International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

A technology has been developed for the formation of a bed surface with a high arc-shaped bed, which has proven its advantages and has established itself in the production of vegetable, berry, essential oil, medicinal and decorative crops. A working tool has been developed for bed formation of a high arc-shaped bed with elevations for adjusting the parameters of the soil profile. An experimental model of a machine soil profiling combined, the machine operates simultaneously forming a bed surface, laying hoses for drip irrigation, on mulching film was made with a view to creating favorable conditions for crops.

To establish the influence of different irrigation and fertilization rates on the quality indicators of the fruit of three specific genotypes of tomatoes- Maldo, Pink Rock, and Hayet- in 2022, experiments were conducted in the experimental field of Maritza Vegetable Crop Research Institute – Plovdiv in an unheated steel and glass greenhouse type Venlo. The experiment was conducted under three irrigation regimes – optimal, reduced, and increased irrigation – 100%, 75%, and 125% using water-saving irrigation technologies and three fertilization regimes – optimal, reduced, and increased fertilization – 100%, 75%, and 150%.
It was found that reducing the water content resulted in a slight increase in dry matter, total soluble solids (TSS), and vitamin C content while varying the fertilizer rate did not significantly change the studied characteristics. Tomato fruit quality was more affected by irrigation than by fertilizer levels. Titratable acidity and pH differed between cultivars but not between treatments applied. The highest dry matter, TSS, and vitamin C contents were observed in the treatments with low irrigation rates and optimal fertilization (75%W and 100%F). Strong positive correlations were found between dry matter, TSS and vitamin C, while a strong negative correlation was found between fruit firmness and dry matter, TSS and vitamin C.
The factor Genotype had the strongest effect on the tomato fruit quality parameters studied, with a weaker but proven effect of the individual factors irrigation rate and fertilization rate on dry matter, soluble solids content, and vitamin C. The highest fruit quality was found in Pink Rock, followed by Maldo. The variety with the lowest values for most of the quality indicators is Hayet.

To establish the influence of irrigation and mineral regime on the growth index of tomatoes, the irrigation and fertilization schedules of three genotypes of tomatoes grown in an unheated steel and glass greenhouse in an experimental field of MVCRI – Plovdiv, Bulgaria, were examined. Environmentally friendly and water-saving irrigation techniques were used. Different irrigation rates were applied starting from full satisfaction of the crop water requirements to irrigation and with 25% reduction and 25% increase in irrigation rates and three fertilization rates respectively – optimum with 25% reduction and 50% increase.
After processing the results, the growth index showed an increase in the irrigation rate by 25% above the optimum growth in all three tomato cultivars included in the experiment. At the same time, no such relationship was observed when the fertilization rates were changed. The exception was the cultivar ‘Hayet,’ in which a decrease in fertilizer rate was also associated with a higher growth index, close to that of the optimum fertilizer regime. At the same time, the combination of increasing or decreasing the irrigation rate and fertilization did not have a positive effect on growth.

The risk of frost is a serious problem for crop production, especially in the spring season when crops are most vulnerable to sudden temperature changes. Autumn frost is a limiting factor for the yield and quality of the produced products. The frequency of frosts in years varies greatly for different agricultural areas according to their geographical location and altitude, topographic features, presence of water basins, typical movements or directions of air masses and depends on the type, condition and care of the specific agricultural crops. To view the danger of frost, the concepts of “first and last” frost have been used in practice, which denote the first and last drop in temperatures to or below 0 °C within the biological vegetation period of plants in the specific calendar year. The article reviews the global practice of providing databases on the risk of frost damage to agricultural crops.

The research was conducted to determine the irrigation regime of greenhouse tomatoes in 2022 on the MVCRI- Plovdiv experimental field in an unheated steel-glass greenhouse of the Venlo type. The experiment was carried out in three irrigation modes: optimal, reduced, and increased, respectively – 100%, 75%, and 125% using water-saving technology.
The size of the irrigation norms has been determined, i.e., the number of waterings for the growing season and their distribution by phases of development for soil and climatic conditions of the Plovdiv region.
The results obtained for irrigation of the greenhouse tomatoes show that 18 waterings were implemented for the growing season to maintain the soil humidity between 85-100% of the MFMC for the conditions of Plovdiv from the beginning of May to the end of July. The size of irrigation norms by modes varies from 14.9 to 24.7 mm, and irrigation from 268 to 447 mm. The maximum irrigation rates during the most significant water consumption period can be applied in 3-4 days and satisfy the needs of the plants. The obtained results are the basis for determining the design irrigation regime and predicting the culture’s irrigation time.

