Kochi Prefecture, located in the south, rice used to be
cropped twice a year by making use of the warm climate.
However, due to the “gentan” rice control policy described
in Chap. 1, rice is now mono-cropped by early planting,
which enables early harvesting in the beginning of August.
In the inland mountainous areas, on the other hand, the
climate is usually colder and wetter than in the floodplains.
Here, rice is often grown in Tanada terraced fields (see
Sect. 9.2.1) with a slope of 1:20 or greater. Many of these
terraced fields are located in the Chugoku region, and
especially in Hiroshima Prefecture, where the area of terraced field amounts to 43% and 26% of the total area of
terraced field in Japan, respectively (Ministry of Agriculture,
Forestry and Fisheries 2017f).
In the Kinki, Chugoku, and Shikoku regions, the percentage of the area of paddy fields under the gentan policy
is more than 20% in Tottori and Kochi Prefectures, about
9% in Wakayama Prefecture, and 10–20% in other prefectures (Board of Audit of Japan 2016). In all prefectures,
the production of staple rice has been controlled by rotating
it with other crops such as vegetables, wheat or barley
(mugi), and soybean—for example, three croppings of rice,
wheat, and soybean in a two-year rotation. In recent years,
more farmers have started to grow non-staple rice, such as
rice for the production of food and drink items such as
Japanese rice wine (sake), rice crackers, miso paste, and soy
sauce, and also rice for feeding domestic animals such as
unhulled rice for pigs and chickens and whole-crop silage
for cows.
The type and properties of paddy soils in the Kinki,
Chugoku, and Shikoku regions are described briefly. The
average soil characteristics in each prefecture are summarized in Table 9.4. According to a national survey from
1959 to 1978, a large regional variation existed in the distribution of Gley Fluvic soils in paddy fields. For example,
in Kagawa Prefecture, only 3% of the paddy soil was
classified as Gley Fluvic soils, whereas that figure was more
than 50% in Shimane and Shiga Prefectures. Gley Fluvic
soils are formed in wet paddy fields where the water table is
high and soil is clayey and impermeable. It is important
even now to improve the field permeability by introducing
open ditches and underground drainage especially when rice
is rotated with upland crops. According to a more recent
national survey from 1999 to 2003 (Ministry of Agriculture,
Forestry and Fisheries Agricultural Production Bureau
2008), the surface paddy soils in the Kinki, Chugoku, and
Shikoku regions showed lower values of total C and cation
exchange capacity than those in other regions of Japan.
Within these regions, the soil contents of exchangeable K
and available P tended to be higher in Kyoto and Kagawa
Prefectures.
9.2.3 Upland Fields
In the Kansai region (which includes the Kinki, Chugoku,
and Shikoku regions), wheat varieties, beans, and millets are
grown mainly in paddy fields utilized for double cropping or
paddy–upland rotation, or in dedicated crop fields converted
from paddy fields, thus providing production on diverse
farmlands adapted to local climatic and soil conditions. In
mountainous areas in the Shikoku region, crops are cultivated in small plots located on sloping lands.
1. Crop cultivation based on the fields originally used as
paddy (wheat varieties, beans, and millets)
To cultivate crops susceptible to moisture damage, such as
cereals, beans, and buckwheat (Fagopyrum esculentum), it is
of utmost importance to improve the drainage of farmland.
Depending on the climatic, topographic, and soil conditions,
various efforts are being made for enhanced drainage,
including the construction of open ditches, underdrains, and
mole drains (Fig. 9.4).
(1) Paddy–upland rotation for wheat and soybean
(Shiga Prefecture: Fluvic Paddy soils, etc.)
In Shiga Prefecture, where paddy fields account for as much
as 92% of all farmland, many farmers adopt a three-year
four-crop rotation of rice (summer harvest) to rice (summer
harvest) to wheat (winter harvest) to soybean (summer harvest) (Kitagawa 2012). For the cultivation of wheat and
soybean, Fluvic Paddy soils, Gray Fluvic soils, and Gley
Fluvic soils distributed along rivers around Lake Biwa are
used, with various measures being taken combining the use
of open ditches, underdrains, and mole drains for improving
the quantity and quality of production (Shiga Prefecture
2012).
(2) Soybean production (Hyogo Prefecture, Okayama
Prefecture: Gray Fluvic soils, Brown Fluvic soils)
In Hyogo Prefecture, soybean (Glycine max), including
large-grain black soybeans, are cultivated, mainly in Gray
Fluvic soils. Soybean is susceptible to humidity damage,
especially after seeding. Therefore, open ditches, underdrains, and radial-shaped mole drains have been constructed
to improve drainage. In Okayama Prefecture, large-grain
black soybean is cultivated mainly in Brown Fluvic soils. In
recent years, instances of decreased soybean harvest have
been reported, indicating a decline in soil fertility. In this
region, as in many other regions, a higher frequency of black
soybean cultivation has been shown to be correlated with
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J. Yanai et al.
cropped twice a year by making use of the warm climate.
