Page 22 - The Chemistry and Fertility of Soils Under Tropical Weeds Book_Neat

The Chemistry and Fertility of Soils under Tropical Weeds 9

and a Mollisol from Wisconsin USA. The released Ca, Mg, K, and Zn increased with
the decrease in soil pH from 7 to 4 buffered by a resin method (Table 1.3).

3+
+
+
KAlSi 3 O 8 + 4 H 2 O + 4 H  K + Al + 3 Si(OH) 4 ....... Eq. 1.2

Table 1.2. The experimental relationships between Cd, Cu, and Zn
1)
solubilities with soil pH .

No Heavy Metal Equation

2+
1 Cd log (Cd ) = 6.50 – 2 pH
2+
2 Cu log (Cu ) = 2.80 – 2 pH
2+
3 Zn log (Zn ) = 5.80 – 2 pH
1)
Taken from Lindsay (1979), Workman and Lindsay (1990),
Ma and Lindsay (1990), El-Falaky et al. (1991)

High

Concentration

Low
Concentration

Precipitation

A B

pH

Fig. 1.6. The precipitation of heavy metal cation as a function of pH.

Abdul Kadir Salam and Nanik Sriyani – 2019