https://orcid.org/0000-0003-3566-8564
Figures
Abstract
Nitrous oxide (N2O) and ammonia (NH3) volatilization (AV) are the major pathways of nitrogen (N) loss in soil, and recently, N2O and NH3 mitigation has become urgently needed in agricultural systems worldwide. However, the influence of straw incorporation (SI) and biochar addition (BC) on N2O and NH3 emissions are still unclear. To fill this knowledge gap, a soil column experiment was conducted with two management strategies using straw ‐ straw incorporation (S1) and straw removal (S0) ‐ and four biochar application rates (0 (C0), 15 (C1), 30 (C2), and 45 t ha−1 (C3)) to evaluate the impacts of their interactions on N2O and NH3 emissions. The results showed that NO3−−N concentration and pH was the major contributors to affect the N2O and NH3 losses. Without biochar addition, N2O emissions was decreased by 59.6% (P<0.05) but AV was increased by 97.3% (P<0.05) under SI when compared to SR. Biochar was beneficial for N2O mitigation when straw was removed, but increased N2O emission by 39.4%−83.8% when straw was incorporated. Additionally, biochar stimulated AV by 27.9%−60.4% under S0 and 78.6%−170.3% under S1. Consequently, SI was found to significantly interact with BC in terms of affecting N2O (P<0.001) and NH3 (P<0.001) emissions; co-application of SI and BC promoted N2O emissions and offset the mitigation potential by SI or BC alone. The indirect N2O emissions caused by AV, however, might offset the reduction of direct N2O caused by SI or BC, thus leading to an increase in overall N2O emission. This paper recommended that SI combined BC at the amount of 8.2 t ha−1 for maintaining a lower overall N2O emission for future agriculture practices, but the long-term impacts of straw incorporation and biochar addition on the trade-off between N2O and NH3 emissions and reactive N losses should be further examined and assessed.
Citation: Zhang A, Zhang X, Liang Q, Sun M (2024) Co-application of straw incorporation and biochar addition stimulated soil N2O and NH3 productions. PLoS ONE 19(2): e0289300. https://doi.org/10.1371/journal.pone.0289300
Editor: Sudeshna Bhattacharjya, ICAR-Indian Institute of Soil Science, INDIA
Received: December 21, 2022; Accepted: July 17, 2023; Published: February 2, 2024
Copyright: © 2024 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: The source of funding that contributed to our study was the Technology Project of Hebei Education Department [KY202012], which was the only funder to support the study design, data collection and analysis, and preparation and language editing of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Globally, fertilized cropland are the major source of nitrogen pollutants, such as ammonia (NH3) and nitrous oxide (N2O) [1]. N2O has 273 times greater global warming potential than carbon dioxide when assessed over a 100−year time scale, and also accelerates ozone depletion [2]. Intensively used agricultural soil have been identified to be the main source of N2O emission, accounting for 60% of total anthropogenic-caused release at approximately 3.5 Mt N2O−N per year [3].
NH3 volatilization (AV) following nitrogen (N) fertilizer application is a major pathway of soil N loss from cropping systems worldwide [4]. It has been estimated that agriculture contributes 80%−90% of the total NH3 emitted in many countries, and globally, NH3 emissions increased by 128% over the last four decades [5]. Additionally, indirect greenhouse gas (GHG) emissions induced by NH3 losses have been found to be up to 5%−12% [6]. Recently tackling the trade-off between N2O and NH3 emissions has been a hot-spot [7], and agricultural soil is increasingly being scrutinized for its contribution to air quality degradation [8]. Moreover, many studies have focused on how to mitigate N2O and NH3 losses to meet the goal of increasing nitrogen use efficiency, decreasing environmental risks for future intensive agriculture.
Northern China, the most important and intensified crop production region in the country, is an area of annual winter wheat (Triticum aestivum L.)/summer maize (Zea mays L.) rotation systems. Unfortunately, intensive agricultural systems are still inefficient in N fertilizer use; around 50%–70% of fertilizer N is lost to the environment [9]. Another striking feature of intensive agriculture is a large amount of crop straw production. In China, straw production exceeds more than 109 Mg per year, accounting for 25% of global production [10]. Crop straw incorporated in the field improves soil fertility and reduces the severe air pollution caused by burning of straw [11], minimizes negative environmental impacts [12], increases soil C sequestration [13–15] and enhances cereal crop yields [16], which has been widely recommended as an environmentally friendly strategy in agricultural ecosystem [15]. Additionally, straw incorporation has been shown to induce net N immobilization, along with reducing NO3− leaching and N2O and NH3 emissions [17]. However, the results of previous studies that assessed the influence of straw incorporation on N2O emissions were found to be inconsistent, showing positive, negative, and neutral effects. For example, Liu et al. [15] reported that N2O emission was increased by 8.3% in upland soils but decreased by 15.2% in paddy soils when straw was incorporated, mainly because of a mineralizable-N substrate for N2O generation through nitrification process and reduced oxygen availability in the soil profile which favored N2O production through denitrification [18–20]. Moreover, previous studies have shown that straw incorporation significantly increased soil NH4+−N concentration and induced 45.7% more AV [21]. This is because when straw was incorporated, the ratio of soil N immobilization was lower than that of N mineralization [21, 22].
