Carbon-nutrient stoichiometry to increase soil carbon sequestration

► Hypothesis: nutrient availability (NPS) not just C inputs can limit humus formation. ► Supplementary nutrient addition doubled the humification efficiency. ► The humus-N, -P and -S levels increased in concert with humus-C levels. ► Nutrient availability is critical to the sequestering of C into soil humus fraction. ► Implications for strategies to increase long-term C sequestration in soils.