Redistribution of soil and soil organic carbon on agricultural landscapes

Authors: Ritchie, Jerry; McCarty, Gregory

Submitted to: International Association of Hydrological Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2008
Publication Date: 11/9/2008
Citation: Ritchie, J.C., McCarty, G.W. 2008. Redistribution of soil and soil organic carbon on agricultural landscapes [abstract]. International Association of Hydrological Science. 2008 CDROM.

Interpretive Summary:

Technical Abstract: Patterns of soil organic carbon (SOC) vary widely across the landscape leading to large uncertainties in the SOC budgets for agricultural systems especially for landscapes where water, tillage, and wind erosion redistributes soil and SOC across the landscape. It is often assumed that soil erosion results in a loss of SOC from agricultural ecosystems, but recent studies indicate that soil erosion on agricultural landscapes is not a source of carbon dioxide to the atmosphere but that soil erosion and its subsequent redistribution within agricultural fields and watersheds can lead to carbon sequestration on agricultural landscapes. This study investigates the relationship between SOC and soil redistribution patterns on agricultural landscapes using the fallout Cesium-137 technique to determine patterns of soil redistribution. Cs-137 and SOC concentrations of soils are significantly correlated in our study areas. Soils in upland areas (eroding) have significantly less SOC than soils in depositional areas. SOC decreased as gradient slope increases and soils on concave slopes had higher SOC than soils on convex slopes. These data suggest that soil redistribution patterns and topographic patterns may be used to help understand SOC dynamics on the landscape. The strong significant relationships between soil redistribution and SOC concentrations in the upland soil suggest that soils and soil organic matter are transported along similar physical pathways in these upland agricultural systems. These transport processes move soils and SOC to sites of deposition within agricultural fields, riparian zones, and water bodies in the watershed where SOC is buried leading to more carbon being removed from the atmosphere than is emitted, creating a sink of atmospheric carbon. Our study indicates the importance for understanding soil movement and redistribution patterns within a field or watershed for understanding soil carbon cycles in agricultural ecosystems.