Open AccessArticle

Estimation of Nitrous Oxide Emissions from Agricultural Sources and Characterization of Spatial and Temporal Changes in Anhui Province (China)

Zhou Ye

^1,2,

Yujuan Sun

³,

Xianglin Zhang

¹ and

Youzhi Yao

^1,2,*

College of Materials Engineering, Wuhu Institute of Technology, Wuhu 241003, China

Wuhu Environmental Monitoring and Control Engineering Technology Research Center, Wuhu 241002, China

College of Ecology and Environment, Anhui Normal University, Wuhu 241000, China

Author to whom correspondence should be addressed.

Atmosphere 2024, 15(12), 1538; https://doi.org/10.3390/atmos15121538

Submission received: 16 November 2024 / Revised: 11 December 2024 / Accepted: 19 December 2024 / Published: 22 December 2024

(This article belongs to the Section Air Quality)

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Figure 1
Changes in the number of farmed animals: (a) for non-dairy cows (×103), (b) for poultry (×105), (c) for sheep (×103), and (d) for pigs (×105). "> Figure 2
Mechanism diagram of nitrous oxide-emissions from agricultural sources [<a href="#B21-atmosphere-15-01538" class="html-bibr">21</a>]. "> Figure 3
Historical changes in nitrous oxide emissions from agricultural activities in Anhui Province. "> Figure 4
Annual emissions of nitrous oxide from agricultural land in Anhui Province. "> Figure 5
Annual emissions of nitrous oxide from animal fecal management. "> Figure 6
Statistical chart of nitrous oxide emissions from agricultural land at some prefecture-level cities in Anhui Province (a) and nitrous oxide emissions from livestock and poultry manure management (b). "> Figure 7
Contribution of animal manure management (a) and agricultural land (b) to nitrous oxide emissions in some prefecture-level cities of Anhui Province in 2014 and 2022. ">

Versions Notes

Abstract

To evaluate the estimation and spatiotemporal variation characteristics of nitrous oxide emissions from agricultural sources in Anhui Province, the nitrous oxide emissions generated during crop cultivation and manure management were assessed based on the recommended methods in the “Guidelines for Provincial Greenhouse Gas Inventories” and official statistical data. The results showed that the overall emission of nitrous oxide from agricultural land showed a downward trend, reaching a valley value in 2019 with an emission of 2.83 × 10⁴ tons. The annual average emissions of nitrous oxide from agricultural land and manure management account for 80.98% and 19.02% of the total annual average emissions of nitrous oxide from agricultural activities in Anhui Province, respectively. Both agricultural land emissions and livestock manure management show a trend of nitrous oxide emissions decreasing from the northern region of Anhui > central region of Anhui > southern region of Anhui. In this paper, we explored and discussed the intrinsic driving factors behind the spatiotemporal changes in nitrous oxide emissions, and analyzed the potential for future emission reductions. It is suggested that the emissions of nitrous oxide from agricultural sources can be reduced through measures such as reasonable nitrogen application, adjustment of aquaculture structures, and the improvement of manure treatment methods, providing a theoretical reference for the estimation of greenhouse gas emissions from agricultural sources.

Keywords:

Anhui Province; agriculture; nitrous oxide emissions; greenhouse gases

1. Introduction

Against the backdrop of an increasingly severe global climate, greenhouse gas emissions have become a focus of international attention [1]. Nitrous oxide (N₂O), as an important greenhouse gas, has an impact on global climate change that cannot be ignored [2], and its global warming potential (GWP) is 273 times higher than that of carbon dioxide (CO₂) on a 100-year scale [3]. Related studies have shown that agricultural activities are the main source of nitrous oxide in the atmosphere [4], with a contribution of more than 70%. According to the Intergovernmental Panel on Climate Change (IPCC) report, two-thirds of nitrous oxide emissions come from the use of agricultural nitrogen fertilizers and manure organic fertilizers [5], which account for 84% of anthropogenic N₂O emissions [6].

At present, the global annual application of nitrogen fertilizers to farmland is as high as 120 million tons [7], and is still showing an increasing trend year by year. However, from the perspective of nitrogen utilization efficiency, the comprehensive utilization efficiency is less than 50%. After nitrogen fertilizer is applied to the soil, a large amount of nitrogen is lost into the environment in the form of ammonia volatilization, nitrous oxide emissions, and leaching runoff [8]. Nitrous oxide enters the air to participate in photochemical reactions, destroying the ozone layer, and nitrogen deposition accelerates its emission rate, leading to soil acidification. Nitrous oxide enters the groundwater through surface runoff, etc., causing eutrophication of water bodies and imbalance in the ecosystem [9]. Therefore, controlling and reducing nitrous oxide emissions is important for controlling the balance of the ecosystem.

