Biomass Production of Monocultures and Mixtures of Cup Plant and Native Grasses on Prime and Marginal Cropland

To date, most candidate systems for producing herbaceous cellulosic biomass have been composed of monocultures of perennial or annual grasses. Ecosystem goods and services provided from these biomass feedstock production systems could be increased dramatically with mixing of one or more forb species that would increase biodiversity and provide habitat for pollinators. Cup plant (Silphium perfoliatum L.) is featured with many desirable characteristics, such as high biomass potential, adaptation to marginal soils, and attractiveness to pollinators, desirable in a dicot species to grow in mixtures with perennial warm-season grasses. The objective of this study was to compare cup plant, switchgrass (Panicum virgatum L.), and prairie cordgrass (Spartina pectinata Link) monocultures to their mixtures for biomass production on prime and poorly drained marginal crop land for two years in both South Dakota and Wisconsin. In Wisconsin, monocultures of prairie cordgrass and cup plant and their mixture produced more biomass (8.1 Mg·ha-1) than the switchgrass monoculture and switchgrass/cup plant mixture (5.3 Mg·ha-1) on both prime and marginal land. While in South Dakota, drought and meristem destruction by the cup plant moth (Eucosma giganteana Riley) caused large reductions in biomass production (1.7 Mg·ha-1) in both years, with the switchgrass/cup plant mixture on marginal land having the highest yield (2.1 Mg·ha-1). Our study showed binary mixtures of cup plant and native warm-season grasses have great potential for increasing biodiversity and other ecosystem goods and services, relative to monocultures, for sustainable biomass feedstock production on poorly drained marginal land in the northcentral USA.

Biomass Production of Cup Plant (<i>Silphium perfoliatum</i>L.) in Response to Variation in Plant Population Density in the North Central USA

The North American genus Silphium is receiving global attention for its potential in the development of new food, forage, and industrial crops, including cellulosic biomass for biofuel. Little is known about the effect of plant population density on biomass production in large, coarse perennial forbs. Our objective was to evaluate the effect of variation in plant density on biomass production and stand morphology of cup plant (Silphium perfoliatum L.). Plant population densities of 17,000, 34,000, and 68,000 plants ha-1 were evaluated for biomass production in a single-harvest per annum system for three years at Brookings, SD and Arlington, WI. Biomass increased linearly by 43% between the low and high density at Brookings;whereas, at Arlington, response to variation in plant density was year dependent. Shoots plant-1 was inversely related to plant density with linear regression explaining >95% of the variation. Our results strongly suggested that further studies of effects of plant population density on biomass production in cup plant should include evaluation of, in addition to, densities higher than 68,000 plants ha-1.

Genetic Variation for Biomass and Related Morphological Traits in Cup Plant (<i>Silphium perfoliatum</i>L.)

Cup plant (Silphium perfoliatum L.) has demonstrated potential for bioenergy production in North America, South America, and Europe. Our objectives were to: 1) determine genetic variation and narrow-sense heritability for biomass and related morphological traits, and 2) identify half-sib families with superior biomass yield and potential for use in cultivar development in cup plant. Thirty three half-sib families and a check were evaluated at two locations in 2011, 2012, and 2013. Annual biomass yield at Brookings ranged from 2183 kg·ha-1 in 2012 to 8053 kg·ha-1 in 2013;whereas, yields at Arlington were similar among years. Mean individual half-sib family biomass yield ranged from 3912 to 6784 kg·ha-1 at Brookings and from 5682 to 11,269 kg·ha-1 at Arlington. Heritability estimates for five biomass-related morphological traits ranged from 0.52 to 0.72. This cup plant population had potential for biomass production in the north central USA and contained sufficient additive genetic variation to expect progress from among-and-within-family selection for biomass yield and related traits.