Hello. I'm Trent Roberts, soil fertility specialist with the University of Arkansas System Division of Agriculture.
Hello. I'm Trent Roberts, soil fertility specialist with the University of Arkansas System Division of Agriculture.

Today we're going to be discussing potash or potassium deficiency in the
Today we're going to be discussing potash or potassium deficiency in the

major row crops grown across the state.
major row crops grown across the state.

For most of our row crops, potassium is the most limiting macronutrient, following nitrogen.
For most of our row crops, potassium is the most limiting macronutrient, following nitrogen.

For crops like soybean and peanut, it can often times be the most limiting nutrient,
For crops like soybean and peanut, it can often times be the most limiting nutrient,

reducing yield in our production systems.
reducing yield in our production systems.

Potash deficiency symptoms are most often seen on our lighter textured soils, which can
Potash deficiency symptoms are most often seen on our lighter textured soils, which can

include sands, sandy loams, and silt loam soils.
include sands, sandy loams, and silt loam soils.

These are the areas where we're most likely to see a potash deficiency occur.
These are the areas where we're most likely to see a potash deficiency occur.

Areas of the state that are more prone to this tend to be west of Crowley's Ridge and include the counties of
Areas of the state that are more prone to this tend to be west of Crowley's Ridge and include the counties of

St. Francis, Cross, Poinsett, Craighead, and Lawrence.
St. Francis, Cross, Poinsett, Craighead, and Lawrence.

Researchers with the U of A System Division of Agriculture have worked hard to correlate and calibrate
Researchers with the U of A System Division of Agriculture have worked hard to correlate and calibrate

soil test data, which allows us to predict when and where we can expect a
soil test data, which allows us to predict when and where we can expect a

potash deficiency symptom to occur, which may limit yield.
potash deficiency symptom to occur, which may limit yield.

What this allows us to do is take corrective measures and apply that fertilizer pre plant in order to
What this allows us to do is take corrective measures and apply that fertilizer pre plant in order to

prevent the deficiency from occurring.
prevent the deficiency from occurring.

Effective soil sampling is the first step in preventing potential potash deficiencies, and when done
Effective soil sampling is the first step in preventing potential potash deficiencies, and when done

correctly can help eliminate the potential for this nutrient robbing yield.
correctly can help eliminate the potential for this nutrient robbing yield.

We use soil test potassium categories to help define crop response to soil test nutrient concentrations.
We use soil test potassium categories to help define crop response to soil test nutrient concentrations.

In Arkansas, these categories give us a relative idea of the rate of potassium fertilizer needed to maximize crop
In Arkansas, these categories give us a relative idea of the rate of potassium fertilizer needed to maximize crop

yield, as well as the level of response for that particular crop in that particular soil test category.
yield, as well as the level of response for that particular crop in that particular soil test category.

Timing of soil sampling following previous crop harvest can be critical for soil test potassium concentrations.
Timing of soil sampling following previous crop harvest can be critical for soil test potassium concentrations.

We want to allow ample time for potassium to leach out of the previous crop residue before we take
We want to allow ample time for potassium to leach out of the previous crop residue before we take

soil samples to identify potassium soil test concentrations.
soil samples to identify potassium soil test concentrations.

Another useful tool is scouting and proper identification of potash or potassium nutrient deficiency
Another useful tool is scouting and proper identification of potash or potassium nutrient deficiency

symptoms for our major row crops in Arkansas.
symptoms for our major row crops in Arkansas.

So we're gonna start with potassium, potash, or K deficiency symptoms in corn.
So we're gonna start with potassium, potash, or K deficiency symptoms in corn.

Since potassium is a mobile nutrient in the plant, we're going to tend to see
Since potassium is a mobile nutrient in the plant, we're going to tend to see

those deficiency symptoms occur on the oldest, lower leaves first.
those deficiency symptoms occur on the oldest, lower leaves first.

You can see that this particular leaf has kind of senesced, and so as we move up to the next
You can see that this particular leaf has kind of senesced, and so as we move up to the next

older leaf on the plant, we can start to identify those deficiency symptoms that
older leaf on the plant, we can start to identify those deficiency symptoms that

are typical for grass crops such as corn, grain sorghum, rice, and wheat.
are typical for grass crops such as corn, grain sorghum, rice, and wheat.

And so in this particular example with potash deficiency, we see firing of the leaf
And so in this particular example with potash deficiency, we see firing of the leaf

margins starting at the tip and working its way towards the base.
margins starting at the tip and working its way towards the base.

This is pretty typical symptom of potash deficiency as we get these leaf margin firings first that move
This is pretty typical symptom of potash deficiency as we get these leaf margin firings first that move

inward towards the midrib and down from the tip towards the base of the leaf.
inward towards the midrib and down from the tip towards the base of the leaf.

