IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Research article
erd

Biochar Amendment to Different Paddy Soils on CH4
Production, Labile Organic Carbon, pH and Electrical
Conductivity Dynamics: Incubation Experiment
CHHIN PHY
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

KETSUDA DEJBHIMON
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

DAUNGSAMON TULAPHITAKFaculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

PHRUEKSA LAWONGSA
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

MATSA KEOPHILA
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

NIPA THAMMASOM
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

PATCHAREE SAENJAN*
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand
Email: patsae1@kku.ac.th
Received 12 October 2013

Accepted 1 March 2014(*Corresponding author)

Abstract Today biochar research in agriculture is worldwide interested to mitigate
greenhouse gas emission. Application of biochar in anoxic condition to different textured
paddy soils was proposed to study. We gave hypothesis that biochar rates in paddy soils
will correlate to the changing of CH4 production, soil labile organic carbon (LOC), pH andelectrical conductivity (EC), and their interactions. Biochar amendment rates, 6.25, 12.50,
18.75 and 25 t ha-1 were anaerobically incubated in loamy, clayey and loamy sand soils for
28 days. At the end of incubation, biochar amended loamy soils gave the highest
cumulative CH4 production followed by clayey and loamy sand soils. CH4 production wasenhanced by biochar amendment in loamy and clayey, but suppressed in loamy sand. The
highest cumulative CH4, 47.03 mg CH4-C kg-1, was produced from loamy soil with 12.50 t
ha-1 of biochar. The highest LOC was in clayey soil followed by loam and loamy sand in
all rates of biochar amendment. Biochar had tendency to enhance soil pH in loam, but not
in clay and loamy sand. In addition, highest EC was in clay, especially with 25 t ha-1 ofbiochar amendment, followed by loam and loamy sand. Through the whole of incubation,
biocahar amendment rates significantly negative correlated to CH4 production rates in all
soil textures. The positive correlations between LOC and biochar rates were found inclayey and loamy sand soils, while the former was highly significant. However, fluctuatedcorrelations were manifested in loamy soil. Furthermore, in loamy sand, the stronger
correlation between biochar rates, and both pH and EC, compared to loamy and clayeysoils. Biochar amendments suppressed CH4 production in loamy sand, but enhanced inloamy and clayey soil under anaerobic incubation. Further studies on biochar feasibility
should be trialed in paddy-field condition.
Keywords organic material, soil organic carbon, greenhouse gasⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2014) 5-1

INTRODUCTION
Rice paddy is an important distribution channel of anthropogenic greenhouse gas (GHG) emission,
which impacts to global warming or climate change aspects. CH4 production and emission fromsoil is derived from C mineralization, and widely documented with relation to the effect of soil
temperature, moisture, pH, Eh and plant cultivars (Zheng et al., 2007). In addition, soil labileorganic matter fractions are very important in vulnerable to transform and play crucial roles for C
and nutrient cycling, and perform a major role for source and sink of GHG change such as CO 2 andCH4 (Tian et al., 2013).
Biochar is a carbon rich by-product derived from thermal decomposition of organic matter
under pyrolysis system with low oxygen concentration promoted the potential for improving soil
properties (Denyes et al., 2012). Today biochar research in agriculture is worldwide interested tomitigate GHG emission such as CH4, or CO2 to environment. Therefore, this incubation experimentis established in a laboratory in order to identify the effectiveness of biochar amendment rates on
soil parameters and their interaction in different soil textures.
OBJECTIVE
To investigate CH4 formation, labile organic carbon (LOC), pH and EC dynamic characteristics
from application of different rates of biochar and their interactions in anoxic condition within
loamy, clayey and loamy sand paddy soils.
METHODOLOGY
Treatments, soils and incubation: The experiment was laid out in completely randomized design(CRD) in triplicate, incorporated with 0, 6.25, 12.50, 18.75 and 25 t ha -1 of biochar with 7.98 and0.94 dS m-1 of pH and EC respectively. Biochar derived from a 5 years old eucalyptus wood,
combusted at conventional kiln by 350 oC. The loamy, clayey and loamy sand soils were sampledfrom 0-15 cm depth in a paddy field in northeast of Thailand. More details of chemical andphysical properties of soils and biochar were shown in Table1. The soil was air dried, grinded andpassed through a 2 mm. sieve. Enough amount of soil sample was pre-submerged in deionizedwater for one week. Prior to the soil incubation, moisture content of the muddy soil was determined.
A weight of muddy soil used in this incubation trial was equivalent to 5 g of dried soil, wasplaced in a 60 ml serum bottle. The soil-biochar mixture with 15 ml of deionized water was shaken
by using vortex shaker in order to expel any gas bubbles in soil slurry, and flushed the head spacein the bottles by ejecting N2 (99.99%) gas with 1 bar pressure for 1 minute, the bottle was closed
immediately with butyl rubber stopper and aluminum crimp top seal. They were wrapped up withaluminum foil for protecting the light radiation.
Table 1 Basic chemical and physical properties of soils and biochar
Soils/biochar
Clay
Loam
Loamy sand
Biochar

