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Mediterranean climates are characterized by long periods of drought during summer and short dry periods from autumn to spring, what limits plant CO2 assimilation and biomass production to a great extent. The JRC has set a series of thresholds to define marginal lands in terms of biophysical constraints. We focus on climate limitation given by the ratio between precipitations and potential evapotranspiration (P/ET). Areas with P/ET ≤0.60 are classified as affected by “dryness”. The present study follows up a long-term plantation of the C4 perennial grass Saccharum spontaneum ssp. aegypticum under different water regimes in a semi-arid Mediterranean environment.

Mediterranean climates are characterized by long periods of drought during summer and short dry periods from autumn to spring, what limits plant CO2 assimilation and biomass production to a great extent. The JRC has set a series of thresholds to define marginal lands in terms of biophysical constraints. We focus on climate limitation given by the ratio between precipitations and potential evapotranspiration (P/ET). Areas with P/ET ≤0.60 are classified as affected by “dryness”. The present study follows up a long-term plantation of the C4 perennial grass Saccharum spontaneum ssp. aegypticum under different water regimes in a semi-arid Mediterranean environment.

Perennial, no-food grasses have been proposed as the most efficient species for biomass production due to their natural resource use efficiency, agronomic, environmental and social benefits. Nitrogen requirement is a significant issue in intensive agriculture and greatly affects the energetic balance of crops. Hence, reduced nitrogen fertilizer by means of low input cropping systems could directly mitigate greenhouse gas emissions. In the present study long-term plantations of two perennial grasses (Arundo donax and Miscanthus x giganteus) grown in rainfed conditions under two nitrogen regimes were compared in terms of biomass yield and nitrogen use efficiency.

Perennial, no-food grasses have been proposed as the most efficient species for biomass production due to their natural resource use efficiency, agronomic, environmental and social benefits. Nitrogen requirement is a significant issue in intensive agriculture and greatly affects the energetic balance of crops. Hence, reduced nitrogen fertilizer by means of low input cropping systems could directly mitigate greenhouse gas emissions. In the present study long-term plantations of two perennial grasses (Arundo donax and Miscanthus x giganteus) grown in rainfed conditions under two nitrogen regimes were compared in terms of biomass yield and nitrogen use efficiency.

A general obstacle to the development of perennial grasses is the relatively high cost of propagation and planting. The objective of the present study was to investigate new propagation and planting methods of giant reed (Arundo donax L.), miscanthus (Miscanthus x giganteus Greef et Deuter) and switchgrass (Panicum virgatum L.). Field and open-air pot trials were carried out in four different locations across Europe: hydro-seeding of switchgrass was tested in field trials at the experimental farm of the University of Bologna, Italy; stem propagation and bud activation methods of miscanthus were evaluated in field experiments in Péteri, Hungary; giant reed rhizome and stem propagations were compared in a field trial in Aliartos, Greece; finally, an open-air pot trial was carried out in Catania, Italy, using single-node stem cuttings of giant reed. Hydro-seeding emerged as a feasible and promising technique for switchgrass to ensure prompt seed emergence and weed control during plant establishment. Direct stem plantings of miscanthus were successful, and activated stem-buds were able to sprout in field conditions; however, timely stem transplant was determinant for shoot density and biomass yield. In giant reed, rhizome propagation showed a higher stem density and biomass yield than stem propagation; however, the yield gap was not significant from the second year onwards. Single-node rooting was mainly driven by air temperature. Nodes from basal stems showed higher rooting rates than median and apical ones. Growth regulator pretreatments enhanced rooting rate only at transplanting times under suboptimal air temperatures. In general, these experiments provided insights into propagation strategies aimed at enhancing the establishment phase of perennial grasses.

Side by side biomass productivities, harvesting time (autumn vs. winter) and frequency (annual vs. biennial) of three perennial grasses were compared under northern and southern Mediterranean climates. Miscanthus ( Miscanthus × giganteus Greef et Deu.) was compared to giant reed ( Arundo donax L.) in Catania (37°24′N, 15°03′E), and to switchgrass ( Panicum virgatum L.) in Bologna (44°55'N, 11°45′E). Generally, giant reed produced about 50% higher biomass than miscanthus in Catania. Miscanthus almost halved biomass productivity in the driest year, while giant reed reduced biomass yield by only 30% under the same conditions. In Bologna, miscanthus and switchgrass produced similar amounts of cumulative biomass over 6 years. Switchgrass kept more stable annual yields than miscanthus, which, however, evidenced a higher potential under favorable climate conditions. Autumn harvest significantly reduced biomass productivity and quality (moisture content, ashes, cellulose and hemicellulose), particularly under South Mediterranean climate. In Catania, autumn biomass was 50% (giant reed) to 85% (miscanthus) lower than winter biomass, while in Bologna, autumn cut reduced switchgrass yield by 20%. Biennial harvesting resulted in almost 40% lower cumulative biomass yield than annual cut, after 6 years.