Now we're going to talk about potash or potassium deficiencies in rice.
Now we're going to talk about potash or potassium deficiencies in rice.

Similar to corn, potassium deficiencies are going to show up first on the lower older leaves.
Similar to corn, potassium deficiencies are going to show up first on the lower older leaves.

A lot of times with rice we don't start to see those potassium deficiencies until three to four
A lot of times with rice we don't start to see those potassium deficiencies until three to four

weeks post flood, when the plant really starts to increase vegetative growth or begin
weeks post flood, when the plant really starts to increase vegetative growth or begin

to go into that reproductive growth cycle.
to go into that reproductive growth cycle.

Since it's on the lower portion of the plant, unless it's moderate to severe, it may be hard to identify
Since it's on the lower portion of the plant, unless it's moderate to severe, it may be hard to identify

unless you move that plant canopy back, and actually look and focus on those lower older leaves.
unless you move that plant canopy back, and actually look and focus on those lower older leaves.

So if we focus on the lower, older leaves of this particular rice plant, we can easily
So if we focus on the lower, older leaves of this particular rice plant, we can easily

identify potassium or potash deficiency.
identify potassium or potash deficiency.

As you can see here this lower older leaf is showing the typical symptoms of potash deficiency.
As you can see here this lower older leaf is showing the typical symptoms of potash deficiency.

Similar to what we saw in corn, we get this firing of the leaf margins that starts at the tip
Similar to what we saw in corn, we get this firing of the leaf margins that starts at the tip

and works its way towards the base of the rice plant.
and works its way towards the base of the rice plant.

This can be hard to identify due to the density of the rice crop canopy.
This can be hard to identify due to the density of the rice crop canopy.

You've really got to move those leaves back and look at the lower
You've really got to move those leaves back and look at the lower

canopy to help see these deficiency symptoms.
canopy to help see these deficiency symptoms.

Cotton is the first broadleaf row crop that we'll talk about, and depending on
Cotton is the first broadleaf row crop that we'll talk about, and depending on

the timing of the onset of deficiency and the severity, can show up at varying levels in the plant canopy.
the timing of the onset of deficiency and the severity, can show up at varying levels in the plant canopy.

This is a good example of moderate potassium deficiency in cotton.
This is a good example of moderate potassium deficiency in cotton.

As you can see, we have marginal chlorosis around the leaf edges
As you can see, we have marginal chlorosis around the leaf edges

beginning at the tip and working its way towards the center of the leaf.
beginning at the tip and working its way towards the center of the leaf.

Now we're going to focus on potash or potassium deficiency symptom identification in soybean,
Now we're going to focus on potash or potassium deficiency symptom identification in soybean,

which can be one of the most complicated of all the row crops we grow in Arkansas.
which can be one of the most complicated of all the row crops we grow in Arkansas.

One unique characteristic of soybean, especially our indeterminate soybean crops,
One unique characteristic of soybean, especially our indeterminate soybean crops,

are that they have vegetative and reproductive growth occurring simultaneously.
are that they have vegetative and reproductive growth occurring simultaneously.

So the idea of potassium being a mobile nutrient which shows up on the lower older
So the idea of potassium being a mobile nutrient which shows up on the lower older

leaves first is not always the case.
leaves first is not always the case.

As you can see here with this particular crop, we have severe potash deficiency in
As you can see here with this particular crop, we have severe potash deficiency in

the upper portion of the canopy.
the upper portion of the canopy.

So similar to other crops, potash deficiency in soybean is going to be marginal leaf chlorosis or necrosis
So similar to other crops, potash deficiency in soybean is going to be marginal leaf chlorosis or necrosis

that starts at the tip and moves towards the base.
that starts at the tip and moves towards the base.

Another useful tool is tissue testing, which can help to confirm a potassium deficiency symptom, or can be
Another useful tool is tissue testing, which can help to confirm a potassium deficiency symptom, or can be

used to identify hidden hunger.
used to identify hidden hunger.

Hidden hunger is a term we use to describe when plants are exhibiting yield loss from nutrient deficiency prior to
Hidden hunger is a term we use to describe when plants are exhibiting yield loss from nutrient deficiency prior to

when we actually see the deficiency symptoms in the field.
when we actually see the deficiency symptoms in the field.

For most of our major row crops species, proper identification of potassium deficiencies early in the
For most of our major row crops species, proper identification of potassium deficiencies early in the

season can be corrected.
season can be corrected.

Depending on the crop, the growth stage, and the level of deficiency, corrective measures can be taken
Depending on the crop, the growth stage, and the level of deficiency, corrective measures can be taken

to recover yield and optimize yield in many cases.
to recover yield and optimize yield in many cases.

If you have any questions concerning soil testing or tissue analysis for potential potassium deficiencies,
If you have any questions concerning soil testing or tissue analysis for potential potassium deficiencies,

please contact your local County Extension agent.
please contact your local County Extension agent.