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

A study was conducted to determine the irrigation regime and its impact on the yield of three genotypes of greenhouse tomatoes in 2022 at the experimental field of MVCRI – Plovdiv in an unheated steel-glass greenhouse of the Venlo type. The experiment was conducted in three irrigation regimes:
Optimal 100%M, reduced by 25% and increased by 25%, using water-saving technology.
The size of the irrigation norms, the number of irrigations for the growing season and their distribution by development phases for the soil and climatic conditions of the Plovdiv region were determined.
The obtained results for irrigation of greenhouse tomatoes show that 18 irrigations were implemented during the growing season in order to maintain soil moisture between 85-100% of the maximum field moisture capacity for the conditions of Plovdiv from the beginning of May to the end of July.
The size of the irrigation rates by regimes varies from 14.9 to 24.7 mm, and the irrigation rates – from 268 to 447 mm. The maximum irrigation rates during the period with the most significant water consumption can be applied after 3-4 days and satisfy the needs of the plants. The analyzed results of the yields obtained from the three tomato genotypes at different irrigation rates show that the highest total yield of greenhouse tomatoes is formed in the variant with 125% implementation of the irrigation rate, followed by the variant with 100% irrigation rate, and the lowest, in the variant with 25% reduction in the irrigation rate.
Obtaining a good effect from irrigation and the most productive use of irrigation water is possible only when applying an optimal irrigation regime, consistent with the requirements of the crops grown.
A number of studies have been conducted in our country on the limiting factor – water. Their main goal is to establish the best efficiency of applying different irrigation regimes for irrigation under optimal and insufficient water supply. (Kireva et al 2020)
The best results in terms of water use in this crop are obtained when the soil moisture is above 85% of the WHC and is applied to water-saving irrigation techniques. This method fully meets the requirements for sustainable agriculture and ecological fruit production, including ensuring high yields and quality of production, reducing unwanted side effects. (Bucks et al.,1982; Kireva ,2020.)
The results obtained by (Mukherjee, S., et al. 2023) show that physiological characteristics, yield and water productivity are significantly influenced by the irrigation system and soil moisture regime, with drip irrigation improving the average yield of tomatoes by 25%.
It was found that reducing the optimal rate (100% M) with a water stress of 50% (50%M), a significant decrease in yield (13.16%) was observed in greenhouse tomatoes (Wu et al. 2022 ; Lu et al. 2019 ). Alternatively, Wu et al. ( 2022 ) stated that under optimal irrigation conditions, tomato plants produced more fruits than those grown under deficit irrigation.
With the studies of the mutual influence of different irrigation regimes on the yield of tomatoes grown in a polyethylene unheated greenhouse, it was found that the impact of irrigation on yield has a greater effect at higher levels of irrigation rate, (Stoyanova A. et al.,2020; Stoyanova A. et al. 2019).
Studies of the irrigation regime and its influence on the yields of tomatoes grown in plastic greenhouses using drip irrigation are quite scarce, and the studies carried out in our country are for the conditions of the Sofia Field (Aboamera M. 1992; Kireva,; Kireva R.,2020) and for St. Zagora (Stoyanova An. et al. , 2020), which cannot be indicative of other agro-climatic regions of the country, which are characterized by different soil and meteorological conditions. Given the above, it is evident that research is needed to establish the complex influence of the irrigation regime on the quantity and quality of the yield of tomatoes grown in glass unheated greenhouses for the soil and climatic conditions of a region with developed vegetable production, such as Plovdiv. This will be achieved by using principal component analysis to assess the effects of tomato quality and the efficiency of water use and fertilization.
Study objective – determining the irrigation regime and its influence on the yields of greenhouse tomatoes for the region of the city of Plovdiv

In order to establish the irrigation regime of short-fruited cucumbers in open areas in the soil-meteorological conditions of the area of the village of Chelopechene – Sofia, researches were carried out in drip irrigation of cucumbers variety “Levina”, testing different regimes – from full satisfaction of daily needs the culture from water to irrigation with reduction by 30% of the irrigation norm. A variant with a 30% increase in the irrigation rate was also tested.
The obtained results show that the cultivation of short-fruited cucumbers for fresh consumption in open areas requires 15 waterings with an average irrigation rate of 18.3 mm, which is realized at different intervals depending on plant development and the stress of metrological factors and irrigation rate 280 mm.
The realized irrigation regimes have influenced the formation of yields of short-fruited cucumbers. The yields during the three years of the experiment varied from 2368 to 5404 kg / dka, with the highest yields being obtained in the first and second years. Yields in the third year were lower by 30% as a result of adverse weather conditions, which led to a shortening of the growing season of the crop.

In order to determine the productivity and the effect of irrigation on apples grown under soil and meteorological conditions in the area of the village of Chelopechene – Sofia, research was conducted on drip irrigation of a plantation of the “Florina” variety, and different regimes were tested – from complete satisfaction of the daily needs of water to irrigate the culture with irrigation rates reduced by 20% and 40%. A non-irrigation variant has also been tested.
The productivity of the irrigation rate at optimal irrigation varies by years from 16.3 to 28.0 kg.ha-1.mm-1, and at 40% reduction of the irrigation rate from 19.3 to 26.0 kg.ha-1. mm-1
The highest values of productivity of the irrigation rate are reached at irrigation with a 40% reduction of the irrigation rate, in the dry 2004 high values were obtained and at the variant irrigated with 100% irrigation rate 28,0 kg.ha-1.mm-1
The optimization of moisture in the active soil layer contributes to a significant increase and stabilization of yields, which for the test conditions are from 1266 to 2087 kg / dka. Additional yields ranged from 542 to 821 kg / dka, averaging over the study period.

