Evolution of farming practices in sub-Saharan region confronted by demographic and climatic changes: runoff control and organic matter resources management

Demographic growth and climatic change in the sub-Sahelian region threaten the sustainability of environmental resources. Modifying farming practices could help to compensate for harmful changes in environmental conditions. A research program was carried out between 1980 and 1987 in Ziga, in the Yatenga region of Burkina Faso, to identify and evaluate changes in farming practices made to ensure the development of agriculture. In 2005, a survey was carried out in the same village to assess the changes made to farming practices. This revealed two practices - zaï and djengo - that had not been previously observed or evaluated and which were widely applied in the cultivation systems. Zaï is a traditional technique for restoring degraded soil by capturing runoff using microcatchments and a localized supply of organic matter around the plants. Djengo is based on the same principle as zaï but it is applied on sandy soils whereas zaï is usually applied on degraded, crusty soils. These two practices could increase grain yields and limit the risk of crop failure. Observations also showed that there was frequent tree regeneration in plots and microcatchments where zaï or djengo practices were used. This study highlighted an example of ecological engineering carried out by farmers in sub-Saharan Africa. The development of these practices indicates the importance of the spatial organization of the determining components that drive an ecological system. Further research should be carried out into this concept to help to improve soil fertility management and farming systems in savanna agrosystems.