Condition and changes in types of natural pasture swards in the Sakar mountain under the influence of climatic and geographic factors

V. Vateva, K Stoеva, D. Pavlov
Abstract. The research focuses on the vegetative development, the state and changes of the types of natural pasture compositions from the Sakar mountains region, by tracking the influence of the climatographic factors. The favorable combination of climatic indicators and the good water ensure the normal vegetative development of the natural pasture compositions and grassland, and in the different kinds of pastures their height varies from 40 to 71 cm. The unfavorable manifestation of the climatographic conditions negatively affects the vegetative development of the pasture compositions. It changes the composition and ways of usage, and the height reduces by 15 to 32 cm. The most significant changes are observed in pasture-type Andropogon ischaemum, in which the height decreases by 32 cm, and the composition of the pasture grassland considerably degrades. Weaker affected by the changes in the climatic parameters are the pastures type Cynodon dactylon – Lolium perenne and Festuca myuros – Bromus sp., due to the larger percentage of drought-resistant species, which constitute them. Water supply in the months April, May and June exercises stronger influence on the grass height than the rainfall amount during the entire vegetation period.


Seasonal and vertical dynamics of the water temperature and oxygen content in Kardzhali reservoir, Bulgaria

I. Iliev, L. Hadjinikolova
Abstract. The aim of the study was to determine the seasonal and vertical dynamics of water temperature and oxygen content in the aquatory of Kardzhali Reservoir, situated in the Eastern Rhodope Mountains at the altitude of 290 m. Water samples from six sampling stations, set in order to fully cover the water area near the cage farms; the aquatory free from net cages and the part near the dam wall were analyzed. In the surface layers for the period of the study, the water temperature ranges from 11.8°C to 25°C respectively in April and in July. With the increase of the air temperature in spring, the surface water layer is heated rapidly. The zone of the temperature shift (thermocline) of the stratifying lake is especially clearly observed during the months May – September between 5–15 meters. During the period of the study were established significant variations in the oxygen content in the water between 2.98 mg.l-1–13.66 mg.l-1 (0.5 m) and 0.16 mg.l-1 –10 mg.l-1 (30 m). The highest average values of this parameter in vertical in the range of 10.47 mg.l-1 were reported in April.


Manganese levels in water, sediment and algae from waterbodies with high anthropogenic impact

V. Atanasov, E. Valkova, G. Kostadinova, G. Petkov, Ts. Yablanski, P. Valkova, D. Dermendjieva
Abstract. A survey and assessment of manganese (Mn) levels was carried out on the chain water – sediment – algae from 6 monitoring points, situated at three rivers and a dam with high anthropogenic impact in Stara Zagora region, South Bulgaria. International references of ISO and BSS for sampling and sample preparation of water, sediment and algae analysis were used. Manganese concentration in the collected samples was determined by atomic absorption spectrometry (AAS). It was found that despite the anthropogenic pressures on the studied waterbodies Mn content in water from all investigated waterbodies does not exceed the maximum permissible concentration, according to national Regulation No 7/1986. Mn accumulates in high levels in sediment and algae from all surveyed monitored waterbodies. The highest Mn concentrations in sediment were measured in Sazliyska River (714.5 mg/kg) and Bedechka River (799.6 mg/kg). With the highest levels of Mn were distinguished algae delivered by Yagoda Village (663.8 mg/kg), Jrebchevo Dam (476.0 mg/kg) and Sazliyka River (411, 5 mg/kg). The estimated ratios between Mn concentrations in sediment and water have shown that the accumulation of this metal in the sediment is from 1407 (Jrebchevo Dam) to 15466 (Tundzha River, Banya Village) times more than in the water. By the sediment/algae ratio it is found that Mn is accumulated from 0.5 (Jrebchevo Dam) to 2.4 times (Bedechka River) more in sediment compared to algae. The data from algae/water ratio show that Mn is accumulated from 1301 (Tundzha River at Jrebchevo Dam) to 19565 (Tundzha River at Banya Village) times more in the algae compared to the water. This fact suggests the mechanism of accumulation of Mn in the sediment and algae, probably different from simple diffusion. The obtained results indicate that sedimentand algae can serve as good indicators of pollution by Mn. They can also be used for purification of water from that metal.