An analysis has been made of the research work to determine the impact of water deficit on the quantity and quality of sunflower production. Studies have also taken into account the more frequent drought in the last decade – soil and atmospheric. Research shows that its good drought resilience allows it to be grown under irrigation conditions, but is sensitive to severe droughts, especially in the critical stages of development which leads to poor quality and drastic decrease in yield, and in some years to the lack of yields. The results show that sunflower irrigation has a large reserve for obtaining additional yield, which has been established through experiments in different parts of the country. The increase in irrigation is about 30-40%, and critical for water stress is the period of 20 days before and 20 days after flowering.

In order to determine the productivity and the effect of irrigation on apples grown under soil and meteorological conditions in the area of the village of Chelopechene – Sofia, research was conducted on drip irrigation of a plantation of the “Florina” variety, and different regimes were tested – from complete satisfaction of the daily needs of water to irrigate the culture with irrigation rates reduced by 20% and 40%. A non-irrigation variant has also been tested.
The productivity of the irrigation rate at optimal irrigation varies by years from 16.3 to 28.0 kg.ha-1.mm-1, and at 40% reduction of the irrigation rate from 19.3 to 26.0 kg.ha-1. mm-1
The highest values of productivity of the irrigation rate are reached at irrigation with a 40% reduction of the irrigation rate, in the dry 2004 high values were obtained and at the variant irrigated with 100% irrigation rate 28,0 kg.ha-1.mm-1
The optimization of moisture in the active soil layer contributes to a significant increase and stabilization of yields, which for the test conditions are from 1266 to 2087 kg / dka. Additional yields ranged from 542 to 821 kg / dka, averaging over the study period.

An analysis has been made of the research work to determine the impact of water deficit on the quantity and quality of sunflower production. Studies have also taken into account the more frequent drought in the last decade – soil and atmospheric. Research shows that its good drought resilience allows it to be grown under irrigation conditions, but is sensitive to severe droughts, especially in the critical stages of development which leads to poor quality and drastic decrease in yield, and in some years to the lack of yields. The results show that sunflower irrigation has a large reserve for obtaining additional yield, which has been established through experiments in different parts of the country. The increase in irrigation is about 30-40%, and critical for water stress is the period of 20 days before and 20 days after flowering.

Drought is a major problem for plant breeding in the country during dry years. This, in parallel with the increase in the technical capabilities of agriculture, has put more emphasis on overcoming the drought phenomenon. For this purpose, efforts have been made both in the development of relevant technical concepts and in the development of appropriate methodologies and technologies. The most important activity in this direction is the redistribution of water resources mostly over time. The report presents some aspects of overcoming the effects of drought by optimizing the use of water resources.

The production of green beans in plastic unheated greenhouses is relevant when grown as a intercropping culture. Rrotation of crops is an important biological factor for increasing soil fertility, and year round production of vegetables in plastic greenhouses to maximize the economic impact of these expensive facilities.
Considering the biology of the crop and especially its requirements for soil moisture, determinating for obtaining high yields and quality production is the implementation of a proper irrigation regime, as well as the use of suitable irrigation technique.
The aim of the research is to identify the main elements of the irrigation regime of green beans, cultivated as a second intercropping culture, in drip irrigation / watering and irrigation rates, interwatering periods and number of irrigations /.
Irrigation was carried out with a drip irrigation system type Drossbach. Variations have been tested at 85-90% of pre-watering humidity and 120% of irrigation rates- 120%; 100%; 80% and 60%.
It has been found that the productivity of irrigation water in drip irrigation of vegetable crops grown in unheated greenhouses is increased by reducing the irrigation rate. The highest productivity of irrigation water is achieved with the 60% irrigation rate option.

Berry cultures – strawberries, raspberries, blackberries, blackcurrants, etc. are of great economic importance due to growing demand and high productivity. In general, they are susceptible to droughts and are so demanding for soil moisture, and their growth and yield depend to a large extent on the presence of sufficient soil moisture.
In order to establish the irrigation regime of raspberriesin drip irrigation conditions, field experiments were conducted on the experimental field Chelopechene-Sofia. Irrigation was carried out with a pre-irrigation humidity less than 85% of WHC and variants watered with irrigation rate reduction of 20%, 40% compared to the variant irrigated at 100% of WHC and non-irrigated variant.
Realized irrigation regimes in individual years have had an impact on the yields obtained, with the highest yields being obtained for the irrigated variants with 100% irrigation rate and the lowest in non-irrigated variants. The highest increase in yield was obtained in 2004 (dry), which is with 67% more compared to non-irrigated variants, and the smallest increase of 33% was obtained in the humid 2005.
The analysis of meteorological factors shows that the rainfall in the country is insufficient to satisfy the requirements of plants of soil moisture, and the temperature sums over ten-days periods over the whole vegetation period considerably exceed the respective norms. This requires the use of drip irrigation for the successful production of raspberries under conditions of water deficiency and relatively high temperatures.