Why Do Plants Need Potassium? Symptoms & Solutions To A Deficiency

Why plants need potassium? Well, if you want to see healthy plants in your garden, give them potassium! It’s as simple as that. The gardening world classifies potassium as one of the macro-nutrients for plants. It’s not only the availability of potassium that’s essential for plants. They’ll need large quantities of this nutrient to thrive.

Keep reading, and you’ll learn all about the importance of potassium for your precious garden and how to save your beloved plants from its deficiency.

Why Is Potassium Important To Plants?

Why do plants need potassium in the first place? Well, potassium (K) is an indispensable element for plants. Here are all the different reasons why it’s vital to the plants.

  • It prevents many plant diseases.
  • Potassium builds resistance in plants against pests.
  • It helps in the synthesis of protein and starch in plants.
  • K is also vital in the biochemical reactions that are at work within the plants.
  • It promotes the growth of the root system and makes the plant more drought resistant.
  • K helps in transporting water and nutrients to the parts of the plants where they are needed.
  • It is a valuable resource that ensures successful photosynthesis since it controls how the plant will respond to the light shining on its leaves by opening and closing the stomata.

Different Potassium Types In The Soil

Most soils usually have a potassium content exceeding 20,000ppm. This may sound like a lot, but all this potassium isn’t available to the plants. Also, plants actually consume tiny quantities of the soil’s potassium. Potassium in the soil can be broadly classified into three forms:

Unavailable Potassium

It is not available to the plants. Almost 95% of the soil’s potassium is present in this form.

Slowly Available Potassium

This form of potassium is present between the layers of clay and is in the process of being fixed. It may not all be available in a growing season but will act as a reserve for later growing seasons.

Readily Available Potassium

This is the water-soluble form of potassium that’s readily available for the plants. The routine soil testing procedures measure this form of potassium in the soil.

The quantity of potassium available to plants growing in a particular soil varies with the soil material and other factors. In most cases, extra potassium dose through fertilizers helps ensure the optimal supply of the element.

What Affects The Uptake Of Potassium (K) In Plants?

The levels of K in the soil aren’t the only factor affecting its availability to the plants. Potassium uptake in plants is affected by several factors:

The Soil Moisture

Increased soil moisture enhances potassium availability since water makes the particles more mobile, moving quickly to the plant roots. But, waterlogged soils will also reduce K’s accessibility to the plants.

Soil Aeration

Air is essential for the respiration of roots and potassium uptake. Overwatering can result in compaction of the soil, decreasing the oxygen levels and the plant’s ability to absorb potassium.

The Temperature Of The Soil

Low soil temperatures reduce potassium uptake by plants. The optimal temperatures for the most significant potassium uptake lie within the range of 60 to 80°F (about 15 to 27°C) for most plants.

The Type Of Plant Your Growing

Different plant varieties vary in their ability to uptake potassium. It depends on the structure of their roots and their surface area. Grass usually has branching roots, giving them an edge over other plants in K absorption.

Plant Population

An increase in plant population in the soil increases the demand for K. Don’t overcrowd your garden, especially with potassium-demanding plants. Plant the varieties that are more demanding of potassium apart from each other so that they don’t deplete each other’s supply.

Signs Of Potassium Deficiency In Plants

Now you know why plants need potassium. Since it is essential in so many different ways for the plants, they won’t do well if it’s deficient for them in the soil. There are a variety of symptoms that are a sign of potassium deficiency in plants.

The deficiency symptoms typically start from the lower leaves and move up to all the plants’ different parts. Different plants exhibit various symptoms in case of severe deficiencies. Some of these symptoms may include:

1. Chlorosis

It begins with the leaves’ yellowing or browning, followed by falling leaf edges or shedding the entire leaf.

2. Stunted Growth

Since potassium helps in plant growth, its deficiency can affect the healthy development of plants. Since the roots and stems will develop poorly, the growth of the plant will also slow down.

3. Reduced Yield

Potassium deficiency also results in the reduction of flower and fruit development. If you notice a reduced yield, a possible reason for the problem could be potassium’s insufficiency in the soil.

4. Weak Resistance To Temperature Changes

Since potassium helps transport water and nutrients to all the parts of a plant, its insufficiency makes them vulnerable to climatic changes. Some plant varieties show specific and very characteristic symptoms if there isn’t potassium available:

Potato: Browning leaf margins, starting at the older leaves, can result from potassium deficiency in potatoes. It usually appears during tubers’ development in July since tubers will demand lots of potassium during their development.

Soybean: The lower leaves’ edges turn from light green to yellow with a potassium deficiency in soybean.

Corn: Browning of the lower leaves’ edges together with the strips’ appearance in the rest of the leaf suggests a potassium deficiency in corn.

Alfalfa: Yellow spots near the leaf borders appearing initially on the older leaves is a typical potassium deficiency in alfalfa.

Using Soil Tests To Diagnose Potassium Deficiency

Potassium deficiency can sometimes be confused with other plant problem symptoms. Even when there is a potassium deficiency, it could result from excess calcium or lime in the soil, unsuitable pH, or lack of aeration in the ground, rather than true soil deficiency. How do you know if potassium’s insufficiency of your plants comes from the element’s deficiency in the soil or other factors?

The simplest solution is to perform a soil test. A soil test will tell you if there’s enough potassium in the soil for your plants or not. You can complete a soil test at home using a soil testing kit, available online or at any gardening store. You can also use a soil lab to perform the analysis for you.

The soil test will tell you the levels of nutrients, including potassium, in your soil. This will help you figure out the kind of fertilizer you’ll need to apply to the land. Some soil tests will also tell you the exact quantities of potassium fertilizers you’ll need in the soil.

Always Perform A Soil Test Before Doing Anything
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What Kind Of Potassium Fertilizers Are Available?

Potassium fertilizers are also called potash fertilizers. That’s because they include a compound called potash. Potash is a natural substance found in mines and oceans. The burning of wood can also produce it. Even though potash is a natural substance, not all fertilizers with potash are organic.

If your soil is severely deficient in potassium, you’ll need a high potassium fertilizer. High potassium fertilizer is a fertilizer with a higher concentration of “K.”

Most fertilizers are recognized by their “NPK” ratios. N – nitrogen, P – phosphorous, and K – potassium will tell you the balance of these primary nutrients for plants present in a specific fertilizer variety.

A Quick Fix To Relieve The Symptoms

Yellowing or browning leaves and other symptoms can be relieved through a foliar fertilizer spray. Not all fertilizers are suitable for foliar application. If you decide to use this solution, please read the instructions on the package to use it properly.

Organic Solutions

Commercial potassium fertilizers aren’t the only solution to catering to soil deficiencies. Organic products offer a more long-lasting solution to rectify potassium deficiencies. Compost made from food waste, particularly banana peels, is a rich source of potassium. Wood ash can also be applied to add some extra potassium to the soil. Greensand, available in gardening stores, is also an excellent organic source for potassium.

Amend your soil with organic compost! Doing this will ensure that nutrients are gradually released in the ground and uniformly available to the plants.

Final Words

Did you get your answer to why plants need potassium? Don’t let the lack of potassium or any other nutrients harm your plants. After all, you’ve spent so much time and effort in your garden. Don’t let it all go to waste; get to the source of the problem and make the necessary fix before it’s too late.

Thankfully, insufficient potassium isn’t a big problem, and you can fix it by applying the right fertilizers. But, it’s always good to test your soil before adding more potassium to it.

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