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

Abstract

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.