Screening of 18 agroforestry species for highly acid and aluminum toxic soils of the humid tropics

A screening trial involving 18 agroforestry species were initiated on highl y acidic and Al toxic soils of Nkoemvone, Southern Cameroon, with the objec tive of identifying fast growing species that can be suitable for improving short fallows. Selected growth parameters evaluated were plant height, ste m and crown diameter, number of stems at 3, 12 and 20 months after planting (MAP), and biomass yield at the first pruning (20 MAP). Then 9 months regr owths were evaluated for the same parameters. Outstanding height and stem d iameter were observed for Indigofera zollingeriana, Inga edulis, Grewia mol lis and Pterocarpus santalinoides. They reached between 6 and 9 m height an d between 8 and 10 cm diameter. The best height was correlated to the best stem diameter for I. zollingeriana (8.7, 8.6), I. edulis (7.7, 10.1) and P. santalinoides (6.4, 10.3). The same four species developed a crown of more than 5 m diameter and easily out competed weed in the alley. G. mollis, Gl yphea brewis, Dactiladenia barteri and I. zollingeriana had a shrubby archi tecture; G. mollis had up to 17 stem before the first pruning. Inga edulis and G. mollis produced the highest total biomass, with respectively 61 and 39 t/ha dry matter. Other species with more than 20 t/ha total mass were I. zollingeriana, P. santalinoides, and Xylia xylocarpa. The first pruning st imulated shoot development, and the response of the species was similar to before the first pruning. Therefore I. edulis, P. santalinoides, G mollis a nd I. zollingeriana had the best growth performances and can be recommended for introduction in short fallows provided their contribution to soil fert ility processes is assessed.