Reforestation of degraded tropical sites is often hampered by soils of
high acidity, high aluminum saturation, and low fertility. To evaluat
e the possibility of cultivating Acacia species on such soils, a study
was conducted at Waiawa, HI, to test growth under conditions of (1) h
igh acidity (primarily aluminum) and nutrient stress, and (2) no acidi
ty stress and high nutrient availability. Twelve Acacia species, inclu
ding the important native Hawaiian species Acacia koa, were establishe
d on a Ustic Kanhaplohumult soil. The experimental design was a split
plot with two fertility treatments as the main plots and the 12 Acacia
species as subplots. The treatments were: low fertility (F-0; 143 kg
ha(-1) 14-14-14 plus micronutrients) and high fertility (F-1; 8 Mg ha(
-1) lime, 143 kg ha(-1) 14-14-14 plus micronutrients, 200 kg P ha(-1),
and 77 kg K ha(-1)). Acacia angustissima, Acacia aulacocarpa, Acacia
auriculiformis, Acacia cincinnata, Acacia crassicarpa, Acacia implexa,
Acacia koa, and Acacia mangium grew significantly faster under the hi
gh fertility treatment. Three species, A. cincinnata, A. crassicarpa,
and A. mangium, are recommended for planting on infertile acid soils.
The volume of A. koa was increased ten-fold by the high fertility trea
tment. Additional study on koa's nutritional requirements is suggested
in order to identify the nutrients contributing to this increased gro
wth.