rates during the cultivation period decreased by 30–91%
when pellets of nitrogen-enriched manure composts
(nitrogen-enriched MCPs) were applied to soils, compared
with emission rates with the application of ordinary MCPs
(non-nitrogen-enriched). The nitrogen-enriched manure
composts were made by blowing the ammonia emitted
during the composting process into matured composts
(Tanaka 2009). It is important to clarify the mechanism of
the decreased N 2 O emissions in such MCPs in order to
develop techniques for decreasing N 2 O emissions from
ordinary MCPs, which is a future challenge.
10.4.4 Heavy Metal Contamination
Mining and refining activities can cause serious heavy metal
contamination to soil in localized areas. Examples include
the arsenic (As) pollution that occurred in Toroku, a small
mountain village in Miyazaki Prefecture, Kyushu. At the
Toroku mine, As-bearing ores had been mined and smelted
until 1962. The smelting plant was very poor and primitive,
lacking a dust-collecting system. As a result, effluent gases
containing arsenic trioxide leaked from the smelter and
diffused throughout the entire Toroku region. Additionally,
slag containing As was thrown into the Toroku River, which
flows through the Toroku region, and polluted the river
water. The As-contaminated river water was then used as
domestic and irrigation water. Consequently, the environment of Toroku and its surrounding areas were completely
polluted with As. Many residents living these areas developed chronic As poisoning, and a large number of them
died. The agricultural soils along the Toroku River were also
severely contaminated with As. The growth of crops,
including paddy rice, was severely suppressed due to As
toxicity, and the yields decreased remarkably. The As concentrations in the paddy (seven sites) and upland (one site)
soils of the Toroku region reached an average of 274 mg
kg
−1
(range: 44.2–424 mg kg
−1 ) and 1302 mg kg
−1 ,
respectively, according to a soil survey in 1970–1971
(Miyazaki Prefecture 1972). In the paddy soils approximately 50 km downstream from the Toroku mine, the As
concentrations were 228 and 635 mg kg
−1 (Saito 1964). In
1973, the Japanese government officially recognized the area
as a “polluted area by As” and undertook soil restoration of
the contaminated agricultural fields.
Soil capping (i.e., the capping of contaminated soils with
uncontaminated soils brought from another place) has been
generally used as a method for the restoration of
As-contaminated paddy soils in Japan. Upon planning the
soil restoration project of the Toroku region, examinations of
capping materials and their thickness were conducted to
achieve an appropriate remediation effect. The examinations
were carried out on lysimeter fields (area of 1 m  0.95 m)
filled with As-contaminated soil for three years. The study
found that capping with over 7.5 cm of Andosol from
neighboring areas could prevent the As toxicity from
inhibiting the growth of paddy rice and reduce the As concentration of soil at 0–15 cm depth to less than 15 mg kg
−1
As extracted 1.0 mol L
−1 HCl (Miyazaki Agricultural
Research Institute 1977). The soil restoration project was
completed in 1983, and monitoring and assessment has been
continuously performed there since.
In Kyushu, the greenhouse cultivation of fruit vegetables
has flourished since the 1970s as a result of farmers taking
advantage of the warm climate in winter. Recently, it has
become clear that the concentration of heavy metals, e.g.,
cadmium (Cd), chrome (Cr), copper (Cu), and zinc (Zn), in
the soils of these greenhouse fields has been slowly
increasing (Akagi and Chishaki 2015). The concentrations of
total (hot HNO 3 –HClO 4 extractable) and water-extractable
Cd, Cr, Cu, and Zn in the soils collected from 23 greenhouse
field sites and from 11 sites of adjacent non-agricultural field
are shown in Fig. 10.15. The concentrations of total and
water-extractable Cd in the greenhouse field soils ranged
from 82.4 to 438 µg kg
−1 (median: 293 µg kg
−1 ) and from
0.520 to 2.97 µg kg
−1 (median: 1.75 µg kg
−1 ), respectively.
These Cd concentrations were approximately three times
higher than those in the adjacent non-agricultural field soils.
Similarly, the concentrations of Cr, Cu, and Zn in the
greenhouse field soils were significantly higher than those in
the adjacent non-agricultural field soils. These heavy metal
concentrations were strongly related to the concentration of
total phosphate in the soils (Fig. 10.16), which indicates that
there was a link between phosphate fertilizer use and an
increase of Cd, Cr, Cu, and Zn concentrations. Additionally,
the livestock manure used in Japan also contains small
amounts of Cu and Zn. Therefore, if a large amount of
livestock manure is used continuously, it may also contribute
a source of Cu and Zn to the soil. The increase in the concentration of toxic heavy metals, including Cd, in agricultural soils is undesirable for sustainably producing safe food.
In order to avoid the ineffectual application of phosphate
fertilizer, which can cause an increase in heavy metal concentration in soils, soil researchers in Kyushu are working to
make a new improved fertilizer application guideline considering the phosphate fertility levels of soils today.
