IJERD – International Journal of Environmental and Rural Development (2020) 11-2

Research article
erdChanges in Soil Physical and Chemical Properties with
Depth due to Megascolicidae Movements
TAKANORI KANEKO
Graduate School of Agriculture, Tokyo University of Agriculture, Japan
Email: taka1504kaneko@gmail.com

TOMONORI FUJIKAWA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Japan
Email: t3fujika@nodai.ac.jp

MACHITO MIHARA
Faculty of Regional Environment Science, Tokyo University of Agriculture, Japan
Received 29 April 2020

Accepted 12 December 2020(*Corresponding Author)

Abstract Earthworms have significant impacts on the physical and chemical properties ofsoils. It is known that they are remarkably improving soil fertility as well as promoting plant
growth because earthworms make castings, which are rich in nitrogen, phosphorus and othernutrients. Additionally, earthworm’s movements effects soil properties by their movementsin the soil, notably soil aggregates, nitrogen and phosphorus concentration. Earthworms from
Megascolecidae family are a major earthworms found in Japan, but there is lack of knowledge
on its effect on soil properties compared to other earthworms. Subsequently, this study
discusses the changes in soil aggregates, nitrogen and phosphorus concentration changes withdepth due to Megascolicidae movements in the soil. An experiment was conducted using
cylindrical columns of 12 cm height divided into 3 layers at 4 cm interval. Additionally, twogroups were made, with litter and without litter, which were divided into subgroups withvariations in earthworm numbers. The results of aggregates showed the tendency of aggregate
formation in both the groups, with high formation rate in litter added group. The results of
NO3 and P2O5 content significantly differed among the 3 layers in the treatments. The trendof higher NO3-N and P2O5 concentration was observed in middle layer and lower layer
respectively. According to the results obtained, Megascolicidae movements effect the
distribution of nutrients in subsurface soils.
Keywords Megascolecidae, earthworm movements, soil chemical and physical properties

INTRODUCTION
It is known that earthworms improve soil structure and enhance soil productivity (Barley, 1959b;
Lee and Foster, 1991). They promote transport of nutrients and ions in subsurface soil with theirbodily movements.
Earthworms are broadly divided into two families, Lumbricidae and Megascolicidae.
Earthworms form Lumbricidae family are found in the area from temperate to polar regions ofEurope and Asia and those from Megascolicidae family are found in the area from tropical totemperate zones of East and South East Asia. Further, ecologists divide them into three groups into
anenic, epigiec and endogeic earthworms based on their habitual preferences (Bouche, 1977). Anenic
earthworms are large species, which dig and inhabit upright, make deep burrows in soil and come tosurface for feeding. Epigiec earthworms are small species, which lives and feeds on the surface ofsoil. Many literatures have been made on earthworm from Lumbricidae family on the effects of theiractivity to the soil properties. Langmaack et al., 1999, estimated that earthworm from Lumbricidae
family (Lumbricus terrestris) makes 82.3 km/ha of burrows in the agricultural field. These burrows
increase air and water permeability, transport oxygen and water and better penetration of roots of thesoil (Kavdir and Ilay, 2011). In these literatures, many researches were concentrated on the nutrientⒸ ISERD

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availability in the casts on soil surface and the large part of the effects of these casts were clarified,
but the knowledge of the effects of the cast in subsurface soil (12 cm depth) which will havesignificant roles on plant growth was limited. Therefore, this study tries to discuss the effects on soil
physical and chemical properties in different layers of subsurface soil released by epigiec earthworm
movements in subsurface soil.
OBJECTIVE
The objective of this study is to assess the changes in soil aggregates, nitrogen and phosphorus
contents with depth due to movements by epigiec earthworm from Megascolicidae family.
METHODOLOGY
Sampling of Earthworms, Soil and Litter
Epigeic earthworms from Megascolicidae family (Fig. 1) were collected from depth up to 10 cm soil
using hand-sorting method. The soil used in this experiment was Andosol, which are volcanic soils
and covers 47% of land area in Japan. The soil was passed through 2 mm sieve (Fig. 2). Litter wascollected from fallen leaves of oak and cereus trees (Fig. 3). The leaves were made into small pieces
before using it. All the samples were collected from the same field in Kanagawa prefecture, Japan.

