Evaluation of the effect of organic manure and compost application on growth, development, essential oil content, and microbial load in valerian (Valeriana officinalis L.)

The utilization of organic fertilizer is an effective method in organic culture of medicinal plants. The aim of this study was to determine the effect of organic manure and compost application on growth، development، essential oil content، and microbial load in valerian. The experiment was conducted in randomized complete block design with 3 treatments and 3 replications. The treatments applied organic manure and urban compost compared with control. Morphological traits and essential oil content were recorded and compared in each treatment، and root samples were analyzed for mesophilic aerobic bacteria، total coliforms، yeasts and moulds، and E. coli according to the standard guideline. Results showed that the application of organic manure increased plant leaf area، plant height، and essential oil content significantly (p <0. 05); whereas the application of compost could increase plant leaf area، fresh and dry plant weight، fresh and dry root weight، plant height، and essential oil content. Both fertilizers specially compost decreased root length significantly. The effect of treatments on essential oil content was also significant (p <0. 05)، both organic manure and compost could increase it in comparison to control. Results of microbial load analysis indicated that the effect of treatments on all microbial contamination was not significant; E. coli existence was not proved in any of، treatments and in other microbial contamination all treatments were in the same level. According to these results، the organic manure and compost application could increase essential oil content، and compost increased underground parts of plant weight more، thus increasing the essential oil yield. In microbial quality، organic manure and compost application did not increase product contamination significantly compare to control. So the application of this kind of fertilizers can be advisable in valerian culture.