Plant variation in nutrient concentrations encompasses two major axes. The first is connected to nitrogen (N) and phosphorus (P), reflects growth rate and has been designated as the leaf economics spectrum (LES) while the second follows the gradient in calcium (Ca) and magnesium (Mg) and mirrors cell structural differences. Here, we tested in grasslands whether the sum Ca + Mg concentrations is a better indicator of digestibility than LES constituents. Structural equation modelling revealed that the total effect size of N (0.30) on digestibility was much lower than that of Ca + Mg (0.58). The N effect originated predominantly from sampling date (biomass ageing), while the Ca + Mg effect largely from phylogenetic composition (proportion of monocots). Thus, plant variation in partially substitutable divalent cations seems to play a significant role in biomass digestion by ruminants. This finding contests, together with litter decomposition studies, the prominent role of the LES for understanding both fundamental ecological processes.

Summary1. Management of high-nature-value (HNV) grasslands follows agri-environmental schemes across large areas of Europe. Long-term agreements and restrictions of fertilizers cause soil nutrient impoverishment, but remarkably this quite often does not reduce biomass production. Therefore, we tested how species-rich vegetation copes with nutrient impoverishment under the most frequently used treatments, that is summer mowing and livestock grazing. 2. During 2011-2012 we studied, simultaneously, plant species composition, soil and biomass chemical properties in two equally designed experiments where mowing, grazing or leaving fallow have been applied since 2004. We asked whether soil-based (C org : N tot , plant-available P and K) and plant-based measures (N : P, N : K, K : P ratios and N-, P-, K-nutrition indices) indicate the same pattern of nutrient limitation as the observed productivity gradient. 3. Seven years of management application resulted in the lowest plant-available P under grazing and the lowest plant-available K under mowing, but neither grazed nor mown plots produced less biomass than fallow ones. Grazing supported dominance of grasses while mowing that of non-leguminous forbs. 4. Projection of nutrition indices to a common framework with nutrient ratios suggests that critical thresholds for diagnosis of nutrient limitation are a function of N deficiency. At biomass production of 2 t ha À1 a N-nutrition index of 50 yielded threshold N : P = 14Á0; hence, all our treatments with N : P of 9Á9-12Á5 should be N limited. 5. Inspecting the productivity gradient separately for each management, we found only soil C org : N tot negatively related to biomass production in mown plots indicating N limitation. However in grazed plots, positive association of biomass production with plant-available P and negative with biomass N : P and N : K suggested PK co-limitation. 6. Synthesis and applications. Mowing and grazing induced different patterns of soil nutrient impoverishment and nutrient limitation, but they did not reduce biomass production of highnature-value grasslands. Non-leguminous forbs prevailing under mowing precluded shortage of P, while grasses dominating under grazing efficiently captured N. We recommend designing agri-environmental measures that will encourage alternating mowing and grazing. This should promote coexistence of multiple forbs and grasses, balance nutrient limitation and ensure stable biomass production under future low-input scenarios.

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Fast-growing woody plants that can be grown under short-rotation systems offer an alternative to food production on arable land, and serve as a potential source of renewable energy. In order to establish the feasibility of future large scale production under the conditions of the Czech-Moravian highland, a high density experimental field plantation including a range of available clones of Populus sp. and Salix sp. with the total area of 1.5 ha was established in early 2001 in Domanínek (Czech Republic, 49°32'N, 16°15'E and altitude 530 m). The clone experiment of Populus sp. covered 0.3 ha in the center of the plantation and included 13 clones in total, with hardwood cuttings of only 6 clones available in numbers allowing 4-replicate experiment. The plantation was established on agricultural land and the trees were planted in a double row design with a density of 10 000 trees/ha. The trial was weeded by mechanical methods, and no irrigation, fertilization, or herbicides were applied. The experiment site was harvested at the end of 2006. It was found that the biomass yields of the tested clones of Populus sp. were in the higher range of results from national and European studies in case of hybrid clones. The satisfactory survival rate in the first year, when mortality tends to be highest, was supported by relatively wet weather conditions after plantation establishment. At the end of the first rotation, the highest yields were obtained from clones J-105 and J-104 (P. nigra × P. maximowiczii) and P-494 (P. maximowiczii × P. berolinensis) with J-105 showing a mean annual increment of dry matter close to 14 t/ha. Additional experiments seem to suggest that well managed poplar plantation might produce even better values if higher survival rates can be achieved.

Agri-environmental measures often require postponing of grassland defoliation until summer months. We investigated how this affects agronomic characteristics, i.e., biomass production and forage quality, in species-rich grasslands in the White Carpathian Mountains, Czech Republic. Three distinct grasslands (vegetation alliances Bromion erecti, Cynosurion cristati, Violion caninae) were selected for biomass sampling in three dates: mid-May, early June and end of June. Proportions of individual species from total biomass, biomass production, crude fibre concentration, organic matter digestibility and community functional properties (forage value, leaf dry matter content, specific leaf area) were determined. Dry matter standing biomass at the end of June was highest in Bromion with 3.5 t/ha, followed by Violion with 2.7 t/ha and Cynosurion with 2.3 t/ha. A steep decline in forage quality (increase in crude fibre and decrease in organic matter digestibility) during accumulation of aboveground biomass was recorded in formerly unmanaged Bromion grassland but remarkably not in formerly grazed Cynosurion and Violion grasslands where early spring dominants were partly replaced by later developing species, Agrostis capillaris and Trifolium spp. Abundance-weighted community functional properties were consistent with results obtained from biomass chemical analyses, thus the 'trait approach' can be used as a suitable surrogate of costly and labor-intensive laboratory procedures. Finally, we assume that the high degree of community seasonal development in Cynosurion and Violion, indicated here by a new community seasonal development index and by development in community specific leaf area, was accountable for the stabilization of forage quality later in the vegetation season.

