Biomass production and energy balance of a 12-year-old short-rotation coppice poplar stand under different cutting cycles N. NASSI O DI NASSO, W. GUIDI, G. RAGAGLINI, C. TOZZINI and E. BONARI Land Lab Scuola Superiore Sant’Anna, via Santa Cecilia 3, 56127 Pisa, Italy Abstract Given today’s political targets, energy production from agricultural areas is likely to increase and therefore needs to be more sustainable. The aim of this study was thus to carry out a long-term ﬁeld trial based on the poplar short-rotation coppice (SRC), in order to compare dry matter, energy-use efﬁciency and the net energy yield obtainable from this crop in relation to different harvest frequencies (1-, 2- and 3-year cutting cycles). The results showed that poplar SRC performed very well under temperate climates as it can survive up to 12 years, providing a considerable annual biomass yield (9.9, 13.8, 16.4 t ha 1 yr 1 for annual T1, biannual T2 and triennial T3 cutting cycles, respectively). The system tested in southern Europe showed a positive energy balance characterized by a high energy efﬁciency. We found that the choice of harvest interval had huge conse- quences in terms of energy yields. In fact, the energy efﬁciency improved from T1 to T2 and T3, while the net energy yield increased from 172 to 299 GJ ha 1 yr 1 . This study suggests that, with 3-year harvest cycles, poplar SRC can contribute to agronomic and environmental sustainability not only in terms of its high yield and energy efﬁciency but also in terms of its positive inﬂuence on limiting soil tillage and on the environment, given its low pesticide and nutrient requirements. Keywords: biomass yield, energy efﬁciency, energy yield, harvesting cycle, poplar, short-rotation forestry Received 7 October 2009; revised version received 11 February 2010 and accepted 30 March 2010 Introduction The use of biomass for energy purposes is an important European Union policy, which aims to mitigate the effects of climate change by reducing greenhouse gas emissions from fossil fuel combustion, and securing the energy supply through the diversiﬁcation of energy sources (Gasol et al., 2008). Biomass exploitation could increase employment in rural areas and provide an additional income for farmers. In addition, the Eur- opean biomass market is increasing and in Italy, woody chip biomass at 40% of moisture can sell for up to h47 t 1 (Gasol et al., 2009a). Poplar (Populus spp.) is one of the most promising woody energy crops due to its high yield and high ecological interest in terms of low input requirements and biodiversity maintenance (Bo ¨ rjesson, 1999). This species is thus grown as a short-rotation coppice (SRC), which consists of fast-growing plants being harvested (coppiced) at very short intervals (1–5 years). The largest dataset concerning SRC crop management is for the most part limited to northern and central Europe and North America (Heilman & Norby, 1998; Labrecque & Teodorescu, 2005; Spinelli & Hartsough, 2006; Pei et al., 2008). For Mediterranean countries (e.g. Italy), information on SRC is also available, but it focuses mainly on a few agronomic aspects such as productivity, fertilization (Moscatelli et al., 2008), water requirements (Guidi et al., 2008a) and some qualitative harvestable biomass traits (Guidi et al., 2008b). For those sites where water is not a limiting factor, plant spacing and cutting cycles are the most impor- tant agronomic aspects on which the establishment of an SRC plantation and its biomass production depend considerably. Nevertheless, currently, little informa- tion is available on these aspects. Many studies report that spacing and SRC cutting cycles are closely related. Correspondence: Nicoletta Nassi o Di Nasso, tel. 1 39 50 883512, fax 1 39 50 883526, e-mail: n.nassiodinasso@sssup.it GCB Bioenergy (2010) 2, 89–97, doi: 10.1111/j.1757-1707.2010.01043.x r 2010 Blackwell Publishing Ltd 89