Soil Ammonia Volatilization Research Articles

Soil ammonia volatilization after fertilization using antibiotic-contaminated swine wastewater

The application of wastewater from pig farming is an alternative to fertilize crops using the effluent produced in the activity. However, in addition to nutrients capable of meeting the needs of crops, this effluent also has residues of antibiotics for livestock use in its composition, which can interfere with the activity of soil microorganisms and reduce the enzymatic activity, leading to nitrogen losses into the atmosphere. Hence, this study evaluated ammonia volatilization behavior after adding swine wastewater with tetracycline-class antibiotics. Pots containing soil received doses of raw and digested wastewater (0.06 and 0.09 L), combined or not with doses of tetracycline (35 µg L-1), chlortetracycline (40.9 µg L-1), and doxycycline (14.9 µg L-1 volatilized NH3 was collected by foam absorbers containing phosphoric acid solution on the soil, which were changed every 48 h, totaling 11 collections at a time. The NH3 volatilization significantly increased when the swine wastewater (raw or digested) was added. The presence of antibiotics reduced NH3 losses, showing that they can inhibit urease activity. Our findings showed that tetracycline-class antibiotics can inhibit urease activity, contributing to the continuity of nitrogen in the soil.

Green manure combined with reduced nitrogen reduce NH3 emissions, improves yield and nitrogen use efficiencies of rice

Background Green manure is an important source of organic fertilizer. Exploring green fertilizer and nitrogen fertilizer reduction is important for agricultural production. However, few studies have been conducted, especially on the effects of different green fertilizers along with reduced nitrogen fertilizer application on soil ammonia volatilization emissions, rice yield, and nitrogen fertilizer uptake and utilization. Methods In this study, the effects of different types of green manure and reduced nitrogen fertilizer application on soil ammonia volatilization emissions, aboveground population characteristics of rice, and nitrogen fertilizer uptake and utilization were explored. This study was based on a field-positioning experiment conducted between 2020 and 2022. Six treatments were established: no nitrogen fertilizer application (CK), conventional fertilization in wheat-rice (WR), villous villosa-rice (VvR), vetch sativa-rice (VsR), rapeseed seed-rice (RR), and milk vetch-rice (GR), with a 20% reduction in nitrogen fertilizer application. The amounts of phosphorus and potassium fertilizers remained unchanged. The characteristics of ammonia volatilization loss in rice fields, agronomic traits of rice, yield traits, and nitrogen uptake and utilization were investigated. Results The results indicated a significant difference (P < 0.05) in the impact of different treatments on ammonia volatilization emissions from rice in the two-year experiment. Compared with WR treatment, VvR, VsR, RR, and GR treatments reduced the total ammonia volatilization loss by 23.58 to 39.21 kg ha−1, respectively. Compared with the conventional WR treatment, other treatments increased rice yield by 0.09 to 0.83 t ha−1. GR treatment was significantly higher than other green fertilizer treatments, except for VsR (P < 0.05). It increased the nitrogen uptake of rice by an average of 4.24%–22.24% and 13.08%–33.21% over the two years, respectively. The impact of different types of green manure on the nitrogen uptake and utilization of rice varied greatly, indicating that the combination of green manure and fertilizer is a sustainable fertilization model for crops to achieve high yields. In particular, the Chinese milk vetch as green manure was more beneficial for ammonia volatilization reduction in paddy field and stable grain production of rice.

Effects of Straw Return and Nitrogen Application Rates on Soil Ammonia Volatilization and Yield of Winter Wheat