111red clover was introduced in the European agriculture approximately 1000 years ago in andalusia, Spain and from there, its cultivation spread to other countries (Kjaergaard 2003). in the territory of the Czech republic, the red clover has been intentionally grown already for 280 years (seed purchase was first mentioned to occur in 1730) and its contribution to the intensification of cattle rearing and production of cereals has been significant (lom 1937). Before the discovery of synthetic production of nitrogen from the atmosphere in 1909 by German chemist Fritz Haber, the main source of nitrogen for agricultural crops was symbiotic fixation of red clover and other legumes. The production of synthetic n fertilizers markedly increased after World War ii, which resulted in a rapid shrinkage of red clover cropland in Europe and north america (taylor 2008). The size of clover crop fields continues to diminish on a global scale. according to rochon et al. (2004), the size of clover crop fields in Europe lessened from 9.5 million ha in 1980 to 6.0 million ha in 2000.at the present time, we can see a certain increase of interest in growing forage legumes including red clover because of increasing energy costs and deteriorating environmental effects of synthetic nitrogen use. another reason for the greater interest in clover crops is an increasing significance of organic farming and increased price of protein concentrates after prohibition of meat-bone meals in feeding animals.red clover is the most important clover crop on moist, less fertile and acidic soils while alfalfa predominates in drier regions on deep soils with neutral reaction. although the forage of alfalfa contains more crude protein as compared with red clover, the advantage of red clover is the presence of enzyme polyphenol oxidase (PPo), which improves protein efficiency during digestion of ruminants (Sulivan and Hatfield 2006) and suppresses proteolysis during forage ensiling (Pahlow 2003). red clover is suitable in mixtures with grasses that enhance ensiling capacity and reduce damage to Effect of provenance and ploidity of red clover varieties on productivity, persistence and growth pattern in mixture with grasses S. Hejduk, P. Knot Department of Animal Nutrition and Forage Production, Mendel University in Brno, Brno, Czech RepublicAbStrAct in temporary and permanent grasslands, red clover distinctly increases herbage quality and production at low fertilization requirements. Main disadvantage of this species is its insufficient persistence. There are considerable differences in persistence among varieties, which are connected with different adaptability and disease resistance. in this experiment, we assessed the production of dry forage, number of plants and growth differences in eight tetraploid and fourteen diploid varieties grown in mixture with grasses. The highest production of forage for both harvest years was achieved by Czech varieties Spurt and amos and by Swiss variety Milvus. The lowest forage production was recorded in both years in Sw...

Broad-leaved dock is together with creeping thistle (Cirsium arvense (L.) Scop.) and dandelion (Taraxacum officinale Wigg.) one of the most frequently occurring grassland weeds in the Czech Republic (Martinková and Honěk, 2001). Broadleaved dock belongs to the group of plants with the highest requirement for nitrogen and other nutrients. Its ecological requirements and herbage quality differ only li�le from those of curled dock (Rumex crispus L.) and the two species can therefore be assessed together (Weissbach, 1998). According to Klimeš (1993), there are also unfertile hybrids of the two species occurring in grass stands, referred to as R. ×pratensis. These species represent aggressive plants which force cultural grasses and legumes out from their surroundings and cause problems at herbage conservation due to their low DM contents. Humpreys et al. (1999) demonstrated that grazed swards in Britain were related to a higher mortality of docks as compared with mown swards due to lower doses of applied fertilisers, increased defoliation and trampling. High doses of N-fertilisers were put into connection with higher occurrence of Rumex obtusifolius. Novák (1994) described associations with dominating broad-leaved dock at grazing sites overfertilized with animal excrements, which can be long without any change in the species composition and which are avoided by grazing animals. In the system of organic agriculture the broad-leaved dock is a very serious problem as it cannot be controlled by herbicides and docks markedly reduce the sward nutritive value (Pötsch, 2000).With respect to the fact that sward herbages are fed on most farms in the form of grass silages, it is vitally important to know individual factors affecting their nutritive value and also the quality of fermentation process during their production. The effect of broad-leaved dock (Rumex obtusifolius L.) on the impaired nutritive value of grassland herbages was studied together with the effect of dock and addition of microbial inoculant on the fermentation process in grass silages. The herbage of broad-leaved dock exhibits low DM content, CP and fibre contents comparable with red clover, yet its NEL concentration is low. Quality of silages made of dock at DM content over 300 g/kg is good but the silages show significantly lower contents of lactic acid (35.9%), acetic acid (70.0%) and higher pH values (4.69 vs. 4.35) as compared with the grass silage. Silages made of dock do not contain butyric acid and exhibit lower rates of proteolysis. The presence of broad-leaved dock in herbage poses a danger of slow wilting and low production of fermentation acids. The addition of lactic acid bacteria (LAB) showed in the studied set of silages and in dock silages by an increased content of lactic acid (+18.9% and +27.0%, resp.) and by a significant reduction of pH value (-0.17 and -0.14, resp.).

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