Učinak ekstrakata koprive (Urtica dioica L.) na vegetativni rast, sastavnice prinosa i kemijski sastav graha mahunara (Phaseolus vulgaris L.)

One of the main challenges in modern agricultural production is how to produce healthy food that meets the needs of a growing population without compromising natural resources. In addition to synthetically produced chemical fertilizers, organic fertilizers are increasingly being explored, in order to support the yield as well as nutritional values of agricultural crops. The most commonly used organic fertilizers are manure, dehydrated organic fertilizers and compost. Organic fertilizers are often combined with various botanical preparations (herbal aqueous extracts) from wild and/or medicinal plants that can stimulate plant growth and development, while strengthening plants' resistance to abiotic and biotic stress. The main disadvantages of these ecological and botanical preparations are variations in their chemical composition, lower and shorter period of efficiency . Depending on the crop species,various medicinal plant preparations are used as fertilizer (bio-fertilizer) and can also act against pathogens and pests (bio-pesticides). Nettle (Urtica dioica L.) is a wild grow and easily available medicinal species, which can also be grown as a cultivated species, making this plant as a great potential for the aquatic extract production. It has long been known that a short-term nettle extract is used as a bio-insecticide, while a long-term nettle extract has a fertilizer effect. There is a lack of scientific research analyzing the impacts of a short-term aqueous extract as bio-fertilizer. The goal of this research was to analyse the effects of long and short aqueous nettle extracts on the chemical composition, vegetative parameters and yield component of green bean (Phaseolus vulgaris L.). The field experiment was established at two climatically and pedologically different locations in Croatia (Zadar and Porec) during two growing seasons (spring and autumn). A short extract (KE) was prepared by extracting dry nettle (183g/10L of water) for 24 hour; a long extract (DE) was prepared in the same ratio with water, but for 14 days. Both extracts were diluted before application in a ratio of 1:3, KE was applied foliarly, and DE by soil watering. The experiment was set up according to a randomized block schedule (RCBD) in four replications. These treatments were performed on experimental plots in one, two or three treatments of green bean during the growing season, and compared with plots fertilized with urea nitrogen fertilizer (46% N) and control variants without fertilizer application. The impact of fertilization treatments was variable with respect to location and growing date. All vegetative parameters and yield, then total phenols, antioxidant activity and the amount of minerals (P, K, S and Mn) in green bean were significantly higher at the location Porec, as a result of the initial higher values of some soil fertility properties. Autumn cultivation was more favorable for the vegetative parameters of plant growth, but not for the yield and size of pods. The phenol content and antioxidant activity in green bean were higher in autumn cultivation, the same as amounts of P, Mg, S, Fe and Mn. As expected, urea mineral fertilization resulted in significantly higher values of most vegetative parameters, but justifiably higher antioxidant activity and more total phenols were achieved by variants fertilized with long extract twice during bean vegetation (DE2). Comparing the aqueous extracts of nettle with each other, foliar fertilization of KE proved to be almost as effective on the vegetative parameters of green bean as the application of DE through the soil. Organic nettle fertilization resulted in a higher amount of Fe in the herb of green bean compared to plants fertilized with urea.