the nitrogen absorbing pattern in crops ensured the growth of
melon (Cucumis melo L.) and tomato (Solanum lycopersicum L.) without applying any chemical fertilizers. Similar
results were obtained for the co-application of composted
cattle manure, dried chicken manure, and rapeseed oil cake
to sweet pepper (Capsicum annuum L. var. “grossum”) (Ono
et al. 1998). Furthermore, Inoue (2015) showed that the yield
of onion (Allium cepa L.) with the co-application of composted cattle manure, composted chicken manure, and
rapeseed oil cake doubled compared with the yield with the
application of composted cattle manure only and was equal
to or greater than the yield with the co-application of
chemical fertilizer and composted cattle manure.
Organic fertilizer with low nitrogen mineralization characteristics (e.g., composted animal manure) can provide
inorganic nitrogen over one cropping season. Therefore, in a
cabbage–sweet potato double cropping system, composted
animal manure for which the amount of mineralized nitrogen
had been predicted for the cabbage cropping season was
applied once to cabbage in winter, and a small amount of
fertilizer was applied to the subsequent sweet potato.
Throughout the three-year experiment, yields in both crops
under composted animal manure were similar to those under
chemical fertilizer, and a high fertilizer nitrogen recovery
rate was obtained (76% and more than 100% for composted
cattle and chicken manure, respectively) (Matsumoto 2007).
During a four-year experiment, the single application of
concentrated stillage from shochu, a Japanese liquor, under a
daikon radish (Raphanus sativus var. longipinnatus)–sweet
potato double cropping system (one application to both
crops in a single year) resulted in yields of both radish and
sweet potato that were as high as those obtained under the
application of chemical fertilizer to every crop, while the
fertilizer nitrogen recovery rate was 75% throughout the
experiment (Niimi et al. 2016). Furthermore, phosphorus
and potassium were not accumulated in the soil.
Thus, in organic farming, it is possible to obtain high
nitrogen use efficiency and stable production by constructing
crop rotation systems introducing crops such as sweet potato
which can grow with limited nitrogen availability in soil as a
subsequent crop.
10.2.5 Soil Physical Properties
Although flooding is a prerequisite for paddy fields, the
increase in the use of tractors in the early 1960s accelerated
efforts toward the reformation of well-drained paddy fields
to ensure machine operability. Furthermore, when the production of rice began to be regulated in 1969, soybean began
to be used as a rotational crop. As a result, the number of
paddy–upland rotation fields increased. In order to allow
paddy fields to be alternately flooded and drained, the
consolidation of farmland including regional drainage
accommodations has been implemented (Haraguchi and
Wakasugi 2014). The promotion of upland crop cultivation
in rice fields involves a reduction in the length of the
flooding period, and in recent years, this has led to changes
in the properties of paddy fields that had maintained their
productivity despite continuous cropping. From the
Soil-Environmental Monitoring Project, which was implemented nationwide from 1979, and the long-term testing of
cultivated land, there have been reports of a decline in levels
of soil available nitrogen, which has led to an awareness of
declining soil fertility in paddy fields, as mentioned by
Sumida et al. (2005). On the other hand, no change trends
were identified on a national level in terms of physical
condition. For example, within Kyushu and Okinawa,
reports from Nagasaki Prefecture showed a high soil bulk
density in surveys from 1994–1998, as well as an increase in
the soil coefficient of permeability in surveys from 2009–
2013 (Inoue et al. 1999). Furthermore, reports from Miyazaki Prefecture showed declines in the solid ratio, bulk
density, and compactness as well as a rise in the air ratio
during 1984–1989 (Akagi et al. 2000). In the Kagoshima
Prefecture, no changes in bulk density were observed during
the 30-year period before 2007 (Nishi et al. 2013). Although
these reports did not exclusively find unfavorable phenomena, in terms of productivity, there are concerns that the
worsening physical conditions could be causing a decline in
soil fertility.
Overwetting is one of the major problems for the yield for
upland crops cultivated in paddy fields. Although topography and hydrographical conditions are difficult to control in
a field, double cropping (rice and wheat) has been implemented in northern Kyushu because of the warm climate.
Yoshida and Adachi (1985) carried out a detailed soil survey
in a deltaic plain between a natural levee and a hill. They
confirmed a mutual dependence among the topography,
hydrographical condition, soil distribution, and the growth
and yield of wheat. Even though the utiliazation rate of
paddy fields (total planted area of crops in paddy
fields/paddy field area  100) has been declining in recent
years, this figure in Kyushu area was nevertheless 113% in
2016, which is clearly different from other areas that have
ratios under 100% (Kyushu Regional Agricultural Administration Office 2018). Odahara et al. (2012) reported that in
areas where either wetland rice or soybean was planted in the
summer and wheat varieties were planted in the winter,
soybean yield decreased as the number of soybean plantings
increased (increasing upland usage ratio), which had a strong
positive correlation with the surface soil macropore ratio.
