The roots of tea plants grow well in autumn, and the late
summer and early autumn are therefore the best period for
soil improvement. To amend soil acidification, lime is
applied at this time. Furthermore, in order to improve the
physical properties of the soil, deep plowing (down to about
30 cm in depth) is recommended. However, deep plowing
has recently tended to be omitted because of the high
workload required. As a result, there is concern about the
degradation of soil physical properties. To improve these
properties, organic matter such as manure and dried grasses
is applied and incorporated into soils. In some tea growing
areas, in an effort to obtain grasses for application to tea
gardens, semi-natural grassland, which is called “chagusaba” in Japanese, has been maintained by farmers around
tea gardens. The primary purpose of maintaining the grassland is to improve tea quality, but this has also contributed to
the conservation of biodiversity (Inagaki and Kusumoto
2014). Due to the good balance between agricultural production and biodiversity conservation, the “traditional tea–
grass integrated system in Shizuoka” was certified as a
Globally Important Agricultural Heritage Systems (GIAHS).
(2) Improvement of nitrogen use efficiency in tea
production
Japanese green tea tends to be traded at high prices for
products containing high free amino acid content, one of the
most important quality indices for Japanese green tea, and
tea plants can store excessive amounts of absorbed nitrogen
as amino acids in the plant body. Thus, high rates of
nitrogen application can increase the concentrations of
amino acids in new shoots. As a result, the amount of N
applied to tea gardens has been increased in some tea
growing areas.
The nitrogen application rates at tea production sites had
often exceeded the recommended amount of nitrogen fertilizer application, that is, the nutrient requirement of tea
plants in some tea growing areas. The surplus nitrogen
application sometimes increases the yield and quality of tea
products but can also cause a decrease in the amount of fine
roots of tea plants, causing a vicious cycle of requiring large
amounts of nitrogen to maintain the yield and quality of tea.
Consequently, environmental problems have arisen. For
example, increasing amounts of surplus nitrogen are leached
from tea gardens, which increase NO 3
−
-N concentrations in
the surrounding water systems (Nagai 1991). Additionally,
the surplus nitrogen application also caused soil acidification
and high emission rates of nitrous oxide (N 2 O) (Tokuda and
Hayatsu 2004), one of the major greenhouse gasses and an
ozone-depleting substance.
To address the problems mentioned above, various fertilizer management methods have been developed.
Fertilizers with enhanced efficiency have been developed to
improve the efficiency of nitrogen use by crops. Among
these, coated urea is representative of tea cultivation in
Japan. Coated urea gradually releases nitrogen and is used in
accordance with the amount required by tea plants. In
addition to the use of fertilizers with enhanced efficiency,
other new methods of fertilizer application, such as
expanding the width of fertilizer application and drip fertigation, which enables the utilization of the root zone under
the tea plant canopy, have been proposed in order to increase
the efficiency of nitrogen uptake by tea plants.
3. Pelleting of livestock manure for environmental
friendly agriculture in Mie Prefecture.
Mie Prefecture has 61,000 ha of agricultural land, with paddy
fields being the predominant land use (46,000 ha) in this
sector. The areas of upland fields and orchards are 8800 ha
and 6400 ha, respectively. Fluvic soils occupy 60% of the
agricultural land, followed by Andosols (11%) and
Red-Yellow soils (10%). Gley Fluvic soils and Gray Fluvic
soils are the dominant soil groups in paddy fields, and
Non-Allophanic Andosols and Argic Red-Yellow soils are the
dominant groups in upland fields and orchards, respectively.
(1) Soil fertility status
The Fundamental Guideline for Soil Productivity Improvement, which is based on the Soil Productivity Improvement
Law, specifies a standard application rate of manure for
paddy fields and upland fields of 10 to 15 Mg ha
−1 and 15 to
30 Mg ha
−1 , respectively. However, the application rate of
organic manure has been decreasing due to the aging
farming population and the increasing farm acreage per
farm. In particular, the application rate of manure is very low
in paddy fields, because this resource depends on rice straw.
