aim of accepting surplus population and increasing food
production. However, it was difficult for colonists to settle
due to severe land conditions. In 1952, a comprehensive
development plan was launched, involving the development
of large-scale agricultural land, which positioned Hokkaido
as a food production base in Japan. The development of
paddy fields in the Ishikari peatlands and the construction of
dairy pilot farms in the Konsen area were implemented, and
by 1985 a total of 600,000 ha of farmland had been created.
The area of cultivated land reached 1,209,000 ha in 1990
and then gradually declined to 1,146,000 ha in 2016.
Together with the “outline of the soils of suitable land for
agriculture,” which summarized the soil survey results of
arable land in Hokkaido, the outline map of problem soils in
Hokkaido (1:1,000,000 scale) was published in 1951 and
was widely used as a basis for agricultural development and
land improvement plans.
In Japan’s period of high economic growth from around
1960, agricultural machinery (e.g. tractors) was introduced
in response to the shortage of rural labor. With projects
based on the Basic Law of Agriculture, large-scale field
improvement, such as rezoning of areas, flattening, setting of
underdrain, and so on, was advanced, and the efficiency of
machine work and productivity were improved. With the
development of dairy farms, pastures grew rapidly, and at
the same time paddy rice production expanded. As a result,
the area of uplands decreased. The agricultural land area per
household increased due to the decrease in farming. However, the rice production adjustment policy that began in
1970 caused a sharp decline in the cultivation of paddy rice;
as a result, rice cultivation in the eastern area of Hokkaido
almost disappeared, and various field crops were introduced
in paddy fields.
In Hokkaido, acidic soils, volcanic ash soils, peat soils,
and heavy clay soils were known as “problem soils” before
the war; however, after 1960, these soils were rapidly
improved with the introduction of large machines: drainage
and mineral soil-dressing were carried out in peatland;
underdrainage and subsoiling were performed in heavy clay
soils; and coarse volcanic soil, the improvement of which
was delayed, could be improved by mixing tillage and so on
(Nishimune and Sekiya 1999).
After World War II, the application of fertilizer increased
rapidly both in paddy rice fields and upland farms, and
yields increased accordingly. The application rate of nitrogen, phosphorus, and potassium per area almost doubled
between 1950 and 1970, leading to a yield increase of 100%
in upland crops and of 60% in paddy rice.
5.1.2 Soils
(1) Climate
Hokkaido is located in Northern Japan. The cold current
“Oyashio” flows east side, and the warm current “Kuroshio”
flows west side. The annual average temperature is 5–10 °C,
while the annual average soil temperature at 0.5 m depth is
estimated as 9.3 °C in Sapporo and 7.4 °C in Nemuro. The soil
temperature regime is classified as mesic to frigid. Precipitation
is in the range of 700–1200 mm per year, which is relatively low
for Japan. Precipitation is low from February to June and peaks
from August to September. The western area of Hokkaido
receives large amounts of precipitation from October to January,
causing heavy snowfall. Therefore, the soil drying season occurs
in only a short period from spring to the beginning of summer. In
Eastern Hokkaido, the temperature is very low in winter due to
radiative cooling, and there is little snowfall. As a result, soil
freezing occurs from December to April, to a depth of about 0.1–
0.4 m. Recently, however, the soil freezing depth has changed to
be shallow due to global warming.
(2) Soil parent materials
The geological basement of Hokkaido is composed of volcanic rocks (mainly andesite), metamorphic rocks, and
sedimentary rocks such as sandstone and conglomerate of
tertiary age. These rocks are the parent materials for soils
such as brown forest soils in mountainous and diluvial plateau areas. Cultivated areas are scarce in these areas due to
the harsh climate. In coastal and riverine areas, the land rose
up in diluvium during the Quaternary Period (glacial period),
forming terraces. The fine-textured sediment in these terraces has been dehydrated and compacted, forming “Terrace
soil”, which is characterized by its fine texture and hardness.
In alluvial land around rivers, lowland soils are widely distributed. In particular, peat is formed in marshy areas in the
lower reaches of large, calm rivers such as the Ishikari,
Teshio, and Kushiro Rivers. These peat areas had generally
been reclaimed by the end of the 1940s. Furthermore, as
there are 20 active volcanoes on Hokkaido, volcanic ash or
pyroclastic deposits widely cover the island. Some of these
pyroclastic deposits were deposited 20 years ago or earlier,
while others were deposited earlier in the Quaternary
(Committee on Nomenclature of the Pyroclastic Deposit in
Hokkaido 1974). These pyroclastic deposits provide parent
material for volcanic ash soils. Volcanic ash soil formed
from volcanic material which deposited less than a thousand
5 Hokkaido Region
137
production. However, it was difficult for colonists to settle
due to severe land conditions. In 1952, a comprehensive
development plan was launched, involving the development
of large-scale agricultural land, which positioned Hokkaido
as a food production base in Japan. The development of
paddy fields in the Ishikari peatlands and the construction of
dairy pilot farms in the Konsen area were implemented, and
by 1985 a total of 600,000 ha of farmland had been created.
