Managing Chernozem for Reducing Global Warming

Abstract

Chernozems or Black Earth in Russian (Mollisols in the USDA taxonomy), cover a total of 916 million ha or 7% of the world’s ice-free land: 485 Mha in Eurasia, 290 Mha in North America and 102 Mha in South America. On the occasion of the first World Soil Day, 5th December 2005, the Chernozem was proclaimed Soil of the Year because of its environmental, economic and societal significance. Chernozems are formed under grassland across the Steppes of Eastern Europe, Russia and Central Asia, the Prairies in North America and on the Pampas in South America, under a wide range of climate with mean annual temperatures of 5–20 °C and annual rainfall of 500–1500 mm. Their thick, humus-rich topsoil contains 4–16% organic matter or 2–8% soil organic carbon (SOC) which creates a favourable structure, high water retention capacity and large plant nutrient reserves; and their subsoils exhibit a concentration of primary and secondary carbonates. Land misuse and soil mismanagement have accelerated soil erosion, undermined their productivity and depleted SOC with associated emissions of CO₂, CH₄ and N₂O. Fifty years or more of continual cultivation has depleted SOC down to depths of 120–130 cm with losses of 38–43% from the top 0–10 cm layer. Restoring degraded Chernozems is a win-win-win strategy with agronomic, environmental, economic and societal benefits including advancing the UN Sustainable Development Goals (SDGs). Restoration would sustain and enhance crop yields, use-efficiency of inputs and advance SDG2 (Zero Hunger). It would reduce gaseous emissions and sequester carbon while reducing risks of accelerated soil erosion and non-point-source pollution, advancing SDGs 6 (Clean Water) and 13 (Climate Action). It would improve farm income and profitability and advance SDG1 (No Poverty). And it would improve societal wellbeing and advance SDG3 (Good Health and Wellbeing). An important global benefit of restoring degraded Chernozems would be adaptation and mitigation of climate change by offsetting anthropogenic emissions; SOC sequestration with improved management can be 0.7–1.5 MgC/ha/y.