Modeling Phenology of Upland and Lowland Switchgrass Ecotypes.

Switchgrass (Panicum virgatum L.) is a C4 perennial grass native to the United States and an important source of hay, grazing and biomass for lignocellulosic fuel production in the Great Plains and Midwest. Mainly there are two types of switchgrass varieties grown for biomass production i.e., lowland and upland varieties. It has been reported that upland ecotypes transplanted into a lowland environment maintained a higher photosynthetic rate than lowland ecotypes; however, lowland ecotypes were more susceptible to water stress than upland ecotypes when transplanted into a drier upland environment. Thus, knowledge of phenology of these cultivars and ecotypes of switchgrass is very important to understand their adaptability. The objectives of this study were to measure and predict phenology of five switchgrass varieties of lowland and upland origin, and also identify the best suited varieties in Iowa for enhanced management practices and optimizing productivity. A field trial was established in summer 2007 as a randomized complete block design with six replicate blocks. Data collected in 2012 was used for model calibration and data collected in 2013 was used for model validation. The model is based on APSIM PLANT generic phenology module. Our analysis indicated the following results: a) Clear differences in all crop stages b) Calibrated model predicted switchgrass phenology very well. This study delivers new data that can be used by many simulation models to improve their predictions and expand their cultivar databases.