Effects of Nitrogen and Nitrification Inhibitors Addition on N2O Emissions under different Long-Term Fertilization
Regimes
Xin Zhang1,2, Haoyu Qian1, Shengming Li3,
Fangjing
Xie3, Yu Jiang4, Frederick
Danso1, Aixing Deng1,
Zhenwei
Song1, Huan Chen5, Weijian Zhang1
and Chengyan Zheng1*
1Institute of Crop Sciences,
Chinese Academy of Agricultural Sciences/ Key Laboratory of Crop Physiology and
Ecology, Ministry of Agriculture and Rural Affairs, Beijing 100081, China
2National
Engineering Laboratory for Improving Quality of Arable Land, Institute of
Agricultural Resources and Regional Planning, Chinese Academy of Agricultural
Sciences
3Institute of
Agricultural Sciences in Xiao County, Xiao County 235200, China
4Jiangsu
Collaborative Innovation Center for Modern Crop Production/National Engineering
and Technology Center for Information Agriculture/Key Laboratory of Crop
Physiology and Ecology in Southern China, Nanjing Agricultural University,
Nanjing 210095, China
5Anhui Academy
of Agricultural Sciences, Hefei 230031, China
*Correspondence
author: zhengchengyan@caas.cn
Received
23 June 2021; Accepted 22 October 2022; Published 12 December 2022
Abstract
Changes in soil systems can
occur during the implementation of long-term agronomic practices and consequently
result in different N2O emissions in response to external environment. Therefore, an incubation study was conducted using
Fluvisols from a 30-yr fertilization experiment to assess N2O
emissions produced because of the nitrogen (N) and nitrification inhibitor (NI)
addition. Different soils were sampled from four
fertilization treatments: no fertilizer (NF), chemical NPK fertilizer (NPK), organic
manure (M) and chemical NPK fertilizer plus manure (NPKM). The results showed that effects of N and NI
additions on N2O emissions were significantly different among the
different soils. The highest stimulation on N2O
emission with N addition was observed in soil with
long-term NPK fertilization regime (10.2 times), while the lowest reduction on N2O
emission due to NI addition in soil with long-term M fertilization
(27.7%). The regression analysis showed that increase rate of N2O
emission caused by N addition and decrease rate by NI was negatively
related to soil organic carbon (SOC) concentration. Our findings indicated that
response of N2O emissions to N and NI additions were different under
different long-term fertilization regimes in Fluvisols, mainly resulting from
the difference of soil organic matters. © 2022 Friends Science
Publishers
Key words: Nitrogen; Nitrification
inhibitor; N2O; Long-term fertilization; Different soil ecosystem
Nitrous oxide (N2O) is the third
important greenhouse gas (GHG) which contributes 6~8% to current global warming
(Smith et al. 2007). Additionally, N2O
concentration can also increase atmospheric PM 2.5 accumulation and aggravate
stratospheric O3 depletion (Ravishankara et al. 2009;
Huang et al. 2014). Agriculture accounting for ∼60% of the global anthropogenic N2O
emissions (IPCC 2013), is projected to increase by
60% in 2050 in order to satisfy the food needs of the growing population (FAO
2013). It is necessary to carry out the appropriate agricultural management,
which can mitigate GHG emissions and maintain crop production simultaneously.
Soil N2O is produced
mainly by microbial nitrification and denitrification processes (Bouwman 1998;
Zhu et al. 2013; Zhang et al. 2018). The soil physical, chemical
and microbial characteristics have been observed to change significantly with
different long-term agricultural management practices (García-Orenes et al.
2009; Zhang et al. 2012), and these changes could affect N2O
emissions in response to the external disturbance, such as temperature
(Coudrain et al. 2016). Nitrogen (N) and nitrification inhibitor (NI)
are both external disturbance that can significantly affect N2O
emissions from agricultural soils. Generally, application of N fertilizer can increase
soil N2O emissions in a nonlinear trend (Hoben et al. 2011; Shcherbak et al. 2014;
Hoa et al. 2018). Nitrification inhibitors can inhibit NH4+
oxidation to NO2- through slowing the genus of nitrifying
bacteria and nitrosomonas, reduce NO3- concentration, and
may thus reducing N2O emissions (Abbasi and Adams 2000; Zhu et
al. 2019; Borzouei et al. 2021). As reported previously in
meta-analysis, response of soil N2O emissions to the N and NI
additions was different along with climate factors, cropping systems or soil
conditions (Shcherbak et al. 2014; Li et al. 2018). To the best of
our knowledge, however, information on how the different soil ecosystems affect
N2O emissions in response to N and NI additions in a specific site
with the same environment conditions is still limited.
