Effects of wastewater irrigation on giant reed (Arundo donax L.) populations biomass production in different Mediterranean environments.

The competition for freshwater between agricultural, industrial, and civil uses has greatly intensified in many Mediterranean areas characterized by prolonged dry seasons. Agriculture accounts for 80% of all water consumption. Efficient use of water for crop irrigation and reuse of scarce quality waters is therefore needed for the conservation of this limited resource. Arundo donax L., a rhizomatous widespread spontaneous plant in Mediterranean regions, is considered among the species at high aptitude for biomass buildup. The aim of this study was to evaluate biomass production of arundo irrigated with different low quality water, at full ETp restitutions, in different Italian environments in relation to three harvest dates. Moreover the combustion data, moisture content, and heating values were measured. The average dry matter production, in the second year cultivation, ranged from 33 to 132 t ha-1. At a plant density of about 10 plant m-2 the highest shoot dry biomass ever measured in Italy was recorded. As concerns the harvest date, the results suggested that arundo reached the maximum biomass yield between November and January. These preliminary results suggest the interest in using treated wastewater for Arundo irrigation. Moreover, the intake of nutrients, present in the irrigation water may reduce fertilization costs and nutrient losses in the environment.