NH3 Loss 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.

Field efficacy of urease inhibitors for mitigation of ammonia emissions in agricultural field settings: a systematic review

Globally, ammonia (NH3) is one of the key air pollutants and reducing NH3 emissions and the associated indirect emission of the greenhouse gas nitrous oxide remains challenging for the agricultural sector. During the past three decades, a number of urease inhibitors have been placed on the market with the goal of reducing NH3 loss from urea containing fertilisers. N–(n-butyl) thiophosphoric triamide (NBPT), N–(2-nitrophenyl) phosphoric triamide (2-NPT), a 3:1 ratio of NBPT + N-(n-propyl) thiophosphoric triamide (NPPT) and the maleic and itaconic acid co-polymer (MIP) are registered urease inhibitors under the European Commission Fertilising Products Regulation (FPR). However, the availability of several inhibitor options has raised questions from farmers, policymakers and emissions inventory compiling authorities regarding the field efficacy of the different options available for reducing NH3 loss. Despite many disparate NH3 field studies existing for NBPT, 2-NPT, NBPT + NPPT and MIP there is presently no review that brings these results together, a significant and important knowledge gap. This review addresses the gap by summarising the published field trial literature on NH3 volatilisation mitigation offered by NBPT, 2-NPT, NBPT + NPPT and MIP. Our review identified 48 peer reviewed studies where NH3 loss mitigation was measured in a field setting, giving 256 replicated comparisons. The synthesised literature results revealed that NBPT + NPPT reduced NH3 loss by 75% (95% CI = 58–82% n = 32), 2-NPT reduced NH3 loss by 70% (95% CI = 63–76% n = 19) and NBPT reduced NH3 loss by 61% (95% CI = 57–64% n = 165), giving on average a 69% reduction by these three urease inhibitors. In contrast, MIP increased NH3 loss by 0.3% on average (95% CI = −8–9% n = 40). The results presented in this review broaden the understanding of urease inhibitor efficacy in field conditions and demonstrate that not all products behave the same in terms of field NH3 reduction efficacy. This review is important for farmers, policymakers, emission inventory compilers and other stakeholders.

Biochar as an Alternative Litter Additive to Mitigate Gaseous Emissions from Broiler Housing and Subsequent Storage

Broiler farming is a significant source of gaseous emissions. The aim of this study was to assess the effects of different litter additives on the emission of NH3, N2O, CO2, and CH4 during broiler housing and subsequent manure storage. The gaseous emissions from the housing facilities were evaluated during one fattening cycle in environmentally controlled rooms with three different additives applied to the litter material (10% w/w aluminum sulphate or biochar and 2.50 mg m−2 urease inhibitor), as well as a control. A storage experiment was conducted under laboratory conditions for 90 days to evaluate the influence of these three additives on gaseous losses. During broiler housing, the results indicated that NH3 emissions were reduced significantly (40–60%) by litter additives, while global warming potential (GWP) emissions were reduced significantly (31%) by Alum. The addition of Biochar (a 58% reduction) had the same significant effect as Alum (a 60% reduction) to mitigate these losses. The re-application of Urease (a 41% reduction) may be required to reach an equal or higher reduction. During storage, NH3 and GWP emissions were not significantly affected by the litter additives. During broiler housing and subsequent manure storage, NH3 emissions were reduced significantly (22–41%) by litter additives, whereas GWP emissions did not decrease significantly. Globally, it can be concluded that Biochar appears to be a good alternative to Alum due to its equal effectiveness in mitigating NH3 losses, without increasing the GWP potential in the housing and avoiding pollution swapping.

Enriched rice husk biochar superior to commercial biochar in ameliorating ammonia loss from urea fertilizer and improving plant uptake

Adding value to agricultural leftovers and turning them into biochar is a viable way to replenish soil nutrients and boost crop productivity. To further validate the efficacy of enriched rice husk biochar, an incubation study and a pot experiment were conducted: (1) to describe the effect of enriched rice husk biochar addition on soil total N, soil exchangeable NH4+ and available NO3− and (2) to describe the effect of enriched rice husk biochar on improving N, P, K, Ca, and Mg uptake, use efficiency, and dry matter production of rice plants. The amount of NH3 loss that was considerably reduced by rice husk biochar at 5 and 10 t ha−1 was 34 % lower than the control. The availability of soil total N, exchangeable NH4+, available NO3−, available P, and exchangeable cations was greatly enhanced by the addition of rice husk biochar. Due to the effective nutrient uptake that occurs with an increase in soil nutrient level, the physical growth of the rice plant (height, tiller number, greenness, and panicle number) increeased significantly in treatments supplemented with 5 t ha−1 rice husk biochar. When rice plants were treated with 5 t ha−1 rice husk biochar, their absorption of N, P, and K increased by >80 %, respectively. The production of dry matter in rice plants increased as a result of the increased N intake. The application of 5 t ha−1 of rice husk biochar enhanced the soil nutrients by reducing NH3 loss and augmenting soil nutrients for efficient plant absorption, as demonstrated by the favourable enhancement of soil macro- and micronutrients and biomass of rice plants.

