Is it “K” to Use Potassium?
By Jeff Higgins Ph.D
There is some skepticism within the turfgrass industry about the need and role of
potassium (K+) in turfgrass maintenance. Currently, there are no conclusive research data
that supports these initiatives; however, the skepticism has raised many questions from turf
managers as to whether they should apply potassium or not. The information below is a
“basic” review of potassium that may help you better understand what it does in plants and
whether you should consider its use in your turfgrass fertility plan.
What are the characteristics of Potassium (K+)?
K+ is highly water soluble
It has a low order of binding strength to cation exchange sites (CEC)
Na+ = K+ < NH4 + < Mg+2 < Ca+2 < H+ < Al+3
K+ is very susceptible to leaching, especially in coarse textured soils
How does K+ increase turfgrass plant tolerance to stresses?
As K+ concentration increases in plant cells, their cell walls thicken
Plant cell water content then decreases and cells become more turgid
Turgid cells are more tolerant of stress and pests
What is the role of K+ in turfgrass plants?
Considered the “plant health” nutrient
K+ is an enzyme that is essential for production of proteins and sugars
Improves plant tolerance to stresses such as cold, heat, and traffic
Improves plant tolerance to diseases
Involved in the regulation of stomatal opening and closing
Improves plant water use efficiency
How does K+ increase turfgrass plant tolerance to stresses?
As K+ concentration increases in plant cells, their cell walls thicken
Plant cell water content then decreases and cells become more turgid
Turgid cells are more tolerant of stress and pests
What are the sources of K+ used in fertilizers?
How much K+ should I apply?
Normally, K+ use rates are based on soil testing recommendations
K+ is often present in the soil at high levels but may not be available
Only small amounts of K may be in the K+ form available for plant uptake
There is no correlation to soil K+ levels and optimum plant response
Tissue testing is best indicator of K+ levels, but environmental factors complicate correlating
soil and tissue K+ levels
Soil microorganisms and clipping removal can deplete K+ levels
When available, plants will absorb much more K+ than required (called luxury consumption)
As a general rule, K+ requirements range from 50 to 200% of the amount of nitrogen applied
depending on turfgrass culture and use intensity
More K+ should be applied as lower nitrogen rates are utilized and use intensity increases
What are the leaching characteristics of K+ fertilizer sources?
Potassium Sources
What are the benefits of using coated K+ fertilizer sources?
Slow release supply of K+ for 16 or more weeks depending on specific product
Minimal leaching loss of K+
Most economical source of K+ on a per week of use basis
Environmentally friendly source