Abstract form

Exchangeable cations of the meadow-chestnut soils at the Dzhanybek
Research Station in the Northern Caspian Region
A. V. KOLESNIKOV
Institute of Forest Research, Russian Academy of Sciences, 143030, Sovetskaya str., 21,
Uspenskoe, Odintsovsky district, Moscow region, Russia.
Contact e-mail: wheelwrights@rambler.ru, root@ilan.msk.ru
The predominance of exchangeable Ca 2+ , Mg 2+ , and Na + in soils of arid regions is a
well-known fact. The relationship between these cations in the soil adsorption complex
(SAC) is determined by the content and chemical composition of soluble salts in the soil
solution and by the values of the selectivity factors. This general regularity is well seen
in the studied soils of solonetzic complexes in the semidesert zone of the northern
Caspian region. The soil cover differentiation is related to the microtopography:
microhighs are occupied by solonchakous solonetzes, and microlows are occupied by
nonsaline meadow chestnut soils. In the solonchakous solonetzes, the portion of
exchangeable Na + reaches 30 – 40% of the cation exchange capacity (CEC); in the
meadow-chestnut soils, it does not exceed 1 – 2% of the CEC.
The studies of the composition of the SAC in the soils of solonetzic complexes at the
Dzhanybek Research Station were mainly focused on the solonchakous solonetzes, as
the high percentage of exchangeable sodium in them was one of the factors exerting a
negative effect on forest shelterbelts and crops grown in the course of the agroforest
amelioration of this area. The SAC of meadow-chestnut soils was studied to a lesser
extent.
Our work is aimed at studying the composition of the SAC and the nature of the CEC in
the meadow chestnut soils located in the microlows under virgin herbaceous vegetation
and in the analogous soils located under artificially planted forest shelterbelts
Taking into account that the main carriers of exchangeable cations are the organic
matter and clay minerals, the humus content, particle-size distribution, and the
mineralogical composition of the clay and fine silt fractions were determined. We made
approximate calculations to estimate the contribution of these factors to the value of the
effective CEC in the soils. The activity of Na + and the salt reserves were determined to
characterize the level of the soil salinity
The meadow-chestnut soils of the Dzhanybek Research Station are characterized by the
eluvial-illuvial textural differentiation of the solonetzic type. It is supposed that
solonetzic process took place in these soils at the earlier stages of their development.
Later, the excessive salts and the adsorbed sodium were removed from these soils by the
fresh water supplied with the snowmelt.
In the virgin and ameliorated meadow-chestnut soils, the portions of exchangeable
calcium and magnesium in the CEC reach 70–80 and 13–30%, respectively. The
composition of exchangeable cations remains relatively stable in the entire profile. The
exchangeable sodium percentage is less than 1%, and there are no indications of the
current activity of solonetzic process in the profiles of meadow-chestnut soils.
The research was supported by the Russian Foundation for Basic Studies (project 09-
04-00030).
Key words: salt-affected soils, soil salinization, soil adsorption complex, cation
exchange in soils.
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