Este Link no existe en su idioma, Ver en: English (en),
O usar Google Translate:  

donnayoung.org/science/garden/...n/double-dig.htm

Double digging is a labor intensive way to prepare a garden bed for planting. It is also a time honored way to prepare a garden bed for planting. Double digging improves soil aeration and drainage and, if you add compost, improves soil texture.