No abstract

A pot experiment with an additive design and three series was conducted to test competition between spring barley and Italian ryegrass under different soil moisture conditions. The experimental factors were as follows: 1. type of sowing – mixed sowing and pure sowing; 2. water supply – plants supplied with water to meet their full requirements and 50% water supply reduction. The study covered five phenological development stages (BBCH) of spring barley: emergence (10–13), tillering (22–25), stem elongation (33–37), heading (52–55), and ripening (87–91). The competitive effects were evaluated based on relative yield (RY), relative yield total (RYT), competitive balance (CB), and relative efficiency index (REI). Spring barley and Italian ryegrass competed for resources throughout the growing season. Competition intensity was found to increase until the heading stage, and it decreased towards the end of the growth cycle. More intense competition was observed under reduced water supply. Spring barley dominated over Italian ryegrass from the tillering stage to the ripening stage. In mixed populations, Italian ryegrass captured the available resources more effectively than spring barley from the stem elongation stage until the end of the growing season, particularly in the treatment with optimal water supply

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The paper analyses the weeds community in oats cultivated at different position in two crop rotations: after potato (in the rotation system with 25% share of oats) and twice after oats (with its 75% share) during the years 1990-2000, using the diversity of species indicators (by Simpson and by Shannon-Wiener), homogeneity of species by Simpson and communities similarity ratios. The dependence of biological indicators on the weather conditions and the dependence of oats grain yield on the number and diversity of species were assessed. Diversity and homogeneity of species in communities of weeds in the field of oats showed high differences from year to year of studies and dates of measurements (stage of oats tillering, end of its vegetation). To a lesser degree they changed under the influence of the position in the rotation system. With the passage of years the number of weeds during the spring period gradually increased. The analyzed parameters showed the differentiated dependence on the weather conditions. The communities form years with similar weather conditions did not show analogy in individual density and species. No significant dependence between the yield and the diversity of weeds was confirmed

S u m m a r yCompetitive interactions between spring wheat and spring barley were traced based on a pot experiment. In the years 2003-2004, three cycles of the experiment were carried out in a greenhouse. Two spring cereals -wheat and barley, sown in a mixture and in a monoculture, with different mineral fertilisation levels, were the object of evaluation and comparison. The experiment was set up according to the additive scheme, determining dry weight values for both species in 5 growth stages (emergence, tillering, shooting, heading and ripening). Results were used to determine relative yields and competition ratios. It was demonstrated that competition between the cereals started already from the emergence stage and lasted till the end of vegetation, manifesting itself with the greatest strength at the heading stage, but thereafter it weakened in the NPK poorer environment. Access to a larger pool of macroelements resulted in the intensifi cation of competitive interactions. Spring barley used the limited growth factors better than wheat from shooting till the ripening period, and a reverse relation was exhibited only at the tillering stage.