Estimates of carbon stocks in sandy soils cultivated under local management practices in Senegal’s groundnut basin

Summary

Soil organic carbon (SOC) is essential for the productivity of agroecosystems and for mitigating climate change. Because the SOC contents of sandy soils are usually small, the effects of agricultural management upon SOC stocks in such soils have been insufficiently studied. In West sub-arid Africa, the coarse-textured soils (mostly Arenosols) are diversely managed by smallholders. In this study, we aimed to quantify SOC stocks in cultivated soils of that region, in a context where agricultural practices rely mainly upon organic inputs derived from various integrated crop-livestock systems. SOC stocks were estimated for the 0-30 cm depth in 1,813 plots in Senegal's groundnut basin. We found that SOC stocks in farmers' fields varied between 2.3 and 59.8 Mg C ha(-1) (mean +/- standard deviation, 14.6 +/- 0.14 Mg C ha(-1)). SOC stocks were influenced slightly by soil type, but were only weakly correlated to soils' clay and silt contents. SOC stocks differed significantly among the three studied village territories due to contrasting livestock-raising systems. Average stocks were significantly higher in plots close to housings (home-fields), which receive larger amounts of organic inputs, than in plots farther from the village (out-fields). Thus, the organic inputs to home-fields improves soil C stocks of these sandy soils in the short term. Innovative agricultural practices in the studied area probably need to target options for managing all fields optimally. Those options will require continuous application of organic products-a measure that will in turn require solutions for improving availability or management of local organic resources.