Rates of Historical Anthropogenic Soil Erosion in the Midwestern United States

Abstract

Conventional agricultural practices have accelerated soil erosion rates, resulting in widespread soil degradation throughout the world's agricultural regions (Montgomery, 2007b). Soil degradation diminishes soil fertility by removing organic matter and nutrients (Pimentel, 2006), which, without countervailing practices such as fertilization and genetic crop enhancements, leads to reductions in crop yields (Lal, 2004;Tilman et al., 2002). Fertilizer use, however, does not fully restore the productivity of eroded soils (Fenton et al., 2005), and because fossil fuels are required to generate the energy required for fertilizer production, the use of fertilizers to increase yields in degraded soils is not sustainable (Montgomery, 2007a). Further, soil erosion leads to increased agricultural production costs (Pimentel et al., 1995) and negative offsite effects such as increased sedimentation and nutrient export to downstream waterbodies (Tilman et al., 2002). In the United States, recognition of the high costs of soil erosion in the early twentieth century led to the development and implementation of soil conservation practices (Bennett, 1948). Field trials have demonstrated the efficacy of soil conservation efforts (Pimentel et al., 1976;Steiner, 1987), but it is unclear whether the advent of soil conservation practices and policies has led to a reduction of region-wide soil erosion rates in the U.S.

The Future of Soils in the Midwestern United States

“…Our findings and those of others suggest there has been substantial burial of SOC within the Midwestern U.S. (Li et al., 2018; Papiernik et al., 2009; Smith et al., 2001; Young et al., 2014). Given that a large extent of the Midwestern U.S. has soils where SOC stocks have been degraded (Thaler et al., 2021, 2022), there is potential to restore agricultural soils via regenerative practices (Montgomery, 2017; Schneider et al., 2021). Whether adoption of no‐till farming can also return atmospheric SOC to soils is a matter of debate; field trials have shown that no‐till farming can increase SOC (Kumar et al., 2012; West & Post, 2002) and regionwide studies and compilations have shown that no‐till increases SOC in upper soil horizons (Christopher et al., 2009; Luo et al., 2010; Nunes et al., 2020).…”

“…The inclusion of dynamic replacement in our model would increase the amount of eroded SOC because SOC concentration in the actively eroding areas would be partially replenished. However, dynamic replacement seems to play a small role compared to erosional SOC transport in the Midwestern U.S. because there is a widespread and persistent absence of A-horizon soils on the hilltops (Thaler et al, 2021(Thaler et al, , 2022, which indicates SOC loss via erosion far outpaces its replacement by crops. Additionally, Kwang, Thaler, Quirk, et al (2022) found that the spatial pattern of SOC erosion can be reproduced by soil transport dynamics alone, which is also consistent with SOC reduction via soil erosion greatly outpacing dynamic replacement.…”

“…The dashed red line denotes the maximum ice sheet extent during the Last Glacial Maximum (Dalton et al, 2020). led to a drastic acceleration in erosion rates (Quarrier et al, 2022;Thaler et al, 2022) and the removal of roughly one-third of the A-horizon soils from agricultural fields (Thaler et al, 2021). Soil degradation in the region is estimated to reduce crop yield by 6%, leading to $2.8 billion in economic losses annually (Thaler et al, 2021).…”

“…Over the 660-year simulation, 45%-52% of SOC erosion and 40%-47% of SOC burial occur between 1860-2020. Although a large portion of SOC has been lost from upper soil horizons (Thaler et al, 2021(Thaler et al, , 2022, there is still SOC that is vulnerable to future erosion. Between 1860-2020, surficial SOC declines by 12%-15%, and between 2020 and 2520, it declines by 16%-26% (Figure S9a in Supporting Information S1).…”

Farmer perceived challenges toward conservation practice usage in the margins of the Corn Belt, USA

“…In the USA, current intensive agricultural production has led to undesirable effects on the environment and a gradual decrease in land productivity (Kassam et al ., 2014; McDaniel et al ., 2014; Benitez et al ., 2017). The average soil loss over the last 100 yr of crop cultivation across the Midwest has been estimated to be 7.2 ± 4.8 Mg ha −1 yr −1 (Thaler et al, 2022). Historic and modern soil erosion reduces cropland productivity and agroecosystem resiliency.…”