In order to determine the influence of different rates of irrigation and fertilization on the growth, yield, and some yield-related characteristics of three genotypes of tomatoes, research was carried out at IVCM – Plovdiv in an unheated steel-glass greenhouse of the “Venlo” type. The experiment was carried out with three modes of irrigation: optimal – 100%, reduced – 75%, and increased – 125%, using water-saving irrigation technologies and three modes of fertilization – optimal – 100%, reduced – 75%, and increased fertilization – 150%. The amount of watering and irrigation norms, the number of waterings for the growing season of greenhouse tomatoes were determined based on soil type, and climatic conditions in the region of Plovdiv. An optimal or high irrigation rate combined with reduced or optimal fertilization leads to maximum yields in all three tomato varieties. A specific reaction of the variety was observed – in “Hayet” and “Pink rock ”varieties, maximum yields (14.1 t/ha and 8.8 t/ha) were obtained in the variants with 100%/75%, while in the “Malduo” variety, the highest yield was obtained (8.6 t/ha) in the variant with 125%/100%, irrigation/fertilizer rate. In the three studied varieties of tomatoes, the lowest yield was reported when the irrigation rate was reduced by 25%, which shows that the reduction of the irrigation rate by 25% is within the limits of the critical, while the reduction of the fertilizer rate by 25% is permissible.

At the Institute of Soil Science, Agrotechnologies and Plant Protection – Sofia (IPAZR – Sofia) an experimental model of a machine for combined soil treatment in permanent plantations has been developed. The machine is designed to work using technology without turning the soil layer and at the same time at a sufficient depth for fruit plantations. Tests were conducted in laboratory and road conditions to verify the capabilities of the structure. Deficiencies have been identified, as a result of which the work must continue.

Rules for aggregating mounted agricultural machines have been systematized. Dependencies are derived for determining the parameters of the tractor after aggregation with the machine and the rules for safe work according to the norms are given.

This is a review of the groups of factors influencing the quality of the main and pre-sowing tillage of the soil for growing tomatoes – soil-climatic, technological.
The paper performs an analysis of the a priori information and from the conducted experimental researches the connection between the separate factors and the quality for performing the basic and pre-sowing treatment of the soil for growing tomatoes was established.

Irrigation plays a key role in growing vegetable crops. The efficiency of irrigation is expressed in obtaining optimal yields in terms of quantity and quality. The use of water resources should be water and energy saving in order to reduce the costs of vegetable production and to be environmentally friendly. The main criteria for assessing the effectiveness of irrigation are the total and additional net incomes. In order to meet the set requirements for irrigation, the best effect is obtained by applying drip irrigation. When growing tomatoes, the value of the irrigation system is redeemed in the first year for areas over 5 dka, for areas below 5 dka it takes 2 years. Drip irrigation of tomatoes has shown that the frequency and size of irrigation rates affect the weight, diameter and length of the fruit, their number and hardness.

In this work the possibilities of reducing the roughness and defects of surfaces obtained by 3D printing with selective laser melting (SLM), via reactive electrospark surface modification (ESD) with low-melting AlSi alloys has been shown. The influence of the energy parameters of the ESD process on the roughness, microstructure, microhardness and performance characteristics of the coatings has been studied. Surfaces with new phases and ultrafine crystal-amorphous structure with particle sizes from micro to nano level, with new relief, with thickness up to 15 μm and microhardness up to 11 GPa were obtained, as the initial SLM roughness from Ra = 8-11μm is reduced to Ra=3-5 μm. Possibilities for control of the characteristics of the coatings and purposeful synthesis of new phases by changing the parameters of the spark discharge have been established. The parameters of the ESD process, which provide simultaneous reduction of SLM surface roughness, removal and erasure of the defects and targeted reactive synthesis of new phases with high performance properties and wear resistance, are defined and optimized.

Mechanized harvesting of tomatoes should be carried out with minimal damage. This is achieved by knowing the processes. The movement of a tomato plant in the period of transition between conveying devices has been studied. Dependencies determining the length of free movement and the rates of fall on the fruit separator are derived, which are essential for determining the kinematic regime and preventing damage to the fruit.