To reasonably and accurately estimate the greenhouse gas emissions from agricultural sources, relevant scholars have conducted research on nitrous oxide emissions. For example, Li et al. used the regional nitrogen cycling model IAP-N method to preliminarily estimate the nitrous oxide emissions from the ecosystem in Fujian Province, resulting in a value of 3.13 × 10⁴ t [10]. Zhu et al. used the IPCC method to estimate the nitrous oxide emissions from agriculture in Jilin Province to be 4.27 × 10⁴ t [11]. Ma et al. estimated the agricultural nitrous oxide emissions in Beijing and found that the agricultural nitrous oxide emissions in Beijing in 2019 were 2.61 × 10⁶ t CO₂ [12]. Yang et al. found that the agricultural greenhouse gas emissions in Anhui Province remained at a level of 3 × 10³ tons through their study on the characteristics of agricultural greenhouse gas emissions in Anhui Province [13]. Bai et al. studied the N₂O emissions from farmland soil in North China, and concluded that the fluxes of N₂O emissions from maize in summer were much higher than those from wheat in winter [14]. However, N₂O emissions naturally show large differences between different provinces and regions; due to great differences in soil and climate, there are naturally significant variations in nitrous oxide emissions. The National Development and Reform Commission (NDRC) issued the “Guidelines for the Preparation of Provincial Greenhouse Gas Inventories (for Trial Implementation)” [15] in 2011, which attracted much attention in the agricultural environment field and in society as a whole upon its promulgation.

In this work, we take the 2013 N₂O emissions from agricultural sources in Anhui Province as the base year, estimate the N₂O emissions from agricultural sources in Anhui Province in the past 10 years (2013–2022) by combining emission factors and N₂O emission models based on the standard parameters, coefficients, and factors stipulated in the “Guidelines for the Preparation of Provincial Greenhouse Gas Inventories (for Trial Implementation)”, and draw a trend chart of the changes in N₂O emissions and analyze various factors affecting the N₂O emissions. Nitrous oxide emission is analyzed in the light of these changes, aiming to provide a basis for reducing nitrous oxide emissions from agricultural sources, and can also serve as a theoretical reference for estimating greenhouse gas emissions from agricultural sources.

2. Research Methodology and Rationale

2.1. Overview of the Study Area

Anhui Province is a typical agricultural and grain-producing province, located in the hinterland of East China, adjacent to the river near the sea. The total land area of the province is about 1.4 × 10⁵ square kilometers, including more than 5.87 × 10⁴ square kilometers [16]. The agricultural climate conditions are suitable, with an average annual temperature of 14–17 °C and an annual rainfall of 700–1700 mm. The planting area of perennial crops exceeds 8.7 × 10⁴ square kilometers, of which the area of grain crops accounts for more than 75%, ranking fourth in the country. Anhui has distinct regional characteristics and is divided into three regions. There are six prefecture-level cities in the north, including Fuyang, Huainan, Huaibei, Bengbu, Bozhou, and Suzhou; in central Anhui, there are mainly four prefecture-level cities, including Hefei (including Chao hu), Anqing, Chuzhou, and Lu’an; and to the south of Anhui, there are six prefecture-level cities, including Wuhu, Ma’anshan, Tongling, Mount Huangshan, Chizhou, and Xuancheng. In addition, Anhui Province is a prominent hub for animal husbandry in China. In 2022, the province had a total of 1.067 × 10⁶ cattle, 1.6558 × 10⁷ pigs, 6.3575 × 10⁶ sheep, and 3.22842 × 10⁸ poultry. Figure 1 shows the changes in the numbers of several farmed animals from 2013 to 2022, with poultry having the highest number of farmed animals (the data were sourced from the annual statistical yearbooks of Anhui Province).

2.2. Principles of Agricultural Nitrous Oxide Emissions

Ammonia oxidation, nitrifying bacteria denitrification, nitrite oxidation, heterotrophic denitrification, anaerobic ammonia oxidation, and nitrate reduction to ammonium (DNRA, or nitrate ammonification) are the main pathways for the production and consumption of nitrous oxide, each regulated by different microorganisms (Figure 2) [17]. The main sources of nitrous oxide emissions in soil are nitrification-related pathways (including ammonia oxidation and nitrifying bacterial denitrification) and heterotrophic denitrification [18].

Heterotrophic denitrification is considered the main respiratory process of microorganisms [19]. It is accomplished by multiple bacteria in multiple steps, reducing N (

N O_{3}^{-}

and

N O_{2}^{-}

) to the gaseous products NO, N₂O, and N₂ under limited oxygen conditions.

Nitrification is the aerobic oxidation of ammonium through nitrite (

N H_{4}^{+}

→NH₂OH/HNO→

N O_{2}^{-}

→

N O_{3}^{-}

) to nitrate, which is carried out by a specialized prokaryotic organism. The first step (

N H_{4}^{+}

→NH₂OH/HNO→

N O_{2}^{-}

) is oxidation, catalyzed by the amoA gene of oxygenase (AMO). The second step (

N O_{2}^{-}

→

N O_{3}^{-}

) is regulated by the nxrB gene of nitrite oxidoreductase in nitrite-oxidizing bacteria (NOB). The oxidation of

N H_{4}^{+}

is considered the rate-limiting step in the entire nitrification process and plays an important role in the rate of nitrification reaction [20]. It is estimated that this process can account for over 80% of nitrous oxide emissions. The specific values are influenced by the type of soil ecosystem, temperature regulation, and water content balance.

Figure 2. Mechanism diagram of nitrous oxide-emissions from agricultural sources [21].

2.3. Methodology and Data Sources

2.3.1. Nitrous Oxide Emissions from Agricultural Land

Direct Emissions

According to the “Guidelines for Compilation of Provincial Greenhouse Gas Inventories (Trial)” [15] (the same below), the main sources of direct nitrogen emissions are as follows: fertilizer nitrogen (denoted by “N_fertilizer”), manure nitrogen (denoted by “N_manure”), and straw returning nitrogen (denoted by “N_straw”), while EF_direct is the nitrous oxide emission factor from agricultural land. According to Equations (1)–(4), the direct emissions of nitrous oxide from agricultural land can be calculated. The caliber of the calculation of the rural population was finalized after consulting the Anhui Provincial Bureau of Statistics and other relevant departments.

