Why Potassium?

Potassium (K) is required by all plant and animal life. Plants require potassium for photosynthesis, osmotic regulation and the activation of enzyme systems. Potassium deficiency in cereal crops results in reduced growth, delayed maturity, lodging caused by weak straw, and low bushel weight.

Potassium deficiency symptoms on cereal grains appear as a burning or scorching of the lower leaves. The burning begins at the tip of the leaf and continues down the leaf margin. Lower leaves are affected first because potassium in the plant is transported to the new upper leaves. Potassium deficiency in alfalfa appears as white or yellow spots on the lower leaves. Many other factors can affect the appearance of lower leaves, so diagnosis based on deficiency symptoms is risky.

Potassium chloride (KCl), also called muriate of potash, is the most commonly used potassium fertilizer. It is a relatively inexpensive nutrient, and deficiencies can often be corrected with moderate rates of application. As a result, correcting a potassium deficiency can result in excellent economic returns.

Potassium requirements of crops

Potassium removal from the soil is relatively low when only the grain of cereals is removed from the field. Potassium removal is much higher when forage crops or potatoes are grown. If the forage is fed to livestock on the farm, the manure can be used to return much of the potassium removed by the forage crops.

While an awareness of the amount of potassium removed by various crops is useful, it is not in itself a basis for determining fertilizer requirements. The majority of soils in the prairie region contain high levels of available potassium and can supply adequate amounts, even for high-use crops, for many years. On soils marginal to deficient in potassium, high use crops will require higher rates of potassium fertilizer to maintain adequate nutrition.