5.3 Upland Fields
5.3.1 Upland Soil
(1) Characteristics and problems of upland soil
In Hokkaido, problematic soils (see Sect. 5.1), which have
serious problems in terms of crop productivity and soil
management, are widely distributed, and the improvement of
their physical and chemical properties according to the
characteristics of each soil is required.
Volcanic ash soil generally has poor chemical properties,
such as high phosphate retention capacity, and wet soil
groups such as Gley Andosols and Wet Andosols have poor
drainage. Terrace soil is highly viscous and often tight, and
soil swelling and drainage measures are necessary. In lowland soil and fields converted from paddy field, drainage
improvement measures are often required.
For these problem soils, soil improvement through public
works, soil-dressing, open-channel drainage, subsurface
drainage, subsoil breaking, phosphate fertilization, liming,
and so on are highly effective. For large-scale countermeasures such as soil improvement projects, the reader is
referred to Sect. 5.1.2, where we describe improvement
technology that farmers can carry out within the range of
usual farming work.
(2) Subsoil breaking and drainage technology
In order to maintain good physical properties of soil, it is
important to suppress subsoil compaction and not to knead
soil during tractor plowing. In the upland fields of Hokkaido,
bottom plowing was typically done in autumn after the crop
harvest. However, in recent years, it has been encouraged to
perform a bottom plowing in spring where the soil is dry or a
chisel plowing without kneading the soil (Onodera et al.
2004).
Hard plow pan is formed by bottom plowing and suppresses crop growth and water permeability. The hardness
index value of plow pan is generally 1.5 MPa or more for a
cone penetrometer or 20 mm or more for a Yamanaka-type
soil hardness tester. The conducting of subsoil breaking is
effective in fields which have a plow pan with these index
values or greater (Nakatsu et al. 2004).
In recent years, wider types of construction, including a
type that does not mix subsoil in the surface soil, a mole
drain construction machine that does not use underdrain pipe
(Kitagawa et al. 2008), and so on, have been developed in
addition to the ordinary subsoil breaking instrument. These
instruments are highly effective, and farmers can use them to
improve the soil drainage. In order to maintain the function
of underdrainage over a long period of time, we encourage
the continual use of the subsoil breaking instrument.
Open-channel drainage is effective in fields where surface
water occurs frequently after heavy or prolonged rain.
Open-channel drainage is a farming technique involving
digging a groove in a field or around a field and discharging
the surface water outside the field.
The sloping of farm field is a farming technique which
involves sloping a field with the assistance of a laser leveler
(Wakasugi and Fujimori 2006). Farm field sloping promotes
gravitational drainage and is effective for draining surface
water.
In addition to the techniques mentioned here, the continuous application of organic material is very important for
soil improvement. If it is difficult to obtain high-quality
manure or compost, the cultivation of green manure is
desirable.
5.3.2 Cropping Systems
(1) Cropping system of upland field
A characteristic cropping system is implemented in every
area in Hokkaido according to the natural environment and
the management scale. Tokachi area is characterized by
large-scale farm management, and crop rotation of 3–4 years
is conducted, mainly combining sugar beet, potato, wheat,
and beans. However, the continuous cropping of wheat is
increasing due to scale expansion and labor shortage in this
area. Abashiri area is characterized by cool early summer
temperatures, and hence, bean cultivation is not common. In
this area, crop rotation of 2–3 years is conducted with sugar
beet, potato, and wheat. In some fields, the continuous
cropping of sugar beet and/or the alternating cropping of
sugar beet and potato is also conducted. In the Shiribeshi
area, where cultivated field is limited, Adzuki beans and
potato are mainly cultivated. In Kamikawa area, wheat,
beans and sugar beet are cultivated in the upland paddy
rotational fields of the central part and in hilly land in the
north and south.
(2) The effect of crop rotation on soil fertility
Plowing in crop residue is effective for the maintenance and
improvement of soil fertility, as reflected by measures such
as total carbon and total nitrogen. In Haplic Allophanic
Andosols of the Tokachi area, the annual application rate of
organic matter for maintaining the total carbon and total
nitrogen of upland fields was 2.5 Mg ha
−1 in dry matter. In
the general 4-year crop rotation of sugar beet, soybeans,
142
T. Nakatsuji et al.
5.3.1 Upland Soil
(1) Characteristics and problems of upland soil
In Hokkaido, problematic soils (see Sect. 5.1), which have
serious problems in terms of crop productivity and soil
management, are widely distributed, and the improvement of
their physical and chemical properties according to the
characteristics of each soil is required.
