Today we're going to  discuss potash or potassium deficiency in the major row crops grown across the state. 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, reducing yield in our production systems. Potash deficiency symptoms are most often seen on our lighter textured soils, which can include sands, sandy loams, and silt loam soils. These are the areas where we're most likely to see a potash deficiency occur .

                 

          We will have four topics to discuss potassium uptake, its mobility in the plant once it is in the plant, deficiencies and toxicity symptoms and how to correct these deficiencies and toxicities if they do occur.                    Potassium uptake is a passive process it is a positively charged ion which can be easily taken up into the plant. Once potassium is taken up into the plant it is mobile.              Mobility:- If potassium is not available in the root zone or there is inadequate root growth potassium can be remobilized from the oldest leaves and relocated up into the newest growth via the phloem 

          Deficiencies and Toxicities:- If there are potassium deficiencies there can be brown scorching and curling of leaf tips as well as chlorosis or yellowing between leaf veins symptoms that are very evident. Because potassium is important in plant water status it mimics a lot of the symptoms  with associated drought stress. So, what will happen is that the oldest leaves will become yellow or speckled or necrotics pecifically on the leaf margins.                     Again mimicking more of the drought stress or a salt stress. Leaf scorch can also occur looking as if the plant leaves have been burned. There are many types of environmental and cultural conditions that can cause potassium deficiency. Things that limit root growth such as    compacted soils sometimes will induce potassium deficiency. Sandy soils tend to be low in potassium because the soil does not readily bind potassium. Dry environments or heavily crop soils or excessive applications of nitrogens pecifically ammonium or magnesium can induce potassium deficiencies. 

Plants that are prone to Potassium deficiency are corn, cotton, rice, Soyabean, etc. 

Potassium Deficiency in corn :-                            

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. You can see that this in the picture, 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 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 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 inward towards the mid rib and down from the tip towards the base of the leaf. 

       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. 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 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 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 identify potassium or 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 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. 

   Potassium Deficiency in cotton :-

  Cotton is the first broad leaf 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. This is a good example of moderate potassium deficiency in cotton.                    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. 

           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 State.  One unique characteristic of soybean, especially our indeterminate soybean crops, 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 leaves first is not always the case. As you can see here with this particular crop, we have severe potash deficiency in the upper portion of the canopy. 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

               Now how do we correct these deficiencies and toxicities if they occur?           Potassium deficiencies can be corrected by just checking the fertilizer and making sure that there are adequate amounts in your plant nutrition program. For example if you have a deficiency symptom you could apply a potassium nitrate solution or increase the amount of potassium in the fertigation system using nitrogen sources such as potassium nitrate. Check your fertilizer injectors for proper operation and settings or fertilizer application rate to make sure they are correct. If you are working in the system where there are high sodium levels some reclaimed waters or some well waters have high sodium, make sure this is not the case because sodium would also compete with potassium for uptake and can cause a potassium deficiency symptom. Also check ammonium and magnesium levels relative to your potassium levels. If there is high ammonium and or magnesium relative to potassium you can also induce potassium deficiencies because these two ions can't compete with potassium for uptake into the plant.

        Can potassium toxicities occur?

Yes again check your fertilizer and injector operations and settings and make surethat high rates of potassium have not been added. In a nutritional program, high potassium can actually induce magnesium deficiency symptoms because they compete with each other for uptake.

This is all about the potassium Deficiency in plants... Thank you!!