The Characterization of Dynamic Soil Properties and Their Relation to Soil Organic Carbon in East Tennessee Soils

Quantifying how dynamic soil properties (DSPs) are affected by different management regimes is essential for understanding how these vital resources can be better managed. The Dewey soil series is a critical soil series in East Tennessee. For this study, the University of Tennessee, Knoxville (UTK) worked alongside the National Cooperative Soil Survey (NCSS) in an effort to better understand the dynamics of the Dewey soil series through a wide range of DSP data. To accomplish this, Dewey soil was collected from five sites which are considered representative of five management regimes: well-managed cropland (WMC), poorly-managed cropland (PMC), well-managed pasture (WMP), poorly-managed pasture (PMP), and a reference state (RS). At UTK, the samples were analyzed for 15 DSPs, and a duplicate set of samples were analyzed at the University of Missouri Soil Health Assessment Center for 8 additional DSPs. The resulting data were analyzed using structural equation modeling (SEM) to quantify the relationships between each analyzed DSP. The goal of this study was to answer the following questions: How do soil organic carbon (SOC) stocks differ between each of the five represented management regimes, which DSPs are the most important controls on SOC, and which management regimes will promote the lowest levels of microbial sensitivity to temperature change? ANOVA and Tukey’s HSD analyses were run on the SOC and Q₁₀ values for the surface soil samples by site. The only significant difference in SOC was between the RS and PMC sites (p=0.0382), and the WMP site was found to have a significantly lower mean Q₁₀ than all other sites. The SEM produced by this study shows significant predictive relationships between SOC and Total Nitrogen, Potentially Mineralizable Nitrogen, Microbial Biomass Carbon, and pH with direct path coefficients of 0.61, 0.24, 0.24, and -0.06 respectively. The DSP found to have the strongest total effect on SOC was POXC, which was also found to have a strong one-on-one correlation with SOC. This implies that while POXC was not found to have a direct relationship with SOC, it can still be used as an indicator for SOC in Dewey soil.