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The aim of the present investigation was to assess the influence of the accompanying grass species on the total N content in the DM of cocksfoot, timothy and perennial ryegrass. The research was conducted on the plant material collected from field experiments located in two habitats that differed in the type of soi and level of ground waters. The studied species were sown in pure sowing and in two-species mixtures (with 50% of each species). Each vegetation season, the same mineral fertilisation was applied to all the experimental objects. The plants were at the same stage of development during regrowth. Total N content was determined in the dry mass of the studied grass spccies using the Kjeldahl's method, in the year of sowing and in the following year of vegetation in the 1st, 2nd and 3rd regrowths. Cocksfoot and timothy cornpeted for nitro gen in all the regrowths, except the 1st regrowth in the dry habitat in the year sowing and both regrowths in both habitats in the year following sowing. In the year of sowing in the dry habitat neither cocksfoot nor perennial ryegrass compete for nitro gen but in the wet habitat in the year of sowing and in both habitat in the following year in all the regrowth forms, strong competition for nitrogen was found. Perennial ryegrass competed for nitrogen with timothy in all the regrowth forms except the 1st regrowth in the dry habitat and the 2nd regrowth in the wet habitat in the year of sowing.
A systematic weekly cutting of timothy grass over the period of the first regrowth allowed to evaluate the changes in yields, chemical composition as well as energetic value and organic matter digestibility over different development phases of the species. The range of the changes was presented as multi-factorial regression equations. A majority of the parameters studied had a high determination coefficient. Over the whole vegetation period yields and the fibre content were higher, while total protein, PDIN, PDIE and PDIF, as well as fat gross energy, UFL, UFY, ash, calcium and phosphorus content were decreasing. The most remarkable changes were noted the period from spreading to earing, white the magnitude of changes decreased over the period of flowering and seed maturing. The most significant changes of energy concentration and its digestibility as well as organic matter digestibility were noted at the last cuts. A significant effect of thermal conditions and the rainfall on the timothy grass development was observed in the spring time. A difference of a dozen days in the earing time was noted over the study period of four years. As results from the fibre content, a later earing time was accompanied not only by increasing yields but also by higher fibre amounts. In the same periods drought and high temperatures caused a decrease of the amount and digestibility of energy. Besides, weather conditions (cold or hot spring) changed directions of the changes of soluble sugars and fat accumulation as well as calcium and phosphorus content.
The studies were carried out in laboratory conditions. Poa pratensis root exudates were obtained in the CRETS (continuous root exudate trapping system) and then in glass platter experiment was determined their biological activity in biotest on seed germination, length of roots and height of Phleum pratense seedlings. In the experiment were used the following concentrations of Poa pratensis root exudates: 0,80%, 0,40% and 0,20%. Conducted studies showed that higher concentrations of Poa pratensis root exudates (0,80% and 0,40%) caused total inhibition of germination. Lower concentrations of exudates significantly limited number of germinated seeds and inhibited of root elongation and growth of tested species seedlings. These results indicate that Poa pratensis root exudates seem to include chemical compounds of allelopathic nature.
The experiment was carried out in the years 1982-1985 on an arable field on leached brown soil and on a permanent meadow with proper deluvial soil. The studied species Dactylis glomerata cv. Brudzyńska and Phleum pratense cv. Skrzeszowicka were grown in monoculture and in mixtures. Content of each species in the mixture was 50%. There were three cuts in the vegetation period. Two times of the first growth were cutted at the full heading of cocksfoot and at the full heading of timothy. The influence of Dactylis glomerata on the Phleum pratense shoots weight was negative and increased in the following years. It was greater on arable land than on permanent meadow. There were observed more negative effect in autumn than in spring.
The evaluation of growth and development of cocksfoot in pure sowing and in mixtures with timothy and perennial ryegrass was carried out in two habitats that were different in terms of soil kind, level of ground water, and weather conditions in the vegetation period. Experiments were located in the northern (Elizówka) and southern (Zaburze) part of the Lublin agricultural-climatic region. In the northern part, the yearly rainfall did not exceed 550 mm, whereas in the southern part it reached 650 mm. The Elizówka experiment (dry habitat) was set on brown soil, while in Zaburze (humid habitat) - on deluvial soil. The research had been carried out for 4 years. Plants were cut 3 times each year. The analysis of the growth and development of cocksfoot was carried out according to the results of shoots length measurements (their maximum range) and the evaluation of tillering intensity (total number of shoots per plant), which had been done prior to cropping of each cut. The research showed that habitat conditions, as well as the species composition of the mixtures affected the growth and development of cocksfoot. Unfavourable weather conditions in spring (negative temperature and water deficit) limited the growth and development of cocksfoot more intensively in the dry habitat that in the humid one. In the mixtures, competitive effects of the components had greater influence on the intensity of tillering than one the length of cocksfoot shoots. The length of cocksfoot shoots in mixtures with timothy was similar to pure sowings in both habitats, whereas in the humid habitat (Zaburze) perennial ryegrass weakened the growth of the length of cocksfoot shoots in the second and in the third year of vegetation. In pure sowing, cocksfoot created an average of 54.2 shoots per plant, while in the mixture with timothy an average was 64.0, and with perennial ryegrass it was 67.3 on average. Those results indicate that cocksfoot is highly resistant to competitive activity of timothy and perennial ryegrass.
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