Fig. 1 Megascolicidae used inthis study

Fig. 2 Soil used in the study Fig. 3 Litter used inthis study

Experimental Set-up and Conditions
Cylindrical columns of size 15 cm in diameter and 12 cm in height were used having surface area of
0.000018 m2 for the experimental apparatus. In the experiments, the depth of soil was set 12 cm. The
apparatus could be separated into three layers with intervals of 4 cm (Fig. 4). In this experiment, 0-4
cm is assumed as the subsurface soil. The experiments were conducted for 28 days in an incubator
whose temperature was set at 17.1 ℃ ± 0.5 ℃ which is similar to the annual average temperature of
the area where soil and litter were sampled.
In this experiment, 1.8 kg of soil was used. Patterns of soil organic matter content were set into
two groups of 0% added litter and 5% added litter. Each group was further divided into threetreatments with 0, 3 and 10 earthworms (Table 1). This experiment was designed with assuming thedensity of 1 earthworm per one column corresponding approximately 56 earthworms per one hectare.
Soil and litter were mixed thoroughly for litter added group. The three column treatments were named
from A1 to A3 for litter added group. Likewise, for 5% added litter group, treatments were named
from B1 to B3 (Table 1).
The soil in the column was saturated before the start of the experiment by capillary action for
24 hours. After saturation, the excess water was released by gravity for 24 hours. Earthworms wereput on the surface of the soil in the start of the experiment. The moisture content of soil for eachtreatment was maintained at 50 to 60%. To maintain the water content, weight of the treatments wasmeasured on daily basis and equal to lost amount of water was added.

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15 cm

4 cm

12 cm

Fig. 4 Schematic diagram ofcylindrical columns

Fig. 5 Column used in this study

Table 1 Column treatment patterns
Litter added (%)

05

Number of earthworms /cylindrical columns

Treatments

0

A1

3

A2

10

A3

0

B1

3

B2

10

B3

Sampling and Parameters Measured
Soil was sampled on 0, 7, 14 and 28 days from the start of the experiments from each layer of 0 to 4
cm, 4 to 8 cm and 8 to 12 cm randomly at 6 different points. The samples were analyzed for water
stable aggregate using Yoder’s method (Yoder, 1936), total available phosphorus using Troug
method (Troug, 1930) and Nitrate nitrogen using Cataldo method (Cataldo et al., 1975).
RESULTS AND DISCUSSION
Survival of Earthworms at Different Layer of Soil
Table 2 shows the change in survival of earthworms at the depth of 0 to 4, 4 to 8 and 8 to 12 cm in
0% and 5 % added litter group at 28 days of experiment. There was no earthworm found in 0 to 4 cm
layer in all the groups. The number of earthworms increased with depth. In 0% added litter group,
most earthworms were present at 4 to 8 cm layer. Whereas, in 5% added litter group, a greater numberof earthworms were present in 8 to 12 cm layer. In B3, 12 earthworms were seen at 28 days, forwhich an assumption was made that new earthworms were born. With the obtained results, it wasproved that the epigiec earthworm from Megascolicidae family used for this study are active insubsurface soil.
Table 2 Result of survival of earthworm at different layer of soil at 28 days
Layer (cm)

A2

A3

B2

B3

0~4

0

0

0

0

4~8

2

7

2

4

8~12

1

2

1

8

Total

3

9

3

12

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Periodic Change in Water Resistant Aggregate
The ratio of 2 mm water resistant aggregates increased with time in all layers of the treatments forboth the groups (Figs. 6, 7 and 8). High aggregate content was seen in 4 to 8 and 8 to 12 cm layers
wherethe larger number of earthworms existed. Similarly, the Mean Weight Diameter (MWD) of
100%
aggregates increased in 4 to 8 and 8 to 12 cm layers with time (Figs. 9, 10, 11 and 12). Group B
having added litter content increased aggregates content in all the three layers. It could be explainedby 80%
the activation of earthworm metabolism by the litter, which provided nutrient to the earthworm.
100%

