IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Research article
erdChanges in Soil Nitrous Oxide and Carbon Dioxide
Dynamics after the Application of Digested Liquid Cattle
ManureTOMONORI FUJIKAWA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: t3fujika@nodai.ac.jp

MASATO NAKAMURA
National Institute for Rural Engineering, National Agriculture and Food Research
Organization (NARO), Tsukuba, Japan
Recieved 13 December 2012

Accepted 10 June 2013(* Corresponding Auther)

Abstract The aim of this study was to clarify the changes in N2O and CO2 emission fromthe soil surface, their concentrations in soil gases, and gas diffusion fluxes after applicationof digested liquid manure (DL) produced by anaerobic digestion of cattle manure slurry.
N2O emission increased more and faster after application of DL compared to after theapplication of conventional inorganic fertilizer. The N2O emission rate from the DL was
0.25% of the applied nitrogen. CO2 emission after the DL application also increased, andthe CO2 emission ratio from the DL was 33% of the applied C. Soil N2O concentration
increased after DL application. The highest soil N2O concentration occurred earlier thanthe largest N2O emission. The increase in CO2 concentrations near the surface was small.
The largest N2O diffusion flux was observed near the surface, and a negative flux was
observed in deeper layers 14 days after DL application. The difference in the CO2 flux
between deeper and surface layers flux was smaller than that in the N2O flux, whichsuggests that the contribution of CO2 generation in deeper layers is larger than that of N2O.
Keywords Methane fermentation, soil gas concentrations, gas diffusion, greenhouse gases

INTRODUCTION
Anaerobic digestion of livestock slurry can potentially reduce greenhouse gas (GHG) emission andsustainably generate electrical and heating energy (Rico et al., 2011). However, digested liquidmanure, which is a by-product of anaerobic digestion, contains a large quantity of organic matters.
Treatment of wastewater containing the digested liquid manure is expensive in terms of energy andchemicals (Massé et al., 2007). The digested liquid manure contains high levels of carbon andnitrogen compounds and other nutrients that can promote plant growth. Application of this liquid toagricultural fields as liquid fertilizer would therefore be an efficient use of the digested liquidmanure, but the environmental effects of this application, and especially the emission of GHGs
need to be better understood.
In a farmland soil, GHGs such as N2O and CO2 are generated by the decomposition of theapplied nitrogen or carbon compounds by soil microorganisms, and the generated gases diffuse
through the soil profile following concentration gradients until the gas is emitted from the soil
surface into the atmosphere. This scenario indicates that the emission of the gases from the soil
surface depends on not only the total amount of generated gases in the soil but also the location (i.e.
depth) of the generation and gas diffusion fluxes.
The aim of this study were to clarify the changes in N2O and CO2 emission from the soil
surface, the corresponding changes in their concentrations and gas diffusion fluxes in the soil after
the application of digested liquid manure produced by digestion of cattle manure slurry.