Straw can be further derived to yield a highly stable biomass-pyrolysis product known as biochar. As a new approach to returning agricultural waste to the field, straw-derived biochar application can affect both N2O and NH3 losses through increasing soil carbon sequestration and reducing carbon mineralization and non−CO2 emissions from the biochar itself [23]. Biochar was beneficial to change the N2O emission and NH3 volatilization, reduce soil organic matter mineralization [24], and improve root biomass, yield, water use efficiency, and soil microbial activities [25]. Previous studies have shown that biochar could reduce current anthropogenic CO2−eq emissions by 12% without endangering food security [26]. Biochar addition can change soil physical and chemical properties, such as increasing the soil carbon content, C/N ratio, pH, soil water holding capacity, and reducing NH4+−N and NO3−−N leaching [27], thus affecting the N2O emissions and AV from agricultural soil. For example, Feng et al. [28] have found that soil N2O emission was increased by 7.7%−21.2%, but Yang et al. [29] reported that soil N2O emission was decreased by 46.6% under biochar addition. Feng et al. [28] reported that biochar treatments recorded 9.9%−70.9% higher AV compared with control mainly due to the increase of soil pH after biochar addition. Sun et al. [30] has found that biochar addition significantly decreased N leaching by 11.6%−29.7%, but not significantly affected AV when 0.5% and 1% biochar amended and increased by 25.6%−53.6% higher AV when 2% and 4% biochar amended. Therefore, the conclusions about the effect of biochar addition on AV were inconsistent, however, and mainly depend on the extent of soil pH change, the ammonium retention capacity, and addition rate of biochar [31].
This study aimed to assess if straw incorporation combined with biochar application could be an efficient measure to reduce N2O and NH3 losses. An indoor soil column experiment was conducted to investigate the comprehensive influences of biochar (derived from maize straw) addition and maize straw incorporation on soil N2O and NH3 losses. The objectives of this study were to determine the response of N2O and NH3 losses to SI and BC, to explore the trade-off between N2O and NH3 emissions under SI and BC, and to establish the soil conditions to identify measures for simultaneous reduction of N2O and NH3 losses.
Materials and methods
Background information and soil column installation
A soil column experiment was conducted from April to May 2021 at the State Key Laboratory of North China Crop Improvement and Regulation, Hebei Agricultural University, China. PVC pots were used (20 cm diameter × 60 cm height). Each column was equipped with a static chamber on the top for gas samples collection (Fig 1A). The experimental soil was collected from 0−10 cm, 10−20 cm, and 20−40 cm of depth from the soil profile in a wheat-maize rotation field located in Sanfenchang field station, Hebei Province, China (38° 51′ 30ʺN, 115° 28′ 52ʺE). The soil samples were air-dried and passed through a 2−mm sieve, then repacked to soil columns in the same order and at the same bulk density. The soil properties of surface layer (0−20 cm) were shown in Table 1.
(a) Design drawing of pot experiment, (b) schedule of fertilization and irrigation managements and air temperature, and (c) photograph of the indoor experiment. SI: straw incorporation; S0: straw removal; BC: biochar addition; B0: without biochar.
Experimental treatments and managements
In this study, the two factors considered were straw and biochar managements. Biochar was derived from maize straw in a continuous slow pyrolysis system at 550°C. The properties of the biochar used in this experiment were shown in Table 1. Two straw management strategies-straw incorporation (S1) and straw removal (S0), and four biochar addition rates (0 [C0], 15 [C1], 30 [C2], and 45 t ha−1 [C3]) were conducted. The experimental design included eight treatments: S0C0, S0C1, S0C2, S0C3, S1C0, S1C1, S0C2, and S1C3, arranged in three replicates each into 24 soil columns total. The straw, biochar, and basal fertilizer were homogeneously mixed with the surface soils (0−20 cm).
The wheat was transplanted on April 7, 2021 with a basal fertilizer of 50% total N (i.e., 105 kg N ha−1), 90 kg P2O5 ha−1, and 120 kg K2O ha−1. The topdressing fertilizer was applied on May 4, 2021. During the wheat-growing season, all experimental columns were irrigated at the amount of 75 mm in three times (Fig 1).
