Potassium

A major plant nutrient which is represented by the chemical symbol K. It typically forms the second highest percentage of any plant nutrient (excluding carbon, hydrogen and oxygen) within a turfgrass leaf, with a typical dry matter mid-range concentration being around 2%.

A very mobile nutrient within a plant, it plays a significant role in controlling water movement through a plant, being the cation, which is most present within the liquid contained within cells and having relatively high concentrations in stomata to regulate transpiration as well as CO2 uptake for photosynthesis. It is important for cell division and protein synthesis. Potassium can improve disease and drought resistance as well as cold hardiness in plants due to its concentration in cellular fluids (cytosol).

It is also prone to leaching from sandy soils and therefore may require more considered fertiliser applications to ensure adequate availability for plant uptake. Potassium is readily held onto the negative edges and surfaces of clay particles, as well as by organic matter and is also fairly easily supplied into a soil solution as the plant uses up potassium from within the solution.

A deficiency of potassium can result in increased plant injury and decreased growth from environmental stresses, including drought, high-light intensity, cold temperatures, excess iron concentrations, as well as increased pest and disease damage. Chlorosis can also result from deficiency, whilst photosynthesis efficiency is reduced. Deficiency of potassium is usually initially observed in mature leaves, with them appearing to wilt and leaf tips die back, all taking on a yellowish appearance.

Excess potassium, however, can result in luxury consumption which can have negative impacts on plant growth, for example, by being in an imbalance with some other nutrients, in particular magnesium which has reduced uptake by a plant when high potassium uptake occur