Effects of wastewater and different fertilization on Sorghum (Sorghum bicolor (L.) Moench) biomass production in mediterranean environment

The competition for freshwater between agricultural, industrial, and civil uses has greatly intensified over the last years in many Mediterranean areas. 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. For these reasons, interest is now growing in the reuse in agriculture of urban wastewater treated by constructed wetlands. Sorghum is a multifunctional crop that can be successfully grown in Mediterranean areas, but irrigation is necessary to achieve maximum yields and stabilize biomass production. The aim of this study was to evaluate sorghum for biomass production when irrigated with CWs treated wastewater in a representative area of Sicily, in relationship to different fertilization techniques (no fertilization, biofertilization based on mycorrhizae, and mineral nitrogen supply). The aboveground dry matter production, as expected, was positively affected by nitrogen fertilization and full ETc restitutions, moreover the ascertained intake of nutrients, particularly phosphorous and nitrogen, present in the irrigation water may reduce fertilization costs and nutrient losses in the environment. No advantages in term of biomass production are ascribed to mycorrhizal inoculum, probably due to the presence in the soil of native mycorrhizae fungi. Finally, the use of urban CWS treated water seems to be an important tool to enhance crop biomass production especially in Mediterranean dry areas, recycling scarce quality water and nutrient otherwise lost in the environment.