Measurements of N2O and NH3
N2O gas samples were collected through a closed chamber method, and were analyzed using a gas chromatograph (Agilent 7820A, Agilent Technologies Inc., US) equipped with an electron capture detector using the DN−CO2 method. For the five gas samples analyzed, N2O flux was calculated by a linear method using Eq 1 as follows:
(1)
where F = N2O flux, μg N m−2 h−1; M = gas molar mass, g·mol−1; V0 = gas volume in the standard state, 22.41×10−3 m3; T = temperature on the sampling day,°C; P = air pressure on the sampling day, hPa; P0 = air pressure on the standard day, 1013 hPa; H = height, cm; and dCt/dt, the linear or non-linear slope of the N2O concentration change over time in the static chamber.
Daily NH3 volatilization fluxes were measured by a continuous airflow enclosure method using a Plexiglas chamber (20 cm inner diameter and 20 cm height). NH3 emitted from soil was absorbed by dilute H2SO4 (0.01 M) solution. The NH4+−N concentration of the resulting solutions was then determined by a continuous flow analyzer (TRAACS2000, Norderstedt, Germany), and the NH3 volatilization fluxes were calculated according to Eq (2):
(2)
where F = NH3 flux, mg NH3−N m−2 h−1; C = concentration of the NH3−N absorbed in the H2SO4 solution, mg NH3−N mL−1; V = volume of the dilute H2SO4 solution, mL; A = cross-sectional area of the capture device, m2; and t = successive capture time, h.
The cumulative N2O emission and NH3 volatilization were estimated by summing the daily mean fluxes, and the daily fluxes of non-measurement days were estimated by interpolating linearly between sampling dates.
The overall N2O emission was defined as direct N2O plus indirect N2O from NH3 volatilization, in which the indirect N2O emission factor from NH3 was defined as 1% according to Wu, et al. [7].
Auxiliary measurements
The amount of irrigation water applied was manually recorded at each occurrence. During N2O and NH3 sampling, the air temperature, soil temperature (0−5 cm) and soil water content in each treatment were simultaneously observed and recorded. Gravimetric water content was measured by drying the soil at 105°C for 24 h. Water-filled pore space (WFPS) was calculated according to the Eq (3)
(3)
where 2.65 = theoretical particle density of the soil, g cm−3.
At experimental completion, soil samples were taken at 0−10, 10−20 and 20−40 cm soil depth and then separated into two portions. One portion was used for soil moisture, NO3−−N, and NH4+−N measurement. The soil samples were extracted with 1 M KCl solution (soil: solution = 1: 5), then the extracts were analyzed using a continuous flow analyzer (TRAACS2000, Bran and Luebbe, Norderstedt, Germany) to determine soil NH4+ and NO3− concentration. The second portion was used for soil organic matter (SOM, digestion with H2SO4−K2Cr2O7 and titration), total N (TN, H2SO4-mixed accelerator-distillation using the Kjeldahl method), and pH determination.
Calculations and data analysis
All data collected were analyzed using one-way analysis of variance (ANOVA) in SPSS Statistics 22.0 (SPSS Inc., Beijing, China). Means of AV monitored by different methods were compared followed the least significant difference (LSD) test at the 5% level of probability. The effects of different straw and biochar managements and their interactions on soil N2O and NH3 losses, soil conditions under different soil layers were analyzed by the two-way ANOVA. Graphs were produced with Origin 9.1. The RDA was estimated by Canoco 5 (version 5.02) software.
Results
N2O fluxes and cumulative emissions
The fertilization and irrigation stimulated substantial N2O emissions (Figs 2A and 2C and S1). When straw was incorporated, the highest N2O flux was found under C2 treatment (265.2 μg N m−2 h−1) at the top-dressing (Fig 2A). Biochar significantly increased the soil N2O flux peaks, especially in the first four days after fertilization, thus significantly increased N2O emissions (Fig 3). The cumulated N2O emissions were in the order of C3>C1>C2>C0, in which the N2O emission of C3, C1, and C2 were 83.8% (0.66 kg N ha−1, P<0.05), 56.9% (P<0.05), and 39.4% (P<0.05) higher than that of C0, respectively. When straw was removed, the highest N2O flux was found under C0 treatment (794.0 μg N m−2 h−1) at the top-dressing (Fig 2C). In this condition, biochar application significantly decreased soil N2O flux peaks and contributed to N2O mitigation by 35.0%−54.7% under straw removal (SR). Additionally, N2O emission under S1C0 was 59.6% lower than that of S0C0 (0.89 kg N ha−1).
The emission fluxes of N2O and NH3 under conditions of either straw incorporation (a, b) and straw removal (c, d) with different addition amounts of biochar. Error bars denote standard errors. C0: without biochar; C1: biochar applied at 15 t ha−1; C2: biochar applied at 30 t ha−1; C3: biochar applied at 45 t ha−1.
Error bars denote standard errors. * P<0.05. Definitions of C0, C1, C2, and C3 are given in caption of Fig 2.
