For the cost of Liquid K with some cu zn - personally i'd spray - as long as what you knockdown is not to much - usually pre flowering they stand back up pretty decent.You could look at ground spread in future until levels are higher than what your average is now, then you should be right - all thats needed is maintenance applications.
Going by your yields quoted flower to pod conversion isn't an issue in your area, i'm lucky where l live its not either, but further north of me it can be poor. Its an important stage of recording that gets missed with beans and leaves everyone scratching there head afterwards as its impossible to tell what went on, did i not get flowers or did i get flowers and were poor or good to convert.
Ant...
Sounds like for the minimal cost of it a application of Yara Krista might payback on Beans regardless, we routinely spray foliar K and Mn on wheats at fungicide timings