Page 18 - Ilmu Tanah

The Chemistry and Fertility of Soils under Tropical Weeds 5

relatively toxic. In this form, Fe may also not move through mass flow, diffusion, as
well as leaching by water. Lowering the soil pH through acidification may reverse
2+
the Fe to Fe with its characteristics mentioned previously.

Plants

Adsorbed

Complexes Free Fe Ions Chelates
Fe  Fe
3+
2+
(Redox)

Precipitates Leaching

Ground-Water: Rivers, Seas:

Contamination Contamination
Pollution Pollution

2+ 3+
Fig. 1.2. The fates of Fe or Fe in the soil system
(Adapted from Salam, 2017).

In wetland soils where the soil condition is reductive with low redox potential,
3+
2+
Fe may exist as Fe . This Fe species in some respect is similar to Fe . This form
shows high reactivity and mobility in soils. Therefore, the fate of this Fe species is
2+
3+
similar to that of Fe as depicted in Fig. 1.2. The Fe ion may participate in
adsorption/desorption reaction through cation exchange processes (Fig. 1.2), may
precipitate as Fe(OH) 2 as the soil pH increases (Fig. 1.1, Fig. 1.2, Fig. 1.3), may move
in the soil body through mass flow, diffusion, or water leaching (Fig. 1.2), and be
chelated and absorbed by plants (Fig. 1.2).

Abdul Kadir Salam and Nanik Sriyani – 2019