Comment on: Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi.

In a recent paper, Jach-Smith and Jackson (2020) used the 15 N natural abundance (δ15 N) of two sources of nitrogen (N), available soil N and N in AMF, and 15 N mass balance equations to calculate the amount of N transferred by arbuscular mycorrhizal fungi (AMF) to switchgrass (Panicum virgatum L.), a perennial grass (the host plant) used in a bioenergy system in the United States. The study was conducted under three levels of inorganic N addition treatments (0, 56, and 196 kg N ha-1 ), at two different sites, the Arlington Agricultural Research Center (ARL) in Arlington, Wisconsin, and the W. K. Kellogg Biological Station (KBS) in Hickory Corners, Michigan.