a
store of ammonium nitrate sitting there because you could have
ammonium nitrate sitting there. But if your AC is too low,
it's way below 150. The plant's not going to grow,
(10:13):
but when it decides to grow, bingo, it's all there.
But if none of that happens, if your soils compacted,
you've got no bugs dying or bugger all. So you've
got no natural EQ, and you haven't got this big
build up of ammonium nitrate. That's happened because there's hardly
any bugs being born and dying anyway, because there's no
air for them to breathe. So that's why the soil
(10:34):
structure and having air in it is so critical. Otherwise,
you're going to be paying through the nose to grow
whatever it is you're trying to grow. Okay, thanks for listening.
In the next episode, I'm going to talk to you
about soil testing and how to navigate what you should
get tested and who you're listening to, because that's, um,
very important. There's a lot of money wasted, and I
don't want you wasting any money. See you next week.
G'day and welcome to our new podcast that we're calling
Where Inches Matter? And it's probably not what you're thinking.
The inches I'm talking about is the depth. The oxygen
goes down into your soil where it's nice and loose
and holds on to water. So the inches I'm talking about.
Welcome back to this latest podcast of where inches matter.
(00:21):
I'm Ellen Pearce from Agora Forum. In this podcast I'd
like to try and let you understand what good soil
should be and what it should look like. Basically, you've
got to think about this thing or soil structure in
terms of physics, like positives and negatives. So basically most
soils are not sand, but most soils are made of, um,
soil clay, soil colloids made of aluminium and silicon. They
(00:44):
think of them like a dinner plate. If the ratio
of cations around the edge of the dinner plate are correct,
you should have a really strong negative charge on that edge.
And if that's the case, you'll have a strong positive
charge on the flat. And as you know, positives repel
each other and negatives repel each other. So you've got
the edges of the plates trying to push the edge
(01:05):
of another plate away, and you've got the flats of
plates trying to push the other flat away because it's positive.
And then you have positives joining to negatives. So you
think of a card house. The plates are joined flat
to the edge to the flat to the edge. So
you've got a card house type set up. And those
spaces between contain oxygen and you've got bacteria and can
(01:29):
operate in there. Now this should be I don't know
what the number is, but maybe a million of those
all joined like that. And the card house structure, that's
a soil aggregate. And it might be very big. It
might be the size of a match head or something.
But inside that match there's heaps of air. But then
if you imagine those match heads, think of them like
(01:49):
tennis balls or cricket balls, all associated with each other.
But like, if they're in a bag, there's a lot
of air between those balls. Now there's more air spaces.
That's where you've got your water holding capacity of your soil,
you've got where more bacteria can live. It's where the
fungi operate and the feeder roots of the plant. Most importantly,
(02:10):
grow into those spaces and associate with the fungi and
the bacteria. And that's how it's all supposed to work. Now,
if you take away those charges, your card house collapses.
You've got a pile of cards on the table. So
that's been the problem. Prior to the well, after the
Second World War, they had all the spare urea and
(02:31):
people noticed it grew grass around the edge of the pile.
So they figured it was a good idea to grow grass,
which it does because it creates a whole lot of
electrical conductivity. But that should be getting made freely in
the soil. And when they first started using it, it
probably was quite amazing. But because it's a salt and
lots of things since that we've used as fertilizers or
as chemicals, agrochemicals like RPA is not a salt, it's
(02:55):
electrically happy. Lime is not a salt, it's electrically satisfied.
But most of the fertilizers we've been using for the
last 60 years assaults. So that's super super phosphate DAP
crop 20. But then all the other a lot of
other things are salts like round ups of salt. Um,
all your fungicides and pesticides are salts. It's how they work.
(03:19):
They are deliberately salts because they bind with something and
either starve the insect or starve the plant of something,
or starve the fungi of something, so it dies. So
that's how they operate. But the problem is you're obviously
putting them on the soil as well. When you're spraying
for your thistles or whatever it is you're doing. And
when you stick a salt with charges on it into
a nicely flocculated soil structure, it's going to grab some
(03:42):
of those positives and some of those negatives and neutralize
them basically. And so that's why your card house starts
to collapse. And once that happens you're in the poo.
Because most of the bacteria that you want to be
operating in the soil and the fungi, they breathe oxygen
just like us. And if they can't breathe, they're not
going to do much. And so then you've got all
(04:04):
this fertility that you might find on a soil test.
But if you've got no air around your soil, colloids,
the bacteria can't access that fertility and turn it into
a form like phosphorus. They'll turn it into phosphate, which
is just phosphorus joined to some oxygen. And that'll have
a charge and it'll shoot up, up the plant. And
(04:26):
phosphates available or phosphorus is available. And the same with
all the elements potassium nitrate a whole lot all joined
to oxygen. So if you haven't got oxygen, you can't
get access to the fertility or the elements in your soil.
And so what we've finished up doing is buying it
in a sack and putting it on. But in actual fact,
a lot of soils, particularly in the North Island, have
(04:48):
got heaps of fertility because they've got a lot of
volcanic ash in there, which has caught a lot of
the soluble phosphate and sulphur or sulphate particularly, that wasn't
used in the South Island. It's leached and it's finished
up in the rivers and out to sea. But in
the North Island. These guys I know up there, that
won't have to put any phosphorus on if they get
their soil structure right for at least 200 years, probably longer.
