Evaluating Switchgrass Varieties for Biomass YIELD and Quality in Massachusetts.

Currently there are no published data on switchgrass (Panicum virgatum L.) yield potential for the state of Massachusetts. Our objective was to determine how cultivars perform in this northeastern United States climate and how harvest management affected overall yield.  Five high-yielding upland varieties (Blackwell, Carthage, Cave-in-Rock-, Shawnee, and Shelter) were harvested at senescence (fall), kill frost (winter), and spring between 2009-2011. Measurements were taken of yield, ash, total nitrogen, and mineral content in the feedstock and non-structural carbohydrates in roots at each time of harvest.   In the first year all varieties produced their highest yields at senescence. Carthage was the highest yielding variety, and harvesting in fall consistently produced higher yields than harvesting in winter or spring. Harvesting Cave-in-Rock, Shawnee, Blackwell, and Shelter as the plant went into senescence in the first year caused a dramatic reduction in yield the following year, such that winter harvests were equivalent to or better than fall harvests.  Nutrients such as nitrogen, phosphorus, potassium, magnesium and ash all decreased in the feedstock when the harvest was delayed from fall to winter or spring. Soluble nonstructural carbohydrate concentrations in the roots were three times higher in the winter than in the fall. These levels decreased again in the spring. Biomass yields ranged from 6.8 Mg ha^-1 to 12.6 Mg ha^-1 across upland varieties in all years.