Influence of flooding levels on changes in c, n and weight of rice straw in a paddy soil

Journal of Biology, Agriculture and Healthcare
ISSN 2224-3208 (Paper) ISSN 2225
Vol.3, No.5, 2013
Influence of Flooding Levels on Changes in C, N and
1. Assessment Institute for Agricultural Technology (AIAT
Agricultural Research and Development (IAARD), Jl. Chr. Soplanit, Rumah Tiga Poka, Ambon,
2. Dharma Wacana Agricultural High School, Metro, Jl. Ken
* E-mail of the corresponding author: arivinrivaie@yahoo.com
Abstract
It is imperative to have a better understanding of the effects of different flooding levels in paddy soils on changes in
soil chemical properties, especially information on the N recovery and N mineralization when the rice straw is
incorporated into soil as a source of soil organic matter under tropic conditions, such as in Metro, Lampung. A
glasshouse study was carried out to deter
changes in carbon (C), nitrogen (N) contents and weight of rice straw incorporated into paddy soil. The treatments
were arranged in a completely randomized block design with six
the rice straw at the beginning of the trial was 33
flooding level of 10 cm the C content still decreased until 4 weeks after flooding. And
values tended to return to the initial values 8 weeks after flooding. Meanwhile, the N content at the beginning of the
trial was 0.56-0.60%. The N contents for all flooding levels increased with increasing time of observat
(1.34-1.48%). The C:N ratios for all flooding levels at the beginning of the trial greatly decreased until 2 weeks after
flooding. Thereafter, the ratios decreased slightly until 8 weeks after flooding. Furthermore, flooding level of 2.5 cm
gave the lowest weight of rice straw 8 weeks after flooding, whereas, flooding level of 10.0 cm gave the highest
weight of rice straw, suggesting that the lesser the flooding level, the faster the litter decomposition rate. This
confirms other findings that at the de
the litter decomposed most rapidly.
Keywords: Flooding levels, decomposition, C, N, rice straw
1. Introduction
In many Asian rice producing countries, such as in Indonesia, t
is the elimination of straw by open-
reduce disease and pest (Ponnamperuma 1984), but, this practice may also results in gree
particulate matter (Cao et al. 2008). After harvesting paddy rice, large quantities of rice straw were produced from
paddy fields as an agricultural waste, amounting 2
the rice straw into the paddy soil has been widely accepted to be an alternative to burning of the straw (Cassman &
Pingali 1995), although long-term experiments on continuous irrigated rice systems in the tropics reported that it may
reduce rice yields (Cassman et al. 1995).
In paddy soil, soil organic matter (SOM) mainly results from plant litter and biomass (Quideau 2002; Sahrawat 2004)
and this consisted of two types of compounds, namely non
substances (Quideau 2002). Studies have reported that SOM is one of important sources of N in paddy ecosystems
and several factors, including rice straw application influenced the accumulation of N in paddy rice soils
(Ponnamperuma 1984; Golhaber & Kaplan 1995; Sundares
reported that the soil under flood fallow receiving application of rice straw significantly had higher N content
compared to the soil under dry fallow without any rice straw application.
Castillo et al. (1992) found that reducing the amount of water
reduced rice growth and yields. In addition, De Datta (1981) reported that the water should be available enough
along the rice growing season to avoid yiel
208 (Paper) ISSN 2225-093X (Online)
80
Influence of Flooding Levels on Changes in C, N and
Straw in a Paddy Soil
A. Arivin Rivaie1*
, Soni Isnaini2
ssment Institute for Agricultural Technology (AIAT-BPTP) - Maluku of Indonesian Agency for
Maluku, Indonesia
Dharma Wacana Agricultural High School, Metro, Jl. Kenanga No. 3 Mulyojati 16C Kota Metro,
Lampung, Indonesia
mail of the corresponding author: arivinrivaie@yahoo.com
mical properties, especially information on the N recovery and N mineralization when the rice straw is
glasshouse study was carried out to determine the effects of different flooding levels (2.5, 5.0, 7.5, and 10.0 cm) on
were arranged in a completely randomized block design with six replications. The results showed that C content of
the rice straw at the beginning of the trial was 33–40%. These values decreased 2 weeks after flooding except for the
flooding level of 10 cm the C content still decreased until 4 weeks after flooding. And then for all flooding levels the
0.60%. The N contents for all flooding levels increased with increasing time of observat
1.48%). The C:N ratios for all flooding levels at the beginning of the trial greatly decreased until 2 weeks after
west weight of rice straw 8 weeks after flooding, whereas, flooding level of 10.0 cm gave the highest
confirms other findings that at the depth of 1-2 cm below water surface of a paddy field are an aerobic zone, where
the litter decomposed most rapidly.
