Page 134 - Ilmu Tanah Book

The Chemistry and Fertility of Soils under Tropical Weeds 121

than K, the weathering process will continue. This condition is mathematically
expressed as follow:

+
[ ] [ 3+ ] ⌈ ( ) 4 ⌉
If > , the weathering process occurs and continues. On the
+
[ ] 4
+
[ ] [ 3+ ] ⌈ ( ) 4 ⌉
other hand, if < , the weathering process does not occur.
+
[ ] 4
Using this logic, the weathering process can be accelerated or inhibited.
Considering the chemical weathering in Fig. 7.1, the weathering of orthoclase can
be accelerated by:

1. increasing the soil moisture
2. lowering the soil pH
+
3. decreasing the concentration of K in soil solution,
3+
4. decreasing the concentration of Al in soil solution, and/or
5. decreasing the concentration of Si(OH) 4 in soil solution.

On the other hand, if the weathering process is to be inhibited, the following
actions can be taken::

1. decreasing the soil moisture,
2. increasing the soil pH,
+
3. increasing the concentration of K in soil solution,
3+
4. increasing the concentration of Al in soil solution, and/or
5. increasing the concentration of Si(OH) 4 in soil solution.

Salam (2019) suggests that in general this logic is possibly used to manage the
chemical weathering of minerals in the soil environment. Increasing the
concentrations of reactants may probably increase the rate of chemical weathering
in the soil environment; likewise, decreasing the concentrations of reaction
products may probably increase the rate of the chemical weathering. For example,
+
increasing the concentration of H or decreasing the soil pH is the most interesting.
+
As the reactant in most cases, H may act as an attacking agent and therefore may
accelerate the rate of chemical weathering. Some research results are summarized
as those depicted in Fig. 7.3.
The weathering process on soil minerals is initiated by the substitution of Na,
+
K, Ca, and Mg by H ions in the mineral structure. In the process, hydrogen ions are
consumed and then the structural cations are released into the soil solution. In the
+ +
weathering of mica, H ions from the soil solution may displace K in the mica
Abdul Kadir Salam and Nanik Sriyani – 2019