{N_{2} O}_{d i r e c t} = (N_{m a n u r e} + N_{f e r t i l i z e r} + N_{s t r a w}) \times {E F}_{d i r e c t}

(1)

N_{manure} = (total N excretion of livestock and poultry + total excretion of rural population) \times [1 - leaching runoff loss rate (15 %) - volatilization loss rate (20 %)] - N_{2} O livestock and poultry manure emissions

(2)

N_{straw} = (grain yield / economic coefficient - grain yield) \times dry weight ratio \times Straw returning rate \times straw nitrogen content + grain yield / economic coefficient \times root shoot ratio \times dry weight ratio \times straw nitrogen content

(3)

R u r a l p o p u l a t i o n = P e r m a n e n t p o p u l a t i o n \times (1 - U r b a n i z a t i o n r a t e)

(4)

Indirect Emissions

Indirect emissions of nitrous oxide result from atmospheric nitrogen deposition. They are mainly derived from the volatilization of NH₃ and NO_X from the agricultural excretion of nitrogen (including the excretion of nitrogen from livestock and poultry manure and the excretion of nitrogen from the rural population (denoted by “N_{agricultural excretion}”) and nitrogen inputs from agricultural land (denoted by “N_input”). The emission factor of 0.01 was used, and the formula was calculated as follows [15]:

N_{2} O_{d e p o s i t i o n} = (N_{a g r i c u l t u r a l e x c r e t i o n} \times 20 % + N_{i n p u t} \times 10 %) \times 0.01

(5)

Nitrous oxide emissions due to losses from nitrogen leaching from agricultural land and runoff were calculated using Equation (6) below (the amount of nitrogen lost from this action was determined by estimating 20% of the total nitrogen input to the agricultural land).

N_{2} O_{leaching runoff} = N_{input} \times 20 % \times 0.0075

(6)

Total Emissions

Total nitrous oxide emissions are equal to the nitrogen input to each emission process multiplied by its corresponding nitrous oxide emission factor [15].

E_{N_{2} O} = \sum (N_{i n p u t} \times E F)

(7)

2.3.2. Nitrous Oxide Emissions from Animal Manure

The formula for calculating nitrous oxide emissions from specific animal manure management is shown in Equation (8) [15].

E_{N_{2} O, m a n u r e, i} = E F_{N_{2} O, m a n u r e, i} \times A P_{i} \times 10^{- 7}

(8)

In the formula,

E_{N_{2} O, m a n u r e, i}

represents the nitrous oxide emissions from animal manure management for the i-th species, unit: 1 × 10⁴ tons of N₂O/year;

{E F}_{N_{2} O, m a n u r e, i}

is the management of nitrous oxide emission factors for specific population feces, unit: kg/head/year; and

{A P}_{i}

is the number of animals of species i in head.

2.3.3. Activity Level Data Sources Identified

To determine the activity level of nitrous oxide emissions from agricultural land, the direct and indirect emissions of N₂O from agricultural land were obtained by certain calculations from the effects of fertilizer N, manure N, straw return N, and N leaching runoff from agricultural land. The original calculation data were derived from the Anhui Statistical Yearbooks of past years. Fertilizer nitrogen covers nitrogen fertilizers and compound fertilizers in the nitrogen component, after reviewing the relevant literature and historical empirical data [11,22,23]. By analyzing the actual use of compound fertilizers in farming in Anhui Province, the compound fertilizer nitrogen element is analyzed; for the conversion of pure calculation of nitrogen content, the value of the purity rate is 15%. Since the annual average nitrogen contribution of the rural population and the direct straw return rate are not fully reflected in the statistical yearbook of Anhui Province, this article refers to the value of such research in Fujian Province [10], and the annual average nitrogen contribution of the rural population is 5.4 kg/year/person and the direct straw return rate is 0.171.

Activity level data on nitrous oxide emissions from animal manure management: The values of nitrogen excretion by different animals are shown in Table 1.

2.4. Determination of Emission Factors

The determination of emission factors was achieved through a series of scientific methods and models to quantify the greenhouse gas emissions generated by a certain activity or process. The emission factor refers to a representative value that links the quantity of pollutants emitted into the atmosphere to the activities that produce those pollutants.

The determination of nitrous oxide emission factors from agricultural land is shown in Formula (1). This paper followed the average values of emission factors recommended in the Guidelines for the Preparation of Provincial Greenhouse Gas Inventories (for Trial Implementation) as the core calculation scale to ensure the accuracy and uniformity of the data [15]. In Anhui Province, the direct N₂O emission factor is 0.0109, with a range of 0.0026~0.022, while the N₂O emission factor caused by atmospheric nitrogen deposition is 0.0100, and the N₂O emission factor caused by nitrogen leaching and runoff loss is 0.0075.

The emission factors in Formula (8) were selected based on the nitrous oxide emission factors from animal manure management, as shown in Table 2.

