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The aim of the present work was to assess the leaf area duration (LAD) and the radiation use efficiency (RUE) of six warm-season perennial biomass grasses (PBGs) in a two-year field trial in the semiarid Mediterranean climate under different soil water availability. Two ecotypes of giant reed (Arundo donax L., ARCT and ARMO), one ecotype of African fodder cane (Saccharum spontaneum L. subsp. aegyptiacum (Willd.) Hack., SAC) and three hybrids of Miscanthus (the commercial M. × giganteus J.M. Greef, Deuter ex Hodk., Renvoize, M × G, and two new seed-based hybrids, GNT9 and GNT10) were compared under three levels of soil water availability: rainfed, 50% and 100% of maximum crop evapotranspiration (ETm) restoration. The determination of RUE of perennial plants is controversial and has led to contrasting results in past studies. In the present work, LAD and RUE differed among crops and irrigation regimes, being positively affected by supplemental water inputs. SAC, ARCT and ARMO showed both high LAD and RUE, which determined the high biomass yield than both the commercial M × G and the improved Miscanthus hybrids GNT9 and GNT10. RUE was particularly high and less affected by soil water availability during the mid-season, while the effect of irrigation and the differences among the genotypes were larger during the late season. Adequate biomass yield can be achieved by sub-optimal soil water availability, thus reducing the water footprint and increasing the sustainability of these biomass perennial grasses selected for the Mediterranean climate. [ABSTRACT FROM AUTHOR]

To date, economically and energy-costly vegetative propagation using rhizomes and tissue culture are the only options for the cultivation of Miscanthus spp. Some genotypes of miscanthus produce fertile seeds, offering a valid alternative to vegetative propagation. A preliminary study has been conducted on the seeds of two hybrids of miscanthus obtained via interspecific cross-pollination between M. sacchariflorus and M. sinensis: 'GRC14' (maternal: M. sacchariflorus) and 'GRC10B' (maternal: M. sinensis). Seeds were assessed for germination traits in a laboratory (at 25 °C in the dark) just after panicle harvest, and during 1-year storage at room temperature or at 8 °C. In a second experiment, the effects of gibberellic acid (GA3) solution at different concentrations (0, 50, 100, 300, 500 ppm) on the germination of freshly matured seeds were assessed. Poor germination just after harvest (<30%) indicates the occurrence of a physiological dormancy. Indeed, two months later, germination rose up to 76.7% in 'GRC14' and 50.8%, in 'GRC10B', and peaked at 95.6% in 'GRC14' and at 78% in 'GRC10B', 6 months after harvest. After a total of 12 months, germination was significantly reduced in both hybrids (≈60%). Seeds stored at room temperature lost dormancy earlier than those stored at 8 °C. Overall, germination was significantly improved by GA3, but the extent of the GA effect was genotype-dependent. In conclusion, a low establishment rate may result from direct seeding when fresh seed is used in the field. In this case, the use of GA3 is a possible strategy to ameliorate the impact of dormancy on seed germination. In the case of delayed sowings in late winter–early spring, seeds stored at room temperature after harvest may better perform than those stored at 8 °C. [ABSTRACT FROM AUTHOR]

Abstract: Miscanthus × giganteus is one of the most promising biomass crops for non-food utilisation. Taking into account its area of origin (Far East), its temperature and rainfall requirements are not well satisfied in Mediterranean climate. For this purpose, a research was carried out with the aim of studying the adaptation of the species to the Mediterranean environment, and at analysing its ecophysiological and productive response to different soil water and nitrogen conditions. A split plot experimental design with three levels of irrigation (I1, I2 and I3 at 25%, 50% and 100% of maximum evapotranspiration (ETm), respectively) and three levels of nitrogen fertilisation (0kgha−1: N0, 60kgha−1: N1 and 120kgha−1: N2 of nitrogen) were studied. The crop showed a high yield potential under well-watered conditions (up to 27tha−1 of dry matter). M. × giganteus, in Mediterranean environment showed a high yield potential even in very limited water availability conditions (more than 14tha−1 with a 25% ETm restoration). A responsiveness to nitrogen supply, with great yield increases when water was not limiting, was exhibited. Water use efficiency (WUE) achieved the highest values in limited soil water availability (between 4.51 and 4.83gl−1), whilst in non-limiting water conditions it decreased down to 2.56 and 3.49gl−1 (in the second and third year of experiment, respectively). Nitrogen use efficiency (NUE) decreased with the increase of water distributed (from 190.5gg−1 of I0 to 173.2gg−1 of I2); in relation to N fertilisation it did not change between the N fertilised treatments (N1 and N2), being much higher in the unfertilised control (177.1gg−1). Radiation use efficiency (NUE) progressively declined with the reduction of the N fertiliser level (1.05, 0.96 and 0.86gd.m.MJ−1, in 1994, and 0.92, 0.91 and 0.69gd.m.MJ−1, in 1995, for N2, N1 and N0, respectively). [Copyright &y& Elsevier]

