Estimating Yield Potential of Shrub Willow in the Northeast U.S. Using a Dynamic Simulation Model.

Dedicated bioenergy crops are projected to be a significant source of biomass for the production of bioenergy, biofuels and bioproducts in the coming decades. One such crop, shrub willow (Salix spp.), has several characteristics making it ideal for perennial energy cropping systems, including high yield potential, vigorous coppicing ability and a broad genetic base. In the Northeast U.S., there is a large production potential for shrub willow because of extensive areas of abandoned or marginal agricultural land. To assess the potential of these lands for shrub willow production, we need to identify yield constraints for the range of soils and climates within the region. We developed a biophysical model representing key soil and crop processes to predict yield potential and identify the factors that limit yield, focusing on climate, soil water and soil nitrogen. This model (Precision Nitrogen Management or PNM model) is composed of a dynamic simulation model of soil N transformations and soil N/water transport (LEACHN; Hutson, 2003) linked to both shrub willow and maize N uptake/growth models. The PNM model has been parameterized and calibrated based on literature values and data from field studies of shrub willow clones by the State University of New York College of Environmental Science and Forestry. Initial model testing has shown good correspondence between simulated and measured rotational biomass yields for a range of soil types, N fertility and available soil water. Specifically, after calibrating the model for two experiments, we predicted biomass yields for three additional experiments. Predictions were within 7% of the measured yield. We are currently performing simulations for representative climate regions and soil types to better estimate biomass production potential of shrub willow in the Northeast U.S.