3. Result Analysis and Discussion

3.1. Time-Varying Characteristics of Nitrous Oxide Emissions from Agricultural Sources in Anhui Province

3.1.1. Characteristics of Temporal Changes in Nitrous Oxide Emissions from Agricultural Sources

Figure 3 shows the changes in nitrous oxide emissions from agricultural sources in Anhui Province over the years from 2013 to 2022. From a general point of view, the total amount of nitrous oxide emissions from agricultural sources in Anhui Province shows a trend of first decreasing and then slowly increasing. From a quantitative point of view, the total amount of nitrous oxide emissions from agricultural sources in Anhui Province decreased from 3.36 × 10⁴ t in 2013 to 2.83 × 10⁴ t in 2019, with a decrease of 0.53 × 10⁴ t, or 15.8%. From the following figure, it can be clearly seen that agricultural land is the key emission source of nitrous oxide from agricultural sources in Anhui Province, the average annual share of agricultural land emissions is 80.98%, and the average annual share of manure management emissions is 19.02%. The average annual emissions of nitrous oxide from agricultural land in Anhui Province from 2013 to 2022 are 2.49 × 10⁴ t/a, and the emissions from agricultural land in 2022 are 2.27 × 10⁴ t, decreased by 0.50 × 10⁴ t compared with 2013; the average emissions of nitrous oxide from livestock and poultry manure management are 0.58 × 10⁴ t/a, the emissions in 2013 are 0.60 × 10⁴ t, and the emissions in 2022 are 0.68 × 10⁴ t, with an increase of 12.5%.

3.1.2. Characteristics of Temporal Changes in Nitrous Oxide Emissions from Agricultural Land

The dynamic trend of direct and indirect nitrous oxide emissions from agricultural land in Anhui Province is shown in Figure 4. It can be seen that the direct and indirect emissions of nitrous oxide from agricultural land show a decreasing trend year by year over time until 2019, when the emissions reached the lowest level of the calendar year, and then showed an increasing and then decreasing trend year by year, but the overall fluctuation is not large.

The specific values of nitrous oxide emissions from agricultural land in Anhui Province are shown in Table 3 below. In 2013, the total amount of nitrous oxide emissions from agricultural land in Anhui Province was 2.76 × 104 t, of which the direct emissions were 2.13 × 10⁴ t (accounting for 77.17% of the total emissions), and the indirect emissions were 0.63 × 10⁴ t (accounting for 22.83%); in 2019, the total amount of nitrous oxide emissions from agricultural land in Anhui Province was 2.31 × 104 t, of which the direct emissions of nitrous oxide were 1.78 × 10⁴ t (accounting for 77.06%) and the indirect emissions were 0.52 × 10⁴ t (accounting for 22.51%). Due to the continuous reduction in agricultural fertilizer nitrogen application in Anhui Province from 2013 to 2019, agricultural nitrous oxide emissions decreased year by year [16]. The total amount of nitrous oxide emissions from agricultural land in Anhui Province in 2022 was 2.26 × 104 t, of which the direct emissions of nitrous oxide were 1.73 × 10⁴ t (accounting for 76.55%) and the indirect emissions were 0.54 × 10⁴ t (accounting for 23.89%).

3.1.3. Characterization of Temporal Changes in Nitrous Oxide Emissions from Animal Manure Management

The nitrous oxide emissions from major animal manure management over the years are shown in Figure 5. From the year-to-year trend, the nitrous oxide emissions of major animals all showed a trend of decreasing and then increasing. Among them, the emission of nitrous oxide from the manure management of non-dairy cattle decreased from 0.07 × 10⁴ t in 2013 to 0.06 × 10⁴ t in 2016, with a decrease of 14.29%; the emission of nitrous oxide from the manure management of non-dairy cattle in 2022 was 0.09 × 10⁴ t, with an increase of 28.6% compared with that of 2013; the emission of nitrous oxide from the manure management of sheep decreased from 0.05 × 10 10⁴ t to 0.04 × 10⁴ t in 2016, and by 2022, the nitrous oxide emissions from manure management of sheep were 0.07 × 10⁴ t, an increase of 40% compared to 2013; the nitrous oxide emissions from the manure management of poultry reached its lowest level in 2017, with an emission of 0.16×10⁴ t, which is not a significant performance in terms of the overall trend of change; and for the nitrous oxide emissions from swine manure management in 2013–2019, nitrous oxide emissions decreased from 0.27 × 10⁴ t to 0.19 × 10⁴ t, a decrease of 29.63%, and in 2022, nitrous oxide emissions from swine manure management increased to 0.29 × 10⁴ t, an increase of 7.4% compared to 2013. In terms of animal species, the largest nitrous oxide emissions are from sheep and the smallest are from poultry.

3.2. Characteristics of Spatial Changes in Nitrous Oxide Emissions from Agricultural Sources in Some Areas of Anhui Province

