A review of nitrogen fertilizer and conservation tillage effects on soil organic carbon storage

Published research results on the effects of nitrogen fertilizer and tillage systems on soil organic carbon storage were synthesized to assess the impact of management policies on C sequestration. The analysis covers paired data from 137 sites with varying N rates and 161 sites with contrasting tillage systems. N fertilizer increased SOC but only when crop residues were returned to soil. C sequestration increased as more N was applied to the system, and as rainfall or cropping intensity increased. Sequestration declined at sites with higher mean temperatures and in fine textured soils. Under conservation tillage, C savings stemming from less cultivation will continue after C sequestration in soil ceases.