The Effect of Organic Fertilisers on the Floristic Composition of Grassland, Herbage Yield and Quality

The aim of this study was to assess the effects of organic fertilisers (cow manure + dung water; cattle slurry) applied in different annual doses of nitrogen (54 kg ha-1; 84 kg ha-1; 120 kg ha-1) according to 3 different intensities of grassland utilisation (extensive – 2 cuts per year, medium intensive – 3 cuts per year, intensive – 4 cuts per year) on percentage of plant functional groups (grasses, legumes, forbs), dry matter yield, and forage quality. The study was performed as a smallplot trial over 7 years on moderately moist grassland in the Czech Republic. The proportion of legumes was significantly higher in the fertilisation treatments with cow manure + dung-water combined with medium intensive utilisation and intensive utilisation (10.2% and 10.3%, respectively). Fertilisation significantly increased dry matter yields by 51.9 % (cow manure + dung water) and 56% (cattle slurry) compared to unfertilised controls (4.81 t ha-1). Grasslands fertilised with cattle slurry showed significantly higher concentration of crude protein (142.9 g kg-1) than unfertilised (126.4 g kg-1). Extensive grassland utilisation significantly increased crude fibre concentration (up to 282.1 g kg-1), and decreased the energy value (up to 4.68 MJ kg-1 of NEL). Organic matter digestibility was negatively influenced by extensive grassland utilisation (61.0%, 65.42 % and 67.44% for the extensive, medium intensive and intensive utilisation, respectively). Our findings suggest that medium intensive and intensive grassland utilisation using organic fertilisation which correspond to annual doses of nitrogen of 84 kg ha-1 and 120 kg ha-1, are the most suitable for animal nutrition.

conditions [3][4][5]. As a result, great variability is seen in floristic composition of the vegetation and hence the productivity and quality of forage produced from these categories of agricultural land [6].
The productive potential and quality of permanent grasslands can be increased by different fertilisation regimes and types of mineral/organic fertilisers. A typical characteristic of fertilisers is that they affect (directly and indirectly) the growth and development of plants [7]. Freely available chemical fertilisers over the past half-century resulted in a period in which efficient nutrient recycling was not prioritized. However, the emphasis on organic fertilisers as a nutrient resource has been reestablished following recent increases in fertiliser prices, more focus on manure management within the European Union (EU) and national environmental policies [8].
Organic agriculture relies on ecosystem management and ecological processes rather than on the external flow of agricultural inputs [9]. Synthetic inputs are replaced with site-specific management practices to balance input and output nutrients to ensure short-term productivity and long-term sustainability. Hence, organic fertilisers are the irreplaceable foundation for rational agriculture. If applied rationally to grasslands, they can entirely replace mineral fertilisers. In addition, organic fertilisers support soil fertility and have other positive effects [10]. Cattle slurry, in particular, is a commonly used fertiliser in many countries and its effects on grassland have been studied [11,12].
In the Czech Republic, the systematic use of organic fertilisers in permanent grasslands is not common because of their preferred application to intensive arable crops. However, their importance is progressively increasing mainly in connection with the development of the organic sector which induces a spatial decoupling of livestock and crop production. Existing methodological recommendations for application of organic fertilisers in the Czech Republic do not take into account Arrhenatherion [14]. Before the experiment setup, the grassland had been used for cattle grazing for over 30 years. applied early in spring and the second 50% after the first cut. Cow manure was applied in autumn, dung water after the first cut. The fertilisers were analysed for nutrient content before application which was annually during 2005-2011.
The plots were cut 2-4 times per year depending on the given dose of fertiliser. Unfertilised plots (F-0) with three types of utilisation were also observed as the control treatments: two-(extensive), three-(medium intensive) and four-(intensive) cuts per year. Treatments as fertilisation and cutting regime are shown in Table 3.   [16]. The energy value (MEmetabolisable energy; NEL -net energy of lactation) was predicted using the equations officially accepted in the Czech and Slovak Republic, which corresponds with the system INRA [17]. The long-term application of organic fertilisers resulted in significant changes in sward floristic composition in the studies of [11]) too.
[23] investigated the effects of different fertilisation systems (organic and mineral fertilisers) on permanent grasslands and found that fertilisation with slurry increased the proportions of grasses, whereas farmyard manure increased forbs; the proportion of legumes was increased by PK and by fertilisation with slurry plus lime. [24] reported that cattle slurry decreased the proportion of legume species, increased the grass proportion but barely affected the non-leguminous herbs in grasslands.
Differences in findings could be caused by different soil-climatic conditions and types of grasslands of experimental study sites and also by treatment differences (e.g. doses of manures, modes of application etc.).

