Instructions for planting things like squashes and melons and pumpkins
call for planting them in "mounds". Can I use store bought black
"topsoil"for those mounds, and if so, how much 10-10-10 fertiliser
should I add to them.

thanks

I plant my squash & pumpkins in mounds, but I use the dirt in my garden to form
the mounds. I don't buy topsoil.
I fertilize my veggie gardens with Miracle Grow in one of those hose feeder
fertilizers about once a week.
Sue in Mi. (zone 5)
Sue in Mi. (zone 5)