|Rocateli, Alexandre - Oklahoma State University|
|West, Charles - Texas Tech University|
|Brye, Kristopher - University Of Arkansas|
|Popp, Michael - University Of Arkansas|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2017
Publication Date: 5/18/2017
Citation: Ashworth, A.J., Rocateli, A.C., West, C.P., Brye, K., Popp, M.P. 2017. Switchgrass growth and effects on biomass accumulation, moisture content, and nutrient removal. Agronomy Journal. 109:1-9.
Interpretive Summary: Renewable fuel standards have set requirements that sustainable biomass sources be used for ethanol conversion. Switchgrass is a native, perennial prairie grass that requires minimal fertilizer inputs and produces high biomass yields on marginal lands. However, data on seasonal trends in plant growth, composition, and nutrient removal are lacking for developing models for predicting optimal harvest times of switchgrass for bioenergy. A research team investigated the seasonal changes in feedstock quality and quantity, as well as soil and tissue moisture. Researchers found that biomass accumulation peaked late summer, with yields decreasing by at least 26% from September to February. Moisture content declined to levels appropriate for direct storage by mid-December. Desirable feedstock composition traits and a reduction in nutrient removal were observed late fall. Therefore, delaying harvests to late fall or winter will reduce fertilizer replacement the following year and improve energy density and moisture content of biomass, however, a trade-off in yield will occur. This study is of interest to scientists, extension personnel, agricultural producers, and the second-generation biofuel industry.
Technical Abstract: Temporal patterns of plant growth, composition, and nutrient removal impact development of models for predicting optimal harvest times of switchgrass (Panicum virgatum L.) for bioenergy. Objectives were to characterize seasonal trends in yield, tissue moisture, ash content, leaf area index (LAI), interception of photosynthetically active radiation (PAR), and macronutrient accumulation and losses. Plots were subjected to 12 single harvests May-February in 2009-2010 and 2010-2011. Biomass accumulation into late summer followed a sigmoidal function, reaching an asymptote at 14 Mg ha-1, concurrent with early seed filling. During both seasons, biomass yields decreased by 26 to 32% from September to February. Moisture content declined to levels appropriate for storage (less than or equal to 200 g kg-1, wet basis) by 15 December. Interception of PAR leveled off at 96% in late July 2009 and mid-June 2010, whereas LAI declined early July both years. Ash concentration decreased from 70 to 27 g kg-1 through August, then declined to 17 g kg-1 by February. Peak N uptake occurred August 2009 and July in 2010 (80 and 141 kg N ha-1, respectively). Potassium uptake peaked July 2009 (136 kg ha-1) and in June 2010 (180 kg ha-1). Phosphorus peaked in July and August 2009 and 2010 at 16 and 17 kg ha-1, respectively. Peak biomass yields occurred August-September when N and K uptake and moisture contents were still elevated. Delaying harvests to late fall or winter will reduce fertilizer replacement needs, ash content, and improve energy density and moisture content, but a trade-off in lignocellulosic yield will likely occur.