March 5, 2025 • 9 mins
Awareness of nutrient mobility in plants drastically improves in-field diagnosis of crop issues. In this episode, we dive deep into plant nutrient mobility and how nutrient mobility impacts visual symptoms in the field.
• Discussion on the concept of nutrient mobility
• Insights into mobile vs. immobile nutrient deficiencies
• Importance of tissue testing for accurate diagnoses
Relatively immobile nutrients (symptoms will appear on newest leaf tissue): S, Zn, Fe, Cu, B, Ca, Mn, Mo, Ni
Relatively mobile nutrients (symptoms will appear on oldest leaf tissue): N, P, K, Mg
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Cover art diagram courtesy of the 4R Plant Nutrition Manual, IPNI 2012 (https://www.canr.msu.edu/news/identifying_nutrient_deficiency_symptoms_in_field_crops)
https://gktechinc.com/
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Sarah (00:00):
And now it's time for a tiny bite of knowledge, Jodi.
Why is my corn purple?
I don't know.
Sarah, Did you give enoughfertilizer?
I don't know.
(00:20):
I've just never seen purplecorn before.
Jodi (00:24):
Okay.
So maybe if you've been aroundnutrient deficiencies for a
while, you might think are wedoing a podcast on phosphorus
deficiency, which we typicallyassociate with purple corn?
But what we want to talk abouttoday is the mobility of
nutrients in plants and why wemight see certain nutrient
deficiencies on the upper or theyoung parts of plants or the
(00:45):
lower parts of plants.
Sarah (00:47):
That's absolutely correct If we back up one second.
My professor at NDSU, dr Goose,used to classify nutrients
according to their soil mobilityand their plant mobility.
Today we're talking about plantmobility.
Some nutrients move easier inplants than others and at the
very outset most nutrients aremobile within the plant when
(01:10):
they are not under any stress.
However, once stress occurs ora nutrient is deficient, the
plant automatically wants tosend that nutrient to the
younger tissues and the growingpoints at the top of the plant.
That is its desire.
It's going to try to preservethat area that's actively
growing to the best of itsability.
(01:31):
But some nutrients just don'tmove that easily in the plant,
and so when you see a nutrientdeficiency or discoloration of
leaves on the upper or the lowerpart of the plant, that is
explaining what type of nutrientit is and whether that nutrient
is plant mobile or immobile inthe plant.
Jodi (01:53):
Sarah, what are some of the nutrient deficiencies we
typically expect to show up onthe older part of the plant
instead of the younger part ofthe plant?
Or what are those nutrientsthat are more mobile in the
plant versus non-mobile?
Sarah (02:07):
Yeah, it corrects Nutrients like nitrogen,
phosphorus and potassium.
Those are plant mobilenutrients.
So when those deficienciesstart to occur, what the plant
is going to do is take thosenutrients out of the bottom
leaves and translocate thosenutrients to the top of the
plant where that younger tissueis growing, where that growing
point is actively growing, sothat the plant can really help
(02:30):
keep that growth happening.
So that's why when you see aphosphorus deficiency or a
nitrogen deficiency or potassiumdeficiency, you're going to see
those occurring on the bottompart of the plant first going to
see those occurring on thebottom part of the plant first.
Jodi (02:48):
What nutrients might we expect to be plant immobile or
appearing first in those newparts of the plant, versus the
old Nutrients like iron?
Sarah (02:54):
zinc and sulfur, copper.
Those are all nutrients thatare plant and mobile and around,
especially in the areas whereiron chlorosis occurs.
We see that frequently, thatclassic interveinal chlorosis of
the upper leaves.
Those nutrients they just can'teasily move from the bottom
(03:16):
tissues and translocate it up tothat growing point so that
younger tissue, that growingpoint, can be maintained and
grow successfully.
As a matter of fact, in some ofthe iron chlorosis work that
I've seen locally there'sactually been an effort to
foliar feed iron into the plantwith sprays.
And what would happen when theywould spray is that just where
(03:38):
that spray would hit, the leafwould green up.
However, they would block partof the leaf with a sticky note
and the iron couldn't eventranslocate to the part of the
leaf that didn't actuallydirectly receive the application
because it's just that immobilein the plant.
So if you're trying to diagnosea nutrient deficiency in the
(03:59):
field, first take a look at theplant and see where the
discoloration or the affectedleaves are occurring.
Are they occurring on the upperpart of the plant or the lower
part of the plant?
