Effects of different levels of cow manure and inoculation with nitroxin on growth and performance of Melissa officinalis L.

Biological fertilizers can be used as alternative for or supplementary to mineral fertilizers in sustainable agriculture. To assess the effects of organic and biological fertilizers on growth and morphological characteristics of Melissa officinalis L., a factorial experiment with 15 treatments was performed in Shahriar, Karaj, Iran, during 2012-2013 in a randomized complete block design and three replications. The factors examined were different levels of cow manure (0, 5, 10, 20 and 40 ton/ha) and inoculation with nitroxin (without inoculation, plant inoculation and soil and plant inoculation). The results showed that application of cow manure significantly increased plant height, number of leaves and lateral branches per plant, fresh and dry weights of shoots and roots, leaf surface area, leaf chlorophyll index and essential oil yield and concentration. The highest values of traits measured, except root fresh and dry weights, were obtained from the application of 20 ton/ha of cow manure and the lowest were observed in control. Our results clearly showed that inoculation with nitroxin could significantly increase the value of traits measured for Lemon balm compared to control, and inoculation of plant soil was the superior treatment.