Plants will take up K far in excess of their requirements without harm to the crop. This “luxury consumption” is wasteful use of potassium, but, more importantly, it can induce nutritional disorders in ruminant livestock.

Recent research has identified high K in dry-cow feed rations as the major cause of hypocalcemia. This condition, known as “milk fever”, results from a shortage of blood calcium at calving, induced mainly by excess K. Avoid overusing potassium (in the form of fertilizers or manure) in production of forages. As a preventative measure, consider shifting dry cows away from high-potassium feed rations and potassium-rich pasture. [Background reading: Cutting K in dairy feed decreases milk fever. by J.Goff & R.Horst. USDA-ARS, Ames, IA. NRI Research Highlights. 2000.]

Hypomagnesia, or grass tetany, is a less common ruminant disorder than milk fever. Low magnesium (Mg) levels in feed rations (relative to potash and calcium) causes grass tetany. The ratio of K to Mg in feed should not exceed 4:1. Use of dolomitic aglime (containing about 10% Mg) for pH management of soils used for forage production should prevent this potentially fatal nutritional imbalance.