PERMANENCE OF SOWN SWARD SITUATED ALONG THE SLOPES OF THE CENTRAL BALKAN MOUNTAIN

: The state of mixed swards of red fescue, Kentucky bluegrass and bird’s foot trefoil was studied. The experiment was situated along the slopes of the Central Balkan Mountain, during the period of the 1st to the 13th year of their creation. At a high degree of soil gleying, the low part of the slope, the dry matter yields were within the limits of 2.8 t/ha (1997, south-eastern exposure) up to 10.66 t/ha (1999, north-eastern exposure). At a low degree of soil gleying, high part of the slope, the dry matter yields were within the limits of 2.34 t/ha (1994, western exposure) up to 14.34 t/ha (1995, east exposure). The most prominent in productive terms for the period of the study are the variants at the east and south-eastern exposure, slightly gleyed soil. The participation of the sown species in the total forage yield is variable quantity. They reach (at their most) up to 96% in 1998, north exposure, slightly gleyed soils and up to 97% in 2000, north-east exposure, highly gleyed soils. Their share was small in 2004 (44%) and in 2006 (42%) on a western slope, highly eroded soils.


Introduction
In the previous study (Mitev et al., 1992) a number of positive results have been determined in the growing of mixed sward of red fescue, Kentucky bluegrass and bird's foot trefoil of local origin, which are a subject of patent work. We share the view of some authors that the combination of certain species could ensure priority of the mixed swards through better use of the resources of the environment (Sanderson et al., 2001). The combination of components in the swards, as well as the determining of their number should be a result from their behaviour in the conditions of the habitat. When the number of components was increased from 2 to 3, the aggressiveness in the system raised fourfold (Mitev and Petrov, 1999). D. Mitev et al. 510 The aim of the study was to estimate the permanence of a mixed sward consisting of red fescue, Kentucky bluegrass and bird's foot trefoil with a local origin during the thirteen years period, along the slopes of the Central Balkan Mountain.

Materials and Methods
The conditions of creation and conducting of the experiment were described in the methodical part of a previous publication (Mitev and Belperchinov, 2000). The main feature in it is the spreading of swards of red fescue, Kentucky bluegrass and bird's foot trefoil along the foothill slopes at a different disposure against the four cardinal points under correspondent soil differences, insolation etc. The variants are given under the enclosed tables. Data were processed by statistical software Stratgraphics Plus v.2.1, with analysis of variance (ANOVA) and multiple comparison of mean values through the smallest statistically proven differences (LSD 0.05).
The dry matter yield and botanical composition of swards were studied. In relation to soil, the region belongs to the foothill subzone of Northern Bulgaria forest-steppe zone, about which is typical the significant presence of pseudopodzolic soils. Pseudopodzolic horizon (A 1 ; A 2 ) has a thickness of 30 -40 cm and it is saturated abundantly by gleyic spots and iron-manganese concretions. Illuvial horizon (B 1 ; B 2 ; B 3 ) has a thickness of 80 -100 cm and it is abundantly saturated at the top with light grey and rusty gleyic spots. Brown and brownyellowish tones are predominant in the lower parts (Palaveev and Totev, 1983).
The experiment was established in 1994 in a randomized complete block design with four replicates, and a plot size of 4 m 2 . After the autumn ploughing in depth of 18-20 cm and the following pre-sowing procedures, 800 germinating seeds were sown at 1m 2 of local populations of red fescue, Kentucky bluegrass and bird's foot trefoil in equal proportions. Each of the above mentioned species participate with 1/3 of its sowing rate for creation of independent swards. Sward was fertilized with N (80 kg/ha) annually and with P (80 kg/ha) every second year, starting from 1995. The dry matter yields were studied in the following way: green mass samples were dried at 105 o C till a permanent weight was reached. The dry matter yield was recalculated on the base of the determined percentage proportion. Тhe botanical composition of swards was determined in the following way: four plant samples were taken from random places in the diagonals of the plots from each variant, for each replication of the experiment, till the weight of the pattern of Permanence of sown sward… 511 two kilograms was reached. The botanical composition of swards was determined in this sample. The swards were cut at the phase of beginning of flowering of legume. Variants A 1 and B 1 were accepted as a control, which was conventionally chosen (Iglovikov et al., 1971). The average amount of precipitation for a period of 35 years  was 737.3 mm. It was closer to that in 1994, 1995, 1998. In 1996, 1997, 1999, 2001, 2003 the precipitation was less in comparison with the average for the region. In 2002In , 2004In , 2006 it was greater. Particularly significant were the differences in 2000, when the precipitation was almost the half in comparison with the average for the region. In 2005 it was almost twice as high. The average annual temperature  for the region was 9.7°C, and for the vegetation period March-October 13.6°C. It was lower in 1996, 1997, 2000, and higher in the rest years.

