The double-dig is a digging technique used in the French intensive gardening and the GROW BIOINTENSIVE system. Double-digging is used until the soil has obtained a good structure. Once a good structure has been established, surface cultivation is preferred (loosening top 5cm of soil) for several years.
GROW BIOINTENSIVE proposes four types of double-dig for four different situations:
1. Initial double-dig: Used when the soil has never been double-digged before.
2. Complete texturizing double-dig: Used when the soil has never been double-digged before and when the soil is heavy and compacted.
3. Ongoing double-dig: Used when the soil has already been double-digged, but the when the soil hasn't obtained a good structure, yet.
3. U-bar dig: Alternative method for the ongoing double-dig, using a "U-bar".