Fruit production ofAcacia tortilis andA. nilotica in semi-arid Ethiopia

Dry, dehiscent fruits ofAcacia tortilis provide important fodder for pastoral livestock in dry seasons on the central Borana Plateau, fruits ofA. nilotica may also be useful during drought. Information was needed on fruit yield to assess what these species could contribute to improved calf feeding systems based on local resources. Fruit production of 10 mature trees per species was measured at five sites for seven months during 1988–9 (n=50 per species). Fruit yields varied according to site, season and species x site (each atP<0.001), but there was no main effect of species (P=0.13). Yields were not correlated with trunk diameter at breast height (DBH) or canopy area within or across species (P>0.05 in all cases). Yields ranged from 0 to 40 kg DM per tree overall, with an average of 5.3 kg DM per tree (or 65 g DM/m² of canopy area). This average tree had a DBH of 26 cm and a canopy area of 81 m². Low and highly variable fruit yields appear to constrain enhanced use of these species here. These species warrant further attention in research and development, however, given their strategic value as forage resources in pastoral systems and their ability to persist in variable environments.