) which can be explained by discharge from a shallow water table, which have precipitated as secondary carbonates in the topsoil due to evapotranspiration and precipitation from upper horizons (Knuteson et al. 1989; Abtahi and Khormali 2001).
CEC is used as an overall assessment of the potential fertility of a soil and to assess the possible response to fertilizer application (Brady and Weil 1999). In accordance with the soil texture and the low organic matter content, the CEC of the soils were classified into low to medium (Table 4.5). The CEC varied between 6 to 27 cmol kg-1 and its was highest was in the A-horizon of profile 4 and B-horizon of profile 3 where the highest values of clay and organic matter were occurred, suggested that CEC is related considerably to clay and SOC values. This investigation is in agreement with other researchers (Rezapour and Samadi, 2012). Ca was the dominant cation in the exchangeable complex, followed by Mg or Na in the majority of the soils. For most of the soil profiles, exchangeable cations (Ca, Mg, Na, K) in surface soils were higher than those of the subsurface soils.
The content of Olsen- P ranged from 0.8 mg kg-1 (B-horizon of profile 7) to 21.0 mg kg-1 (A-horizon of profile 3) and decreased with depth in all soils (except profile1). Presently, the accepted critical level of Oslen- P in calcareous soils of Western Azerbaijan Province is 15 mg kg-1 soil (Malakouti and Gheibi 2000). Therefore, available P concentrations were lower than this level (expect upper horizons of profile 3). The concentration of available K varied between 30 mg kg-1 (B-horizon of profile 2) to 825 mg kg-1 (A-horizon of profile 3) and decreased with depth in all soils. In the majority of the soils, the values of available K mainly in surface horizons were higher than the accepted critical level of available K in the Iran soils (Malakouti and Gheibi 2000).

Table 4.5: The chemical and fertility properties of the studied profiles
Horizon
Depth (cm)
OC
CCE
Pava
Kava
Na
K
Ca
Mg
CEC

%
mg/kg
cmol (+)/kg
Profile 1
Az
0-15
0.35
2.25
5.05
172.37
3.25
0.55
8.75
2.00 12.56
Bgz
15-60
0.13
3.25
6.93
101.02
2.33
0.53
10.50
2.00 13.64
Cgz
60-110
0.07
13.5


1.90
0.34
8.50
3.00 11.38
Bgzb
110-150
0.07
12.5


1.82
0.29
6.00
3.50 10.53

Profile 2

Az
0-20
0.91
12.75
2.81
304.89
5.19
1.27
9.00
3.50 19.00
Bg
20-60
0.09
13.25
2.09
29.66
1.76
0.40
8.00
1.20 10.69
Cg
60-110
0.04
12.75


0.86
0.20
1.75
1.00 5.90
Bgzb
110-140
0.09
9


2.79
1.14
3.50
1.50 18.32

Profile 3

Az
0-20
1.02
18.25
21.3
824.77
1.75
2.61
4.25
3.00 15.18
Bgz
20-40
1.00
11.25
14.3
651.48
6.98
2.11
10.00
4.80 25.66
Bkgz
40-80
0.32
19


3.00
0.98
3.00
5.00 14.90
Cgz
80-125
0.30
16


4.16
0.61
3.25
2.25 12.04

Profile 4

Az
0-20
0.52
15.25
7.22
794.19
4.38
3.20
9.00
6.00 21.62
Bgz1
20-60
0.32
14.5
5.92
620.9
3.93
1.90
8.00
4.50 17.30
Bgz2
60-100
0.24
13.75


3.90
0.67
3.75
1.5 12.48
Cgz
100-130
0.11
12.75


3.89
0.55
3.75
1.25 11.56

Profile 5

A
0-10
0.76
16.25
10.64
478.18
1.61
0.41
8.50
0.75 16.05
Bg
10-40
0.3
13.5
1.14
70.44
1.60
0.35
3.75
0.25 9.23
Cz
40-90
0.19
11


1.36
0.14
2.50
2.50 6.34
Bgzb
90-140
0.33
19.25


3.04
0.39
5.25
0.50 11.76

Profile 6

Az
0-20
0.3
11.5
5.36
141.79
1.69
0.36
8.00
2.00 10.27
Cgz
20-90
0.20
10.75
2.21
39.86
2.15
0.26
6.50
2.50 7.69
Bgzb
90-140
0.39
13.5


0.96
0.37
6.50
4.50 10.88

Profile 7

Az
0-20
0.76
11.5
5.29
580.12
1.71
1.97
9.00
5.00 19.59
Bgz
20-60
0.32
15
0.81
101.02
1.37
0.48
9.50
3.00 12.89
Bkgz1
60-120
0.43
13.25


