Using Fallout Cesium-137 to understand soil redistribution over agricultural landscapes

Authors: Ritchie, Jerry; McCarty, Gregory

Submitted to: International Soil Conservation Organization (ISCO)
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2008
Publication Date: 5/1/2008
Citation: Ritchie, J.C., McCarty, G.W. 2008. Using fallout Cesium-137 to understand soil redistribution over agricultural landscapes. In: Proceedings of the International Soil Conservation Organization Conference (ISCO2008) Congress, May 18-23, 2008, Budapest, Hungary. 2008 CDROM.

Interpretive Summary: Cesium-137, soil redistributions and SOC concentrations of agricultural soils were significantly related in Iowa and Maryland fields. Eroding soils determined by the Cs-137 technique have significantly less SOC than soils in deposition 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 these agricultural soils suggest that they are moving along similar physical pathways in these agricultural ecosystems. A strong relationship was also found between terrain attributes (slopes 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: While it is recognized that soil erosion is highly variable in space and time, studies of the redistribution of soil and soil organic carbon (SOC) within a field or watershed are limited. Our studies focus on the use of fallout Cesium-137 to understand pattern of soil and SOC movement on the landscape. It is often assumed that eroding soils results in soil losses from agricultural fields; however, our studies indicate that most of the eroding soils are redeposited within same field. These studies also investigated the relationship between soil redistribution and SOC patterns in agricultural fields. Cesium-137, soil, and SOC redistribution in agricultural fields were significantly correlated. Hillslope areas lost significantly more soil and SOC than soils in toe slope positions (deposition). Soil erosion increased as the slope increases and soils on concave slopes had higher SOC than soils on convex slopes. These data suggest that soil and SOC redistribution patterns and topographic patterns can be used to help understand soil erosion and SOC redistribution patterns on agricultural landscapes. The strong significant relationships between soil and SOC redistribution patterns in agricultural soils suggest that they are moving along similar physical pathways in these systems. Our study also indicates that geomorphic position is important for understanding soil and SOC movement and redistribution patterns within a field or watershed. Such information can help develop and implement management systems to increase SOC and reduce soil loss in agricultural ecosystems.