Simulating Seasonal Trends in Switchgrass Biomass Using Almanac.

An accurate growth model for switchgrass (Panicum virgatum L.) is needed to support decision-making on timing of harvest to predict biomass yield as a function of soil and weather conditions and to maximize resource-use efficiency. The aim was not only calibrate and validate ALMANAC model to simulate ‘Alamo’ switchgrass biomass yield for Arkansas conditions, but also to assess the model limitations on simulating Alamo. The model was calibrated based on biomass samples from plots established in 2008 in Fayetteville, AR, which were sampled approximately monthly from early May 2009 to mid-February 2010, and again in 2010-2012. Additionally, the model was validated based on 5 consecutive years of Alamo biomass yields from plots located at two contrasting Arkansas ecoregions, Ozark Highlands in northwest Arkansas and Bottomland and Terrace in east-central Arkansas. ALMANAC was calibrated by modifying the value of five crop parameters according to field measurements. Validation showed good simulation for regional average biomass production. Nevertheless, deviation of the validation regression from slope of 1 necessitates further investigation of growth constraints such as water deficit stress.