Results and Discussion
At a high degree of soil gleying, low part of the slope, the dry matter yields were within the limits from 2.8 t/ha (1997, south-eastern exposure) to 10.66 t/ha (1999, north-eastern exposure) (Table 1). At a low degree of soil gleying, high part of the slope, the dry matter yields were, in the range, from 2.34 t/ha (1994, west exposure) to 14.34 t/ha (1995 eastern exposure). The most prominent in productive terms for the period of the study were the variants at south-east exposure, slightly gleyed soils.
On a slope at south-eastern exposure with heavily gleyed soils the highest productivity was recorded in 2002 (9 th vegetation). During the last three year period (2004)(2005)(2006), the productivity of that variant was higher than that in the previous periods. In a previous publication was presented the thesis that each 'structural unit' (….species, population, variety, ...) probably has a specific energy configuration where a proper energy balance is achieved, which allows the formation of a specific "projection in Time" (including permanence in ontogenetic and phylogenetic aspect), which in a peculiar way is included in the cycle of nature. In this situation, the use of the environmental factors is strictly individual, and a part of them remains conditionally not mastered for ever. The access to them from the part of the plant material, the sustainability of the development of the swards, and so on differ (Mitev, 2004;Mitev and Naydenova 2012). In this case it is not difficult to assume that the components in a sward interact on "time level", creating peculiar "energy-informational systems" with their corresponding durability (Mitev and Naydenova, unpublished).
The botanical composition of the swards manifests the sustainability of their development ( Table 2).
The participation of the sown species in the total forage yield is a variable. They reached up to 96% in 1998, north exposure, slightly gleyed soils and up to 97% in 2000, north-eastern exposure, highly gleyed soils. Their share in the initial and final period of the study usually is smaller: 29%, north exposure, low degree of soil gleying, 1994; 36% west exposure, highly eroded soils, 1994; 42%, west exposure, highly eroded soils, 2006. The red fescue is a predominant species in the swards. In previous publications has been mentioned that the participation of red fescue reached up to 84% in 2004, north exposure, slightly gleyed soils (Mitev et al., 2006). It had 89% from the total yields at north-eastern exposure, highly gleyed soils, in 1998 (Belperchinov andMitev, 2004).
The presence of weeds was higher in low level of soil gleying, at a high part of the slope. It should be noticed that the species, included here, are not Setaria viridis (L.) P.B., Setaria glauca P.B., Agropyrum repens (Scop.) etc. We found the presence Galium aparine (L.), Galium tricorne (With), the broadleaf plantain (Plantago major L.), narrowleaf plantain (Plantago lanceolata L.) etc., which are characteristic for the neighbouring natural swards. These species are herbs that have a positive influence over the animal organism, respectively over the human one.  9  13  14  11  12  20  32  5  2002  sown species  88  92  84  43  84  90  69  92  weeds  12  8  16  57  16  10  31  8  2003  sown species  89  58  61  94  89  85  86  82  weeds  11  42  39  6  11  15  14  18  2004  sown species  73  72  -94  83  64  44  88  weeds  27  28  -6  17  36  56  12  2005  sown species  72  87  -78  81  84  91  51  weeds  28  13  -22  19  16  9  44  2006  sown species  88  64  -71  86  81  42  weeds  12  36  -29  14  19 58 -A1 East exposure with a high degree of soil gleying (Control of A); A2 South-east exposure with a high deg. The mentioned species, as well as the other self-sown meadow grasses and legumes, with a local origin such as white and hybrid clover, etc, display the level of balance in the system, as well as the change in the balance. The specificity of the interrelation among productivity and the category of the so called weeds impose a careful analysis according to the type of swards, as well as continuation of the experiment in the future.

Conclusion
The opportunity for prolonged use of artificial meadow wards has been found in the slopes of the Central Balkan Mountain.
At a high degree of soil gleying, low part of the slope, the dry matter yields were within the limits from 2.8 t/ha (1997, south-eastern exposure) to 10.66 t/ha (1999, north-eastern exposure).
At a low degree of soil gleying, high part of the slope, the dry matter yields were within the limits from 2.34 t/ha (1994, west exposure) to 14.34 t/ha (1995 eastern exposure). The most prominent in productive terms for the period of the study were the variants at east and south-east exposure, slightly gleyed soils.
The participation of the sown species in the total forage yield is a variable quantity. They reached up to 96% in 1998, north exposure, slightly gleyed soils and up to 97% in 2000, north-eastern exposure, highly gleyed soils. The grass components, and especially red fescue, are predominant in the swards. The presence of self-sown other legumes of local origin was determined, such as white clover, hybrid clover, etc.
Weed infestation, in view of the durability of swards (1st -13th year since their establishment) has been slight.