Growing of cabbage in water efficient irrigation methods in Uzbekistan

. In world agriculture, efforts are being made to reduce water consumption in crop irrigation, to study the level of soil moisture and water consumption in different irrigation methods, to improve the agrophysical, agrochemical and microbiological properties of the soil, and to increase its productivity. Also, large-scale scientific research is being carried out on increasing the yield of vegetable crops in different irrigation methods and reducing the phytosanitary condition of the field (density of weeds and pests, level of disease). The development, improvement and widespread implementation of optimal and cost-effective irrigation methods for planting and caring for vegetable crops in the spring and summer periods in the conditions of water scarcity is one of the urgent issues in agriculture. The development of water saving irrigation technologies in conditions of Uzbekistan does not influence essentially on agro-application physical properties of typical grey soils. At application of water saving irrigation in conditions of a climate of Uzbekistan, it was noticed that the most effective way is drip irrigation. At this way of irrigation, water is saved by 50% and productivity of vegetable crops and fertility of soil increases by 10-15%.


Introduction
In the world today, ensuring food security is one of the main tasks of developed countries. Today, the demand for vegetable and potato products is increasing dramatically in order to ensure food security around the world [1]. If we analyze the data of the last years, 182.3 million tons of tomatoes, 71.45 million tons of cabbage, 36.1 million tons of sweet and hot peppers, 42.83 million tons of carrots and 388, 19 million tons of gross crops are grown [2]. According to the information of the international organization FAO, 30-33% of cultivated areas have been degraded due to improper irrigation of agricultural crops, as a result, production is reduced by 15-20% [3].
In particular, proper use of water resources, provision of water to the population and agriculture is one of the urgent problems [4]. Plants can use only 30-35% of the amount of water given to 1 hectare of land for development and harvesting. The remaining 30-35% of the water evaporates from the body and the surface of the earth, and another 30-35% of the water is added to the groundwater [5].
In developed countries, Japan, the USA, Europe, Israel and other countries, watersaving irrigation methods are widely used and high yields are obtained. Drip irrigation is used for 80-90% of irrigated areas. The tragedy of Aral Sea became a lesson for the whole world due to the unwise use of land and water resources [6].
All over the world, a wide range of measures are being implemented for the effective use and protection of water and land resources [7]. In this regard, creating an optimum level of water, heat, air and nutrition in the soil prevents salinization and re-salinization, and the use of agro-ameliorative measures against erosion, the development and wide implementation of water-saving innovative technologies of irrigation of vegetable and potato crops during spring and summer maintenance, and widespread implementation. is one of the tasks [8]. It ensures a high and quality harvest from crops and increases soil fertility.
Today, the cost of building a drip irrigation system in Uzbekistan was reduced by 3-5 times compared to 2000. 95% of the necessary components for building a drip irrigation system are produced in Uzbekistan, and more than 10 companies and farms produce the necessary components for the construction of a drip irrigation system. In order to achieve the solution of the set tasks, many scientific and research works are being carried out, and the main goal of these works is to apply foreign water-saving progressive technologies in accordance with the soil and climate conditions of Uzbekistan [6][7][8][9][10]. In addition, the evaluation of the agro-economic and environmental efficiency of water-saving technologies, the development of scientifically based recommendations, the creation of demonstration areas showing the advantages of new water-saving technologies for farmers, the holding of seminars and trainings, the acceleration and expansion of the application to production are being focused on nowadays.

Materials and methods
The purpose of the research is to apply 40 tons of organic fertilizers per hectare in the conditions of irrigated typical gray soils of the Tashkent region (Uzbekistan), in the maintenance of cabbage, bell pepper, tomato and potato crops from spring to autumn. It also consists in improving water-efficient irrigation methods that allow saving water and land resources and improve the phytosanitary condition of cultivated fields.
Observations, analysis and measurements were carried out in the research "Methods of conducting field experiments", Dospekhov's methods of multifactor dispersion analysis were used [1,2]. Statistical analysis of experimental data was carried out in "Excel 2019" and "Statistica 7.0 for Windows" computer programs, as well as mathematical analysis. The research was carried out in 2020-2022 at the Scientific Research and Training Experimental Station of Tashkent State Agrarian University, Uzbekistan.