This study investigates the impact of corn straw return and nitrogen application rates on ammonia volatilization and yield enhancement under field conditions, in order to reduce emissions while increasing crop yield. During the winter wheat season, a fissure area design was implemented, comprising three levels of straw return in the main area and three distinct nitrogen fertilizer levels in the subsidiary area, for a total of nine treatments. The results can be summarized as follows: (1) The ammonia emissions flux initially increased followed by a decrease, and was primarily concentrated within the first 14 days after fertilization, with a peak observed at 4–5 days before decreasing. Notably, nitrogen fertilizer significantly affected the cumulative ammonia emissions, ranging from 0.019 to 1.786 kg·hm−2·d−1 and 0.013 to 1.693 kg·hm−2·d−1 across the two seasons. (2) The soil with a higher nitrogen application rate exhibited elevated levels of inorganic nitrogen content and urease activity under the same straw return level. Maintaining a consistent nitrogen application level, the return of straw to the field increased the cumulative ammonia discharge, inorganic nitrogen content, and urease activity. (3) The interaction between straw return and nitrogen fertilizer substantially affected crop yield. Specifically, during the winter wheat season, the optimal combination for reducing ammonia emissions and enhancing yield was observed under straw return (both half or full) combined with 180 kg·hm−2 nitrogen application. Notably, the reduction of soil emissions and winter wheat yield augmentation were feasible through appropriate corn straw return in the preceding season.

Effects of water-nitrogen interactions on NH3 and N2O emissions and yield in winter wheat cropland

To investigate the effects of different irrigation and nitrogen application modes on nitrogen gaseous loss in winter wheat farmland, we conducted a field experiment at Changqing Irrigation Experiment Station in Shandong Province, with two irrigation levels (80%-90% θf(I1) and 70%-80% θf(I2)) and three nitrogen application levels (conventional nitrogen application of 240 kg·hm-2(N1), nitrogen reduction of 12.5% (N2), and nitrogen reduction of 25% (N3)). The results showed that ammonia volatilization and nitrous oxide emission rate peak appeared within 2-4 days after fertilization or irrigation. The ammonia volatilization rate during the chasing fertilizer period was significantly higher than that during the basal fertilizer period. Compared with other treatments, the ave-rage ammonia volatilization rate of I2N2 treatment during the chasing fertilizer period was reduced by 10.1%-51.6%, and the average nitrous oxide emission rate over the whole growth period was reduced by 15.4%-52.2%. The ammonia volatilization rate was significantly positively associated with surface soil pH value and ammonium nitrogen content, while the nitrous oxide emission rate was significantly positively associated with nitrate content in topsoil. The accumulation amount of soil ammonia volatilization and nitrous oxide emission ranged from 0.83-1.42 and 0.11-0.33 kg·hm-2, respectively. Moderate reduction of irrigation water and nitrogen input could effectively reduce cumulative amounts of ammonia volatilization and nitrous oxide emission from winter wheat farmland. The cumulative amounts of ammonia volatilization and nitrous oxide emission under I1N3 and I2N2 treatments were signi-ficantly lower than those under other treatments. The highest winter wheat yield (5615.6 kg·hm-2) appeared in I2N2 treatment. The irrigation water utilization efficiency of I2 was significantly higher than that of I1, with the maximum increase rate of 45.2%. Compared with N1 and N3 treatments, the maximum increase rate of nitrogen fertilizer productivity and agricultural utilization efficiency in N2 reached 15.2% and 31.8%, respectively. In conclusion, the treatment with 70%-80% θf irrigation level and 210 kg·hm-2 nitrogen input could effectively improve the utilization efficiency of irrigation water and nitrogen fertilization and reduce gaseous loss from winter wheat farmland.

Biochar and hydrochar application influence soil ammonia volatilization and the dissolved organic matter in salt-affected soils

Biochar, which including pyrochar (PBC) and hydrochar (HBC), has been tested as a soil enhancer to improve saline soils. However, the effects of PBC and HBC application on ammonia (NH3) volatilization and dissolved organic matter (DOM) in saline paddy soils are poorly understood. In this research, marsh moss-derived PBC and HBC biochar types were applied to paddy saline soils at 0.5 % (w/w) and 1.5 % (w/w) rates to assess their impact on soil NH3 volatilization and DOM using a soil column experiment. The results revealed that soil NH3 volatilization significantly increased by 56.1 % in the treatment with 1.5 % (w/w) HBC compared to the control without PBC or HBC. Conversely, PBC and the lower application rate of HBC led to decrease in NH3 volatilization ranging from 2.4 % to 12.1 %. Floodwater EC is a dominant factor in NH3 emission. Furthermore, the fluorescence intensities of the four fractions (all humic substances) were found to be significantly higher in the 1.5 % (w/w) HBC treatment applied compared to the other treatments, as indicated by parallel factor analysis modeling. This study highlights the potential for soil NH3 losses and DOM leaching in saline paddy soils due to the high application rate of HBC. These findings offer valuable insights into the effects of PBC and HBC on rice paddy saline soil ecosystems.