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METHODOLOGY
Site description and experimental setup
Samples of digested liquid manure produced by anaerobic digestion mixture of dairy cattle manureslurry and vegetable scraps at the Yamada Biomass Plant in Katori City, Chiba Prefecture, Japan(Nakamura et al., 2007) was obtained. The digested liquid manure used in the present study wascollected in September 2007. Approximately half of the nitrogen in the digested liquid manure isorganic nitrogen, and the remainder is NH4-N, with a very small NO3-N content. In this study, thedigested liquid manure without any dehydration or filtration was used. The field experiments wereconducted in an experimental field at the National Institute for Rural Engineering in Tsukuba City,
Ibaraki Prefecture. This field was classified as Andosol soil, and the surface soil was light clay
(LiC). This field had not been cultivated for more than 3 years prior this experiment.
A total of 4 plots (1 m × 2 m) in the field were established. Based on previous standard
fertilizer application rate that has been used around this site, we applied 24 g N m-2 (7800 cm3 m-2)of the digested liquid manure to the surface soil in the first plot (hereafter, the DL treatment). In thesecond plot, (NH4)2SO4, which included the same total amount of nitrogen as in the DL treatment,
was applied (hereafter, the conventional fertilizer [CF] treatment). In the third plot, we added thesame amount of (NH4)2SO4 used in the CF treatment, but added water equal to the amount includedin the digested liquid manure; hereafter, we refer to this as the conventional fertilizer plus water(CW) treatment. We also included a non-fertilized plot (hereafter, the NF treatment) as the control.
All three treatments were applied in October 2007. In the DL, CF, and CW treatments, Mg3(PO4)2
and KCl were also applied to prevent P or K deficiency from affecting the results. Japanesemustard spinach (Komatsuna: Brassica rapa var. perviridis) was sown 7 days after the fertilizer
application. The komatsuna plants were harvested after 57 days. The field was not irrigated, andrainfall during the growth period totaled 169 mm which is normal for the study area; thus, the soils
were neither excessively dry nor flooded. The yield of komatsuna was highest in the DL treatment,
at 1900 g m-2 (9.1 g N m-2). The plants absorbed 37% of the applied nitrogen in this treatment. The
yield in the CF treatment (890 g m-2) was smaller than that in the CW treatment (1800 g m-2). These
differences appear to have resulted from a water shortage during the early growth stages suggested
by Fujikawa and Nakamura (2010).
Measurements
Emissions of N2O and CO2 from the soil were measured surface using the closed-chamber method(Rolston and Moldrup, 2002). Daily measurements were completed between 09:00 to 11:00 h.
Three collars were installed in each plot. N2O and CO2 concentrations in the sampled gas wereanalyzed using a GC-8A gas chromatograph (Shimadzu, Kyoto, Japan) with an electron capture
detector and a GC-14A gas chromatograph (Shimadzu) with a thermal conductivity detector,
respectively. Hutchinson and Livingstone (2002) estimated the gas emission flux (q; g N m-2 h-1 for
N2O; g C m-2 h-1 for CO2) using the slope of the change in gas concentration in the chamber (a; m3
m-3 h-1), the height of the gas chamber (h; 0.20 m), the ratio of nitrogen mass to N2O mass orcarbon mass to CO2 mass (s; 28/44 for N2O; 12/44 for CO2), the density of each gas at 273.15 K (ρ;g m-3), and the temperature (T; K): 273.15 q  ρ ahs
T 


(1).

Cumulative gas emission (Q; g N m-2 for N2O; g C m-2 for CO2) in the DL, CF, and NF
treatments were calculated based on the assumption of linear changes between consecutive
measurements: 2  t  q  q 
n

Q

1

i

i 1

(2).

i

i 1

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where qi is the ith measurement flux, Δti is the time interval between measurements i and i - 1, andn is the total sampling time. The increase in emission of each gas as a result of fertilizer application(Q’) was calculated by subtracting Q in the NF treatment from Q in the DL and CF treatments, andthe nitrogen and carbon emission rates were estimated by dividing Q’ by the amount of nitrogen or
carbon (respectively) in the applied fertilizer.
Soil gas was collected using the stainless-steel gas sampling pipes described by Fujikawa et al.
(2000). Soil gas samples (10 cm3) from around the gas inlets were removed from the pipes using asyringe. The N2O and CO2 concentrations in the soil gases were quantified using the gas
chromatographs, as described above.
Undisturbed 100 cm3 soil cores were collected to determine the gas diffusion coefficient ofeach soil layer. The soil gas diffusion coefficient for O2 was quantified using the non-steady-statemethod suggested by Osozawa and Hasegawa (1995). Relative gas diffusivity (D/D0) was
calculated by dividing the O2 gas diffusion coefficient of the soil (D) by that in the atmosphere(D0). The gas diffusion coefficient of each gas (Da) was estimated by multiplying the relative gas
diffusivity by the diffusion coefficient in the atmosphere for each gas (N2O = 0.0514 m2 h-1, CO2 =0.0756 m2 h-1) as suggested by Rolston and Moldrup (2002).
The gas diffusion flux (qd) in the soil was calculated by multiplying the gas diffusion
coefficient (Da; m2 h-1) by the gas concentration gradient, which was obtained by dividing thedifference in gas concentrations by the distance between two measurements at adjoining depths:
 273.15  Cu  Cd
qd   ρ 
 Da
s
T 
z u  zd(3).

