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UDK. 626.86: 575.1
RESEARCH OF IRRIGATED SOILS AND THEIR PROPERTIES OF THE BUKHARA
OASIS (on the example of OLOT district)
Nazarova Sevara Mustakimovna
Associate Professor, Bukhara State University
Sayfiyeva Elmira Sodikovna
Independent Researcher, Bukhara State University
Annotasiya.
Из 4304,32 тыс. га орошаемых земель нашей республики большую часть
(около 50%) составляют засоленные в разной степени почвы, что снижает общую
продуктивность сельскохозяйственных культур на орошаемых массивах. В статье
представлена подробная информация об орошаемых почвах Олотского района и их
свойствах. Кроме того, были приняты меры по повышению плодородия почв.
Annotation.
The main part (about 50%) of the 4304.32 thousand hectares of irrigated land of our
republic is saline soils to varying degrees, which reduces the overall productivity of agricultural
crops in irrigated areas. This article provides detailed information on the irrigated soils of the
Olot district and their properties. In addition, measures to improve soil fertility are presented.
Ключевые слова:
Олотский район, орошаемые почвы, механический состав почв, дельта
реки Зарафшан, мелиорация земель, плодородие почв, нормы орошения, засоление,
материнская порода, пролювиальные, аллювиальные, лессовидные пески, грунтовые воды,
минерализация.
Key words:
Olot district, irrigated soils, mechanical composition of soils, Zarafshan River Delta,
land reclamation, soil fertility, irrigation standards, salinity, parent rock, proluvial, alluvial,
loess-like sands, groundwater, mineralization.
ntroduction.
Bukhara region is located in the lower reaches of the Zarafshan River. The
entire oasis consists of areas formed by wide and short river beds. In the wide part of the river, in
the lower part of Bukhara, the Kara Kul oases are located.[3.4.]
The Bukhara oasis enters the Tertiary deposits of the Avtobacha and Kyzyltepa plateaus of
the Navoi-Konimiyek Khazar thrust. According to the natural zoning of agriculture, Bukhara
region belongs to the subtropical desert zone of the southern Kyzyl-Kum and northern Kyzyl-
Kum districts of the Central Asian steppe province.[11.12]
The reason for the deterioration of the ecological and reclamation situation in the irrigated
dekhkan region is the result of the extensive use of existing water and land resources. In all
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projects for the development of new lands, it was planned to discharge the waters of the
collector-drainage networks into the lowlands and riverbeds.
As a result of the large-scale implementation of projects that are not theoretically and
practically justified, the quality of river waters is sharply deteriorating, artificial lakes and
swamps are formed around the developed areas, the natural balance is disturbed, and the
ecological situation is deteriorating.
The most negative aspect of salinization is that it destroys the soil structure, worsens the
water-physical, physico-chemical properties, affects the microbiological activity and other
properties of soils, causing soil degradation.
This requires inspection of the areas, a thorough study of the degree of salinity of the soil
cover and soil subsoil, types of salinity.
Research object and method. In scientific research conducted to study the main properties and
ecological and melioration state of irrigated soils of the Olot district of the Bukhara vozh, new
data were obtained on the mechanical composition of irrigated soils, agrochemical properties,
main parameters of groundwater, types and levels of salinity.
In the Olot district, various geomorphological, lithological, hydrogeological and climatic
conditions have influenced the soil formation processes in the region in different directions. As a
result of natural geographical conditions and the influence of anthropogenic factors, irrigated
meadow and barren soils have been formed in the district. In the area of the district where
the research was conducted, there are irrigated meadow and barren and partially meadow swamp
soils.
The irrigated lands of the Olot district, including F. Aloev, O. Ubaydov, developed in the
V-VI centuries BC on Quaternary alluvial deposits located at a depth of 14-20 m. Nowadays, the
upper part of these alluvial deposits is covered with modern, cultural anthropogenic
agroirrigation layers. The level and degree of mineralization of groundwater are distributed in
these local and alluvial rocks, which periodically lead to the formation of various salinization
processes under the influence of various micro- and mesoreliefs.[2.]
Soil samples taken from the Olot district were chemically analyzed in laboratory
conditions, the amount of salts was determined, and the type and degree of salinity in them were
determined according to the I and II methods of water absorption (Lebedev).
As a result of field research and laboratory analysis, it was found that the quantitative
indicators of salts, the degree of salinity and types of salinity differ in different areas of the
district.
Mapping materials based on water absorption analyses and data from other modern rapid
methods for determining the degree of soil salinity (electroconductometric method) serve as the
primary sources for recording, accounting and compiling cartograms of saline soils.
