Comparative trials of elite Swedish and UK biomass willow varieties 2001-2010.

UK willow variety trials are planted at four sites at IACR-Long Ashton in Bristol, Markington in North Yorkshire, North Molton in Devon and Loughgall in County Armagh. The trials normally comprise between five and ten elite willow lines including two yield controls (L78183 and ‘Tora’). Between 1991-95, the trial design included 10 replicates of 10 plants (double rows of five) planted at a stocking rate of 20,000 cuttings per hectare. Subsequent trials included three replicates of each variety (52 plants per plot) in a randomised plot design. Typically, the duration of a trial is 6 years comprising an establishment year followed by a two-year harvest and a three-year harvest. ‘Ashton Stott’ has been found to be the most productive variety with a mean yield of 15.4 oven dry tonnes per hectare per year from 16 harvests. This equates to 243% of the control clone L78183. ‘Ashton Parfitt’ the sibling of Stott has also yielded highly with an average of 13.9 ODT/ha/yr from 9 harvests. ‘Tora’ is the highest yielding variety originating from the Svalöf-Weibull breeding programme with an average yield of 12.8 ODT/ha/yr from 23 harvests. At IACR-Long Ashton, the S. viminalis clone Bowles Hybrid has produced high yields but its overall yield performance is low as it is severely affected by rust, particularly at the Northern Ireland sites. In 2001, the first yield trials involving willows bred by the European Willow Breeding Partnership (EWBP) will be harvested. Early results will be exhibited at the conference.