In brief:

Assists in maintenance of acid-base relationship - osmotic balance, regulates movement of substrates in and out of cells, movement of water, transport of oxygen and carbon dioxide in blood, nerve impulse, heart beat, energy transfer and utilisation, protein synthesis and metabolism.

Potassium is the third most abundant mineral in the system.

Chemical properties and distribution

• Potassium represents 0.3% of body D.M and is in skin and muscle
• Potassium presents inside cells vs sodium to be the main electrolyte in plasma and extracellular fluids
• Blood cells contain 25 times as much potassium as plasma
• Muscle and nerve cells contain 20 times the potassium level as interstitial fluid.

Metabolism

Absorption:

• Mostly through small intestine
• Saliva can be high in potassium
• Certain health conditions can interfere with normal absorption
• Potassium enters cells against a concentration gradient (active process)
• Adrenal hormone (aldosterone) favours reabsorption of sodium and excretion of potassium in renal tubules
• If insufficient aldosterone - excess potassium to sodium
• Hyperactivity of adrenal – excess sodium to potassium
• Stress aldosterone – loss of potassium
• Aldosterone controls potassium in saliva
• In contrast to calcium and phosphorous, potassium is not stored and must be supplied daily but K supplementation not palatable so must be mixed with other feed

Functions

• Maintainence of acid-base relationship - proper osmotic balance
• Potassium in cell, sodium in plasma and interstitial fluid
• Sodium, potassium and chlorine are the three major electrolytes in the body and maintain cation-anion balance
• Active transport (energy required) regulates transport of substrates into and out of the cell
• Movement of water
• pH rigorously maintained at 7.4%
• To maintain potassium levels involves respiration, blood buffering, renal excretion and reabsorption
• Potassium is important in the transport of 02 and C02 in blood, responsible for half the C02 carrying capacity
• Needed for nerve impulse transmission and heart beat
• Activator or cofactor for several enzyme systems, for energy transfer and utilisation, protein synthesis and CH20 metabolism
• Potassium affects amino acid uptake by cells

Deficiency

Reduced appetite, growth, muscular weakness, stiffness, paralysis, diarrhea. Continued deficiency – intracellular acidosis, organ degeneration and nervous disorders and low serum K. May need high potassium intake to replace potassium lost in sweat.

Note: If potassium is applied to soil as a fertility building additve, applications at general fertiliser rates of potassium chloride (muriate of potash) especially on a continued basis is not advised due to potentially harmful effects of chloride on beneficial soil microbes which are in effect the 'farmers of the soil'. Hence the reason chlorine is added to swimming pools to kill biological life.

Other sources of potassium such as potassium sulphate are better suited.