I think technically you're supposed to put your P&K out several weeks to even a month or more ahead of time.....P stays in the soil a long time but also takes awhile to become available to the plant. It doesn't move through the soil very fast. There's a word I'm looking for here....hmmmmm…...I think of it in a minute....Anyways, K is similar but not to the same extent. I added K in the fall and had my levels at 220 lbs/ac.....by spring it had only fell to 180 lbs...