where Cu and Cd are the gas concentrations at depths of zu and zd, respectively, where u and d referto the upper and deeper soil layers, respectively. The datasets for the calculation of qd are shown in
Table 1. The values of Da of the samples obtained 3 days after the fertilizer application were used
for qd after 7, 14 and 21 days and those of the samples obtained 36 days after the application wereused for qd after 36 days.
Table 1 Datasets of zu, zd and Da for the calculation of
the gas diffusion flux (qd) in the soil
Depth of qd (cm)
- 2.5
2.5
7.5
12.5
22.5
32.5
42.5

zu (cm)
- 5**
0**
5
10
20
30
30

zd (cm)
0**
5
10
15
25
50
50

Depth of Da* (cm)(atomosphere***)0 to 55 to 1010 to 15
20 to 25
30 to 35
40 to 45*: Depth of the undisturbed samples using for the measurement of D a**:The atmosphere above the soil surface was also sampled using a syringe.
***: Da at -2.5 cm is gas diffusion coefficient in the atmosphere (D 0)

RESULTS AND DISCUSSION
Emissions of N2O and CO2
One week after fertilizer application, a strong increase in N2O emission was observed in DL. The
increase of N2O emission were also observed in CF and CW but it took about 7 days longer toreach its peak in CF and CW than in DL. The difference in N2O emission between the CF and CW
treatments was negatively small, even though plant growth was much lower in the CF plot.
Changes in cumulative N2O emissions in the DL, CF, CW and NF treatments over time are shownin Fig. 1(a). The cumulative N2O emission in DL was higher than that in CF or CW for about
30days after the fertilizer application. The difference in N2O emission rates could have resulted© ISERD
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100
80

120

(a)

60
40
20
0
0

Cumulative CO2 emission(g CO2-C m-2)

Cumulative N2Oemission(mg N2O-N m-2)

from activation of microorganisms by the organic compounds in the digested liquid manure. The
cumulative N2O emission in DL was 63 mg N m-2 (reached after 57 days) and the N2O emission
rate was 0.25%. This emission rate was similar to that (0.17%) reported by Wulf et al. (2002).
In the DL treatment, the peak CO2 emission was observed just after the fertilizer application.
The CO2 emission decreased with time after 2 days from the application and remained relatively
constant or increased slightly until about 57 days after fertilizer application. No significant
difference between that in CF and CW and that in NF during the first 20 days after the fertilizer
application. This suggests that the effect of the application of inorganic nitrogen and water on theCO2 emission rate was small and that the increase in CO2 emission after application of the digested
liquid manure was caused by 1) the decomposition of the organic matter in the digested liquidmanure and/or by 2) the activation of soil microorganisms by the organic nitrogen. By 30 days after
the fertilizer application, CO2 emission in CF and CW became larger than that in NF. The reason
for this increased CO2 emission was probably that promotion of plant growth by the fertilizer
increased root respiration. The cumulative CO2 emission by the application of digested liquidmanure during the first 28 days, during that time the effect of plant root respiration would be small,was 41 g CO2-C m-2 (Fig. 1(b)). The CO2 emission rate was 33% in the DL plot. Part of the carbon
applied to the soil was emitted as a gas and the remainder moved downward into the groundwater
after dissolving in the soil water or accumulated in the soil.

20

40

60

(b)

80
40

0
0

20

40

60

Time (days after fertilizer application)

