Assessment of giant reed biomass potential (Arundo donax l.) in marginal areas of italy via the application of arungro simulation model

Giant reed (Arundo Donax L.) is a perennial, non-food and low-input energy crop representing a promising solution to produce renewable energy at low cost, especially in marginal areas - i.e. low profitable areas which are prone to land abandonment. This study presents a detailed model-based evaluation of future trends of giant reed productivity in marginal areas of Italy, via the spatially explicit application of the process-based Arungro model. Arungro was calibrated using nine multi-year field datasets collected in six locations across Italy in the period 1997- 2013, in both rainfed and well irrigated systems, under non-limiting conditions for nitrogen availability. The model was then coupled with a georeferenced database, with detailed information on i) baseline and climate change scenarios, ii) farming practices, iii) soil physical and hydrological properties, iv) land marginality and v) crop suitability to environment. Spatially distributed simulations were run at 500×500 m spatial resolution under nonlimiting conditions for nutrients, pests and weeds. In this exploratory study, the analysis of results focused on marginal areas belonging to the provinces of Catania (CT, Southern Italy) and Bologna (BO, Northern Italy), which are characterized by contrasting climate conditions and well represented in the calibration dataset. At field level, Arungro explained the 78% and 85% of the year-to-year variability of measured green leaf area index and aboveground biomass, proving model accuracy across sites, seasons, soils and alternative management (i.e. transplanting/cutting times, stand density and water management). At province level, average aboveground biomass simulated in 2030 remained almost unchanged compared to the baseline (- 1% in BO and +1.5% in CT), although showing large heterogeneity across the study area, depending on the combination of soil and weather considered (relative changes in the range -6/+15 % in BO and -16/+15 % in CT). Conversely, results achieved for water use efficiency (mean of -10% in both provinces) were decidedly less variable suggesting that a larger amount of water will be needed to maintain the current production level under warmer scenarios. Despite the need of extending the analysis of results to other provinces and energy crops, this study provides site-specific indications on local suitability of giant reed, ready-to-use for farmers and public entities regulating the agricultural sector.