NH3 fluxes and cumulative emissions
Daily NH3 fluxes exhibited apparent temporal patterns, and the flux peaks were occurring on the first 1−7 days after fertilization. Additionally, the NH3 volatilization (AV) was stimulated by SI and BC (Fig 2 and S2 Fig). The highest NH3 flux peaks were all observed in the C2 treatment after two fertilizations under SI and SR; the highest NH3 flux peak was found under C2 (Fig 2B and 2D). AV under BC treatment was 78.6% (C1, P<0.05), 170.3% (C2, P<0.05), and 92.1% (C3, P<0.05) higher than that of C0 (24.2 kg N ha−1), respectively. When straw was removed, AV under BC treatment was 32.9% (C1, P<0.05), 60.4% (C2, P<0.05), and 27.9% (C3, P<0.05) higher than that of C0 (12.3 kg N ha−1), respectively. In addition, AV was further stimulated by 165.1%−232.4% with biochar application under SI when compared with SR (Fig 3).
Soil temperature, WFPS and chemical parameters
Under the same straw practice, no significant difference among these four biochar treatments was found (Figs 4 and 5). The WFPS of S1C0 was 20.5% (P<0.05) lower that of S0C0 (Fig 5).
Error bars denote standard errors. Definitions of C0, C1, C2, and C3 are given in caption of Fig 2.
Error bars denote standard errors. Definitions of C0, C1, C2, and C3 are given in caption of Fig 2.
Soil NO3−−N, NH4+−N, total N, and SOM varied in different soil layers under different treatments (Fig 6). In surface soil (0−10 cm), SI and BC were both beneficial for the increase of soil NO3−−N concentration. However, the highest soil NO3−−N concentration was found in C1, and gradually decreased along with the increase of biochar addition amount under SR. In the 10−40 cm soil layer, soil NO3−−N was only influenced by the addition amount of biochar.
Error bars denote standard errors. The different letters in the same soil layer indicate a significant difference (P<0.05) with Turkey’s multiple range test of different amounts of biochar addition either under straw incorporation or not. Definitions of C0, C1, C2 and C3 are given in caption of Fig 2.
SI only contributed to the increase of NH4+−N concentration in surface soil (0−10 cm). In the 20−40 cm soil layer, soil NH4+−N concentration under SR was increased by 81.1% (P<0.05) in comparison to SI. BC highly affected the influence of soil TN concentration under SI; for instance, in the 0−10 cm layer, TN was increased by 40.4% (P<0.05) under SI as compared to SR under C3 (45 kg C ha−1). Additionally, biochar addition further contributed to the increase of SOM especially in the 0−10 cm and 20−40 cm soil layers.
Effect of straw incorporation and biochar on soil N2O, NH3, and other chemical parameters
Soil NO3−−N concentration and pH were the main contributor (accounting for 51.2%, 14.3%, respectively) to affect soil N2O emission and NH3 volatilization (Fig 7). SI significantly interacted with biochar addition in terms of affecting N2O and NH3 emissions, soil pH and NO3− in 0−10 cm soil layer, and SOM in 20−40 cm soil layer (Table 2). Under SI, biochar application particularly stimulated N2O and NH3 losses (Fig 8). The soil moisture and SOM significantly increased (P<0.05) along with the increase of biochar addition amount in 0−40 cm soil layer. The positive influence of biochar on NO3−−N and NH4+−N content, however, was only found in 0−20 cm layer. The high N2O emission caused by biochar addition was mainly due to its negative influence on soil pH and the increase in soil moisture and SOM, which was particularly noticeable in the 0−10 cm soil layer. In addition, SI contributed to SOM increase (P<0.05) in surface soil, leading to high NH3 volatilization (P<0.05).
(a) Redundancy analysis of the influence and the contribution (b) of soil properties on N2O and NH3 losses.
Each bubble with * indicates a significant correlation at P<0.05.
Biochar was beneficial to increase soil moisture (P<0.05) (particularly in the 0−20 cm soil layer) as well as N2O mitigation (P<0.05) under SR condition. No significant relationships were found between NH3 emission and the measured variables.
