Environmental Engineering Reference
In-Depth Information
value (0.5) that can induce salt injury to rice plant. If this were simply abandoned
in the environment, tsunami deposit having a high salt concentration would dam-
age rice plants due to salt injury as the tsunami deposit was heavily mixed into
the soil.
3. The mud deposited by the tsunami contains a high concentration of sulfi de. If
tsunami-deposited mud containing large amounts of sulfi des (iron sulfi de, iron
disulfi de) is incorporated into the farmland soil, there is a possibility of acidifi ca-
tion problems occurring on upland soils due to sulfuric acid being formed as the
oxidation product of the sulfi des. For example, plow layer soil showed strongly
acidic (pH 3.8) after 5 cm of tsunami-mud was incorporated into the soil in Soma
City, northern Fukushima (Inagaki et al.
2012
). Paddy rice root injury may also
occur due to hydrogen sulfi de formed in the reduced condition.
4. Restoration methods for fi elds where the topsoil has been washed away will need
to be carried out with due care. When poor soils are dressed into the fi elds, con-
siderable time may be taken to recover good soils with high productivity.
We intend to continue the research for resolving these problems in the future
(Kitamura et al.
2012
).
18.3.2.2
Salt Tolerance Experiments with Brassicaceae Plant Crops
Lines showing strong salt tolerance were selected from among the
B. napus
and
B.
juncea
genetic resources held by the Graduate School of Agricultural Science. The
dry weight ratio after salt treatment cultivation and an index of the cumulative dry
weight ratio were used to evaluate the degree of salt tolerance. Of 38 lines of
B.
napus
examined, fi ve lines exhibited relatively strong salt tolerance, as did four
lines of the 28
B. juncea
lines examined. Excerpts from the data are shown in
Table
18.4
(Nasu et al.
2012
).
The amount of sodium absorbed from the upper layer of the soil was then deter-
mined. Regardless of the degree of the salt tolerance, the Na concentration per unit
dry-weight increased as the treated salt concentration rose. No signifi cant difference
between the lines was observed for Na concentration at equivalent salt treatment
concentrations (Table
18.5
). Nevertheless, a trend of increased Na accumulation per
plant was seen in strongly salt-tolerant lines of both
B. napus
and
B. juncea
when
compared with weakly salt-tolerant lines. Strongly salt-tolerant lines of both
B.
napus
and
B. juncea
accumulated 1.5-2 times more Na than weakly salt-tolerant
lines. This lead us to believe that a certain degree of salt-removal effect could be
expected from the strongly salt-tolerant lines.
18.3.2.3
Cultivation Trials on Salt-Damaged Farmland
In early October 2011, the growth, yields and so on of the
B. napus
and
B. juncea
that had been planted on affected wet rice fi elds (Arai, Wakabayashi Ward) and
affected upland fi elds (Sendai City Agricultural and Horticultural Center) were
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