[Selected biological, and productive characteristics and quality of Cynosurion spp. grasslands as affected by fertilization]

Submitted work deals with an influence of mineral nutrition and various frequency of utilization on some biological properties, productivity and feed quality of grasslands. Experimental investigations were realised on semi-natural grasslands in the region of Strazov Hills [southwestern Slovakia] in periods of the years 1976-1995. Close consideration was focused on effect of gradually increasing rates of nitrogenous fertilizers and their periodical alternation on the botanical and productional changes of grassland ecosystems in relation to fenological observations, seed production, chemical changes in grassland plants and the roll of root system under the condition of antropic pressure. Following conclusions can be formulated on the basic of achieved results: 1/ Floristic composition and its changes are affected first of all by fertilization and utilization intensity, but not also by initial cover composition of the stand. Gradually increasing intensity of fertilization sharply reduced number of species (during 4 years on the level of 61% on the average). 2/ Higher frequency of utilization shows contrary tendency, i.e. strengthens the portion of legumes, but mainly other meadows herbs in the cover with exception of high but worse regrowing species. 3/ Altering nitrogenous fertilization shows more important effect on botanical composition only in that case when after 2 years application of 300 kg/ha N further 2 years the rate of 50 kg/ha N was applied. All other combinations of altering fertilization intensity had not more substantial influence on maintenance of species diversity on the cover. 4/ Periodical altering of PK fertilization with 2 years period application of nitrogenous fertilizers insures such vitality of legumes in the cover that they are able to maintain their higher portion in it in comparison with initial cover in spite of the utilization of the highest rate of nitrogen (240 kg/ha). 5/ Productive ability of covers was influenced first of all fertilization, but in close interaction with the utilization pattern and initial cover composition. 6/ Comparison of the yield of 3-times cut covers indicated that the covers with dominance of high grasses and herb species under 3 cut utilization with increasing intensity of fertilization still more expressivelly overcome the yield of those covers which were cut 5 times. 7/ By alteration of PK fertilization with periodical 2 years application of nitrogenous fertilization within four years cycle the reached yield were not significantly lower in the course of the years comparing with every-year application of 120 kg/ha N. However, the total rate of nitrogen was substantially lower on the average of the years and the influence on floristical cover composition was more favourable. 8/ After a period of fertilization absence the dominance of floristic groups has changed on the variants fertilized with gradually increasing rates of nitrogen and on those of periodical alterational as well.The legumes are regenerating and the portion of other meadow herbs is rising too. 9/ Utilization of thermodynamic method of analysis made possible to again the basic characteristics for real determination of planning yield and the reasons of qualitative changes in dry matter. 10/ By seed production study in association of Lolio-Cynosuretum typicum the knowledge on plant populations were gained and they became the basic for some regulative pratotechnical measures potentially realizable with an aim of optimal grasslan utilization under the concrete floristic composition. Total seed production of 50 species of plant was formed on the average by 13 fertile populations. The highest 1,000 kernels weight was found out at Rhinanthus minor, Plantago lanceolata, Festuca rubra and Taraxacum officinale. 11/ Quantity vertical distribution and qualitative parameters of root system are changing in consequence of gradually increasing rates of nitrogen (+PK). PK fertilization increased the quantity of root biomass by 35% and low rate of nitrogen (60 kg/ha) by 4%. Higher rates of nitrogen (120-240 kg/ha) reduced quantity of root biomass by 8.78 - 11.65%. Portion of 82.9 - 93.6% of total root biomass was concentrated in the soil layer of 0 - 100 mm under N-fertilizing and 75.8% under PK fertilization. Seasonal changes in root production are also influenced by changes in tillering process and by this also by relations between alive and total underground biomass. Under the mineral nutrition chemical profile of roots in grassland phytocenosis in being changed. 12/ In spite of relatively large variability of collected data, chemical analyses of chosen species offered some knowledge which can concluded as follows: Species differentiation is not so signifircant as in was supposed on the basic various sources of literature. Gradually increasing nitrogenous nutrition increasing nitrogen concentration in all investigated herbs. High contents of nitrogen and other mineral elements are typical for Lathyrus pratensis, Lotus corniculatus, Trifolium pratense and Trifolium repens. Phosphorus content in herbs can be increased by gradually increasing rates of inorganic fertilizers. Calcium level fluctuates in comparison with other lements. Magnesium concentration is relatively constant. Natrium content in dry matter is very low and does not increase significantly even fertilizers application