Identifying strategies for enhancing switchgrass quality for use as a bioenergy feedstock

The United States has set a goal for integrating biofuels into the nation\u27s energy portfolio by 2022. Declining energy supplies and issues concerning energy independence and adverse environmental consequences have increased interest in developing bioenergy. Renewable bioenergy could be provided by high-yielding crops such as switchgrass (Panicum virgatum L.). The successful growth of the bioenergy industry will depend not only on harvesting switchgrass with high yield but with good quality. Few, however, have intensively studied the changes that occur in quality during the growing season. A field plot study on an established stand of a lowland cultivar planted in 2006 was carried out. A total of 13 harvests were taken at different dates in a one-cut system in 2011 and certain quality characteristics like nutrient concentration (N, P, K, Ca, Mg), ash and moisture content were measured. In addition, relationships between these variables and climatic conditions (rainfall and temperature) were determined. Overall, the variables studied declined significantly throughout the growth period. These quality indicators and dry weight also showed little or no correlation with rainfall or temperature throughout the harvest period. The highest quality switchgrass was observed when switchgrass harvest was delayed. For all of the quality characteristics studied, however, earlier harvests were not significantly different from the final harvest date indicating that switchgrass grown in Middle Tennessee may have an earlier and longer harvest window than what is currently recommended. Based on our data and depending on the quality characteristic/nutrient, switchgrass may be harvested earlier than the current recommendation (after Nov. 1 or killing frost) by 2 to 17 weeks allowing farmers greater flexibility