Sand
(%)
2.53
50.00
84.14
-

Silt
(%)
17.31
36.70
11.95
-

Clay
(%)
80.26
13.30
3.91
-

BD
(g cm-3)
1.44
1.45
1.80
-

SOC
(%)
1.75
0.79
0.12
38.60

LOC
(g-C kg-1)
1.70
0.50
0.10
13.30

TN
(%)
0.16
0.07
0.02
0.50

C:N ratio
10.94
11.29
6.00
77.20

Gas samplings and soils analyses: Gas samplings were performed every week for 4 weeks.
Before the actual gas samplings, the incubated samples were flushed with N2 (99.99%) for 1 minute,sealed tight as mentioned previously and incubated again for 24 hours. One ml gas sample wastaken from the head space of incubation bottle using an air-tight syringe. The concentration of CH4
in the gas samples was analyzed with gas chromatograph (GC), Shimadzu GC2014, detector
temperature 200 oC (FID), injection port 150 oC, oven 180 o C, stainless steel column 2 m lengthⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2014) 5-1

packed with unibead C. Carrier gas is He and retention time is 2.25 minutes. To calculate the CH4
production was mentioned by Ro et al., (2011). Labile organic carbon (LOC) was analyzed bypermanganate-oxidation method (Moody and Cong, 2008). The actual soil pH and EC were
measured by pH and EC meters, respectively.
Statistical Analysis: The data collected was analyzed statistically using Analysis of Variance(ANOVA) technique and treatment means were compared by using Duncan’s Multiple Range Test
(DMRT) with SAS statistical program.

RESULTS AND DISCUSSION
Cumulative CH4 production: Biochar amendment significantly enhanced cumulative CH4
production accompanied with a large range (8.42 to 54.03 mg CH4-C kg-1) in loamy soil, and amoderate range (5.63 to 19.40 mg CH4-C kg-1) in clayey soil, when compared to its control withoutbiochar Aemicalon, but it decreased CH4 production with a very low range (0.31 to 0.86 mg CH4-C
kg-1) in amended loamy sand soil (Fig. 1, a). Biochar amendment rates significantly negative
correlated to CH4 production rates in all soil textures (Table 2). A quadratic regression
determination had identified that cumulative CH4 production was influenced by LOC in loam, but
not found in clay and loamy sand. While pH had impacts on cumulative CH4 production in clayey
and loamy sand, and EC had determined cumulative CH4 production in all types of soil (data notshown). Zhang et al. (2012) had given a report that methane emission over the whole rice growing
season was significantly increased by the rate of biochar amendment. Yu et al. (2012) also
confirmed that under the high soil moisture, 85 and 100% water filled pore space, biocharenhanced methane emission. In contrast, Feng et al. (2012) indicated that biochar amendment inpaddy soil decreased CH4 emission as well as Liu et al. (2011) had proved that application ofbiochar reduced methane emissions from the paddy soil. These findings agreed to our results which
CH4 productions were enhanced in loamy and clayey soils, but decreased in loamy sand soil
amended with biochar. Zhang et al. (2010) had emphasized that the degree of methane emission
vary depending upon the type of soils, biochar application rates, soil moisture conditions, thefertilization, and water management regimes.
Labile organic carbon (LOC): The highest LOC was found in amended clayey soil, 1697.45 to1890.71 mg-C kg-1, followed by loamy soil, 587.46 to 681.20 mg-C kg-1, and loamy sand, 99.93 to
178.99 mg-C kg-1, respectively. The results found that biochar had no influence on LOC in loamy
and clayey soils, but fluctuated among biochar rates in loamy sand (Fig. 1, b). The dynamicchanges of LOC in loamy soil with 6.25, 12.50 and 18.75 t ha-1 of biochar were gradually increased
from 0 to 21 DOI, but tended to go down at 28 DOI, contradictory to the LOC change in clayey soil,
which was still keep increasing over the whole incubation. In addition, LOC changes in loamy sandsoil were very low but fluctuated (data not shown). The positive correlations between LOC andbiochar rates were found in clayey and loamy sand soils, while the former was highly significant(Table 2). However, fluctuated correlations were manifested in loamy soil. Zhang et al. (2012)
found that biochar amendment did not change LOC over the rice growing season.
Potential of hydrogen (pH): The dynamic changes of pH in different soil textures showed thesame patterns, which increased from the initials to the fluctuated peaks at 7, 14 and 21 DOI and
thereafter had tendency to go down at the end of experiment. The highest initial pH indicated inloamy soil followed by clayey and loamy sand, but at the end of incubation we did not find any
significant differences among those soil amendments. The pH values were range from 5.87 to 6.93,
5.77 to 6.45 and 5.26 to 5.76 for loamy, clayey and loamy sand respectively. Furthermore, we did
not see the effects of biochar on soil pH in clayey and loamy sand soils, except for amended loamy
soil which bichar had influenced to enhance soil pH (Fig. 2, a). Furthermore, in loamy sand, thestronger correlation between biochar rates and pH, compared to loamy and clayey soils (Table 2).
Farrel et al. (2013) had proved that pH change in biochar amended soils were higher than control
soil over the duration of incubation experiment because biochar was highly alkalinity. Lai et al.
(2013) also claimed that the application of biochar increased the soil pH due to their alkalinity.
Nigussie et al. (2012) also supported the findings above, i. l. biochar stimulated soil pH, and theⒸ ISERD

