LB 7-68 - Carbon and nitrogen dynamics in Miscanthus x giganteus biomass crop over a decade

Background/Question/Methods:

Miscanthus x giganteus (miscanthus) is a perennial rhizomatous grass with a C4 photosynthetic pathway. It is considered an ideal biomass energy crop because of its carbon (C) sequestration potential, water use efficiency, and low fertilizer requirements. The objective of this study was to measure the potential for C sequestration on degraded and abandoned agricultural land, the change in plant and soil nitrogen (N) over a decade, and the photosynthetic capacity in the tenth year of growth. The study was conducted on six replicate 10x10 m² miscanthus plots at two sites in southeast Ohio. One site (A) was previously a pasture, and the other site (B) was managed for hay. Soil samples were collected to a depth of 30 cm before and after planting in 2013 and will be resampled in 2022 and 2023. New soil samples will be dried, ground and wrapped for analysis in a CN elemental analyzer (Costech; Valencia, CA). Harvested biomass over seven years (2015-2022) was also sampled, weighed, dried, and the tissue composition of biomass was measured. Diurnal photosynthesis measurements will be made in 2022 and reported in this presentation.

Results/Conclusions:

The amount of C and N in soils measured in 2013 at site A was 22.8 Mgha^-1 and 2.29 Mgha^-1, respectively, and 27.8 Mgha^-1and 2.81 Mg ha^-1 at site B. The mean C and N percentage in the harvested plant biomass in 2015 (41.0 %C and 1.88 %N) was not significantly different (p > 0.05) from that of 2016 (43.9 %C and 1.43 %N). Subsequent plant samples in 2018 had lower N concentration than in prior years (47.2 %C and 0.34 %N). Soil conditions measured in the tenth year of crop growth will be compared to initial soil conditions (from 2013) to determine the magnitude of C sequestration that occurred over the last decade. Changes in soil N and plant tissue composition over seven years of harvest will also be described. Ultimately, this presentation will address the net environmental benefit of using a perennial grass as a dedicated biomass crop relative to (i) an annual row cropping systems with large input requirements or (ii) unmanaged abandoned agricultural land.