weak angular blocky (f1abk) to moderate weak angular blocky (m1abk). The moist consistence ranged from slightly friable(msfr) in the surface horizons to frim (mfi) in the subsurface horizons (Table 4-1). The selected physical attributes of the soils are presented in table 4-2. Soil texture varied at each profile and ranged from sand to clay class and sand content ranged between 2 to 85% which varies irregularly with depth.
Table 4.1 Morphological properties in the studied soil profiles
Horizon
Depth(cm)
color(moist)
structure
consistence(moist)
Boundary
Profile1
Az
0-15
5YR 3/2
C2pl
D.sH
M.sfi
w.sst
gw
Bgz
15-60
5Y 4/2
f1 abk
M.sfi
W.sst
gw
Cgz
60-110
5Y 3/3
M
M.fr
W.sst
gw
?? Bgzb
110-150
5Y 3/2
f1 abk
M.sfi
W.sst

Profile2
Az
0-20
10YR 4/3
C3pl to pr
D.H
M.fi
W.st
gw
Bg
20-60
10YR 3/2
f1 abk
M.fi
W.st
cs
Cg
60-110
10YR 3/3
s.g
M.l
W.ns
cs
?? Bgzb
110-140
10YR 3/2
f2 abk
M.sfi
W.sst

Profile3

Az
0-20
10YR 4/3
m2pl
M.sfi
W.sst
gw
Bgz
20-40
10YR 2/1
f1 abk
M.sfi
W.sst
gw
Bkgz
40-80
10YR 3/2
f1 abk
M.sfi
W.sst
gw
Cgz
80-125
10YR3/2
s.g
M.sfi
W.sst

Profile4

Az
0-20
5YR 3/2
C3pl to pr
D.sh
M.sfi
W.sst
gw
Bgz1
20-60
5Y 4/3
f1 abk
M.sfi
W.sst
gw
Bgz2
60-100
5Y 4/3
f1 abk
M.sfi
M.sst
cw
Cgz
100-130
5Y 3/2
s.g
M.l
W.sst

Profile5

A
0-10
10YR 4/3
f1 abk
D.sh
M.sfi
W.sst
gw
Bg
10-40
10YR 4/2
f1 abk
M.sfi
W.sst
cw
Czg
40-90
10YR 3/2
s.g
M.l
W.sst
cs
?? Bgzb
90-140
10YR 3/2
f2 abk
M.sfi
W.sst

Profile6

Az
0-20
10YR 3/2
C2pl
M.fr
W.sst
cw
Cgz
20-90
5YR 2.5/2
S.G
M.fi
W.st
cs
?? Bgzb
90-140
5Y 3/2
f1 abk
M.fr
W.sst

Profile7

Az
0-20
10YR 3/3
f1 abk
D.h
M.fi
W.st
gw
Bgz
20-60
10YR 3/2
f2 abk
M.fi
W.st
gw
Bkgz1
60-120
10Y 3/2
f2 abk
M.fi
W.st
gw
Bkgz2
60-160
10YR 3/1
f1 abk
M.sfi
W.sst

Symbols applied are according to Soil Survey Manual, USDA. Hand book no. 18 (2003).

Table 4.2 Physical properties of the studied soil profiles
Horizons
Depth (cm)
Sand(%)
Silt(%)
Clay(%)
Texture
Sp(%)
Profile 1
Az
0-15
32
50
18
SL,SIL
26
Bgz
15-60
21
55
24
SCL,SIL
32
Cgz
60-110
66
20
14
L,SL
27
Bgzb
110-150
72
16
12
SL,SL
21
Profile 2
Az
0-20
21
43
36
CL,CL
37
Bg
20-60
64
18
18
CL,SL
26
Cg
60-110
92
2
6
S,S
15
Bgzb
110-140
35
15
50
SCL,C
45

Profile 3

Az
0-20
14
68
18
SIL,SIL
23
Bgz
20-40
10
34
58
SL,SCL
48
Bkgz
40-80
18
50
32
SIL,SICL
38
Cgz
80-125
40
40
20
SL,L
34

Profile 4

Az
0-20
12
48
40
SICL,SICL
34
Bgz1
20-60
10
52
38
SICL,SICL
33
Bgz2
60-100
42
42
16
SL,L
21
Cgz
100-130
56
30
14
SL,SL
24

Profile 5

A
0-10
28
42
30
CL,CL
34
Bg
10-40
63
18
19
SCL,SL
17
Cz
40-90
92
2
6
S,S
15
Bgxb
90-140
42
40
18
SCL,SL
26

Profile 6

Az
0-20
64
20
16
SL,SL
22
Cgz
20-90
85
5
10
S,LS
18
Bgzb
90-140
50
34
16
SL,L
21

Profile 7

Az
0-20
26
40
34
CL,CL
29
Bgz
20-60
38
38
24
CL,L
21
Bkgz1
60-120
2
58
40
CL,SICL
37
Bkgz2
120-160
9
63
28
SICL,SL
20