Efficacy and selectivity of vegetation-applied herbicides and their mixtures with growth stimulator Amalgerol premium at oil-bearing sunflower grown by conventional, Clearfield and ExpressSun technologies

G. Delchev
Abstract. During the period 2010 – 2012, on the experimental field of the Field Crops Institute – Chirpan was carried out a field experiment with oil-bearing sunflower (Helianthus annuus). A total of 18 variants from the three technologies for oil-bearing sunflower growing were investigated – conventional (hybrid Arena), Clearfield (hybrid Alego) and ExpressSun (hybrid P64LE20). Vegetation-applied herbicides Goal, Raft and Pledge combined with the soil-applied herbicide Pelican provide good control of annual broadleaved weeds in conventional technology for sunflower growing. Combinations of herbicides Stomp, Wing with herbicide Pelican can be applied to mixed weeding from annual grassy and some broadleaved weeds, but with the absence of Xanthium strumarium, Cirsium arvense and Convolvulus arvensis. Herbicide combination Modown + Pelican should be used in secondary weeding primarily from annual broadleaved weeds, but with the absence of Xanthium strumarium. Herbicide tank mixtures Pulsar + Stomp by Clearfield technology and Express + Stratos ultra by ExpressSun technology completely destroyed all annual and perennial grassy and broadleaved weeds. Vegetation use of herbicides by conventional technology causes high phytotoxicity on sunflower. Phytotoxicity was the highest by herbicide Goal, followed by Pledge. Phytotoxicity is weaker by herbicides Stomp, Raft, Wing and Modown. Treatment of growth stimulator Amalgerol premium with herbicides Goal, Raft, Wing, Pledge and Modown as tank mixtures increases the selectivity of these herbicides.

Screening of plant protection products against downy mildew on cucumbers (Pseudoperonospora Cubensis (Berkeley & M. A. Curtis) Rostovzev) in cultivation facilities

S. Masheva, N. Velkov, N. Valchev, V. Yankova
Abstract. Screening of plant protection products (PPP) against downy mildew in cucumbers Pseudoperonospora cubensis (Berkeley & M. A. Curtis) Rostovzev was carried out during the period 2006-2011 in the “Maritsa” Vegetable Crops Research Institute, Plovdiv. Their toxicity to the imago of the bioagent Encarsia formosa Gah. were studied. High effectiveness (over 85.00 %) of the PPP with active ingredients: dimethomorph (Zampro SC, Acrobat paplus SC); symoxanil (Korsate Pro WG, Korsate R DF), strobilurins (Eclair 49 WG, Quadris 25 SC) was established. With the lowest effectiveness to the agent of downy mildew is Timorex 66 EC. All studied products are suitable for including in the systems for control of this disease. A non-toxic product to E. formosa is the botanical fungicide Timorex 66 EC, medium toxic products are those containing a.i. strobilurin and propamocarb-hydrochloride. The remaining PPP are slightly or medium toxic to the bioagent. Therefore E. fоrmosa could be applied parallel with slightly toxic fungicides against P. cubensis.

Stability of herbicides and herbicide tank-mixtures at winter oilseed canola by influence of different meteorological conditions

G. Delchev
Abstract. During the period 2010 – 2012, on the experimental field of the Field Crops Institute – Chirpan was carried out a field experiment with conventional Maximus hybrid PR44D06 (Brassica napus). A total of 15 variants were investigated. Canola hybrid from Maximus product line which is included in the study eliminates the need for growth regulators. The efficacy of the herbicide Salsa when used separately without the other partner herbicide is higher when treated with adjuvant Trend compared to adjuvants Codacide and Silvet. At tank mixtures of Salsa and Butizan, herbicide efficacy and crop long action against weeds are higher when they are introduced with adjuvant Codacide. When herbicide tank mixture Salsa + Pantera is treated with adjuvant Codacide synergism is accounted. At tank mixtures of Salsa + Agil, higher efficiency is accounted in its joint use with adjuvant Trend. Technologically the most valuable are tank mixtures of herbicides Salsa and Butizan with adjuvant Codacide, followed by these with adjuvant Trend. From the viewpoint of technology for growing winter oilseed canola, high rating also have tank mixtures of Salsa with antigrass herbicides Pantera and Agil, followed by that of Salsa with Runway. Combinations of Salsa with adjuvants Trend, Codacide and Silvet, but without a partner herbicide, have low rating because they are inefficient against grassy weeds and absence of soil action.

