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Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008) 107-112
107
CLAY MINERALOGY INFLUENCE ON THE PHYSICAL AND CHEMICAL
PROPERTIES OF VERTISOLS FROM ROMANIA
Victoria Mocanu, C. Craciun, M. Eftene, Sorina Dumitru, Valentina Cotet
National Research-Development Institute for Soil Science,
Agrochemistry and Environment Protection-Bucharest
Abstract
The mineralogical investigation of the 33 profiles of vertisol from Romania
indicated that there are two principal geographical zones with vertisols (West and
South) which present some quantitative mineralogical differences at the colloidal
level. In spite of the fact that in all investigated profiles, the quantitative
mineralogical composition of the clay fraction (below 2
μ
) was the same, (smectite,
illite and kaolinite) the vertisols from the western zone show a higher content of
smectite (montmorillonite) and a lower content of illite in comparison with
vertisols from southern zone.
The correlations between some physical indices of soil and smectite
quantity indicated that an increase of soil smectite content determines an increase
of bulk density and compaction degree, concomitantly with a decrease of total
porosity and air porosity.
The established relationships between some chemical indices and
mineralogical parameters indicated that cation exchange properties and reaction
of these soils appear more closely related to the quality (mineralogical
composition) than to the quantity of clay fraction.
The empirical relationships established between physical and chemical
indices of vertisols and mineralogical parameters suggest that in some cases,
considered favorable, the clay mineral information could allow some predictions
on the physical and chemical properties, in spite of the fact that such of predictions
have a limited value from quantitative point of view.
Key words: vertosol, clay minerals
INTRODUCTION
The physical and chemical properties of soils are strongly influenced by the
soil constituents which have high specific surface or highly reactive surfaces. Since
high specific surface is associated with small particle size, the colloidal fraction (below
2 µm) of the soil is the dominant factor in influencing certain properties of the soil.
The usefulness of clay mineral information depends upon how closely clay
minerals influence physical and chemical properties of the soils and upon our
methodological posibilities to make evident and to estimate this influence.
The goal of this paper is to present some aspects referring to the mineralogical
composition of the clay fraction (below 2μ) from vertisols of Romania, and the
influence of the clay minerals on some physical and chemical properties involved in
the fertility of these soils.
Victoria Mocanu et.al. / Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008)107-112
108
MATERIAL AND METHODS
A number of 33 soil profiles classified as vertisols were selected for this study.
The location of the sampling sites is given in Figure 1.
The clay fraction below 2μ was separated from the soil by gravity
sedimentation using Na OH 4% as dispersing agent (Craciun &Gata, 1986).
For the X –ray analysis oriented specimens were separated by depositing 3 ml
of clay suspension into a glass slide. All clay fraction samples were subjected to three
types of X-ray examination (K-saturated-, Ca –saturated- and glycolated Ca –saturated
sample).
The mineralogical composition of the clay fraction was estimated by X-ray
diffraction using the intensities of the characteristic basal reflections (001) of the
identified clay minerals (Gâţă et al. 1981). The X-ray diffraction patterns were carried
out with a DRON-2,0 difractometer using Ni-filtered CuKα radiation.
The physical and chemical analyses were carried out by the usual methods.
The influence of the clay minerals on the physical and chemical properties of these
soils has been studied using the statistical correlation between physical and chemical
indices, on once hand and mineralogical parameters (the contents of the principal clay
minerals and clay content of the soil) on the other hand.
Fig. nr. 1 Emplacement of the investigated soil profiles
Victoria Mocanu et.al. / Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008)107-112
109
Fig. 2 X-ray diffraction patterns of the clay fraction (<2μm) separated from the surface horizon
of the Balaci vertisol (values in nm)
A= K-saturated sample; B= Ca-saturated sample; C= Ethylen glycol treated Ca-sample
RESULTS AND DISCUSSION
From the qualitative point of view, there are no mineralogical differences
between the investigated soil profiles, the identified clay minerals in all Romanian
vertisols being smectite, illite and kaolinite (Fig. 2).
Generally, the results of mineralogical analyses indicate the existence of two
groups of soil profiles occurring in the distinct geographical zones.
The quantitative mineralogical differences between the two groups of profiles
refer to the ratio of the principal components of the clay (Table 1).
Victoria Mocanu et.al. / Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008)107-112
110
Table 1
THE MINERALOGICAL COMPOSITION (AVERAGE VALUE) OF THE CLAY
FROM STUDIED VERTISOLS AS FUNCTION OF GEOGRAPHICAL ZONE
Mineralogical composition of the clay(%) Geographical zone
Smectite Illite Kaolinite
Smectite/Illite ratio
Whole country 66 30 4 2.20
Western zone 71 25 4 2.84
Southern zone 61 36 3 1.69
The smectite /illite ratio of the vertisols located in the Western part of Romania
show higher values (2.84) comparing to the vertisols located in Southern part of
Romania (1.69).
