Phenology and fruit production of Piliostigma reticulatum (DC), Hochst., an agroforestry forage species in the Sahel

In central Burkina Faso, Piliostigma reticulatum is a more and more adopted agroforestry species by farmers but is increasingly over exploited because of the use of its pods as forage. Therefore, understanding its phenology and fructification becomes urgent for a better management of existing parks. The flowering and fructification stages of two populations (41 trees of 10 years old obtained from stumps and 35 planted trees aged 4 years) were monitored every two days on the same fallow during three consecutive years. Physical parameters of each tree were measured and the pods harvested at maturity, counted, dried and weighted. The fruit production of P. reticulatum happens once a year during the rainy season. Old trees’ flowering as well as their fruit formation started earlier than for younger ones. These stages (flowering and fruit formation) started in July but August is the most determining month because of the regular and sufficient rainfall during this period. Sixty percent of trees aged 10 to 12 years reached 100 % flowering stage while only about 12 % of 4 to 6 years old trees reached this stage. Fifty-six percent of plants aged 10 to 12 years reached 100 % fruit formation stage whereas only 12 % of trees aged 4 to 6 years could reach this stage. The old populations produced more pods than less aged ones (8 kg against 1 kg). Pod production was determined by the magnitude of the tree’s crown, which was strongly correlated with the pod weight (R2= 0.77) and their number (R2= 0.75)