Optimizing the thickness of a straw outer wall of a building for sows in a view to achieving cost-effective heat insulation

V. Dimova*, D. Georgiev

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 22 November 2020; accepted for publication 16 April 2021)

Abstract. The aim of the study is to determine the optimum thickness of the surrounding wall structure of a building for nursing sows by using heat insulation from straw and different fuel (pellets and dry wood) for heating the building. To achieve the purpose, 6 models of walls made of environmentally friendly panels with wooden skeleton, thermal insulation from pressed straw bales and double-sided clay plaster have been developed, such that the accepted thickness of the thermal insulation layer is respectively: 20, 25, 30, 35, 40 and 45 cm. The construction value of the finished wall is determined by adding the value of the construction and assembly works on the construction site to the value of the preparation of the panels (in a workshop), including the payment of labor, materials and additional costs for the implementation of clay plaster and waterproofing membrane. The annual energy losses through 1 m2 of the enclosing wall and the annual heat insulation costs (as a sum of annual energy cost and the depreciation deductions) are determined through the described methodology and verification of condensation of water vapor on the inner surface of the wall was carried out. The results of the research show that by using pellets for fuel, the optimal thickness of the thermal insulation is 45 cm, and by using dry wood it is 35, 40 and 45 cm. All studied models of enclosing straw wall meet the hygienic requirements for preventing condensation on their inner surfaces.

Effect of transport vehicles on the grain harvester idle time during harvesting

G. Tihanov*

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 12 December 2020; accepted for publication 2 April 2021)

Abstract. The article studied the effect of transport vehicles on the grain harvester idle time during wheat, barley and rapeseed harvesting in 6 agricultural farms. In each of the farms one grain harvester and the established harvesting organization were studied without changing the unloading mode and the specific activities performed by the harvester operators and transportation vehicles. By multifactor regression analysis the effect of time for moving the transport vehicle on the grain harvester idle time was established. In addition, the value of the determination coefficient R2=0.54 reveals that 54% of the harvester idle time for unloading the grain hopper (Т1) change is due to the change of significant times and 46% to the effect of unmanageable factors. It has been established that the change in the time from opening the unloading auger to its activation depends on the position of transport vehicles on the field (t1) and the time for their movement to the harvester auger (t2). The results obtained can be used to minimize costs in the technological process of crop harvesting.

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).

Productivity and quality of experimental sunflower hybrids in climatically different years

M. Drumeva*

Department of Plant Production, Faculty of Manufacturing Engineering and Technologies, Technical University of Varna, 1 Studentska str., 9010 Varna, Bulgaria

(Manuscript received 5 September 2020; accepted for publication 16 January 2021)

Abstract. The main purpose of sunflower breeding requires the developing of high-yielding hybrid varieties with broad ecological plasticity that would guarantee the stability of the yield and the quality of the production from them. This investigation involved 10 experimental F1 hybrid combinations developed with the participation of double haploid fertility restorer lines (DHR) obtained through the method of gamma-induced parthenogenesis in combination with embryo culture. The aim of the investigation was to study the productivity and quality of the seeds from the new experimental sunflower hybrid varieties with a view of their future use in practice. The experimental work included years 2014 and 2015, which were significantly different with regard to the climatic conditions. The experiments were carried out in the experimental field and the laboratory of the Technical University in Varna. The hybrid combinations were assessed according to the main parameters of sunflower productivity, namely seed yield (kg/ha) and oil yield (kg/ha), as well as according to the main quality parameter of sunflower seeds – oil percent in seed. Under the conditions of this investigation, the analysis of the results showed that the genotype potential of the hybrids was determining for the seed and oil yield; a relatively high effect of the year conditions was also established for the parameter oil yield. The percent of oil in seeds was determined on the basis of the genotype, and the effect of the year was considerably lower. Summing up the results from the testing of the experimental hybrids, it can be pointed out that three of the studied hybrid combinations (3607A х 112DHR, 3607A х 123DHR and 3607A х 167DHR) realized good production potential under variable agro-meteorological conditions and can find future realization in practice.

