Changes in Nutrient Characteristics of Switchgrass for Bioenergy

Abstract

Switchgrass (Panicum virgatum L.) was identified as a “model” bioenergy crop by the USDOE in 1991. Since then, there has been little research to understand changes in switchgrass quality during the growing season or the effect that drought may have on these quality characteristics. This study determined changes in total N, P, K, S, Ca, Mg, moisture concentration, and dry weight yield through intensive sampling during the growing season. Subsamples from a one‐cut system were harvested on 13 different dates in 2011 and eight different dates in 2012 between late May and early November. Low rainfall in late spring and early summer 2012 created drought conditions that led to some differences between years. In general, the measured variables decreased with time, but dry weight yield increased in both years and peaked around late August. In 2011, a significant rise in N between late July and mid‐August may have been caused by reproductive growth and/or organic matter mineralization, although this has not been documented elsewhere. Differences between normal (2011) and drought (2012) conditions included lower biomass production, reduced N concentrations, increased S and P concentrations in late August, and increased plant moisture in late August and October under drought conditions. Years with drought conditions may allow more staggered harvesting because nutrient ranges are smaller. This will allow a more continuous supply of feedstock to the biorefinery. These data and future economic analyses will allow better decision‐making opportunities for producers.

Switchgrass Cultivar, Yield, and Nutrient Removal Responses to Harvest Timing

“…These data suggests that in some years, detrimental yield impacts may occur from earlier post-senescence harvests removing carbohydrate reserves. These results support those reported by Parrish et al (2003), de Koff and Allison (2015), and Gorlitsky et al (2015).…”

Evaluation of eastern gamagrass as dual‐purpose complementary bioenergy and forage feedstock to switchgrass

“…We found significant differences in biomass yield and other variables among the 3 years in this study. Variation in biomass yield among years has been reported by many previous studies (e.g., de Koff & Tyler, 2011; Ritchie et al, 2006; Rushing, Lemus, White, et al, 2019). Maughan (2011) found that SG biomass yield averaged 6.6 ± 3.0 Mg ha −1 during the establishment year, increased to 9.1 ± 5.5 Mg ha −1 in the second year, and reached a maximum of 10.9 ± 5.2 Mg ha −1 in the third year, in a meta‐analysis including 106 sites from 45 studies.…”

Differential effects of warming and nitrogen fertilization on soil respiration and microbial dynamics in switchgrass croplands

“…The switchgrass stands were located at the Tennessee State University Agricultural Research and Education Center, Ashland City, Tennessee. The site occupies Lindside silt loam soil (fine‐silty, mixed, mesic Fluvaquentic Eutrochrepts; de Koff & Allison, ). On the year prior to planting switchgrass in 2012, the field site was left fallow.…”