Impacts of nitrogen fertilization rate and landscape position on select soil properties in switchgrass field at four sites in the USA

Abstract Switchgrass ( Panicum virgatum L.) has been recognized as a potential bioenergy feedstock due to its high yield potential and benefits to the environment. However, little is known about the impacts of nitrogen fertilization and landscape position on soil properties in switchgrass fields at multiple locations in the USA. The objective of this study was to assess the impacts of application of nitrogen fertilization rate (N rate; zero, 0; medium, 56; and high, 112 kg ha −1 ) and landscape position (shoulder, backslope, and footslope) on soil pH, electrical conductivity (EC), soil organic carbon (SOC), total nitrogen (TN), nitrate-N (NO 3 − -N), and ammonium-N (NH 4 + -N). This experiment was established in 2008 at four sites in Oklahoma (OK), South Dakota (SD), New York (NY), and Virginia (VA). Data showed that the N rate significantly increased NO 3 − -N for the 0–5 and 5–15 cm depths at the SD, NY, and VA sites. Compared with the zero N rate, the high N rate averagely increased NO 3 − -N by 75.7% for the two depths and three sites. The SOC and TN increased with the increase in N rate at most of the depths. The landscape position significantly reduced soil pH and increased EC, SOC, TN, NO 3 − -N, and NH 4 + -N at the footslope compared with the shoulder and backslope positions in most depths at the SD site (no position data at the NY and VA sites). The pH generally increased and the SOC, TN, and NO 3 − -N reduced with the increase in soil depth. These findings indicate that switchgrass production has the potential to improve or maintain soils in the USA.