adequate application of compost is effective for maintaining
soil fertility (Kitagawa et al. 2009; Fujitomi et al. 2014) and
also enables the reduction of fertilizer application (Haruguchi et al. 2009; Fukuda et al. 2001; Ishii et al. 2016). As
livestock manure is not sufficiently applied in paddy fields in
northern Kyushu, it is encouraged to incorporate rice straw
and wheat straw into paddy soil without burning to maintain
soil fertility (Kitagawa et al. 2009). In Saga Prefecture in
2016, half of rice straw was removed from paddy fields, for
various purposes, and half was plowed into the soil. The
percentage of rice-cultivated fields in which rice straw was
burned was just 4% in the prefecture. Compared with rice
straw, the usage of wheat and barley straws out of fields is
not common. These straws are plowed in 80% of their cultivated field. The percentage of cultivated fields in which
straw was burned was about 10%. Plowing straw suppresses
the initial growth of crops, but also suppresses weed incidence and increases rice yield by improving the ripening
(Hideshima et al. 2016).
To allow two crops a year to be produced in northern
Kyushu, it is important to keep the soil fertility high. In
order to achieve this without increasing cultivation costs,
various locally unutilized organic matter should be applied.
Therefore, it is necessary to estimate the (highly variable)
fertility of paddy fields to which various organic matters are
applied, and to establish a fertilization method to give
high-quality and high-yield products in individual paddy
fields.
10.3.3 Vegetable Production on Isahaya Bay
Reclaimed Land
(1) Agriculture on reclaimed land
Isahaya Bay is located on the northwest coast of the Ariake
Sea in northwest Kyushu. The surrounding low-lying area is
geographically and topographically susceptible to typhoons
and torrential rain. This area has been affected by natural
disasters many times, such as the Great Flood of Isahaya,
which took place on 25 July 1957. Therefore, in order to
enhance the effectiveness of regional disaster prevention and
to develop large amounts of flat farmland with higher productivity, the National Project of Isahaya Bay Land Reclamation, which was conducted between 1989 and 2008,
implemented a double dike system of land reclamation in
which both ocean and land are blocked. This project
developed 672 ha of farmland, 12 ha of housing land,
2600 ha of flood regulation pond, 126 ha of bank land, and
132 ha of road and canal land. Upland irrigation was
introduced using water in regulated pondage in all fields.
This allows for large-scale vegetable farming and horticultural enterprise. The farmlands are leased to immigrants,
who were selected from various applicants.
(2) Features Isahaya Bay reclaimed soil
The reclaimed land of Isahaya Bay is located on a sea coast,
and its soil parent materials are marine deposits. Most soils
are classified as Gley Fluvic soils immediately after land
drying, being rich in smectite-a 2:1 type clay minerals and
classified as clayey in soil texture. The soil has a high
stickiness and low permeability, and consequently, drainage
systems have been installed at 10-m intervals in fields. The
soil has a high nutrient-holding capacity, high levels of
exchangeable bases, and is rich in available phosphate,
however has a low organic matter content. In particular, its
high concentration of chloride ions and alkaline soil pH has
caused concerns about crop cultivation.
(3) Soil management up to the time when farming starts
Terai et al. (2006) examined the desalinization and drainage
measure of the heavy reclaimed soil and found that the
desalinization to a level that made upland farming possible
by green manure cultivation for two years or during four
crop seasons in conjunction with field drainage using supplementary drainage (Table 10.3).
This achievement was possible due to the following
reasons: (1) An annual rainfall of approximately 2000 mm;
(2) the increase of evapotranspiration caused by the green
manure crop; and (3) the occurrence of large-scale soil
cracking caused by the shrinkage of clay during drying.
(4) Soil management after the initiation of farming
After desalinization and the improvement of permeability on all
farmland, farming was started in the Isahaya Bay reclaimed land
in April 2008. In 2016, the total growing area was 1117 ha, with
onions, lettuce, wheat (Triticum aestivum L.), barley (Hordeum
vulgare L.), carrots, cabbages, broccoli (Brassica oleracea var.
italica), and perilla (Perilla frutescens var. crispa) being cultivated. The local government provides a guidance of large-scale
environmental-friendly agricultural practices in the Isahaya Bay
reclaimed land (Nagasaki Prefecture 2013). Farmers are
encouraged to utilize organic fertilizers such as oil cake, cattle
manure compost pellets, and poultry litter to halve nitrogen
application.
