Green Manuring for Low-input Irrigated Maize Cultivation as an Energy Crop in Mediterranean Climates

Introduction of high input crops to existing rotation schemes for bio-energy production such as corn in Mediterranean areas would only be possible by improving its yield and decreasing the cultivation costs. This work focusses on the combined effect of irrigation rate and green manuring on growth and productivity of irrigated corn grown in typical Mediterranean lowland. On a flat, calcareous clay-loam soil, a three-year field experiment was conducted. Pisum sativum was sown in specific plots every year in November and grew as cover crop under rainfed conditions until mid-April where its biomass was incorporated into the soil, while maize was sown by the end of April. A 3 × 2 factorial split-plot design was used in 3 blocks. Corn irrigation comprised the main plots and pea incorporation comprised the sub-plots. Soil moisture was monitored at weakly intervals at 10 layers of 10 cm each down to 1 m soil depth. Corn growth and final yield were monitored by means of distracting samplings. The overall conclusion is the significant positive effect of green manuring on corn biomass and seed yield. This effect was mainly attributed to greater water use efficiency as green manuring was associated with greater moisture content within the rooting zone compared to control plots. The increased yield obtained could offset the increased costs of growing pea as green manure (increase in farmers’ income of 20–110 € ha−1), allowing green manuring to become more widely used to reduce fertilization and irrigation inputs while also allowing corn to be introduced into current crop rotations for bio-energy production.