Fertilization is a key agricultural
practice that would have a long-term impact and significantly affect the soil
ecosystem (Geisseler and Scow 2014; Wen et al. 2020). Previously, we
found the significant difference in soil microbial biomass, pH, organic carbon and
nitrogen under treatments of chemical fertilizer and manure after a 30-yr field
experiment (Zhang et al. 2017). It was
hypothesized that effects of N and NI additions on N2O emissions
would be different in soil after long-term different fertilization. Therefore,
a laboratory incubation study was conducted to investigate the differences in N2O
emissions resulting from the additions of N and NI to the soils under different
long-term fertilization regimes.
Materials and Methods
Soil sampling and analysis
The long-term fertilization experiment was
initiated in 1983 at the Institute of Agricultural Sciences in Xiao County, Anhui
Province, China (34°18′ N, 116°53′ E). The
climate and soil characteristics and the experimental design of this site have
been described in our previous study (Zhang et al. 2017). The
fertilization regimes selected in the present study were no
fertilizer (NF), chemical NPK fertilizer (NPK), organic manure (M), and
chemical NPK fertilizer plus manure (NPKM). The total amount of nitrogen
input in each fertilization regime was 240 kg ha-1, while phosphorus
and potassium were not unified. Chemical N, P and K fertilizers used in this
experiment were urea, superphosphate, and potassium sulphate, respectively, and
cattle manure was used for the M and NPKM regimes. The application amounts of
different fertilizers in each treatment are shown in Table 1.
We collected fresh soils from 0–20 cm layer in the field
after soybean harvest in 2015. In each plot, five randomly sampled soil cores
were taken and mixed to one sample. The samples were passed through
Soil
incubation and gas sampling
Laboratory
incubation experiment was conducted in Chinese Academy of Agricultural Sciences
(40.0°N, 116.3°18’E), Beijing, China. Six aliquots (
N2O fluxes in the incubation studies were measured every day for three consecutive days and every 2 or 3 days afterwards,
until the fluxes under U and UNI treatments were no
different from the CK (12 days totally). On each
sampling occasion, three glass jars of each treatment
were sealed with airtight rubber plugs and
then incubated for 2 h in the dark at 25°C. The rubber plugs were fitted
with three-way valves to allow for headspace gas sampling. Before and after the 2-h airtight incubation, a 30-mL gas sample was taken
from each jar using an airtight syringe. The sampled headspace N2O
concentrations in the jars were determined with a gas
chromatograph (GC, Agilent
Effects of N and NI additions on N2O
emissions
The
effects of N and NI additions on N2O emissions in the different
soils were calculated as the follows:
Effect of N addition on N2O
emissions = (U - CK)/CK × 100% (1)
Effect of NI addition on N2O
emissions = (U - UNI)/U × 100% (2)
Soil measurement
On 6th
day of the incubation, three soil microcosms for soil properties determination
in each treatment was destructively sampled and passed through a 2-mm sieve for
the measurement of soil available nitrogen, nitrification and denitrification
potential. NH4-N and NO3-N concentrations extracted by potassium
chloride solution were analyzed with the continuous flow analyzer (TRAACS 2000,
Germany). Soil nitrification and denitrification potentials were measured following
the techniques described by Šimek and Kalčík (1998) and Chu et al.
(2007), respectively.
Table 1: The application amounts of fertilizers and their total pure nutrient
contents of N, P, and K under different long-term fertilization regimes
|
Application amounts of fertilizers
in kind (kg ha-1) |
Pure
nutrient contents in total (kg ha-1)
|
|||||
Treatments |
Manure |
Urea |
Superphosphate |
Potassium sulphate |
N |
P |
K |
NF |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
NPK |
0 |
522 |
1338 |
267 |
240 |
335 |
120 |
M |
75000 |
0 |
0 |
0 |
240 |
188 |
113 |
NPKM |
37500 |
261 |
669 |
134 |
240 |
261 |
116 |
Treatments of NF, NPK, M and
NPKM represent no fertilizer application, sole organic manure, balanced
chemical fertilizer and chemical NPK plus manure, respectively
Fig. 1: Response of N2O fluxes to N and
nitrification inhibitor (NI) additions in soils under different long-term fertilization:
(a) NF; (b) NPK; (c) M; (d) NPKM. Vertical bars indicate the standard
error (n = 3)
Statistical
analysis
The means
and standard error for each data set were calculated from triplicate plots while
Microsoft Excel 2003 was used for basic data calculation and drawing of graphs.