Dry Matter Yields
Data for dry matter (DM) yields of grasslands by management, as well as the significance of differences are given in Table 5. Significantly higher DM yields were found for the fertilisation treatments. Cow manure + dung water increased DM yield by 51.9% and cattle slurry by 56.0%, compared to unfertilised control (4.81 t ha -1 ). Differences between the types of organic fertilisers used (cattle slurry vs. cow manure) on DM yield were not significant in our study. However, we found a slightly higher DM yield in the slurry treatment (7.51 t ha -1 ) than in the fertilisation treatment with cow manure + dung water (7.31 t ha -1 ).
We also found an effect of intensity of utilisation in our study. In the grasslands utilised extensively (two cuts per year) fertilised with the lowest doses of organic manures, we found a significantly lower mean DM yield (6.14 t ha -1 ) in contrast to grasslands with medium intensive and intensive utilisation (6.82 t ha -1 and 6.68 t ha -1 , for three and four cuts per year, respectively). This finding is not in agreement with [25] or [26], who documented that the treatment of 4 cuts is unfavourable in terms of production, which was explained in relation to the phenological development of the swards. Our results demonstrated that DM yields were significantly influenced by level of organic fertilisation. This is in accord with [27,19,10,28]. [29] who investigated via the same experiment at two different localities in the Czech Republic (Jevíčko, Vysoké nad Jizerou) had similar results. In contrast, [30]) found that the addition of organic manure produced no increment in DM yields, which was probably caused by significant changes in the floristic composition.  Table 3 In our study, DM yields were also affected by annual climate. It can be seen from Table 1 (Table 5 and Table 6). From Table 4 it is clear that the exceptionally dry year 2007 also had an effect on the floristic composition (significantly higher proposition of grasses to the detriment of forbs), which is in line with [31]. [32] found that the quantity of annual herbage DM yield correlated highly with the amount of precipitation during the March-August period. This finding is also described in relation to climatic conditions by [33].

Forage Quality
Regarding the effect of different grassland management on forage quality (Table 6) These results on forage quality are in agreement with [30], who found that the fertilised (including organic fertilisers) swards produced 55-60% more protein.
[34] conducted experiments on the influence of organic fertilisation on content of crude protein, crude fiber, phosphorus and raw ash. The applied fertilisation systems resulted in an increased fodder yield and CP content, compared with the unfertilised control, by 14-29% on Nardus stricta grassland and by 9-22% on Agrostis capillaris + Festuca rubra grassland.
Intensive grassland utilisation is usually connected with a decrease in DM yield and simultaneous increase in forage quality [25]. Within our study, we found that higher doses of organic fertilisers (especially cattle slurry) and increasing grassland utilisation had a more significant effect than intensity of utilisation. Our finding could be explained by the fact that cattle slurry provided a source of fast-release nitrogen which could be immediately utilised by the plants for their growth. As [35] have reported, slurries typically contain more inorganic than organic N, whereas most of the inorganic N in slurries is present as N-NH4 + . types of organic fertilisers significantly increased DM yields, even though the treatments with higher doses of fertilisers were utilised more intensively.
Appropriate grassland management through the number of cuts and fertilisation enable improvement in floristic composition, and amount and quality of forage. In our study, cattle slurry significantly increased the concentration of crude protein in dry matter compared to unfertilised control. Extensive grassland utilisation significantly affected the increase in concentration of crude fibre, and decrease in energy value as well as organic matter digestibility.
Our findings suggest that medium intensive (three cuts per year) and intensive grassland utilisation (four cuts per year) and fertilisation with organic fertilisers, which correspond to 84 kg N ha -1 year -1 and 120 kg N ha -1 year -1 , are the most suitable management practices from the viewpoint of animal nutrition. There are other relevant environmental factors that could influence these parameters, including climatic conditions, which are different for each locality and vegetation season.
For specific sites, it is necessary to take into account the possible environmental risks, which could arise from the use of high doses of organic fertilisers (e.g. decrease in species diversity, leaching of nutrients into ground water).