ingredient with reference to the recommended fertilizer
amount, the amount of fertilizer to be applied for the area of
the field and the fertilizer costs are calculated and displayed.
A database of the nutrient composition of the 26 main
livestock manures and composts distributed in Aomori
Prefecture has been registered, making it is possible to calculate the level of fertilizer reduction required based on the
amount of nutrients in the soil and in the soil improvement
materials applied.
In Aomori Prefecture, all producers are involved in the
“healthy soil making” initiative, using appropriate (and
rationalized) amounts of inorganic and organic soil
improvement materials on the basis of soil analysis, and
hence reducing the need for (and cost of) fertilizers. Using
safe and reliable amounts of agricultural products as a selling
point, we aim to raise the added value of the prefectural
agricultural products. An effective tool to achieve this is the
Sehi Navi internet application, which as described can
compute the proper application rates of inorganic soil
improvement materials, composts, composted manures, and
fertilizers, in a simple operation.
6.2.6 Usage of Excess Accumulated Phosphate
Being susceptible to the effect of cold winds, called
“Yamase” in Japanese, Iwate Prefecture has experienced a
number of seriously cold weather events in the past. Additionally, volcanic ash-derived Andosols, which efficiently
immobilize phosphate, are widely distributed in the paddy
field soils of this prefecture. Phosphate application is considered to promote the initial growth of paddy rice, and
multiple applications are actively conducted to fertilize the
soil and counteract low soil temperatures. As a result, large
amounts of phosphate have accumulated in the paddy field
soils of Iwate Prefecture.
In an effort to minimize over-application, we developed a
fertilizer application method that monitors the phosphate
which accumulates in the soil.
To evaluate the relationship between the available phosphate content and the amount of phosphate applied to each
type of soil, we investigated numerous test cases to obtain a
yield increase index. Figure 6.12 summarizes the influence
of phosphate fertilizer application on paddy rice yield; the
indicator used here is based on the gross brown rice amount
set as 100 from the same or adjacent fields when phosphate
is applied at levels of 0 or 30 kg ha
−1 . The results revealed
that when the level of available phosphate was below
60 mg kg
−1 the increase in rice yield was substantial, but
that when level of available phosphate was 60–300 mg kg
−1
there were large annual fluctuations in yield. When the level
of available phosphate was more than 300 mg kg
−1 , phosphate application did not influence yield. Additionally, at
available phosphate levels of 300 mg kg
−1 or below, tillering was delayed in years when low temperatures were
experienced at the start of the growth period. Table 6.5
shows the cases in which yields were affected. In 1993, the
yield was considerably lower because of very cold weather,
which is apparent in the graph.
Considering the abovementioned facts, the levels of
available aqueous phosphate in paddy rice, regardless of soil
type, are summarized in Table 6.6.
It was confirmed that when the level of available phosphate was more than 300 mg kg
−1 , yields were unaffected,
even when no additional phosphate was applied; however,
discontinuing phosphate application would likely decrease
available phosphate. Thus, periodic soil analysis is required.
6.3 Management of Upland Soils
6.3.1 Organic Matter Application
In the Tohoku region, upland fields are often located on
Andosols generated from volcanic products. Additionally,
livestock farming is concentrated in Iwate Prefecture and on
the Pacific Ocean side of Aomori Prefecture. Therefore,
animal manure is mainly applied to the Andosol upland
fields. Although Andosols are characterized by a high
organic matter content, the application of organic matter on
these soils nevertheless has a positive effect on the soil
properties and crop growth. This section describes the
dynamics of applied organic matter in Andosols and its
effect on the formation of macroaggregates.
Generally, the level of SOM tends to decrease over time
when the soil is used as an upland field. Thus, it is necessary
to apply an appropriate amount of organic matter to the field
in order to maintain the level of SOM.
We investigated the effects of the continuous application
of cattle manure on the quantity and quality of SOM in an
Andosol (Aoyama and Kumakura 2001). Over a period of
20 years, surface soil samples were collected periodically
from plots treated with NPK and NPK + manure, with
application rates of 80, 160, and 320 Mg ha
−1 yr
−1 , at the
Tohoku Agricultural Research Center in Morioka. Particulate organic matter (POM, > 53 µm) and mineral-associated
organic matter (MAOM, < 53 µm) fractions were separated
from the soil samples by sieving after mechanical dispersion.
In the soil treated with only NPK, a significant decrease
in the concentration of total organic carbon (C), reaching up
to 10%, was observed after 20 years (Fig. 6.13). Although
the application of only NPK had no significant effect on the
amount of POM-C, the amount of MAOM-C decreased over
time. This indicates that the decrease in the concentration of
organic C in the soil treated with only NPK was due to a
decrease in the amount of MAOM.
