further detailed study to determine the efficient application of the nitrogen fertilizer
required by specific crops. In general, these soils have a low pH (<4.4, measured
with H2O, KCL, and CaCl2). However, for wet peat, the pH value tends to be
slightly higher. The CEC values of these soils range from 66 to 192 me/100 g soil. At
the same time, they also have high extractable acidity. Therefore, most of the cation
is H
+ ion, while the large part thereof is expected to be from the RCOOH radicals.
Since the H
+ ion plays an important role to determine the CEC, these soils are
highly pH-dependent. Under the natural field conditions which are highly acidic, the
H
+ ion is usually tightly fixed with the functional group. If the soil pH increases, the
H
+ ion on the hydroxyl group will become more active and thus, increasing the CEC
values.
The exchangeable aluminum of the organic soil materials seldom exceeds 4 me/
100 g soil. It is relatively low in comparison to that of the acid sulfate soil nearby.
Thus, an increase in the soil pH by liming should be very effective in these soils. The
total bases (Ca, Mg, Na, and K) of these soils range from 3 to 18 me/100 g soil.
Table 27.1 Physical and chemical properties of the peat soils in Thailand
Properties
Peat
Substratum
Sandy
Loamy or clayey (muddy)
% moisture at saturation
245–1107
nd
nd
Hydraulic conduct (cm/sec)
0.001–0.032
nd
nd
Bulk density (gm/cc)
0.10–0.32
nd
nd
Loss on ignition (%)
85–99
nd
nd
pH 1:1 H2O
3.4–4.4
4.6–5.8
2.7–4.6
1:1 KCl2
2.3–3.4
3.6–4.6
2.7–4.4
1:1 CaCl2
2.8–3.8
3.9–4.8
2.6–3.6
Organic carbon (%)
24–80
0.3–1.0
0.9–8.6
Nitrogen (%)
0.7–1.7
0.01–0.1
0.1–0.3
CEC (me/100 g soil)
66–192
2.1–4.1
13.7–23.2
Exch. cation
Ca (me/100 g soil)
0.9–10.8
0.1–1.0
0.4–1.0
Mg (me/100 g soil)
0.6–6.7
0.1–0.9
0.6–2.7
Na (me/100 g soil)
0.3–3.4
0.2–0.9
0.3–0.9
K (me/100 g soil)
0.1–0.9
<0.1
0.1–0.2
Bass saturation (%)
by CEC
2–15
18–70
6–12
by sum of cation
2–12
10–22
3–16
Bray II-P (ppm)
18–94
7–23
9–31
Al (N-KCl soluble me/100 g soil)
0.4–9.9
0.2–2.1
2.3–7.5
Free Fe (%)
0.1–0.3
<0.1
2.3–7.5
DTPA (extractable)
Cu (ppm)
0.1–0.3
nd
nd
Zn (ppm)
0.1–2.0
nd
nd
Fe (ppm)
260–386
nd
nd
738
P. Vijarnsorn
required by specific crops. In general, these soils have a low pH (<4.4, measured
with H2O, KCL, and CaCl2). However, for wet peat, the pH value tends to be
slightly higher. The CEC values of these soils range from 66 to 192 me/100 g soil. At
the same time, they also have high extractable acidity. Therefore, most of the cation
is H
+ ion, while the large part thereof is expected to be from the RCOOH radicals.
Since the H
+ ion plays an important role to determine the CEC, these soils are
highly pH-dependent. Under the natural field conditions which are highly acidic, the
H
+ ion is usually tightly fixed with the functional group. If the soil pH increases, the
H
+ ion on the hydroxyl group will become more active and thus, increasing the CEC
values.
The exchangeable aluminum of the organic soil materials seldom exceeds 4 me/
100 g soil. It is relatively low in comparison to that of the acid sulfate soil nearby.
Thus, an increase in the soil pH by liming should be very effective in these soils. The
total bases (Ca, Mg, Na, and K) of these soils range from 3 to 18 me/100 g soil.
Table 27.1 Physical and chemical properties of the peat soils in Thailand
Properties
Peat
Substratum
Sandy
Loamy or clayey (muddy)
% moisture at saturation
245–1107
nd
nd
Hydraulic conduct (cm/sec)
0.001–0.032
nd
nd
Bulk density (gm/cc)
0.10–0.32
nd
nd
Loss on ignition (%)
85–99
nd
nd
pH 1:1 H2O
3.4–4.4
4.6–5.8
2.7–4.6
1:1 KCl2
2.3–3.4
3.6–4.6
2.7–4.4
1:1 CaCl2
2.8–3.8
3.9–4.8
2.6–3.6
Organic carbon (%)
24–80
0.3–1.0
0.9–8.6
Nitrogen (%)
0.7–1.7
0.01–0.1
0.1–0.3
CEC (me/100 g soil)
66–192
2.1–4.1
13.7–23.2
Exch. cation
Ca (me/100 g soil)
0.9–10.8
0.1–1.0
0.4–1.0
Mg (me/100 g soil)
0.6–6.7
0.1–0.9
0.6–2.7
Na (me/100 g soil)
0.3–3.4
0.2–0.9
0.3–0.9
K (me/100 g soil)
0.1–0.9
<0.1
0.1–0.2
Bass saturation (%)
by CEC
2–15
18–70
6–12
by sum of cation
2–12
10–22
3–16
Bray II-P (ppm)
18–94
7–23
9–31
Al (N-KCl soluble me/100 g soil)
0.4–9.9
0.2–2.1
2.3–7.5
Free Fe (%)
0.1–0.3
<0.1
2.3–7.5
DTPA (extractable)
Cu (ppm)
0.1–0.3
nd
nd
Zn (ppm)
0.1–2.0
nd
nd
Fe (ppm)
260–386
nd
nd
738
P. Vijarnsorn