Suitability of cultivated and wild cardoon as a sustainable bioenergy crop for low input cultivation in low quality Mediterranean soils

Increasing the use of renewable energies as biomass offers significant opportunities for Europe to reduce greenhouse gas emission and secure its energy supply. To ensure that bioenergy develops in environmentally-compatible way, the availability of crops, such as perennials, adapted to cropping systems based on minimal production inputs and marginal lands with medium-low soil fertility, is strongly needed. To examine the potential ability in terms of biomass, achenes, and energy yield and the possible role in soil fertility conservation of two botanical varieties (cultivated and wild cardoon) of the C3 Asteraceae, Cynara cardunculus L., a long-term experiment (seven cropping seasons) was carried out in a marginal farmland of Sicily (Southern Italy), with low soil fertility and without external inputs as fertilization, irrigation, weed and pest control from the second season onward. Under these conditions C. cardunculus improved soil fertility by increasing the soil organic matter content, organic C content, total nitrogen, assimilable P2O5 and exchangeable K, giving an annual harvestable biomass and energy yield of 14.6 t ha−1 and 275 GJ ha−1 (cultivated cardoon) and 7.4 t ha−1 and 138 GJ ha−1 (wild cardoon). The harvest time, in the third 10-day of August, allowed a very low biomass moisture, about 11% in cultivated cardoon and 7% in wild cardoon. Cultivated cardoon was capable of producing high yields until fifth season, therefore is indicated for medium long-time cropping systems. Wild cardoon showed a most stable yield pattern and plant survival over seasons, suggesting its particular suitability for perennial cropping systems of Mediterranean marginal areas. For these reasons, we have undertaken a breeding program aimed to improve the crop performances in terms of both biomass and energy yield (wild cardoon) and to stabilize the biomass production characteristics during crop ageing (cultivated cardoon).