Physical methods for weeds suppression in cultivation encompass many methods but our article focuses on application of various mulches. They belong to integrated non-chemical weed management strategies and are very useful in organic farming. Mulching might be performed either by the use of biodegradable mulching materials or by various mulch films. The main benefits of organic mulches are that they can be collected from the nature, thus providing cheaper crop production. In addition, they use to be biodegradable and with no harmful effects on environment. Physical methods of weed control can cause both, positive and negative effects; they certainly influence weed suppression leading to a higher yield of cultivated herbs and vegetables but if applied as living mulches in a main crop production, they compete for essential resources. In addition, apart from the weeds, living cover crop at the same time also suppress the main crop. Therefore, a great attention should be paid when selecting the most appropriate living mulch for the purpose of weed suppression in any specific cultivation. In this article, experiences with various biodegradable mulches (straw, chopped newspapers, biodegradable and photodegradable films, gravel and compost) are well described, with a special attention devoted to their use in cultivation of medicinal plants. Presented data support application of physical methods of weeds control in cultivated crops and suggest them as efficient for use in cultivation of medicinal plants.

Genetic and morphological interpopulation variability of weed species is often responsible for variable responses to herbicides. As weedy sunflower, an invasive form of Helianthus annuus L., possesses high morphological and genetic variability, very different responses of its populations to herbicides can be expected. This species is one of the dominant weed species in row crops, including maize, in many European countries in which nicosulfuron is intensively used for weed control. There are little available data about the response of this sunflower form to nicosulfuron or of the interpopulation variability of its response to other herbicides. The responses of three weedy sunflower populations to nicosulfuron were studied in field dose-response experiments, and acetolactate synthase (ALS) enzyme activity at different herbicide concentrations was determined in vitro. Interpopulation variability in the response to nicosulfuron was confirmed. Populations WS2 and WS3 were more that 20-fold and 30-fold less susceptible to nicosulfuron, respectively, than population WS1, based on fresh weight, whereas the differences were not so prominent based on other parameters, including plant height, leaf area and ALS activity, and ranged from 2 to 12-fold. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. III46008 and Grant no. 173018]

The evaluation of the inhibition effect achieved by essential oils of dill (Anethum graveolens L.), oregano (Origanum vulgare L.), juniper (Juniperus communis L.), sage (Salvia officinalis L.) and winter savory (Satureja montana L.) on seed germination and shoot growth of Johnson grass (Sorghum halepense L.) was tested in laboratory. The chemical composition of essential oils was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The major constituents were carvon (40.5%) and limonene (32.2%) for A. graveolens essential oil, carvacrol (73.7%) for O. vulgare essential oil, α-pinene (43.5%) for J. communis essential oil, β-thujone (32.7%) and camphor (17.2%) for S. officinalis essential oil, thymol (44.6%) and p-cimene (13.4%) for S. montana essential oil. The in vitro study on herbicidal activity was carried out on seed germination and shoots length of S. halepense. Essential oils of A. graveolens, O. vulgare and S. montana significantly inhibited the germination and shoot length and their herbicidal activity could be attributed mainly to their high content of carvone, carvacrol and thymol. Their essential oils reduced seed germination by 61.5%, 52.7% and 47.3%, respectively, while J. communis and S. officinalis essential oils stimulated germination (7.7% and 2.2%, respectively). The shoot growth reduction for almost all essential oils, except J. communis essential oil, was more than 30%. The solution of A. graveolens, O. vulgare and S. montana essential oils exhibited more powerful bio-herbicidal effect compared to J. communis and S. officinalis essential oils on the germination and shoot growth of S. halepense.

The aim of study was to investigate development of perennial medicinal plant, Satureja montana L., cultivated in dry farming conditions of South Banat, Serbia, with use of black permeable mulch film. In the first two vegetations, the influence of fertilization and crop density on yields of the aboveground plant part (per plant and per m 2) and on the content of total essential oil and its major constituents was observed. Overwintering survival, after late performed first harvest, and surviving ratio by the end of the second year of vegetation were 90.1% and 86.9%, respectively. Ratio between fresh and dry biomass (2.4:1) was not affected by tested treatments. The yield per plant was affected by the treatments only in the second year. Higher crop density produced 25% higher yield, while organic fertilization variant yield was 19% higher. In both years, crop density did not show significant effect on yield per unit area, while in case of fertilization, this yield was higher in organic fertilization compared to mineral in the first and the second year, 7% and 19%, respectively. The essential oil yields ranged from 0.8% to 0.9%, with the major constituent thymol (48.3-69.4%), followed by carvacrol, pcymene and β-bisabolene. The essential oil yield did not depend on treatments, while the content of major constituents was significantly affected only by applied crop density.

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