All statistical analyses were carried out using SAS system (SAS 9.2, USA). Differences
in treatments were evaluated using analysis of variance (Proc Anova) and significance
among treatment means using the least significant difference (LSD). Proc Reg
was used to do the linear regression analysis of N2O emissions in
response to N and NI additions upon soil organic carbon.
Dynamics
of N2O fluxes during the incubation period
The application of urea
increased N2O fluxes from the fertilizer treatments as compared to
CK (Fig. 1). Urea application increased N2O fluxes significantly in
the 1st and 2nd day, and subsequently decreased
continuously till no difference were observed in comparison with the CK. The application
of urea with nitrification inhibitor (i.e., UNI treatment) decreased N2O
fluxes compared to urea (U) treatment under all the fertilization regimes, with
almost similar time trends to N2O fluxes in urea (U) treatment.
Effects
of N and NI additions on N2O emissions and their relationship with
SOC under different fertilization regimes
Application of urea (U) significantly
increased N2O emissions in comparison with CK, while nitrification
inhibitor application (UNI) significantly decreased N2O emissions
compared to urea (U) treatment (Fig. 2a, P
< 0.05). Under different fertilization regimes, various effects of N
and NI additions on N2O emissions were observed. Compared to CK, N2O emissions were increased
by 543, 1023, 537 and 365%, under fertilization treatments of NF, NPK, M and
NPKM (Fig. 2b), respectively. Moreover, the increase rate of N2O
emission under NPK treatment was significantly higher than other fertilization
treatments (P < 0.05). Compared
to urea (U) treatment, decrease rate of N2O emissions in UNI were
56.9, 79.9, 27.7 and 60.3%, respectively, under fertilization treatments of NF,
NPK, M and NPKM (Fig. 2c). In addition, the decrease rate of N2O emission
under M treatment was significantly lower than those under other fertilization
treatments (P < 0.05).
Increase rate of N2O emissions in U compared to CK was
negatively related to SOC (Fig. 3a), though the relationship was not
significant. Decrease rate of N2O emissions
in UNI compared to U treatment was negatively related to SOC (Fig. 3b, P < 0.01).
Effects of N and NI additions on soil NO3-N
content, nitrification and denitrification potential under different
fertilization regimes
Urea (U) treatment significantly
increased NO3-N content in comparison with CK, and urea + nitrification
inhibitor (UNI) treatment significantly decreased NO3-N
content in comparison with urea (U) (Fig. 4b, P < 0.05), with various
impacting amplitudes under different fertilization regimes. Increase of NO3-N
content under NPK treatment was higher than both M and
NPKM treatments when urea was added.
Urea (U) treatment significantly increased nitrification potential in
comparison with CK, while nitrification inhibitor (UNI) treatment significantly
decreased nitrification potential in comparison with urea (U), with various
impacting amplitudes under different fertilization regimes (Fig. 4c, P < 0.05). Increase
of nitrification potential under M treatment was lower compared to other
fertilization treatments when urea was added. Although
fertilization treatments of M and NPKM significantly increased soil denitrification potential, N and NI additions had no
effect on soil denitrification (Fig. 4d).
Discussion
The results showed that application
of urea significantly
Fig. 2: Effects of N and NI additions on N2O emissions in soils
under different long-term fertilization regimes. (a) Cumulative N2O
emissions; (b) Increase rate of N2O emissions in response to
N addition; (c) Decrease rate of N2O emissions in response to
NI addition. Vertical bars indicate the standard error (n = 3). Different lowercase
letters indicate significant difference between incubation treatments at P
< 0.05
increased N2O emissions in comparison with CK, with the various
effects under different fertilization regimes. According to Geisseler and Scow
(2014) and Zhang et al. (2017) and Yang et al.
