Abstract
Yield is a critical factor for economic and environmental assessments of willow biomass crops which undergo multiple harvests. Changes in yield from first to subsequent rotations show variability in the literature, but fixed increases are often used in models. Yield data across 360 plots were used to build regression models which showed that change between first and second rotation yields is largely dependent on first rotation yield quantity (R2=0.635) with higher yielding plots having smaller changes than lower yielding plots. A meta-analysis of the literature revealed a similar pattern. Repeated measures modeling over three rotations with 18 cultivars at two sites showed that 55.6% of site-cultivar combinations had consistent yields over time. Cultivar ranks after one rotation were strongly correlated with ranks after three rotations at both sites (Spearman coefficients of 0.91 and 0.83). Characterizing these trends showing yield stability should provide more accurate yield estimates across rotations.