Rocky Lemus

Switchgrass cultivar/ecotype selection and management for biofuels in the upper southeast USA.

Switchgrass (Panicum virgatum L.), a perennial warm-season grass indigenous to the eastern USA, has potential as a biofuels feedstock. The objective of this study was to investigate the performance of upland and lowland switchgrass cultivars under different environments and management treatments. Four cultivars of switchgrass were evaluated from 2000 to 2001 under two management regimes in plots established in 1992 at eight locations in the upper southeastern USA. Two management treatments included 1) a single annual harvest (in late October to early November) and a single application of 50 kg N/ha/yr and 2) two annual harvests (in midsummer and November) and a split application of 100 kg N/ha/yr. Biomass yields averaged 15 Mg/ha/yr and ranged from 10 to 22 Mg/ha/yr across cultivars, managements, locations, and years. There was no yield advantage in taking two harvests of the lowland cultivars (Alamo and Kanlow). When harvested twice, upland cultivars (Cave-in-Rock and Shelter) provided yields equivalent to the lowland ecotypes. Tiller density was 36% lower in stands cutting only once per year, but the stands appeared vigorous after nine years of such management. Lowland cultivars and a one-cutting management (after the tops have senesced) using low rates of applied N (50 kg/ha) are recommended.

Moisture Determination in Windrowed Switchgrass Using Electrical Resistance Probes

Determining moisture content (MC) levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies needed to measure MC in switchgrass using electrical resistance meters, ii) to determine the effects of pressure and probe orientation on MC measurement and iii) to generate MC calibration equations for electrical resistance meters using switchgrass in the senescence growth stage. Two meters (Meter 1, Farmex HT-PRO; Meter 2, Delmhorst F-2000) were selected based on commercial availability. A forage compression apparatus was designed and constructed with on-farm materials and methods to provide a simple system of applying pressure achievable by any forage producer or researcher in the field. A study was performed to test four levels of moisture contents (10%, 20%, 30%, and 40%), five pressures (0, 1.68, 3.11, 4.55,