Seasonal Changes in Shoot and Root Nitrogen Distribution in Switchgrass (Panicum virgatum)

Project Author
Issue Date
Wayman, Sandra
Bowden, Richard D.
Mitchell, Robert B.
Thumbnail Image
First Reader
Additional Readers
Bioenergy , Biofuel , Harvest , Nitrogen retranslocation , Panicum virgatum , Switchgrass
Switchgrass is a promising bioenergy source that is perennial, productive, native to a broad geographic region, and can grow on marginal, nitrogen (N)-poor soils. Understanding N dynamics in switchgrass is critical to predicting productivity, conserving N, and optimizing the timing of harvest. We examined seasonal changes in N distribution in above- and belowground tissues in switchgrass to quantify N retranslocation rates. Above- and belowground biomass from three sites (two in PA and one in NE) were collected and analyzed for biomass growth and N concentrations at 30-day intervals from June through October. Total living plant mass ranged from 10.3 ± 2.4 standard error (SE) to 14.9 ± 2.5 SE Mg ha−1. Belowground mass comprised 52–57 % of total mass. Blades had the highest N concentration during summer, ranging from 6 to 22 g kg−1 N. Aboveground N concentrations decreased from September until autumn senescence, whereas belowground N concentration increased from August until senescence. Across the sites, total N retranslocated from aboveground to belowground components between September and October averaged 16.5 ± 7.1 (SE) kg ha−1 N representing 26.7 % of the average maximum N content of aboveground biomass. Based on N fertilizer costs, delayed harvest would conserve some N and provide financial savings on fertilizer ($9 ha−1) if harvest occurs after senescence but before overwinter biomass loss. However, biomass losses of even 10 % will negate potential economic savings accrued from N retention. To maximize environmental and economic savings from N retranslocation and to simultaneously minimize harvest losses, it would be optimal to harvest switchgrass as soon as possible after complete senescence.
Environmental Science / Studies
This article is a U.S. Government work, and is not subject to copyright in the United States.
Wayman, Sandra, Richard D. Bowden, and Robert B. Mitchell. 2014. "Seasonal Changes in Shoot and Root Nitrogen Distribution in Switchgrass (Panicum virgatum)."BioEnergy Research 7, no. 1: 243-252.
Published article
Springer US