Question
elizabeth,can i grow watermelon,turnip,radishes,cucumber,in a 10 by 5 area. also
the soil i use, do we remove 6 inches and replace it with a mix of compost ,top soil ,and peat moss
thanks for your help

Answer
Dear Anne,
Yes you can grow those 4 items in that space, but be sure to plant the watermelon and cucumbers at opposite ends, because they vine and they will cross if they get too close.  I don't remove top soil, but I have placed railroad ties around the garden space and added more top soil, manure, compost, etc.  
Hope this helps.  
Happy Gardening,
KD Elizabeth
www.eingedi.us