Volcanic ash soil generally has poor chemical properties,
such as high phosphate retention capacity, and wet soil
groups such as Gley Andosols and Wet Andosols have poor
drainage. Terrace soil is highly viscous and often tight, and
soil swelling and drainage measures are necessary. In lowland soil and fields converted from paddy field, drainage
improvement measures are often required.
For these problem soils, soil improvement through public
works, soil-dressing, open-channel drainage, subsurface
drainage, subsoil breaking, phosphate fertilization, liming,
and so on are highly effective. For large-scale countermeasures such as soil improvement projects, the reader is
referred to Sect. 5.1.2, where we describe improvement
technology that farmers can carry out within the range of
usual farming work.
(2) Subsoil breaking and drainage technology
In order to maintain good physical properties of soil, it is
important to suppress subsoil compaction and not to knead
soil during tractor plowing. In the upland fields of Hokkaido,
bottom plowing was typically done in autumn after the crop
harvest. However, in recent years, it has been encouraged to
perform a bottom plowing in spring where the soil is dry or a
chisel plowing without kneading the soil (Onodera et al.
2004).
Hard plow pan is formed by bottom plowing and suppresses crop growth and water permeability. The hardness
index value of plow pan is generally 1.5 MPa or more for a
cone penetrometer or 20 mm or more for a Yamanaka-type
soil hardness tester. The conducting of subsoil breaking is
effective in fields which have a plow pan with these index
values or greater (Nakatsu et al. 2004).
In recent years, wider types of construction, including a
type that does not mix subsoil in the surface soil, a mole
drain construction machine that does not use underdrain pipe
(Kitagawa et al. 2008), and so on, have been developed in
addition to the ordinary subsoil breaking instrument. These
instruments are highly effective, and farmers can use them to
improve the soil drainage. In order to maintain the function
of underdrainage over a long period of time, we encourage
the continual use of the subsoil breaking instrument.
Open-channel drainage is effective in fields where surface
water occurs frequently after heavy or prolonged rain.
Open-channel drainage is a farming technique involving
digging a groove in a field or around a field and discharging
the surface water outside the field.
The sloping of farm field is a farming technique which
involves sloping a field with the assistance of a laser leveler
(Wakasugi and Fujimori 2006). Farm field sloping promotes
gravitational drainage and is effective for draining surface
water.
In addition to the techniques mentioned here, the continuous application of organic material is very important for
soil improvement. If it is difficult to obtain high-quality
manure or compost, the cultivation of green manure is
desirable.
5.3.2 Cropping Systems
(1) Cropping system of upland field
A characteristic cropping system is implemented in every
area in Hokkaido according to the natural environment and
the management scale. Tokachi area is characterized by
large-scale farm management, and crop rotation of 3–4 years
is conducted, mainly combining sugar beet, potato, wheat,
and beans. However, the continuous cropping of wheat is
increasing due to scale expansion and labor shortage in this
area. Abashiri area is characterized by cool early summer
temperatures, and hence, bean cultivation is not common. In
this area, crop rotation of 2–3 years is conducted with sugar
beet, potato, and wheat. In some fields, the continuous
cropping of sugar beet and/or the alternating cropping of
sugar beet and potato is also conducted. In the Shiribeshi
area, where cultivated field is limited, Adzuki beans and
potato are mainly cultivated. In Kamikawa area, wheat,
beans and sugar beet are cultivated in the upland paddy
rotational fields of the central part and in hilly land in the
north and south.
(2) The effect of crop rotation on soil fertility
Plowing in crop residue is effective for the maintenance and
improvement of soil fertility, as reflected by measures such
as total carbon and total nitrogen. In Haplic Allophanic
Andosols of the Tokachi area, the annual application rate of
organic matter for maintaining the total carbon and total
nitrogen of upland fields was 2.5 Mg ha
−1 in dry matter. In
the general 4-year crop rotation of sugar beet, soybeans,
142
T. Nakatsuji et al.