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Summary The quality and provenance of seed are of exceptional importance for the production and yield of cultivated plants. There are numerous tests for determination of seed vigour. The seed accelerated ageing test is one of the most important tests that provide determination of the degree of germination preservation and the seed longevity in storages. The aim of this study was to observe the effect of different production methods – organic and conventional – on seed vigour of maize (variety Rumenka), using the seed accelerated ageing test. Maize seeds were exposed to double stress conditions (temperature of 45 °C, air humidity of 100%) for 72h. Maize seed germination was determined by the standard germination test and was expressed as a percentage. The results of vigour of maize seeds organically produced indicated that the application of the seed accelerated ageing test increased the first count (78.5%) in relation to the standard germination test (70.75%), and a significantly higher percentage of nongerminated seeds (10.25%) were recorded. Furthermore, the radicle length decreased (120.75 mm), while the length of the seedling above-ground part (117.13 mm) and fresh weight (4.56 g) increased. In maize seeds conventionally produced, the first count and germination were higher (41.5% and 46.25%, respectively) after the application of the seed accelerated ageing test, while the percentage of nongerminated seeds were higher (38.75%). In addition, the length (105.88 mm) and fresh weight (4.43 g) of the seedling above-ground part decreased, while the values of the radicle length (137.5 mm), fresh weight (2.39 mm) and dry weight (0.28 mm) as well as dry weight of above-ground parts of seedlings (0.31 g) were higher than after the application of the standard laboratory method (127.88 mm, 1.89 g, 0.17 mm and 0.31 g, respectively).

Summary Over the past few years, both producers and consumers have become increasingly interested in organic farming because conventional agriculture relies so heavily on the use of synthetic pesticides, thus causing environmental pollution. Weeds, as inevitable "companions" of cultivated plants, represent a major, everlasting issue in plant production. As organic plant production is legally regulated, the control of undesirable plants such as weeds is further complicated. Using the relevant literature, the purpose of this study is to survey the existing weed control methods in organic crop production. In order to be certified, organic plants have to be grown in the farming system without the application of synthetic herbicides and other chemicals that are commonly used in conventional production. This means that crop growers have to apply non-chemical, alternative methods of weed suppression, i.e. weed control based on the combination of cropping practices, mechanical control, and the use of bioherbicides. There is a large number of plant extracts with bioherbicidal activity, the effect of which is mostly attributed to the biological phenomenon of allelopathy, rendering such weed control sustainable, inexpensive, and environmentally friendly. Although bioherbicides are successfully used in organic farming worldwide, there are no registered bioherbicides in Serbia to date (according to the data of the Ministry of Agriculture, Forestry and Water Management of the Republic of Serbia). Both organic producers and experts should raise awareness of the importance of successful weed control to the health of cultivated plants, soil, beneficial organisms, and the entire ecosystem, which requires further research attention.

Summary The central issuses in organic agricultural production are related to the plant protection sector. As the use of synthetic pesticides is not allowed in the organic system of agricultural production, biopesticides are considerd a natural, safe and environmentally friendly alternative. The purpose of this study is to identify the most important biological agents used as biopesticides in organic agriculture through a review of the relevant literature. Biopesticides are compounds made from microorganisms and various natural materials of plant and animal origin. Biological protection also includes the use of extracts of different plant species (such as essential oils) that have toxic effects on plant pathogens. This paper accounts for the most important types of biopesticides based on bacteria, fungi and viruses, which are licensed for use in the Republic of Serbia according to the Law on Organic Agriculture. Their mechanisms of action, possibilities of application and efficiency are described in the present study. The bacterium Bacillus subtilis is the most studied bacterial species used in biological protection, whereas the species Bacillus thuringiensis is predominantly used for the control of harmful insects. There is no doubt about the need for alternative protection systems in the future, which necessitates further scientific research. A sound application of biopesticides in combination with preventive protection measures would meet the requirements of safe agricultural production.