|ZAIBON, SYAHARUDIN - University Of Missouri|
|ANDERSON, STEPHEN - University Of Missouri|
|HARUNA, SAMUEL - Middle Tennessee State University|
Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2019
Publication Date: 5/5/2019
Citation: Zaibon, S.B., Anderson, S.H., Veum, K.S., Haruna, S.L. 2019. Soil thermal properties affected by topsoil thickness in switchgrass and row crop management systems. Geoderma. 350:93-100. https://doi.org/10.1016/j.geoderma.2019.05.005.
Interpretive Summary: Growing perennial crops in place of annual row crops can provide many conservation benefits. For example, perennial vegetation has been shown to reduce soil erosion and improve soil characteristics, including soil-water dynamics, over traditional row crop production systems. However, the impact of perennial vegetation on thermal properties that affect the transfer and storage of heat in soil is not well understood. This study compared the thermal properties of soil with different topsoil thickness (1.5 and 14 inches) under perennial switchgrass and an annual, corn-soybean, row crop production system. Soil samples were collected at the University of Missouri South Farm Research Center from research plots established in 2009. Soil properties included thermal conductivity, volumetric heat capacity, and thermal diffusivity along with other soil characteristics. The results showed that the switchgrass system improved soil characteristics by increasing soil organic matter, increasing water content, and reducing bulk density relative to the row crop system. Furthermore, the switchgrass system also demonstrated lower thermal conductivity, lower heat capacity, and increased diffusivity. The results of this study also found that the shallow topsoil had increased thermal properties compared to the deeper topsoil, likely due to the increase in clay content. This study may contribute to a better understanding of the impact of topsoil loss and perennial vegetation on degraded land. Producers and land managers will benefit by understanding the role of perennial vegetation in maintaining or improving soil characteristics that can affect productivity and the environment.
Technical Abstract: Perennial systems such as switchgrass have been shown to improve soil hydraulic properties on degraded soils relative to annual cropping systems; however, studies of the effects on thermal properties are limited. Therefore, the objectives of this study were to determine the effects of topsoil thickness on soil thermal properties under switchgrass (Panicum virgatum L.) and row crop production systems. The experiment was carried out at the University of Missouri South Farm Research Center (38°54’ N, 92°16’ W). Research plots were re-established in 2009 with selected topsoil thickness categorized into two treatments (shallow [4 cm] and deep [36 cm]) on a Mexico silt loam (Vertic Epiaqualfs). Plots were planted to either switchgrass or a corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation with four replicates. Undisturbed soil cores (7.6 by 7.6 cm) and bulk soil were collected from two depths (10 cm increments) to determine thermal properties. Thermal conductivity, volumetric heat capacity, and thermal diffusivity were measured at 0, -33, -100 and -300 kPa soil water pressures. In addition, soil organic carbon (SOC), bulk density, and water content were also determined. The results showed that the switchgrass treatment had 23% higher SOC, 5 – 8% greater water content, and 11% lower bulk density than the row crop treatment. In turn, switchgrass exhibited a 5-7% reduction in thermal conductivity, an 8-9% reduction in thermal diffusivity, and a 2-3% increase in volumetric heat capacity. Shallow topsoil thickness demonstrated increased thermal properties relative to the deep topsoil thickness, likely due to higher clay content. This study contributes to a better understanding of the impact of topsoil loss and perennial vegetation on the thermal properties of soils in degraded landscapes.