The Effect of Pyrolysis Temperature of calotropis procera Biochar on Dynamics of Petroleum Hydrocarbons Degradation, Carbon Emission, and Ammonia Volatilization in Artificial Petroleum-Contaminated Soil

Pollution by petroleum hydrocarbons (PHCs) is a current environmental challenge all over the world. Therefore, this study was established to evaluate the impact of calotropis procera biochar (CPB) produced at various pyrolysis temperatures on carbon emission, ammonia volatilization, degradation of PHCs, and properties of artificial petroleum-contaminated soil. An incubation experiment was performed with CPB produced at 400 °C (CPB400) and 650 °C (CPB650). The artificial petroleum-contaminated soil was amended with biochar at doses of 1, 2.5, and 5% along with the unamended soil (control) and incubated for 78 days. The results demonstrate that the CO2-C emission rate in petroleum-contaminated soil increases significantly with all biochar applications compared to the control treatment. Adding CPB400 into the soil, at all doses, decreased cumulative NH3 emission significantly, in comparison with control and CPB650 treatments during all incubation periods. Total PHCs concentration in the soil reduced significantly with CPB400 application at 2.5% compared to the control treatment. CPB400 was more effective in declining total PHCs content in the soil than biochar produced at 650 °C. Available phosphorus and potassium in petroleum-contaminated soil increased significantly under biochar applications compared with the control treatment. Using Calotropis procera biochar produced by low-temperature pyrolysis as an amendment can play a vital role in the remediation of PHCs in polluted soils, it is also a promising way to improve the quality indicators of petroleum-contaminated soil.

Comparison of ammonia volatilization in paddy and field soils fertilized with urea and ammonium sulfate during rice, potato, and Chinese cabbage cultivation

Ammonia in fertilizers used in agriculture is emitted into the atmosphere, which can be a precursor to the formation of fine dust that deteriorates air quality. This study investigated ammonia emissions from paddy and upland fields when urea (UR) and ammonium sulfate (AS) were used to grow rice, potato, and Chinese cabbage. Ammonia emissions from agricultural fields, water/soil properties, and meteorological data were monitored. In the paddy fields, the highest level of ammonia emissions was observed immediately after basal fertilization. However, this trend was not observed in the upland fields, where the application of a top dressing to moist soil led to an increase in ammonia emissions. In rice paddy fields and Chinese cabbage upland fields, higher ammonia emissions were observed under UR fertilization than under AS fertilization; whereas, no discrepancy was observed in the potato upland fields. A random forest model was used to determine the importance of environmental variables in ammonia emissions. The results indicated that UR application was the most significant factor affecting ammonia emissions, followed by the NH4+ concentration in ponding water in paddy fields. In upland fields, the soil water content was an important factor, and the temperature of ponding water influenced ammonia emissions. Most of the agronomic traits of rice and Chinese cabbage improved with increased amounts of fertilizer, whereas such a trend was not observed for potato. This study provides new insight into the environmental factors influencing ammonia emissions in agricultural settings. These findings serve as a foundation for the development of strategies and practices aimed at mitigating future ammonia emissions.