6 Tohoku Region
203
amount, the amount of fertilizer to be applied for the area of
the field and the fertilizer costs are calculated and displayed.
A database of the nutrient composition of the 26 main
livestock manures and composts distributed in Aomori
Prefecture has been registered, making it is possible to calculate the level of fertilizer reduction required based on the
amount of nutrients in the soil and in the soil improvement
materials applied.
In Aomori Prefecture, all producers are involved in the
“healthy soil making” initiative, using appropriate (and
rationalized) amounts of inorganic and organic soil
improvement materials on the basis of soil analysis, and
hence reducing the need for (and cost of) fertilizers. Using
safe and reliable amounts of agricultural products as a selling
point, we aim to raise the added value of the prefectural
agricultural products. An effective tool to achieve this is the
Sehi Navi internet application, which as described can
compute the proper application rates of inorganic soil
improvement materials, composts, composted manures, and
fertilizers, in a simple operation.
6.2.6 Usage of Excess Accumulated Phosphate
Being susceptible to the effect of cold winds, called
“Yamase” in Japanese, Iwate Prefecture has experienced a
number of seriously cold weather events in the past. Additionally, volcanic ash-derived Andosols, which efficiently
immobilize phosphate, are widely distributed in the paddy
field soils of this prefecture. Phosphate application is considered to promote the initial growth of paddy rice, and
multiple applications are actively conducted to fertilize the
soil and counteract low soil temperatures. As a result, large
amounts of phosphate have accumulated in the paddy field
soils of Iwate Prefecture.
In an effort to minimize over-application, we developed a
fertilizer application method that monitors the phosphate
which accumulates in the soil.
To evaluate the relationship between the available phosphate content and the amount of phosphate applied to each
type of soil, we investigated numerous test cases to obtain a
yield increase index. Figure 6.12 summarizes the influence
of phosphate fertilizer application on paddy rice yield; the
indicator used here is based on the gross brown rice amount
set as 100 from the same or adjacent fields when phosphate
is applied at levels of 0 or 30 kg ha
−1 . The results revealed
that when the level of available phosphate was below
60 mg kg
−1 the increase in rice yield was substantial, but
that when level of available phosphate was 60–300 mg kg
−1
there were large annual fluctuations in yield. When the level
of available phosphate was more than 300 mg kg
−1 , phosphate application did not influence yield. Additionally, at
available phosphate levels of 300 mg kg
−1 or below, tillering was delayed in years when low temperatures were
experienced at the start of the growth period. Table 6.5
shows the cases in which yields were affected. In 1993, the
yield was considerably lower because of very cold weather,
which is apparent in the graph.
Considering the abovementioned facts, the levels of
available aqueous phosphate in paddy rice, regardless of soil
type, are summarized in Table 6.6.
It was confirmed that when the level of available phosphate was more than 300 mg kg
−1 , yields were unaffected,
even when no additional phosphate was applied; however,
discontinuing phosphate application would likely decrease
available phosphate. Thus, periodic soil analysis is required.
6.3 Management of Upland Soils
6.3.1 Organic Matter Application
In the Tohoku region, upland fields are often located on
Andosols generated from volcanic products. Additionally,
livestock farming is concentrated in Iwate Prefecture and on
the Pacific Ocean side of Aomori Prefecture. Therefore,
animal manure is mainly applied to the Andosol upland
fields. Although Andosols are characterized by a high
organic matter content, the application of organic matter on
these soils nevertheless has a positive effect on the soil
properties and crop growth. This section describes the
dynamics of applied organic matter in Andosols and its
effect on the formation of macroaggregates.
Generally, the level of SOM tends to decrease over time
when the soil is used as an upland field. Thus, it is necessary
to apply an appropriate amount of organic matter to the field
in order to maintain the level of SOM.
We investigated the effects of the continuous application
of cattle manure on the quantity and quality of SOM in an
Andosol (Aoyama and Kumakura 2001). Over a period of
20 years, surface soil samples were collected periodically
from plots treated with NPK and NPK + manure, with
application rates of 80, 160, and 320 Mg ha
−1 yr
−1 , at the
Tohoku Agricultural Research Center in Morioka. Particulate organic matter (POM, > 53 µm) and mineral-associated
organic matter (MAOM, < 53 µm) fractions were separated
from the soil samples by sieving after mechanical dispersion.
In the soil treated with only NPK, a significant decrease
in the concentration of total organic carbon (C), reaching up
to 10%, was observed after 20 years (Fig. 6.13). Although
the application of only NPK had no significant effect on the
amount of POM-C, the amount of MAOM-C decreased over
time. This indicates that the decrease in the concentration of
organic C in the soil treated with only NPK was due to a
decrease in the amount of MAOM.
6 Tohoku Region
203