Fuel consumption of a machine-tractor unit in direct sowing of wheat

G. Tihanov1*, N. Ivanov2

1Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Plant production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 7 September 2020; accepted for publication 8 January 2020)

Abstract. A study has been conducted on the fuel consumption in direct sowing of wheat with a Horsch Avatar 6.16 SD direct seeder aggregated to a John Deere 7250 R tractor. The experimental field (29.53 ha) was sown with winter soft wheat (Silverio variety) at a sowing rate of 195 kg/ha. The data from the sowing unit were collected using the JD Link telematics system, downloaded from the system and imported and compiled in a database. Fuel consumption was analyzed in accordance with the operation mode, the idle mode and the transportion mode of the machine-tractor unit. It was found that the average fuel consumption in work mode (when the seeder was sowing) was 23.08 l/h, while in transportion mode the seeding unit consumed 16.55 l/h and while the unit was idling it consumed 4.30 l/h. The results also show that the seeding unit has travelled 63 km and consumed 185 L of diesel fuel at an average diesel consumption of 23.08 l/h.

Evapotranspiration in Sudan grass second culture grown under non – irrigated and optimal irrigated conditions

R. Bazitov*

Agricultural institute, 6000 Stara Zagora, Bulgaria

(Manuscript received 24 August 2020; accepted for publication 19 October 2020)

Abstract: The aim of the present study was to establish the evapotranspiration of Sudan grass variety Engje-1, grown as a second crop for silage on meadow-cinnamon soil for the region of Southern Bulgaria under irrigation conditions and without irrigation. For this purpose, an experiment with Sudan variety Endje-1 was conducted in the experimental field of the Agricultural Institute – Stara Zagora on soil type meadow-cinnamon soil, after its predecessor barley. The Sudan grass is harvested in the brooming stage. Two variants were explored: Variant 1 – without irrigation (control) and Variant 2 – with optimal irrigation, 70-75% of field capacity (FC). Evapotranspiration of Sudan grass grown as a second crop under non-irrigated conditions, depending on the nature of the year, ranges from 168.7 mm to 183.7 mm. Under conditions of irrigation, the largest share in the formation of the water consumption is occupied by the irrigation norm – 87.1% on average (from 86.3 to 90.8%). Under irrigated conditions, the relative participation of the initial water reserve in the formation of evapotranspiration significantly decreases.

Operational characteristics of direct sowing machine-tractor unit

G. Tihanov*

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 13 July 2020; accepted for publication 26 October 2020)

Abstract. A study on some operational characteristics of a direct sowing machine-tractor unit has been carried out in wheat sowing. It is performed by Horsch Avatar 6.16 SD direct seeder aggregated to John Deere 7250 R tractor. It was found that 91% of the area is sown at sowing rate of 195 kg seed/ha. The remaining 9% are sown either at lower or higher rate. Engine rotations of the seed unit have been established at work mode, i.e. when the seeder is sowing, these are 1594.81 min-1, in idle state the rotations are 912.08 min-1, and in transportation mode are 1860.36 min-1. The relative share of engine use has also been determined: when the seeder is sowing, it is 56.68%, when the seeder unit is in idle mode, it is 14.54% and when the unit is in transportation mode – 28.78%, respectively. The actual operation speed of the seeder unit when sowing wheat was 10.40 km/h and the real hourly productivity – 3.7 ha/h.

