Plants needs for potassium
Potassium is essential to regulate growth and protein production, yet it is not found in any part of any plant cell. Potassium is very mobile and important to the growth of the plant. It is essential for nitrogen uptake.
Potassium deficiency in plants
Potassium deficiency is first seen in older leaves, with a yellowing of tip and leaf edges. The yellowing extends inwards and the leaf edges turn brown and die. The center of the leaf crinkles because the center is still trying to grow and the leaf edge does not. The lack of color begins at extreme edges of leaves rather than between veins.
Plants with potassium deficiency show less vigor, fail to grow normally and are very suseptible to diseases. Deficiency of potassium shows up as leaf scorch. Cloudy areas need more potassium so more is needed in the winter. Potassium should increase keeping quality of food. Deficiency sign is a browning of older leaf tips, yellow brown spots - leaf curls upwards, internodes are short and roots are damaged (Schwartz, 1995). Potassium supplements are recommended for root development.
Signs of deficiency vary on various crops. Lettuce and cabbage show signs on tip edges that dry out and die, and overall size of plant is reduced. Carrots show dry curled leaves. Sweet potatoes form a long and thin tuber. Peas show dwarfed plants and seeds with a thick coat. Soybeans are wrinkled and misshapen. Potassium deficiency generally shows that the growing portions of plants are failing to grow.
Potassium is found in highest concentrations in plant leaves, rather than seeds. Forage crop potassium content is affected by 1) plant maturity (more mature less potassium). 2) Species and variety in species 3) management 4) fertilization 5) soil and environmental conditions (McDowell, 1985).
Blotchy ripening - portions of the tomato remain green and do not show a full green color.
Black leaf- interveinal leaf exposed to the sun turns black. Usually caused by potassium deficiency.
Scorching - can be from magnesium deficiency, excessive soluble salts, drought or born toxicity.
Potassium Toxicity
There is no known potassium toxicity for plants.
Human needs for potassium
Potassium is about 5% of total body weight. It is the third most abundant mineral in body and two thirds of body potassium is in skin and muscle cells. Blood cells contain 25 times potassium as in blood plasma.
Potassium is absorbed mainly by simple diffusion from the upper small intestine, but some absorption also occurs in the lower small intestine and large intestine (Church and Pond, 1974). Digestibility if 95%. Potassium is absorbed in small intestine, but excess sodium can deplete potassium, so can sugar and alcohol.
Daily requirements for potassium
Daily human requirements are from 2000 to 2500 mg/day. Unlike calcium and phosphorus, potassium is not readily stored and must be supplied daily in the diet.
Potassium deficiencies
Potassium and sodium help regulate water balance within the body. Potassium has key functions for many body processes. It is necessary to stimulate nerve impulses for muscles. It is a part of converting glucose to glycogen, the glucose stored in liver. It also functions with calcium to regulate neuromuscular activity. Reduced appetite a sign of potassium deficiency. Other symptoms are repressed growth, muscular weakness, stiffness and paralysis. Potassium acts as a break for regulating heart beat, suppresses heart flutter, helps prevent tetany, convulsions, and an unsteady gait.
Refined sugar can cause the urine to become alkaline so that minerals cannot be held in solution. Potassium deficiency can cause nervous disorders, insomnia, constipation, slow and irregular heartbeat. Potassium can treat high blood pressure caused by high salt intake. Colic can be treated with potassium. Potassium can be used to treat headache, allergies, diarrhea (Kirschmann, J.D., 1975).
Irritability of the nervous system is dependent upon balance between calcium, potassium and sodium ions in tissues and body fluids.
Remedies for deficient potassium in humans
Potassium content is higher is younger plant tissues, so some plant material in a daily diet should be from younger tissues. An easy remedy is sprouts that have been nourished in a potassium rich nutrient media.
Adrenal hormones favor sodium retention and potassium loss, so stress can affect potassium levels. Reducing stress levels could increase body potassium.
Maintaining electrolytic balance
In the body, potassium salts dissociate to yield potassium as a free cation or positively charged electrolyte, which must be balanced by an anion. Sodium is major extracellular cation and potassium is the major intracellular cation. Potassium also important to transmission of nerve impulses. Ionic balance exists between K+, Na+, Ca+, Mg2+.
Potassium needs in animals
Diets of grains and soybean normally maintain enough potassium to meet requirements for swine and poultry. A diet of corn and soybean should provide about 3/4 of necessary potassium (Combs et al 1985).
Mature pastures that have weathered or exposed to rain have less potassium. Since potassium is easily leached dead material usually has less potassium (Karn and Clanton, 1977; McDowell, 1985). Molasses has high potassium (usually about 4%) and can be used as a potassium supplement (12).
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