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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #317881

Title: From soilscapes to landscapes: A landscape-oriented approach to simulate soil organic carbon dynamics in intensively managed landscapes

item PAPANICOLAOU, A - University Of Tennessee
item WACHA, KENNETH - University Of Iowa
item ABBAN, BENJAMIN - University Of Tennessee
item WILSON, CHRISTOPHER - University Of Tennessee
item Hatfield, Jerry
item STANIER, CHARLES - University Of Iowa
item FILLEY, TIMOTHY - Purdue University

Submitted to: Journal of Geophysical Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2015
Publication Date: 11/23/2015
Citation: Papanicolaou, A.N., Wacha, K.M., Abban, B.K., Wilson, C.G., Hatfield, J.L., Stanier, C., Filley, T. 2015. From soilscapes to landscapes: A landscape-oriented approach to simulate soil organic carbon dynamics in intensively managed landscapes. Journal of Geophysical Research. 120:2375-2401.

Interpretive Summary: Soils change across a landscape as a result of movement of soil from the higher elevations to the lower elevations as a result of erosion. A critical component to understanding these processes is the amount of organic material contained in the soil and how these materials interact with water erosion. We developed a model to simulate the processes of erosion across a landscape to more fully understand the interactions of soil organic carbon in soil with crop and tillage management and found that practices that increased the erosion reduced the soil organic matter content. This trend was reversed when there was adoption of conservation tillage and increased crop productivity which supplied more organic matter into the soil. The ability to provide detailed estimates of the interactions between crop management practices and soil management across a landscape allows for a more detailed assessment of management practices that can protect the soil from erosion and restore soil organic matter. This information will be valuable to scientists and natural resources managers to understand these complex interactions which occur in agricultural fields.

Technical Abstract: Most available biogeochemical models focus within a soil profile and cannot adequately resolve contributions of the lighter size fractions of organic rich soils for Enrichment Ratio (ER) estimates, thereby causing unintended errors in Soil Organic Carbon (SOC) storage predictions. These models set ER as constant, usually equal to unity. The goal of this study is to provide spatiotemporal predictions of SOC stocks at the hillslope scale that account for the selective entrainment and deposition of lighter size fractions. It is hypothesized herein that ER values may vary depending on hillslope location, Land Use/ Land Cover (LULC) conditions, and magnitude of the hydrologic event. An ER module interlinked with two established models, CENTURY and WEPP, is developed that considers the effects of changing runoff coefficients, bare soil coverage, tillage depth, fertilization, and soil roughness on SOC redistribution and storage. In this study, a representative hillslope is partitioned into two control volumes (CVs): a net-erosional upslope zone and a net-depositional downslope zone. We first estimate ER values for both CVs I and II for different hydrologic and LULC conditions. Second, using the improved ER estimates for the two CVs we evaluate the effects that management practices have on SOC redistribution during different crop rotations. Overall, LULC promoting less runoff generally yielded higher ER values, which ranged between 0.97-3.25. Eroded soils in the upland CV were up to 4% more enriched in SOC than eroded soils in the downslope CV due to larger interrill contributions, which were found to be of equal importance to rill contributions. The chronosequence in SOC storage for the erosional zone revealed that conservation tillage and enhanced crop yields begun in 1980s reversed the downward trend in SOC losses, causing nearly 26% of the lost SOC to be regained.