Jach-Smith, L. C. and R. D. Jackson. 2020. Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi. Ecological Applications 30:e02047.

Arbuscular mycorrhizal fungi (AMF ) provide many benefits in agroecosystems including improved soil tilth, carbon sequestration, and water and nutrient transfer to plants. AMF are known to affect plant nitrogen (N) dynamics and transfer N to plants, but there have been few studies addressing whether the amount of N transferred to plants by AMF is agronomically relevant. We used δ15N natural abundance methods and δ15N mass balance equations to estimate the amount of plant N derived from AMF transfer in perennial grasses managed for bioenergy production under different N addition treatments (0, 56, and 196 kg N/ha). Differentiation of δ15N among plant, soil N, and AMF pools was higher than anticipated leading to calculations of 34–55% of plant N transferred by AMF in the treatments receiving no N addition to 6–22% of plant N transferred to plants in high‐N addition treatments. AMF extra‐radical hyphae biomass was significantly reduced in the high‐N (196 kg N/ha) addition treatments, which was negatively correlated to enriched plant δ15N. Our results suggest that N addition decreases AMF N transfer to plants. When N was limiting to plant growth, AMF supplied agronomically significant amounts of plant N, and a higher proportion of overall plant N. Because differentiation between N pools was greater than expected, stable isotope measurements can be used to estimate N transfer to AMF plant hosts.

DOI: 10.1002/eap.2047

Data URL: https://doi.org/10.5061/dryad.31zcrjdgb

Associated Treatment Areas:

• Switchgrass Nitrogen/Harvest Experiment - GLBRC

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