Productivity and flower quality of different pot marigold (Calendula officinalis L.) varieties on the compost produced from medicinal plant waste

This article describes still insufficiently known technology of pot marigold cultivation with the compost produced from the organic waste of the processing of medicinal plants. For the first time the application was analyzed of different amounts of compost (control – without compost, 2, 10 and 30 kg/m2) on the morphological, productive and qualitative parameters of two pot marigold varieties (Domaći oranž and Plamen Plus). During the five-year period, the best results in both tested pot marigold varieties were achieved with the 30 kg/m2 compost application. The yield of dry flower was higher for the Domaći oranž pot marigold variety fertilized with 30 kg/m2 compost (1957.4 kg/ha) compared with the Plamen Plus variety (451.1 kg/ha). A significantly higher fresh flower yield of the Domaći oranž variety greatly influenced the increase in the quantities of examined quality parameters (total carotenoids, total phenolic, total flavonoids, and DPPH reduction), whose content was higher in the Plamen Plus variety. The artificial neural network model, was built applying the Broyden-Fletcher-Goldfarb-Shanno algorithm, exerted the adequate forecasting abilities for the productivity and quality of pot marigold flowers and the influence of compost material, produced from medicinal plants waste (R2 was 0.837 for the training period). This research demonstrates that it is possible to use organic waste obtained in the processing of medicinal plants, supporting the effectiveness of a circular economy model in the cultivation of pot marigold.