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Zakirova Salomat Kasimbaevna, Doctoral student, National University of Uzbekistan named after M. Ulugbek, Tashkent Abdullaev Sagdulla, Professor, of the department National University of Uzbekistan named after M. Ulugbek, Tashkent E-mail: [email protected]
THE SALINITY STATE OF SOILS IN THE LOWER REACHES OF KASHKADARYA AND THE BASIS FOR ITS REGULATION
Abstract: In the article, with the help of experimental studies, the present state of salinity in irrigated soils of the lower reaches of the Kashkadarya River has been revealed, and their movements and regulatory factors have been scientifically substantiated.
Keywords: salinity, soils, effective land use, Kashkadarya region, soil fertility, irrigation, underground water.
Introduction
The solution of the problem ofeffective land use is determined by the development of agricultural production, the climatic conditions of soils, and the ameliorative state of the terrain and the indicator of the use of land and water resources. The emergence of erosion and salinization of irrigated lands disrupts the fertility of the soil, sharply reduces the crop yield from crops, and damages irrigated agriculture. Today, one of these territories exists in the irrigated lands of the Kashkadarya region and 70% of the region's land fund is salinized to varying degrees [3].
Continuous use of irrigated soils of the Kashkadarya oasis in production, violation of the irrigation order and as a result of slow implementation of agro technical measures, increase of underground water of the soil layer, the emergence of various degrees of salinity was revealed [1].
The study of soils in field and laboratory conditions and their analysis showed that the weak activity of aquatic farms and the surrender of unfinished work on the compilation of land to households and, in turn, the assumption of a number of inaccuracies in the use of virgin lands by farms, i.e. Due to the long-term immersion of land, the spreading of soil developed. In addition, the agro physical, agrochemical and ameliorative state of soils began to deteriorate due to monoculture in the same field for many years without reckoning with rec-
lamation measures. As a result, the newly acquired irrigated lands did not yield the expected result, soil salinity began, and secondary salinization and irrigation erosion arose. Despite this, in the present day the development of reclamation works in the oasis does not give a sufficient effect, because the agro technical measures carried out have negative sides along with positive sides, i.e. The process of secondary salinization of irrigated land with the threat of accumulation of salts neither decrease. The accumulation of a large number of toxic salts in different soil layers leads to a decrease in soil fertility [1].
It is necessary to emphasize the importance of the fact that the main reason for the slow increase in the fertility of agricultural crops is the incomplete improvement of irrigation and collector systems-drainage ditches and specialists often do not take into account the properties of soil layers when using water during prolonged irrigation and the diversity of ameliorative stratification of different regions and landscapes and widespread use in the practice of a monotonous agricultural system, a soil order, and as a result, a decrease in the amount of humus and nutrient substances increase erosion, salinity, gypsum, occurrence saline soils as well as processes of strong seal [2].
The main and most important reason in this direction is the increased salinity of the soil, because in the
fields where experiments are carried out, cotton yields have decreased by 8-10 c per hectare.
Materials and methods
Geomorphological, hydrogeological conditions of the terrain, relief and lithological structure were taken into account from the scientific point of view, morphology of soil of lands where agricultural crops are grown, samples from genetic layers were determined, the content of water-soluble salts in laboratory conditions were determined. The percentage of salts in the soil was determined on the basis of the manual "Guidelines for the conduct of chemical and agro physical analyzes of soils in the monitoring of land", published in 2004 with the approval of the State Committee of Land Resources of the Republic of Uzbekistan. Preparation of aqueous extract and easily soluble salts of chlorine ions by the Mohr method, content of the SO4 method of extracting sulfuric acid, Ca++ and Mg++ by Trilon-B, part of Na+ and K+ is determined by a flame photometer, and the other part by calculating the difference between anions and cations by evaporation dry residues. In addition, based on the foregoing guidance, saline stocks in different soil layers, salinity levels and types of salinity were identified [2].
For this reason, a successful solution to this problem can be achieved only through a thorough and comprehensive analysis of the soil layers of the region, research of the ameliorative model (regional, territorial, specific area), increase and regulation of the plant system of soil and increase their yield. To this end, it is necessary to improve, use and develop methods that improve soil fertility, assess the ecological and ameliorative state and increase the productive capacity of irrigated lands, exfoliate soil properties, relief, weather and land reclamation system depending on the type of crops and the wide use of agrochemical, other methods.