Sulfur is also an interestingone.
Sulfur actually looks an awfullot like nitrogen.
However, it starts on the upperleaves and the upper tissues.
(04:20):
But once it gets to be sosulfur deficient the whole plant
starts to take to look yellow.
And the way the pattern is forsulfur it's very similar to
nitrogen, especially in wheat.
Oftentimes a sulfur deficiencycan get confused with a nitrogen
deficiency in wheat because itgoes from being those initial
(04:41):
stages of that upper tissueturning yellow to the whole
plant canopy turning yellow soquickly.
So that's a place where if youput nitrogen out there and it
doesn't green up, I would arguethat most of the time if you see
a yellow plant canopy in asmall grain, it's probably
nitrogen deficient.
But if you put nitrogen onthere to remedy it and it
(05:01):
doesn't fix it, it was probablysulfur.
Check it out.
Jodi (05:05):
And this is a really, really good place to plug tissue
testing in terms of its abilityto help diagnose some of these
issues, or say if you're not asfamiliar with diagnosing these
issues in a new crop or you're.
Or say if you're not as familiarwith diagnosing these issues in
a new crop or you're in a newplace and not as familiar with
what the practices are and whatcommonly occurs.
Do take a diagnostic tissuetest and what's important right
(05:28):
is that you follow theinstructions of whatever lab
you're submitting that tissuetest to and you're taking a test
of both a plant that looks likeit has that deficiency and
collect it from an area where itdoes not look like they have a
deficiency or that issue.
That way, you can compare whenyou get the tissue test results
back.
Okay, what are my levels in thearea of the field that I
(05:48):
collected that looked like ithad a deficiency versus where it
wasn't?
Because, yeah, I mean, some ofthese nutrient deficiencies can
look pretty similar, and sohaving a tissue test is a really
good way to diagnose that, geta cook result and help you apply
only what you need.
Sarah (06:03):
Just like Jodi said, you need to take one from the area
that's deficient and you need totake another sample from the
area that is not displayingthose symptoms so you can really
compare those results, becauseit really will help you
understand what that deficiencyis.
You need to be able to comparethose sample results and, of
course, the topic is mobile andimmobile nutrients.
Jodi (06:25):
We haven't even touched on what some of these nutrient
deficiencies can look likeoutside of nutrient deficiency.
So taking a tissue test is agood way to hone in on what
you're looking out anddiagnosing what you got in the
field.
Sarah (06:37):
It's pretty simple when you see something yellow, you
see yellow corn to think rightaway that it's nitrogen.
I have had farmers andagronomists confuse that with
potassium and in my opinion Idon't think those two things
look at all the same, butthey're yellowing of the leaves
on the bottom, so I can see howthat can get mistaken pretty
easily.
Also, note the misapplicationof some herbicides can actually
(06:59):
cause some purpling.
So to verify whether it'sphosphorus or not or something
else, it's always a great ideato start with that phosphorus
tissue test because it's a muchcheaper test to run than an
actual chemical analysis orpesticide analysis an actual
(07:20):
chemical analysis or pesticideanalysis.
Also, keep in mind that when youare taking that tissue sample,
it's really important to takethe right part of the plant that
the instructions say to takefor the stage of the crop that
you are in.
And that all comes back to theplant mobility.
If you're at different stagesin crop growth, those nutrients
are going to be mobilized todifferent areas of the plant.
So that's why you need to bemaking sure that you're at
different stages in crop growth,those nutrients are going to be
mobilized to different areas ofthe plant.
So that's why you need to bemaking sure that you're sampling
(07:42):
the correct part of the plantfor the stage that that crop is
in.
Jodi (07:46):
So, to wrap this all up again, when we're talking about
plant mobile and plant immobilenutrients, when we're talking
about plant mobile, these arenutrients that the plant can
actually remobilize from a lowerpart of the plant and put up to
the top of the plant, and sowe're going to see these
deficiencies in the old leaftissue first.
Those nutrients that are plantimmobile are the ones that the
(08:07):
plant can't remobilize and movesomeplace else.
Sarah, do you want to give us arecap of what our common plant
mobile nutrients are and whatour common plant immobile
nutrients?
Sarah (08:17):
are, Again, our plant mobile nutrients, for the most
common nutrients that we'rehandling are nitrogen,
phosphorus and potassium, andour most common nutrients that
we handle that are immobile andyou will see their deficiencies.
