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Research Project: Strategies to Predict and Mitigate the Impacts of Climate Variability on Soil, Plant, Animal, and Environmental Interactions

Location: Plant Science Research

Title: Soil carbon fractions from an alluvial soil texture gradient in North Carolina

item Diess, L - Universidade Federal Do Parana
item Franzluebbers, Alan
item Amoozegar, A - North Carolina State University
item Polizzotto, M - North Carolina State University
item Hesterberg, Dean - North Carolina State University
item Cubbage, F - North Carolina State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2017
Publication Date: 10/12/2017
Citation: Diess, L., Franzluebbers, A.J., Amoozegar, A., Polizzotto, M.L., Hesterberg, D.L., Cubbage, F.W. 2017. Soil carbon fractions from an alluvial soil texture gradient in North Carolina. Soil Science Society of America Journal. 81:1096-1106.

Interpretive Summary: Carbon-depleted agricultural soils are a threat to the sustainability of food production and environmental quality worldwide. Improving soil organic carbon concentration is a potential path towards mitigation of soil erosion, water quality deterioration, biodiversity loss, and greenhouse gas emissions. A USDA-Agricultural Research Service scientist in Raleigh, North Carolina collaborated with scientists at North Carolina State University and University of Parana to evaluate variations in soil organic carbon fractions in a flood-plain soil on the Coastal Plain of North Carolina. A natural soil texture gradient at the site revealed that soil organic carbon stabilization was promoted by reactive surfaces of the fine fraction of soil. Binding to clay minerals and iron oxyhydroxides possibly contributed to accumulation of soil organic carbon and suppression of carbon mineralization as clay concentration increased. Understanding these relationships in space and time and the relationship between mineralizable organic carbon and nitrogen will allow us to develop field-specific management strategies, such as variable-rate application of nitrogen fertilizers. These results will inform scientific understanding to be able to improve nutrient application recommendations for farmers throughout the region.

Technical Abstract: Soil texture is known to affect soil organic carbon (SOC) concentration and soil microbial activity, but sources of clay could result in different relationships. We characterized total organic C, mineral-associated organic C (MAOC), and the flush of CO2 following rewetting of dried soil (as a proxy of potential soil microbial activity) along a gradient of soil texture within a flood plain field in the Coastal Plain of North Carolina. Soil samples were collected from 0-5, 5-15, and 15-30 cm depth intervals at 204 locations within a 7-ha area. The samples were analyzed for soil texture, specific surface area (SSA) and oxalate-extractable Al and Fe to estimate poorly crystalline (pxl) oxyhydroxides. Linear and segmented regression models were used to relate SOC, MAOC and the flush of CO2 with other measured soil properties. Overall, relationships between soil C fractions and textural classes were complex. Both SOC (0.4-13.9 g kg-1) and MAOC (0-12 g kg-1) increased as soil clay concentration increased (73-430 g kg-1), but trends were not uniform with clay concentration and depth. As clay concentration increased, SSA (12-76 g m-2) and pxl Fe oxyhydroxides (0.45-5.9 g kg-1) also increased. A weaker relationship was observed between pxl Al oxyhydroxides (0.38-1.5 g kg-1 soil) and SSA or MAOC. The flush of CO2 increased with increasing clay concentration up until 143-161 g kg-1, but decreased at higher clay concentrations. Physical isolation and binding to clay minerals and pxl Fe oxyhydroxides possibly contributed to accumulation of SOC and suppression of the flush of CO2 as clay concentration increased.