Organic carbon fractions and micronutrient status of soils under some plantation crops in southwestern Nigeria

The organic carbon (OC) fractions and micronutrient status of soil under cashew (Anacardium occidentale), plantain (Musa spp), oil-palm (Elaeis guineensis) and gmelina (Gmelina arborea) plantations were studied to determine their effectiveness for managing converted forest in the derived savanna ecology of southwestern Nigeria. The control secondary forest soil had statistically similar OC (2.11%) at 0-15cm with gmelina but significantly higher than those of the remaining plantation crops. At deeper depths, however, the OC content of the control forest was lower than those of other plantation crops. Apart from gmelina, other plantation crops had carbon enrichment ratio (CER) <1 at 0-15cm. Only gmelina sequestered as much non-hydrolysable carbon (NHC) as the control at 0-15cm depth. Also it was observed that plantain plantation sequestered higher NHC than the control at 15-30cm depth. At >30cm depth, however, none of the plantation crops sequestered as much NHC as the control. Using the average NHC at all the soil depth as a quality index, gmelina has a better potential to sequester NHC than the other plantation crops used in this study.