Forage species and summer management impacts on soil carbon and nitrogen in winter stockpiled grazing systems

Abstract

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 two 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 permanganate‐oxidizable carbon (POXC) and 5–15 cm hot‐water extract ultraviolet absorbance at 254 nm (A254). Hot‐water extractable carbon, A254, 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.

Opportunities to increase soil carbon sequestration in grazing lands in the southeastern United States

“…Forage species and cropping systems also play a major role in controlling soil C accumulation (Allen et al, 2006; Rolando et al, 2021; Tilhou et al, 2021; Wang et al, 2014). Wang et al (2014), evaluating the effects of grass species and grazing intensity on soil C in North Carolina, reported that after 4 years, soils cultivated with annual ryegrass/sorghum–sudangrass contained ~20% more C (0–10 cm) than soils under annual ryegrass/bermudagrass.…”

“…This response was associated with greater above‐ and belowground biomass under N‐fertilized pastures, which likely favored soil C accumulation. In a 3‐year study in Tennessee, Tilhou et al (2021) evaluated C pools in stockpiled winter grazing systems with two summer management treatments (grazed or hayed) and three plant species (tall fescue, switchgrass, or a mixture of Indian grass and big bluestem). The authors reported that both the defoliation regimen and plant species affected soil C concentrations (0–5 cm).…”

“…Allen et al (2006) examined soil C responses 6 years following the conversion of cropland to either bahiagrass or rhizoma perennial peanut pastures and reported that soil C stocks increased by 26% (or the equivalent of ~0.4 Mg C ha −1 year −1 ). Forage species and cropping systems also play a major role in controlling soil C accumulation (Allen et al, 2006;Rolando et al, 2021;Tilhou et al, 2021;Wang et al, 2014). Wang et al (2014), evaluating the effects of grass species and grazing intensity on soil C in North Carolina, reported that after 4 years, soils cultivated with annual ryegrass/sorghum-sudangrass contained ~20% more C (0-10 cm) than soils under annual ryegrass/bermudagrass.…”

Diversity and abundance of bacterial and fungal communities in rhizospheric soil from smallholder banana producing agroecosystems in Kenya

“…The decline in soil health and fertility including biological degradation (organic matter) is a worrying trend and has the potential to lower productivity significantly. Constant monitoring of soil health status is an essential factor in processes of development of land management systems that ensure the sustainability of soil resources (Tilhou et al, 2021). In order to reclaim the damage to soil and ensure global agricultural sustainability, the identification of these stressors as well as development of sustainable methods such as bioremediation is important (Tahat et al, 2020).…”