Influence of the agricultural management practices on the yield and quality of poplar biomass (a 9-year study)

Abstract

The aim of this work is to study the effect of different agricultural management on the yield and quality of two poplar biomass clones (AF2 and I-214 clones) in short rotation coppices (SRC), which were harvested using different alternatives (with and without cutting and sprouting after the first year), with two fertilisation doses and through three different 3-year rotation cycles. The plantation was established in 2006 in a marginal land at 1,100 m above sea level in central-northern Spain. Yields were evaluated and biomass samples were analysed to determine the quality of the biomass for energy purposes. Biomass quality was estimated taking into account calorific value, volatile matter, ash content, carbon, nitrogen, sulphur and chlorine contents, as well as the chemical composition and melting behaviour of their ashes. The highest yields, around 9 dry tons per hectare and year, were obtained in this marginal land during the first and second rotation cycles when plots received a supplementary fertilisation. Both clones (AF2 and I-214) provided similar yield and biomass quality. Plots where poplar was not harvested the first year (without cutting and sprouting after the first year) provided higher accumulated yields. Poplar biomass from SRC can be considered a suitable solid biofuel due to its appropriate ash melting behaviour and its low content of nitrogen (0.44 wt-%), sulphur (0.03 wt-%) and chlorine (around 0.01 wt-%). No important significance effect on the poplar quality can be found depending on the additional fertilisation. Poplar quality varied as a function of root/stem age.