Managing Carbon in Agroecosystems: The Roles of Fertilizers and Crop Management

Agriculture faces the dual challenge of reducing greenhouse-gas emissions while maintaining food production under increasing climatic stress. This review examines fertilizer and crop management strategies to reducing production-related emissions and restoring carbon stocks in agroecosystems. It links fertilizer-related emissions, plant carbon inputs, and nutrient cycling to assess soil carbon sequestration in relation to both climate mitigation and soil fertility. Mineral nitrogen fertilizers often account for the largest share of the carbon footprint of crop production, but an adequate nitrogen supply is also required for photosynthesis, net primary production, root growth, crop yield, and plant-derived carbon inputs to soil. Carbon management should therefore optimize fertilizer production and use rather than simply restrict nitrogen inputs. Relevant measures include lower-emission fertilizer manufacture, improved nutrient-use efficiency, mineral–organic fertilization, manure and residue recycling, increased use of legumes and cover crops, and regulation of carbon–nitrogen interactions during organic-matter decomposition. Mineral fertilizers generally produce modest increases in soil organic carbon (SOC), whereas organic amendments produce larger gains. However, finite carbon-storage capacity, declining sequestration rates, reversibility, limited biomass and nutrient resources, and measurement uncertainty substantially restrict the contribution of soil sequestration to global climate-change mitigation. The most realistic objective of agroecosystem recarbonization is therefore to restore soil fertility, support stable food production, and increase resilience to climatic extremes.