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.
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.
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 given 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.
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.