Describe the potential synergies and trade-offs between carbon sequestration and crop productivity in long-term no-till systems, and how these trade-offs may impact global food security.
The additional SOC storage potential in the topsoil of global croplands ranges from 29 to 65 Pg C. These values only equate to three to seven years of global emissions, potentially offsetting 35% of agriculture's 85 Pg historical carbon debt estimate due to conversion from natural ecosystems. The total C sequestration potential of the world cropland is about 0.75–1.0 Pg/yr or about 50% of annual emission of 1.6–1.8 Pg by deforestation and other agricultural activities. The global potential of SOC sequestration through these practices is 0.9±0.3 Pg C/year, which may offset one-fourth to one-third of the annual increase in atmospheric CO2 estimated at 3.3 Pg C/year. The cumulative potential of soil C sequestration over 25–50 years is 30–60 Pg. Average sequestration potential in agroforestry in India has been estimated to be 25 Mg C ha−1 over 96 million ha. Carbon sequestration was 2.5 Mg C ha⁻¹ yr⁻¹ over the 22-yr lifespan for the tagasaste treatments, with a change of 0.9 Mg C ha⁻¹ yr⁻¹ in SOC and 1.6 Mg C ha⁻¹ yr⁻¹ in biomass. 'No-till' (NT) agriculture, which eliminates nearly all physical disturbance of the soil surface on croplands, has been widely promoted as a means of soil organic carbon (SOC) sequestration with the potential to mitigate climate change. A direct seedling mulch-based cropping system increases soil organic matter, as a result of increased carbon inputs and decreased soil disturbance. Mulch can increase soil organic matter (SOM) and carbon sequestration in the top 0–5 cm soil depth. Agroforestry practices can help mitigate emissions and store carbon in both soils and trees. Not only does agroforestry provide above-ground benefits in the field but it also provides crucial below-ground benefits.
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