Willow Yield Is Highly Dependent on Clone and Site

Use of high-yielding genotypes is one of the means to achieve high yield and profitability in willow (Salix spp.) short rotation coppice. This study investigated the performance of eight willow clones (Inger, Klara, Linnea, Resolution, Stina, Terra Nova, Tora, Tordis) on five Danish sites, differing considerably in soil type, climatic conditions and management. Compared to the best clone, the yield was up to 36 % lower for other clones across sites and up to 51 % lower within sites. Tordis was superior to other clones with dry matter yields between 5.2 and 10.2 Mg ha(-1) year(-1) during the first 3-year harvest rotation, and it consistently ranked as the highest yielding clone on four of the five sites and not significantly lower than the highest yielding clone on the fifth site. The ranking of the other clones was more dependent on site with significant interaction between clone and site. For instance, Tora obtained the same yield level as Tordis on two locations but significantly lower yield on the other sites. Dry matter content at harvest differed significantly among clones, ranging from 44.5 to 46.8 % across sites with highest level in Inger, Linnea, Resolution, and Tordis. Compared to the best site, yield level was up to 51 % lower on other sites across all clones, probably due to combined effects of differences in soil type, climate and management. Thus, willow yield depends both on the use of high-yielding clones and on the combined site effects of soil, climate, and management.