Introduction
Anhui is an important food production base in China with
average annual planting area of wheat (Triticum aestivum L.) of 2.4 million ha (Zhang et al. 2018). The amount of chemical
fertilizers used in Anhui is 33.86% higher than that regulated by China’s
ecological township construction (Dong and Liu 2018). However, the excessive
use of chemical fertilizers gradually decreases the marginal effect of
production, slightly increases the crop yield while increase greenhouse gas
emissions and cause environmental pollution. The contribution rate of nitrous
oxide (N2O), carbon dioxide (CO2) and methane (CH4)
to global warming in the atmosphere reaches 80%, and N2O emitted by
the application of chemical fertilizers accounts for 25–82% of the total N2O
emissions of the soil. The global warming potential of N2O is
298-fold higher than of CO2, and that of CH4 is 25-fold
higher than that of CO2 (Li et
al. 2018).
Research on reducing the application of chemical
fertilizers and greenhouse gas emissions has become a hot topic. Using
slow-release fertilizers, adding nitrification inhibitors, incorporating
organic fertilizers, returning straw to the fields, and using biochar and
precision agriculture are the main research areas (Ali et al. 2017; Hussain et al.
2017). The high-temperature compost of crop straw is one of the effective
methods used to treat the combination of rural breeding industry. It cannot
only prevent pests and diseases but also replace fertilizers. Straw returning
to the soil can replace fertilizer and reduce CH4 emissions by 23.6%, but it will increase N2O gas emissions
(Li et al. 2018). Nitrification inhibitors are used to reduce the
emission of N2O. Dicyandiamide (DCD) is a chemical nitrification
inhibitor that can reduce nitrogen oxide emissions by 49.3–79.4%. DCD is widely
used in the US, Europe, and other countries, but its application in China is
still at the preliminary research stage (Wang et al. 2017). No reports have reported on the combination of
compost and DCD. The present study combines compost with several chemical
fertilizers and DCD to determine the optimal dosage and its effects on
greenhouse gas emissions and wheat yield. Thus, the objectives of this study
were to clarify the green ecological agriculture model suitable for winter
wheat production with environmental-friendliness.
Materials and Methods
Description of experimental
site
This study was conducted in the plantation of Anhui
Science and Technology University (E117°33′39″, W32°52′49″) from October 2018 to June 2019. The annual average
temperature of the plantation was 15°C, the annual average rainfall was 1200 mm
and the frost-free period was 230 days. The previous crop sown was peanut (Arachis hypogaea L.).
The soil was yellow cinnamon soil that contains
Experimental
treatment and methods
Wheat was sown using ten treatments: CKN:
Determined items and methods
Greenhouse gas
collection, measurement, and emission calculations: Gas was collected using static black box sampling method
according to seasonal temperature. Gas was collected once a week from November
to December, once every 2 weeks from January to March and once a week from
April to June. Gas was collected every 10 min during sampling for a total of
three times. The gas was recorded while recording the temperature inside the
static dark box and surface. After gas samples were collected in each plot, the
gas syringe was brought to the laboratory and measured by gas chromatograph
Agilen
Global warming potential (GWP) of soil-emitted gas
The influence of
CO2, CH4, and N2O emitted by
wheat field on atmospheric greenhouse effect was quantitatively
evaluated by the combined action of three greenhouse gases emitted by soil and
was regarded as GWP. In 100-year scale, the global warming effects of
Grain yield and quality
At the maturity stage, a row of wheat was collected from
each plot, and the number of productive tillers and the plant height were
recorded. The average grain number per spike was calculated by randomly
selecting 20 spikes in each plot. The 1000-grain weight and the total grain
yield of each plot were calculated by drying and threshing. Grain quality was
measured by a NIR grain quality tester (PM-8188).
Data processing and statistical analysis
WPS office 2007 was used to perform data processing and
chart drawing. One-way ANONA of SPSS 20.0 was used to check the overall
significance of data while least significant test (LSD) was used to compare
treatments means at P < 0.05. The
data in the figure were the average value ± standard error of three repeated
measurements.
Results
Emission characteristics of N2O in soil
Different treatments had significant effect on
greenhouse gas emissions (Figs. 1–3). The N2O emission was
significantly higher in plots where alone chemical fertilizers (225 kg N,
Emission characteristics of CO
As shown in Fig. 2, the CO2 emission of CKN treatment was the highest in each stage
while the application of DCD by biomass composting reduced the emission of CO2
to the atmosphere, but the overall trend was relatively consistent. The CO2 emission of T1D3 was 16.9 and
7.8% lower than the N2O emission in CKN and T1D1
treatments on March 27, respectively (Fig. 2); however, the CO2 emission of CK0 was still lowest. At 34 d after wheat
sowing, CO2 emission showed the peak value. After the peak, wheat
entered the wintering period, and the emission flux of CO2 was low.
