Potassium is one of the most important plant nutrients and is the second highest in terms of plant nutrient uptake. Unlike many other nutrients which are required as structural components within the plant, potassium exists mainly within solutions. This is tied to its function within plants, which include osmoregulation, photosynthate transport, enzyme activation and balancing of electrical charges across membranes.
As a result, it influences essential plant processes such as photosynthesis, transpiration and fruit development. Inadequate potassium uptake can lead to potassium deficiency, which can result in negative effects such as reduced plant biomass, photosynthesis, crop yields, crop quality and shelf life.
Therefore, being able to easily detect potassium deficiencies allows for adequate and accurate potassium fertilization, helping you prevent crop losses. Here are 3 visual signs to help you detect potassium deficiencies in your farm easily.
Visual Sign 1: Chlorosis at leaf edges
Chlorosis refers to the yellowing of plant leaves due to insufficient chlorophyll produced. Potassium-deficient plants usually show chlorosis at the leaf edges, tips, and sometimes at interveinal areas. These chlorotic areas will then slowly develop into necrotic lesions (dead tissues). These symptoms usually show up in older leaves first.
Why this happens: The lack of potassium leads to stomatal closure and drought stress, which result in the formation of reactive oxidative species (ROS), causing chlorophyll degradation which manifests visually as yellowing and dead tissues.
Visual Sign 2: Shorter and weaker stems
Potassium deficiencies can also show up as shorter and weaker stems that bend and break easily. This is otherwise known as lodging, which increases yield losses.
Why this happens: Stem strength is influenced by the strength and rigidity of cell walls. Potassium contributes to these factors by increasing cellulose content, stem fiber content, and basal internode space. Without potassium, stem strength is affected and the risk of lodging increases.
Visual Sign 3: Smaller leaves
Plants which lack potassium generally have smaller leaves compared to healthy plants. Smaller leaves help to reduce water loss, but sacrifice photosynthetic areas to do so.
Why this happens: Low potassium availability triggers the transport of storage K ions out of the vacuole, decreasing intracellular expansion pressure - a factor essential to cell enlargement, cell growth and general leaf expansion.
Other than these 3 visual signs of potassium deficiency, here are some additional indicators that show your plants may not have enough potassium:
What can cause potassium deficiency?
You may be wondering: Why am I still facing potassium problems even though I apply potassium regularly?
The answer is: potassium deficiency is not always caused by a lack of potassium fertilization, but instead can be due to a lack of available potassium for uptake. There are several factors which can cause potassium to be unavailable to plants.
Soil pH too acidic
Soil pH refers to the acidity of a soil. Acidic soils are generally unfavorable for nutrient uptake because they cause greater competition among H+ and K+ for binding sites in the soil. (H+ presence contributes to soil acidity). Without being able to bind to soil particles, K+ which is dissolved in water will leach away. Acidic soils are usually highly weathered; hence leaching is a major crop limiting factor in tropical regions.
Not enough soil oxygen and water
Soil requires adequate amounts of oxygen and water for roots to develop properly and absorb nutrients. Without sufficient oxygen, root development is stunted and water containing potassium cannot reach the roots without soil pores. When there is not enough water, potassium cannot be dissolved, move towards roots or be taken up.
Improper nutrient management and fertilization practices
Since K+ is a cation, it can experience antagonism with other cationic nutrients such as magnesium and calcium. Too much of another cationic nutrient can displace potassium from soil binding sites and cause less potassium to be available for plant uptake. Improper fertilization practices such as high quantity-low frequency application can also lead to greater K leaching and reduced nutrient use efficiency.
How can potassium deficiencies be solved?
So how can these problems limiting potassium uptake be solved? By improving soil conditions and ensuring there is a steady supply of available potassium, we can help to increase potassium availability to plants.
Liming and addition of organic matter
Liming is the addition of a basic substance that increases soil pH. By increasing the soil pH of acidic soils, the cation exchange capacity is improved, increasing binding sites for potassium to prevent loss through leaching.
Organic matter increases soil aggregation and increases cation exchange capacity. This increases the capacity for potassium adsorption in the soil, improving root growth and nutrient uptake. Organic matter also helps to buffer soil pH, preventing soil pH from easily changing.
AgroBridge’s Solution:
Use AMICOTE to increase your soil pH while without damaging soil organic matter. Unlike conventional liming materials, AMICOTE raises soil pH in a stable and consistent manner, so that you can still apply fertilizer during this period. See results in 2 – 4 weeks.
Use Champion® organic fertilizers to add organic matter to your soil. With more than 50% organic matter, humic acid and effective microbes, Champion® organic fertilizers are reliable, effective and easy to use.
Proper irrigation practices
Having proper irrigation practices in place ensures adequate water is always supplied, so that nutrients such as potassium can be dissolved and be absorbed by plants. It also prevents over-watering, preventing soil conditions from becoming anoxic or easily acidified.
Adequate K sources and fertilization practices
Other than amending soil conditions to improve nutrient absorption, the method of application and source of potassium should also be considered. Opt for sulphate-based potassium sources to reduce salt index and risk of leaching. Increase fertilizer application frequency at smaller doses to improve fertilizer use efficiency. Ensure the correct ratio of calcium, magnesium and potassium in the soil to prevent antagonism. Lastly, use K-rich fertilizers to increase the amount of potassium supplied.
AgroBridge’s solution:
Choose UNEKA®18S (30K-18S-10Mg) for a potassium-rich granular fertilizer option. The high dosage of K ensures a long-lasting supply of potassium towards your crops.
Use WUXAL® K40 foliar fertilizer when soil conditions are not the best and nutrients are not available. WUXAL® K40 supplies K through leaves, and WUXAL® additives ensure maximum nutrient absorption to fix potassium deficiencies.
Conclusion
The role of potassium in plant performance, crop yield and crop quality cannot be understated. Therefore, being able to easily and accurately identify when your farm needs a potassium boost is important so that any deficiencies can be corrected.
Still not sure if your farm has a potassium deficiency? Find us on WhatsApp at +60 12-531 8161 or contact your area technical executive here today!