Matricaria chamomilla L. (German chamomile) flower yield and essential oil affected by irrigation and nitrogen fertilization
Matricaria chamomilla is one of the most important medicinal herbs. The aim of this study was to investigate irrigation and N-fertilization effect on German chamomile yield and essential oil production. For the purposes of this study, field experiments were established at the Experimental Farm of the University of Thessaly, Larissa, Greece, in 2016 and 2017. The experimental design was a factorial split-plot design with main factor irrigation (I1: rainfed, I2: 100% ETo) and sub factor N-fertilization (F1: 0, F2: 80, and F3: 160 kg ha-1) with four replications. Flower yield measured by samplings at the ideal collection stage (2/3 of the rounds of tubes have been opened on the elevated flowering plant). Essential oil content was determined, using a Clevenger-type distillation apparatus and essential oil analysis by a GC-MS on a fused silica DB-5 column. Irrigation had a significant effect on yield, with irrigated treatments producing higher yield in comparison with rainfed treatments (5,250 and 2,200 kg ha-1, fresh and dry flowers, respectively). Furthermore, N-application had also a significant effect on yield, with the higher N-supply producing higher yield. The highest yield and essential oil production were found for the irrigated and fertilized treatment with the higher N-dressing (I2F3, 3,800 and 25 kg ha-1 dry flowers and essential oil yield, respectively). Moreover, it was found that the irrigated treatments produced lower amount of essential oil, while N-fertilization had a positive effect on α-bisabolol and chamazulene and a negative effect on bisabolol oxide A. Although irrigation had a negative impact on the content of essential oils, the high increase in yield led to a maximization of the essential oil production for the irrigated cultivation with maximum nitrogen fertilization. Therefore, chamomile seems to be a promising annual cultivation in Greece which can be established in areas of similar environmental conditions producing satisfactory yields.