Aboveground Yield and Biomass Quality of Giant Reed (Arundo donax L.) as Affected by Harvest Time and Frequency

Giant reed (Arundo donax L.) is a perennial rhizomatous grass producing high biomass yields in temperate and warm climates under rainfed and reduced input conditions. Harvest time and frequency typically affect the productivity and suitability for energy conversion of energy crops. In order to evaluate the effect of different cutting managements on biomass yield and quality of giant reed, three single harvest (SH) and six double harvest (DH) systems were compared. Biomass yield, leaf mass ratio, dry matter (DM), and ash content were assessed for each harvest. Over the 2 years of study, giant reed demonstrated good productivity levels both when harvested once a year and twice a year (about 30 Mg ha⁻¹) without significant differences between the treatments. Regarding double-cut regimes, overall yields were significantly reduced by delaying the second cut from autumn to winter (32.9 vs 30.2 Mg ha⁻¹), and the percentage of the first cut with respect to the overall yield varied from 55 to 80 %. Biomass quality was also significantly affected by harvest time and frequency. The biomass obtained in double harvest systems showed higher average moisture levels (about 40 % DM) and ash concentrations ranging from 4.7 to 8.7 %. In contrast, single harvest systems led to a drier biomass (47–57 % DM) and reduced mineral contents (3.4–4.8 % ash). The feasibility of double-cut management should therefore be considered in terms of the specific giant reed-based supply chain, with particular regards to the storage and conversion technology adopted.