application of manure on the aggregate composition in an
Andosol upland field (Aoyama and Taninai 1992). Aggregates of different sizes were separated by wet sieving from
soil samples collected from field plots that were amended
with cattle manure at rates of 0 to 200 Mg h
−1 for 4 years.
The results showed that the proportion of macroaggregates
increased with an increasing manure application rate. Furthermore, the application of manure increased the amount of
organic C in the macroaggregates. This indicates that
manure-derived organic matter accumulates as POM, which
contributes to the formation of macroaggregates. Macroaggregates are formed by the association of microaggregates
and POM (Aoyama et al. 1999). This association is considered to be due to the binding action of microbial mucilage
and fungal hyphae, with the POM acting as a substrate for
microorganisms (Aoyama 2015).
6.3.2 Watermelon Cultivation on Andosols
The cultivation of watermelon (Citrullus lanatus) in Yamagata Prefecture is mostly concentrated in its northeastern
part, in the Kitamurayama area. Here, 850 ha are under
watermelon cultivation (as of 2016) and 33,700 tons of
watermelons are grown annually. Located in the Murayama
Basin, which is surrounded by the Ōu Mountains and Dewa
Hills, Kitamurayama experiences a wide range of temperatures during summer and relatively heavy snowfall during
winter. Kitamurayama also receives relatively less rainfall
during the rainy season and is covered with volcanic soils
(Andosols) that are suitable for watermelon cultivation.
Watermelon cultivation in this area began in the 1960s.
Since then, technical advancements, such as row covers and
plastic mulch, together with the local soil characteristics and
Fig. 6.13 Changes in the
amounts of organic C in the
whole soil sample and the
particulate and mineral-associated
organic matter fractions.
Regressions shown by a solid line
are statistically significant at the
0.05 level, whereas those shown
by a dashed line are not
significant. ○, 0 Mg ha
−1 yr
−1
;
▲, 80 Mg ha
−1 yr
−1
; ■,
160 Mg ha
−1 yr
−1
; ◆,
320 Mg ha
−1 yr
−1
. Reprinted
from Aoyama and Kumakura
2002
6 Tohoku Region
205
Andosol upland field (Aoyama and Taninai 1992). Aggregates of different sizes were separated by wet sieving from
soil samples collected from field plots that were amended
with cattle manure at rates of 0 to 200 Mg h
−1 for 4 years.
The results showed that the proportion of macroaggregates
increased with an increasing manure application rate. Furthermore, the application of manure increased the amount of
organic C in the macroaggregates. This indicates that
manure-derived organic matter accumulates as POM, which
contributes to the formation of macroaggregates. Macroaggregates are formed by the association of microaggregates
and POM (Aoyama et al. 1999). This association is considered to be due to the binding action of microbial mucilage
and fungal hyphae, with the POM acting as a substrate for
microorganisms (Aoyama 2015).
6.3.2 Watermelon Cultivation on Andosols
The cultivation of watermelon (Citrullus lanatus) in Yamagata Prefecture is mostly concentrated in its northeastern
part, in the Kitamurayama area. Here, 850 ha are under
watermelon cultivation (as of 2016) and 33,700 tons of
watermelons are grown annually. Located in the Murayama
Basin, which is surrounded by the Ōu Mountains and Dewa
Hills, Kitamurayama experiences a wide range of temperatures during summer and relatively heavy snowfall during
winter. Kitamurayama also receives relatively less rainfall
during the rainy season and is covered with volcanic soils
(Andosols) that are suitable for watermelon cultivation.
Watermelon cultivation in this area began in the 1960s.
Since then, technical advancements, such as row covers and
plastic mulch, together with the local soil characteristics and
Fig. 6.13 Changes in the
amounts of organic C in the
whole soil sample and the
particulate and mineral-associated
organic matter fractions.
Regressions shown by a solid line
are statistically significant at the
0.05 level, whereas those shown
by a dashed line are not
significant. ○, 0 Mg ha
−1 yr
−1
;
▲, 80 Mg ha
−1 yr
−1
; ■,
160 Mg ha
−1 yr
−1
; ◆,
320 Mg ha
−1 yr
−1
. Reprinted
from Aoyama and Kumakura
2002
6 Tohoku Region
205