Length-weight relationship of European catfish (Silurus glanis L.) fry reared at different stocking densities under controlled conditions

V. Krasteva*, M. Yankova

Institute of Fisheries and Aquaculture, 4003 Plovdiv, Bulgaria

(Manuscript received 14 October 2020; accepted for publication 18 January 2021)

Abstract. The present paper investigates the body length and weight, and the size-weight variations of one-month-old European catfish reared at 4 variants of stocking density: Variant 1 – 5 spec/l; Variant 2 – 10 spec/l; Variant 3 – 15 spec/l and Variant 4 – 28 spec/l. The experiment is carried out at the Institute of Fisheries and Aquaculture, Plovdiv for a period of 16 days, using a production system consisting of tubs with continuous water flow (0.7 l/min). At the end of the experiment, the fish from each variant are sorted in three size-weight groups: A – large, B – medium and C – small. The number of fish in each group is established. From the group of the medium- and small-sized fish, 150 speciments are measured, while from the group of the large specimens, which are the smallest in number, all specimens are measured for the biometric parameters body weight (BW, g) and total body length (TL, cm). The results from the study show small variations in the length and weight of the fish reared at the lowest stocking density (Variant 1). As the density increase, the size-weight differences between the specimens from Group A also increased, while of those from Group B they decrease. The number of the medium-sized fish decrease (p≤0.001) while the number of large specimens (p≤0.01) and small fish increase (p≤0.001).

Some physical properties of lentil seeds affected by harvest time

S. Gürsoy*

Department of Agricultural Machinery and Technologies Engineering, Faculty of Agriculture, Dicle University, 21280-Diyarbakır, Turkey

(Manuscript received 29 April 2020; accepted for publication 10 July 2020)

Abstract: The physical properties and the hardness of lentil seeds, which can also be affected by harvest times, are very important variables in the designing and adjustment of machineries used during harvest, handling and other processes. The objective of this study is to determine the effects of different harvest times on some physical and mechanical properties of lentil seeds. A field experiment was conducted at six harvest times including the harvesting at physiological maturity (H1) and 5, 10, 15, 20 and 25 days after physiological maturity (H2, H3, H4, H5 and H6, respectively). The variables determined were moisture content, diameter, thickness, sphericity, seed mass, bulk density, true density, porosity and hardness of lentil seeds. It was found that seed moisture content, seed dimensions, seed mass and bulk density decreased with delayed harvest time. However, sphericity, true density, porosity and hardness of lentil seeds increased with increased harvest time.

Productivity and grass density of the main types of pastures in Sakar and Strandja region

V. Vateva*
Department of Engineering and Technologies, Faculty of Technics and Technologies, Trakia University, 6000 Stara Zagora, Bulgaria
Abstract. Grassland associations are natural resource, which in their proper use might affect the welfare and economic development of the region in which they are located. In Sakar and Strandja regions such herbaceous plant associations occupy about 107.3 thousand hectares. Only in those regions of the country there is a favorable combination of environmental and climatic conditions allowing almost all year round utilization of pasture grass associations. They are the main potential to supply feed for the animals. In this experiment, the goal is to tracce and identify the productivity of natural pasture grass associations in Sakar and Strandja mountain. Observations were performed on the most typical, the most common and most used pastures located in these regions. The density of the pasture types was established. A comparative analysis of productivity of fresh mass and dry pasture grass of Sakar and Strandja region was performed. The results show that the pasture types in Strandja region possess higher density and greater productivity than those in Sakar region. With the highest density in Sakar region are the grassland type Agrostis capillaris – Festuca fallax, with a density of up to 1972 pieces/m2 at least. In Strandja region pasture type Agrostis capillaris – Cynosurus cristatus – Lolium perenne reaches density 3716 pieces/m2. These types of pastures are distinguished with the highest productivity of fresh and dry biomass. In Sakar region from pastures of type Agrostis capillaris – Festuca fallax 16680 kg/ha green mass and 4920 kg /ha dry matter can be obtained, and in Strandja region from grassland of type Agrostis capillaris – Cynosurus cristatus – Lolium perenne, 31700 kg/ha fresh mass and 7380 kg/ha dry matter can be obtained.

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Species composition of weeds in wheat and barley

M. Georgiev, D. Pavlov, G. Beev, M. Gerdzikova, R. Bazitov

Abstract. During the period 2008-2009 investigation was performed to determine the species composition and density of weeds in the main cereals (wheat and barley). The aim of study was to establish the weed species diversity and the background of weed infestation in wheat and barley in the region. The number of weeds in wheat and barley was established in three regions west, east and south from Stara Zagora by itinerary method in 10 points for each region. Weed infestation and domination of weed species was established by Statistica for Windows. In the eastern region of Stara Zagora (the land of Dalboky) the most propagate weed was Veronica hederifolia L. – 37,2 and Convolvulus arvensis L. – 10,3 plants per m2. In the western area of the municipality (the land of Bogomilovo) prevail mainly Avena fatua L. – 16,4; Veronica hederifolia L. – 12,8 and Galium aparine L. – 6,6 plants of m2. In the southern region (the land of Malko Kadievo) winter cereals have higher weed infestation compared to the other 2 regions. The most propagated weeds in this region were Chenopodium album L. – 36,2; Convolvulus arvensis L. – 7,3 plants per m2 etc. The type of weed infestation of wheat and barley in the investigated areas was as a whole the typical for these crops.

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