Abstract
27 grasslands it leads to strong sward degradation after a couple of years. However, exclusively cut permanent grasslands can still be found, particularly in large wet valleys where soils are too wet in spring to be grazed. The first cut is then taken later when soils are better drained and allow for tractor traffic. If these plots are also far from farm buildings, the later regrowth can also be harvested by cutting. This situation is common in eastern Poland. Foxtail (Alopecurus pratensis) or couch grass (Elytrigia repens) are often the dominant grasses in these conditions. Mixed-used grasslands are very common either in permanent or temporary grasslands. Most extensive systems combine a hay cut with several grazing periods. Most intensive systems, usually associated with dairy systems, may combine several short grazing periods with one or two silage cuts. As explained above, alternating between grazing and cutting is a very beneficial system for both grassland plants and grazing animals. Factors affecting the botanical composition Grasslands provide ecosystem functions, such as carbon sequestration, nitrogen fixa-tion (if legumes grow in the sward), water quality preservation, biodiversity conservation , positive effects if integrated into a crop rotation (prevention of weed infestation in arable crops), cultural aspects and the provision of forage for ruminant livestock production. Due to a wide range of climates (sub-tropic to sub-arctic, from mountainous to the lowlands), grasslands appear in diverse botanical compositions. The number of species is mainly mediated by the management intensity and can range between a few species in temporary grasslands and up to very high numbers (e.g. about 70) in extensively managed grasslands. Moreover, the magnitude of these compositions is driven by the management intensity (fertilisation, defoliation frequency) and all other agronomical measures (e.g. cut vs. grazed, over-and re-sowing) at a specific site. Each species has its own requirements (functional traits) with respect to the management and site conditions and a sustainable sward is only as good as it is managed, because the grassland sward is a result of several interacting factors (Figure 1.8). In fact, all of these factors directly or indirectly affect competition between species, which is an underlying main driver of changes of the botanical composition over time. Site conditions are the basis and preconditions of productivity under the given environment, as they affect plant growth (climate, weather, soil properties) and the mechanisation potential (topography). Usually, they cannot be changed by the farmer. Utilisation form, fertilisation and sward care depend on the farmer's agronomical choices and represent different management aspects. There are farms that predominantly cut their grass, others that graze it and some that do both. Intensity refers to the number of cuts per year or the grazing intervals on one site. In cold climates, the timing of the first and the last cut influences the winter survival and the botanical composition of the sward. Nutrients affect soil fertility and thus 2013-24_grasslands2-def.indd 27 28/11/2019 15:53