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2500

70
70

b

a

60
60

aA
aA

Controol
Control
6.25
6.25 tt BC
BC ha
ha-1-112.50ttBC
BCha
ha-1-112.50
18.75ttBC
BCha
ha-1-1
18.75
25.00
t
BC
ha-1-125.00 t BC ha

50
50
40
40
bA

30
30
aB

20
20
cA

cA

10
10

dB

cB bB

eB

aB abC

0

0

Loam
Loam

Clay
Clay

bB bC bC

Labile organic carbon (mg-C kg-1)

Cumlative
4-C/ -1kg)
(mgCH
CH-C
CumulativeCH
production (mgkg )CH44 production
4

result gave another reason that the high surface area and porous nature of biochar and the factor
increases cation exchange capacity (CEC) of the soil and significantly positive correlate with pH.
Ventura et al. (2012) reported that biochar amended soil 30 and 60 t ha -1 had no effect on soil pH
from upland field experiment.

2000

1500

1000
B

0

Loamy sand
sand
Loamy

dB

cB bB
aB abCClaybB bC bC

Loamy sandLabileorganic
carbon(mg-C/kg)
Labileorganic
carbon(mg-C kg-1)

B

b
2000
2000

A

A

A

A

A

1500
1500

1000
1000
B

B

B
B B

500
500
aC

bC abC bC aC

00

Loam
Loam

Clay
Clay

Loamy sand
Loamy
sand

Different letters showed significantly different at p<0.01, vertical bars represent SE-mean. The lowercase used tocompare between the treatments within each soil type and the uppercase used to compare the same treatments among thethree soil types

Fig. 1 Cumulative CH4 production (a) and LOC at 28 DOI (b) from anoxic incubated soils anaffected by different rates of biochar application.
Electrical conductivity (EC): The highest initial EC was in loamy soil (0.34 to 0.40 dS m-1)
followed by clay (0.20 to 0.32 dS m-1) and loamy sand (0.02 to 0.08 dS m-1), respectively, but at theend of experiment we found that the highest EC was in clayey soil (0.25 to 0.44 dS m -1) followed
by loamy (0.12 to 0.16 dS m-1) and loamy sand (0.05 to 0.08 dS m-1) soils, respectively. Fig. 2, b
showed that biochar amendments had no potentials on soil EC in loamy soil, except for 25 t ha -1 ofbiochar amendment in clayey and loamy sand respectively, which promoted soil EC, compared tothe control. In addition, in loamy sand, the stronger correlation between biochar rates and EC wasevident, compared to loamy and clayey soils (Table 2).