According to the National Agricultural Management Statistics, the average application rate of manure in Japanese
paddy fields decreased from 5.5 Mg ha
−1 in 1965 to
1.3 Mg ha
−1 in 1997. The decrease in the rate of manure
application to paddy fields in Mie Prefecture was at the same
level as the Japanese average, but a 2-year crop rotation
system (rice, wheat, soybean) was widely conducted there in
paddy–upland rotation fields. Prolonged non-rice cultivation
in paddy fields caused a decrease in soil organic matter and
soil productivity. It was thought that soil fertility could be
maintained by total rice straw plowing; however, the prolongation of non-rice cultivation in the paddy–upland fields
and global warming may increase the decomposition rate of
soil organic matter. It is estimated that increased application
of manure (15 Mg ha
−1 ) with total rice straw plowing is
required in order to maintain soil fertility for the 2-year crop
8 Chubu Region (Hokuriku/Tokai)
295
summer and early autumn are therefore the best period for
soil improvement. To amend soil acidification, lime is
applied at this time. Furthermore, in order to improve the
physical properties of the soil, deep plowing (down to about
30 cm in depth) is recommended. However, deep plowing
has recently tended to be omitted because of the high
workload required. As a result, there is concern about the
degradation of soil physical properties. To improve these
properties, organic matter such as manure and dried grasses
is applied and incorporated into soils. In some tea growing
areas, in an effort to obtain grasses for application to tea
gardens, semi-natural grassland, which is called “chagusaba” in Japanese, has been maintained by farmers around
tea gardens. The primary purpose of maintaining the grassland is to improve tea quality, but this has also contributed to
the conservation of biodiversity (Inagaki and Kusumoto
2014). Due to the good balance between agricultural production and biodiversity conservation, the “traditional tea–
grass integrated system in Shizuoka” was certified as a
Globally Important Agricultural Heritage Systems (GIAHS).
(2) Improvement of nitrogen use efficiency in tea
production
Japanese green tea tends to be traded at high prices for
products containing high free amino acid content, one of the
most important quality indices for Japanese green tea, and
tea plants can store excessive amounts of absorbed nitrogen
as amino acids in the plant body. Thus, high rates of
nitrogen application can increase the concentrations of
amino acids in new shoots. As a result, the amount of N
applied to tea gardens has been increased in some tea
growing areas.
The nitrogen application rates at tea production sites had
often exceeded the recommended amount of nitrogen fertilizer application, that is, the nutrient requirement of tea
plants in some tea growing areas. The surplus nitrogen
application sometimes increases the yield and quality of tea
products but can also cause a decrease in the amount of fine
roots of tea plants, causing a vicious cycle of requiring large
amounts of nitrogen to maintain the yield and quality of tea.
Consequently, environmental problems have arisen. For
example, increasing amounts of surplus nitrogen are leached
from tea gardens, which increase NO 3
−
-N concentrations in
the surrounding water systems (Nagai 1991). Additionally,
the surplus nitrogen application also caused soil acidification
and high emission rates of nitrous oxide (N 2 O) (Tokuda and
Hayatsu 2004), one of the major greenhouse gasses and an
ozone-depleting substance.
To address the problems mentioned above, various fertilizer management methods have been developed.
Fertilizers with enhanced efficiency have been developed to
improve the efficiency of nitrogen use by crops. Among
these, coated urea is representative of tea cultivation in
Japan. Coated urea gradually releases nitrogen and is used in
accordance with the amount required by tea plants. In
addition to the use of fertilizers with enhanced efficiency,
other new methods of fertilizer application, such as
expanding the width of fertilizer application and drip fertigation, which enables the utilization of the root zone under
the tea plant canopy, have been proposed in order to increase
the efficiency of nitrogen uptake by tea plants.
3. Pelleting of livestock manure for environmental
friendly agriculture in Mie Prefecture.
Mie Prefecture has 61,000 ha of agricultural land, with paddy
fields being the predominant land use (46,000 ha) in this
sector. The areas of upland fields and orchards are 8800 ha
and 6400 ha, respectively. Fluvic soils occupy 60% of the
agricultural land, followed by Andosols (11%) and
Red-Yellow soils (10%). Gley Fluvic soils and Gray Fluvic
soils are the dominant soil groups in paddy fields, and
Non-Allophanic Andosols and Argic Red-Yellow soils are the
dominant groups in upland fields and orchards, respectively.
(1) Soil fertility status
The Fundamental Guideline for Soil Productivity Improvement, which is based on the Soil Productivity Improvement
Law, specifies a standard application rate of manure for
paddy fields and upland fields of 10 to 15 Mg ha
−1 and 15 to
30 Mg ha
−1 , respectively. However, the application rate of
organic manure has been decreasing due to the aging
farming population and the increasing farm acreage per
farm. In particular, the application rate of manure is very low
in paddy fields, because this resource depends on rice straw.
According to the National Agricultural Management Statistics, the average application rate of manure in Japanese
paddy fields decreased from 5.5 Mg ha
−1 in 1965 to
1.3 Mg ha
−1 in 1997. The decrease in the rate of manure
application to paddy fields in Mie Prefecture was at the same
level as the Japanese average, but a 2-year crop rotation
system (rice, wheat, soybean) was widely conducted there in
paddy–upland rotation fields. Prolonged non-rice cultivation
in paddy fields caused a decrease in soil organic matter and
soil productivity. It was thought that soil fertility could be
maintained by total rice straw plowing; however, the prolongation of non-rice cultivation in the paddy–upland fields
and global warming may increase the decomposition rate of
soil organic matter. It is estimated that increased application
of manure (15 Mg ha
−1 ) with total rice straw plowing is
required in order to maintain soil fertility for the 2-year crop
8 Chubu Region (Hokuriku/Tokai)
295