However, due to the “gentan” rice control policy described
in Chap. 1, rice is now mono-cropped by early planting,
which enables early harvesting in the beginning of August.
In the inland mountainous areas, on the other hand, the
climate is usually colder and wetter than in the floodplains.
Here, rice is often grown in Tanada terraced fields (see
Sect. 9.2.1) with a slope of 1:20 or greater. Many of these
terraced fields are located in the Chugoku region, and
especially in Hiroshima Prefecture, where the area of terraced field amounts to 43% and 26% of the total area of
terraced field in Japan, respectively (Ministry of Agriculture,
Forestry and Fisheries 2017f).
In the Kinki, Chugoku, and Shikoku regions, the percentage of the area of paddy fields under the gentan policy
is more than 20% in Tottori and Kochi Prefectures, about
9% in Wakayama Prefecture, and 10–20% in other prefectures (Board of Audit of Japan 2016). In all prefectures,
the production of staple rice has been controlled by rotating
it with other crops such as vegetables, wheat or barley
(mugi), and soybean—for example, three croppings of rice,
wheat, and soybean in a two-year rotation. In recent years,
more farmers have started to grow non-staple rice, such as
rice for the production of food and drink items such as
Japanese rice wine (sake), rice crackers, miso paste, and soy
sauce, and also rice for feeding domestic animals such as
unhulled rice for pigs and chickens and whole-crop silage
for cows.
The type and properties of paddy soils in the Kinki,
Chugoku, and Shikoku regions are described briefly. The
average soil characteristics in each prefecture are summarized in Table 9.4. According to a national survey from
1959 to 1978, a large regional variation existed in the distribution of Gley Fluvic soils in paddy fields. For example,
in Kagawa Prefecture, only 3% of the paddy soil was
classified as Gley Fluvic soils, whereas that figure was more
than 50% in Shimane and Shiga Prefectures. Gley Fluvic
soils are formed in wet paddy fields where the water table is
high and soil is clayey and impermeable. It is important
even now to improve the field permeability by introducing
open ditches and underground drainage especially when rice
is rotated with upland crops. According to a more recent
national survey from 1999 to 2003 (Ministry of Agriculture,
Forestry and Fisheries Agricultural Production Bureau
2008), the surface paddy soils in the Kinki, Chugoku, and
Shikoku regions showed lower values of total C and cation
exchange capacity than those in other regions of Japan.
Within these regions, the soil contents of exchangeable K
and available P tended to be higher in Kyoto and Kagawa
Prefectures.
9.2.3 Upland Fields
In the Kansai region (which includes the Kinki, Chugoku,
and Shikoku regions), wheat varieties, beans, and millets are
grown mainly in paddy fields utilized for double cropping or
paddy–upland rotation, or in dedicated crop fields converted
from paddy fields, thus providing production on diverse
farmlands adapted to local climatic and soil conditions. In
mountainous areas in the Shikoku region, crops are cultivated in small plots located on sloping lands.
1. Crop cultivation based on the fields originally used as
paddy (wheat varieties, beans, and millets)
To cultivate crops susceptible to moisture damage, such as
cereals, beans, and buckwheat (Fagopyrum esculentum), it is
of utmost importance to improve the drainage of farmland.
Depending on the climatic, topographic, and soil conditions,
various efforts are being made for enhanced drainage,
including the construction of open ditches, underdrains, and
mole drains (Fig. 9.4).
(1) Paddy–upland rotation for wheat and soybean
(Shiga Prefecture: Fluvic Paddy soils, etc.)
In Shiga Prefecture, where paddy fields account for as much
as 92% of all farmland, many farmers adopt a three-year
four-crop rotation of rice (summer harvest) to rice (summer
harvest) to wheat (winter harvest) to soybean (summer harvest) (Kitagawa 2012). For the cultivation of wheat and
soybean, Fluvic Paddy soils, Gray Fluvic soils, and Gley
Fluvic soils distributed along rivers around Lake Biwa are
used, with various measures being taken combining the use
of open ditches, underdrains, and mole drains for improving
the quantity and quality of production (Shiga Prefecture
2012).
(2) Soybean production (Hyogo Prefecture, Okayama
Prefecture: Gray Fluvic soils, Brown Fluvic soils)
In Hyogo Prefecture, soybean (Glycine max), including
large-grain black soybeans, are cultivated, mainly in Gray
Fluvic soils. Soybean is susceptible to humidity damage,
especially after seeding. Therefore, open ditches, underdrains, and radial-shaped mole drains have been constructed
to improve drainage. In Okayama Prefecture, large-grain
black soybean is cultivated mainly in Brown Fluvic soils. In
recent years, instances of decreased soybean harvest have
been reported, indicating a decline in soil fertility. In this
region, as in many other regions, a higher frequency of black
soybean cultivation has been shown to be correlated with
308
J. Yanai et al.