Hi Blackjack, The need for fertilizer is determined by the quality of the soil your plants are in....some native soils require very little, if any, supplemental fertilizer. In some of my current plots I have grown large healthy plants without adding ANY ferts for the whole season.....on the other hand I have lived in other areas where the native soil needed ferts once every 7 to 10 days.
IMO it is a good idea to test your soil and proceed accordingly...you can het test kits at most garden centers or similar stores....
good luck