Fig. 1 Changes in cumulative (a) N2O and (b) CO2 emission in DL and CF, and NF plot.
Concentrations of N2O and CO2 in the soil
The soil N2O concentration increased after the fertilizer application in both the DL and CF
treatments (Fig. 2). Soil N2O concentrations remain unchanged throughout the study period in the
NF treatment. Throughout the first 7 days of the study, the N2O concentration increased withincreasing depth in the DL and CF treatments; in contrast, at 14 days, the N2O concentration inboth treatments increased to a depth of 5 cm, then decreased thereafter with increasing depth. The
decrease in the N2O concentration in DL was faster than that in CF, which agrees with the changes
in N2O emission. The highest N2O concentration occurred between 7 and 14 days (DL) andbetween 14 and 21 days (CF), which were earlier than the largest N2O emissions observed in theseplots. This suggests that the increase in N2O emission is delayed compared with the increase in theN2O concentration in the surface soil layers.
The soil CO2 concentration tended to increase with increasing depth in all plots (Fig. 3). In the
DL treatment, there was a small and possible non-significant increase in CO2 concentration
between days 7 and 14 in the surface layers (0 to 20 cm). However, the amount of the increase in
DL was smaller than that in CF and NF, which indicates that changes in CO 2 concentration in thesurface soil after the application of the digested liquid manure were smaller than those caused by
the changes in the temperature, aeration, and water content of the soil. Changes in CO2
concentrations in deeper layers (> 30 cm) were larger than those in surface layers in each plot. Thisagrees with the results of Fujikawa et al. (2000) stated that diurnal fluctuations in soil CO2
concentrations were larger in deeper layers in a field with a hard pan. The large diffusion flux of
CO2 negated the effect of changes in generation of CO2 by soil microorganisms, although the© ISERD
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respiration rates of roots and microorganisms would be larger in this layer because of the abundant
substrate and oxygen availability.

Depth (cm)

0

0

0

20

20

20

40

40

40

(DL)

60
0

0.4 0.8 1.2

(CF)

60

Days after
the application
7
14
21
36
(NF)

60
1.6
0 0.4 0.8 1.2 1.6
0 0.4 0.8 1.2
Soil N2O concentration（mg N2O-N m-3）

1.6

Fig. 2 Distribution of the concentration of N2O as a function of time

Depth (cm)0Days after
the application
7
14
21
36

20

40

0

20

20

40

40

(DL)
(CF)
60
60
1
2
3
0
2
3
0
Soil CO2 concentration（g CO2-C m-3）

60
0

0

1

(NF)

1

2

3

Fig. 3 Distribution of the concentration of CO2 as a function of time
Soil gas diffusivity and diffusion flux
In DL, agglutination of the soil particles was observed, and the bulk density of the soil was reducedby these large pores. However in the top layer of the soil (0 to 5 cm) the differences in air-filled
porosity and the relative gas diffusivity between treatments were small, whereas in deeper layers,
the differences were large because of the large differences in bulk density in these deeper layers.

Depth (cm)

-10
-10
(a)
(b)
0
0
10
10
Days after
the application
20
20
7
30
30
14
21
40
40
36
50
50
-100 0 100 200 300-100 0 100 200 300
Gas diffusion flux of N2O （g N2O-N m-2 h-1）Depth (cm)Depth (cm)

-10 (c)
-10
(d)
0
0
10
10
20
20
30
30
40
40
50
50
-40 0 40 80 120-40 0 40 80 120
Gas diffusion flux of CO2 （mg CO2-C m-2 h-1）