Dryness triggers soil degradation processes and land abandonment in the south Mediterranean environment. Becoming unsuitable for food crops, it can be usable by low-iLUC risk biomass crops able to withstand prolonged dry periods due to drought-resilience traits and high biomass yield. The present experiment ascertained the biomass dry matter yield (DMY), water use efficiency (WUE) and water footprint (WF) by modulating soil water availability of six warm-season perennial grasses in the semiarid Mediterranean for two consecutive growing seasons. Two ecotypes of giant reed (Arundo donax L., ARCT and ARMO, respectively), one ecotype of African fodder cane (Saccharum spontaneum L. subsp. aegyptiacum (Willd.) Hack., SAC) and three hybrids of Miscanthus (the commercial M. × giganteus J.M. Greef, Deuter ex Hodk., Renvoize - M×G, and two new seed-based hybrids, GNT9 and GNT10, respectively) were subjected to 100%, 50% and 0% of maximum crop evapotranspiration (ETm) restoration supplied during summer months. Crop water use (CWU) differed among crops, growing seasons and irrigation regimes, and significantly influenced DMY, WUE and WF. ARCT, ARMO and SAC had higher DMY and WUE, and lower WF than Miscanthus hybrids. Among Miscanthus , the new seed-based hybrids outperformed the M×G in all examined parameters. Genotypic response in DMY, WUE and WF by varying the CWU had different trends and rates of change. The relationship between WUE and WF combining data of all genotypes, growing seasons and irrigation regimes followed an exponential decay; it underlined the importance to select for crops with high resource use efficiencies to reduce the water required per ton of biomass. • Warm-seasons perennial grasses are suitable feedstock for dry areas. • Irrigation improved dry matter yield, but worsened water use efficiency and water footprint. • Different genotypic responses were observed by modulating the crop water use. • Water footprint can be improved by selecting high water use efficiency genotypes. • Improved knowledge on traits conferring higher water use efficiency as key for dry areas. [ABSTRACT FROM AUTHOR]

Sustainable biomass production mostly relies on cultivation practices employing low external input supply. Wild germplasm might be suited for low-input techniques while providing enough output. The present study investigated four native Mediterranean perennial grasses ( Oryzopsis miliacea , Cymbopogon hirtus , Sorghum halepense , and Saccharum spontaneum L. ssp. aegyptiacum ), with an autumn and winter harvest regime in a 4-year field trial in Sicily (south of Italy). Species, cultivation year and harvest time had significant effects on whole season crop water use efficiency, energy efficiency and biomass quality. Species and cultivation year also significantly affected aboveground biomass yield and net energy yield. The total accumulated harvested yield over the 4-year experiment was the highest in Saccharum in both autumn and winter harvests (79.5 and 79.2 Mg DM ha −1 ), and the lowest in Cymbopogon (13.7 and 14.9 Mg DM ha −1 ). In both harvests, less than 20% of this total biomass was collected for all species at the first year (9.5–11.3% in Sorghum and 15.7–18.1% in Oryzopsis ). Peak biomass was reached at the third ( Saccharum and Sorghum ) or at the fourth year ( Orzyzopsis and Cymbopogon ) in autumn, and at the third year in winter harvest (all species). Water use efficiency was higher in the autumn than in the winter harvest (2.06 and 1.75 g L −1 , respectively), whilst the opposite was observed for energy efficiency (35.7 and 38.6 GJ ha −1 , respectively). Biomass structural compounds (hemicellulose, cellulose and acid detergent lignin) were higher in winter than autumn, while protein, lipid and ash contents were higher in autumn than winter. [ABSTRACT FROM AUTHOR]