looding levels, decomposition, C, N, rice straw
In many Asian rice producing countries, such as in Indonesia, the management practice of post
-air burning to accelerate the growing season. Burning the straw may control or
reduce disease and pest (Ponnamperuma 1984), but, this practice may also results in gree
. 2008). After harvesting paddy rice, large quantities of rice straw were produced from
paddy fields as an agricultural waste, amounting 2-9 t/ha (Becker et al. 1994; Cao et al. 2008). The incorporation of
rice straw into the paddy soil has been widely accepted to be an alternative to burning of the straw (Cassman &
term experiments on continuous irrigated rice systems in the tropics reported that it may
. 1995).
and this consisted of two types of compounds, namely non-humic substances, such as carbohydrates, and humic
ideau 2002). Studies have reported that SOM is one of important sources of N in paddy ecosystems
(Ponnamperuma 1984; Golhaber & Kaplan 1995; Sundareshwar et al. 2003). Furthermore, Olk
compared to the soil under dry fallow without any rice straw application.
(1992) found that reducing the amount of water-use for lowland paddy rice production significantly
along the rice growing season to avoid yield reduction. For instance, soil moisture content of
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Influence of Flooding Levels on Changes in C, N and Weight of Rice
Maluku of Indonesian Agency for
anga No. 3 Mulyojati 16C Kota Metro,
mail of the corresponding author: arivinrivaie@yahoo.com
mical properties, especially information on the N recovery and N mineralization when the rice straw is
mine the effects of different flooding levels (2.5, 5.0, 7.5, and 10.0 cm) on
replications. The results showed that C content of
40%. These values decreased 2 weeks after flooding except for the
then for all flooding levels the
0.60%. The N contents for all flooding levels increased with increasing time of observation
1.48%). The C:N ratios for all flooding levels at the beginning of the trial greatly decreased until 2 weeks after
west weight of rice straw 8 weeks after flooding, whereas, flooding level of 10.0 cm gave the highest
2 cm below water surface of a paddy field are an aerobic zone, where
he management practice of post-harvest rice residues
air burning to accelerate the growing season. Burning the straw may control or
reduce disease and pest (Ponnamperuma 1984), but, this practice may also results in greenhouse gases and
. 2008). After harvesting paddy rice, large quantities of rice straw were produced from
. 2008). The incorporation of
rice straw into the paddy soil has been widely accepted to be an alternative to burning of the straw (Cassman &
term experiments on continuous irrigated rice systems in the tropics reported that it may
humic substances, such as carbohydrates, and humic
ideau 2002). Studies have reported that SOM is one of important sources of N in paddy ecosystems
2003). Furthermore, Olk et al. (1996) also
use for lowland paddy rice production significantly
d reduction. For instance, soil moisture content of -50 kPa (slightly above

Vol.3, No.5, 2013
field capacity) may result in yield reduction by 20
centimetre of water in their paddy fields. However, this condition
of the limited O2 supply and the increase of anaerobic microorganism that decay plant residues (Courreges 2004).