354
Y. Arakawa et al.
when pellets of nitrogen-enriched manure composts
(nitrogen-enriched MCPs) were applied to soils, compared
with emission rates with the application of ordinary MCPs
(non-nitrogen-enriched). The nitrogen-enriched manure
composts were made by blowing the ammonia emitted
during the composting process into matured composts
(Tanaka 2009). It is important to clarify the mechanism of
the decreased N 2 O emissions in such MCPs in order to
develop techniques for decreasing N 2 O emissions from
ordinary MCPs, which is a future challenge.
10.4.4 Heavy Metal Contamination
Mining and refining activities can cause serious heavy metal
contamination to soil in localized areas. Examples include
the arsenic (As) pollution that occurred in Toroku, a small
mountain village in Miyazaki Prefecture, Kyushu. At the
Toroku mine, As-bearing ores had been mined and smelted
until 1962. The smelting plant was very poor and primitive,
lacking a dust-collecting system. As a result, effluent gases
containing arsenic trioxide leaked from the smelter and
diffused throughout the entire Toroku region. Additionally,
slag containing As was thrown into the Toroku River, which
flows through the Toroku region, and polluted the river
water. The As-contaminated river water was then used as
domestic and irrigation water. Consequently, the environment of Toroku and its surrounding areas were completely
polluted with As. Many residents living these areas developed chronic As poisoning, and a large number of them
died. The agricultural soils along the Toroku River were also
severely contaminated with As. The growth of crops,
including paddy rice, was severely suppressed due to As
toxicity, and the yields decreased remarkably. The As concentrations in the paddy (seven sites) and upland (one site)
soils of the Toroku region reached an average of 274 mg
kg
−1
(range: 44.2–424 mg kg
−1 ) and 1302 mg kg
−1 ,
respectively, according to a soil survey in 1970–1971
(Miyazaki Prefecture 1972). In the paddy soils approximately 50 km downstream from the Toroku mine, the As
concentrations were 228 and 635 mg kg
−1 (Saito 1964). In
1973, the Japanese government officially recognized the area
as a “polluted area by As” and undertook soil restoration of
the contaminated agricultural fields.
Soil capping (i.e., the capping of contaminated soils with
uncontaminated soils brought from another place) has been
generally used as a method for the restoration of
As-contaminated paddy soils in Japan. Upon planning the
soil restoration project of the Toroku region, examinations of
capping materials and their thickness were conducted to
achieve an appropriate remediation effect. The examinations
were carried out on lysimeter fields (area of 1 m  0.95 m)
filled with As-contaminated soil for three years. The study
found that capping with over 7.5 cm of Andosol from
neighboring areas could prevent the As toxicity from
inhibiting the growth of paddy rice and reduce the As concentration of soil at 0–15 cm depth to less than 15 mg kg
−1
As extracted 1.0 mol L
−1 HCl (Miyazaki Agricultural
Research Institute 1977). The soil restoration project was
completed in 1983, and monitoring and assessment has been
continuously performed there since.
In Kyushu, the greenhouse cultivation of fruit vegetables
has flourished since the 1970s as a result of farmers taking
advantage of the warm climate in winter. Recently, it has
become clear that the concentration of heavy metals, e.g.,
cadmium (Cd), chrome (Cr), copper (Cu), and zinc (Zn), in
the soils of these greenhouse fields has been slowly
increasing (Akagi and Chishaki 2015). The concentrations of
total (hot HNO 3 –HClO 4 extractable) and water-extractable
Cd, Cr, Cu, and Zn in the soils collected from 23 greenhouse
field sites and from 11 sites of adjacent non-agricultural field
are shown in Fig. 10.15. The concentrations of total and
water-extractable Cd in the greenhouse field soils ranged
from 82.4 to 438 µg kg
−1 (median: 293 µg kg
−1 ) and from
0.520 to 2.97 µg kg
−1 (median: 1.75 µg kg
−1 ), respectively.
These Cd concentrations were approximately three times
higher than those in the adjacent non-agricultural field soils.
Similarly, the concentrations of Cr, Cu, and Zn in the
greenhouse field soils were significantly higher than those in
the adjacent non-agricultural field soils. These heavy metal
concentrations were strongly related to the concentration of
total phosphate in the soils (Fig. 10.16), which indicates that
there was a link between phosphate fertilizer use and an
increase of Cd, Cr, Cu, and Zn concentrations. Additionally,
the livestock manure used in Japan also contains small
amounts of Cu and Zn. Therefore, if a large amount of
livestock manure is used continuously, it may also contribute
a source of Cu and Zn to the soil. The increase in the concentration of toxic heavy metals, including Cd, in agricultural soils is undesirable for sustainably producing safe food.
In order to avoid the ineffectual application of phosphate
fertilizer, which can cause an increase in heavy metal concentration in soils, soil researchers in Kyushu are working to
make a new improved fertilizer application guideline considering the phosphate fertility levels of soils today.
354
Y. Arakawa et al.