Kenaf (Hibiscus cannabinus L.) is a warm-season annual plant grown in the past for the bast fiber. In the last decades, this crop has been re-evaluated for many alternative industrial uses of its biomass (i.e., production of biofuel, biocomposite materials, bioproducts). In this paper, the interaction effects of sowing time (May and June) and plant population (P20 and P40, 20 and 40 plants m-2, respectively) on yield and some biomass parameters were analysed in two cultivars of kenaf (Tainung 2-TAI, and Everglades 41-EVER), in a two-year experiment in semi-arid environment, under irrigation. The aim of this paper was to assess the potential of this crop as an energy or industrial feedstock, in south Mediterranean environment where was never cultivated. Overall, plants from late sowing (June) were smaller and with less node, those at high plant density (P40) were thinner. In both seasons, plants of TAI were taller than those of EVER. Plant weight was greater in P20, and an overall significant negative correlation was found between plant weight and actual plant density (r = −0.76 **). The shift of sowing time reduced significantly the final dry biomass. Crop productivity did not change with plant density, however a higher percent bark corresponded to P40 in both years, cultivars, and sowing times, A simple model was developed to simulate and predict the course of LAI and dry biomass (AGB) with time, using field dataset of 2004, for calibration, and dataset of 2005, for validation. The minor response of LAI to plant population in 2005 led to a low accuracy of model approximation. This result suggests that other variables that are not considered in the model, may influence LAI. Nevertheless, the overall AGB model approximation of observed value was accurate. Concluding, the results revealed that biomass productivity is more influenced by sowing time than by plant density. However, plant population has been found to regulate the proportion of bark/core layers, with important implications for industrial (energy and pulp production) purposes. Further improvements on the simple model developed, e.g., including soil water nitrogen balances submodels, may be done, in order to explore the possibility of using the model under different conditions of soil water content and nitrogen fertilization. • Sowing time and plant density effects were studied in two cultivars of kenaf. • Dry biomass yield was significantly reduced shifting sowing from May to June. • Dry biomass did not change with plant density (20 or 40 plants m-2). • The % incidence of bark on core weight was greater in plants at higher density. • A simple model was developed to simulate and predict LAI and biomass in kenaf. [ABSTRACT FROM AUTHOR]

• Long-term perennial grasses were compared in two locations and four growing seasons. • The main driving factor of bioethanol production was the biomass yield. • Optimization of harvest time allowed to gain more ethanol per unit mass. • Giant reed was the most chemically consistent feedstock among study factors. • Bioethanol biorefineries may gain fourfold the energy invested. Advanced biofuel production requires feedstock with specific composition in terms of quantity and quality. Decisions about the harvest time of perennial energy grasses have important implications for bioconversion process as well as for the life-span of the plant stand. Four-year data from long term-field trials were used to identify the optimal crop-specific harvest date (autumn vs. winter), in relation to advanced biofuel production. Three different perennial energy grasses (i.e., switchgrass, giant reed and miscanthus) were grown at Bologna and Catania (Italy), under northern and southern Mediterranean climate, respectively, adopting a low input management. In addition to the biomass yield and composition, the net energy value (NEV) from agricultural activities, and the energy return on investment (EROI) at the biorefinery gate was also evaluated. At Bologna, switchgrass biomass yield and quality (hemicellulose, cellulose and acid detergent lignin – ADL) were significantly enhanced when harvested in winter. At Catania, giant reed productivity, cellulose and ADL content were unaffected by harvest date, while hemicellulose and ash content decreased in winter. Biomass composition of miscanthus was more stable in Catania than Bologna, however, yield and components resulted significantly higher in Bologna than Catania, due mainly to the more even precipitation distribution throughout the vegetative crop development. The NEV was positive for all energy crops, treatments and locations, with the highest value for miscanthus grown at Bologna. The EROI of lignocellulosic bioethanol ranged from 4.16 for switchgrass in the autumn harvest at Bologna to 4.37 for miscanthus grown at Catania, which showed also the highest theoretical bioethanol production (169.2 kg h−1) at a feeding rate of 300 kg h−1 of raw material. Nonetheless, miscanthus grown at Bologna attained the highest bioethanol yield (12,254 L ha−1). This study proved that investigated perennial grasses are worth to be grown as lignocellulosic feedstock under low input for at least one decade, upon which Mediterranean region biorefineries may gain fourfold the energy invested. [ABSTRACT FROM AUTHOR]