Study of the effect of soil trampling on the structural elements of yield and productivity of soybean

V. Sabev, S. Raykov, V. Arnaudov
Abstract. The study was conducted in the experimental field of the Institute of Forage Crops Pleven, Pavlikeni branch during the 2005–2007 period. The objective of the study was to determine the effect of soil trampling by the wheels of the tractor unit on the structural elements of yield and productivity of soybean. It was found that soil trampling by the tractor unit tires had a negative effect on the ramification number, being most pronounced after three and four passages. The trampling influenced negatively also the pod number and grain yield per plant, the results being statistically significant. The single and two-fold passage decreased productivity 13 to 24% and after three and four passages over the area the yield was reduced to 40% and the yield was lower at very good statistical significance.

Cultivation of Scenedesmus dimorphus strain for biofuel production

K. Velichkova, I. Sirakov, G. Georgiev
Abstract. Microalgae have several advantages, including higher photosynthetic efficiency as well as higher growth rates and higher biomass production compared to other energy crops. The Scenedesmus dimorphus strain was studied by using two media – BBM and 3N-BBM, and its potential for biofuel production was established. The temperature varied between 25 – 27ºC during the experiment. Fluorescent light was used to assure optimal light condition and a photoperiod of 15/9h light and dark cycle was maintained.The duration of the experiment was 25 days. Dry weight, optical density, chlorophyll, carotenoids and total lipids were measured for the biomass evaluation. The received results showed that the maximum vegetative growth was reached after approximately 16 days of incubation. The maximum growth rate during this period was 1.690 mg.l -1 dry weight in 3N-BBM medium, and in BBM medium – 0.960 mg.l -1. The lipid content which we received from the examined strain was 21.6% in BBM medium, and in 3N-BBM – 18.5%.

Metabolic and enzymatic profile of sheep fed on forage treated with the synthetic pyrethroid Supersect 10 EC

R. Ivanova
Abstract. Most of the small ruminant flocks on the Balkan Peninsula are bred on pasture. Thus the animals are endangered to graze treated alfalfa, without observing quarantine. The instability of the pyrethroid insecticides in rumen alkaline pH of the sheep is the reason for its absorption as early as in the upper part of the digestive tract and hence a better-expressed subtoxicosis appeared. Following the technological instruction given by the producer of the insecticide, the alfalfa field plots were treated with Supersect 10 EC. After seven days quarantine, the alfalfa was mowed, dried and added to the ration of the tested animals. After 20 days feeding of the animals, a decrease in the amount of the total lipids was established, without any changes of the blood glucose and total protein values. As regards the enzymatic profile of sheep fed on alfalfa treated with Supersect 10 EC, a significant increase of the activities of ASAT, LDH, MAO and ChE was reported. Based on the data obtained, we could conclude that when sheep was fed on alfalfa treated with Supersect 10 EC, a strong change in the enzymatic profile was observed. There were not significant changes in hepatocyte according to De Rites but the metabolic strain in the organism was suppressed as compared to that of the control animals

Food spectrum of grey mullet (Mugil cephalus L.) along the Bulgarian Black Sea coast

R. Bekova, G. Raikova-Petrova, D. Gerdzhikov, E. Petrova, V. Vachkova, D. Klisarova
Abstract. For the present paper 35 specimens of sea mullet (Mugil cephalus) from different age groups were investigated. The material was collected between May 2010 – September 2011 along the coast, the main points are two: Varna Bay and the mouth of the river Veleka. The main objective of the study was to establish the food spectrum of mullet, and thus a connection could be made between food components. The methods which were used and defined to study the food spectrum and the relationship between different food components are as follows: frequency of occurrence and dominance index of the nutritional components; the filling index and stomach emptiness index, as well as selectivity coefficient of a meal.Results showed that detritus, zoobenthos (Rissoa sp. and Trochammina inflate – 71.43%) and macrophytes (Cladophoraceae family – 63.64%) dominated in stomachs. Several potential toxic species were also found: Amphora coffeaeformis, Pseudo-nitzschia delicatissima, Pseudo-nitzschia seriata, Prorocentrum cordatum, E. pyriformis, P. minimum, Protoperidinium crassipes. The results for the frequency of occurrence (pF) showed that the most common in the stomach of a mullet of the macrophytes are the species of family Ulvaceae – 45.5% ; family Cladophoraceae – 45.5% ; of phytoplankton – Navicula spp (109,09%).; of zoobenthos: Nematoda g.sp. – 42.9% and Trochammina inflate – 28.6 %. The low emptiness index (0.0857) defines the grey mullet as an often eating fish. The small fish reaching up to 3–4 cm eat phytoplankton and zooplankton. Until now, research on the food spectrum of sea mullet by the Bulgarian sector of the Black Sea have not been conducted.