Potassium Is Also An Essential Human Nutrient

A cut open cantaloupe, a bunch of bananas, and a smoothie.

Potassium is one of the primary essential plant nutrients. Like nitrogen, it is taken up by crops in large amounts and is critical at all stages of growth. Potassium is also an essential nutrient for animals, including humans. Potassium regulates many important bodily functions such as nerve signals, blood pressure, water retention, and muscle contractions. It helps protect against stroke and osteoporosis. Declining potassium intake has long been a concern in the U.S. population as well as around the world. A recent study published in the Journal of Agricultural and Food Chemistry examined a continuing decline in dietary potassium intake and the rise in hypokalemia, a potassium deficiency, in the U.S. population. The authors examined potassium content of common foods, including meats, fruit, vegetables, cereal grains, and others between 1999 and 2015. They also examined potassium fertilizer inputs to crops, soil-test potassium levels, and potassium removals by crops.

The authors of the study noted some important findings. Decreasing dietary potassium intake and increasing incidence of hypokalemia (4.4 percent in 1999 to 12.3 percent in 2016) were correlated with declining potassium content of a wide variety of foods over the period of the study. The authors also reported declining soil-test potassium levels and increasing crop potassium removal to input ratios. They estimated 70 percent of U.S. counties exhibited greater crop potassium removal than potassium inputs between 1987 and 2014. The authors also noted the potassium applications have declined in proportion to nitrogen and phosphorus. Additionally, the report suggested animals feeding on lower-potassium forages results in lower potassium content of meat and milk.

The authors concluded that the combination of declining crop-available potassium in soil together with potassium dilution in higher yielding crops is a strong contributing factor in the decline in dietary potassium intake. To reverse this trend, they suggested improving soil potassium management in U.S. cropping systems, reducing potassium loss to erosion and leaching, increasing potassium application in fertilizers and manures, and improving potassium levels in animal feeds.

Increasing crop yields will continue to remove increasing potassium from soils. Many of the soils in the eastern U.S. need regular potassium additions to maintain crops yields and quality. While many soils in the western U.S. are high in potassium and above critical levels, crop removal commonly exceeds application, and these should be monitored to avoid becoming deficient. Be sure to soil test and apply potassium according to 4R principles (the Right source at the Right rate, at the Right time, and in the Right place) to avoid deficiencies of this important nutrient. Food quality and human nutrition depends on balanced nutrition of our crops. Do not forget the critical nutrient potassium. More information can be found at the links below.

Sources:

Sun, H. and C. M. Weaver. 2020. Rise in Potassium Deficiency in the US Population Linked to Agriculture Practices and Dietary Potassium Deficits. Journal of Agricultural and Food Chemistry 2020 68 (40), 11121-11127. https://doi.org/10.1021/acs.jafc.0c05139

North American Soil Test Inventory