In March, wheat entered the regreening period. As the temperature increased,
the growth rate of wheat and the CO2 emission flux increased. The CO2
emission gradually decreased after April. The CO2 emissions of each
treatment were always higher than that of CK0, thereby indicating that the use
of fertilizer increased the emission of CO2 (Fig. 2).
Fig. 1: N2O Emission flux in wheat soil under crop
residue compost added nitrification inhibitor
Here CKN:
Fig. 2: CO2 Emission flux in wheat soil under crop
residue compost added nitrification
Here CKN:
Table
1: Total emission of greenhouse gas in wheat
field with compost return added nitrification inhibitor replaces part of
chemical fertilizer
Treatments |
Total CO2 emission (kg ha-1) |
Total CH4 emission (kg ha-1) |
Total N2O emission (kg ha-1) |
Total GWP (kg ha-1) |
CKN |
363.3 ± 1.8i |
7.4 ± |
0.5 ± 0.0i |
697.3d |
CK0 |
521.7 ± |
-17.4 ± |
3.7 ± |
1189.3a |
T1D1 |
408.3 ± |
-21.6 ± |
2.3 ± |
553.7e |
T1D2 |
382.7 ± |
-32.1 ± 0.4j |
1.9 ± 0.0e |
146.4g |
T1D3 |
357.2 ± 5.8j |
-14.0 ± 0.2d |
1.3 ± 0.0h |
394.6f |
T1D4 |
373.3 ± 3.5h |
-31.6 ± 0.3i |
1.6 ± |
60.1h |
T2D1 |
459.4 ± 0.9b |
-21.2 ± 0.0b |
3.2 ± |
883.0c |
T2D2 |
449.5 ± |
-23.9 ± 0.1h |
2.7 ± 0.0b |
656.6d |
T2D3 |
423.7 ± 5.0e |
-14.4 ± 0.2e |
1.8 ± |
600.1e |
T2D4 |
434.4 ± 3.5d |
-5.7 ± |
2.1 ± 0.0d |
917.7b |
Means (± standard deviation) sharing same letters differ
non-significantly at P ≤ 0.05
Here CKN:
Emission characteristics of CH
The CH4 emissions didn’t have significant
different in biomass compost and DCD treatments as shown in Fig. 3. The CH4
emissions in the wheat growth stage were mostly negative, and the absorption
and emission of CH
Fig. 3: CH4 Emission flux in wheat soil under crop
residue compost added nitrification
Here CKN:
Total
emission of greenhouse gas
Applied treatments had significant effect on total
emissions of CH4, CO2 and N2O as well as
global warming potential (GWP) (Table 1). Total emissions of CH4, CO2
and N2O as well as GWP were higher in CKN compared with all
treatments and lower in CK0 (Table 1). The application of DCD by biomass
composting reduced the emission of CO2, N2O. The CO2 and N2O emissions in T1D3 were 31.5 and
64.7 lower than CKN and T1D1, respectively. The total GWP of T1D3 was the highest and DCD
treatment significantly decreased GWP (Table 1).
Analysis of wheat yield and yield composition
According to the actual weighing and measurement of wheat
after harvest, the interaction between nitrogen-reducing compost replacement
and DCD was significant, with the highest T2D3 of 5998 kg
ha-1. In the two nitrogen reduction treatments, the yield increased
with increasing nitrification inhibitors. The highest yield exceeded the
fertilization mode, but D4 did not exceed the yield D3.
Hence, DCD of >
Wheat quality analysis
The use of organic fertilizers along with DCD, instead
of chemical fertilizers, significantly improved the quality of wheat (Table 3).
The increase was significant compared with the situation without fertilizer
application and chemical fertilizer application, especially T1D3,
which led to the highest protein and amylopectin contents. The protein content
and amylopectin contents of T1D3 wheat were increased by
7.9–13.9% and 7.9–14.0% than CH0, respectively (Table 3).
Discussion
The addition of nitrification inhibitor DCD significantly
reduced the emission peak and total discharge of N2O and CO2
by 11.9–31.5% compared with traditional fertilizer control treatment,
consistent with previously reported findings (Xu et al. 2016). Nitrogen in urea exists in the form of ammonium N,
and the absorption of wheat is mainly nitrate N. Therefore, the ammonium
nitrogen of urea must undergo nitrification in the soil, and N2O is
one of the important intermediate products of nitrification.
Conventional straw returning to the field increased the
N content in the soil, thereby promoting nitrification and denitrification and
further increasing N2O emissions. Moreover, the N2O
emission of straw returning to the field was ~25% higher than that of not
returning (Li et al. 2018). In the
present study, the addition of DCD to straw compost for replacing chemical
fertilizer significantly inhibited the nitrification and denitrification
reactions. The N2O emission after DCD addition was lower than that
of conventional fertilizer application, similar to a previous study that
reported that the application of organic fertilizer and decomposed manure can
also reduce N2O emissions (Ren
et al. 2019). Organic fertilizer and decomposed manure undergo full aerobic
fermentation of organic matter. Thus, N is relatively stable, and straw
directly returning to the field has not become thoroughly decomposed. The
process of decomposition mainly includes carbon–nitrogen conversion. When
microorganisms decompose cellulose, hemicellulose, lignin, and other organic
matter, N undergoes numerous nitrification and denitrification cycles. This
process also exacerbates nitrification and denitrification in the soil, thereby
promoting N2O emission. However, decomposed straw compost and manure
reduce nitrification and denitrification and decrease
the emission of N2O.
