Zaï or Tassa is a cultivation technique to dig pits (20-30cm long and deep and 90 cm apart) in the soil during the preseasonplease clarify to catch water and collect compost. The technique is a traditional practice from the western Sahel (Burkina Faso, Niger, Mali) used to restore degraded drylands and increase soil fertility.
Zaï holes have been promoted by Yacouba Sawadogo from Burkina Faso since the 1980s. He introduced the innovation of filling them with manure and compost to provide plant nutrients. The manure attracts termites, whose tunnels help further break up the soil. He also slightly increased the size of the holes from the traditional models. Zaï holes help to improve the yields of trees, sorghum, and millet by up to 500%. 
References[edit | edit source]
- "Sourcebook of Alternative Technologies for Freshwater Augumentation in Africa". Unep.or.jp. Retrieved 2016-01-13.
- Kaboré, Daniel and Chris Reij. "The Emergence and Spreading of an Improved Traditional Soil and Water Conservation Practice in Burkina Faso". International Food Policy Research Institute, February 2004. http://www.ifpri.org/publication/emergence-and-spreading-improved-traditional-soil-and-water-conservation-practice-burkin (last accessed 24 December 2012)
- Hans-Heinrich Bass, Klaus von Freyhold und Cordula Weisskoeppel: Wasser ernten, Bäume schützen: Ernährungssicherung im Sahel, Bremen 2013, S. 46-48.