Agriculture Reference
In-Depth Information
0.18
7.4
0.15
7.3
0.12
Fe(III)
pH
0.09
7.2
0.06
Fe(II)
7.1
0.03
3 days
0.00
7.0
0.18
7.4
6 days
0.15
7.3
0.12
0.09
7.2
0.06
7.1
0.03
0.00
7.0
0.18
7.4
12 days
0.15
7.3
0.12
0.09
7.2
0.06
7.1
0.03
0.00
7.0
0
2
4
6
8
10
12
Distance from root plane (mm)
Figure 6.16
As Figure 6.15 but with Maahas soil. Maahas soil is a dark humic clay,
org C
=
18%, aerobic pH
=
5
.
9, reducible Fe
=
30mmol kg
−
1
(Kirk and Bajita, 1995).
Reproduced by permission of Blackwell Publishing
Over 2 weeks of root-soil contact, Fe
2
+
close to the roots was oxidized by O
2
from the roots, and substantial quantities of iron were transferred towards the
root plane producing a well-defined zone of Fe(OH)
3
accumulation. The pH in
the oxidation zone fell. In both the soils studied, the amount of H
+
formed in