Jodi (08:30):
The immobile nutrients at the top of the plant sulfur,
zinc, iron, copper, boron and,if you don't remember these,
listen back to the podcast, do aquick Google search and that'll
help you a ton when you're outthere trying to diagnose
nutrient deficiencies out in thefield.
Sarah (08:46):
Absolutely, absolutely Purple corn.
Jodi (08:50):
Purple corn, you ready Tune in next time for a tiny
bite of knowledge from GKTechnology where we have a map
and an app for that.
And now it's time for a tiny bite of knowledge, Jodi.
Why is my corn purple?
I don't know.
Sarah, Did you give enoughfertilizer?
I don't know.
(00:20):
I've just never seen purplecorn before.
Jodi (00:24):
Okay.
So maybe if you've been aroundnutrient deficiencies for a
while, you might think are wedoing a podcast on phosphorus
deficiency, which we typicallyassociate with purple corn?
But what we want to talk abouttoday is the mobility of
nutrients in plants and why wemight see certain nutrient
deficiencies on the upper or theyoung parts of plants or the
(00:45):
lower parts of plants.
Sarah (00:47):
That's absolutely correct If we back up one second.
My professor at NDSU, dr Goose,used to classify nutrients
according to their soil mobilityand their plant mobility.
Today we're talking about plantmobility.
Some nutrients move easier inplants than others and at the
very outset most nutrients aremobile within the plant when
(01:10):
they are not under any stress.
However, once stress occurs ora nutrient is deficient, the
plant automatically wants tosend that nutrient to the
younger tissues and the growingpoints at the top of the plant.
That is its desire.
It's going to try to preservethat area that's actively
growing to the best of itsability.
(01:31):
But some nutrients just don'tmove that easily in the plant,
and so when you see a nutrientdeficiency or discoloration of
leaves on the upper or the lowerpart of the plant, that is
explaining what type of nutrientit is and whether that nutrient
is plant mobile or immobile inthe plant.
Jodi (01:53):
Sarah, what are some of the nutrient deficiencies we
typically expect to show up onthe older part of the plant
instead of the younger part ofthe plant?
Or what are those nutrientsthat are more mobile in the
plant versus non-mobile?
Sarah (02:07):
Yeah, it corrects Nutrients like nitrogen,
phosphorus and potassium.
Those are plant mobilenutrients.
So when those deficienciesstart to occur, what the plant
is going to do is take thosenutrients out of the bottom
leaves and translocate thosenutrients to the top of the
plant where that younger tissueis growing, where that growing
point is actively growing, sothat the plant can really help
(02:30):
keep that growth happening.
So that's why when you see aphosphorus deficiency or a
nitrogen deficiency or potassiumdeficiency, you're going to see
those occurring on the bottompart of the plant first going to
see those occurring on thebottom part of the plant first.
Jodi (02:48):
What nutrients might we expect to be plant immobile or
appearing first in those newparts of the plant, versus the
old Nutrients like iron?
Sarah (02:54):
zinc and sulfur, copper.
Those are all nutrients thatare plant and mobile and around,
especially in the areas whereiron chlorosis occurs.
We see that frequently, thatclassic interveinal chlorosis of
the upper leaves.
Those nutrients they just can'teasily move from the bottom
(03:16):
tissues and translocate it up tothat growing point so that
younger tissue, that growingpoint, can be maintained and
grow successfully.
As a matter of fact, in some ofthe iron chlorosis work that
I've seen locally there'sactually been an effort to
foliar feed iron into the plantwith sprays.
And what would happen when theywould spray is that just where
(03:38):
that spray would hit, the leafwould green up.
However, they would block partof the leaf with a sticky note
and the iron couldn't eventranslocate to the part of the
leaf that didn't actuallydirectly receive the application
because it's just that immobilein the plant.
So if you're trying to diagnosea nutrient deficiency in the
(03:59):
field, first take a look at theplant and see where the
discoloration or the affectedleaves are occurring.
Are they occurring on the upperpart of the plant or the lower
part of the plant?
Sulfur is also an interestingone.
Sulfur actually looks an awfullot like nitrogen.
However, it starts on the upperleaves and the upper tissues.
(04:20):
But once it gets to be sosulfur deficient the whole plant
starts to take to look yellow.
And the way the pattern is forsulfur it's very similar to
nitrogen, especially in wheat.
Oftentimes a sulfur deficiencycan get confused with a nitrogen
deficiency in wheat because itgoes from being those initial
(04:41):
stages of that upper tissueturning yellow to the whole
plant canopy turning yellow soquickly.
