Page 132 - Enzymes in Tropical Soils

120 Enzymes In Tropical Soils

4.1), in which ortophosphates are produced. This stimulating or hindering
phenomenon is called a Mass Action Law or Common Ion Effect. The Mass Action
Law may be used to fasten or to slow a particular reaction depending on our
interest with respect to the reaction.

8.1 Effects of Mass Action Law

The Mass Action Law is clearly shown by the chemical weathering of Albit
(Na-Feldspars) described in Eq. 8.1 as follows (Bohn et al., 1985). The weathering
of Albit will progress in moist and acid soils. The rate of the weathering increases
with the increase in soil water content and the decrease in soil pH or the increase
+
in H concentration. The importance of water and pH in the weathering of soil
minerals is in general represented by Fig. 8.1.

+
+
3+
NaAlSi 3 O 8 + 4 H 2 O + 4 H  Na + Al + 3 Si(OH) 4 ....... Eq. 8.1

120
Low Water
100 Content
Rate of Weathering 60 Content
High Water
80

40
20

0
3 4 5 6 7 8
Soil pH

Fig. 8.1. Hyphotetical effect of soil water content and pH on the rate of
Albit weathering.

Abdul Kadir Salam - 2014