100%

Percentage of aggregates

Percentage of aggregates

60%

80%

40%

80%

＜0.1 mm60%＜0.1 mm60%0.25＞d≧0.1 mm

20%0.25＞d≧0.1 mm

0.5＞d≧0.25 mm

40%

0%
20%

40%

0.5＞d≧0.25 mm

1＞d≧0.5 mm

1＞d≧0.5 mm

2＞d≧1 mm

2＞d≧1
mm
20%

B1
≧2 mm

0 day

0%
0 day

≧2 mm
80%

B3

≧2 mm

28 day

0%
A1

100%

B2

A2

A3

B1

28 day2＞d≧1 mm0 day

1＞d≧0.5 mm

B2B328 day0.5＞d≧0.25 mm＜0.1 mm0.25＞d≧0.1 mm

Fig. 6 Changes in aggregate percentage at 0 to 4 cm depth in A and B

100%

100%

80%

Percentage of aggregates

Percentage of aggregates

60%
80%

＜0.1 mm

40%
60%

20%

40%

0.25＞d≧0.1
mm
60%＜0.1 mm0.5＞d≧0.25 mm

0.25＞d≧0.1 mm

40%0.5＞d≧0.25 mm

1＞d≧0.5 mm

0%
20%

20%

B2

≧2 mm

0 day
0%

2＞d≧1 mmB3

28 day

≧2 mm

0%
A1

0 day

100%

1＞d≧0.5 mm

2＞d≧1 mm

B1

≧2 mm

A2

A3

B1

28 day2＞d≧1 mm0 day

1＞d≧0.5 mm

0.5＞d≧0.25 mm

B2

B3

28 day＜0.1 mm0.25＞d≧0.1 mm

Fig. 7 Changes in aggregate percentage at 4 to 8 cm depth in A and B
80%
100%

100%

Percentage of aggregates

Percentage of aggregates

60%
80%

40%

60%

20%40%
0%20%

80%

60%

＜0.1 mm＜0.1 mm0.25＞d≧0.1 mm

0.25＞d≧0.1 mm

40% mm0.5＞d≧0.25

0.5＞d≧0.25 mm

1＞d≧0.5 mm

1＞d≧0.5 mm

20%
2＞d≧1
mm

B1
0 day

0%

0%
A1

0 day

≧2 mm

A2

2＞d≧1 mm

B2

≧2 mm

1＞d≧0.5 mm≧2 mm

28 day

A3

B1
0 day

28 day2＞d≧1 mmB3

0.5＞d≧0.25 mm

B2
28 day0.25＞d≧0.1 mm＜0.1 mmFig. 8 Changes in aggregate percentage at 8 to 12 cm depth in A and BⒸ ISERD

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The results of this study show that earthworm feeds on soil and litter and releases them in theform of casts. The released casts by the assimilation with soil to form aggregates of 2 mm or larger.
This has been also showed in laboratory conditions by Kawaguchi et al., 2011, and in field conditions
by Marinissen and Hillenaar, 1997; Ketterings et al., 1997 and Arai et al., 2013. In addition,
Kawaguchi et al., 2011, found that 92% of casts weight had 2 mm or more water-resistant aggregates.
MWD (mm)

MWD (mm)0day
7day・B1
7day・B2

7day・A1
7day・A2
7day・A3
14day・A1

7day・B3

Depth (cm)Depth (cm)

0day

14day・B1

14day・B2
14day・B3

28day・B1
28day・B2

14day・A2

28day・B3

14day・A3
28day・A1

28day・A2
28day・A3

Fig. 9 Periodic changes of MWD content
in A1 to A3

Fig. 10 Periodic changes of MWD content
in B1 to B3

MWD(mm)a**b**

MWD (mm)

b**

b**

a**

b**

A**

B**

B**

0day

Depth (cm)Depth (cm)

0day

28day・B1
28day・B2
A**

B**

B**

28day・B3

28day・A1
28day・A2
α**

β**

β**

28day・A3

α*, **

Significant difference at ** p<0.01, * : p<0.05

Fig. 11 MWD content in A1 to A3
at 0 and 28 daysb*, **

b**

Significant difference at ** p<0.01, * : p<0.05

Fig. 12 MWD content in B1 to B3
at 0 and 28 days

Periodic Changes in Nitrate Nitrogen Content
The nitrate nitrogen content became higher in all three layers of treatment A2 and A3, with A3
showing comparative high nitrate nitrogen content as shown in Fig. 13. Similarly, the nitrate nitrogencontent in 5% added litter treatment B3, increased with time (Fig. 14). Nitrate nitrogen content was
highest in treatment B3 in 28 days of experiment (Fig. 16). The highest value was observed in layerof 0 to 4 cm in B3. This increase of nitrate nitrogen content could be explained by nitrification oforganic matter enhanced by microbial action present in casts of earthworms. As, B3 had the highest
amount of organic matter, it is speculated that earthworm activity was highest in this treatment,
resulting in excretion of casts and higher microbial activity. In this process, organic nitrogen getsconverted to NH4-N to NO2-N, which further changes into NO3-N. NH4-N is converted to NO2-N by
the action of ammonia oxidizing bacteria. Whereas, NO2-N is converted into NO3-N by the action of
nitrite oxidizing bacteria. Nitrifying bacteria are aerobic microbes and are active near surface of soils(Ward, 2008) which supports the result of this study where nitrate nitrogen content was high in upper
layer of soil compared to lower layers. According to Su et al., 2017, Amynthas corticis from
Megascolicidae family has nitrifying bacteria in casts. The results with high nitrate nitrogen content
in treatment with high litter content can be discussed with the fact that nitrifying bacteria gets
attached in the surface of the litter.
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NO3-N (mg/100 g)

