Long-term yield effects of establishment method and weed control in willow for short rotation coppice (SRC)

• Lay-flat planting of willow gave higher yield than cuttings in 1st harvest rotation.
• Over 16 years, lay-flat planting and cuttings gave similar yields.
• Depending on length, billets gave similar or lower yields than cuttings.
• Over 16 years, willow was able to maintain a relatively high yield level.

A prerequisite for successful willow production is a reliable and economically competitive establishment of the crop. Here, we compare different establishment methods including long-term yield effects. A field trial with the new-bred variety Bjørn was established in 1996 and included four establishment methods; 1) vertical planting of standard 0.2 m cuttings; 2) horizontal planting of 0.1 m billets; 3) horizontal planting of 0.2 m billets; 4) horizontal planting of 1.8 m rods. All establishment methods were combined with mechanical and chemical weed control during the establishment year. Dry matter (DM) yield was measured over 6 harvest rotations corresponding to 16 years. In 1st rotation, yield differed significantly between establishment methods with highest yield for 1.8 m rods (10.4 Mg ha−1 year−1), intermediate yield for cuttings and 0.2 m billets (8.6 and 8.5 Mg ha−1 year−1, respectively) and lowest for 0.1 m billets (5.6 Mg ha−1 year−1). No differences were found in 2nd rotation. Over 1st and 2nd rotation, mechanical weed control resulted in significantly lower yield than chemical control when combined with 0.1 m billets. Cuttings and 1.8 m rods were compared over 1st, 2nd, 3rd, 5th and 6th rotation. Rods gave higher yield in 1st rotation, lower yield in 3rd rotation but there were no significant yield differences in 2nd, 5th and 6th rotations, resulting in similar mean yields of 12.4 and 11.9 Mg ha−1 year−1 for cuttings and rods over the whole period. The general yield development over time indicates a relatively stable long-term yield level.