Vivianite forms in bulk soil under reducing conditions. Vivianite may affect the P
dynamics in the plow layer soil of paddy fields (Walpersdorf et al. 2013). In a
lowland paddy field soil, the Fe o content is typically much higher than Al o . Under
oxidizing conditions, active Fe materials in the plow layer soil play a major role in
sorbing P from fertilizers. The P concentration in the soil solution increases with soil
incubation under submergence (Shiga 1973). In that previous study, although
vivianite formation was not confirmed, it is probable that the increase in P concentration was related to vivianite formation. However, the formation of vivianite
contributes to retain P in the plow layer soil of paddy fields after releasing P from
active Fe materials.
It is believed to be effective to study the factors affecting the formation and
dissolution of vivianite to control P dynamics, and to increase P efficiency, in the
plow layer soil of paddy fields. Although to date it has been difficult to artificially
extract P from paddy fields, vivianite can at least theoretically be separated from soil.
Magnets can also be used to collect vivianite aggregates from incubated paddy
field soil.
Fig. 5.20 Optical micrographs of vivianite crystal aggregates. (a) Immediately after separation
from soil incubated for 30 days at 30
C, (b) after allowing to stand for 8 h at approximately 25
C
120
5 Inorganic Soil Constituents Sensitive to Varying Redox Conditions
dynamics in the plow layer soil of paddy fields (Walpersdorf et al. 2013). In a
lowland paddy field soil, the Fe o content is typically much higher than Al o . Under
oxidizing conditions, active Fe materials in the plow layer soil play a major role in
sorbing P from fertilizers. The P concentration in the soil solution increases with soil
incubation under submergence (Shiga 1973). In that previous study, although
vivianite formation was not confirmed, it is probable that the increase in P concentration was related to vivianite formation. However, the formation of vivianite
contributes to retain P in the plow layer soil of paddy fields after releasing P from
active Fe materials.
It is believed to be effective to study the factors affecting the formation and
dissolution of vivianite to control P dynamics, and to increase P efficiency, in the
plow layer soil of paddy fields. Although to date it has been difficult to artificially
extract P from paddy fields, vivianite can at least theoretically be separated from soil.
Magnets can also be used to collect vivianite aggregates from incubated paddy
field soil.
Fig. 5.20 Optical micrographs of vivianite crystal aggregates. (a) Immediately after separation
from soil incubated for 30 days at 30
C, (b) after allowing to stand for 8 h at approximately 25
C
120
5 Inorganic Soil Constituents Sensitive to Varying Redox Conditions