Agriculture Reference
In-Depth Information
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Distance from root surface (mm)
Figure 6.17
Calculated pH profiles around a rice root exporting acid into anaerobic soil
at different initial pHs. Other parameter values: H
+
flux across root
2.5 nmol dm
−
2
s
−
1
,
root radius
=
0
.
2mm, pH buffer power
=
0
.
05mol dm
−
3
pH
−
1
,CO
2
pressure
=
1kPa,
θ
L
=
0
.
7,
f
L
=
0
.
4, time
=
12 days (after Nye, 1981)
=
0.00
initial p
H
flux
of H
+
−
0.25
pH buffer
power
−
0.50
−
0.75
−
1.00
CO
2
pressure
−
1.25
−
1.50
6.0
6.5
7.0
7.5
initial pH
0.00
0.02
0.04
0.06
0.08
0.10
pH buffer power (mol kg
−
1
pH
−
1
)
0.0
0.5
1.0
1.5
2.0
CO
2
pressure (kPa)
0
1
2
3
4
5
flux of H
+
across root (nmol dm
−
2
s
−
1
)
Figure 6.18
Sensitivity of pH change at root surface to important variables, varied indi-
vidually. Standard values as in Figure 6.17 with initial pH
=
6
.
75
