Effect of fertilisation on biomass yield, ash and element uptake in SRC willow

Optimal fertilization of short rotation coppice (SRC) willow is important both in terms of economic yield and environmental effect. We measured biomass yield and nutrient uptake in two willow clones, Inger and Tordis, grown on a coarse sandy soil and within six different fertilization regimes. Fertilization treatments were carried out during two two-year harvest rotations, beginning in the 2nd growth year of the plantation. Willow was fertilized as follows with names referring to type of fertilizer and total quantities of nitrogen (kg ha −1 ) in first and second year within both rotations: 1) Control 0+0 , 2) NPK 120+0 , 3) Slurry 180+0 , 4) NPK 120+120 , 5) NPK 240+0 , 6) Slurry 360+0 . Fertilization affected biomass yield significantly but interacted with rotation and clone. In first rotation, fertilization increased dry matter (DM) yield across clones significantly from 3.7 Mg ha −1 y −1 for Control 0+0 to 6.5, 6.4 and 5.6 for Slurry 360+0 , NPK 120+120 and NPK 240+0 , respectively. In second rotation, yield increased from 6.2 Mg ha −1 y −1 to 8.8, 8.2, 7.8 and 7.4 for Slurry 360+0 , NPK 240+0 , Slurry 180+0 and NPK 120+120 , respectively. Biomass dry matter yield per ha increased linearly at 15 kg kg −1 of applied total-N in both rotations. The yield increase in response to fertilization was generally larger in Inger than in Tordis. In general, element concentration in the harvested biomass was either unaffected or slightly reduced by fertilization. In conclusion, yield response to fertilization appears to be primarily related to the quantity of N applied but the effect depended on fertilizer type, harvest rotation and willow clone.