Discussions
Response of N2O emissions to straw incorporation and biochar addition
Soil N2O production is stimulated by native soil N (background), fertilizer N, and the priming effect [32]; the influence of field management strategies on soil N2O emissions is mainly due to the impacts of fertilizer N and the priming effect [33]. In previous studies, SI was found to be beneficial to increase the concentration of SOC and total N, and C/N ratio through available N release or soil N immobilization processes [19]. In this study, a 59.6% reduction in N2O emissions was found under SI without biochar addition (Fig 3). Additionally, C/N ratio, SOM and NO3– concentration was positively correlated to soil N2O emission, and the soil NO3– concentration was the major contributor (accounting for 51.2%) to soil N2O and NH3 losses, and the pH was the next one through a redundancy analysis (Fig 7). Eventhough, no significant influence of SI on SOM was found, our previous study have demonstrated that SI has a positive impact on C sequestration [34]. Therefore, SI is regarded as an important way to affect soil N2O emission [35]. Straw managements showed a significant effect on SOM and soil NO3– concentration in 0−10 cm soil layer (Table 1). Some studies have found that N2O emission was positively correlated with soil NO3– and SOM concentration [35, 36]. However, no similar results were observed in our study, which indicated that changes in available N might not be the main factor affecting soil N2O productions. As previous studies reported that transient subsequent microbial N immobilization might have occurred with straw-C inputs [23, 37]. Chen et al. [36] has found that maize straw incorporated into soil would decrease seasonal N2O emissions by decreasing the contribution of denitrification to N2O emissions and through decreasing the abundance of N functional genes, thus caused the higher of soil NO3– concentration under SI than SR.
Biochar derived by maize straw was also expected to have potential to improve soil nutrient retention. Some previous studies have also observed significant reductions in soil N2O emissions after biochar addition, potentially because of the increase of soil organic C contcentration and C/N ratio and adsorption of NH4+−N by biochar [30]. A high soil C/N ratio promoted soil N assimilation and immobilization, and resulted in the consumption of by nitrifiers and denitrifiers [24]. Additionally, in northern China, a reduction in N2O emissions was also found due to the reduction process by nitrifier denitrification (by 74%) and heterotrophic denitrification (by 58%) [24] with the increase in nosZ gene prevalence following biochar application [31]. In this study, compared with S0C0, adding biochar significantly reduced N2O production from the soil (approximate decrease of 35.0%−54.7%), showing a binomial relationship (S3 Fig).
Unfortunately, no coordinated mitigation potential for N2O emissions was found for co-application of straw and biochar, but promoted by 39.4%−83.8% (P<0.05) as comparison to S1C0 (Figs 3 and S1). In this study, the significant influence of SI, biochar addition, and their interactions were found on N2O emissions (Table 1). These results might be explained that straw decomposition was accelerated and thus increased the contcentration of surface soil organic matter when straw was incorporated and biochar was applied [24, 38]. The co-application of straw and biochar also likely significantly promoted the positive priming effect on soil organic N mineralization, increasing NH4+−N concentrations in the 10−20 cm soil layer [39]. The treatment also increased the soil NO3−−N concentration in the 0−10 cm soil layer by promoting nitrification, ultimately resulted in the increase of soil N2O emissions [24].
NH3 emissions response to straw incorporation and biochar amendment
In this study, NH3 volatilization was increased by 97.3% under SI, and significant correlated to SOM, TN, and NH4+ concentrations (Figs 3 and 7). Incorporation of maize straw with high C/N ratio could stimulate soil microbial activity, as previously discussed, enhancing straw decomposition and urea hydrolysis [21, 22]; this likely increased the NO3− concentrations in the 0−10 cm soil layer (Table 1), indicating that nitrification was promoted and contributed to NH3 reduction. Higher concentration of SOM and TN, and pH were found under SI (Fig 8). Consequently, the increased potential for NH3 volatilization through the hydrolysis of urea may have offset its reduction potential through the nitrification process, causing the observed increase of AV[40].
A significant correlation was found between the amount of biochar addition and pH/NH4+ in the 0−10 cm soil layer (Table 1). Additionally, biochar would increase AV by 27.9%−60.4% under SR, and a a binomial relationship was found between the amount biochar addition and AV (S4 Fig), which was in line with Sun et al. [30] and Feng et al. [28]. Through a redundancy analysis, we found pH was a main contributor (accounting for 14.3%) to NH3 emission (Fig 7). As Liu et al. [6] reported that the increase of AV induced by biochar might be caused by the strong increase of soil pH, thus promoted the hydrolysis of urea and inhibited the nitrification processes (especially in the 10−40 cm soil layer), thus increased soil NH4+ concentration [41].
AV decreased gradually with the increase of the amount of biochar addition; this was mainly due to the high NH4+/NH3 absorption/immobilization by biochar offsetting the NH4+ hydrolyses from urea [42]. When the co-application of straw and biochar, the AV increased by 78.6%−170.3% (P<0.01) (Fig 3 and Table 1). Previous studies have shown that biochar was beneficial for straw decomposition and SOM mineralization, then increasing NH4+ concentrations [24, 38] and resulting in a positive effect on AV (S4 Fig).
Tackling the trade-offs between NH3 and N2O emission using straw incorporation and biochar addition
Recently, approaches to tackle the possible trade-off between N2O and NH3 emissions in croplands have been studied [40, 41]. In fertilized fields, many factors have inconsistent impacts on NH3 volatilization and N2O emission [3], implying that a trade-off is required in decisions surrounding practical management of straw incorporation and biochar addition. As evidenced by Fig 3, lower N2O emissions (straw effects vs. biochar effects: 59.6% vs. 97.3%) and higher NH3 volatilization (straw effects vs. biochar effects: 35.0%−54.7% vs. 27.9%−60.4%) were achieved under SI or biochar addition, indicating that either the single- or co-application of these compounds was unable to achieve the win-win goal of both N2O and NH3 mitigation [24].
