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In the Mediterranean rainfed systems, perennial warm-season grasses are profitable crops for the production of herbage as forage or feedstock for bioenergy purposes. During summer, when the production of cool-season crops is scarce, warm-season grasses can improve the productivity and stability of forage cropping systems. In Italy, switchgrass (Panicum virgatum L.) can be cultivated for herbage production or as energy crop. The objective of this work was evaluating if relay intercropping with cool-season legumes could be suited to convert a mature stand of switchgrass from energy to dual, energy and forage, production, together with improving the productivity and the quality of the harvestable biomass. All these things considered, a field experiment was carried out in Central Italy, on mature stands of two switchgrass varieties, Alamo and Blackwell, overseeded with two legumes: sulla (Hedysarum coronarium L.) and crimson clover (Trifolium incarnatum L.). The intercropping system was compared with fertilized and un-fertilized pure switchgrass stands. After two years of study, data showed that the intercropping increased the total above ground biomass (AGB) productivity. In the second year, the increase in total AGB production for switchgrass mixtures compared with the pure stands was greater for sulla, a biennial legume, than crimson clover. [ABSTRACT FROM AUTHOR]

Giant reed ( Arundo donax L.) is a perennial rhizomatous grass producing high biomass yields in temperate and warm climates under rainfed and reduced input conditions. Harvest time and frequency typically affect the productivity and suitability for energy conversion of energy crops. In order to evaluate the effect of different cutting managements on biomass yield and quality of giant reed, three single harvest (SH) and six double harvest (DH) systems were compared. Biomass yield, leaf mass ratio, dry matter (DM), and ash content were assessed for each harvest. Over the 2 years of study, giant reed demonstrated good productivity levels both when harvested once a year and twice a year (about 30 Mg ha) without significant differences between the treatments. Regarding double-cut regimes, overall yields were significantly reduced by delaying the second cut from autumn to winter (32.9 vs 30.2 Mg ha), and the percentage of the first cut with respect to the overall yield varied from 55 to 80 %. Biomass quality was also significantly affected by harvest time and frequency. The biomass obtained in double harvest systems showed higher average moisture levels (about 40 % DM) and ash concentrations ranging from 4.7 to 8.7 %. In contrast, single harvest systems led to a drier biomass (47-57 % DM) and reduced mineral contents (3.4-4.8 % ash). The feasibility of double-cut management should therefore be considered in terms of the specific giant reed-based supply chain, with particular regards to the storage and conversion technology adopted. [ABSTRACT FROM AUTHOR]

Cropping among trees with perennial legumes is one option for increasing agro-ecosystem services, such as improving the nitrogen supply and increasing soil protection by herbaceous vegetation. Moreover, cropping under the canopy of olive trees should diversify the farm production, compared to the traditional fallow management. Among perennial legumes, alfalfa (Medicago sativa L.) produces abundant biomass under Mediterranean rainfed condition. Based on this, a two-year field experiment was implemented in southern Tuscany in a rainfed olive orchard to test the competition for light effects on alfalfa biomass production and nutritive value. Light availability under the tree canopy was measured by hemispherical photos. In both years, the alfalfa yield of under-canopy varied according to the tree presence. A significant relationship between biomass production and light availability was recorded. The nutritive value of under-canopy alfalfa was similar to that of the open-grown alfalfa. However, same significant differences did however occur, between shaded and sole crop. When differences were found, under-canopy herbage was characterised by a higher content of crude protein and a lower content of fibre with respect to open-grown. In a hilly silvoarable olive orchard, alfalfa biomass accumulation was reduced mainly due to scarce light availability, therefore tree management such as pruning and plantation layout can enhance the herbage productivity. Studying shade tolerant forage legumes in order to enhance the yield and nutritive value of herbage production in rainfed agroforestry systems is essential. [ABSTRACT FROM AUTHOR]