What crop type for atmospheric carbon sequestration: Results from a global data analysis

Sequestration of atmospheric carbon (C) into soils is a strategy to compensate for anthropogenic emissions of carbon dioxide. The response of SOCs to crop types is yet to be determined under different environments. The objectives of this study were to elucidate the impact of crop type on the allocation of atmospheric C to shoots and roots, and ultimately to the soils and to determine its association with soil carbon stocks. Three hundred and eighty-nine field trials were compared to determine allocation of biomass and C in plants and SOCs under fields of different crop types. Grasses had the highest plant biomass production (19.80 ± 1.16 Mg ha−1 yr−1), followed by cereals (9.44 ± 0.45 Mg ha−1 yr−1), fibre (7.90 ± 1.00 Mg ha−1 yr−1), legumes (3.29 ± 0.63 Mg ha−1 yr−1), and oil crops (3.05 ± 1.16 Mg ha−1 yr−1) showing significant differences (p < 0.05). Maize (6.3 ± 0.34 Mg C ha−1 yr−1) had the highest plant C amongst summer crops, while wheat (2.2 ± 0.35 Mg C ha−1 yr−1) had the highest plant C amongst winter crops. In all the studies, crops allocated more C to their shoots than roots yielding root C: shoot C (Rc/Sc) ratios below magnitude. The greatest C allocation to roots was in grasses (Rc/Sc = 1.19 ± 0.08), followed by cereals (0.95 ± 0.03), legumes (0.86 ± 0.04), oil crops (0.85 ± 0.08), and fibre crops (0.50 ± 0.07). There was evidence that high plant C stocks were found in crops grown under carbon rich clayey soils of tropical humid areas. Natural grasses and cereals should be promoted as they appeared to yield greater potential for atmospheric carbon sequestration in plants and soils. Overall, the study evaluated the relative potential of the main crop types to sequester atmospheric C useful in screening of crop types for carbon efficiency and for development of plant C models.