Performance of planted indigenous trees, Acacia galpinii and Faidherbia albida, in semi-arid Botswana

Abstract

Two popular indigenous browse, shade and poles trees, Acacia galpinii and Faidherbia albida, were evaluated for survival and growth on-farm in Malotwana, Botswana, with a mean annual rainfall of 450 mm. The trial was a two species × three spacing factorial experiment in a randomised complete block design replicated five times. The three spacings were 5 m × 5 m, 6.3 m × 5 m and 8.3 m × 5 m. The study was conducted over 6.5 years. The results showed that A. galpinii is a promising poles, browse and shade species, while F. albida exhibited high mortality (67%) at 4.5 years (after below-average rainfall). The crown width of A. galpinii ranged from 5.86 ± 0.24 m at high density to 6.56 ± 0.25 m in low-density plots. The difference in crown width among densities was significant (p = 0.0406). Diameter at breast height ranged between 10.4 ± 0.68 cm at high density to 12.5 ± 0.64 cm in low-density plantings and was significantly different among spacings (p = 0.0003).