Oxygen is one of most important factors controlling the decomposition of organic matter in
flooded soils which increases oxygen availability increases the rates of soil organic matter decomposition and N
mineralization (Sahrawat 1983). Meanwhile, Howeler & Bouldin (1971) noted that lack of oxygen in submerged soil
resulted in lower rate of organic matter decomposition. Therefore, it is imperative to have a better understanding of
the effects of different flooding levels in paddy soils on changes in soil chemical properties, especially information
on the N recovery and N mineralization when the rice straw is returned to the soil as a source of SOM. This
information is important to determine feasible water management practices that suitable for rice growth and yield in
lowland paddy fields where the abundant straw is incorpo
Lampung. The objectives of this study were to determine the effects of different flooding levels on the carbon (C),
nitrogen (N) contents and weight of rice straw incorporated into a paddy soil
2. Materials and Methods
2.1 Trial Design and Conduct
This pot trial was carried out to observe the effects of different flooding levels (2.5, 5.0, 7.5, and 10.0 cm) on a paddy
soil. The treatments were replicated six times in a completely randomized bl
treatment was composed of 10 pots for the observations made every 2 (two) weeks and ended 8 (eight) weeks after
flooding (in accordance with the age of rice to reach the panicle initiation).
Two weeks before the trial was started, a bulk sample of soil was taken from a well
of 0-10 cm, in Metro, Lampung, Indonesia in June, 2008. Air
was decomposed. Ten kilograms of soil (absolute dry wei
ion-free water. Afterwards, the soil was stirred to form slurry (rice field soil conditions). Rice straw as organic
material was cut to the size of 2-3 cm. The rice straw was dried in an open room. Ten
to absolute dry weight) were inserted into the nylon bag (10 cm x 15 cm) (Armbrust 1980). The nylon bags were
placed at a depth of 5 cm below the soil surface. The weight decrease of rice straw biomass was calculated based o
the initial weight of the straw (air-dry weight). The measurement was done every two weeks until the period of 56
days to determine the content of total soil N and C from each pot.
2.2 Statistical Analysis
Data were subjected to analysis of variance (ANO
used when the ANOVA results indicated that there were significant treatment effects (Steel
3. Results and Discussion
The result of the initial soil analysis showed that the rat
in the paddy soil was progressing well. In addition, the value of N
was very low. This is likely that the farmers always burn their rice straw.
3.1 Changes in C
Carbon (C) is the major element of organic compounds in plant tissue. Figure 1 shows that the content of C at the
beginning of the experiment ranged from 33% to 40%. For the flooding levels of 2.5, 5.0, and 7.5 cm, the C content
decreased to approximately 30% until 2 weeks after flooding, and then it increased again. Whereas, for the flooding
level of 10.0 cm the C content slightly decreased to about 33% until 4 weeks after flooding, and then it increased
again. The dynamics of the C conten
in general, the content of C for all treatments decreased again. This indicated that there was a reduction in C content
for each observation time.
81
field capacity) may result in yield reduction by 20-25. In general, to control weeds most of farmers keep several
centimetre of water in their paddy fields. However, this condition results in an adverse affect on rice growth because
Oxygen is one of most important factors controlling the decomposition of organic matter in
ed in lower rate of organic matter decomposition. Therefore, it is imperative to have a better understanding of
ineralization when the rice straw is returned to the soil as a source of SOM. This
lowland paddy fields where the abundant straw is incorporated into the soil under tropic conditions, such as in Metro,
nitrogen (N) contents and weight of rice straw incorporated into a paddy soil.
soil. The treatments were replicated six times in a completely randomized block design in a glasshouse. Each
flooding (in accordance with the age of rice to reach the panicle initiation).
tarted, a bulk sample of soil was taken from a well-irrigated paddy field at soil depth
10 cm, in Metro, Lampung, Indonesia in June, 2008. Air-dry soil was used as the medium where the rice straw
was decomposed. Ten kilograms of soil (absolute dry weight) were inserted into the pot, and then flooded with
free water. Afterwards, the soil was stirred to form slurry (rice field soil conditions). Rice straw as organic
3 cm. The rice straw was dried in an open room. Ten grams of the straw (equivalent
placed at a depth of 5 cm below the soil surface. The weight decrease of rice straw biomass was calculated based o
dry weight). The measurement was done every two weeks until the period of 56
days to determine the content of total soil N and C from each pot.