Fig. 4 Distributions of the gas diffusion flux of N2O in the (a) DL and (b) CF treatments andof the gas diffusion flux of CO2 in the (c) DL and (d) CF treatments© ISERD
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The maximum N2O gas diffusion flux in the top layers of the soil (Fig. 4(a), (b)) was larger inDL than in CF. A negative flux was observed in DL at 5 to 50 cm in depth 14 days after thefertilizer application. This indicated that downward N2O diffusion occurred as a result of theapplication of digested liquid manure. It must be verified whether the larger downward flux of N2O
by digested liquid manure than inorganic fertilizer originated from the properties of the digested
liquid manure. The CO2 gas diffusion flux decreased with increasing depth in the DL and CF
treatments (Fig. 4(c), (d)). Compared with the N2O diffusion flux, the difference in the CO2 flux
between deeper and surface layers was smaller. This supports previous reports that the contributionof the generation of CO2 in deeper layers is larger than that of N2O. The distribution of the CO2 gas
flux in CF varied with time; for this scenario, further research need to be conducted.
CONCLUSION
We cultivated komatsuna in the field under three fertilization treatments, inclusive of digested
liquid manure and an unfertilized control, to clarify the changes in N2O and CO2 dynamics in thesoil and at the soil surface. N2O emission increased more rapidly and substantially after theapplication of the digested liquid manure compared to inorganic fertilizer. Based on the cumulative
N2O emission, the N2O emission rate was 0.25% for the digested liquid manure. CO2 emission
increased drastically after the application of the digested liquid manure, and then decreased withtime from 2 days after the fertilizer application, but remained higher than the initial value. The CO2
emission ratio for the digested liquid manure was 33%. The soil N2O concentration increased after
the application of digested liquid manure and inorganic fertilizer. The increase in N2O emission isdelayed compared with that in the N2O concentration in the surface soil. The changes in the CO2
concentration in the surface soil caused by the application of digested liquid manure were smaller
than those caused by changes in the temperature, aeration, and water content of the soil. The largest
N2O gas diffusion flux was observed in the surface layer and negative flux was observed in deeper
layers 14 days after the application of digested liquid manure. The difference in the CO2 flux
between deeper and surface layers was smaller than that for N2O. This suggests that thecontribution of CO2 generation in deeper layers is larger than that of N2O after the application ofdigested liquid manure.
ACKNOWLEDGEMENTS
The present study was supported by grant from Ministry of Agriculture, Forestry and Fisheries ofJapan (Rural Biomass Research Project, BUM-Cm3200). And for soil carbon analysis, it was also
supported a Grant-in-Aid for Young Scientists (B), No. 22780222, provided by the Ministry of
Education, Culture, Sports, Science and Technology, the Government of Japan.
REFERENCES
Fujikawa, T. and Nakamura, M. 2010. Influence of application method and rate of digested liquid frommethane fermentation on N2O gas emission and plant growth. (In Japanese with English abstract.) Jpn. J.
Soil Sci. Plant Nutr., 81(3), 240-243.
Fujikawa, T., Miyazaki, T., Seki, K. and Imoto, H. 2000. Correlation between the distribution of
microorganisms and CO2 and O2 gas concentrations in a field under rotating use. (In Japanese withEnglish abstract.) Trans. Jpn. Soc. Irrig. Drain. Reclam. Eng., 68(4), 443-452.
Hutchinson, G.L. and Livingstone, G.P. 2002. Chap 4.5. Soil-atmosphere exchange; In: Dane, J.H. and Topp,
G.C. (eds.), Methods of Soil Analysis Part 4, Soil Sci. Soc. Am., Madison, U.S.A., 1159-1182.
Massé, D.I., Croteau, F. and Masse, L. 2007. The fate of crop nutrients during digestion of swine manure inphychrophilic anaerobic sequencing batch reactors. Bioresour. Technol., 98, 2819-2823.
Nakamura, M., Yuyama, Y., Yamaoka, M. and Fujikawa, T. 2007. Material balance in biogas plant andfertilizer characteristics of digested liquid and digested liquid supplement. (In Japanese with English
abstract.) Trans. Jpn. Soc. Irrig. Drain. Reclam. Eng., 75(3), 337-343.

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Osozawa, S. and Hasegawa, S. 1995. Diel and seasonal changes of carbon dioxide concentration and flux inan andisol. Soil Sci., 55, 55-62.
Rico, C., Rico, J.L., Tejero, I., Muñoz, N. and Gómez, B. 2011. Anaerobic digestion of the liquid fraction of
dairy manure in pilot plant for biogas production: Residual methane yield of digestate. Waste Manage.,31, 2167-2173.
Rolston, D.E. and Moldrup, P. 2002. Chap 4.5. Gas Diffusivity; In: Dane, J.H. and Topp, G.C. (eds.),
Methods of Soil Analysis Part 4, Soil Sci. Soc. Am., Madison, U.S.A., 1113-1139.
Wulf, S., Maeting, M. and Clemens, J. 2002. Application technique and slurry co-fermentation effects onammonia, nitrous oxide, and methane emission after spreading: II. Greenhouse gas emissions. J. Environ.
Qual., 31, 1795-1801.

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