Redistribution of soil and soil organic carbon on agricultural landscapes

Authors: Ritchie, Jerry; McCarty, Gregory

Submitted to: Hydrological Sciences Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2008
Publication Date: 11/9/2008
Citation: Ritchie, J.C., McCarty, G.W. 2008. Redistribution of soil and soil organic carbon on agricultural landscapes. Hydrological Science Journal. 2008 CDROM.

Interpretive Summary: Soil organic carbon (SOC), Cesium-137, and soil redistributions of agricultural soils are significantly related. Eroding soils determined by the Cs-137 technique have significantly less SOC than soils in depositing areas. Our data suggest that soil redistribution patterns may be used to help understand SOC dynamics on agricultural landscapes. Different productivity and oxidation rates of SOC of eroded versus deposited soil would also contribute different patterns of SOC on the landscape. However, the strong significant relationships between soil redistribution and SOC concentrations in agricultural soils suggest that they are moving along similar physical pathways in agricultural ecosystems. A strong relationship was also found between terrain attributes (slopes, slope shapes and types) and SOC suggesting that models can be developed to predict patterns of soil redistribution and SOC on agricultural landscapes providing potential insights into management system that will enhance sequestration of carbon in agricultural ecosystems.

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 limited carbon sequestration on agricultural landscapes. This study investigates the relationship between SOC and soil redistribution patterns on agricultural landscapes using fallout Cesium-137 to determine patterns of soil redistribution. SOC and Cs-137 concentrations of soils were significantly correlated in our study areas. Soils in eroding areas 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 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 soils suggest that soil and soil organic matter are transported along similar physical pathways in 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 of understanding soil movement and redistribution patterns within a field or watershed for understanding soil carbon cycles in agricultural ecosystems