Table 8. Temporal changes in SOC stock of 0-15 cm depth of an Alfisol in western Nigeria with cultivation and fallowing treatments (recalculated from Juo et al., 1995). Years after Bush Guinea Leucaena Pigeon Maize & Maize-stover clearing fallow grass pea stover -------------------------------------t C/ha---------------------------------------- 22.5 28.2 22.9 23.9 29.0 24.1 0 18.0 20.8 19.1 20.0 18.5 14.4 4 7 15.1 17.1 18.5 16.0 18.2 12.8 27.4 31.2 35.1 25.2 27.1 24.8 10 27.4 30.0 33.0 20.8 28.1 27.0 12 13 30.0 30.9 34.3 25.2 29.8 26.0 Table 9. The potential of soil organic carbon sequestration in the TFE of the humid tropics (Lal, 2005a). Area Rate of SOC sequestration Potential of SOC (Mha) (kg C/ha/yr) sequestration (Mt C/yr) Land use Agroforestry 500 100-300 50-150 Plantations 250 500-1,000 125-150 50 100-200 5-10 No-till mulch farming Improved pastures 200 100-500 20-100 1,000 200-510 Total XI. Tropical Savanna and Rangelands Ecosystems (TSREs)
Table 8. Temporal changes in SOC stock of 0-15 cm depth of an Alfisol in western Nigeria with cultivation and fallowing treatments (recalculated from Juo et al., 1995). Years after clearing Bush fallow Guinea grass Leucaena Pigeon pea Maize & stover Maize-stover -------------------------------------t C/ha---------------------------------------- 0 22.5 28.2 22.9 23.9 29.0 24.1 4 18.0 20.8 19.1 20.0 18.5 14.4 7 15.1 17.1 18.5 16.0 18.2 12.8 10 27.4 31.2 35.1 25.2 27.1 24.8 12 27.4 30.0 33.0 20.8 28.1 27.0 13 30.0 30.9 34.3 25.2 29.8 26.0 Table 9. The potential of soil organic carbon sequestration in the TFE of the humid tropics (Lal, 2005a). Land use Area (Mha) Rate of SOC sequestration (kg C/ha/yr) Potential of SOC sequestration (Mt C/yr) Agroforestry 500 100-300 50-150 Plantations 250 500-1,000 125-150 No-till mulch farming 50 100-200 5-10 Improved pastures 200 100-500 20-100 Total 1,000 200-510 XI. Tropical Savanna and Rangelands Ecosystems (TSREs)