4.1.1 Soil Classification and Evolution of Diagnostic Horizons
In the investigated region, known as salt-affected soils, the soils generally occur in the level to depresssional and basin type landforms under poor to somewhat poorly drained conditions. Parent materials are either calcareous alluvium or lacustrine deposits (Urmia lake), originating from saliniferous and calcareous marl deposits. They have a tendency to crust, have weak to strong platy surface structure, and support a thinner vegetative cover as compared to saline soils. Such natural properties lead to considerable variations in the morphological, physical, and chemical properties of the studied soils.
Field and laboratory data were applied to evaluated master horizons and to classy them according to Soil Taxonomy (Soil Survey Staff, 2014). Generally, the soils are in a transitional stage of development, with ochric epipedon, salic and calcic horizons along with the presence of gleying process. Thus, they are classified as Aridisols order and salids suborder except profile 6.
Salic horizons are designated with the symbol z, which refers to the pedogenic accumulation of salts more soluble than gypsum. Soils with salic horizons in the region contained a variety of structures, including granules, sub angular blocks, plates, prismatic, structure less conditions. Masses of Fe or Mn and redox features were common in the soils. In general, the water table was present at depths of 100 to 140 cm form soil surface, as indicated by redoximorphic features in their Bg and Cg horizons, for periods ranging from 1 to 12 months of the year in many of the soils. Indeed, this soil is often saturated into profiles in during the wet season, but the water table drops to about 1 m from the surface during the dry season. This is shown by dark greenish gray (5Y3/4) and brownish black (10YR3/2) mottles throughout the profile. Fine, tubular pores were common in soils with a salic horizon. Salinity is caused mainly by the anions Cl-1 and SO2 and the cations Na+, Ca+2and Mg+2. K+ and HCO3-1 were less abundant and CO3-2 was least abundant.
In the literature, topography is viewed as a very important factor leading to the development of the salic horizon, including groundwater level and salinity, slope position, proximity to the edge of playas, the presence of depressions, and the influence of flooding (Bockheim and Hartemink, 2013). In the region, the dominant processes leading to the development of saline soils were salinization and gleization with calcification occurring in some soils. The salts in soils with salic horizons in the investigated soils, the catchments of the Urmia Lake, probably originated from evaporites, groundwater seeps, and dust deposition form Urmia Lake. As a result, the main reasons for the presence of a well-developed salic horizon in the region are the occurrence of shallow water along with its high evapotranspiration and the translocation of solution salts form Urmia Lake as subsurface movements (both horizontal and lateral flows).
In profiles 3 and 7 with water table depth of about 120 cm, soils contain calcic horizons (Table 4.1). These soils are classified as Calcic Aquisalids (Table 4.3). Based on Knuteson et al. (1989) condition which favor the formation of these soils are (a) the capillary fringe from a water table approaching the root zone; (b) evapotranspiration exceeds precipitation during the summer months; and (c) bicarbonate anions dominate the composition of shallow ground water promote preservation of calcium by calcite formation.
The soil profiles of 1, 2, 5 and 6 showed the presence of evidences of a buried genetic horizon. A buried genetic horizon of these soils was characterized by the presence of (i) a surface mantle of new soil material that has more 50 cm thick and (ii) surface mantle of new material was largely unaltered, at least in the lower part (Soil Survey Staff, 2014).
In profile 6, the presence of properties such as aquic condition within 50 cm of the mineral soil surface; have less than 35 percent (by volume) rock fragments and a texture class of loamy sand in all layers within the particle-size control section; and an exchangeable sodium percentage of more 15 along with a sodium adsorption ratio of more 13 for 6 or more months in normal led to the information of Entisols order, Aquents suborder and Sodic psammaquents subgroup (Soil Survey Staff, 2014).

این مطلب رو هم توصیه می کنم بخونین:   پایان نامه رایگان با موضوع گندم و برنج

Table 4.3 Classification of the studied soil profiles (Soil Survey Staff, 2014)
USDA SOIL TAXONOMY
Profiles
ORDERS
SUBGROUP
FAMILY

Aridisols
Typic Aquisalids
Fine loamy, mixed, super active, mesic
1
Aridisols
Typic Aquisalids
Coarse loamy, over sandy, mixed, super active, mesic
2
Aridisols
Calcic Aquisalids
Coarse loamy ,mixed, super active, mesic
3
Aridisols
Typic Aquisalids
Fine loamy, mixed, super active, mesic
4
Aridisols
Typic Aquisalids
Coarse loamy, ,mixed, super active, mesic
5
Entisols
Sodic psammaquents
Sandy loamy, mixed, super active, mesic
6
Aridisols
Calcic Aquisalids
Coarse loamy, ,mixed, super active, mesic
7

In general, salt affected soils are classified into three broad classes, sodic, saline, and saline-sodic, based on pH, EC, sodium adsorption ratio, and exchangeable sodium percentage (United States Salinity Laboratory Staff, 1954).Saline soils are those that contain appreciable amounts of soluble salts so as to interfere with plant growth. These soils have high salt content, as measured by ECe, and their pH values are less than 8.5. Their saturated paste extracts contain Na+, Mg2+, and Ca2+ as the dominating cations, while Cl- and SO42- are the dominating anions. According to US Salinity Laboratory (1954), saline soils have ECe 4 dS/m, pH values 8.5, and ESP 15 (SAR 13). A typical sodic soil has high pH values (8.5), high ESP (15), and EC values less than 4 dS/m throughout the soil profile. While the anions present consist mostly of chloride, sulfate, and bicarbonate, small amounts of carbonate often occur. At high pH values and in the presence of carbonate ions, calcium and

دسته‌ها: No category

دیدگاهتان را بنویسید