05/26/2020
Nitrogen Cycling in Switchgrass Varieties
The Science
Determine differences in nitrogen (N) acquisition and conservation between switchgrass varieties to optimize growth with the least amount of fertilizer usage by measuring N fixation, N mineralization, and N translocation along with soil moisture and N content in switchgrass varieties from upland and lowland ecotypes.
The Impact
- N fixation was highly variable among switchgrass varieties, but in general lowland ecotypes had significantly higher yields, N translocation, and root N fixation, with lower soil N fixation than upland ecotypes.
- N cycling differences might be due to root and soil microbiome differences in switchgrass varieties.
- Many switchgrass varieties can achieve high yield without N additions, decreasing the economic and environmental cost of growing this bioenergy crop.
Summary
In nitrogen (N)-limited terrestrial ecosystems, plants employ various strategies to acquire and conserve N, including translocation of N in perennial tissues and stimulation of N fixation in roots and soils. Switchgrass (Panicum virgatum L.) is a genotypically and phenotypically diverse perennial grass with two distinct ecotypes (lowland and upland) and numerous genotypes. It grows well in low-N soils, likely because of its ability to translocate N and to associate with N-fixing microbes, but little is known about variation in these traits among cultivars or even ecotypes. We measured N translocation, N fixation potential in roots and soils, soil net N mineralization, soil net nitrification, and biomass yields in 12 switchgrass cultivars grown in a replicated block experiment in southwestern Michigan, USA. Lowland cultivars had higher yields, rates of N translocation, soil net N mineralization, and N fixation potentials on washed, non-sterile roots, while upland cultivars exhibited higher N fixation potentials in root-free soil.
References
Roley, S.S., T. C. Ulbrich, and G. P. Robertson. 2020. “Nitrogen Fixation and Resorption Efficiency Differences Among Twelve Upland and Lowland Switchgrass Cultivars,” Phytobiomes 116, 071802. DOI:10.1094/PBIOMES-11-19-0064-FI.