Additionally, the indirect and direct N2O emissions were accounted for 13.8%−49.0% and 67.6%−131.1% of overall N2O emission under S0 and S1 treatment, respectively (S5 Fig). For the overall N2O emission, both negative (for biochar amount lower than 8.2 kg ha−1) and positive effects were observed under SI (Fig 9). Therefore, using SI or biochar addition could lead to high NH3 volatilization when urea was applied, and stimulated the indirect N2O emissions that offset the mitigation potential of direct N2O reduction [40, 41]. Because of this, when biochar is applied in cropland, the influence of straw managements on soil N2O and NH3 emissions should be further assessed for future sustainable agriculture. Additionally, when straw was incorporated, biochar applied at the amounts of 8.2 kg ha−1 are recommended based on this study for overall N2O mitigation, though further work remains to achieve better reduction.
Error bars denote standard errors.
Conclusions
Fertilized cropland is a major source of ammonia (NH3) and nitrous oxide (N2O) losses. This study demonstrated that NO3−−N concentration and pH was the major contributors to affect the N2O and NH3 losses. Single straw incorporation (SI) or biochar addition could mitigate N2O emission, but co-application contributed to the increases of N2O emission. Eventhough, the single- or co-application of SI and biochar both induced NH3 volatilization (AV). The effects of SI and biochar on N2O and NH3 emissions could be partly ascribed to the straw decomposition, urea hydrolysis, and nitrification. Additionally, the indirect N2O emission induced by AV offset the mitigation potential for direct N2O emissions when straw incorporated or biochar applied. Overall, the co-application of SI with BC at the amount of 8.2 t ha−1 is recommended to successfully maintain a lower overall N2O emission to tackle the trade-off between N2O and NH3 emissions. For future agriculture, the long-term impacts of straw incorporation and biochar addition on the trade-off between N2O and NH3 emissions and reactive N losses should be further examined and assessed.
Supporting information
S1 Fig.
The distribution of N2O fluxes under (a) straw incorporation and (b) straw removal. Error bars denote standard errors. C0: without biochar; C1: biochar applied with 15 t ha−1; C2: biochar applied with 30 t ha−1; C3: biochar applied with 45 t ha−1.
https://doi.org/10.1371/journal.pone.0289300.s001
(DOCX)
S2 Fig.
The distribution of NH3 fluxes under (a) straw incorporation and (b) straw removal. Error bars denote standard errors. Definitions of C0, C1, C2 and C3 are given in caption of S1 Fig.
https://doi.org/10.1371/journal.pone.0289300.s002
(DOCX)
S3 Fig. The relationship between N2O accumulation and biochar addition under straw incorporation (S1) and removal (S0).
Error bars denote standard errors.
https://doi.org/10.1371/journal.pone.0289300.s003
(DOCX)
S4 Fig. The relationship between NH3 accumulation and biochar addition under straw incorporation (S1) and removal (S0).
Error bars denote standard errors.
https://doi.org/10.1371/journal.pone.0289300.s004
(DOCX)
S5 Fig. Soil N2O emissions from direct and indirect induced from NH3 under different treatments.
Error bars denote standard errors. Definitions of C0, C1, C2 and C3 are given in caption of S1 Fig.
https://doi.org/10.1371/journal.pone.0289300.s005
(DOCX)
Acknowledgments
We deeply appreciate the anonymous reviewers for their helpful advice and comments that improved this manuscript.
References
- 1. Fan C, Li B, Xiong Z. Nitrification inhibitors mitigated reactive gaseous nitrogen intensity in intensive vegetable soils from China. Sci Total Environ. 2018;612:480–9. Epub 2017/09/03. pmid:28865265.
- 2. Bahram M, Espenberg M, Parn J, Lehtovirta-Morley L, Anslan S, Kasak K, et al. Structure and function of the soil microbiome underlying N2O emissions from global wetlands. Nat Commun. 2022;13(1):1430. Epub 2022/03/19. pmid:35301304; PubMed Central PMCID: PMC8931052.
- 3. Zhang C, Song X, Zhang Y, Wang D, Rees RM, Ju X. Using nitrification inhibitors and deep placement to tackle the trade-offs between NH3 and N2O emissions in global croplands. Glob Chang Biol. 2022. Epub 2022/04/17. pmid:35429205.
- 4. Pan B, Lam SK, Mosier A, Luo Y, Chen D. Ammonia volatilization from synthetic fertilizers and its mitigation strategies: A global synthesis. Agriculture Ecosystems & Environment. 2016;232:283–9.