Data were subjected to analysis of variance (ANOVA). The least significant difference (LSD) test at p < 0.05 was
used when the ANOVA results indicated that there were significant treatment effects (Steel
The result of the initial soil analysis showed that the ratio of C:N was 6.11 (below 15), indicating that mineralization
in the paddy soil was progressing well. In addition, the value of N-total in the soil (0.58%) prior to the experiment
was very low. This is likely that the farmers always burn their rice straw.
to approximately 30% until 2 weeks after flooding, and then it increased again. Whereas, for the flooding
again. The dynamics of the C content for each treatment varied with observation time. At the end of the experiment,
www.iiste.org
25. In general, to control weeds most of farmers keep several
results in an adverse affect on rice growth because
Oxygen is one of most important factors controlling the decomposition of organic matter in rice soils. Drainage of
ed in lower rate of organic matter decomposition. Therefore, it is imperative to have a better understanding of
ineralization when the rice straw is returned to the soil as a source of SOM. This
rated into the soil under tropic conditions, such as in Metro,
ock design in a glasshouse. Each
irrigated paddy field at soil depth
dry soil was used as the medium where the rice straw
ght) were inserted into the pot, and then flooded with
free water. Afterwards, the soil was stirred to form slurry (rice field soil conditions). Rice straw as organic
grams of the straw (equivalent
placed at a depth of 5 cm below the soil surface. The weight decrease of rice straw biomass was calculated based on
dry weight). The measurement was done every two weeks until the period of 56
VA). The least significant difference (LSD) test at p < 0.05 was
used when the ANOVA results indicated that there were significant treatment effects (Steel et al. 1997).
io of C:N was 6.11 (below 15), indicating that mineralization
total in the soil (0.58%) prior to the experiment
to approximately 30% until 2 weeks after flooding, and then it increased again. Whereas, for the flooding
t for each treatment varied with observation time. At the end of the experiment,

Vol.3, No.5, 2013
Fig 1. Dynamics of C
3.2 Changes in N
At the beginning of the experiment, the N content ranged from 0.56% to 0.60% (Figure 2). By the time the content of
N in the incorporated rice straw increased until 8 weeks after
increased only until 6 weeks after flooding, and then it decreased again.
Fig 2. Dynamics of N content in the rice straw under different flooding levels
25.00
27.50
30.00
32.50
35.00
37.50
40.00
42.50
0
C(%)
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0
N(%)
82
Dynamics of C content in the rice straw under different flooding levels
N in the incorporated rice straw increased until 8 weeks after flooding, except for the flooding level of 2.5 cm, it
increased only until 6 weeks after flooding, and then it decreased again.
Dynamics of N content in the rice straw under different flooding levels
2 4 6 8
Time (weeks)
2.5 cm 5.0 cm
7.5 cm 10.0 cm
2 4 6 8
Time (weeks)
2.5 cm 5.0 cm
7.5 cm 10.0 cm
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content in the rice straw under different flooding levels
flooding, except for the flooding level of 2.5 cm, it
Dynamics of N content in the rice straw under different flooding levels

Vol.3, No.5, 2013
3.3 Ratio of C:N
In addition to C and N, the observation of C:N ratio is also one of important variables to measure decomposition of
organic matters. At the beginning of the study, the ratio of C:N ranged from 56.5 to 67 (Figure 3). After 2 weeks after
flooding, the ratio of C:N decreased by 83
However, thereafter the ratio of C:N decreased slightly.
Fig 3. Dynamics of C:N ratio in the rice straw under different flooding levels
3.4 Weight of rice straw
The results in Table 1 showed that, in general, there was no difference in the weight of rice straw for the observation
at 2 until 4 week after flooding. However, at 6 and 8 weeks after flooding, there were significant differences in the
weight of the rice straw, especially b
the flooding level, the faster the organic matter decomposition rate.
