December 10, 2025 • 11 mins
We dig into why low (acidic) soil pH unlocks aluminum toxicity, how that halts root growth, and which crops suffer first. Then we lay out a practical plan to find acidic patches with smarter sampling, NDVI, and grid-the-zone strategies, and point to lime and buffer pH for the fix.
In this episode, we discuss...
• soil pH as chemical control and pH level of 7 is neutral
• aluminum toxicity risk to crops increases below 6.5 pH
• wheat relatively tolerant, legumes struggle with nodulation
• stunted roots and thin stands on slopes and sandier spots
• acidic areas are patchy and do not always follow productivity maps
• importance of using intensive grids and how 0–3 inch sampling in no-till helps detect acidicity issues
• soil testing: pair pH with buffer pH to set lime rates
• target NDVI-low areas and grid inside zones
• variable-rate lime as the remediation path
Gridding the Zone with Ag Genesis Part 1: https://www.buzzsprout.com/2297340/episodes/16692855
Gridding the Zone with Ag Gensis Part 2:
https://www.buzzsprout.com/2297340/episodes/16692855
Tune in next time for a Tiny Byte of knowledge from GK Technology, where we have a map and an app for that.
https://gktechinc.com/
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Sarah (00:00):
And now it's time for a Tiny Byte of knowledge.
So, Jodi, what is the big dealwith low soil pH?
I mean, I hear people talkinglike down in Iowa, man, my pH is
(00:22):
low and I got a lime.
What in the heck is going on?
Help me understand.
Jodi (00:28):
That's a fantastic question.
And it's a question we'regetting more and more often up
here in the northern GreatPlains and also the prairie
provinces.
So stepping back for a second,thinking about soil pH itself,
it's basically the chemicalcontrol of our soil.
So when we think about pH, it'simportant to remember that like
(00:48):
seven is our baseline, that'sour neutral point.
And that's everything's kind ofquote unquote normal.
And then as we swing to higherpHs, which we can sometimes see
in soil here in the valley, wecan see them 8.2 to 8.3 is
pretty common.
Can get higher in the 8.5s.
But we can also, when you kindof start to get sandier stuff,
you can see pHs down to 6.5, 6,5.5.
(01:12):
Numbers above seven are goingto be basic, and then pHs below
seven are going to be consideredacidic.
And so what that's telling us,or what these numbers mean, or
really on a practical level, isthat they're controlling what in
the soil is soluble andavailable for the plants to take
up.
So for those of you that haveseen charts that show like the
(01:32):
pH chart and they've gotdifferent colors and they show
the pH range from, you know,zero to seven and seven to
fourteen, and you've got thesestripes that kind of go in and
out based on the number and howeach of those nutrients are,
those essential crop andnutrients are available based on
pH.
That's what we're talking abouthere.
As you get to lower pHs, somesoil elements or some nutrients
(01:57):
in the soil become way moreavailable than they are at a
normal pH of like seven.
And then some nutrients becomemore tied up or no longer
soluble and no longer presentfor plants to take up at these
lower pHs.
And so, long story short, whenwe get to pHs that are below
6.5, we start to worry aboutaluminum toxicity.
(02:19):
And this isn't because, youknow, the pH is introducing new
aluminum.
There's not aluminum fallingfrom the sky.
What's happening is that thataluminum that was tightly bound
and not available for the plantto take up now is available in
the soil solution for our plantsto take up.
And unfortunately, a lot of thecrops that we grow up here in
North Dakota don't likealuminum.
(02:40):
They are not happy when they'reinteracting with that aluminum.
And so we we run into aluminumtoxicity.
Some crops are better attolerating this than others.
Um, for example, wheat, smallgrains are going to be more on
the tolerant side.
Any sort of legume below 6.5,we start to worry about pH is
below 6.5, it's harder forbacteria to grow.
(03:02):
So when we think about likelegumes and nodulation, below
6.5, that process becomes very,very low.
And so we're starting to seereduced crop growth, reduced
nodulation.
Our crops just can't compete aswell when they are affected by
that aluminum in the soil.
So, like overall, the numberone concern with low pHs is that
(03:23):
most of our crops are nottolerant to really low pHs.
So 6.5, you might not seeanything right away, but as we
creep down into 6, 5.5, 5, 4.5,we're gonna see that the roots
are going to start and explorein the soil, but then they just
stop.
Uh, they can't, our plantscan't put on root systems
(03:43):
because they can't grow in thepresence of that aluminum.
Sarah (03:46):
That's such a great explanation about how aluminum
becomes more available, um, moreit's more soluble and made more
available for plant takeout.
And it's just so prevalent inthe soil that the plants take it
up readily.
And it's interesting when youtake a look at at roots that are
affected by aluminum toxicity,they almost look like there's
(04:08):
they reach this layer and theyjust become like these wimpy
little things.
