Potassium: Nature’s Gatorade for PlantsThere’s a general concern among doctors that as we age, our bodies become less efficient at regulating temperature. They state that this puts such people at greater risk of heat illness. To avoid such problems, health professionals recommend that aging folks in hot weather drink plenty of water before going outside and eat a banana.

Bananas are rich in potassium, which helps regulate body fluids. They also say that muscle cramps suggest dehydration, which tends to indicate that electrolyte levels most likely are down. Often these professionals recommend sports drinks like Gatorade, whose main electrolyte source is potassium carbonate. Milk is also an extremely good source of potassium. “Morrison’s Feeds and Feeding” (1959) text shows that dried skim milk averages 1.46% potassium (K), 1.28% calcium (Ca) and 1.04% phosphorus (P). Most folks are surprised that the K in milk runs slightly higher than its Ca.

I have formulated mineral premixes with higher K levels to help target heat stress in lactating cattle. Understand that we don’t want to over-elevate K levels for dry cows, since elevated K levels (a major cation or positively charged particle source) can disrupt the cation/anion balance (anions are negatively charged particles). That disruption predisposes to milk fevers.

A general recommendation from dairy nutritionists is that for dry cows, K should account for 0.93% – 1% on a dry matter basis. Too much K slows down bacterial growth in the rumen, while too little K can result in difficult breeding. Because carbohydrate utilization is slowed by too little K, this deficiency will also slow growth of livestock.

Writing in his textbook “Eco-Farm: An Acres U.S.A. Primer,” Charles Walters stated that K introduces elements in the plant to each other so that they can “form compounds and set up housekeeping, or be carried from one part of the plant to the next.” He stated that even though magnesium is the cornerstone of the green-making chlorophyll molecules, K is critical to that building block’s synthesis. Plants need K before they can pull carbon, nitrogen and oxygen – at no charge – out of the air. Quoting Walters again, “They can’t even survive summer dry stretches very well without ample potassium.”

Farmers also blame increased lodging (reduced standability) on potash deficiency. Understand, potash is considered chemically to be K2O, so it’s actually only 83% elemental K.

According to Wikipedia, the English name for K comes from the word potash, which refers to an early method of extracting various K salts: placing in a pot the ash of burnt wood or tree leaves, adding water, heating and evaporating the solution. When British scientist Humphry Davy first isolated the pure element using electrolysis in 1807, he named it potassium, which he derived from the word potash.

A logical question then is “Why is potassium’s chemical symbol K?” Earlier scientists, like German chemist Martin Klaproth, in 1797, singled out the Arabic word “alqalyah” – from which we get our word “alkali” – which means “plant ashes.” In 1814, the Swedish chemist Berzelius advocated for the name kalium for potassium, with the chemical symbol K. Nordic languages, like those in Scandinavia, won out, convincing the scientific community to use the first letter of that term as the chemical’s official symbol.

Moving on into hardcore soil and plant nutrition, Walters wrote that “a deficiency causes mottling, brown top, purplish spotting.” Other K deficiency symptoms include streaking or curling of leaves, starting at lower levels of corn plants. Dead areas frequently fall out, leaving ragged edges. In grains and grasses, firing starts at the tip of the leaves and proceeds down the leaf’s edge, usually leaving the midrib green. This is not to be confused with the classic N deficiency symptom in corn, where the die-back, involving tan discoloration, starts at leaf tip and moves down the midrib. Premature loss of leaves, as well as lowered resistance to cold, are also K deficiency symptoms.

This time of year, topdressing potash fertilizers on meadows is a common practice. This should be done by following the recommendation derived from recent (within the last 36 months) soil test results. The plant desiring K topdress most is usually alfalfa. Alfalfa desires soils that are well-drained with naturally higher pH. But a lot of the better drained soils in the Northeast have larger soil particle size. Generally, such soils have reduced natural potash-supplying ability; their lower surface-to-mass ratios tend to indicate reduced cation exchange capacities. These vital, though microscopic, surface areas are storage depots for K. Thus, the soil test recommendations typically are going to indicate higher fertilizer rates for sandy soils – much, much higher compared to recommendations for clays – with silts falling somewhere in the middle. This is not an area for guessing.

Let’s recall that the moisture-regulating job site in all plants is the microscopic stomate. The countless numbers of these minute structures enable plants to gather C atoms from the air and, most importantly, limit water loss. One more critical role of K is its assignment to “oversee” the moisture regulating role of stomates. We see that regulatory process playing out when corn plants respond to drought by assuming that spikey pineapple configuration, often referred to as “firing.”

Drought is a serious fact of agriculture. I can’t overstress that loss of soil organic matter intensifies the pain of drought as well as flooding.