The statistical results of the total nitrous oxide emissions from agricultural land and livestock manure management at some prefecture-level cities in Anhui Province from 2013 to 2022 are shown in Figure 6. Anhui Province is divided into north and south regions, with the Huaihe River as the boundary. In order to analyze and compare the differences in nitrous oxide emissions from agricultural sources between different regions, this article selected eight prefecture-level cities in central, southern, and northern Anhui as the research objects, in which Fuyang City and Suzhou City were selected as the representatives of northern Anhui; Wuhu City, Anqing City, and Mount Huangshan City as the representatives of southern Anhui (considering the balance of the distribution of the selected prefecture-level cities, Anqing City takes into account many characteristics of southern Anhui, and analyzes them as the representatives of southern Anhui); and Hefei City, Chuzhou City, and Lu’an City are the representatives of central Anhui. From the figure below, it can be seen that there are certain differences in nitrous oxide emissions from agricultural land in the north and south of Anhui Province due to factors such as geographical location, economy, and environment. The area with the largest amount of agricultural land emissions in 2014 was Lu’an City in central Anhui Province, with = agricultural land emissions of 0.35 × 10⁴ tons; the emissions from livestock and poultry manure management were mainly concentrated in the northern Anhui region, such as Fuyang City and Suzhou City. In 2014, the emissions of nitrous oxide from livestock and poultry manure management reached 0.11 × 10⁴ t and 0.12 × 10⁴ t, respectively. In 2018 and 2020, emissions in various regions significantly decreased. According to the statistical yearbook data of Anhui Province over the years, the geographical environment in southern Anhui is superior, suitable for multiseason crop growth, and requires a large amount of fertilizer. Some cities in the central Anhui region, such as Chuzhou City, have a relatively large proportion of rice planting area, and the amount of irrigation water also has a certain impact on the emission of nitrous oxide. However, in the northern Anhui region (such as Fuyang City), there are a large number of animal farms, and the estimated emissions from the management of livestock and poultry manure are relatively high. Therefore, there is a significant difference in nitrous oxide emissions between the central, southern, and northern regions of Anhui.

In order to more intuitively analyze the characteristics of nitrous oxide emissions from agricultural activities, the article analyzes the nitrous oxide emissions from agricultural land and animal manure management in each region in 2014 and 2020, and the comparison is shown in Figure 7. For nitrous oxide emissions from animal manure management and nitrous oxide emissions from agricultural land, the contribution rate of nitrous oxide emissions was the largest in northern Anhui in the 2 years, followed by central Anhui, with southern Anhui being the smallest. Comparing 2014 and 2020, in terms of nitrous oxide emissions from animal manure management, the contribution rate of the northern Anhui region decreased from 40% to 33.3%, the contribution rate of the central Anhui region decreased from 26.7% to 13.3%, and the contribution rate of the southern Anhui region basically remained stable; in terms of nitrous oxide emissions from agricultural land, the contribution rate of the northern Anhui region decreased from 36.1% to 30.8%, the contribution rate of the central Anhui region decreased from 32.9% to 20.4%, and the contribution rate of the southern Anhui region decreased from 15.4% to 11%.

3.3. Discussion

This study selected Anhui Province as its research object, and based on the relevant data released by the Anhui Provincial Department of Statistics, analyzed and estimated the nitrous oxide emissions from agricultural activities in Anhui Province. The results are as follows:

(1) Overall, from 2013 to 2022, the emissions of nitrous oxide from agricultural sources in Anhui Province showed a slow decrease followed by a slow increasing trend. In 2022, there was a decrease of 0.50 × 104 tons compared to 2013. Agricultural land is a key source of nitrous oxide emissions from agriculture in Anhui Province, with an average annual emission rate of 80.98%, while the average annual emission rate is 19.02% from manure management.

From the perspective of the mechanism of nitrous oxide production in agricultural land, the formation pathways of nitrous oxide in agricultural land include nitrification, denitrification (biological denitrification, chemical denitrification), and the transformation and reduction of nitrate nitrogen to ammonia. The most important ones are nitrification and denitrification, which can account for 70% to 90% of the total emissions. Therefore, controlling the emission of nitrous oxide from agricultural land mainly relies on inhibiting nitrification. The use of underground drip irrigation to improve microbial activity and the use of nitrification inhibitors to inhibit nitrifying bacteria are very effective control measures [24,25,26,27]. The amount of irrigation water also has a certain impact on the emission of nitrous oxide. In the production process, controlling the emission of nitrous oxide during irrigation and shallow water irrigation leads to lower emissions than long-term irrigation. This is because choosing controlled and shallow water irrigation can alternate nitrification and denitrification [28]. From the perspective of evaluation factors for nitrous oxide emissions from agricultural land, crops with large planting areas and high fertilizer application rates are positively correlated with nitrous oxide emissions from farmland [29]. Therefore, in order to reduce the emissions of nitrous oxide from agricultural land, emphasis should be placed on reducing fertilizer application, improving fertilizer utilization efficiency, and adjusting fertilizer structure. Researchers have pointed out that the use of the urea deep burial method produces nearly 30% less nitrous oxide emissions than the urea broadcasting method, and can increase net ecological benefits by nearly 48% [30]. In addition, using organic fertilizers and adding nitrogen fertilizer enhancers and biochar are also effective means to reduce soil nitrous oxide emissions [31,32].

(2) From a typological perspective, the emissions from agricultural land gradually decrease over time and then slowly increase again. The lowest emissions in 2019 were 2.31 × 10⁴ t, with direct nitrous oxide emissions of 1.78 × 10⁴ t (77.06%) and indirect emissions of 0.52 × 104 t (22.51%). The management of animal feces shows a trend of first decreasing and then increasing nitrous oxide emissions. Compared to 2013, the nitrous oxide emissions from the animal manure management of pigs, poultry, non-dairy cows, and sheep increased by 7.4%, 9.5%, 28.6%, and 40%, respectively, in 2022.

