Stigmas yield and volatile compounds of saffron (Crocus sativus) in a late sowing under greenhouse with two nitrogen rates.

In order to evaluate the possibility of introducing saffron into a greenhouse crop cycle, in 2013-2014 the present trial was carried out in a greenhouse traditionally devoted to horticultural crops. Two treatments were studied: corm dimensions (greater and smaller than 3.0 cm) and fertilization (not fertilized and fertilized with 45 kg ha-1 of nitrogen). A late sowing (September 28) was adopted. Soil and air temperatures were recorded. Leaf number, flower number, flower calendar and stigma weight were measured. All samples were analyzed by a combination of solid phase micro extraction (SPME) and GC-FID/GC-MS. Late sowing determined a slight shift of harvest period compared to the traditional harvest in open field: stigma harvest started on November 21 and ended on December 11, for a total of 21 days. Corm dimension and fertilization greatly affected leaf number per corm and stigma yield, but not the flower calendar. The late sowing of saffron in greenhouse determined a shorter and later crop cycle and proved to better fit with the cycles of the other main horticultural crops. Volatile compounds analysis allowed us to establish that the main compound is safranal. Among the minor components are to be underlined crotonolactone, and a series of cyclohexene derivatives (isophorone, ketoisophorone 3-cyclohexene-5,5-dimethyl-2-methylene-1-carboxyaldehyde, hydroxy isophorone) which normally accompany the safranal.