How much K is lost to runoff during rain or irrigation events?
There has been a lot of research on this related to nitrogen and phosphorus, but I am not aware of anything published on potassium. Let’s first agree that loss is only going to occur if the rainfall event creates surface runoff (the CEC in question is not low enough to be too concerned with leaching).
I’m going to borrow from experiments where phosphorus from recent applications is exposed to a runoff event (using phosphorus as a proxy for potassium). The actual amount of phosphorus lost in these experiments is generally very low. As percentage of what is supplied, it is generally less than 5 percent (and sometimes much lower than 5 percent). I would assume the same for potassium. Just for reference, much of this research is done with rainfall simulators that are dumping a good amount of water over a short period of time.
