-Build a 
compost heap on the spot
 Over time, any leachate from the heap will add fertility to the spot.  As the heap is turned, soil and compost will be blended.  When the compost is ready, haul away what you need, leave some to amend that spot. 
 -Gley
 Look it up.  This serves as a barrier to keep moisture and nutrients contained. 
 -Hugelkulture
 As a nutrient and moisture trap, this method is hard to beat 
 -Build
 Since nothing is growing in that spot, seems to be a fine place for a shed, chicken coop, campfire pit.