In the case of some vertisols from Southern part of Romania the attempts to
correlate the mineralogical parameters with the indices which express certain physical
and chemical properties point out the influence of the clay quality and quantity on these
properties.
Since the physical and chemical indices do not correlate preferentially linear or
parabolic with mineralogical parameters in the figures are given only the linear
correlation results.
The correlation attempts of the physical and chemical indices with the
parameters which express the quantity and quality of the clay fraction, show a
similarity between the influence of the clay content and soil smectite content (Figure
3,4).
The relationship of the clay parameters with the studied physical and chemical
indices is direct except the relation with total porosity which is inverse.
CONCLUSIONS
- The identified clay minerals in the vertisols of Romania are, in order of
occurence, smectite (montmorillonite), illite and kaolinite.
- There are in Romania two main areas occupied by vertisols which are
different from the quantitative mineralogical point of view.
- The established relation between physical and chemical indices on the side,
and mineralogical parameters on the other side, show that in comparison with physical
properties of vertisols those chemical appear more closely related to clay quality than
clay quantity. These relations could be considered take an attempts of clay influence
quantification on the soil properties.
Victoria Mocanu et.al. / Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008)107-112
111
y=0,009x+1,040
R=0,459**
0
0,5
1
1,5
2
0 204060
Bulkdensity(g/cm3)
Soilclayfractioncontent(%)
DA
Linear(DA)
y=0,011x+1,168
R=0,447**
0
0,5
1
1,5
2
0 10203040
Bulkdensity(g/cm3)
Soilsmectitecontent(%)
DA
Linear(DA)
y=‐0,358x+60,91
R=‐0,451**
0
10
20
30
40
50
60
0 102030405060
Totalporosity(%v/v)
Soilclayfractioncontent(%)
PT
Linear(PT)
y=0,859x‐ 6,680
R=0,513***
‐20
‐10
0
10
20
30
40
0 10203040
Degreeofcompactationindex(%
v/v)
Soilsmectitecontent(%)
GT
Linear(GT)
y=0,668x‐ 14,38
R=0,502***
‐20
‐10
0
10
20
30
40
0 102030405060
Degreeofcompactionindex(%v/v)
Soilclayfractioncontent(%)
GT
Linear(GT)
y=0,859x‐ 6,680
R=0,513***
‐20
‐10
0
10
20
30
40
0 10203040
Degreeofcompactationindex(%
v/v)
Soilsmectitecontent(%)
GT
Linear(GT)
Fig. 3 Relationships of some physical parameters with soil clay content and soil smectite
content respectively, for some vertisols from Sothern part of Romania
Victoria Mocanu et.al. / Factori şi Procese Pedogenetice din Zona Temperată 7 S. nouă (2008)107-112
112
y=0,368x+12,79
R=0,518**
0
10
20
30
40
50
0 102030405060
C
ationexchangecapacity(me/100g
soil)
Soilclayfractioncontent(%)
y=0,532x+15,53
R=0,594***
0
10
20
30
40
50
0 10203040
C
ationexchangecapacity(me/100g
soil)
Soilsmectitecontent(%)
y=0,393x+7,902
R=0,502**
0
5
10
15
20
25
30
35
40
0 102030405060
Totalexchangeablebases(me/100g
soil)
Soilclayfractioncontent(%)
y=0,617x+9,572
R=0,626***
0
5
10
15
20
25
30
35
40
0 10203040
Totalexchangeablebases(me/100g
soil)
Soilsmectitecontent(%)
Fig. 4 Relationships of chemical parameters (exchange properties) with clay content and soil
smectite content respectively, for some vertisols from Southern part of Romania.
REFERENCES
CANARACHE A., (1990) – Fizica solurilor agricole. Ed. Ceres, Bucureşti.
CRĂCIUN C., 1998, The clay minerals in vertisols of Romania. Implication in soil
physical and chemical properties. Ştiinţa Solului nr. 1-2, p. 53-61
CRĂCIUN C., LATIŞ L., DULVARA EUFROSINA, ZOTA MARILENA (1996 b) –
Influenţa mineralelor argiloase asupra unor însuşiri de bază ale solului:
Proprietăţile chimice. Analele I.C.P.A., v LII, p. 53-61.
CRĂCIUN C., 1993, Caracteristicile termice ale mineralelor smectitice. Ştiinta
Solului nr. 1-2, p. 37-57.
CRĂCIUN C., GÂŢĂ G. (1986) – Stabilirea compoziţiei mineralogice a fracţiunii
coloidale anorganice din soluri. Cap. 18 din Metode de analiză chimică a
solului, p. 392-436.