(2019), long-term different fertilization would change the physical, chemical and microbial
characters of soil, and may affect the response of N2O emissions to
N addition. In the present study, significant differences in soil organic
carbon, nitrogen and pH were observed among the fertilization regimes (data not
shown), indicative of variation in the soil ecosystems after long-term
fertilizer application. Moreover, regression analysis showed the increase rate
was negatively related to SOC. The observed increase in N2O emission
under NPK was higher than under M and NPKM fertilization regimes. It can be
attributed to the sorption of NH4+ onto soil organic
matters (Fernando et al. 2005). Soil organic matter content was
significantly higher in fertilization regimes of organic amendment (i.e.,
M and NPKM regimes) compared to NPK regime. When urea added to soil, NH4+
hydrolyzed from urea might be absorbed by soil organic matters, then the NO3-
would thereupon decrease, which is confirmed by the lower increase rate of NO3-N
content in urea (U) treatment compared to CK under fertilization regimes of M
and NPKM (Fig. 4b).
It was also found that
application of nitrification inhibitor significantly
reduced soil N2O emissions, as previously reported in earlier
studies of upland field (Tian et al. 2015; Guardia et al.
2017; Recio et al. 2019), with different reduction rate
under various fertilization regimes. Regression analysis showed the decrease rate was negatively
related to SOC content. The decrease rate of N2O
emission under regime with manure was significantly lower than under other
fertilization regimes (P < 0.05).
One of the mechanisms can be that high organic matter
could null the nitrification inhibitor through
adsorption (Jacinthe and Pichtel 1992; Asgedom et al.
2014). Fertilization regime of manure has the
highest organic matter, which can greatly hinder the nitrification
inhibitor, and thus got lower reduction rate of N2O emission. Another
reason might be the difference of soil microbes among
different fertilization treatments. The nitrification and denitrification potential under fertilization
regime of manure was higher than NPK, indicating greater microbial activities
related to N2O emissions. After application of nitrification inhibitor, decrease rate of these microbial
properties was lower in manure regime, which in turn
caused lower reduction of N2O emissions.
Fig. 3: Linear regressions of N2O
emissions in response to N (a) and NI (b) additions upon soil
organic carbon (SOC) content. * represents the significant regression at P
< 0.05
Fig. 4: Impacts of N and NI additions on
NH4-N concentration (a), NO3-N concentration (b),
nitrification potential (c) and
denitrification potential (d) in soils under different long-term
fertilization. Vertical bars indicate the standard error (n = 3). Different lowercase
letters indicate significant difference between incubation treatments at P
< 0.05
In the present study, N and NI additions had significant
effects on N2O emissions. However, the
response of related nitrifiers and denitrifiers in soils from different
long-term fertilization was not clear, which needs further investigation.
Besides, it is considered that gaseous N is closely
related to global warming, i.e., N2O in this study. However,
there is other important gaseous N such as N2, also being product of
denitrification process (Poth 1986), which need to be considered. Moreover, the
leaching of NO3-N during N conversion should not be neglected. After
addition of N or inhibitor, the turnover of external and endogenous N can be
further investigated by 15N isotope labeling.
Conclusion
A significantly
different response of N2O
emissions to N and NI additions
from Fluvisols under different long-term fertilization regimes. N addition significantly increased N2O emissions, with
the highest increase rate in the soil of long-term NPK
fertilization and the lowest increase rate in the soil of long-term NPKM fertilization. NI addition significantly decreased N2O
emissions, with the lowest decrease rate in the soil of long-term M fertilization.
Those differences of N2O emissions in
response to N and NI additions were mainly resulted from the difference of soil
organic matters. It can be concluded that for soils with lower organic matter
content, chemical N fertilizer addition would cause more N2O
emissions; nevertheless, addition of NI had higher effects on N2O emissions
from these soils. Therefore, the application of nitrification inhibitor in
field with lower soil organic matter (e.g., soils after long-term
chemical NPK fertilization) is recommended, to better mitigate the global
warming potential.
Acknowledgements
This work was jointly supported by the National Natural
Science Foundation of China (42205173, 32272218), the earmarked fund for CARS - Green manure
(CARS-22), and the Innovation Program of CAAS (CAAS-S2021ZL06).
Author Contributions
XZ: methodology, data curation and writing-original draft
preparation, HQ: methodology and validation, SL: resources, FX: resources, YJ:
writing-review and editing, FD: writing-review and editing, AD: writing-review
and editing, ZS: writing-review and editing, HC: resources, writing-review and
editing, WZ: supervision, CZ: Conceptualization.
Conflicts of Interest
The author declares no conflict of interest
Data Availability
All new research results were presented in this article
Ethics Approval
Not applicable.
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