Soil organic matter (SOM) in managed grasslands have economic and environmental benefits. This experiment evaluated a stockpiled winter grazing system with two summer management treatments (grazing or hay harvest) and three forage species treatments: tall fescue (TF, Schedonorus arundinaceus Schreb.), switchgrass (SG, Panicum virgatum L.), and mixed big bluestem-Indiangrass [BBIG, Andropogon gerardii Vitman-Sorghastrum nutans (L.) Nash]. Soil was sampled on 18 dates (January 2016-July 2017) at

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... wo depths (0-5 and 5-15 cm) in 15 paddocks in central Tennessee. Total organic carbon and total nitrogen concentrations in 0-5-cm samples were greater in grazed paddocks relative to hay harvest, and greater in TF relative to BBIG and SG. Summer grazing also resulted in greater 0-5-cm permanganateoxidizable carbon (POXC) and 5-15 cm hot-water extract ultraviolet absorbance at 254 nm (A 254 ). Hot-water extractable carbon, A 254 , and POXC concentrations were reduced in SG soils compared with TF and BBIG. Summer hay harvests, compared with grazing, reduced hot-water extractable C/N in both soil horizons in TF. The interactions between management and plant species suggests contrasting nutrient cycling associated with TF and the morphologically different native grasses BBIG and SG. This study represents the first observations of soil impacts within stockpiled grazing systems and the first observations of grazed native grass species in the southeastern United States.