Potassium increases dollar spot?

When you think of potassium (K) fertilizer, you probably think of it as beneficial to the grass, rather than as a product that might stimulate disease. A team of researchers (Xu, Clarke, Ward, and Murphy) at Rutgers University have published "Potassium fertilization effects on dollar spot of annual bluegrass and creeping bentgrass" with these surprising results:

- "Increasing K fertilization rate consistently increased dollar spot severity on ABG [annual bluegrass or Poa annua] and CBG [creeping bentgrass] - "increases in both leaf tissue and mat layer K were associated with greater dollar spot severity on both species"

Of course there…