Response of herbage yield, essential oil yield and composition of South African rose-scented geranium (Pelargonium sp.) to conventional and organic nitrogen

• Published in: The Journal of essential oil research 2006, Vol.18 (sup1), p.111-115
• Main Authors: Araya, H.T, Soundy, P, Steyn, J.M, Teubes, C, Learmonth, R.A, Mojela, N
• Format: Article
• Language: English
• Subjects: aromatic hydrocarbons; chemical composition; citronellol; citronelly formate; composts; conventional tillage; crop yield; essential oil composition; essential oils; experimental design; fertilizer application; field experimentation; forage; Geraniaceae; geraniol; Geranium; guaia-6,9-diene; harvest date; odor compounds; organic nitrogen compounds; Pelargonium; Pelargonium sp; yield components
• ISSN: 1041-2905; 2163-8152
• DOI: 10.1080/10412905.2006.12067130

A field experiment was conducted on rose-scented geranium in Pretoria, South Africa, to evaluate the response of plants to amount and source of N. Treatments consisted of two sources of N, comprising conventional or organic fertiliser sources at 100, 200 and 300 kg/ha N/year and a control (zero kg/ha N/year). The experiment was laid out in a randomized complete block design. The oil content of the plants (sub sample of 10 kg from each treatment) was determined by steam distillation and oil samples were analyzed by gas chromatography (GC). At the first harvest (summer/autumn), there was no significant effect of conventional N on fresh herbage and oil yield, probably due to leaching of N by rainfall. However, organic N at 100 kg/ha increased fresh herbage and oil yields by 57.5% and 47.9% over the control, respectively. In the second harvest (spring/summer), fresh herbage yield increased by 46.3% (conventional N) and 60.3% (organic N) at 100 kg/ha compared to the control. Compared to the control, 100 kg/ha conventional and organic N also increased essential oil yields by 93.6% and 129.4%, respectively. Increasing N levels of both sources increased citronellol percentage, in the first harvest. In the second harvest, organic N increased citronellol percentage, whereas conventional N had no effect. In both harvests, no effect of conventional N was observed on geraniol percentage compared to the control. Except for the 100 kg/ha level, the same was true for organic N. In the first harvest, application of conventional N beyond 200 kg/ha and all levels of organic N reduced guaia-6,9-diene percentage, while in the second harvest, it was not significantly influenced by either source or level of N. This study revealed that rose-scented geranium produced higher fresh herbage and essential oil yield when organic fertilizer was used as a source of N. Furthermore, N application influenced oil composition.