Potential of natural and improved fallow using indigenous trees to facilitate cacao replanting in Ghana

Abstract

Poor establishment, due to loss of soil fertility, weeds and lack of appropriate shade, is a major constraint to replanting cacao on previously used land. Spathodea campanulata, Newbouldia laevis and Ricinodendron heudelotii planted as monospecific improved fallow and Terminalia ivorensis, T. superba and Antiaris toxicaria planted as a multispecies improved fallow and a natural tree fallow were assessed for their potential to facilitate cacao replanting in a randomized complete block design experiment. Simpson and Shannon diversity indices and species richness in the natural tree fallow were 0.6, 1.6 and 20, respectively, at 4 years after trial inception. The Multispecies and the R. heudelotii improved fallows had better height growth, crown development and light transmission characteristics, which are desirable for cacao shade. However, these were not comparable to S. campanulata or the natural tree fallow in terms of improving microsite topsoil pH, % organic carbon and % total nitrogen and site capture. Since optimum fallow period is shortened by growing fast-growing trees, the height growth rate >2.0 m per annum in all the treatments except N. laevis indicates the suitability of these species for improved fallow. The trees species showed different and complementary characteristics and from a standpoint of biodiversity conservation and the future floristic composition of the landscape the natural tree fallow with its diversity of tree species may be recommended as a rehabilitation technique to facilitate the replanting of cacao with a diverse overhead shade.