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B
B B

500

2500
2500

Control
6.25 t BC ha-1
12.50 t BC ha-1
18.75 t BC ha-1
25.00 t BC ha-1

B

Loam

IJERD – International Journal of Environmental and Rural Development (2014) 5-1

0.6

88

a

b

a ab abc

66

Soil
Soil pH
pH

Electrical conductivity (dS m-1)

bc

44

22

0

0.5

0.4

0.3

Loam
Loam

B

Clay
Clay

Loamy sand
sand
Loamy

Electricalconductivity
conductivity(dS/m)
Electrical(dS m-1)

aA
Control
Controol-1
6.25
6.25ttBC
BCha
ha-1
-1
12.50
t
BC
ha
12.50 t BC ha-1
18.75 tt BC
BC ha
ha-1-118.75
25.00 tt BC
BC ha
ha-1-1
25.00

0.3
0.3

bA
bA

bA
bA

B

0.2
0.2
B

B
B

B

0.1
0.1

aB
abC
abC

bC abC

0.0
0.0
Loam
Loam

Loamy sand

Clay
Clay

Loamy sand
sand
Loamy

Different letters showed significantly different at p<0.01, vertical bars represent SE-mean. The lowercase used tocompare between the treatments within each soil type and the uppercase used to compare the same treatments among thethree soil types

Fig. 2 Soil pH (a) and EC (b) at 28 DOI from anoxic incubated soils an affected by different
rates of biochar application
Table 2 Pearson correlation coefficients (r) relating biochar rates to CH4 production rate,
LOC, pH and EC
Soil parameter
CH4 (mg CH4-C kg-1d-1)

LOC (mg kg-1)

pH

EC (dS m-1)

B

Loam

b

Clay

B
B

0.1

0.6
0.6

0.4
0.4

B

0.2

0.0

0

0.5
0.5

Control
6.25 t BC ha-1
12.50 t BC ha-1
18.75 t BC ha-1
25.00 t BC ha-1

DOI
7
14
21
28
7
14
21
28
7
14
21
28
7
14
21
28

Loamy soil
-0.80**-0.82**-0.86**-0.85**
0.75**-0.66*
-0.29
0.50
0.39
0.19
-0.32
-0.61*
-0.04
0.17
-0.56
-0.05

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Clayey soil
0.80**-0.82**-0.81**-0.88**
0.73**
0.69*
0.57
0.63*
0.77**
0.58*
0.15
-0.22
0.54
-0.22
0.19
0.58*

Loamy sand soil
-0.51
-0.52
-0.60*-0.69*
0.51
0.41
0.68*
0.51
0.85**
0.96***
0.16
0.50
0.91***
0.86**
0.79**
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IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Ventura et al. (2012) indicated that biochar application significantly increases soil EC and it
was a direct relationship between biochar rate and EC. The higher rate of biochar application
results in higher EC. Nigussie et al. (2012) had emphasized that biochar amended soils enhanced
EC in chromium polluted soil because biochar attributed to ash accretions as ash residue which was
dominated by carbonates of alkali and alkaline earth metals, variable amounts of silica, heavy
metals, sesquioxides, phosphates and small amounts of organic and inorganic N. In addition, Farrel
et al. (2013) proved that biochar had highly EC, which tend to promote soil EC.
CONCLUSION
Biochar amendment had varied effect on CH4 production in different soil textures under anaerobic
incubation. Biochar enhanced CH4 production in loam and clay, but decreased in loamy sand.
Simultaneously, biochar amendment had no potential to change LOC in every soil. While, biochar
had influenced to stimulate soil pH in loam, but not found any effectiveness in other two soils. In
addition, EC changes were tending to increase by biochar in clay and loamy sand. The correlation
was found between biochar rates and soil parameters in each soil texture and interaction between
LOC, pH, EC, and CH4 production. In order to minimize biochar production from tree feedstock,
the future research should generate biochar from crop residues (rice straw, rice hull, grass etc.), or
agricultural industrial wastes.
ACKNOWLEDGEMENTS
The authors would like to pay the highest respect and gratitude to H.R.H. Princess Maha Chakri
Sirindhorn, who awarded this scholarship. This research was also partially supported by the
National Research University Project, KKU and Office of the Higher Education Commission;
KKU’s Graduate School Research Fund; KKU research grant, financial year 2013-2014; and also
the project “Problem soils in Northeast Thailand.”
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