The nitrous oxide emissions in livestock and poultry manure management mainly come from the nitrification and denitrification processes under the composting state of early storage and treatment. From the perspective of livestock and poultry species, the nitrogen content in the excrement of different types of livestock and poultry varies greatly, resulting in significant differences in emissions. The annual nitrogen excretions per head of cows, non-dairy cows, goats, and pigs are 60–100 kg, 40–70 kg, 12–20 kg, and 16–20 kg, respectively [33]. Therefore, adjusting the breeding structure appropriately and selecting livestock and poultry with low emission factors is obviously more conducive to reducing nitrous oxide emissions. Starting from the perspective of production mechanisms, changing the storage environment and processing methods is also an effective means to reduce nitrous oxide emissions. The research results of Zhou et al. [34] indicate that the emission of nitrous oxide from stored feces under anaerobic conditions is much lower than that under fixed storage and grazing conditions.

(3) From a spatial perspective, the area with the largest amount of agricultural land emissions is Lu’an City in central Anhui Province, with an emission of 0.35 × 10⁴ tons; the emissions of livestock and poultry manure management are mainly concentrated in the northern Anhui region, with Fuyang City and Suzhou City achieving 0.11 × 10⁴ t and 0.12 × 10⁴ t, respectively, in 2014. In 2018 and 2020, emissions in various regions significantly decreased.

Therefore, selecting planting and breeding models that are suitable for local conditions and developing effective management measures are key to reducing emissions. The management and utilization of livestock and poultry manure should be strengthened, and the adoption of composting, biogas, and other treatment methods to reduce direct emissions. Exploring the integration of planting and breeding, and implementing the return of livestock and poultry manure to the field, are also important safeguarding measures for controlling greenhouse gas emissions [35,36].

4. Conclusions

This study sampled the methods recommended in the “Guidelines for Provincial Greenhouse Gas Inventories” and combined them with relevant data released by the statistical department of Anhui Province over the past 10 years to analyze and estimate the nitrous oxide emissions from agricultural activities in Anhui Province. Overall, from 2013 to 2022, the emissions of nitrous oxide from agricultural sources in Anhui Province showed a slow decrease followed by a slow increasing trend. In 2022, there was a decrease of 0.50 × 10⁴ tons compared to 2013. Compared to 2013, the nitrous oxide emissions from the animal manure management of pigs, poultry, non-dairy cows, and sheep increased by 7.4%, 9.5%, 28.6%, and 40%, respectively, in 2022. The emissions from agricultural land significantly decreased in all regions in 2018 and 2020. From the perspective of crop management, rational nitrogen application is key, including inhibiting fertilizer nitrification and controlling fertilizer application time. Adjusting the livestock and poultry manure management structure appropriately is an effective low-carbon measure. A new agricultural model that combines planting and breeding to scientifically control nitrous oxide emissions should be explored.

Author Contributions

Conceptualization, Z.Y. and Y.Y.; methodology, Z.Y.; software, Z.Y., Y.S. and X.Z.; validation, Z.Y.and Y.Y..; formal analysis, Z.Y., Y.S. and X.Z.; investigation, Y.S. and X.Z.; resources, X.Z.; data curation, Z.Y. and Y.S.; writing—original draft preparation, Y.S. and X.Z.; writing—review and editing, Y.Y.; visualization, Y.S.; supervision, Z.Y. and Y.Y.; project administration, Z.Y. and Y.Y.; funding acquisition, Z.Y. and Y.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Key Project of Natural Science Research in Anhui Province’s Universities (2022AH052204); Talent Engineering Project of Wuhu Institute of Technology (rc2023qnbj04) and Key research projects of Wuhu Institute of Technology (wzyzrzd202304).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data are available on request from the corresponding author. The data are not publicly available due to privacy.

Acknowledgments

This work was supported by Wuhu High Efficiency Environmental Protection Equipment Manufacturing and Operation Technology Research and Development Center, and the helpful comments of the anonymous reviewers.

Conflicts of Interest

The authors declare no conflicts of interest.