In order to ensure the implementation of the Resolution of the Cabinet of Ministers of the
Republic of Uzbekistan dated February 24, 2014 No. 39 “On additional measures to ensure the
unconditional implementation of the State Program for Improving the Reclamation Condition of
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Irrigated Lands and Rational Use of Water Resources for 2013-2017”, the Subsidiary Enterprise
of Soil Bonitation, the Scientific Research Institute of Soil Science and Agrochemistry and the
Bukhara and Andijan branches of the Uzdaverloyiha DILI carried out work to determine and
map the levels of soil salinity of irrigated agricultural land in 93 districts of the republic's regions
during 2014-2017. Accordingly, out of a total of 226.4 thousand hectares of irrigated land in
Bukhara region (12 districts), 192.8 thousand hectares (85.1%) are saline to varying degrees, of
which 119,900 hectares (52.9%) are weakly saline, 49,200 hectares (21.8%) are moderately
saline, 15,200 hectares (6.7%) are severely saline, and 8,476.8 hectares (3.7%) are very severely
saline. (3)
There are a total of 17,218.0 hectares of irrigated land in Olot district, of which 13,233.1
hectares (76.9%) are saline to varying degrees. The salinity level is as follows: 4,478.9 hectares
(26.01%) are weakly saline, 5,012.5 hectares (29.11%) are moderately saline,
Table 1
Characteristics of irrigated soils of Olot district according to the degree of salinity
Salinity level
Total irrigated
land
Unsalted
Weak
Averag
e
Strong Very
strong
Area, in hectares 17218,0
3985,0
4478,7
5012,5
2038,7 1703,1
Area, in %
100
23,14
26,01
29,11
11,84
9,9
In the conditions of the natural and artificially drained district, as a result of irrigation at
high rates for many years, large amounts of water that have been absorbed, merging with
groundwater, allow them to rise sharply to the surface, which in turn leads to rapid salt
accumulation in the soil and deterioration of the reclamation condition of irrigated lands. The
state of groundwater is seasonal, and if the depth typical for these lands decreases to 2-3 meters
after the end of the growing season, it increases to 0.5-1.5 meters during the growing season,
with an amplitude of seasonal fluctuations of 1.0-1.5 meters.
The fact that the main part of the district is located much higher than the optimal depth,
regardless of the geomorphological region to which they belong, in turn actively participates in
the processes of soil formation and soil salinization.
The irrigated soils distributed in the Olot district are classified by their mechanical
composition as heavy sandy loam and clayey, medium sandy loam, light sandy loam and sandy
loam. Medium sandy loam and sandy loam are widespread.
Experiments show that with the lightening of the soil mechanical composition, the
absorption capacity and the water column increase, the leaching of salts becomes easier, and vice
versa, not only does it become more difficult, but also the capillary rise of saline waters
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negatively affects the saline vegetation that has appeared in the depths of the soil where the root
system is located.[4]
During scientific research, it became clear that the amount of physical clay in the
mechanical composition of these soils changes with distance from the canal. If in the areas
located closer to the canal, the amount of physical clay is 30-32% in a thickness of 0-66 cm, then
in areas located at 200 and 300 m, the amount of these fractions increases to 40%. Along with
the increase in the amount of medium loam fractions in the horizons of the soil section, the
formation of heavy loamy soils is observed in the areas moving away from the canal. Based on
the collected data, the quantitative and qualitative changes in the mechanical composition of the
studied soils, based on the above laws, depend not only on the influence of the soil-forming
parent rock and relief, but also on the turbidity level of suspended sediments, the length of
irrigation channels, and the composition of particles in the water flowing in the ditches located in
the field.
When leaching, it is necessary to take into account the salinity level, mechanical
composition, water permeability (water-physical properties) of the soil, as well as the amount
and reserves of salts in the root zone (0-1m). Water standards for leaching vary depending on the
mechanical composition. Depending on the mechanical composition of the soil, the average salt
leaching rate is 3000-3500 m3/ha for light layered soils, 3500-5000 m3/ha for moderately saline
soils by 2-3 times of flooding, 4000-5000 m3/ha for strongly saline soils by 3 times of flooding,
5000-6500 m3/ha for very saline soils of different mechanical composition by 3-4 times of
flooding, and 6000-7500 m3/ha for strongly and very strongly saline soils of heavy mechanical
composition by 3-4 times of flooding. The amount of salts in the soil after leaching should be
reduced to 0.01% of chlorine ions and to 0.4-0.6% of dry residue. When determining the
standards for salt leaching, the recommendations of the UzPITI (now PSUEMTI) (Scientific
Research Institute of Cotton Breeding, Seed Breeding and Cultivation Agrotechnology) (Table 2)
and available data (based on salinity cartograms according to the A.E. Nerozin formula) are
used.[2]
Conclusion. In order to prevent the salinization process in the irrigated lands of the Olot
district, to systematically increase soil fertility and productivity, and the yield of agricultural
crops, it is necessary to fully implement hydrotechnical, agrotechnical and land reclamation
measures. When salt leaching, it is necessary to take into account the degree of salinity,
mechanical composition, water permeability (water-physical properties) of the soil, as well as the
amount and reserves of salts in the root-spreading layer (0-1m). Water standards for salt leaching
vary depending on the mechanical composition. When implementing measures aimed at
improving the land reclamation condition, it is extremely important to first correctly select the
reclamation objects that need improvement, and an integrated approach to this issue is necessary
from both a scientific and practical perspective.
References:
1. Developed by the State Committee of the Republic of Uzbekistan for Land Resources,
Geodesy, Cartography and State Cadastre and the State Research Institute of Soil Science
and Agrochemistry: “Methodological Guide for Mapping, Accounting and Determining the
Standards of Salting-Out Soils”. 2014. 45-46 pp.
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2. Umarov M. Physical Properties of Soils of New and Promising Irrigation Regions of the
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