Agronomic crops require relatively large amounts of potassium (K). Potassium concentrations in plant tissues and total seasonal requirements are similar to and sometimes greater than nitrogen (N). In a sense it is a testament to the K supplying power of soil that K nutrition has not received more research attention over the past decades. Only in the past few years have cotton researchers, extension specialists, and industry agronomists strongly focused on the benefits of K fertilization in cotton production.

The concept in the western U.S. has traditionally been that K nutrition is "generally adequate" for most agronomic crops. It was thought that soils with high pH (above 7.0) and high exchangeable bases, which includes calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), were not deficient in plant available K. Such a generalization serves no useful purpose today. There are simply too many exceptions that have been clearly documented by our agricultural research institutions. In fact, adhering to such a generalization retards progress because it suggests K should not be a research priority.

Late-season K deficiency which has been recognized across the entire Cotton Belt in recent years suggests more than simply a depletion of available soil K by long-time cropping. Today's higher yielding varieties have a higher K demand, exaggerated during boll development, which can outpace the soil's ability to supply K. Management of fertilizer K is being reevaluated to consider peak in-season demand periods. Methods of soil testing are also being re-evaluated, including supply rate estimates (lb/A/day).

Fertilizer K will undoubtedly play an ever-larger role in cotton production. In order to maximize it benefits for higher yield and improved quality, understanding how it behaves in soil is essential.