I mean, you see a definite linewhere um above that maybe
there's not quite as muchaluminum available and the root
looks normal.
And then below that, um thatthat root looks just wimpy and
(04:29):
and like it can't do anything.
And guess what?
It's not, and and your plantslook terrible on the top as
well.
And it's interesting becauseyou mentioned that wheat is is
fairly tolerant, and it is, butat a certain point in time, not
even the small grains can keepup.
And we are seeing that inwestern North Dakota all the
(04:50):
time.
We've got had a chance to seefrom some of our friends out
west some really interestingpictures of landscapes out there
where you can clearly see wherethe small grain looks good and
it's healthy, and then you cansee the side hills or the top of
the hills that are greatlyaffected by that aluminum
toxicity, and the plants justlook terrible.
(05:12):
You can see right down to thesoil in between the rows of that
small grain in those scenarioswhere it's being affected by
that low pH.
So it's very interesting.
So, what is the best way for usto identify where these spots
are?
And I think this is incrediblyimportant for us because this
(05:34):
soil pH issue is a perfect issueto try to address with
precision agriculture.
So, how do we figure out wherethese places are occurring in
the field?
Jodi (05:44):
Yeah, absolutely.
So, really the best way toidentify them, unfortunately,
because it's not gonna be, it'snot easy, is what I'm gonna say.
There's no easy button to veryquickly figure out exactly where
the soil pHs are.
What we're finding as more andmore people, at least in like
Western North Dakota, are soilsampling for specifically for pH
(06:07):
and for pH management andacidic soil management, what
we're finding is that theseareas that are low are pretty
spotty and they don't alwaysfollow our productivity maps.
In the like in the corn belt,they've been dealing with these
acidic soils and managing themfor the last hundred years.
And it's even where the gridconcept and grid soil sampling
(06:28):
concept comes from is figuringout, you know, how can we make
be more efficient in our Lymeapplications?
And so in general, the best wayto go out and soil sample and
find and identify these spots isgoing to be through, you know,
pretty intensive soil samplingsetup, one acre grids, two and a
half acre grids, and thensampling at least a zero to six.
(06:50):
And I'd say if you're in ano-till system where you're
gonna have more acidity on thetop, zero to three inches, than
the bottom three to six inches,you may even want to consider
doing a zero to three inchsample just to identify how low
that pH is, where the seed isplaced, because I think it
surprises people more when we'vegot no-till.
(07:11):
It's worse than people think.
I'll just leave it there.
But that's gonna be the biggestthing.
And identifying it, you'regoing to sample it for pH.
And then if you have a pH thatis below 6.5, you'll want to run
a buffer pH, which is the soiltest result that is going to
tell you how much Lyme to apply.
So you need to have both a pHnumber and a buffer pH number to
(07:33):
diagnose and then determine howmuch Lyme you should apply in
order to increase your pH.
And we haven't even touchedthat, Sarah.
We haven't even talked aboutwhat to do when we have these
pH, these little pH areas, butit comes down to Lyme.
Sarah (07:47):
We could talk about that in another tiny bite.
But one thing I want to um makecertain when we're trying to
identify where these spots are,like Jodi said, some of these
aren't always related toproductivity areas.
Many times when we were makingzones for zone soil sampling,
those zones are driven off ofproductivity data.
And so they may or may not bethe best identifier of where we
(08:11):
actually need to be applyinglime to remediate these areas.
But one thing that you can dois if you figure out areas in a
field that have less plantgrowth.
For example, I was talkingabout those fields in western
North Dakota earlier, where youcan clearly see that the plant
growth is diminished.
You can use NDVI data toidentify where those spots are
(08:35):
occurring.
And then once you might havethat laid out in a zone, grid
that zone.
Go out and do that intensivesoil sampling on a grid, but
just within that zone.
That's a really important thingto think about because
especially when we're dealingwith areas of the United States
where we've got such largeacreage fields, you know, some
(08:57):
of those fields out west are1200 acres in size.
Are you seriously going to gridsample that on a one-acre grid?
Ufda made of that's intense.
And so trying to do that in ascenario where maybe we can grid
a zone or identify those spotswhere we need more of that
intensive sampling, that couldbe a very good option for us.
Jodi (09:20):
Yes.
And do take a listen.
We've got an episode where wetalked to Lane Bothwell and Kurt
Turner.
Kurt Turner, down withAg Genesis, South Dakota, where
they are gridding their zonesamples or gridding their zones
to identify and makeprescriptions for variable rate
Lyme.
And they are truly gritting thezone.
(09:42):
And you can listen back to thatepisode for more tips on how to
do that and how to make thatwork.
Sarah (09:46):
And I think we had another tiny bite about what
Lyme is, right?
Jodi (09:51):
Yes.
