I have a buddy that would point out fields along 54 up towards land-o-lakes that he would go shroomin in....said he had to run from a few farmers...LOLI used to live off Little RD and 54. Had very good luck with the fields closer to Land' O Lakes/I-75, US-19 is nothing but commercial and residental, no fields anymore. I remember their was a little field behind Vetrans Village and The River that would get packed full of mushrooms around September!
Go down twords landolakes around 41 in the New Tampa area. There are fields everywhere, you just have to look around.
Or you could go by the incinerator off Hicks RD in Shady Hills, that's Pasco County, or Hernando. 75 to 52, take 52 west until you get to hicks road. then turn Right and drive for ever, there are fields full of shrooms on both sides of the road by the incinerator.
Landolakes and zepherhills has tons of fields too!
Just go look around bro.