Although it was previously considered that the physical
condition of surface soil changes dramatically due to tilling,
those fundamental changes were difficult to observe on the
farmer’s fields; this report uncovered only one physical
340
Y. Arakawa et al.
melon (Cucumis melo L.) and tomato (Solanum lycopersicum L.) without applying any chemical fertilizers. Similar
results were obtained for the co-application of composted
cattle manure, dried chicken manure, and rapeseed oil cake
to sweet pepper (Capsicum annuum L. var. “grossum”) (Ono
et al. 1998). Furthermore, Inoue (2015) showed that the yield
of onion (Allium cepa L.) with the co-application of composted cattle manure, composted chicken manure, and
rapeseed oil cake doubled compared with the yield with the
application of composted cattle manure only and was equal
to or greater than the yield with the co-application of
chemical fertilizer and composted cattle manure.
Organic fertilizer with low nitrogen mineralization characteristics (e.g., composted animal manure) can provide
inorganic nitrogen over one cropping season. Therefore, in a
cabbage–sweet potato double cropping system, composted
animal manure for which the amount of mineralized nitrogen
had been predicted for the cabbage cropping season was
applied once to cabbage in winter, and a small amount of
fertilizer was applied to the subsequent sweet potato.
Throughout the three-year experiment, yields in both crops
under composted animal manure were similar to those under
chemical fertilizer, and a high fertilizer nitrogen recovery
rate was obtained (76% and more than 100% for composted
cattle and chicken manure, respectively) (Matsumoto 2007).
During a four-year experiment, the single application of
concentrated stillage from shochu, a Japanese liquor, under a
daikon radish (Raphanus sativus var. longipinnatus)–sweet
potato double cropping system (one application to both
crops in a single year) resulted in yields of both radish and
sweet potato that were as high as those obtained under the
application of chemical fertilizer to every crop, while the
fertilizer nitrogen recovery rate was 75% throughout the
experiment (Niimi et al. 2016). Furthermore, phosphorus
and potassium were not accumulated in the soil.
Thus, in organic farming, it is possible to obtain high
nitrogen use efficiency and stable production by constructing
crop rotation systems introducing crops such as sweet potato
which can grow with limited nitrogen availability in soil as a
subsequent crop.
10.2.5 Soil Physical Properties
Although flooding is a prerequisite for paddy fields, the
increase in the use of tractors in the early 1960s accelerated
efforts toward the reformation of well-drained paddy fields
to ensure machine operability. Furthermore, when the production of rice began to be regulated in 1969, soybean began
to be used as a rotational crop. As a result, the number of
paddy–upland rotation fields increased. In order to allow
paddy fields to be alternately flooded and drained, the
consolidation of farmland including regional drainage
accommodations has been implemented (Haraguchi and
Wakasugi 2014). The promotion of upland crop cultivation
in rice fields involves a reduction in the length of the
flooding period, and in recent years, this has led to changes
in the properties of paddy fields that had maintained their
productivity despite continuous cropping. From the
Soil-Environmental Monitoring Project, which was implemented nationwide from 1979, and the long-term testing of
cultivated land, there have been reports of a decline in levels
of soil available nitrogen, which has led to an awareness of
declining soil fertility in paddy fields, as mentioned by
Sumida et al. (2005). On the other hand, no change trends
were identified on a national level in terms of physical
condition. For example, within Kyushu and Okinawa,
reports from Nagasaki Prefecture showed a high soil bulk
density in surveys from 1994–1998, as well as an increase in
the soil coefficient of permeability in surveys from 2009–
2013 (Inoue et al. 1999). Furthermore, reports from Miyazaki Prefecture showed declines in the solid ratio, bulk
density, and compactness as well as a rise in the air ratio
during 1984–1989 (Akagi et al. 2000). In the Kagoshima
Prefecture, no changes in bulk density were observed during
the 30-year period before 2007 (Nishi et al. 2013). Although
these reports did not exclusively find unfavorable phenomena, in terms of productivity, there are concerns that the
worsening physical conditions could be causing a decline in
soil fertility.
Overwetting is one of the major problems for the yield for
upland crops cultivated in paddy fields. Although topography and hydrographical conditions are difficult to control in
a field, double cropping (rice and wheat) has been implemented in northern Kyushu because of the warm climate.
Yoshida and Adachi (1985) carried out a detailed soil survey
in a deltaic plain between a natural levee and a hill. They
confirmed a mutual dependence among the topography,
hydrographical condition, soil distribution, and the growth
and yield of wheat. Even though the utiliazation rate of
paddy fields (total planted area of crops in paddy
fields/paddy field area  100) has been declining in recent
years, this figure in Kyushu area was nevertheless 113% in
2016, which is clearly different from other areas that have
ratios under 100% (Kyushu Regional Agricultural Administration Office 2018). Odahara et al. (2012) reported that in
areas where either wetland rice or soybean was planted in the
summer and wheat varieties were planted in the winter,
soybean yield decreased as the number of soybean plantings
increased (increasing upland usage ratio), which had a strong
positive correlation with the surface soil macropore ratio.
Although it was previously considered that the physical
condition of surface soil changes dramatically due to tilling,
those fundamental changes were difficult to observe on the
farmer’s fields; this report uncovered only one physical
340
Y. Arakawa et al.