Growth and yield of orange (Washington Navel 141) grafted on different citrus rootstocks

Alaa Suhiel Ibrahim*

Research station of Ciano, Jableh, the agricultural scientific research center in Lattakia, General corps of scientific agricultural researches, Syria

(Manuscript received 26 May 2020; accepted for publication 27 July 2020)

Abstract. This investigation was conducted during 2014, 2015 and 2016 in the field of the citrus experimental station in Ciano, the general corps of scientific agricultural researches. The growth and yield of orange trees (Washington navel 141) budded on seven citrus rootstocks (Sour orange, Troyer citrange, Carrizo citrange, Citrumelo 4475, Citrumelo 1452, Macrophylla and Cleopatra mandarin) and farmed since 1989 have been studied. The results for the average of yield showed that the trees grafted on Cleopatra mandarin (58.33 kg. tree-1) were significantly superior to those grafted on Macrophylla (34.17 kg. tree-1). Orange trees grafted on Citrumelo 4475 and Citrumelo 1452 were significantly superior to other treatments in trunk section area of the rootstock (922.41 and 841.02 cm2, respectively). The greatest fruit fresh weight was in trees grafted on Citrumelo 4475 (284.85 g. fruit-1) which were significantly superior to those grafted on Carrizo and Troyer citrange (232.49 and 236.06 g. fruit-1, respectively). The biggest total soluble solids (%) was in trees grafted on Carrizo and Troyer citrange (12.83% for both treatments) which were significantly superior to those grafted on Sour orangе and Macrophylla (11.5% for both treatments), while the greatest total acids (%) was by Sour orange (2.08%) without significant differences.

Spectral analysis as an extra method to soil type discrimination

M. Todorova1*, S. Atanassova2, M. Georgiev1, L. Pleshkuza1

1Department of Crop production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria,
2Department of Biochemistry, Microbiology and Physics, Faculty of Agriculture, Trakia University,
6000 Stara Zagora, Bulgaria

(Manuscript received 18 February 2020; accepted for publication 25 April 2020)

Abstract. The purpose of the study was to test near infrared soil spectra as an extra method for three soil types (Fluvisols, Vertisols and Solonchaks) discrimination from different regions of South Bulgaria. The diffuse reflectance spectra of 177 soil samples (from the 0-20cm layers): 50 samples of Fluvisols soil type, 78 samples of Vertisols soil type and 48 samples of Solonchaks soil type were obtained using a Spectrum NIRQuest (OceanOptics, Inc.) working within the range from 900 to 1700 nm. Soft independent modelling of class analogy (SIMCA) was performed to classify samples according to their taxonomic classes. The results obtained showed that the soil samples are separated accurately according to their soil type based on their spectral information. All this could be used in the future studies related to the application of the NIRS method as a qualitative or quantitative method for soil analysis and also for the purposes of precision farming.

Еconomic analysis of meat production from two types of Domestic quails

H. Lukanov1*, I. Pavlova2

1Department of Animal Science – monogastric and other animals, Faculty of Agriculture, Trakia University,

6000 Stara Zagora, Bulgaria

2Department of General livestock breeding, Faculty of Veterinary medicine, Trakia University,

6000 Stara Zagora, Bulgaria

(Manuscript received 3 March 2019; accepted for publication 17 April 2020)

Abstract. There are two types of Japanese quails, reared in Europe – dual-purpose and meat. The aim of the present study was to made an economic analysis of fattening quails from the dual-purpose and heavy production types. Three groups were formed – group 1 (dual-purpose), groups 2 and 3 (heavy type), reared in cages. After quails sexing on the 16th day of age, there were formed six subgroups: 1m, 1f, 2m, 2f, 3m and 3f. Fattening period lasted until 35 days of age. For revenues calculation produced meat and edible offal data per m2, were used. Costs calculation include consumed feed for the period, day-old quail, and other costs. The main production costs were associated with feed and day-old quails: from 80.3 and 82.6% of all costs in the studied groups. The anticipated revenues from produce in group 2 were 10 EUR/m2 higher than those in group 1, and for group 3 – 10.21 EUR/m2 higher than group А. The results indicate that meat type quails fattening is the most economically efficient in quail meat production. Producing quail edible offal is still not developed but could be beneficial for efficiency of quail fattening small farms.