NO3-N (mg/100 g)

Depth (cm)0day

Depth (cm)

7day・A1
7day・A2
7day・A3
14day・A1

0day

7day・B1
7day・B2
7day・B3

14day・A2

14day・B1

14day・A3

14day・B2

28day・A1

14day・B3

28day・A2

28day・B1

28day・A3

28day・B2
28day・B3

Fig. 13 Periodic changes of NO3-N content
in A1 to A3

Fig. 14 Periodic changes of NO3-N content
in B1 to B3NO3-N (mg/100 g)

b**

A**

a**

c**

B**

b**

a**

Depth (cm)Depth (cm)a**NO3-N (mg/100 g)

C**

A**

A**

B**
0day

0day
28day・B1

28day・A1

α**

β**

γ**

28day・A2

α**α**28day・B2

β**28day・A3

28day・B3

Significant difference at ** : p<0.01, * : p<0.05

Significant difference at ** : p<0.01, * : p<0.05

Fig. 15 NO3-N content in A1 to A3 at 28 days Fig. 16 NO3-N content in B1 to B3 at 28 days
Periodic Change in Total Available Phosphorus
High content of total phosphorus in lower layers of column was observed for treatment A3 and B3
contrasting to the results of nitrate nitrogen (Figs. 17 and 18).
P2O5 (mg/100 g)

P2O5 (mg/100 g)

0day
7day・B1
7day・B2

7day・A1
7day・A2
7day・A3

7day・B3

Depth (cm)Depth (cm)

0day

14day・B1
14day・B2
14day・B3

28day・B1

14day・A1

28day・B2

14day・A2

28day・B3

14day・A3
28day・A1
28day・A2
28day・A3

Fig. 17 Periodic changes of P2O5 content
in A1 to A3

Fig. 18 Periodic changes of P2O5 content
in B1 to B3

This tendency can be linked with high presence and activity of earthworm in lower layers. It is
speculated that high phosphorus content is caused by high phosphatase activity in earthworm casts.
High phosphatase activity results in increased inorganic phosphorus released by mineralization oforganic phosphorus. Satchell and Martin, 1984 reported high level of phosphatase activity inearthworm casts of Aporrectodea trapezoides, an earthworm from Lumbricidae family. The resultsof laboratory experiments conducted by Matsumoto and Taniguchi, 1995, hypothesized highphosphatase occurrence in earthworm leading to high phosphatase activity in earthworm casts andsurrounding soils.
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P2O5 (mg/100 g)

a**

b**

P2O5 (mg/100 g)

a**

b**

b**, *

c**, *
0day

A**

C**, *

Depth (cm)Depth (cm)

28day・B1

B**, *

28day・B2

A**

B**

C**

28day・B3

0day
28day・A1

α**

β**

γ**

28day・A2

α**

β**

α**

28day・A3

Significant difference at ** : p<0.01, * : p<0.05

Fig. 19 P2O5 content in A1 to A3
at 0 and 28 days

Significant difference at ** : p<0.01, * : p<0.05

Fig. 20 P2O5 content in B1 to B3
at 0 and 28 days

CONCLUSION
This study was conducted to clarify the effects of epigiec earthworm from Megascolicidae family on
soil aggregates, nitrogen and phosphorus content with their ecological behavior in subsurface soil
using column treatment in incubator. Survival rate of earthworm at different layers resulted in highearthworm number between 4 to 8 and 8 to 12 cm deep, irrespective of litter content. Water resistantaggregates (larger than 2 mm) and MWD increased with time, where the earthworm numbers were
high. Similarly, available phosphorus content was high in the layer with high earthworm numbers.
This increase can be explained with phosphatase activity in earthworm casts. High phosphataseactivity results in increased inorganic phosphorus released by mineralization of organic phosphorus.
Whereas, nitrate nitrogen was high in the upper layer having less number of earthworm. The resultsof nitrate nitrogen content would be due to the presence of nitrifying bacteria in earthworm’s casts,
which are aerobic microbes and are active near surface of soils. With the obtained results, earthworm
activity and movement showed potential for growth and development of plant by enhancing soil
structure, increasing nitrogen and phosphorus content.
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