Keyhole Gardens

Keyhole gardens originated in southern Africa about 30 years ago. They now provide  food for thousands  of people there. Keyhole gardens are especially beneficial in areas with poor soil and undependable rainfall.  

Look at Sage Osterfeld's articles about his keyhole garden. 

Additional links:

https://keyholefarm.com/

https://txmg.org/bluebonnet/twenty-years-and-counting-the-keyhold-garden/

https://en.wikipedia.org/wiki/Keyhole_garden

https://www.bobvila.com/articles/keyhole-gardening/