Hossein Ayyobi - Horticultural Department, Faculty of Agriculture, University of Guilan, Rasht, Islamic Republic of Iran
Jamal-Ali Olfati - Horticultural Department, Faculty of Agriculture, University of Guilan, Rasht, Islamic Republic of Iran
Gholam-Ali Peyvast - Horticultural Department, Faculty of Agriculture, University of Guilan, Rasht, Islamic Republic of Iran

Background The utilization of organic fertilizer is aneffective method in organic culture of medicinal plantsbecause of its beneficial effects on soil structure,reduction of environmental problem and improvement inplant growth. The experiments were conducted in aresearch field at the University of Guilan at the Rasht andTorbat-e-Jam Razavi Khorasan Province, Iran. Theexperiment was conducted to determine the effects of7 Mt ha-1 of cow manure vermicompost, vermiwashprepared from 7 Mt ha-1 of vermicompost, leachatevermicompost ? vermiwash, 50 Mt ha-1 municipalsolid waste compost (MSWC), chemical fertilizer (50, 0,300 NPK) and no fertilization as a control on peppermintyield and quality.Results Organic fertilizers significantly affected all themeasured characters except total phenols and antioxidantcapacity compared to chemical fertilizers and the control.Plants treated with vermicompost, vermiwash or vermicompostleachate ? vermiwash were the tallest and hadthe highest levels of chlorophyll a, chlorophyll b, totalchlorophyll and carotenoids. Plants treated with vermicomposthad the highest essential oil yield (24.21 ml m-2).Plant growth in the Rasht region had the highest number oflateral branches (18), fresh (10.51 g) and dry weight(4.64 g) of plant, fresh (2,102.9 kg ha-1) and dry(928.67 kg ha-1) yield, leaf area index (0.17) and carotenoids(531.82 mg 100 g-1), while the highest oil per plant(0.24 ml plant-1) and oil yield (18.49 ml m-2), chlorophylla (7.37 mg 100 g-1), b (4.07 mg 100 g-1) and totalchlorophyll (11.44 mg 100 g-1), total phenol (7.48 mggallic acid equivalent 100 g-1) and antioxidant capacity(71.89 (% of inhibition) were obtained from plants grownin the Torbat-e-Jam region.Conclusion Organic fertilizers beneficially affect soilstructure and nutrient availability. The use of sustainableorganic materials can increase fertility without negativeeffects on human health and environment. We counselfarmers to use leachate vermicompost and vermiwash inorganic cultivation of peppermint separately or mixedtogether.

Vermicompost Medicinal plants Organic culture Essential oil