Ensiling of Willow and Poplar Biomass Is Improved by Ensiling Additives

Biomass from willow and poplar harvested for feed during the growing season may be preserved by ensiling; however, little research has focused on ensiling of these biomasses. This study focuses on the use of ensiling additives to reduce the pH to around 4.0 to secure stable storage. Lab-scale ensiling experiments were conducted with different willow and poplar clones, shoot ages, and harvest times (June or September). Ensiling without additives often resulted in limited pH reduction. The pH could be reduced in the biomass of both species by adding formic acid, and the required dose to reduce the pH to 4.0 (buffering capacity, BC) ranged significantly between biomass types but was in the range of 2–5 kg formic acid (78%) per ton fresh weight. BC decreased with increasing dry matter (DM) content and decreasing crude protein content. The pH could also be reduced during ensiling by applying molasses and/or lactic acid bacteria, although not sufficiently in poplar. Willow biomass was ensiled effectively at the pilot scale with less than 7% DM loss by adding formic acid or by mixing with grass biomass. Comparable pH results were obtained at the lab scale and pilot scale. The study demonstrates how willow and poplar can be ensiled; however, more research is needed on quality changes during ensiling.