To do this, based on analytical analysis of data obtained from production experiments based on existing methods in natural conditions for reclamation of saline lands, practical use of the conclusions and recommendations based on the comparison of the data obtained as a result of our scientific research is important.
This article presents data on the assessment of the current reclamation state of the lands of the supporting farms of the Karshi steppe and our main goal is to demonstrate the opportunities for widespread use of the soils of the Kashkadarya region, the preservation, restoration
and enhancement of their fertility, thereby ensuring a high yield from the lands of the region.
A diverse analysis of scientific research conducted in the lower reaches of Kashkadarya has shown that the process of accumulation of salts in the soil is mainly due to evaporation and in the midst of transpiration, i.e. late spring, summer and autumn months. In winter and early spring, under the influence of precipitation, such water-soluble salts as Na2SO4, MgSO4 along with downstream currents seep to groundwater and increase their level of mineralization.
Sulfates such as Na2SO4, gypsum (CaSO4) and calcium carbonate (CaCO3) move during heavy precipitation with seasonal salinity reduction (in winter and spring), and a negligible amount returns to groundwater. In the last month of spring the next seasonal water rotation process is repeated, in the sedimentary season the process of reducing salinity again changes and the ground waters are again enriched with water-soluble salts. For several centuries the repetition of a salt pattern of this type leads to delamina-tion of the salts and leaving this compound, the ground waters of Fe(Al)2O3 and SiO3, Ca-Mg(CO3)2, CaCO3 and CaSO4 are not returned back to the soil layers. Na2SO4 forms dense and soft salt-bearing layers between soil layers and groundwater, and some NaCl, MgCl2, MgSO4 and Na2SO4 accumulate in the soil and groundwater solution and continue its circulation in different soil layers.
In addition, the process ofsalt circulation is the process of accumulating slightly soluble salts (SiO2, Ca(HCO3)2, Mg(CO3)2, CaCO3 and CaSO4) in solid soil layers. Accumulation of salts in solid soil layers, highly soluble salts have a sharp seasonal character and appear in the upper soil layers (NaNO3, MgCl2, CaCl2, NaCl, Na2SO4).
The weaker the solubility of salts, the earlier they reach the saturation point of the solution, and the wider their circulation in the soil layers and their geographic range of accumulation.
The direction of the change in the content of salts in the soils of the studied regions is determined by transpiration and evaporation in plant tissues. At the same time, the depth of groundwater and high pollination, characterizing their mechanical composition and low sandy state, strongly influence the intensity of salinity.
Observations have shown that the diversity of natural and irrigation-economic conditions is manifested on a large scale and diverse in irrigated agriculture, in the pro-
cesses of quantitative and qualitative composition of sali-nization and accumulation ofsalts in land use, because the direction and intensity of the salinization process are very high. The appearance of this process, in our opinion, depends on the thickness of the collectors and the drainage ditches and the weak differentiation of their distance according to the lithology and geomorphology ofthe terrain.
As field observations and many analytical data have shown, in different soil sections and in some places of the surface layer of the investigated areas are not saline, even washed-out soils are partially salinized and the appearance of fields with salty spots.
The reason is that it is possible to single out the entire degree of salinity in terms of the degree and type of salinity in irrigated takyr, takyr-meadow and meadow soils and at the same time in the structure of the layers containing salts.
In terms of the depth of the salt layer (salt maximum), its depth, according to the degree of salinity, shows various, mainly lithological, geomorphological, hydrogeological, climatic, soil-ameliorative and irrigation-economic conditions, among the studied soils, besides saline soils salts at a depth of 0-30 cm), heavily saline soils (30-50 cm), deeply saline (50-100 cm),
Table 1. - The content of water-of the lower reaches
saline-marsh (50-100 cm), deep salt-marsh (100-150 cm) and not saline soils salts at a depth of 0-200 cm) (1-table).