As a nitrification inhibitor, DCD is widely used in
Europe and the US. In this study, the effect of
Green agricultural products are one of the research
hotspots in recent years. The reduction of chemical fertilizer and the
substitution of organic fertilizer can improve the quality of agricultural
products, but also bring about the reduction of yield. While nitrification
inhibitor can reduce the gas emission, it can also increase the yield. It has
been reported that adding 5% nitrification inhibitor DCD and 0.5% urease
inhibitor can reduce the N2O emission by 40% compared with
traditional fertilization 60%, and the yield increased by 21% (Zhu et al. 2019). This experiment did not
achieve such a significant effect; maybe because the application effect of
compost is relatively slow, long-term positioning should get better effect.
Table
2: Effects of composting return and
nitrification inhibitors on wheat grain yield
Treatments |
Plant height (cm) |
Number of productive tillers (m-2) |
Number of grains per spike |
1000-grain weight (g ) |
Grain yield (kg ha-1) |
CKN |
72.1 ± |
528.6 ± |
34.6 ± 1.2b |
42.3 ± 3.5b |
5946 ± |
CK0 |
65.0 ± 0.5d |
461.3 ± |
29.0 ± |
39.7 ± 2.3b |
5023 ± |
T1D1 |
73.2 ± 1.5b |
525.4 ± |
34.4 ± 1.1b |
42.6 ± 0.6b |
5887 ± 23.8b |
T1D2 |
73.8 ± |
522.1 ± |
34.8 ± 1.5b |
42.7 ± 0.6b |
5907 ± |
T1D3 |
74.5 ± |
514.3 ± 1.3b |
35.9 ± |
43.1 ± |
5929 ± |
T1D4 |
73.6 ± 0.4b |
514.6 ± 1.3b |
35.5 ± |
42.9 ± 1.3b |
5908 ± |
T2D1 |
72.5 ± |
521.3 ± |
35.1 ± |
42.2 ± 1.7b |
5865 ± 92.2b |
T2D2 |
72.8 ± 0.6b |
514.6 ± 1.1b |
35.8 ± |
42.4 ± 0.4b |
5901 ± |
T2D3 |
73.6 ± 1.1b |
518.2 ± 1.3b |
35.7 ± |
42.8 ± 0.6b |
5998 ± |
T2D4 |
73.1 ± 1.1b |
525.5 ± |
34.9 ± 0.6b |
42.4 ± 0.9b |
5916 ± |
Means (± standard deviation) sharing same letters differ
non-significantly at P ≤ 0.05
Here CKN:
Table
3: Effects of composting return and
nitrification inhibitors on quality of wheat
Treatments |
Protein (%) |
Gluten (%) |
Sedimentation value (ml) |
Amylopectin (%) |
|
CKN |
10.7 ± 0.2b |
810.5 ± 0.1b |
21.0 ± |
5.45 ± 0.32b |
55.8 ± 0.15b |
CK0 |
9.5 ± |
790.5 ± |
19.1 ± 0.2b |
3.75 ± |
50.1 ± |
T1D1 |
11.8 ± |
899.7 ± |
23.3 ± |
6.05 ± |
61.9 ± |
T1D2 |
12.0 ± |
907.8 ± |
23.6 ± |
6.10 ± |
62.5 ± |
T1D3 |
12.2 ± |
924.0 ± |
23.9 ± |
6.21 ± |
63.6 ± |
T1D4 |
12.1 ± |
915.9 ± |
23.7 ± |
6.16 ± |
63.1 ± |
T2D1 |
11.5 ± |
875.3 ± |
22.7 ± |
5.89 ± |
60.3 ± |
T2D2 |
11.6 ± |
883.4 ± |
22.9 ± |
5.94 ± |
60.8 ± |
T2D3 |
11.7 ± |
891.5 ± |
23.1 ± |
5.99 ± |
61.4 ± |
T2D4 |
11.7 ± |
887.5 ± |
23.1 ± |
5.97 ± |
61.1 ± |
Means (± standard deviation) sharing same letters differ
non-significantly at P ≤ 0.05
Here CKN:
Conclusion
Straw compost replacement with chemical fertilizers
along with DCD reduced greenhouse gas emissions and improved wheat yield and
quality. The use of 15 t ha-1 straw compost +
Acknowledgements
The first author acknowledges the financial grant from
Science and Technology Major Projects of Anhui Province (18030701190); National
Key R&D Program of China (2018YFF0213500); Natural science Research Program
in Universities in Anhui (KJ
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