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GEOCHEMISTRY OF WATER-SOLUBLE SALTS IN IRRIGATED SOILS
Muhammadno‘monjon Iqrorjon o‘g‘li Aktamov
PhD Candidate, Fergana State University
https://doi.org/10.5281/zenodo.14551369
Abstract
This research explores the composition and distribution of water-soluble
salts in the genetic horizons of irrigated meadow-saz soils. Based on dry residue
levels, these soils are categorized as moderately to strongly saline. Using the
concentrations of water-soluble ions, hypothetical salts were determined. The
analysis highlights that sulfate salts are predominant, and the salinity levels are
significantly influenced by mineralized groundwater with a saz regime.
Keywords:
salinity, hypothetical salts, geochemical analysis, water
extraction, dry residue, sulfate salts.
Introduction
In the 1930s, extensive soil studies were conducted in Central Asia to
identify and develop lands suitable for irrigation. These efforts focused on
analyzing the composition of soil, parent materials, and groundwater, as well as
the distribution of soluble salts across various geomorphological regions. These
studies laid the groundwork for landscape-geochemical analysis and enabled the
classification of soils based on their salinity and reclamation potential.
Today, in arid regions such as Central Fergana, the study of water-soluble salt
geochemistry is essential. These investigations provide insights into combating
secondary salinization, justifying large-scale reclamation projects, and
advancing sustainable irrigation practices.
Geochemical Dynamics in Saline Soils
Salinity in arid regions arises from geochemical processes that mobilize and
accumulate salts. These processes involve interactions between mobile ions,
including
Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, SO₄²⁻
, and
HCO₃⁻
. Salt deposition occurs
primarily in response to evaporation exceeding precipitation, particularly in
areas with poor drainage systems.
Key Stages of Salt Migration
1.
Mobilization:
Transformation of salts into soluble forms for easy
transport.
2.
Migration:
Movement of salts through water flow.
3.
Accumulation:
Deposition of salts in fixed forms within the soil profile.
In arid landscapes, these processes are accelerated by factors such as rising
groundwater levels, irrigation, and fertilization practices.
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Predominant Salts and Their Characteristics
Irrigated meadow-saz soils contain various soluble salts, as shown in
Table 1
:
Table 1: Common Soluble Salts in
Meadow-Saz Soils
Chemical
Formula
Solubility
Sodium bicarbonate
NaHCO₃
Highly soluble
Magnesium sulfate
MgSO₄•7H₂O
Highly soluble
Gypsum
CaSO₄
‧
H₂O
Sparingly
soluble
Mirabilite
Na₂SO₄
‧
10H₂O
Highly soluble
Sodium chloride
NaCl
Highly soluble
The accumulation of these salts can occur in both lateral and vertical directions,
leading to significant deposits over geological timescales. These deposits are
particularly prevalent in arid and semi-arid regions.
Findings
Distribution of Salts
In the irrigated soils of Central Fergana, sulfate salts dominate the salinity
profile.
Calcium sulfate (CaSO₄)
is the most prevalent, followed by
magnesium
sulfate (MgSO₄)
,
sodium bicarbonate (NaHCO₃)
, and
sodium sulfate
(Na₂SO₄)
. Groundwater plays a significant role in shaping these distributions, as
illustrated in
Table 2
:
Table 2: Ion Concentrations in
Meadow-Saz Soils
Depth
(cm)
HCO₃⁻
Cl⁻
SO₄²⁻
Ca²⁺
Mg²⁺
Na⁺
0-30
1.010
-
- -
-
-
-
30-45
1.238
-
- -
-
-
-
45-87
1.301
-
- -
-
-
-
Impact of Irrigation
Continuous irrigation alters the soil’s hydrological and salinity dynamics. While
irrigation boosts crop productivity, it can also exacerbate secondary salinization
if drainage systems are insufficient. Older irrigated soils show increased salt
accumulation in deeper layers, highlighting the need for improved irrigation
management.
Conclusion
Effective salinity management in irrigated soils involves addressing both natural
and human-induced factors. In arid climates like Central Fergana, strategies such
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as proper irrigation scheduling, advanced drainage systems, and targeted
fertilization are crucial for maintaining soil health and agricultural productivity.
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