Soil Organic Carbon Sequestration in Jatropha curcas Systems in Burkina Faso

The cultivation of the biofuel crop Jatropha curcas L. in Burkina Faso may contribute to ameliorating the soil fertility of severely declining cropland through increased organic matter input and erosion control. This study addresses the potential for the soil organic carbon (SOC) sequestration in traditional and newly introduced J. curcas production systems. Five prevailing systems included interplanting with annual crops, intensely managed monoculture plantations, afforestation of abandoned cropland, plantings along contour stone walls, and traditional living fences. The SOC was analyzed in 20 paired sites of 1- to 4-year-old J. curcas plantings and adjacent cropland. Paired sites with living fences involved a longer chronosequence with 15- and 20-year-old plantings. Additionally, the contribution of J. curcas to SOC sequestration was investigated by comparing the ¹³C signature of the C inputs in four J. curcas sites with that of sorghum cropping. Linear regression analysis did not reveal a clear trend of SOC dynamics over time for the short-term chronosequences, nor could the isotopic tracer technique prove a contribution of 4-year-old J. curcas trees to the SOC stock. The 20-year chronosequence of J. curcas living fences exhibited a significant SOC increase of 62 ± 23 g m⁻² y⁻¹. Considering soil coverage of 1,200 m² ha⁻¹ by living fences (400-m hedge with a width of 3 m), 1.5 Mg SOC was sequestered. Also, changes in δ¹³C values indicated a contribution of C₃-derived C to the SOC stock. These findings on traditional J. curcas systems indicate the potential of this biofuel crop for improving cropland soil fertility in the long run.