Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Miscanthus, switchgrass, giant reed, and bulbous canary grass as potential bioenergy crops in a semi-arid Mediterranean environment Recep Irfan Nazli a, ⁎ , Veyis Tansi a , Hasan Hüseyin Öztürk b , Alpaslan Kusvuran c a Department of Field Crops, Faculty of Agriculture, Cukurova University, 01330, Adana, Turkey b Department of Agricultural Machineries and Technologies, Faculty of Agriculture, Cukurova University, 01330, Adana, Turkey c Department of Park and Garden Plants, Kizilirmak Vocational High School, Cankiri Karatekin University, Cankiri, Turkey ARTICLE INFO Keywords: Miscanthus Switchgrass Giant reed Bulbous canary grass Biomass Mediterranean ABSTRACT Perennial grasses have received particular attention as bioenergy crops in recent years due to their high biomass productivity and environmental benefits. The objective of the present study was to compare four perennial grasses: miscanthus (Miscanthus x giganteus Keng), switchgrass (Panicum virgatum L.), giant reed (Arundo donax L.), and bulbous canary grass (Phalaris aquatica L.) in terms of biomass yield, energy balance, and biomass quality under four nitrogen fertilization rates (0, 100, 150, 200 kg ha –1 y –1 ) and 2 harvest times (autumn, winter) over three growing seasons in the Mediterranean environment of Turkey. The crop biomass and net energy yields were optimized with none or 100 kg ha –1 y –1 N input in the study. Although the winter harvest resulted in sig- nificant yield reductions in all of the grass species, it improved the biomass quality of miscanthus, switchgrass, and giant reed due to reduced moisture and ash contents. On the contrary, the autumn harvest resulted in a considerably lower moisture and ash contents in bulbous canary grass, mainly because of leaf defoliation the during summer dormancy period. Giant reed produced the highest average biomass yield (between 12.86 and 36.78 t ha –1 ) over the three years, followed by miscanthus (between 12.75 and 23.54 t ha –1 ), switchgrass (be- tween 11.88 and 18.91 t ha –1 ), and bulbous canary grass (between 5.21 and 10.83 t ha –1 ). On the other hand, bulbous canary grass provided the highest average energy ratio (19.7–64.5) over the three years, due mainly to a lack of energy input for irrigation. These results suggest that satisfactory biomass production can be achievable from miscanthus, switchgrass, and giant reed in the semi-arid Mediterranean environment under adequate moist conditions, but the irrigation requirement increases the energy cost, thus decreasing the energy ratio. In this respect, bulbous canary grass may be evaluated as an alternative bioenergy crop in the dry marginal lands of Mediterranean for sustainable biomass production. 1. Introduction The inevitable depletion of fossil fuel sources and their adverse ef- fects on the environment, particularly greenhouse gas (GHG) emissions have dramatically raised the tendency toward renewable energy sources worldwide (Chen et al., 2012). The utilization of biomass for bioenergy production is an important form of renewable energy, which can substitute fossil fuels, and thereby allow GHG mitigation (Meyer et al., 2017; Xu et al., 2017). Among bioenergy crops, perennial rhi- zomatous grasses, such as miscanthus (Miscanthus x giganteus), switch- grass (Panicum virgatum L.), and giant reed (Arundo donax L.) have re- ceived much attention due to their many advantages, including higher biomass productivity and GHG saving potentials, efficient water and nitrogen uses, and lower input requirements in comparison to con- ventional crops (Lewandowski et al., 2003a; Pedroso et al., 2014). Miscanthus and switchgrass, which have a C 4 photosynthetic pathway, have been most extensively studied as dedicated bioenergy crops around the world (Pedroso et al., 2014). Miscanthus is currently culti- vated in Europe on about 20,000 ha of land for local co-firing in heat and power plants (Don et al., 2012; Lewandowski et al., 2016). Switchgrass originated in North America and has been proposed as a prominent crop to be cultivated on marginal croplands and conserva- tion reserve program lands in the USA, which may play an important role in achieving the USA government’s 2030 bioenergy goal, pre- dicting that 30% of the petroleum usage will be displaced by biofuels (Heaton et al., 2004; Dohleman et al., 2009). On the other hand, giant reed, a C 3 perennial grass, has been considered as a valuable biomass feedstock for temperate regions, like the Mediterranean, due to its higher biomass yield potential relative to miscanthus and switchgrass under adequate water availability conditions (Christou et al., 1999; https://doi.org/10.1016/j.indcrop.2018.08.090 Received 19 June 2018; Received in revised form 29 August 2018; Accepted 31 August 2018 ⁎ Corresponding author. E-mail address: inazli@cu.edu.tr (R.I. Nazli). Industrial Crops & Products 125 (2018) 9–23 0926-6690/ © 2018 Elsevier B.V. All rights reserved. T