Nitrogen Demand Associated with Increased Biomass Yield of Switchgrass and Big Bluestem: Implications for Future Breeding Strategies

Development of perennial biomass cropping systems is focused on maximizing biomass yield with minimum inputs, particularly nitrogen (N) fertilizer. Historical breeding efforts have focused on increasing biomass yield but have ignored N-use efficiency. The purpose of this study was to quantify the increased N demand associated with realized gains in biomass yield from big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) breeding programs. Nitrogen demand was highly variable across locations and years, ranging from − 1.7 to + 6.8 kg N Mg−1 DM, with an average of 2.2 kg N Mg−1 DM. Increases in N demand were closely associated with realized gains in biomass yield and were observed for all types of switchgrass (upland, lowland, and hybrid) as well as for big bluestem. Attenuation of these responses will require alternative breeding schemes that are focused on evaluation of switchgrass genotypes and progeny under low-N conditions and include a highthroughput tissue N analysis as a component of future selection criteria, designed to develop new cultivars with high biomass yield and low tissue N