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 biofue l crop, knowledge of its morphological development in several environm ents would be useful, This study was conducted to determine how morpho logical development of switchgrass varies in different field environme nts and to relate development to soil moisture status and other meteor ological indicators. An established stand of'Alamo' switchgrass at Ste phenville, 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, F ield plots of Alamo and 'Cave-in-Rock' were established at Stephenvill e 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 degree s 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 det ermined according to a maturity scale developed at Stephenville, Morph ological development and apical meristem elevation of both cultivars w ere 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 dist ribution at Stephenville. Cave-in-Rock and Alamo matured about 4 wk ea rlier at Stephenville than at Blacksburg. The duration of the vegetati ve period was about 300 DD shorter at Blacksburg than at Stephenville for both Alamo and Cave-in-Rock, The close association of morphologica l development with DD in different environments could simplify morphol ogical development models; however, the models would need to be locati on specific, because the timing and duration of phenological events di ffered as switchgrass cultivars were moved southward or northward.