Meta-Analysis of Switchgrass: Management and Environmental Factors That Affect Its Growth and Biomass Production.

Switchgrass (Panicum virgatum), a C4 photosynthetic perennial grass has been researched extensively in North America as a biomass crop and its potential for bioenergy.  Switchgrass' ability to grow and persist in a broad range of environments, make this crop an ideal candidate for cellulosic feedstock production.  For this study, we have collected most of the relevant literature regarding key management and environmental factors that influence dry biomass production of switchgrass.  The data were analyzed using meta-analytical techniques that take into account the large variability due to genotype and location on dry biomass yields. Key factors investigated were ecotype, nitrogen rate, season of growth, precipitation, and temperature.  Our analysis showed that the switchgrass cultivars do not seem to take advantage of longer growing seasons (e.g. at lower latitudes). This suggests that there is room for improving yields by extending the vegetative period while maintaining its persistence and winter hardiness.  On average, addition of 100 kg/ha N fertilizer increased switchgrass yields by 4.3 Mg/ha, which is in close agreement with previous reports. In summary, this analysis establishes quantitative relationships for switchgrass agronomic management that can be used as guidelines for future management.