Environmental Engineering Reference
In-Depth Information
plants and the experimental production of solid candles and soap from rapeseed oil
was also carried out.
Considering the results of this project, the following activities have been planned.
It is thought that these activities will be carried out over about the next 10 years:
1. To analyze the mechanisms and genes involved in the breeding of salt-tolerant
Brassicaceae plants.
2. To establish methods for the stable production of Brassicaceae plants and a cul-
tivation system for soil improvement in the affected farmlands.
3. To establish sales methods for rapeseed oil as BDF and edible oil.
4. To construct a local-production-for-local-consumption energy system for BDF
production and so on from rapeseed oil.
18.3.2
Synopsis of the Specifi c Project Activities
18.3.2.1
Soil Surveys of the Farmland Affected by the Tsunami
From March 2011, immediately after the earthquake disaster, a detailed and wide-
ranging soil survey covering the entire 14,300 ha of tsunami-affected farmland in
Miyagi Prefecture was carried out in coordination with Miyagi Prefectural research
institutes, the agricultural technology extension offi ce, farmer's cooperative staff
and other partners. Three hundred and forty four locations were selected for the
survey (Nanzyo
2013
). There were signifi cant differences in the damage from
region to region. In some places, the soil surface had been covered to a depth of
10 cm by a tsunami deposit consisting of mud (Fig.
18.5
), while in others the plow
layer was covered in a thick deposit of sand. In other places, the topsoil had been
washed away, making a revival of agriculture impossible without soil dressing.
There were places where the land had simply been immersed in seawater and could
not be recovered without salt removal. There were also places where the windbreak
forest had been uprooted and the roof tiles of houses had been scattered over the
land. It was clear that the farmland restoration method would differ according to the
type of damage found in each area. Soil analyses were performed in detail with
reference to the vertical distribution of salt. Salt removal projects have been carried
out during the 2 years thus far, but it has been confi rmed that the following issues
still remain (Ito
2013
; Ito and Kanno
2012
).
1 . I n fi elds where salt removal has been completed, sodium adsorbed by the soil
particles still remains and the concentration of bioavailable calcium is reduced
(Fig.
18.6
).
2. The mud deposited by the tsunami contains a high concentration of salt.
According to our research on tsunami-muds distributed in northern part of
Miyagi prefecture (Shima et al.
2012
), they showed the electric conductivity of
3.5-24.9 as the averaged values of the three areas, measured by water to mud
ratio of 5. The values of electric conductivity are very high compared to the critical
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