- 5. Liu L, Xu W, Lu X, Zhong B, Guo Y, Lu X, et al. Exploring global changes in agricultural ammonia emissions and their contribution to nitrogen deposition since 1980. Proc Natl Acad Sci U S A. 2022;119(14):e2121998119. Epub 2022/03/29. pmid:35344440.
- 6. Liu M, Liu C, Liao W, Xie J, Zhang X, Gao Z. Impact of biochar application on gas emissions from liquid pig manure storage. Sci Total Environ. 2021;771:145454. Epub 2021/03/20. pmid:33736144.
- 7. Wu D, Zhang Y, Dong G, Du Z, Wu W, Chadwick D, et al. The importance of ammonia volatilization in estimating the efficacy of nitrification inhibitors to reduce N2O emissions: A global meta-analysis. Environ Pollut. 2021;271:116365. Epub 2021/01/04. pmid:33388681.
- 8. Chapman KE, Torbert HA, Watts DB. Validation of a new method for quantification of ammonia volatilization from agricultural field plots. Eur Agro J, 2016; 3(3), 76–90. https://doi.org/10.17830/j.eaj.2016.03.078.
- 9. Ju X, Xing G, Chen X, Zhang S, Zhang L, Liu X, et al. Reducing environmental risk by improving N management in intensive Chinese agricultural systems. Proc Natl Acad Sci U S A. 2009;106(9):3041–6. pmid:19223587
- 10. Ji L. An assessment of agricultural residue resources for liquid biofuel production in China. Renew Sust Energ Rev. 2015;44:561–75.
- 11. Wu X, Wang W, Xie K, Yin C, Hou H, Xie X. Combined effects of straw and water management on CH4 emissions from rice fields. J Environ Manage. 2019;231:1257–62. Epub 2019/01/04. pmid:30602250.
- 12. Li N, Wen S, Wei S, Li H, Feng Y, Ren G, et al. Straw incorporation plus biochar addition improved the soil quality index focused on enhancing crop yield and alleviating global warming potential. Environ Technol Inno. 2021;21.
- 13. Chen H, Hou R, Gong Y, Li H, Fan M, Kuzyakov Y. Effects of 11 years of conservation tillage on soil organic matter fractions in wheat monoculture in Loess Plateau of China. Soil Till Res. 2009;106(1):85–94.
- 14. Guan XK, Wei L, Turner NC, Ma SC, Yang MD, Wang TC. Improved straw management practices promote in situ straw decomposition and nutrient release, and increase crop production. J Clean Prod. 2020;250.
- 15. Liu C, Lu M, Cui J, Li B, Fang C. Effects of straw carbon input on carbon dynamics in agricultural soils: a meta-analysis. Glob Chang Biol. 2014;20(5):1366–81. Epub 2014/01/08. pmid:24395454.
- 16. Zhao H, Sun B, Lu F, Zhang G, Wang X, Ouyang Z. Straw Incorporation strategy on cereal crop yield in China. Crop Sci. 2015;55(4):1773–81.
- 17. Rizhiya EY, Boitsova LV, Buchkina NP, Panova GG. The influence of crop residues with different C: N ratios on the N2O emission from a loamy sand soddy-podzolic soil. Eurasian Soil Sci. 2011;44(10):1144–51.
- 18. Zhao Y, Lv H, Qasim W, Wan L, Wang Y, Lian X, et al. Drip fertigation with straw incorporation significantly reduces N2O emission and N leaching while maintaining high vegetable yields in solar greenhouse production. Environ Pollut. 2021;273:116521. Epub 2021/01/29. pmid:33508627.
- 19. Liu N, Li Y, Cong P, Wang J, Guo W, Pang H, et al. Depth of straw incorporation significantly alters crop yield, soil organic carbon and total nitrogen in the North China Plain. Soil Till Res. 2021;205.
- 20. Mutegi JK, Munkholm LJ, Petersen BM, Hansen EM, Petersen SO. Nitrous oxide emissions and controls as influenced by tillage and crop residue management strategy. Soil Biol Biochem. 2010;42(10):1701–11.
- 21. Xu SS, Hou PF, Fan LH, Xue LH, Li GH. Effect of straw incorporation and domestic sewage irrigation on ammonia volatilization from paddy fields. Environ Sci. 2016;37(10):3963–70. pmid:29964433
- 22. Sun L, Wu Z, Ma Y, Liu Y, Xiong Z. Ammonia volatilization and atmospheric N deposition following straw and urea application from a rice-wheat rotation in southeastern China. Atmos Environ. 2018;181:97–105.
- 23. Lehmann J, Cowie A, Masiello CA, Kammann C, Woolf D, Amonette JE, et al. Biochar in climate change mitigation. Nat Geosci. 2021;14(12):883–92.
