Soil management for carbon sequestration

An increase in atmospheric CO2 by ∼146% and global temperature by ∼1 °C since the year ca. 1750 has created an urgency to identify potential sinks for storage of excess CO2. The historic depletion of soil organic carbon (SOC) from agroecosystems is 135 petagrams of carbon (Pg C). Thus, soils of agroecosystems have a potential to sequester atmospheric CO2 and mitigate anthropogenic global warming. Of the total anthropogenic emissions of 11.3 Pg C in 2017, 4.1 Pg C (36.3%) was absorbed by land-based sinks. Hence, land-use and soil management systems that can create a positive soil/ecosystem carbon (C) budget have a potential to store C in soil. A positive soil C budget is created when input of biomass-C exceeds that of losses. Practices that can create a positive soil C budget in the surface layer (0–30 cm) are conservation agriculture, mulch farming, cover cropping, biochar and complex farming systems. Techniques to include SOC in the sub-soil (30–100 cm) are deep-rooted species and deep-burrowing earthworms. There exists a positive correlation between SOC concentration and aggregation, plant-available water capacity, nutrient retention, bulk density and porosity. Therefore, restoring the SOC stock of degraded soils is pertinent to advancing global food and climate security, allowing an agricultural solution to environmental issues.