Promotion effects of salt-alkali on ammonia volatilization in a coastal soil

Coastal ecosystems are highly susceptible to salt-related problems due to their formation process and geographical location. As such ecosystems are the most accessible land resources on Earth, clarifying and quantifying the effects of salt-alkali conditions on N concentration and ammonia (NH3) volatilization are pivotal for promoting coastal agricultural productivity. The challenge in establishing this effect is to determine how salt-alkali conditions impact NH3 volatilization through direct or indirect interactions. An incubation experiment using a coastal soil from a paddy farmland, combined with the structural equation modeling (SEM) method, was conducted to reveal the net effects of salt-alkali on NH3 volatilization and the role of environmental and microbial factors in mutual interaction networks. The specific experimental design consisted of four salt treatments (S1, S2, S3, and S4: 1‰, 3‰, 8‰, and 15‰ NaCl by mass of soil, respectively), four alkaline treatments (A1, A2, A3, and A4: 0.5‰, 1‰, 3‰, and 8‰ NaHCO3 by mass of soil, respectively) and a control without NaCl or NaHCO3 addition (CK), and each treatment had three urea concentrations (N1, N2, and N3: 0.05, 0.10, and 0.15 g N kg-1 soil, respectively) and three replicates. At the N1, N2, and N3 levels, NH3 volatilization increased by 9.31%–34.98%, 3.07%–26.92%, and 2.99%–43.61% as the NaCl concentration increased from 1‰ to 15‰, respectively, compared with CK. With an increase in the NaHCO3 concentration from 0.5‰ to 8‰, NH3 volatilization increased by 8.36%–56.46%, 5.49%–30.10%, and 30.72%–73.18% at the N1, N2, and N3 levels, respectively, compared with CK. According to the SEM method, salinity and alkalinity had positive direct effects on NH3 volatilization, with standardized path coefficients of 0.40 and 0.19, respectively. Considering the total effects (net positive and negative effects) in the SEM results, alkalinity had a greater influence than salinity (total standardized coefficient 0.104 > 0.086). Nitrogen concentrations in the incubation system showed a direct positive effect on NH3 volatilization (standardized path coefficient = 0.78), with an obvious decrease under elevated salinity and alkalinity levels. Additionally, gene abundances of nitrogen-transforming microbes indirectly increased NH3 volatilization (total indirect standardized coefficient = 0.31). Our results indicated that potential NH3 emissions from coastal saline areas could be enhanced more by soil alkalization than by salinization.

Insight into the functional mechanisms of nitrogen-cycling inhibitors in decreasing yield-scaled ammonia volatilization and nitrous oxide emission: A global meta-analysis

Soil ammonia (NH3) volatilization and nitrous oxide (N2O) emission decrease nitrogen (N) utilization efficiency and cause some environmental problems. The N-cycling inhibitors are suggested to apply to enhance N utilization efficiency. Quantifying effects of N-cycling inhibitors on yield-scaled NH3 volatilization and N2O emission and functional genes could provide support for the optimal selection and application of N-cycling inhibitor. We conducted a meta-analysis to reveal the effects of N-cycling inhibitors on soil abiotic properties, functional genes and yield-scaled NH3 volatilization and N2O emission by extracting data from 166 published articles and linked their comprehensive relationships. The N-cycling inhibitors in this meta-analysis mainly includes nitrification inhibitors 3, 4-dimethyl pyrazole phosphate, dicyandiamide and 2-chloro-6-trichloromethylpyridine, urease inhibitor N-(n-butyl) thiophosphoric triamide and biological nitrification inhibitors methyl 4-hydroxybenzoate and 1, 9-decanediol. The N-cycling inhibitor applications significantly increased alkaline soil pH but significantly decreased acidic soil pH. The N-cycling inhibitors decreased soil AOB amoA gene abundances mostly under the condition of pH 4.5–6 (mean: 212%, 95% confidence intervals (CI): 249% and −176%) and significantly decreased nirS gene (mean: 39%; 95% CI: 72% and −6%). The yield-scaled NH3 volatilization was significantly decreased by the N-cycling inhibitors under the condition of soil pH = 7–8.5 (mean: 45%; 95% CI: 59% and −31%). The yield-scaled N2O emission was also significantly reduced by all N-cycling inhibitors and had negative correlations with the soil nirK and nirS gene abundances. The effects of N-cycling inhibitors on soil pH, ammonium-N, nitrate-N and nitrifying and denitrifying genes and yield-scaled NH3 volatilization and N2O emission were dominated by the inhibitor types, soil textures, crop species and environmental pH. Our study could provide technical support for the optimal selection and application of N-cycling inhibitor under different environmental conditions.

