Apple plant requires correct level and large quantity of Potassium for successful completion of their life circle. Role of Potassium in apple tree growth is quite significant in nature. Potassium plays important role in manufacturing and translocation of sugar and starches.
It helps in uptake and transpiration of water by tree. Deficiency of potassium hinders root growth, colour and quality of the fruit. Deficiency impact directly on yield of tree. In severe deficiency,it can make tree uneconomic to maintain.
As a prominent apple grower, we need to know:-
• Role of Potassium.
• Source of Potassium.
• Effect of Potassium Deficiency.
• Visual Inspection for Potassium Deficiency.
• Relation between Nitrogen and Potassium.
• Effect of Excess Potassium.
• Potassium Application.
Role of Potassium
Among all nutrient potassium is the quality nutrient which helps in refining fruit shape, size, colour and plant growth. Potassium helps in opening and closing of stomata as as result indirectly helps in regulating uptake of carbon dioxide by plant.
Stomata are tiny holes or pores mainly under the leaves in plant tissues which allow plant in exchanging Carbon dioxide and water to environmental.
Stomata helps in reducing water loss to surrounding in hot or drought conditions by closing the tine pores in plant tissues. So potassium function is to allow uptake of carbon dioxide which helps in photosynthesis of plant. Furthermore it limits the water loss from plant.
Under drought or dry conditions, water loss to surrounding is maximum. So to minimise water loss guard cell kicks out positive potassium ion to surrounding cells. This causes water in guard cell to move to surrounding cell which is having high solute concentration. Due to loss of water, guard cell shrink itself and closes stomata pores.
Potassium helps in activating enzymes whose function are directly linked to growth of plant. Potassium helps in activating Adenosine Triphosphate which is energy bank for Chemical processes in Plant
Source of Potassium
Potassium level in Himalayan range particularly in Himachal Pradesh is quite high. Average Potassium content in most soil is 2 %, but can reach 4 % in favourable conditions.
Surprisingly soil solution content of potassium is quite poor as it is mostly unavailable to apple tree because it is not reactive with many soil minerals.
Most part of potassium is absorbed be the tree roots from the soil water solution. Some Potassium is also picked directly by the roots from soils. Clay soils or soil rich in clay materials have shown excellent affinity toward absorption of Potassium.
Potassium uptake plant roots is mainly by the diffusive flux in direction toward apple plant that a soil can maintain. Apple tree have low root density as compared to other fruits.Hence Potassium is deficient in light texture soils having high sand content and which is susceptible to drought.
Uptake of Potassium by plant generally depend on many factor like climate, type of soils and apple tree root system. Potassium uptake by Apple tree is poorly correlated with available potassium in soil. Moreover soil analysis of potassium does not provide adequate data for availability and uptake of Potassium.
Effect of Potassium Deficiency.
• Deficiency of Potassium causes following symptoms in Apple plant:-
• Tips and margins of leaf burns up and scorch on older basal leaves. At severe Deficiency edges becomes irregular because dead tissue breaks off.Since Potassium is major positive ion taken by apple tree, under severe deficiency compensatory positive ion mainly magnesium and potassium are taken up by Plant. So abnormal high content of magnesium in leaves are found in potassium deficient plant.
• Potassium deficiency results in poor photosynthetic capability resulting in reduced fruit size and poor colour content in fruit.
• Shoot growth is thin and short. Many lateral buds do not unfold and remain dormant.
Visual Inspection for Potassium Deficiency
Potassium deficiency can checked directly from health of leaves. Potassium Deficient leaves turn yellow or brown at margins or edges. First evidence of potassium deficiency can be seen when leaves start to change colour to light green specially on older leaves.
In Second stage is followed by death of tissues. Furthermore scorch moves inward from leave margin. Leaf becomes brown at margins .Necrotic spots develop between leaf veins and in severe condition leave start to falls.
Depth of scorch depend on moisture content in soils and on dry weather. It is important to note in wet conditions it may not even occurs as surface moisture necessary for absorption of potassium. That is why trees under mulch are highly efficient in absorbing potassium content from soil.
Calcium Deficiency
Potassium Deficiency
Nitrogen Deficiency
Magnesium Deficiency
Potassium Deficiency
Relation between Nitrogen and Potassium
Apple tree demand for Potassium is similar in magnitude of as Nitrogen. Both Nitrogen and Potassium concentration in leaf is among highest among all other nutrients.
Balance between Potassium and Nitrogen is important for Plant growth. Higher Application of Nitrogen to Apple tree specially in form of Ammonium may lead to Potassium Deficiency.
Effect of Excess Potassium
Excess Potassium is not toxic to Apple plant . But excess Potassium hinder uptake of magnesium and calcium. Most importantly soil will become magnesium deficient if excess Potassium is applied to soils. It is always advisable to test soil before applying excess potassium to soils.
In order to increase availability of potassium to Rooting depth of Apple tree in grower orchards, it is generally advisable to apply moderate to heavy application of potassium salts to the soil surface.
Potassium Application
In general full grown apple tree is capable of bearing 200 kg apple . As per research apple fruit utilises 360 gram of Potassium. Roots, leaves and branches of apple tree utilises 60 gram of Potassium. Hence apple tree requires 400 gram of potassium for completion of healthy life cycle.
Good growth and positive yield were observed Forshey and Cummings when 50–100 kilogram was added per hectare in apple orchards during their research.
Role of Potassium in apple growth Apple plant requires correct level and large quantity of Potassium for successful completion of their life circle.