The area of cultivated land reached 1,209,000 ha in 1990
and then gradually declined to 1,146,000 ha in 2016.
Together with the “outline of the soils of suitable land for
agriculture,” which summarized the soil survey results of
arable land in Hokkaido, the outline map of problem soils in
Hokkaido (1:1,000,000 scale) was published in 1951 and
was widely used as a basis for agricultural development and
land improvement plans.
In Japan’s period of high economic growth from around
1960, agricultural machinery (e.g. tractors) was introduced
in response to the shortage of rural labor. With projects
based on the Basic Law of Agriculture, large-scale field
improvement, such as rezoning of areas, flattening, setting of
underdrain, and so on, was advanced, and the efficiency of
machine work and productivity were improved. With the
development of dairy farms, pastures grew rapidly, and at
the same time paddy rice production expanded. As a result,
the area of uplands decreased. The agricultural land area per
household increased due to the decrease in farming. However, the rice production adjustment policy that began in
1970 caused a sharp decline in the cultivation of paddy rice;
as a result, rice cultivation in the eastern area of Hokkaido
almost disappeared, and various field crops were introduced
in paddy fields.
In Hokkaido, acidic soils, volcanic ash soils, peat soils,
and heavy clay soils were known as “problem soils” before
the war; however, after 1960, these soils were rapidly
improved with the introduction of large machines: drainage
and mineral soil-dressing were carried out in peatland;
underdrainage and subsoiling were performed in heavy clay
soils; and coarse volcanic soil, the improvement of which
was delayed, could be improved by mixing tillage and so on
(Nishimune and Sekiya 1999).
After World War II, the application of fertilizer increased
rapidly both in paddy rice fields and upland farms, and
yields increased accordingly. The application rate of nitrogen, phosphorus, and potassium per area almost doubled
between 1950 and 1970, leading to a yield increase of 100%
in upland crops and of 60% in paddy rice.
5.1.2 Soils
(1) Climate
Hokkaido is located in Northern Japan. The cold current
“Oyashio” flows east side, and the warm current “Kuroshio”
flows west side. The annual average temperature is 5–10 °C,
while the annual average soil temperature at 0.5 m depth is
estimated as 9.3 °C in Sapporo and 7.4 °C in Nemuro. The soil
temperature regime is classified as mesic to frigid. Precipitation
is in the range of 700–1200 mm per year, which is relatively low
for Japan. Precipitation is low from February to June and peaks
from August to September. The western area of Hokkaido
receives large amounts of precipitation from October to January,
causing heavy snowfall. Therefore, the soil drying season occurs
in only a short period from spring to the beginning of summer. In
Eastern Hokkaido, the temperature is very low in winter due to
radiative cooling, and there is little snowfall. As a result, soil
freezing occurs from December to April, to a depth of about 0.1–
0.4 m. Recently, however, the soil freezing depth has changed to
be shallow due to global warming.
(2) Soil parent materials
The geological basement of Hokkaido is composed of volcanic rocks (mainly andesite), metamorphic rocks, and
sedimentary rocks such as sandstone and conglomerate of
tertiary age. These rocks are the parent materials for soils
such as brown forest soils in mountainous and diluvial plateau areas. Cultivated areas are scarce in these areas due to
the harsh climate. In coastal and riverine areas, the land rose
up in diluvium during the Quaternary Period (glacial period),
forming terraces. The fine-textured sediment in these terraces has been dehydrated and compacted, forming “Terrace
soil”, which is characterized by its fine texture and hardness.
In alluvial land around rivers, lowland soils are widely distributed. In particular, peat is formed in marshy areas in the
lower reaches of large, calm rivers such as the Ishikari,
Teshio, and Kushiro Rivers. These peat areas had generally
been reclaimed by the end of the 1940s. Furthermore, as
there are 20 active volcanoes on Hokkaido, volcanic ash or
pyroclastic deposits widely cover the island. Some of these
pyroclastic deposits were deposited 20 years ago or earlier,
while others were deposited earlier in the Quaternary
(Committee on Nomenclature of the Pyroclastic Deposit in
Hokkaido 1974). These pyroclastic deposits provide parent
material for volcanic ash soils. Volcanic ash soil formed
from volcanic material which deposited less than a thousand
5 Hokkaido Region
137