So that's a place where if youput nitrogen out there and it
doesn't green up, I would arguethat most of the time if you see
a yellow plant canopy in asmall grain, it's probably
nitrogen deficient.
But if you put nitrogen onthere to remedy it and it
(05:01):
doesn't fix it, it was probablysulfur.
Check it out.
Jodi (05:05):
And this is a really, really good place to plug tissue
testing in terms of its abilityto help diagnose some of these
issues, or say if you're not asfamiliar with diagnosing these
issues in a new crop or you're.
Or say if you're not as familiarwith diagnosing these issues in
a new crop or you're in a newplace and not as familiar with
what the practices are and whatcommonly occurs.
Do take a diagnostic tissuetest and what's important right
(05:28):
is that you follow theinstructions of whatever lab
you're submitting that tissuetest to and you're taking a test
of both a plant that looks likeit has that deficiency and
collect it from an area where itdoes not look like they have a
deficiency or that issue.
That way, you can compare whenyou get the tissue test results
back.
Okay, what are my levels in thearea of the field that I
(05:48):
collected that looked like ithad a deficiency versus where it
wasn't?
Because, yeah, I mean, some ofthese nutrient deficiencies can
look pretty similar, and sohaving a tissue test is a really
good way to diagnose that, geta cook result and help you apply
only what you need.
Sarah (06:03):
Just like Jodi said, you need to take one from the area
that's deficient and you need totake another sample from the
area that is not displayingthose symptoms so you can really
compare those results, becauseit really will help you
understand what that deficiencyis.
You need to be able to comparethose sample results and, of
course, the topic is mobile andimmobile nutrients.
Jodi (06:25):
We haven't even touched on what some of these nutrient
deficiencies can look likeoutside of nutrient deficiency.
So taking a tissue test is agood way to hone in on what
you're looking out anddiagnosing what you got in the
field.
Sarah (06:37):
It's pretty simple when you see something yellow, you
see yellow corn to think rightaway that it's nitrogen.
I have had farmers andagronomists confuse that with
potassium and in my opinion Idon't think those two things
look at all the same, butthey're yellowing of the leaves
on the bottom, so I can see howthat can get mistaken pretty
easily.
Also, note the misapplicationof some herbicides can actually
(06:59):
cause some purpling.
So to verify whether it'sphosphorus or not or something
else, it's always a great ideato start with that phosphorus
tissue test because it's a muchcheaper test to run than an
actual chemical analysis orpesticide analysis an actual
(07:20):
chemical analysis or pesticideanalysis.
Also, keep in mind that when youare taking that tissue sample,
it's really important to takethe right part of the plant that
the instructions say to takefor the stage of the crop that
you are in.
And that all comes back to theplant mobility.
If you're at different stagesin crop growth, those nutrients
are going to be mobilized todifferent areas of the plant.
So that's why you need to bemaking sure that you're at
different stages in crop growth,those nutrients are going to be
mobilized to different areas ofthe plant.
So that's why you need to bemaking sure that you're sampling
(07:42):
the correct part of the plantfor the stage that that crop is
in.
Jodi (07:46):
So, to wrap this all up again, when we're talking about
plant mobile and plant immobilenutrients, when we're talking
about plant mobile, these arenutrients that the plant can
actually remobilize from a lowerpart of the plant and put up to
the top of the plant, and sowe're going to see these
deficiencies in the old leaftissue first.
Those nutrients that are plantimmobile are the ones that the
(08:07):
plant can't remobilize and movesomeplace else.
Sarah, do you want to give us arecap of what our common plant
mobile nutrients are and whatour common plant immobile
nutrients?
Sarah (08:17):
are, Again, our plant mobile nutrients, for the most
common nutrients that we'rehandling are nitrogen,
phosphorus and potassium, andour most common nutrients that
we handle that are immobile andyou will see their deficiencies.
Jodi (08:30):
The immobile nutrients at the top of the plant sulfur,
zinc, iron, copper, boron and,if you don't remember these,
listen back to the podcast, do aquick Google search and that'll
help you a ton when you're outthere trying to diagnose
nutrient deficiencies out in thefield.
Sarah (08:46):
Absolutely, absolutely Purple corn.
Jodi (08:50):
Purple corn, you ready Tune in next time for a tiny
bite of knowledge from GKTechnology where we have a map
and an app for that.
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