Assessing the impact of residue cover on hillslope soil loss in the Midwest US: insights from the daily erosion project modeling framework

Designing regionally resilient cropping systems requires understanding the interactions of multiple factors important to crop production and soil erosion-susceptibility both spatially and temporally. The objectives of this study were to elucidate the relationships between regional hillslope soil loss and Daily Erosion Project (DEP) tillage management scenarios and assess the sensitivity of hillslope soil loss to different field residue covers associated with these tillage scenarios. DEP simulations used the same tillage management scenario for the entire domain. Scenarios consisted of the six tillage categories within DEP (T1 to T6), with increasing values implying more intense tillage (less residue). Results indicated a direct relationship between tillage intensity (less residue cover) and higher erosion rates at different spatial scales (statewide, major land resource areas [MLRA], and DEP watersheds). The study also revealed a significant spatial variability across the DEP domain, identifying erosion-prone regions along the Missouri River and eastern Iowa and Minnesota, surpassing in many scenarios 17.9 Mg/ha/yr. Other areas showed no response associated with increasing tillage intensity, demonstrating how local factors such as topography, soil, land use, and climate and their interaction could also affect erosion. The sensitivity analysis uncovered a very high erosion sensitivity to small changes in residue cover, especially in hilly watersheds, while transitioning from no-till to tilled systems. Overall, this regional study underscores the importance of residue cover management and minimal soil disturbance in reducing hillslope erosion and illustrates the critical role landscape and management interactions play in spatially variable regional hill slope soil erosion rates.