So when I say lime or calciumcarbonate, if you want to know
more, check back to our othertiny bites to hear more on that.
Because we don't want me on mysoapbox to talk about it some
more, because this will getlong.
Um but in short, what low whatacidic soils are, they are soils
that have low pHs.
(10:12):
Anything below seven isconsidered acidic, but we're
talking soils of 6.5 pH orlower.
And the problem with thesefields is that they're prone to
aluminum toxicity.
So get out there.
There is a solution.
Sarah (10:26):
Get them identified and get them taken care of.
Jodi (10:29):
Woo! Tune in next time for a tiny bite of knowledge from
GK Technology, where we have amap and an app for that.
And now it's time for a Tiny Byte of knowledge.
So, Jodi, what is the big dealwith low soil pH?
I mean, I hear people talkinglike down in Iowa, man, my pH is
(00:22):
low and I got a lime.
What in the heck is going on?
Help me understand.
Jodi (00:28):
That's a fantastic question.
And it's a question we'regetting more and more often up
here in the northern GreatPlains and also the prairie
provinces.
So stepping back for a second,thinking about soil pH itself,
it's basically the chemicalcontrol of our soil.
So when we think about pH, it'simportant to remember that like
(00:48):
seven is our baseline, that'sour neutral point.
And that's everything's kind ofquote unquote normal.
And then as we swing to higherpHs, which we can sometimes see
in soil here in the valley, wecan see them 8.2 to 8.3 is
pretty common.
Can get higher in the 8.5s.
But we can also, when you kindof start to get sandier stuff,
you can see pHs down to 6.5, 6,5.5.
(01:12):
Numbers above seven are goingto be basic, and then pHs below
seven are going to be consideredacidic.
And so what that's telling us,or what these numbers mean, or
really on a practical level, isthat they're controlling what in
the soil is soluble andavailable for the plants to take
up.
So for those of you that haveseen charts that show like the
(01:32):
pH chart and they've gotdifferent colors and they show
the pH range from, you know,zero to seven and seven to
fourteen, and you've got thesestripes that kind of go in and
out based on the number and howeach of those nutrients are,
those essential crop andnutrients are available based on
pH.
That's what we're talking abouthere.
As you get to lower pHs, somesoil elements or some nutrients
(01:57):
in the soil become way moreavailable than they are at a
normal pH of like seven.
And then some nutrients becomemore tied up or no longer
soluble and no longer presentfor plants to take up at these
lower pHs.
And so, long story short, whenwe get to pHs that are below
6.5, we start to worry aboutaluminum toxicity.
(02:19):
And this isn't because, youknow, the pH is introducing new
aluminum.
There's not aluminum fallingfrom the sky.
What's happening is that thataluminum that was tightly bound
and not available for the plantto take up now is available in
the soil solution for our plantsto take up.
And unfortunately, a lot of thecrops that we grow up here in
North Dakota don't likealuminum.
(02:40):
They are not happy when they'reinteracting with that aluminum.
And so we we run into aluminumtoxicity.
Some crops are better attolerating this than others.
Um, for example, wheat, smallgrains are going to be more on
the tolerant side.
Any sort of legume below 6.5,we start to worry about pH is
below 6.5, it's harder forbacteria to grow.
(03:02):
So when we think about likelegumes and nodulation, below
6.5, that process becomes very,very low.
And so we're starting to seereduced crop growth, reduced
nodulation.
Our crops just can't compete aswell when they are affected by
that aluminum in the soil.
So, like overall, the numberone concern with low pHs is that
(03:23):
most of our crops are nottolerant to really low pHs.
So 6.5, you might not seeanything right away, but as we
creep down into 6, 5.5, 5, 4.5,we're gonna see that the roots
are going to start and explorein the soil, but then they just
stop.
Uh, they can't, our plantscan't put on root systems
(03:43):
because they can't grow in thepresence of that aluminum.
Sarah (03:46):
That's such a great explanation about how aluminum
becomes more available, um, moreit's more soluble and made more
available for plant takeout.
And it's just so prevalent inthe soil that the plants take it
up readily.
And it's interesting when youtake a look at at roots that are
affected by aluminum toxicity,they almost look like there's
(04:08):
they reach this layer and theyjust become like these wimpy
little things.
I mean, you see a definite linewhere um above that maybe
there's not quite as muchaluminum available and the root
looks normal.
And then below that, um thatthat root looks just wimpy and
(04:29):
and like it can't do anything.
And guess what?
It's not, and and your plantslook terrible on the top as
well.
And it's interesting becauseyou mentioned that wheat is is
fairly tolerant, and it is, butat a certain point in time, not
even the small grains can keepup.
And we are seeing that inwestern North Dakota all the
(04:50):
time.