10 Kyushu and Okinawa Regions
343
soil fertility (Kitagawa et al. 2009; Fujitomi et al. 2014) and
also enables the reduction of fertilizer application (Haruguchi et al. 2009; Fukuda et al. 2001; Ishii et al. 2016). As
livestock manure is not sufficiently applied in paddy fields in
northern Kyushu, it is encouraged to incorporate rice straw
and wheat straw into paddy soil without burning to maintain
soil fertility (Kitagawa et al. 2009). In Saga Prefecture in
2016, half of rice straw was removed from paddy fields, for
various purposes, and half was plowed into the soil. The
percentage of rice-cultivated fields in which rice straw was
burned was just 4% in the prefecture. Compared with rice
straw, the usage of wheat and barley straws out of fields is
not common. These straws are plowed in 80% of their cultivated field. The percentage of cultivated fields in which
straw was burned was about 10%. Plowing straw suppresses
the initial growth of crops, but also suppresses weed incidence and increases rice yield by improving the ripening
(Hideshima et al. 2016).
To allow two crops a year to be produced in northern
Kyushu, it is important to keep the soil fertility high. In
order to achieve this without increasing cultivation costs,
various locally unutilized organic matter should be applied.
Therefore, it is necessary to estimate the (highly variable)
fertility of paddy fields to which various organic matters are
applied, and to establish a fertilization method to give
high-quality and high-yield products in individual paddy
fields.
10.3.3 Vegetable Production on Isahaya Bay
Reclaimed Land
(1) Agriculture on reclaimed land
Isahaya Bay is located on the northwest coast of the Ariake
Sea in northwest Kyushu. The surrounding low-lying area is
geographically and topographically susceptible to typhoons
and torrential rain. This area has been affected by natural
disasters many times, such as the Great Flood of Isahaya,
which took place on 25 July 1957. Therefore, in order to
enhance the effectiveness of regional disaster prevention and
to develop large amounts of flat farmland with higher productivity, the National Project of Isahaya Bay Land Reclamation, which was conducted between 1989 and 2008,
implemented a double dike system of land reclamation in
which both ocean and land are blocked. This project
developed 672 ha of farmland, 12 ha of housing land,
2600 ha of flood regulation pond, 126 ha of bank land, and
132 ha of road and canal land. Upland irrigation was
introduced using water in regulated pondage in all fields.
This allows for large-scale vegetable farming and horticultural enterprise. The farmlands are leased to immigrants,
who were selected from various applicants.
(2) Features Isahaya Bay reclaimed soil
The reclaimed land of Isahaya Bay is located on a sea coast,
and its soil parent materials are marine deposits. Most soils
are classified as Gley Fluvic soils immediately after land
drying, being rich in smectite-a 2:1 type clay minerals and
classified as clayey in soil texture. The soil has a high
stickiness and low permeability, and consequently, drainage
systems have been installed at 10-m intervals in fields. The
soil has a high nutrient-holding capacity, high levels of
exchangeable bases, and is rich in available phosphate,
however has a low organic matter content. In particular, its
high concentration of chloride ions and alkaline soil pH has
caused concerns about crop cultivation.
(3) Soil management up to the time when farming starts
Terai et al. (2006) examined the desalinization and drainage
measure of the heavy reclaimed soil and found that the
desalinization to a level that made upland farming possible
by green manure cultivation for two years or during four
crop seasons in conjunction with field drainage using supplementary drainage (Table 10.3).
This achievement was possible due to the following
reasons: (1) An annual rainfall of approximately 2000 mm;
(2) the increase of evapotranspiration caused by the green
manure crop; and (3) the occurrence of large-scale soil
cracking caused by the shrinkage of clay during drying.
(4) Soil management after the initiation of farming
After desalinization and the improvement of permeability on all
farmland, farming was started in the Isahaya Bay reclaimed land
in April 2008. In 2016, the total growing area was 1117 ha, with
onions, lettuce, wheat (Triticum aestivum L.), barley (Hordeum
vulgare L.), carrots, cabbages, broccoli (Brassica oleracea var.
italica), and perilla (Perilla frutescens var. crispa) being cultivated. The local government provides a guidance of large-scale
environmental-friendly agricultural practices in the Isahaya Bay
reclaimed land (Nagasaki Prefecture 2013). Farmers are
encouraged to utilize organic fertilizers such as oil cake, cattle
manure compost pellets, and poultry litter to halve nitrogen
application.
10 Kyushu and Okinawa Regions
343