Estimating carbon sequestration potential on U.S. agricultural topsoils

Abstract

A better understanding of the potential for increasing soil carbon sequestration is necessary to estimate the greenhouse gas emission offset potential from agricultural soils. The objective of this research is to use the 2006 Intergovernmental Panel on Climate Change (IPCC) factors to estimate potential soil organic carbon (SOC) storage on U.S. agricultural land from widespread adoption of activities that are expected to increase SOC (e.g., remove highly erodible cropland from crop production, eliminate summer fallow, include winter cover crops in crop rotations, and widespread use of no-tillage). Previous land-use and management and the transitions between activities over three inventories are critical to the SOC estimates. The effects of these transitions between inventories are captured by using the ending SOC stock from the previous inventory for the SOC stock at the beginning of the next inventory. This approach increases the precision of SOC sequestration estimates based on the initial SOC stock, land-use and change in land-use, climate, soil characteristics, residue input, and soil disturbance. Total SOC storage during the final inventory is estimated to be 63.7TgCyr−1, with over half (35TgCyr−1) from new no-till management. The potential annual SOC accumulation could offset over half of the annual carbon dioxide (CO2) emissions from U.S. agriculture in 2010 and all of the 1990–2010 average annual increase in U.S. CO2 emissions. The approach provides more information than previous studies about the effect of land-use and tillage on SOC sequestration. No-till in the final inventory is estimated to accumulate 0.39MgCha−1yr−1 on cropland that was under reduced tillage the first inventory and conventional tillage the second inventory but 0.21MgCha−1yr−1 if the cropland was under reduced tillage the previous two inventories. This approach also captures the influence of soil characteristics on SOC sequestration. For example, land that was under continuous row crops prior to enrollment in the Conservation Reserve Program accumulated 0.39MgCha−1yr−1 on high activity mineral soils, but only 0.19MgCha−1yr−1 on sandy soils.