Switchgrass Rhizosphere Microflora Community Structure and Nutrient Acquisition As a Function of Nitrogen and Cultivar.

Biofuel production using native perennial grasses such as switchgrass (Panicum virgatum L.) can reduce U.S. dependence on foreign oil and curtail greenhouse gas emissions. Moreover, switchgrass can be grown on fragile or low-productivity soils, providing valuable ecosystem services such as topsoil retention and nutrient loss reduction. This study quantifies switchgrass biomass production as a function of nitrogen application at two marginal sites in Minnesota, using three cultivars that differ greatly in origin and production characteristics: ‘Shawnee’ is a standard productive forage variety selected out of ‘Cave-in-Rock’ switchgrass, whose germplasm originated in southern Illinois; ‘Sunburst’ is an extremely hardy northern forage variety that was selected out of seed originating in Union County, South Dakota, with excellent seedling vigor and high germination rate; and ‘Liberty’ is a new bioenergy-type F1 hybrid of ‘Summer’ and ‘Kanlow’, bred for winter hardiness, yield, and low stem lignin. This study also uses metagenomics to examine whether the distinct characteristics of these cultivars, combined with nitrogen fertility treatments, affect the community composition of rhizosphere bacterial and fungal communities. Finally, we are analyzing nutrient availability in soil relative to nutrient concentration in plant tissue to determine if nutrient uptake may be influenced by microbial community structure.