Variety and altitude effects on yield and other characters of SRC willow in Wales

The main purpose of the project was to assess the adaptability and biomass yield potential of old and new varieties of SRC willow (Salix spp.) through trialling in Wales. Two trials were established in 2003 (Trial I) and 2004 (Trial II) using a total of 19 willow varieties and planted at a stocking rate of 13,333 cuttings per hectare. Average yields of varieties in Trial I varied between 8.5-13.2 odt ha-1 yr-1 based on two harvest years and a biennial harvest rotation. Generally, variety yields were greater in the second harvest rotation probably due to an increase in stem number and stem diameter. Tordis was the most productive variety, although 13 of 15 varieties did produce average yields in excess of 10 odt ha-1 yr-1. Trial II incorporated three altitude sites, and variety yields were between 3.2-14.6 odt ha-1 yr-1 at 32 masl, 3.1-8.7 odt ha-1 yr-1 at 228 masl, and 2.0-7.9 at 296 masl in the first harvest year on a triennial harvest rotation. Discovery yielded best at 32 masl, Endeavour at 228 masl, and Inger at 296 masl. At each trial, the incidence of leaf rust, leaf damage and aphids were generally low and unlikely to have any adverse impact on variety yields. In addition, results of the chemical and physical properties of willow chip of varieties from Trial I showed that all varieties assessed would present reasonable quality feedstock for combustion. The implications of these results on the growth and development of SRC willow in Wales are discussed.