## 5 Cultivation Techniques
At the end of the growing cycle, the crop helps to enrich the soil with organic matter and nutritive elements derived from the abundant mass of its residues. As this species performs a good part of its cycle in cold and rainy months, it actively explores the soil, intercepting and taking up nitrate, thus helping to limit the risk of leaching [101]. The average yields in central Europe (France-Germany) vary from 3 to 4 t ha\({}^{-1}\)[106]. The energy yield depends very much on the cultivation techniques and conditions and can vary between 4 and 44 GJ ha\({}^{-1}\) (Table 5). In terms of CO\({}_{2}\) emissions, the savings are much lower for liquid biofuels than for solid ones; for rapeseed, they are estimated to be 0.2-2.4 t ha\({}^{-1}\) year\({}^{-1}\) in CO\({}_{2}\) equivalents [107]. **Sugar beet** (_Beta vulgaris_ L.) is cultivated for the production of sugar. It has been exploited with this aim since 1700, allowing sugar, once produced only from sugar cane, to become a product for general use. The sugar produced is sucrose, a disaccharide composed of glucose and fructose. The cultivation of sugar beet particularly benefits from deep and permeable soils that are well drained. The plant has good tolerance of saline soils. The preparation of the soil for sugar beet cultivation is done following normal agricultural practices, according to the type of soil: the tap-root must be able to penetrate deep in the soil and find no (hard) layers that limit its development, while waterlogging should be avoided [108]. The yield of tap-roots varies between 45 and 50 t ha\({}^{-1}\)[101]. Bio-ethanol, bio-ETBE and biogas can be obtained from this species in elevated yields (Table 4). **Maize** (_Zea mays_ L.) is a species native to the tropical and subtropical climate zones of the American continent. Introduced into Spain in 1493, maize spread quickly in other European countries, first for ornamental purposes, and a century later as a food resource. From Europe, mainly by the Portuguese, maize was spread in Africa and Asia, while it was taken to North America by the British. Maize is a plant with a summer cycle and is sown in spring; it is sensitive to cold, especially during the early stages of development [101]. Regarding soil requirements, deep soils with pH between 6 and 6.5 are excellent for maize cultivation, which has high water requirements. Maize plants are large and have a root system that reaches to a depth of 1.5-2 m. Traditional soil preparation is based on plowing to 25 cm for loose soils and to 30-35 cm in heavy soils. Water availability is often one of the limiting factors, and about 300-400 m\({}^{3}\) ha\({}^{-1}\) of water has to be supplied for irrigation. The dry matter yield varies from22 to 26 t ha\({}^{-1}\). The grain is harvested with a moisture content of 21%-28%, usually 10-15 days after maturation [108]. Different bio-ethanol and biogas yields can be obtained when different parts of the plants are used for biofuel production (Table 4). **Cardoon** (_Cynara carntuculus_ L.), also known as the artichoke thistle, is a traditional horticultural multi-year crop characterized by high rusticity, being widespread throughout southern Europe. The cultivation is simple, as the cardoon can be propagated by seeds and normally does not need irrigation. In terms of productivity, the results obtained from experiments demonstrate that for low-input cultivation regimes, the biomass yields vary between 14 and 20 t ha\({}^{-1}\) of dry matter [109]. With regard to oil production, taking into account the average results obtained from various studies carried out in Sicily and in Spain, a seed yield ranging from 0.4 to 2.8 t ha\({}^{-1}\) is expected, with an oleic content that varies between 18% and 27%. The achenes (the achene represents the typical fruit of the Asteraceae, the botanical family to which the genus _Cynara_ belongs), where the seeds are contained, represent, in total, 30% of the dry matter of the flower heads and about 8%-10% of the total biomass [110; 111; 112; 113].