Effect of foliar fertilization on Urospermum picroides, an indigenous plant of the traditional cretan-mediterranean diet

Abstract

Urospermum picroides (L.) Scop. ex F. W. Schmidt (Asteraceae) is rich in secondary compounds, with antimicrobial and antioxidant activity, medicinal and health-promoting properties, however, like many other wild edible plants of the Mediterranean, it is still underutilised. This study focused on the pilot cultivation of U. picroides, under minimal irrigation and organic, integrated nutrient management (ΙΝΜ) fertilisation (by foliar application) in Crete, Greece, analysing its response in terms of yield characteristics and nutritional content. The foliar fertilisation treatments consisted of a control treatment (CO), a conventional water-soluble fertiliser (CV), a semi-organic nitrogen fertiliser (TR), a liquid semi-organic fertiliser (TF), and v) a mix of the conventional and semi-organic fertiliser (CF). Physiological characteristics (i.e., SPAD and Fv/Fm) were assessed during cultivation, while yield and leaf nutrient parameters were determined, at harvest. Treatments containing bioactive compounds (TF and CF) almost doubled the fresh and dry weight of U. picroides shoot compared to the control (CO) treatment (172% and 160%, respectively) which can be partially ascribed to the elevated physiological characteristics of the TF and CF fertilisation treatments. Even more, nitrogen rich treatments (CV and TR) improved yield characteristics compared to the control, but the effect was not as pronounced as that achieved by TF and CF semi-organic fertilization treatments. Our results indicate that the application of foliar semi-organic fertilization seems to be an effective alternative practice to increase photosynthetic capacity and concomitantly fresh and dry yield of U. picroides without compromising the nutritional profile of the edible product.