Nitrogen input effectiveness on carbon sequestration in rainfed cropping system

The combined effect of total N and C/N ratio had a large influence on the decomposition rate and consequently onpotential soil organic carbon sequestration.The aim of the work was to evaluate Carbon sequestration potentiality under three mineral N fertilization levels ininteraction with two cropping systems characterized by addition of N input due to leguminous species in the rotation.The study was carried out in the semiarid Mediterranean environment in a 18years long-term experiment. Iswell know that in the semiarid environment the excess of N fertilization reduces biomass yield and the consequentC input. On the contrary, both N and C input determine high difference in C/N input ratio and faster organic mattermineralization.Results showed no influence of N fertilization on SOC sequestration and a reduction of SOC stock due to croprotation due to lower C input. Crop residue quality of durum wheat-pea crop rotation characterized by a fasterdecomposition rate could explain the lower ability of crop rotation to sequester C in the semiarid environment.