References

Chen, Y.; Meng, Y.; Weng, W.; Chen, Y.; Zhang, H.; Liao, P. Effects of nitrification inhibitor dicyandiamide application on rice yield and greenhouse gas emissions. China Rice 2024, 30, 26–29. [Google Scholar]
Ai, X. Research on Catalyst for Nitrous Oxide Decomposition of Nitric acid Plant Tail Gas. Master’s Thesis, Beijing Institute of Petrochemical Technology, Beijing, China, 2023. [Google Scholar]
Matthew, W.J.; Glen, P.P.; Thomas, G.; Robbie, M.A.; Clemens, S.; Johannes, G.; Richard, A.H.; Pierre, F.; Julia, P.; Corinne, L. National contributions to climate change due to historical emissions of carbon dioxide, methane, and nitrous oxide since. Sci. Data 2023, 10, 155. [Google Scholar]
Li, B.; Fan, C.; Zhang, H.; Chen, Z.; Sun, L.; Xiong, Z. Combined effects of nitrogen fertilization and biochar on the net global warming potential, greenhouse gas intensity and net ecosystem economic budget in intensive vegetable agriculture in southeastern China. Atmos. Environ. 2015, 100, 10–19. [Google Scholar] [CrossRef]
Jia, G.; Yang, N.; Wu, X. Situation and Suggestions for Non-CO₂ Greenhouse Gas Control in China. Environ. Impact Assess. 2023, 45, 1–7. [Google Scholar]
Li, C.; Liu, Z.; Gong, S. Effects of changing rice cropping patterns on CH₄ and N₂O emissions from paddy fields. J. Ecol. Environ. 2022, 31, 961–968. [Google Scholar]
Gu, B.; Zhang, X.; Lam, S.K. Cost-effective mitigation of nitrogen pollution from global croplands. Nature 2023, 613, 77–84. [Google Scholar] [CrossRef] [PubMed]
Shen, J.; Li, Y.; Wang, Y. Soil nitrogen cycling and environmental impacts in the subtropical hilly region of China: Evidence from measurements and modeling. Front. Agric. Sci. Eng. 2022, 9, 407–424. [Google Scholar]
Cheng, J.; Xu, L.; Fan, L. Effects of nitrogen application and temperature increase on nitrous oxide emission during the growth period of grayed Carex cinerascens (Carex cinerascens Kukenth.) wetland autumn grass at Poyang Lake. Lake Sci. 2024, 36, 1152–1162. [Google Scholar]
Li, Y.; Wang, Y.; Wang, C. Estimation and characterization of nitrous oxide emissions from agroecosystems in Fujian Province. Chin. J. Ecol. Agric. 2014, 22, 225–233. [Google Scholar] [CrossRef]
Zhu, Y.; Wang, X.; Zhao, X. Analysis of the current situation and spatial and temporal pattern of agricultural nitrous oxide emission in Jilin Province. Agric. Technol. 2023, 43, 80–83. [Google Scholar]
Wang, A.; Ma, W.; Wu, J. Changes and analysis of agricultural nitrous oxide emissions in Beijing from 2015 to 2019. China Agric. Resour. Zoning 2023, 44, 47–56. [Google Scholar]
Xie, L.; Yang, S.; Zhang, C. Characterization of greenhouse gas emissions from agricultural sources in Anhui Province. China Agron. Bull. 2020, 36, 88–91. [Google Scholar]
Bai, F.; Li, P.; Lu, H. Mechanisms of Nitrogen Reduction on Soil N₂O Emission Regulation in Wheat and Jade Rotation Farmland in North China. J. Irrig. Drain. 2024, 43, 95–104. [Google Scholar]
National Development and Reform Commission of the People’s Republic of China. Guidelines for the Preparation of Provincial Greenhouse Gas Inventories (Trial); National Development and Reform Commission: Beijing, China, 2011.
Anhui Agriculture and Rural Affairs Department. Agricultural Profile [EB/OL]. 4 June 2021. Available online: https://nync.ah.gov.cn/nygk/index.html (accessed on 28 August 2024).
Wrage, N.; Velthof, G.L.; van Beusichem, M.L. Role of nitrifier denitrification in the production of nitrous oxide. Soil Biol. Biochem. 2001, 33, 1723–1732. [Google Scholar] [CrossRef]
Shcherbak, L.; Millar, N.; Robertson, G.P. Global metaanalysis of the nonlinear response of soil nitrous oxide (N₂O) emissions to fertilizer nitrogen. Proc. Natl. Acad. Sci. USA 2014, 111, 9199–9204. [Google Scholar] [CrossRef] [PubMed]
Philippot, L.; Hallin, S.; Schloter, M. Ecology of denitrifying prokaryotes in agricultural soil. Adv. Agron. 2007, 96, 249–305. [Google Scholar]
Hu, H.; Chen, D.; He, J. Microbial regulation of terrestrial nitrous oxide formation: Understanding the biological pathways for prediction of emission rates. FEMS Microbiol. Rev. 2015, 39, 729–749. [Google Scholar] [CrossRef]
Li, X.; Wang, R.; Du, Y.; Han, H.; Guo, S.; Song, X.; Ju, X. Significant increases in nitrous oxide emissions under simulated extreme rainfall events and straw amendments from agricultural soil. Soil Tillage Res. 2025, 246, 106361. [Google Scholar] [CrossRef]
Zhang, X.; Wang, J.; Zhang, T.; Li, B.; Yan, L. Assessment of nitrous oxide emissions from Chinese agricultural systemand low-carbon measures. Jiangsu J. Agric. Sci. 2021, 37, 1215–1223. [Google Scholar]
Mao, G.; Ma, W.; Kang, J. Estimation of N₂O Emissions from Agricultural Land in Beijing- Based on the Regional Nitrogen Cycle IAP-N Model. Jiangsu Agric. Sci. 2018, 46, 280–284. [Google Scholar]
Shang, J.; Yang, G.; Yu, F. Calculation and influencing factors of greenhouse gas emissions in Chinese agriculture. Chin. J. Ecol. Agric. 2015, 23, 354–364. [Google Scholar]
Wei, L.; Lin, N.; Mo, Z. Inventory and Characteristics Analysis of N₂O Emissions from Agricultural Sources in Chinese Provinces. Zhejiang Agric. J. 2019, 31, 1909–1917. [Google Scholar]
Zhang, Q.; Ju, X.; Zhang, F. Re estimation of N₂O emissions from Chinese farmland using the modified IPCC 2006 method. Chin. J. Ecol. Agric. 2010, 18, 7–13. [Google Scholar] [CrossRef]
Ying, N. Direct Emissions, Spatial Distribution, and Changing Trends of N₂O from Farmland in China. Master’s Thesis, Anhui Normal University, Wuhu, China, 2014. [Google Scholar]
Wang, M.; Zhang, Z.; Lv, C. Study on CH₄ and N₂O Emissions and Greenhouse Effect in Cold Field Rice Fields under Different Irrigation Modes. Soil Water Conserv. Res. 2016, 23, 95–100. [Google Scholar]
Liang, W.; Zhang, Y.; Yue, J. Effects of Long acting Nitrogen Fertilizer Application on CH₄ and N₂O Emissions from Black Soil Water and Drought Fields. J. Ecol. 2004, 3, 44–48. [Google Scholar]
Liu, T.; Li, S.; Guo, L. Advantages of nitrogen fertilizer deep placement in greenhouse gas emissions and net ecosystem economic benefits from no-tillage paddy fields. J. Clean. Prod. 2020, 263, 121322. [Google Scholar] [CrossRef]
Zhang, X.; Qin, Y.; Wu, L. Research progress on agricultural greenhouse gas emissions. J. Henan Univ. (Nat. Sci. Ed.) 2019, 49, 649–662. [Google Scholar]
Cayuela, M.L.; Oenema, O.; Kuikman, P.J. Bioenergyby-products as soil amendments?Implications for carbon sequestra-tion and green-house gas emissions. GCB Bioenergy 2010, 2, 201–213. [Google Scholar] [CrossRef]
Hogan, K.B. Aruthropogenic Methane Emissions in the United States: Estimate for 1990; United States Environmental Protection Agency: Washington, DC, USA, 1993.
Zhou, J.; Ma, Y.; Yang, S. Study on the influencing factors and emission reduction of greenhouse gases in animal husbandry. Agric. Environ. Dev. 2013, 30, 78–82. [Google Scholar]
Liu, C.; Wu, Y.; Zhang, W. Study on the Benefits of Implementing Integrated Planting and Breeding for Emission Reduction in China. Environ. Pollut. Prev. 2016, 38, 87–89. [Google Scholar]
Clough, T.J.; Cardenas, L.M.; Friedl, J.; Wolf, B. Nitrous oxide emissions from ruminant urine: Science and mitigation for intensively managed perennial pastures. Curr. Opin. Environ. Sustain. 2020, 47, 21–27. [Google Scholar] [CrossRef]

