Low- and high-frequency irrigation of ‘Rosso di Treviso’ Radicchio

Radicchio (Cichorium intybus L., group rubifolium) is a plant widely cultivated in Italy to sell the leafy heads. Veneto is one of the Italian regions with the largest share of Radicchio cultivation. Radicchio ‘Rosso di Treviso’ is one of the more cultivated varieties, but scientific knowledge about the most appropriate irrigation management is still limited. The study focuses on the effect of two irrigation scheduling criteria on Radicchio yield and on the number of marketable plants, in a field experiment carried out from 2013 to 2017 in a commercial farm in Veneto (northeast Italy). Mini-sprinkler system was set to provide water from the transplanting for most of the cropping period, with a low-frequency schedule, and a high-frequency schedule that doubled the number of interventions but halved the water volumes applied each time. The total volumes of water applied each year were the same in both treatments. At harvest, 7 sample areas were randomly harvested and (i) marketable yield, (ii) average head weight, and (iii) number of marketable plants were measured. Overall, the high-frequency schedule produced 26.5 t ha‑1 of marketable Radicchio heads, while the low-frequency schedule 23.6 t ha‑1, significant variability was found between years. The greater productivity was mainly the result of a greater number of marketable plants, while the average head weight was not significantly different between the treatments. This suggests that a greater irrigation interval can create less favorable conditions for radicchio yield, increasing the number of underweight, rotten and missing plants. Farmers should take into account the possibility to increase irrigation frequency if the eventual higher management cost does not offset the gain in radicchio productivity.