In tropical peatlands of the maritime continent boundary in Southeast Asia, water
is supplied mainly from rain (Fig. 1.12). Along the maritime continent boundary, sea
water evaporation brings water in cloud form to the land, which means that this rain
contains extremely low amounts of nutrients, similar to distilled water.
Soil Clays
Permanent charge
Soil Organic
Matter (SOM):
Variable charge
(pH-depended)
Cation Retention on Clays and Organic Matter
Na +
K +
Mg 2+
Ca 2+
NH 4+
COO
Na +
K +
NH 4+
Na +
K +
Mg 2+
Ca 2+
NH 4+
COO H +
Na +
K +
NH 4+
CEC(pH7) CEC(pH4)
CEC(pH7) > CEC(pH4)
Desorption
pH7
pH4
Adsorption
*Tropical Peat: pH3.0~3.5
Mg 2+
Mg 2+
Fig. 1.11 Cation leaching mechanisms by cation desorption in peat (organic soil) at low pH (less
than 4.0). Based on Andriesse (1988) and Sumner and Miller (1996)
Fig. 1.12 Water and nutrient supply system for the peatland
20
M. Osaki et al.