Developmental morphology, biomass yield and compositional differences among upland and lowland switchgrass (Panicum virgatum L.) ecotypes grown as a bioenergy feedstock crop

Sustainable and successful development of the bioenergy industry strongly depends upon the amount and quality of bioenergy feedstock produced. Switchgrass (Panicum virgatum L.) has been identified as a model lignocellulosic bioenergy crop in the U.S. Information regarding its growth and development is considered critical for making management decisions, production of high quality feedstock and to support simulation model calibration and subsequent analysis. In the first study (Chapter 2), we evaluated upland (‘Cave-in-Rock’, ‘Trailblazer’ and ‘Blackwell’) and lowland (‘Kanlow’ and ‘Alamo’) ecotypes of switchgrass for harvest management, morphological (phenology and leaf area index) and biomass yield differences. A field study was conducted near Ames, IA during 2012 and 2013. The experiment design was a randomized complete block design. Six in-season destructive biomass harvests were collected at approximately 2-week intervals each year. In both years, delaying harvest to later maturity increased biomass yield in all cultivars. Averaged over years lowland cultivars ‘Kanlow’ and ‘Alamo’ produced higher dry matter yield (6.31 and 5.98 tons ha, respectively) than upland ecotypes ‘Cave-in-Rock’, ‘Trailblazer’ and ‘Blackwell’ (5.89, 4.78 and 4.53 tons ha, respectively). Lowland cultivars had delayed reproductive development compared with upland ecotypes. The widely recommended cultivar in Iowa ‘Cave-in-Rock’ had the highest mean stage count and leaf area index at the end of both growing seasons, but did not produce the greatest biomass. There was a nonlinear relationship between MSC and biomass yield. However, the magnitude and form of the response was different between cultivars and from year to year.