Corn Cropping System and Nitrogen Fertilizers Technologies Affect Ammonia Volatilization in Brazilian Tropical Soils

The adoption of technologies for N fertilization has become essential for increasing the N use efficiency in no-till (NT) systems in Brazil. Thus, this study aimed to quantify ammonia losses, N removal in grains, and second crop season yield in no-till and conventional (T) areas that received the application of different N fertilizers and their technologies. Ammonia volatilization, N extraction in grains, and corn yield in response to the application of conventional fertilizers were compared to urea treated with urease inhibitors in NT and conventional systems. The treatments were: no-N (Control); Prilled urea (PU); urea + N-(n-Butyl) thiophosphoric triamide (UNBPT); urea + Cu + B (UCuB); ammonium nitrate (AN), and ammonium sulfate (AS). In the NT system, the N-NH3 losses were 49% higher than in the conventional; without differences in corn yield. The fertilizers AN and AS had the lowest N-NH3 losses, regardless of the tillage system. UNBPT reduced the mean N-NH3 loss by 33% compared to PU. UNBPT (1200 mg kg−1) and UNBPT (180 mg kg−1) reduced the N-NH3 losses by 72% and 22%, respectively, compared to PU in the NT system. We noticed that the NBPT concentration to be used in soils under NT should be adjusted, and a reduction of N-NH3 losses does not directly reflect an increase in yield and N extraction by corn.

Arbuscular Mycorrhizal Fungi Shift Soil Bacterial Community Composition and Reduce Soil Ammonia Volatilization and Nitrous Oxide Emissions.

Arbuscular mycorrhizal fungi (AMF) establish mutualistic relationships with the majority of terrestrial plants, increasing plant uptake of soil nitrogen (N) in exchange for photosynthates. And may influence soil ammonia (NH3) volatilization and nitrous oxide (N2O) emissions directly by improving plant N uptake, and/or indirectly by modifying soil bacterial community composition for the soil C availability increasing. However, the effects of AMF on soil NH3 volatilization and N2O emissions and their underlying mechanisms remain unclear. We carried out two independent experiments using contrasting methods, one with a compartmental box device (in 2016) and the other with growth pot experiment (in 2020) to examine functional relationships between AMF and soil NH3 volatilization and N2O emissions under varying N input. The presence of AMF significantly reduced soil NH3 volatilization and N2O emissions while enhancing plant biomass and plant N acquisition, and reducing soil NH4+ and NO3-, even with high N input. The presence of AMF also significantly reduced the relative abundance within the bacterial orders Sphingomonadales and Rhizobiales. Sphingomonadales correlated significantly and positively with soil NH3 volatilization in 2016 and N2O emissions, whereas Rhizobiales correlated positively with soil N2O emissions. High N input significantly increased soil NH3 volatilization and N2O emissions with increasing relative abundance of Sphingomonadales and Rhizobiales. These findings demonstrate the contribution of AMF in regulating NH3 and N2O emission by improving plant N uptake and altering soil bacterial communities. They also suggest that altering the rhizosphere microbiome might offer additional potential for restoration of N-enriched agroecosystems.

A Study of Controlling of Soil Ammonia Volatilization by Bacillus amyloliquefaciens and Its Mechanism

A Study of Controlling of Soil Ammonia Volatilization by Bacillus amyloliquefaciens and Its Mechanism

Environmental risk of microplastics after field aging: Reduced rice yield without mitigating yield-scale ammonia volatilization from paddy soils

Microplastics (MPs, <5 mm) are enriched in paddy ecosystems as emerging environmental pollutants. Biochar (BC) is a controversial recalcitrant carbon product that poses potential environmental risks. The presence of these two exogenous organic substances has been demonstrated to have impacts on soil nitrogen cycling and crop production. However, the after-effects of MPs and BC on soil ammonia (NH3) volatilization and rice yield after field aging remain unexplored. In this study, two common MPs, including polyethylene (PE) and polyacrylonitrile (PAN), and BC were selected for rice growing season observations to study the impacts on soil NH3 volatilization and rice yield after field aging. The results showed that the reduction of cumulative soil NH3 losses by MPs was around 45% after one-year field aging, which was within the range of 40–57% in the previous rice season. Abatement of NH3 volatilization by MPs mainly occurred in basal fertilization and was related to floodwater pH. Besides, the reduction rate of NH3 volatilization by BC and MPs + BC was enhanced after field aging (63% and 50–57%) compared to that in the previous rice season (5% and 11–19%), with the abatement process occurring in the first supplementary fertilization. There was a significant positive correlation between cumulative NH3 volatilization and soil urease activity. Notably, field aging removed the positive effect of MPs and MPs + BC in reducing yield-scale NH3 losses in the previous rice season (∼62%). Furthermore, despite BC affecting rice yield insignificantly after field aging, the presence of MPs led to a significant 17–19% reduction in rice yield. Our findings reveal that differences in the after-effects of BC and MPs in field aging emerge, where the negative impacts of MPs on soil NH3 abatement and crop yield are progressively becoming apparent and should be taken into serious consideration.