Figure 1. Changes in the number of farmed animals: (a) for non-dairy cows (×10³), (b) for poultry (×10⁵), (c) for sheep (×10³), and (d) for pigs (×10⁵).

Figure 3. Historical changes in nitrous oxide emissions from agricultural activities in Anhui Province.

Figure 4. Annual emissions of nitrous oxide from agricultural land in Anhui Province.

Figure 5. Annual emissions of nitrous oxide from animal fecal management.

Figure 6. Statistical chart of nitrous oxide emissions from agricultural land at some prefecture-level cities in Anhui Province (a) and nitrous oxide emissions from livestock and poultry manure management (b).

Figure 7. Contribution of animal manure management (a) and agricultural land (b) to nitrous oxide emissions in some prefecture-level cities of Anhui Province in 2014 and 2022.

Table 1. Nitrogen excretion by different animals (kg/head/year) [15].

Wildlife	Non-Dairy Cows	Milk Cows	Poultry	Goats	Hogs	Others
Nitrogen excretion	40	60	0.6	12	16	40

Table 2. Nitrous oxide emission factors for manure management (kg/head/year) [15].

Prefecture or County (Area Administered by a Prefecture-Level City or County-Level City)	Non-Dairy Cows	Ovine	Goats	Hogs	Poultry
Eastern China	0.846	0.113	0.113	0.175	0.007

Table 3. Nitrous oxide emissions from agricultural land in Anhui Province, 2013–2022.

Particular Year	Direct Emissions/10,000 t			Indirect Emissions/10,000 t		Emissions from Agricultural Land/10,000 t
Particular Year	Fertilizer Nitrogen	Manure Nitrogen	Straw Nitrogen	Atmospheric Deposition	Runoff	Emissions from Agricultural Land/10,000 t
2013	1.50	0.48	0.16	0.33	0.29	2.76
2014	1.48	0.47	0.16	0.33	0.29	2.73
2015	1.44	0.46	0.17	0.32	0.29	2.68
2016	1.40	0.44	0.16	0.31	0.28	2.59
2017	1.35	0.42	0.16	0.30	0.27	2.50
2018	1.30	0.42	0.16	0.29	0.26	2.43
2019	1.22	0.41	0.16	0.28	0.25	2.31
2020	1.17	0.46	0.16	0.30	0.25	2.33
2021	1.13	0.48	0.16	0.30	0.24	2.31
2022	1.07	0.50	0.16	0.30	0.24	2.26

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Ye, Z.; Sun, Y.; Zhang, X.; Yao, Y. Estimation of Nitrous Oxide Emissions from Agricultural Sources and Characterization of Spatial and Temporal Changes in Anhui Province (China). Atmosphere 2024, 15, 1538. https://doi.org/10.3390/atmos15121538

AMA Style

Ye Z, Sun Y, Zhang X, Yao Y. Estimation of Nitrous Oxide Emissions from Agricultural Sources and Characterization of Spatial and Temporal Changes in Anhui Province (China). Atmosphere. 2024; 15(12):1538. https://doi.org/10.3390/atmos15121538

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Ye, Zhou, Yujuan Sun, Xianglin Zhang, and Youzhi Yao. 2024. "Estimation of Nitrous Oxide Emissions from Agricultural Sources and Characterization of Spatial and Temporal Changes in Anhui Province (China)" Atmosphere 15, no. 12: 1538. https://doi.org/10.3390/atmos15121538

APA Style

Ye, Z., Sun, Y., Zhang, X., & Yao, Y. (2024). Estimation of Nitrous Oxide Emissions from Agricultural Sources and Characterization of Spatial and Temporal Changes in Anhui Province (China). Atmosphere, 15(12), 1538. https://doi.org/10.3390/atmos15121538

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