- 24. He T, Yun F, Liu T, Jin J, Yang Y, Fu Y, et al. Differentiated mechanisms of biochar- and straw-induced greenhouse gas emissions in tobacco fields. Appl Soil Ecol. 2021;166.
- 25. Schmidt HP, Kammann C, Hagemann N, Leifeld J, Bucheli TD, Sánchez Monedero MA, et al. Biochar in agriculture–A systematic review of 26 global meta‐analyses. GCB Bioenergy. 2021;13(11):1708–30.
- 26. Woolf D, Amonette JE, Street-Perrott FA, Lehmann J, Joseph S. Sustainable biochar to mitigate global climate change. Nat Commun. 2010;1:56. Epub 2010/10/27. pmid:20975722; PubMed Central PMCID: PMC2964457.
- 27. Haider G, Steffens D, Müller C, Kammann CI. Standard extraction methods may underestimate nitrate stocks captured by field-aged biochar. J Environ Qual. 2016;45(4):1196–204. pmid:27380067
- 28. Feng Y, Sun H, Xue L, Liu Y, Gao Q, Lu K, et al. Biochar applied at an appropriate rate can avoid increasing NH3 volatilization dramatically in rice paddy soil. Chemosphere. 2017;168:1277–84. Epub 2016/12/07. pmid:27919533.
- 29. Yang Y, Kumar Awasthi M, Wu L, Yan Y, Lv J. Microbial driving mechanism of biochar and bean dregs on NH3 and N2O emissions during composting. Bioresour Technol. 2020;315:123829. Epub 2020/07/19. pmid:32682258.
- 30. Sun H, Lu H, Chu L, Shao H, Shi W. Biochar applied with appropriate rates can reduce N leaching, keep N retention and not increase NH3 volatilization in a coastal saline soil. Sci Total Environ. 2017;575:820–5. pmid:27693153
- 31. Craswell ET, Chalk PM, Kaudal BB. Role of 15N in tracing biologically driven nitrogen dynamics in soils amended with biochar: A review. Soil Biol Biochem. 2021;162.
- 32. Liao X, Liu D, Niu Y, Chen Z, He T, Ding W. Effect of field-aged biochar on fertilizer N retention and N2O emissions: A field microplot experiment with 15N-labeled urea. Sci Total Environ. 2021;773:145645. Epub 2021/05/05. pmid:33940745.
- 33. Xu C, Han X, Ru S, Cardenas L, Rees RM, Wu D, et al. Crop straw incorporation interacts with N fertilizer on N2O emissions in an intensively cropped farmland. Geoderma. 2019;341:129–37.
- 34. Zhang H, Liang Q, Peng Z, Zhao Y, Tan Y, Zhang X, et al. Response of greenhouse gases emissions and yields to irrigation and straw practices in wheat-maize cropping system. Agr Water Manage. 2023;282:108281.
- 35. Lin J, Xu Z, Xue Y, Sun R, Yang R, Cao X, et al. N2O emissions from soils under short-term straw return in a wheat-corn rotation system are associated with changes in the abundance of functional microbes. Agri Ecosys Environ 2023;341.
- 36. Chen Z, Tu X, Meng H, Chen C, Chen Y, Elrys AS, et al. Microbial process-oriented understanding of stimulation of soil N2O emission following the input of organic materials. Environ Pollut. 2021;284:117176. Epub 20210417. pmid:33901983.
- 37. Li N, Ma X, Bai J, Xu H, Feng Y, Ren G, et al. Plastic film mulching mitigates the straw-induced soil greenhouse gas emissions in summer maize field. Appl Soil Ecolog. 2021;162.
- 38. Frimpong KA, Baggs EM. Do combined applications of crop residues and inorganic fertilizer lower emission of N2O from soil? Soil Use Manag. 2010;26(4):412–24.
- 39. Nelissen V, Rütting T, Huygens D, Staelens J, Ruysschaert G, Boeckx P. Maize biochars accelerate short-term soil nitrogen dynamics in a loamy sand soil. Soil Biol Biochem. 2012;55:20–7.
- 40. Xu S, Hou P, Xue L, Wang S, Yang L. Treated domestic sewage irrigation significantly decreased the CH4, N2O and NH3 emissions from paddy fields with straw incorporation. Atmos Environ. 2017;169:1–10.
- 41. He T, Yuan J, Xiang J, Lin Y, Luo J, Lindsey S, et al. Combined biochar and double inhibitor application offsets NH3 and N2O emissions and mitigates N leaching in paddy fields. Environ Pollut. 2022;292:118344. Epub 2021/10/13. pmid:34637831.
- 42. Mandal S, Thangarajan R, Bolan NS, Sarkar B, Khan N, Ok YS, et al. Biochar-induced concomitant decrease in ammonia volatilization and increase in nitrogen use efficiency by wheat. Chemosphere. 2016;142:120–7. pmid:25959224