Cover crops and N fertilization affect soil ammonia volatilization and N2O emission by regulating the soil labile carbon and nitrogen fractions

Introducing cover crops in monocropping systems to improve soil health has been broadly adopted worldwide. However, the impacts of different cover cropping systems on soil emissions and related soil fractions and their regulatory mechanism remain elusive. In this study, four cropping systems, i.e., relay intercropping with Orychophragmus violaceus L./cotton (OvC), Vicia villosa Roth/cotton (VvC), a cover crop mixture (Ov and Vv)/cotton (MSC) and a fallow field–cotton (FFC) system, were combined with four N application rates in a two-rotation cycle (2019–2021) to evaluate the effects on soil greenhouse gases (GHGs) emission, ammonia (NH3) volatilization, and labile carbon (C) and nitrogen (N) fractions and their relationships. Compared with the FFC system, the cumulative NH3 volatilization and nitrous oxide (N2O) emissions of OvC are noticeably reduced 13% and 58%, respectively, and those of VvC are comparable, while those of MSC are markedly increased by 15% and 24%, respectively. N fertilization significantly affects soil NH3 volatilization and N2O emissions, and a higher N rate results in more gaseous N emissions. In addition, NH3 volatilization and N2O emission are positively correlated with the soil microbial biomass N (MBN), dissolved organic N (DON), NH4+-N and NO3--N but negatively correlated with microbial biomass C (MBC) and dissolved organic C (DOC). OvC system decreased gaseous N emission by high soil MBC/MBN ratio, Vv as cover crop indirectly promote soil N2O emission through increased soil MBN, DON and MBC content, while cover crop mixtures increase soil labile C and N fractions and enhance gaseous N emission ultimately. Overall, application of N fertilizer and cover crop mixture both promoted soil NH3 and N2O emissions; the relay intercropping nonlegume cover crop Ov noticeably mitigates N2O and NH3 emissions through an increase in the soil MBC and reduce in the labile N, while introduction of the legume cover crop Vv increases N2O emissions but reduces soil NH3 volatilization due to a lower soil MBC/MBN ratio.

Hydrochar and microplastics disturb soil dissolved organic matter and prominently mitigate ammonia volatilization from wheat growing soil

The impacts of microplastics (MPs) pollution on the nitrogen (N) cycle in soil ecosystems have attracted worldwide attention. Meanwhile, dissolved organic matter (DOM)-rich hydrochar (HBC) is being tried as an emerging soil conditioner for gaseous N reduction load to the atmosphere. However, the influence of MPs and HBC on soil DOM and ammonia (NH3) volatilization in wheat soils remains poorly understood. In this study, a soil column experiment was established in wheat growing soils to determine the impacts of HBC, MPs (i.e., polyethylene and polyacrylonitrile), and the co-occurrence of HBC and MPs (HBC + MPs) on soil NH3 volatilization, physicochemical properties and wheat growth. In comparison with the control (CK, without MPs or HBC), HBC, MPs, and HBC + MPs reduced cumulative NH3 volatilization by 45.4%, 66.7–67.4% and 29.8–58.7%, respectively. Soil DOM fulvic acid-like and humic aid substance abundances of the other treatments were increased by 18.5–56.2% and 12.7–39.3%, respectively, compared to CK. Besides, soil NH3 fluxes were positively correlated to soil NH4+-N concentration at basal fertilization and soil NO3−-N concentration at first supplementary fertilization. HBC, MPs and HBC + MPs treatments promoted soil urease activity and plant N uptake by 6.5–24.2% and 31.9–74.3%, respectively, compared to CK. This study provides an insight into the variation of NH3 volatilization caused by anthropogenic carbon in wheat soil ecosystems.