As shown in the table, the content of water-soluble salts in the investigated territory varies on a large scale, i.e. there are not saline soils (washed by irrigation of the soil) to strongly saline soils. According to the content of salts in the layers of the investigated soils, where the root system of plants is widespread, the salinity is mainly weakly and in an average degree and in some cases on the highly saline upper arable layer, the salt content is from 0.110-0.130 to 0.560-0.730%, the chlorine content is 0.014-0.09% and sulfates 0.037-0.325%, and in the lower layers it increases to 0.880-1.235% (8, 53, 14 cuts). Throughout the section to groundwater (43-section) the salt content is high; i.e. soil is saline throughout the profile.
Results and discussion
According to the nature of salinity, the soils are divided into chloride-sulfate, rarely chloride. Basically, the chloride-sulfate type of salinity is rare and typical for medium saline soils and their highly saline types remain the same. By variety and quality composition among the various salts, sulfates, Na2SO4, MgSO4 and the next place is occupied by CaSO4.
soluble salts of irrigated soils of Kashkadarya,%
Section No., Depth of the Dry residue Cl - SO-2 4 Salinity
farm, district layer, cm . Type Degree
1 2 3 4 5 6 7
0-15 0.130 0.021 0.037 x-c low
17. KP "Pakhta-kor" Kasbi 15-34 34-54 0.095 0.150 0.017 0.014 0.020 0.064 C-x x-c low low
54-82 0.425 0.021 0.232 C low
82-160 0.450 0.024 0.220 C low
0-21 0.180 0.031 0.068 x-c low
14 KP "Pakhtakor" Kasbi 21-62 0.150 0.028 0.045 x-c low
62-90 90-125 0.185 0.975 0.034 0.101 0.066 0.529 x-c x-c low strong
125-155 1.235 0.094 0.740 C strong
155-180 0.925 0.059 0.549 C strong
0-31 0.510 0.038 0.269 C middle
39. KP "Galaba" Kasbi 31-48 48-72 0.145 0.110 0.021 0.021 0.053 0.033 x-c x-c low low
72-99 0.095 0.014 0.029 x-c low
99-136 0.120 0.021 0.041 x-c low
1 2 3 4 5 6 7
39. KP "Galaba" 136-185 0.110 0.017 0.037 x-c low
Kasbi 185-220 0.115 0.021 0.033 x-c low
0-33 0.200 0.028 0.070 x-c low
53. MG "Gu-listan" Mubarak 33-53 53-85 85-120 0.235 0.970 1.040 0.024 0.038 0.052 0.103 0.570 0.625 x-c c c low middle middle
120-160 1.095 0.060 0.648 c middle
038 0.235 0.028 0.076 x-c low
63 MX "Hitoy" Mubarak 38-58 0.265 0.021 0.117 x-c low
58-90 0.515 0.035 0.251 c middle
90-106 0.420 0.031 0.208 x-c low
106-150 0.410 0.035 0.201 x-c middle
0-30 0.215 0.024 0.080 x-c low
66. MX "Khitoy" Mubarak 30-40 48-79 0.200 0.225 0.028 0.031 0.060 0.068 x-c x-c low low
79-121 0.220 0.024 0.072 x-c low
121-163 0.185 0.028 0.055 x-c low
In addition, in order to reliably classify saline soils in our studies, we tried to evaluate the studied soils by salinity. As shown by the data of the two tables in the soil layers of farms, the total content of water-soluble salts is significantly different from each other. For example, in "Pakhtakor" and "Khitoy" farms in the arable horizon, the soil varies from 4.6-5.2 to 9-10 tons/ha, then in the "Galaba" and "Gulistan" farms this indicator reaches 23-30 tons/ha.
