Chicory and Jerusalem artichoke productivity in different areas of Italy, in relation to water availability and time of harvest

Inulin is an important polysaccharide synthesised by different crops, which, in the EU has been included in the system of sugar quotas since 1994. Currently, one of the major problems of the agro-industry is the need to extend the length of the sugar crop harvest season. It was therefore decided, also in relation to the increased demand for inulin, to study the two main inulin producing crops in Italy (chicory and Jerusalem artichoke), to verify yield and quality potential and stability in relation to some important agronomic factors such as irrigation and time of harvest. The work was conducted in 1999 and 2000 in four areas of Italy (Udine, Rovigo, Bologna and Bari). The effects evaluated were time of harvest (3 for chicory and 2 for Jerusalem artichoke) and irrigation system (evapotranspiration replacement and dry regime, with irrigation applied only when strictly necessary) on the production of storage organs, sugars and inulin in the two crops. The highest chicory root yield was in Bologna, with an average production of 65.6 t ha-1 (fresh weight), compared to Rovigo (54.4 t ha-1), Bari (46.5 t ha-1) and Udine (38.7 t ha-1). For final tuber yield in Jerusalem artichoke, Bari was the most productive environment with an average of 80 t ha-1, followed by Bologna (61 t ha-1) and Udine (55.5 t ha-1). However, when this crop is whole-plant harvested (stalks and tubers) at pre-flowering, Bologna, with high stalk yields (58.7 t ha-1) appeared to be the most suitable environment. This type of harvesting was also shown to be more productive in terms of sugar and inulin yield. The total sugar content in the different organs analysed (roots, stalk and tubers) was always higher in Udine compared to Bologna, for both crops. Lastly, the length of the inulin chain (average degree of polymerisation [DP]) diminishes with the delaying of the harvest in both crops. The Bologna area had the highest potential in terms of chicory root production, while for the tubers yield of Jerusalem artichoke, the Bari environment was the most productive. But, when Jerusalem artichoke is instead considered as a crop for whole-plant harvest (stalks and tubers), Bologna, with a very high stalk yields, becomes the most suitable area. The highest sugar content in roots, stalks and tubers of both crops was found in the Udine trial.