Effects of Straw Returning on Soil Ammonia Volatilization Under Different Production Conditions Based on Meta-analysis

In order to explore the response of Chinese farmland soil ammonia volatilization to straw returning to the field under different production conditions, this study used no straw returning as a control. Through the collection of published literature test data, the Meta-analysis method was used to quantitatively study the effects of different natural factors and, under the conditions of farmland management measures, the effect of returning straw to the field on the emission reduction of soil ammonia volatilization. At the same time, through partial correlation analysis, the main influencing factors of ammonia volatilization under the condition of returning straw to the field were found, and the ammonia volatilization was quantified. The results showed that the effect of straw returning on soil ammonia volatilization decreased with the increase in accumulated rainfall during the growth period and increased with the increase in average temperature during the growth period. When the soil pH was less than 6, straw returning to the field significantly promoted soil ammonia volatilization, and when the pH was ≥ 6, returning straw to the field significantly inhibited ammonia volatilization in the soil. The reduction effect of returning straw to the field on soil ammonia volatilization increased with the increase in soil clay content. When the total soil nitrogen content was <0.1% and >0.2%, returning the straw to the field significantly inhibited the volatilization of soil ammonia, and when the total soil nitrogen content was between 0.1% and 0.2%, returning the straw to the field significantly promoted the volatilization of ammonia from the soil. When the nitrogen application rate was 60-180 kg·hm-2 and the nitrogen application rate was >240 kg·hm-2, returning straw to the field significantly reduced soil ammonia volatilization (P<0.05), and when nitrogen application rate was 180-240 kg·hm-2, returning straw to the field significantly promoted ammonia volatilization in the soil. Returning straw to the field by plowing or rotary tillage significantly inhibited ammonia volatilization in the soil, whereas returning straw to the field in a mulching mode had no significant effect on ammonia volatilization. When the straw C/N>45, it significantly inhibited ammonia volatilization from the soil, and when the straw C/N ≤ 45, the straw returning to the field significantly promoted the ammonia volatilization of the soil. The reduction effect of straw returning on ammonia volatilization increased with the increase in straw-returning amount. In non-paddy fields, returning straw to the field had a significant inhibitory effect on soil ammonia volatilization, and in paddy fields, returning straw to the field had a significant effect on soil ammonia volatilization. The results of partial correlation analysis showed that in paddy fields, the average growth period and soil pH were the main factors affecting soil ammonia volatilization under the condition of returning straw to the field, and in non-paddy fields, nitrogen application rate and straw C/N were the main factors affecting the conditions. This study can provide reference for the scientific and rational use of straw to achieve ammonia volatilization emission reduction in farmland.

How does biochar aging affect NH3 volatilization and GHGs emissions from agricultural soils?

Biochar has been considered as a potential tool to mitigate soil ammonia (NH3) volatilization and greenhouse gases (GHGs) emissions in recent years. However, the aging effect of biochar on soils remains elusive, which introduces uncertainty on the effectiveness of biochar to mitigate global warming in a long term. Here, a meta-analysis of 22 published works of literature with 217 observations was conducted to systematically explore the aging effect of biochar on soil NH3 and GHGs emissions. The results show that, in comparison with the fresh biochar, the aging makes biochar more effective to decrease soil NH3 volatilization by 7% and less risk to contribute CH4 emissions by 11%. However, the mitigation effect of biochar on soil N2O emissions is decreased by 15% due to aging. Additionally, aging leads to a promotion effect on soil CO2 emissions by 25% than fresh biochar. Our findings suggest that along with aging, particularly the effect of artificial aging, biochar could further benefit the alleviation of soil NH3 volatilization, whereas its potential role to mitigate global warming may decrease. This study provides a systematic assessment of the aging effect of biochar to mitigate soil NH3 and GHGs, which can provide a scientific basis for the sustainable green development of biochar application.