Results and discussion
Among the cost-effective irrigation methods, the role of drip irrigation in restoring, maintaining and increasing soil fertility is extremely large. It has a positive effect on the agrophysical and agrochemical properties of the soil. According to the results of agrophysical analysis, the amount of aggregates larger than 0.25 mm in the 0-20 cm layer in the control variant was 18.5%. The amount of macroaggregates increased by 20.3% in the subsurface irrigation method or 1.8% compared to the control. Microaggregates < 0.25 mm, the amount of large aggregates 0-20 cm was 81.5% in the control variant. The amount of microaggregates increased by 82.3% or 0.8% in the 20 cm layer by drip irrigation method.
The amount of 1-025 mm macroaggregates was 64.5% in the control variant. An increase of 67.9% or 3.4% was observed in the drip irrigation method compared to the control.
The influence of the irrigation method on soil aggregates during the growing season was studied in the experimental field where "Dar Tashkenta" variety bellpepper was planted. The structural coefficient was equal to 1.81 in the control variant. In drip irrigation, it was 2.11 (Table 1). Table 1. Change of the soil aggregates of the experimental area planted with "Iyunsky" variety of cabbage depending on the irrigation method (2020-2022).
It was noted that grain size was slightly higher in rainfed and subsurface irrigation methods compared to the control option. When sprinkler irrigation was used, the average granularity of the soil in the 0-30 cm layer was 49.3% and the granularity in the 0-60 cm layer was 49.0%, while it was around 50.5% and 51.1% in the surface irrigation method, respectively. In the 0-60 cm layer by drip irrigation, the volume mass was 1.34 g/cm 3 and the granularity was 50.2%. Compared to the control variant, bulk density was found to be 0.06 g/cm 3 and grain size was 1.5% higher. The highest granularity was returned in drip and subsurface irrigation methods (Table 2). The results of agrochemical analysis in the 0-30 cm layer of the soil showed that the amount of nitrate nitrogen at the beginning of the flowering period (Table 3) was 24.6 mg/kg in the method of overhead irrigation and 27.5 mg/kg in the method of underground irrigation. At the end of the irrigation period, it was noted that in the control option, it was 11.0 mg/kg in the 0-30 cm soil layer, 15.3 mg/kg in rain irrigation, and 12.4 mg/kg in drip irrigation. Nitrate nitrogen depletion at the end of the growing season has also been reported in other irrigation methods. The plant cannot absorb mineral fertilizers well due to the frequent formation of mud and soil moisture in the method of sprinkler irrigation. Therefore, it was observed that the growth of vegetables was very slow. It was 12.4-15.3 mg/kg at the end of the irrigation period in drip and subsurface irrigation. It was determined that the amount of ammonia nitrogen in the 0-30 cm control variant was 35 mg/kg at the beginning of the application period and 22 mg/kg at the end of the irrigation period. This indicates that plants absorb ammonia nitrogen during growth. Ammonia nitrogen does not accumulate in the soil and plant composition. Ammonia nitrogen was 36-38 mg/kg at the beginning of the growing period and 20-28 mg/kg at the end of the growing period. This is the highest indicator, mineral fertilizers are evenly distributed in the 0-30 cm layer in the underground irrigation method, creating a favorable nutrition regime for plants. 40 kg/mg, and 18.0 kg/mg at the end of the growing period. Phosphorous fertilizer at the beginning of the growing season in rain, drip and underground irrigation methods, respectively (Table 3) 42; 45 and 47 mg/kg, at the end of the growing period it was 18, 26 and 32 mg/kg. It has been proven that the best method of feeding is drip and subsurface irrigation. In economical irrigation methods, mineral fertilizers are mainly applied in water along with irrigation, the annual amount is divided into 4 parts and given in 2-4-6-8 irrigations. The regime of feeding with mineral fertilizers was stopped 15-20 days before fruit ripening.
The use of water-soluble chemical preparations has also given good results in controlling pests, diseases and weeds in drip irrigation. Diseases and pests were reduced by 30-35 percent compared to the control option. Total costs are reduced by 30%.
When vegetable crops were irrigated in the same way, the seasonal irrigation rate was 3070 m 3 /ha in cabbage, 6206 m 3 /ha in evening cabbage and 11594 m 3 /ha in bell pepper. The most promising method for vegetable crops was drip irrigation, with seasonal irrigation rates of 1567, 3237 and 5924 m 3 /ha during the three-year study period. The saving of E3S Web of Conferences 389, 03053 (2023) https://doi.org/10.1051/e3sconf/202338903053 UESF-2023 irrigation water by season was 51.3% in carrot, 47.9% in cabbage and 48.9% in bell pepper. Irrigation methods had different effects on water conservation and crop planting period, respectively.
The most water saving in the carrot was recorded in the option using the drip irrigation method. In this experimental option, the total seasonal irrigation rate was 1567 m 3 /ha, and 51.3% of water was saved in the drip irrigation method compared to the control option -the furrow irrigation method (3070 m 3 /ha) ( Table 4). The next place in terms of water saving is occupied by options using rain and underground irrigation methods. It was found that the amount of water saved compared to the control was 40.8% and 69.0%, respectively.
Among the economical irrigation methods, the highest average yield was 45.4 tons/ha in the drip irrigation method, which was 7.8 tons/ha additional yield compared to the control option. 3.1 tons/ha additional yield was obtained compared to rain irrigation method (Table  5). This is because there is no soil erosion and the soil is fertilized with 40 tons of organic fertilizers every year. These conditions reduce weed seed germination, resulting in 70-80% reduction of annual weeds and 60-75% reduction of perennial weeds.
According to the results of biochemical investigations of the composition of cabbage, it was found that the amount of dry matter increased by 0.5-0.4% in drip irrigation methods compared to the control option ( Table 6). The total sugar content increased by 0.3-.04% and vitamin C content by 0.4-1.0 mg/%, resulting in improved product quality. An increase in soil graininess was observed in vegetable crop drip irrigation methods.  Cabbage cultivation using drip irrigation method was found to be effective and yield was 60%. It has a 24% yield compared to the irrigation method. It was 49% in rain irrigation method (Table 7).

Conclusions
In the conditions of the typical gray soils of the Tashkent region of Uzbekistan, which have been irrigated for a long time, during the growing season of vegetable crops (carrots, cabbage, tomatoes and bell pepper) and potatoes using economical irrigation methods, 50% of water is saved using drip irrigation methods, the yield is on average 3-15%, and the number of agronomic structures in the soil increased by 4-11%. The efficiency of mineral fertilizers has increased as a result of simultaneous and uniform application of mineral fertilizers with water. As a result, cultivated crops were harvested 10-15 days earlier, the amount of organic elements in the fruit increased and the quality of the crop improved. In order to grow high-quality crops, save water resources, and reduce the spread of weeds, diseases, and pests, soil moisture before irrigation should be in the order of 65-70-75% compared to the limited field moisture capacity, with an average irrigation rate of 290.6 m 3 /ha, and should be irrigated 9-10 times.