puddling. In the background of these unfavorable soil
characteristics, no-tillage transplantation of rice was conducted. The recovery rate of fertilizer nitrogen was remarkably low due to the surface fertilization of basal dressing in
the no-tillage cultivation system. Improving the method of
fertilization was necessary to address this problem.
(1) For no-tillage cultivation
The single application of fertilizer in a nursery box was first
reported by Sato and Shibuya (1991), who used a controlled
availability fertilizer (CAF). In this CAF, the sigmoidal
release properties of nitrogen were accurately controlled by a
resin film coating the fertilizer granules. By a single application of fertilizer in a nursery box, an amount of fertilizer
nitrogen was delivered in a controlled manner over time
corresponding to the requirements of rice plants throughout
an entire growing season, which makes the application of
nitrogen fertilizers to the field unnecessary.
The CAF in nursery boxes was applied to paddy fields at
the transplanting stage, where it came into contact with the
roots of rice seedlings. The CAF used in the study was a
sigmoid-type slow-release nitrogen fertilizer (N content:
40%). Negligible release of nitrogen was observed for about
30 days after the application of CAF to the nursery box;
thereafter, approximately 80% of the total nitrogen content
leached into the water at 25 °C within 70 days of the lag
period. Readily available fertilizer (e.g., ammonium sulfate
and urea) and CAF of the normal-type release, which elutes
immediately after application, cannot be used, because
abnormally high nitrogen concentration is present in the
nursery soil. Currently, the fertilizer used in our investigation (product name: “Naebako Makase”) is sold only for the
single application of fertilizer in a nursery box. The elution
during the seedling period (approximately 35 days in the
middle seedling stage) is insignificant. There is no abnormally high nitrogen concentration or spindly growth of
seedlings. Moreover, the topdressing of nitrogen fertilizer to
the nursery box during the seedling period can be omitted.
The single application of fertilizers in a nursery box can
supply the fertilizer through contact with the rootlets of the
seedlings. Therefore, the recovery rate of nitrogen fertilization applied to the field with the no-tillage transplanting of
rice was improved by the single application of fertilizer in a
nursery box (Kaneta et al. 1994a; Kaneta 1995). At first, the
CAF was completely mixed with the soil in a nursery box.
Then, we devised a method in which fertilizers were applied
in layers in the nursery box without mixing (Kaneta et al.
1994b).
(2) Characteristics of nitrogen release from fertilizer
In Akita Prefecture in the Tohoku region, the cumulative soil
temperature in the nursery boxes during the 34 days of the
rice-growing period was about 615 °C. The cumulative
nitrogen release from the CAF during this period was 2.8%
of its total nitrogen content. The nitrogen released during the
seedling period was exceedingly low, and thus nitrogen
topdressing to the nursery box was unnecessary. The effect
of temperature change on nitrogen release was minor. After
transplantation, the rate of nitrogen release from the CAF
increased during the tilling stage (cumulative soil temperature of 1000 °C) and the reduction division stage. After that
stage, the nitrogen release was extremely slow until the
Fig. 6.4 Temporal changes in d
15
N values of soil in a long-term field
experiment with repeated application of rice straw compost conducted
at Tohoku Agricultural Research Center, National Agriculture and
Food Research Organization located in Daisen, Akita, Japan. +RSC:
rice straw compost applied, −RSC: rice straw compost not applied,
+CF: chemical N fertilizer applied, −CF: chemical N fertilizer not
applied. Data source Nishida et al. (2007)
196
H. Fujii et al.
characteristics, no-tillage transplantation of rice was conducted. The recovery rate of fertilizer nitrogen was remarkably low due to the surface fertilization of basal dressing in
the no-tillage cultivation system. Improving the method of
fertilization was necessary to address this problem.
(1) For no-tillage cultivation
The single application of fertilizer in a nursery box was first
reported by Sato and Shibuya (1991), who used a controlled
availability fertilizer (CAF). In this CAF, the sigmoidal
release properties of nitrogen were accurately controlled by a
resin film coating the fertilizer granules. By a single application of fertilizer in a nursery box, an amount of fertilizer
nitrogen was delivered in a controlled manner over time
corresponding to the requirements of rice plants throughout
an entire growing season, which makes the application of
nitrogen fertilizers to the field unnecessary.
The CAF in nursery boxes was applied to paddy fields at
the transplanting stage, where it came into contact with the
roots of rice seedlings. The CAF used in the study was a
sigmoid-type slow-release nitrogen fertilizer (N content:
40%). Negligible release of nitrogen was observed for about
30 days after the application of CAF to the nursery box;
thereafter, approximately 80% of the total nitrogen content
leached into the water at 25 °C within 70 days of the lag
period. Readily available fertilizer (e.g., ammonium sulfate
and urea) and CAF of the normal-type release, which elutes
immediately after application, cannot be used, because
abnormally high nitrogen concentration is present in the
nursery soil. Currently, the fertilizer used in our investigation (product name: “Naebako Makase”) is sold only for the
single application of fertilizer in a nursery box. The elution
during the seedling period (approximately 35 days in the
middle seedling stage) is insignificant. There is no abnormally high nitrogen concentration or spindly growth of
seedlings. Moreover, the topdressing of nitrogen fertilizer to
the nursery box during the seedling period can be omitted.
The single application of fertilizers in a nursery box can
supply the fertilizer through contact with the rootlets of the
seedlings. Therefore, the recovery rate of nitrogen fertilization applied to the field with the no-tillage transplanting of
rice was improved by the single application of fertilizer in a
nursery box (Kaneta et al. 1994a; Kaneta 1995). At first, the
CAF was completely mixed with the soil in a nursery box.
Then, we devised a method in which fertilizers were applied
in layers in the nursery box without mixing (Kaneta et al.
1994b).
(2) Characteristics of nitrogen release from fertilizer
In Akita Prefecture in the Tohoku region, the cumulative soil
temperature in the nursery boxes during the 34 days of the
rice-growing period was about 615 °C. The cumulative
nitrogen release from the CAF during this period was 2.8%
of its total nitrogen content. The nitrogen released during the
seedling period was exceedingly low, and thus nitrogen
topdressing to the nursery box was unnecessary. The effect
of temperature change on nitrogen release was minor. After
transplantation, the rate of nitrogen release from the CAF
increased during the tilling stage (cumulative soil temperature of 1000 °C) and the reduction division stage. After that
stage, the nitrogen release was extremely slow until the
Fig. 6.4 Temporal changes in d
15
N values of soil in a long-term field
experiment with repeated application of rice straw compost conducted
at Tohoku Agricultural Research Center, National Agriculture and
Food Research Organization located in Daisen, Akita, Japan. +RSC:
rice straw compost applied, −RSC: rice straw compost not applied,
+CF: chemical N fertilizer applied, −CF: chemical N fertilizer not
applied. Data source Nishida et al. (2007)
196
H. Fujii et al.