Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer’s economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7–8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34–42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha−1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus × giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997–2012 was obtained with the shortest row distance (∼18,000 rather than ∼12,000 plants ha−1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha−1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995–2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha−1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha−1 DM was achieved over the period 1995–2012.
Bioenergy Research, 2014, Vol 7, Issue 2, p. 620-635