Table 2.- Stock of water-soluble salts of irrigated
Analysis ofthe obtained data on the salt reserve showed that in the soil layers the total reserve of water-soluble salts in the two-meter layer varies from 35-73 ("Galaba" farm) to 226-232 tons/ha ("Gulistan" farm), respectively, in one meter layer of soil of Gulistan of Mubarak region, this indicator ranges from 17-46 to 81-112 t/ha, and the lowest content of salts is distributed on the fields of the "Galaba" farm of the Kasbi district. The remaining farms occupy intermediate positions (2-table).
soils of the lower reaches of Kashkadarya, t/ha
Farm, district Section № Layer, cm
0-30 0-100 100-200 0-200
"Pakhtakor" Kasbi 17 15 5.46 6.72 37.46 19.30 63.00 27.76 100.46 47.06
14 7.56 34.80 144.28 179.08
32 6.51 46.97 26.92 73.89
"Galaba" Kasbi 27 4.62 17.63 17.43 35.06
39 21.42 33.0 16.02 49.02
"Gulistan" Mubarak 53 8.40 81.11 151.76 232.87
43 30.66 112.33 113.89 226.22
55 23.52 37.36 41.09 78.45
"Hitoy" Mubarak 63 9.87 48.87 57.49 106.36
60 6.09 20.06 13.21 33.27
66 9.03 30.30 26.93 57.23
On the surface and two-meter layers of soil horizons, 15 soil sections from 1.4 g/cm3 of volume, too large sa-the average reserve of water-soluble salts was taken from linity patches were observed not only in the general fields
of the studied areas, but also in individual farm boundaries such changes (3-table).
Table 3.- Stock of water-soluble salts in the average mass of irrigated soils of the lower reaches of Kashkadarya, t/ha
Farm, district Section № Layer, cm
0-30 0-100 100-200 0-200
"Pakhtakor" Kasbi 17, 15, 14 6.58 30.52 78.35 108.87
"Galaba" Kasbi 32, 27, 39 10.85 32.53 20.12 52.65
"Gulistan" Mubarak 53, 43, 55 20.86 76.33 102.25 178.58
"Khitoy" Mubarak 63, 60, 66 8.33 33.08 32.54 65.62
As can be seen from the table, water-soluble salts are distributed in the fields of the Kasbi and Mubarak regions in a bulk mass of the soil layer with a calculation of 1.4 g/cm3. On the basis of the data obtained, one can come to the conclusion that the irrigation started in different periods and different irrigation and economic conditions exerted a peculiar influence on the ameliorative-ecological state of soils distributed in the lower reaches of the Kashkadarya. At present, this confirms the intensification of salinity at the stage of a peculiar development of the studied soils. However, this process is supported by the formation of a type of erosion in the regulation of annual washing and redistribution ofwater in a certain part of irrigated areas.
The increase in the content of accumulated water-soluble salts in the two-meter layers of the studied soil layers to 200 tons/hectare is currently considered not very high, but if timely not to take ameliorative measures to prevent factors that promote secondary salinization and cause accumulation of salts they can gradually increase. Because soil horizons and groundwater movement show an increase in the total salt content compared to the previous 40-50 years.
On this basis, the reclamation of the irrigated lands in the Kashkadarya region together with the areas studied is not stable, because the groundwater of the land retains an average (3-10 g/l) and strong (10 g/l) mineralization.
For centuries, the presence of a process of underground water flow and its expending to transpiration leads to a weak formation of a drainage system and the accumulation of a large number of salts, for example, for the upper 10 meter layer per hectare, this figure exceeds one thousand tons, at the same time a large part of water-soluble salts (at depths of 0-3 m) accumulate on the evaporating surface [1].
Conclusion
The obtained data allow us to estimate the soil-ameliorative state of the irrigated areas of the Kashkadarya Oasis in this way: there are soils with medium and strong salinity in each farm (area), irrespective of such conditions; it is possible to conduct irrigated agriculture efficiently and with great success. To achieve such success, first of all, it is necessary to take measures to reduce the salinity of groundwater and at the same time, it is necessary to intensively carry out reclamation work, and also to bring the soil to the necessary condition.
References:
1.
Rasulov A. M. Saline soils of the Karshi steppe and ways of their development and enhancement of fertility. Author's Diss. Doctor of Science.- Tashkent,- 1969.- 50 p.
2. Rasulov A. M. Soils of the Karshi steppe: ways to develop and improve fertility // Tashkent: FAN,- 1976.- 248 p.
3. Abdullaev S. (ed.). Guidelines for conducting chemical and agrophysical analyzes of soils in land monitoring // Tashkent: State Committee for Land Resources of the Republic of Uzbekistan,- 2004.- P. 39-40; - P. 64-65.