We've got had a chance to seefrom some of our friends out
west some really interestingpictures of landscapes out there
where you can clearly see wherethe small grain looks good and
it's healthy, and then you cansee the side hills or the top of
the hills that are greatlyaffected by that aluminum
toxicity, and the plants justlook terrible.
(05:12):
You can see right down to thesoil in between the rows of that
small grain in those scenarioswhere it's being affected by
that low pH.
So it's very interesting.
So, what is the best way for usto identify where these spots
are?
And I think this is incrediblyimportant for us because this
(05:34):
soil pH issue is a perfect issueto try to address with
precision agriculture.
So, how do we figure out wherethese places are occurring in
the field?
Jodi (05:44):
Yeah, absolutely.
So, really the best way toidentify them, unfortunately,
because it's not gonna be, it'snot easy, is what I'm gonna say.
There's no easy button to veryquickly figure out exactly where
the soil pHs are.
What we're finding as more andmore people, at least in like
Western North Dakota, are soilsampling for specifically for pH
(06:07):
and for pH management andacidic soil management, what
we're finding is that theseareas that are low are pretty
spotty and they don't alwaysfollow our productivity maps.
In the like in the corn belt,they've been dealing with these
acidic soils and managing themfor the last hundred years.
And it's even where the gridconcept and grid soil sampling
(06:28):
concept comes from is figuringout, you know, how can we make
be more efficient in our Lymeapplications?
And so in general, the best wayto go out and soil sample and
find and identify these spots isgoing to be through, you know,
pretty intensive soil samplingsetup, one acre grids, two and a
half acre grids, and thensampling at least a zero to six.
(06:50):
And I'd say if you're in ano-till system where you're
gonna have more acidity on thetop, zero to three inches, than
the bottom three to six inches,you may even want to consider
doing a zero to three inchsample just to identify how low
that pH is, where the seed isplaced, because I think it
surprises people more when we'vegot no-till.
(07:11):
It's worse than people think.
I'll just leave it there.
But that's gonna be the biggestthing.
And identifying it, you'regoing to sample it for pH.
And then if you have a pH thatis below 6.5, you'll want to run
a buffer pH, which is the soiltest result that is going to
tell you how much Lyme to apply.
So you need to have both a pHnumber and a buffer pH number to
(07:33):
diagnose and then determine howmuch Lyme you should apply in
order to increase your pH.
And we haven't even touchedthat, Sarah.
We haven't even talked aboutwhat to do when we have these
pH, these little pH areas, butit comes down to Lyme.
Sarah (07:47):
We could talk about that in another tiny bite.
But one thing I want to um makecertain when we're trying to
identify where these spots are,like Jodi said, some of these
aren't always related toproductivity areas.
Many times when we were makingzones for zone soil sampling,
those zones are driven off ofproductivity data.
And so they may or may not bethe best identifier of where we
(08:11):
actually need to be applyinglime to remediate these areas.
But one thing that you can dois if you figure out areas in a
field that have less plantgrowth.
For example, I was talkingabout those fields in western
North Dakota earlier, where youcan clearly see that the plant
growth is diminished.
You can use NDVI data toidentify where those spots are
(08:35):
occurring.
And then once you might havethat laid out in a zone, grid
that zone.
Go out and do that intensivesoil sampling on a grid, but
just within that zone.
That's a really important thingto think about because
especially when we're dealingwith areas of the United States
where we've got such largeacreage fields, you know, some
(08:57):
of those fields out west are1200 acres in size.
Are you seriously going to gridsample that on a one-acre grid?
Ufda made of that's intense.
And so trying to do that in ascenario where maybe we can grid
a zone or identify those spotswhere we need more of that
intensive sampling, that couldbe a very good option for us.
Jodi (09:20):
Yes.
And do take a listen.
We've got an episode where wetalked to Lane Bothwell and Kurt
Turner.
Kurt Turner, down withAg Genesis, South Dakota, where
they are gridding their zonesamples or gridding their zones
to identify and makeprescriptions for variable rate
Lyme.
And they are truly gritting thezone.
(09:42):
And you can listen back to thatepisode for more tips on how to
do that and how to make thatwork.
Sarah (09:46):
And I think we had another tiny bite about what
Lyme is, right?
Jodi (09:51):
Yes.
So when I say lime or calciumcarbonate, if you want to know
more, check back to our othertiny bites to hear more on that.
Because we don't want me on mysoapbox to talk about it some
more, because this will getlong.
Um but in short, what low whatacidic soils are, they are soils
that have low pHs.
(10:12):
Anything below seven isconsidered acidic, but we're
talking soils of 6.5 pH orlower.
And the problem with thesefields is that they're prone to
aluminum toxicity.
So get out there.
There is a solution.
Sarah (10:26):
Get them identified and get them taken care of.
Jodi (10:29):
Woo! Tune in next time for a tiny bite of knowledge from
GK Technology, where we have amap and an app for that.
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