By Doug Soldat, University of Wisconsin-Madison
As turf managers begin preparing for winter across the northern latitudes, understanding how potassium fertilization affects turfgrass health and winter disease resistance is essential. Research by the University of Wisconsin-Madison and other institutions highlights that potassium's impact on winter survivability and disease is more nuanced than potassium acting as a “winterizer” treatment. Studies have shown that creeping bentgrass can obtain sufficient potassium from sandy soils (Bier et al., 2018), making additional fertilization less impactful for growth and quality. However, potassium's effects on disease and cold tolerance are where things get interesting.
Potassium fertilization can influence winterkill and snow mold severity. For example, Rutgers University researchers observed that low potassium levels increased winterkill in annual bluegrass (Schmid et al., 2016), while potassium has not been reported to impact the winter survivability of bentgrass due to its inherent cold tolerance. Potassium fertilization consistently increased the severity of snow mold on bentgrass (Woods, 2013) and annual bluegrass (Moody, 2011) turf. Our long-term research in Wisconsin supports these findings, with treatments receiving potassium experiencing more extensive snow mold damage than those without potassium applications every year (Figure 1).
So, as you prepare your turf for the coming winter, consider how potassium fertilization might interact with your turfgrass species, climate, and disease pressure. While potassium may enhance turf resilience in some cases (annual bluegrass), over-fertilizing could exacerbate snow mold or other diseases if environmental conditions align. Stay tuned as we continue investigating potassium’s influence on winter disease and survivability in turfgrass, helping you make informed fertilization decisions for your course's health and longevity.
References
Bier, P. V,, Persche, M., Koch, P., & Soldat, D. J. (2018). A long term evaluation of differential potassium fertilization of a creeping bentgrass putting green. Plant Soil, 431, 303-316.
Moody, D. R. (2011). The effect of potassium fertilization on psychrophilic pathogen susceptibility and carbon metabolism of annual bluegrass. [Doctoral dissertation, Cornell University].
Schmid, C. J., Murphy, J. A., Clarke, B. B., DaCosta, M., & Ebdon, J. S. (2016). Observations on the effect of potassium on winter injury of annual bluegrass in New Jersey in 2015. Crop, Forage & Turfgrass Management, (2)1, 1-4.
Woods, M. (2013). 10 years ago today, a startling observation about potassium and snow mold. Viridescent: the Asian Turfgrass Center Blog.