Ecological and phytochemical response of Mentha piperita L. to Nitrogenous fertilizers types in Khuzestan region

Peppermint (Mentha piperita L.) is an aromatic medicinal plant, that its cultivation is limited due to low soil from organic matter. Therefore choose right amount and type of fertilizer is very necessary to ensure of satisfactory yield. A factorial experiment was conducted at research farm of Ramin University during 2014, arranged in CRD design contain three types of nitrogen fertilizer as the first factor: liquid (urea ammonium nitrate), powder (ammonium sulfate) and granular (Urea) which were applied at five levels: 0, 70, 140, 210 and 280 KgN/ha as the second factor with three replications. Aerial pares of plant were collected in early of blooming, the essential oils were obtained by hydro distillation method (Clevenger apparatus) and were analyzed by GC/MS. Result were showed that the nitrogen had significant effects on vegetative traits, quantity and quality of essential oil and finally on efficiency of nitrogen usage. With increases of nitrogen rate the vegetative traits and its yields of essential oil were increased. The effect of UAN was higher than U and SA, however, the trend of nitrogen usage efficiency was descended with AS of the lowest efficiency at 280 kg.ha-1. The rate and type of nitrogen fertilizers were also effective on essential oil components. The highest content of menthol was obtained in controls (37.16%) with 70 kg.ha-1 nitrogen (38.44%) but with increases of nitrogen application the menthol rate was decreased. Additionally, U and AS were respectively had the highest and lowest impact on menthol content, but in other hands the UAN application had the lowest content of menthofuran (1.17%).