Fonio (Digitaria exilis Stapf) is an annual tropical grass grown in West Africa for its tiny and husked seeds. In this region, fonio grain plays a major role in food security, preventing food shortages as it ripens outstandingly faster than other crops and can be harvested one month before other cereals like maize or millet. (Vodouhè et al., 2006; NRC, 1996). An important trait of fonio is its resistance to drought and its adaptation to climate change (Cruz et al., 2016). Fonio crop residues like straw and chaff are used as fodder and are often sold in markets for this purpose (Vodouhè et al., 2006).
Morphology
Fonio is an ascending, free-tillering annual cereal grass. It has slender, kneed stems growing up to 80 cm in height. The leaves are alternate, simple. The leaf blade is glabrous, linear to lanceolate in shape, 5–15 cm long × 0.3–0.9 cm broad. The inflorescence, a terminal digitate panicle, bears 2–5 slender, spike-like racemes, up to 15 cm long. The spikelet is stalked, narrowly ellipsoid, surrounded by lemma, palea, and glumes. The fruit is a minute caryopsis (grain), oblong to globose-ellipsoid in shape, about 0.5 mm long, white to pale brown or purplish in colour (Vodouhè et al., 2006). The 1000-grain weight is only about 0.5 g, making fonio the smallest cereal grain worldwide (Jideani et al., 1993).
Uses
In arid and semi-arid regions of West Africa where livestock feeds resources are rare, fonio straw is used as fodder for cattle, sheep, goats, horses and donkeys (Vodouhè et al., 2006; Adoukonou-Sagbadja et al., 2006; Cruz et al., 2016; Karbo et al., 2002; Nzelibe et al., 2000). In sub-humid areas, hoewever, fonio straw is often left to rot after threshing, or burned (Vall et al., 2008; Akinfemi, 2012; Mbahi et al., 2017). In the Dominican Republic, farmers grow fonio with dual purpose of grass and grain: fonio is used as a pasture in marginal areas where other cultivated grasses do not grow well (Morales-Payan et al., 2002).
Fonio straw can be used to make mattresses or in adobe production. It is a good insulating material due to its low thermal conductivity, and it is resistant to water erosion (Ouédraogo et al., 2019). Fonio straw can be burned to produce potash. Fonio straw could be a good organic fertiliser and could have potential to produce compost in pits (Vall et al., 2008). Two other fibrous residues of fonio crop are the husks and the bran. Fonio husks are usually discarded or burned, and it has been proposed that they can be used in the building industry or burned to make amorphous silica (Ndububa et al., 2016; Shamle et al, 2014). There are indirect reports that fonio bran, like other cereal brans, is used to feed poultry (Sanou et al., 2018) and some vendors propose it for sale as a livestock feed.
