Response of giant reed (Arundo donax L.) to nitrogen fertilization and soil water availability in semi-arid Mediterranean environment

The aim of the present work was to evaluate the effect of soil water availability and nitrogen fertilization on yield, water use efficiency and agronomic nitrogen use efficiency of giant reed (Arundo donax L.) over four-year field experiment.After the year of establishment, three levels for each factor were studied in the following three years: I₀ (irrigation only during the year of establishment), I₁ (50% ETm restitution) and I₂ (100% ETm restitution); N₀ (0 kg N ha⁻¹), N₁ (60 kg N ha⁻¹) and N₂ (120 kg N ha⁻¹).Irrigation and nitrogen effects resulted significant for stem height and leaf area index (LAI) before senescence, while no differences were observed for stem density and LAI at harvest.Aboveground biomass dry matter (DM) yield increased following the year of establishment in all irrigation and N fertilization treatments. It was always the highest in I₂N₂ (18.3, 28.8 and 28.9 t DM ha⁻¹ at second, third and fourth year growing season, respectively). The lowest values were observed in I₀N₀ (11.0, 13.4 and 12.9 t DM ha⁻¹, respectively).Water use efficiency (WUE) was significantly higher in the most stressed irrigation treatment (I₀), decreasing in the intermediate (I₁) and further in the highest irrigation treatment (I₂). N fertilization lead to greater values of WUE in all irrigation treatment.The effect of N fertilization on agronomic nitrogen use efficiency (NUE) was significant only at the first and second growing season.Giant reed was able to uptake water at 160–180 cm soil depth when irrigation was applied, while up to 140–160 cm under water stress condition.Giant reed appeared to be particularly suited to semi-arid Mediterranean environments, showing high yields even in absence of agro-input supply.     

Biomass production and N balance of giant reed (Arundo donax L.) under high water and N input in Mediterranean environments

This study aimed to evaluate the productivity of Arundo donax under good water and N availability coming from non-conventional sources, in different Italian environments (Padova and Bologna in the north, Reggio Calabria and Catania in the south) in relation to three harvest periods (autumn; mid-winter; late-winter).In the northern locations A. donax had already reached maximum productivity the year after transplanting, with 85 and 98 t ha⁻¹ of dry matter at Padova and Bologna, respectively. At Reggio Calabria and Catania a further biomass increase was obtained from the second to third year of cultivation, when production was 62 t ha⁻¹ and 51 t ha⁻¹, respectively.The average dry matter production was 74, 66 and 65 t ha⁻¹ with autumn, mid-winter and late-winter harvesting, respectively.Under N input ranging from 225 to 329 kg ha⁻¹ year⁻¹ at the different locations, the apparent N balance (input–output) was negative except in Catania indicating a great potential of A. donax to provide high N uptake, which would be a useful feature in environments under the European Nitrates Directive.