(05:12):
A healthy flocculated soil. And by flocculated I mean, uh,
soil that's made up of aggregates, which are made up
of clay colloids which are joined so that these spaces
of air between them and then the aggregates are like
the cricket balls. I was saying again, except the cricket
balls is full of air, because you've got that card
house structure that's flocculated soil, so it's got plenty of
(05:34):
air in it and plenty of water holding capacity so
that your plants can get CO2 out of the atmosphere
and the soil and also water and photosynthesize. There's another
thing that you need to know about. If you're a
hydroponics guy, you live and die by what they call
electrical conductivity. So it's actual electricity that they measure. And
(05:57):
so when they poke their water containing salts to create
a certain level of electrical conductivity for their the tomatoes
or strawberries or whatever they're doing. Growing sucks their nutrients
out to grow in a hydroponic situation. They measure the
EC going in and the EC of that water going out,
and they know how much the plants use, and they
keep it at certain levels in in the soil. It's
(06:19):
exactly the same in the soil to get vegetative growth,
like for growing pasture or before wheat gets to flag
leaf and things. You want to ec of the soil
of around three 350 micro-siemens. Now ideally when that wheat
goes past flag leaf and it's got some fruit to fill,
(06:41):
or trees falling apples or whatever, they like to have
EC closer to 700, they'll still grow fruit, but not
as well if it if it's much below that, and
if it gets too low, if it gets down below 150,
odd things will stop growing vegetatively. But also, when you're
filling seed like wheat in it, you'll get pinch seed.
(07:01):
And if it gets low enough, if it's a fruit tree,
it'll just drop the fruit off the tree. That's what's
happening in Florida with the with that greening. So this
electrical conductivity in the soil, you can create it artificially
with salts, which is what we do with urea and
all those other salts. We make electrical conductivity in the soil,
the fertility, you know, the fruit that you're putting on
(07:22):
a lot of it's not actually the element that you're
putting on. It's the EQ you're creating in a vacuum.
Because if your soil is compacted, you don't have much EQ,
and the reason for that is the electrical conductivity in
the soil should be coming from bacteria. Now, bacteria, when
it's cold, like in the winter, especially down south here,
(07:42):
they don't do anything. They just they're sleeping. Basically, they've
laid spores and they just sit there. When the ground
temperature warms up, they start hatching and they breed like crazy,
but they don't live long. And when they die, they
split open and release. I suppose you'd call them natural salts,
and that creates electrical conductivity, if you want to know
(08:03):
what I mean. If you could find electrical Electrical conductivity
meter somewhere, and you got some water out of the
cowshed or somewhere that there's clean water anyway. And then
you put an EQ meter and it probably measures 20
or 30 or something, but then you get a pinch
of salt, just normal table salt, and put it in
and see what happens. That's that's what I'm talking about.
(08:24):
That's the electrical conductivity. Plants want at least 150 micro-siemens
ideally more than that to grow. So anyway, when these
bacteria die they release salts. So when they're breeding faster
or coming out of the winter, there's more and more
of them being born. There's more and more of them dying.
That's why your EQ comes up. That's where your spring
growth comes from. And that's what they used to call
(08:45):
the spring flush, because associated with that spring flush. Apart
from the EQ coming up, there was also a big
store of ammonium nitrate sitting there. And that's because in
the soil you've got bacteria and they've got a carbon
to nitrogen ratio of ten carbons to one nitrogen. And
when they die, the bodies or the skins of the
(09:06):
dead bacteria get eaten by protozoa and bigger bugs in
the soil, but they've got a carbon to nitrogen ratio
of 1 to 100. So when they have a big
feed of dead bugs, they've got way too much nitrogen
in their body, so they pull it out in the
form of ammonium nitrate. And then the bigger critters that
eat the protozoa have got an even higher carbon to
(09:29):
nitrogen ratio, and they also poo out the excess nitrogen
in the form of ammonium nitrate. Now ammonium nitrate doesn't leach.
And it also turns out it acts like the gas
in your fridge. So it buffers soil temperature. So if
you've got a lot of ammonium nitrate, your soil doesn't
get as hot in the in the heat of the
summer or as cold in the winter. Or basically your
(09:51):
springs come earlier and your autumns last later. So you've
got a longer growing period. But that spring flush was
it's warms up. The bug start breeding like crazy. They
die because they don't live long. And you had a
store of ammonium nitrate sitting there because you could have
ammonium nitrate sitting there. But if your AC is too low,
it's way below 150. The plant's not going to grow,
(10:13):
but when it decides to grow, bingo, it's all there.
But if none of that happens, if your soils compacted,
you've got no bugs dying or bugger all. So you've
got no natural EQ, and you haven't got this big
build up of ammonium nitrate. That's happened because there's hardly
any bugs being born and dying anyway, because there's no
air for them to breathe. So that's why the soil
(10:34):
structure and having air in it is so critical. Otherwise,
you're going to be paying through the nose to grow
whatever it is you're trying to grow. Okay, thanks for listening.
In the next episode, I'm going to talk to you
about soil testing and how to navigate what you should
get tested and who you're listening to, because that's, um,
very important. There's a lot of money wasted, and I
don't want you wasting any money. See you next week.
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