Nutrient Release and Ammonia Volatilization from Biochar-Blended Fertilizer with and without Densification

Blending fertilizer with biochar followed by densification to make it into a tablet can enhance the adsorption of fertilizer on the biochar surface and reduce the nutrient loss during handling. However, the nutrient release and ammonia volatilization from biochar-blended fertilizer with and without densification are not well understood. The objectives of this study were to determine the nutrient release and ammonia volatilization from an acid soil applied with biochar-blended NPK fertilizer with and without densification. The nutrient release of biochar-blended NPK was determined using water incubation for 30 days, whereas daily loss of ammonia was measured using a closed dynamic air flow system for 10 days. The densified biochar-blended NPK caused stronger physical binding of the nutrients within the tablet in addition to stronger chemical bondings between the nutrients with the biochar’s functional groups. As a result, nutrient release in the water incubation from the biochar-blended NPK fertilizer tablet was slower. However, blending the biochar with the NPK fertilizer increased soil ammonia volatilization relative to the NPK fertilizer alone. This demonstrates that the biochar-blended fertilizer tablet has the potential to serve as a slow release fertilizer for crop cultivation.

Efficiency and mechanism of reducing ammonia volatilization in alkaline farmland soil using Bacillus amyloliquefaciens biofertilizer

Ammonia volatilization from the farmland caused by the application of synthetic nitrogen fertilizer is the most important source of anthropogenic ammonia emissions. Biofertilizer application has been considered as an alternative option for agriculture sustainability and soil improvement. In this study, field trials were carried out to investigate the efficiency of Bacillus amyloliquefaciens (BA) biofertilizer on alleviating ammonia volatilization in alkaline farmland soil and increasing crop yield and nitrogen utilization. Potential response mechanisms were investigated from soil enzyme, nitrogen cycle function genes and microbial community levels. Compared with conventional fertilization, BA biofertilizer application reduced the ammonia volatilization by 68%, increased the crop yield and nitrogen recovery by 19% and 19%, respectively. Soil enzyme activity analysis showed that BA biofertilizer inhibited the urease activity and enhanced the potential ammonia oxidation (PAO). In addition, BA biofertilizer application also increased the bacterial amoA gene abundance, while decreased the ureC gene abundance. BA biofertilizer also significantly altered the community structure and composition, and especially raised the abundance of ammonia oxidation bacteria (AOB), while no changes were observed in abundance of nitrite oxidation bacteria (NOB). Briefly, BA biofertilizer was approved to reduce the transformation of fertilizer nitrogen to NH4+-N, simultaneously accelerating NH4+-N into the nitrification process, thus decreasing the NH4+-N content remained in alkaline soil and consequently alleviating the ammonia volatilization. Thus, these results suggested that the application of BA biofertilizer is a feasible strategy to improve crop yields and reduce agricultural ammonia emissions.

Use of ammonium sulphate as a sulphur fertilizer: Implications for ammonia volatilization.

Ammonium sulphate is widely used as a sulphur (S) fertilizer, constituting about 50% of global S use. Within nitrogen (N) management, it is well known that ammonium‐based fertilizers are subject to ammonia (NH3) volatilization in soils with pH > 7, but this has been overlooked in decision making on S fertilization. We reviewed 41 publications reporting measurements of NH3 loss from ammonium sulphate in 16 countries covering a wide range of soil types and climates. In field experiments, loss was mostly <5% of applied N in soils with pH (in water) <7.0. In soils with pH > 7.0, there was a wide range of losses (0%–66%), with many in the 20%–40% range and some indication of increased loss (ca. 5%–15%) in soils with pH 6.5–7.0. We estimate that replacing ammonium sulphate with a different form of S for arable crops could decrease NH3 emissions from this source by 90%, even taking account of likely emissions from alternative fertilizers to replace the N, but chosen for low NH3 emission. For every kt of ammonium sulphate replaced on soils of pH > 7.0 in temperate regions, NH3 emission would decrease from 35.7 to 3.6 t NH3. Other readily available sources of S include single superphosphate, potassium sulphate, magnesium sulphate, calcium sulphate dihydrate (gypsum), and polyhalite (Polysulphate). In view of the large areas of high pH soils globally, this change of S fertilizer selection would make a significant contribution to decreasing NH3 emissions worldwide, contributing to necessary cuts to meet agreed ceilings under the Gothenburg Convention.