Zai practice: A west African traditional rehabilitation system for semiarid degraded lands, a case study in Burkina Faso

For degraded soil productivity, restoration, and green cover rehabilitation , it is essential to study and improve traditional farming systems, especia lly in the Sudano-Sahelian areas, where technical possibilities are limited . One example is the Zai practice, a very complex soil restoration system u sing organic matter localization, termites to bore channels in the crusted soils, runoff capture in microwatersheds, and seed hole cropping of sorghum or millet on sandy soils. Investigation on many fields of the Mossi Platea u (northern part of Burkina Faso) has shown a range of variations of the Za i system in relation to soil texture, availability of labor and organic mat ter, and relevance for rehabilitation of these degraded crusted soils. We d escribe a complex soil restoration system revealed during our 2 years of in quiries and experiments testing this system in two types of soil (a shallow , poor alfisol and a deep, brown tropical inceptisol). Biomass production o f sorghum is reported in relation to various potential improvements of the Zai systems and also the wild grass and shrub species that appeared after 2 -7 years of a Zai cropping system on a bare, crusted, degraded soil surface . Experimental improvements of this Zai system on two soils confirm the pos sibility not only to increase the production of cereal grains (from 150 to 1700 kg ha(-1)) and straw (from 500 to 5300 kg ha(-1)) on deep, brown soils (eutropept), but also to reintroduce a large diversity of useful plants th at may help during the fallow period and the process of degraded soil resto ration. The concentration of runoff water, organic manure, and a complement of mineral nutrients in microwatersheds increased biomass production witho ut significant change in soil properties after 2 years. This system may be useful not only to restore soil productivity but also for revegetation, e.g ., 22 species of weeds and 13 species of forage shrubs included in dry dung manure (3 Mg ha(-1) yr(-1)).