Potassium Deficiency in Plants

Potassium Deficiency in Plants
Potassium is an important mineral nutrient for plants. Find out what potassium deficiency in plants does to them, and how to detect if a plant is potassium deficient, from the following write-up.
Gardenerdy Staff
Banana plant in Rumtek Sikkim India,Tibet, Asia
Plants derive much of their nutrition from soil in the form of minerals while absorbing carbon and oxygen from the air. These minerals that plants extract from the soil and absorb along with water through their roots can be classified into three distinct categories - primary macronutrients, secondary macronutrients, and micronutrients. The primary macronutrients for plants include nitrogen, potassium, silicon and phosphorus. The secondary macronutrients for plants consist of magnesium, calcium and sulfur. Macronutrients, especially the primary ones, are extremely essential for the growth and health of plants, and any deficiency of these will lead to withering, malnutrition, and death of the plants. Sodium, selenium, nickel, iron, manganese, zinc, copper, chlorine, boron and molybdenum, make up the micronutrients category, and are required in trace or very small amounts for the healthy growth of plants.

Role of Potassium in Plant Nutrition

As we can see, potassium is a primary macronutrient. This makes it very important for the proper growth of plants. Potassium regulates growth and metabolism in plants, and its deficiency adversely hampers all those functions of the plant which are directed towards synthesizing nutrients and derive food or metabolic fuel from them. For instance, insufficient amounts of potassium can interfere with the plant's photosynthesis function, which is absolutely essential for converting minerals and nutrients into the right form of plant nutrition. Most fertilizer ingredients include a healthy dose of potassium to encourage growth and improve metabolism in plants. What are the causes and effects of potassium deficiency in plants? What are the external signs of such a deficiency? The following segment deals with these very points.

Causes of Potassium Deficiency in Plants

Most cases of potassium deficiency depend upon soil type, or rather the water retention capacity of a particular soil type. Soils that have a low clay content - such as sandy, chalky or peaty soil - are unable to hold moisture, and water drains away very quickly from these types of soil. Since potassium is highly water-soluble, its ions leach away along with the escaping moisture. Potassium deficiency in aquatic plants, particularly those kept in aquariums, often occurs due to the presence of carbon in aquarium filters, which lowers the potassium levels of the water.

Effects and Signs of Potassium Deficiency in Plants

As mentioned previously, insufficient amounts of potassium, which is a primary macronutrient, leads to growth and metabolic disorders in plants. Even though a plant may absorb all other essential minerals from the soil and may be exposed to healthy amounts of air, moisture and sunlight, if it is deficient in potassium, it will not be able to put all these other raw materials for plant nutrition to any good use. Since metabolism of nutrients takes place in the leaves, the first signs of potassium deficiency would surface in the form of yellowing of the young leaves. Older leaves will start withering around the edges and will show brown scorch marks on them, despite being kept in the shade and watered regularly. The spaces between the veins on the leaves will assume an unhealthy, yellowish hue. If you turn the leaves over and take a closer look on the undersides, you may also see purple spots appearing there. The discoloration and withering of the leaves occurs first in the older leaves, as a plant's physiology is intelligent enough to detect a macronutrient deficiency, which makes it allocate all the potassium it gets to the newer and younger leaves, in order to allow them to mature properly.

Potassium deficient plants are more susceptible to various kinds of diseases and parasitic infestations, as their defenses are weakened owing to their inability to produce sufficient nutrition. As a result, their growth and overall health is adversely affected. Cell walls of the plants also become weaker owing to potassium deficiency, which further serves to weaken the entire plant. Adding potassium rich fertilizers, generically known as potash, to the soil, solves this deficiency problem to a large extent. These may include chemical potassium fertilizers as well as organic compounds such as wood ash, comfrey derivatives, decayed banana skin, seaweed compost, etc. For restoring healthy potassium levels in aquariums, specialized mineral specific plant food can be added to the water.