Yield responses of willow (Salix) grown in mixtures in short rotation coppice (SRC)

Twenty Salix spp. varieties were grown in mono-culture as well as being incorporated into five-, 10-, 15- and 20-way random, intimate mixtures. There was a wide range of dry matter yield from the varieties in mono-culture ranging from the most productive, which was S. schwerinii×aquatica ‘V7534’ to the least productive, S. dasyclados×caprea ‘V794’. The low yield from this, and a number of other varieties, was primarily due to their susceptibility to rust. The yield from any of the mixtures was always higher than from the combined equivalent area of the constituent varieties. This increased yield was evident in all mixtures, even the five-way mixture where three out of the five varieties had been killed by rust. A small number of varieties did not perform well when incorporated into mixtures due to reasons other than disease. Other varieties such as S. viminalis ‘78195’ and S. viminalis ‘870082 ORM’ grew much more vigorously within mixtures and were able to more than compensate for any losses which had occurred.