Quick link to some info on radishes.
Popping in during a break at work, back to it.

http://hgic.clemson.edu/factsheets/HGIC1305.htm

radishes are the last item covered...

Jeff

Sue wrote:

I am curious as to what the soil requirements are for growing radish. Do
they prefer an acid or base soil?
I moved into a new garden spot this Spring and applied lime to the soil
before planting without testing the soil first and so far I'm disappointed
with the radish harvest.
My garden is located in Iowa and I planted french breakfast, cherry belle,
scarlet globe, german giant and white hailstone varieties. The leaves grew
considerably larger than usual compared to my old garden but not much edible
root.
I expect it may have been a mistake to apply the lime but decided on doing
this because the garden area is where a large tree had been removed the year
before and thought there may have been too much acid for good garden soil.