Table 1. Change in rice straw weight (g) under different flooding levels
Flooding
Levels (cm) 0ns
2.5 9.63
5.0 9.63
7.5 9.50
10.0 9.70
CV (%) 3.05
Notes: 1
Numbers within the same column followed by the same letters are not significantly different at
p<0.05
Weight reduction of organic material at the end of the experiment generated by the flooding level of 2.5 cm was
significantly different from the flooding level of 7.5 and 10.0 cm, indicating that the paddy soils flooded by 2.5 cm
had a higher rate of organic matter weight reduction compared to the soils flooded by the deeper flooding (>5 cm).
This could be related to the balance between oxygen in atmosphere with oxygen in the oxidation layer of the paddy
soil. According to Sanchez (1976), the layer of 0
Ponnamperuma (1972) stated that in the waterlogge
20
25
30
35
40
45
50
55
60
65
70
0 2
C:Nratio
2.5 cm
7.5 cm
83
, the observation of C:N ratio is also one of important variables to measure decomposition of
flooding, the ratio of C:N decreased by 83-120%, indicated by a very steep line (ratio of C:N ranged 31
However, thereafter the ratio of C:N decreased slightly.
Dynamics of C:N ratio in the rice straw under different flooding levels
1 showed that, in general, there was no difference in the weight of rice straw for the observation
weight of the rice straw, especially between the flooding level of 2.5 cm and 10.0 cm. This indicated that the thinner
the flooding level, the faster the organic matter decomposition rate.
Table 1. Change in rice straw weight (g) under different flooding levels
2ns
Time of flood (weeks)
4ns
6
8.23 7.10 4.37
8.82 7.33 4.67 a
8.53 7.43 4.70 a
8.50 7.30 5.20 b
6.82 6.41 5.91
ignificantly different from the flooding level of 7.5 and 10.0 cm, indicating that the paddy soils flooded by 2.5 cm
the balance between oxygen in atmosphere with oxygen in the oxidation layer of the paddy
soil. According to Sanchez (1976), the layer of 0-1 cm of the top of the rice field is an oxidation zone. Meanwhile,
Ponnamperuma (1972) stated that in the waterlogged soil, the layer 1-2 cm is an oxidation layer. This is one reason
4 6 8
Time (weeks)
2.5 cm 5.0 cm
7.5 cm 10.0 cm
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, the observation of C:N ratio is also one of important variables to measure decomposition of
120%, indicated by a very steep line (ratio of C:N ranged 31-37).
Dynamics of C:N ratio in the rice straw under different flooding levels
1 showed that, in general, there was no difference in the weight of rice straw for the observation
etween the flooding level of 2.5 cm and 10.0 cm. This indicated that the thinner
6 8
4.371
a 1.90 a
4.67 a 1.97 a
4.70 a 2.08 b
5.20 b 2.08 b
5.91 3.67
ignificantly different from the flooding level of 7.5 and 10.0 cm, indicating that the paddy soils flooded by 2.5 cm
the balance between oxygen in atmosphere with oxygen in the oxidation layer of the paddy
1 cm of the top of the rice field is an oxidation zone. Meanwhile,
2 cm is an oxidation layer. This is one reason

Vol.3, No.5, 2013
why aerobic microorganisms are capable to utilize organic materials as a source of energy. In accordance with the
findings of Ponnamperuma (1972), Watanabe (1984) also reported that floodin
rate of decomposition of organic material. In the present study, for each flooding level, the weight of the rice straw
decreased obviously, especially from 6 to 8 weeks after flooding, suggesting that the decompositi
The obvious loss of the straw weight is likely related to the release of carbon dioxide (CO
nutrients and re-synthesized organic carbon compounds during the decomposition process.
4. Conclusions
The different flooding levels of paddy soil had different effects on the decomposition rate of rice straw incorporated
into the soil. The flooding level of 2.5 cm resulted in the highest decrease of the straw weight, suggesting that under
conditions of flooding level about 2.0 cm, the rice straw spread on the paddy soil surface would be decomposed more
rapidly than deeper flooding levels. To have a better management of the rice straw, in practical applications, rice
straw supposed to be spread on the soil surface followed b
Acknowledgement: The first author thanks Umar Bamualim of BPTP Maluku for his suggestions on the
manuscript.
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