The Future of Soils in the Midwestern United States

Soil is the source of the vast majority of food consumed on Earth, and soils constitute the largest terrestrial carbon pool. Soil erosion associated with agriculture reduces crop productivity, and the redistribution of soil organic carbon (SOC) by erosion has potential to influence the global carbon cycle. Tillage strongly influences the erosion and redistribution of soil and SOC. However, tillage is rarely considered in predictions of soil erosion in the U.S.; hence regionwide estimates of both the current magnitude and future trends of soil redistribution by tillage are unknown. Here we use a landscape evolution model to forecast soil and SOC redistribution in the Midwestern United States over centennial timescales. We predict that present-day rates of soil and SOC erosion are 1.1 +/- 0.4 kg center dot m(--2) center dot yr(--1) and 12 +/- 4 g center dot m(-2) center dot yr(-1), respectively, but these rates will rapidly decelerate due to diffusive evolution of topography and the progressive depletion of SOC in eroding soil profiles. After 100 years, we forecast that 8.8 (+1.9/-2.1) Pg of soil and 0.17 (+0.03/-0.04) Pg of SOC will have eroded, causing the surface concentration of SOC to decrease by 4.4% (+0.9/-1.1%). Model simulations that include more widespread adoption of low-intensity tillage (i.e., no-till farming) determine that soil redistribution, SOC redistribution, and surficial SOC loss after 100 years would decrease by similar to 95% if low-intensity tillage is fully adopted. Our findings indicate that low-intensity tillage could greatly decrease soil degradation and that the potential for agricultural soil erosion to influence the global carbon cycle will diminish with time due to a reduction in SOC burial. Plain Language Summary Plow-based agriculture has accelerated soil erosion rates by one to two orders of magnitude, which diminishes crop productivity and has the potential to impact the carbon cycle. Using a numerical model, we calculate that present-day rate of soil and soil organic carbon (SOC) erosion are 1.1 +/- 0.4 kg center dot m(--2) center dot yr(--1) and 12 +/- 4 g center dot m(-2) center dot yr(-1), respectively and predict that 8.8 (+1.9/-2.1) Pg of soil and 0.17 (+0.03/-0.04) Pg of SOC will be eroded in the Midwestern United States over the next century. Compared to other measured rates of soil and SOC erosion, the predicted rates are relatively high and have the potential to degrade soil and influence the carbon cycle. With our model, we simulated the more widespread adoption of low-intensity tillage (i.e., no-till farming) and found that the full adoption of low-intensity tillage would reduce soil and SOC erosion by similar to 95% over the next 100 years. Therefore, our results indicate that further adoption of low-intensity tillage has the potential to greatly reduce soil and SOC erosion and contribute to soil sustainability.