David Lang and Vitalis Temu. Mississippi State University, Mississippi State University, Box 9555, Mississippi State, MS 39762-9555
Switchgrass (Panicum virgatum L.) is a tall growing native warm season grass with wide adaptation and multiple uses. Forage utilization and seed production offer the potential for economic returns as acreage is developed for biomass feedstock. The objective of this study was to evaluate alternative usage of switchgrass within a biomass system. An existing stand of ‘Alamo’ switchgrass was harvested on 13 June and 16 December 2006 as forage and biomass. Seed was harvested 30 October for half and full season yield. Seed was harvested within hand clipped 3.28 ft2 quadrats, bagged and air dried. Seed was cleaned into 1st and 2nd grades by weight using a suction cleaning machine. Total herbage yield was 7.8 tons acre-1 harvested once in December (full season) and 5.9 tons acre-1 harvested in June and December (half season). Total threshed seed yield in October was 165 lb acre-1 for switchgrass grown full season and 53 lb acre-1 for half season switchgrass. Ratio of grade 1 (heavier) to grade 2 (lighter) seed was 1.34 for half season switchgrass and 0.91 for switchgrass not harvested in June. Germination of grade 1 seed was 63.6% for switchgrass seed harvested following June harvest and 59.5% for switchgrass seed grown for the full season (NS). Yield of grade 1 pure live seed (PLS) was 35 lb acre-1 for full season and 28 lb acre-1 for half season. Switchgrass harvested in June had forage quality characteristics suitable for beef animals. In vitro dry matter digestibility (IVDMD) was 53.7%, acid detergent fiber was 34.5%, neutral detergent fiber was 72.5%, lignin was 5.7% and protein was 7%. In contrast, neither half nor full season switchgrass harvested in December was suitable for anything other than as a biomass feedstock. IVDMD was 32.4 and 26.9% for half and full season switchgrass.
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