THE CHANGES OF BOTANICAL COMPOSITION AND YIELD IN DEPENDENCE ON THE TYPE OF GRASSLAND AND FERTILIZATION

In 1993 to 1995 at Oldfichov v Hajich in the Jizera Mountains three ty pes of grasslands - renewed, slot seeded and permanent one - were stud ied. Observed the changes of botanical composition and yield were reco rded in dependence on the type of grassland and fertilization. Experim ental site, 420 m elevation, was on acid kambizem with average tempera ture of 7.1 degrees C and annual precipitation of 918 mm. The same clo ver - grass mixture composed of five components and the same sowing am ount of single components (generic hybrid Festulolium - the variety Fe lina 12 kg.ha(-1), Lolium perenne - the variety Sport 8 kg.ha(-1), Dac tylis glomerata - the variety Niva 4 kg.ha(-1), Trifolium pratense - t he variety Kvarta 3 kg.ha(-1) and Trifolium repens - the variety Huia 2 kg.ha(-1)) were used for the renovation and slot seeding. The grassl ands were divided into four variants according to the fertilization. T he first variant was unfertilized, in the second variant every year at the beginning of vegetation period 30 kg P.ha(-1) and 60 kg K.ha(-1) was applied. In the third and the fourth variants, with exception of P and K, N fertilizers in the separated dose 90, respectively 180 kg N. ha(-1), were used. The studied grassland area was cut three times and before every harvesting the portions of species were written down. The primary production of grasslands was recorded after each cutting. The original grassland seems to be the stablest as to the yield. During t he first two years the yields of temporary grasslands were the highest (fourth variant reached average 8.89 t.ha(-1) against 8.12 t.ha(-1) p ermanent grassland) (Fig. 1), but then the yield was reduced, especial ly in the first cutting, with a relatively fast floristic degradation of grassland, where a considerable succession of native species and a fast drop of sown grass species occurred. Native species of the grass, mainly Agrostis capillaris L., Holcus mollis L. and Festuca rubra L. took empty places, as regards the variants fertilized with N also Alop ecurus pratensis L. This development was slower in the variants fertil ized with N. Of the sown components Dactylis glomerata L. was kept bes t, especially in the variants with the N fertilization (about 10%), th e generic hybrid Felina had the worst result. Slot seeding did not bri ng the demanded results. The sown species, in spite of repeated seedin g in 1995, were not practically put across. The germinated plants deca yed and the vegetation was regenerated very difficult owing to bad wea ther and soil conditions. The results was the fall of covering of the vegetation and the following drop of yield of the forage (2.88 t.ha(-1 )) (Tab. I). The same species by renovation with predominance of Festu ca rubra L. were increased here. The biggest changes of species compos ition of permanent grassland were caused by using N fertilizers. By th e dose 180 kg N.ha(-1) Alopecurus pratensis L. was very increased to t he detriment of other species, in the fourth year of the observation i t reached about 75% of the portion in the grassland. In all types of. grassland the development of clover was supported with the P and K fer tilization without N (in permanent grasslands 20%), on the contrary, i n the variants fertilized with N the clover diminution and a high pred ominance of grass were recorded (Fig. 2). The whole number of the spec ies of renewed and slot seeded grasslands were kept approximately on t he same level, by the permanent grassland a slow fall was noted, mostl y in the last year of the observation (Tab. II).