1.34
0.60
9.00
5.00 20.59
Bkgz2
120-160
0.41
13.5


1.53
0.38
11.50
6.00 16.17

4.3 Assessment of Pattern and Distribution of Iron Oxides Forms
In general, the soils indicated some differences in the value of iron oxides and their vertical distribution within the profiles (Table 4.6) that might related to degree of weathering, pedogenic accumulation, seasonal fluctuations in water table, and repeated cycles of sediment accumulation. Tite and Linington (1975) have suggested that environmental conditions such as: distinct wetting-drying cycles and associated alternation among reduction-oxidation provide the best conditions for the pedogenic formation of iron oxides in Mediterranean climates such as those of the soils being studied. The values of Fed (Free or pedogenic Fe oxides) in these soils were commonly quite low, ranging between 3 and 12 g kg-1, reflecting low weathering of primary Fe-bearing minerals and formation of Fe oxides. Similar results have been reported for soils with Mediterranean climate (Singer 1977; Pena and Torrent 1984). The vertical distribution of Fed, attributed to crystalline, poorly crystalline and organically bound Fe, indicated an increasing trend towards the lower horizons and the largest amount of Fed was associated with B horizons in the majority of the soils. This pattern may be explained in two mechanisms: the fist interpretation is related to the high rate of in situ weathering, as results of wetting-drying cycle and great presence of micaceous minerals and chlorite in the soils (as will see in the next section). The presence of high rate of mica (illite) and chlorite along with parallel increase of Fed in the soils suggests that the large amount of Fed may be released from micaceous chlorite minerals by weathering. Aniku and Singer (1990) indicated that high Fed value was as a result of the progressive transformation of silicate-bound Fe into Fe oxides. Rezapour et al. (2010) reported a similar result in the calcareous soils from Urmia region, north-west of Iran. According to the second interpretation, the accumulation of Fed in subsurface horizons can be attributed to migration of iron oxides coated clay from upper to lower horizons. The determination of association of Fed with translocation of clay fraction was calculated by the Fed/clay ratio (Birkeland 1999).
Table 4.6 Iron oxides forms in the studied soil profiles
Horizon
Depth (cm)
Feo
Fed
Feo/Fed
Fed-Feo
Fed/clay

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mg/kg

Profile1

Az
0-15
3816
6953
0.5488
3137
0.39
Bgz
15-60
3636
7606
0.4780
3970
0.32
Cgz
60-110
3684
6697
0.5500
3013
0.48
Bgzb
110-150
3120
6016
0.5186
2896
0.50

Profile2

Az
0-20
4158
6570
1.580
2412
0.18
Bg
20-60
1794
5536
0.3240
3742
0.31
Cg
60-110
1662
5451
0.3048
3789
0.91
Bgzb
110-140
3134
6306
0.4969
3172
0.13

Profile3

Az
0-20
2172
2251
0.9649
79
0.13
Bgz
20-40
2256
3475
0.6492
1219
0.10
Bkgz
40-80
2376
4999
0.4752
2623
0.16
Cgz
80-125
2676
6976
0.3836
4300
0.35

Profile4

Az
0-20
3084
4216
0.7314
1132
0.11
Bgz1
20-60
3330
6021
0.5530
2691
0.16
Bgz2
60-100
2166
4545
0.4765
2379
0.28
Cgz
100-130
2466
3603
0.6844
1137
0.26

Profile5

A
0-10
4062
5470
0.7425
1408
0.18
Bg
10-40
1590
5323
0.2987
3733
0.28
Cz
40-90
2544
4736
0.5371
2192
0.79
Bgzb
90-140
2010
4173
0.4816
2163
0.23

Profile6

Az
0-20
1512
5604
0.2698
4092
0.35
Cgz
20-90
996
5631
0.1768
4635
0.56
Bgzb
90-140
2394
6335
0.3779
3941
0.40

Profile7

Az
0-20
1392
5620
0.2476
4228
0.17
Bgz
20-60
984
6398
0.1537
5414
0.27
Bkgz1
60-120
3060
9656
0.3169
6596
0.24
Bkgz2
120-160
3036
8965
0.3386
5929
0.32

This ratio increased from soil surface to lower solum in most of the profiles (Table 4.6). Accordingly, the high proportion of Fed is independent with clay fraction; therefore, most of its content is as product of in situ pedogenic processes and seems not necessarily to be the redeposition of clay with Fed. Additionally, lack of evidence of clay movement within the profiles along with weak relationship of Fed and clay (Fig. 4.8 ) supports this assessment. Within the soil profiles with more restricted drainage, exhibiting typically Fe depletion processes with repeated cycles of wet and dry as distinctive grey zones and mottles in subsoil (profiles of 1, 4,5 and 7), B horizon had higher concentration of Fed as well as greater part of Fe oxides in the crystalline (Fecryst.).

Fig. 4.8 A plot of Fed versus clay in the studied soils

Poorly crystalline Fe oxides that often called non-crystalline, poorly ordered, short-range-order and active or amorphous iron oxides showed a considerable variation among the soil profiles. This behavior might be explained by seasonal fluctuations in water table and moisture within soils along with variation in soil organic matter. The vertical distribution pattern of oxalate extractable Fe (Feo), ranging from 984 mg/kg (B-horizon of profile 7) to 4158 mg/kg (A-horizon of profile 2), showed a decreasing trend with depth in the most of the soil profiles (Table 4.8). In the profiles of 1, 2, and 5, the content of Feo was in the high rate in the A horizon where soil organic matter also presented in the maximum rate. This pattern may be due to two processes: First, influence of some soil

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