MORPHOLOGICAL DEVELOPMENT OF SWITCHGRASS IN DIVERSE ENVIRONMENTS

Switchgrass (Panicum virgatum L.) has been proposed as a model species for biomass fuel production. To better manage switchgrass as a biofuel crop, knowledge of its morphological development in several environments would be useful, This study was conducted to determine how morphological development of switchgrass varies in different field environments and to relate development to soil moisture status and other meteorological indicators. An established stand of'Alamo' switchgrass at Stephenville, TX (32 degrees 13'N, 98 degrees 12'W;399 m elevation), was sampled weekly or biweekly from April to September in 1991 and 1992, Field plots of Alamo and 'Cave-in-Rock' were established at Stephenville in 1992 and sampled 17 times during 1993. Established field plots of Alamo and Cave-in-Rock at Blacksburg, VA (37 degrees 11' N, 80 degrees 25' W; 610 m elevation) were sampled at 11 dates in 1992 and 9 dates in 1993 from May to September. Maturity stage at each harvest was determined according to a maturity scale developed at Stephenville, Morphological development and apical meristem elevation of both cultivars were closely related to cumulative degree days (DD, base 10 degrees C) at each location, The developmental patterns were similar among years and were not affected by differences in soil moisture or rainfall distribution at Stephenville. Cave-in-Rock and Alamo matured about 4 wk earlier at Stephenville than at Blacksburg. The duration of the vegetative period was about 300 DD shorter at Blacksburg than at Stephenville for both Alamo and Cave-in-Rock, The close association of morphological development with DD in different environments could simplify morphological development models; however, the models would need to be location specific, because the timing and duration of phenological events differed as switchgrass cultivars were moved southward or northward.