Green manuring alters reactive N losses and N pools in arable soils: A meta-regression study

Green manuring is a conservation agricultural practice that improves soil quality and crop yield. However, increasing the active nitrogen (N) and carbon (C) pools during green manure (GM) amendment may accelerate soil N transformation and stimulate N loss. Previous studies have reported the effects of cover crop incorporation on N2O emission; however, the driving mechanisms and other N losses remain unclear. Therefore, we conducted a comprehensive meta-analysis of 109 published articles (517 paired observations) to clarify the effects of GM amendment on soil reactive N (Nr) losses (N2O emissions, NH3 volatilization, and N leaching and runoff), N pools, and N cycling functional gene abundance. The results showed that green manuring increased soil microbial biomass N (MBN) and NO3−-N concentrations and stimulated N2O emission but significantly lowered N leaching and yield-scaled NH3 volatilization. Practices of green manuring made a dominant contribution to the variation in N2O emissions and NH3 volatilization after GM application. Furthermore, applying legume-based GM, using N derived from GM (GMN) as an additional input, and short-term GM amendment each stimulated N2O emissions. In contrast, adopting non-legume GM, using GMN to partially substitute mineral N, and applying GM to the soil surface or paddy field mitigated NH3 loss during GM amendment. Additionally, the variation in NH3 volatilization was positively related to soil pH and N application rate (NAR) but had a negative relationship with mean annual precipitation (MAP). This study highlighted the marked effects of green manuring on soil N retention and loss. Agricultural operations that adopt GM amendment should select suitable GM species and optimize mineral N inputs to minimize N loss.

Stacking nitrogen management practices: Combining double‐slot fertilizer injection with urease and nitrification inhibitors improves yields and reduces ammonia and nitrous oxide emissions

AbstractAmmonia loss following nitrogen fertilization can degrade air quality and impact human health, whereas nitrous oxide (N2O) can contribute to global warming and climate change. Mitigation practices that target only one N‐loss pathway can lead to pollution swamping; hence, practices targeting both N‐losses are required. A 3‐year field study examined fertilizer N‐placement (broadcast urea, single‐slot injection of urea ammonium nitrate [UAN], double‐slot UAN injection) and N‐metabolization inhibitors (with/without urease and nitrification inhibitors) impacts on NH3 and N2O losses and corn yields. Ammonia volatilization was reduced (p < 0.05) by 26% with single‐slot UAN injection (10.6 kg N ha−1) and by 63% with double‐slot UAN injection (5.32 kg N ha−1) compared to broadcast urea (14.3 kg N ha−1). Dual urease and nitrification inhibitors reduced NH3 volatilization (0.84–3.86 kg N ha−1) by 57%–92% compared to no inhibitors (5.32–14.3 kg N ha−1). When no inhibitors were applied, N2O emissions from slot injection (6.43–7.62 kg N ha−1) were 2.6–3.1 times greater than from broadcast urea (2.43 kg N ha−1). Dual inhibitors reduced N2O emissions by 43% from 6.43 to 3.66 kg N ha−1 with double‐slot injection. Double‐slot UAN injection increased corn grain yields (9.73 t ha−1) by 12%–13% compared to single‐slot UAN injection (8.71 t ha−1) and broadcast urea (8.6 t ha−1). Double‐slot UAN injection effectively decreased NH3 losses and increased corn grain yields, but dual N inhibitors were required to also reduce N2O. Hence, combined productivity and environmental benefits were accrued only when fertilizer containing urease and nitrification inhibitors was combined with double‐slot injection.

Site-Specific Photochemistry along a Protonated Peptide Scaffold.

We present a detailed study of the time-dependent photophysics and photochemistry of a known conformation of the two protonated pentapeptides Leu-enkephalin (Tyrosine-Glycine-Glycine-Phenylalanine-Leucine, YGGFL) and its chromophore-swapped analogue FGGYL, carried out under cryo-cooled conditions in the gas phase. Using ultraviolet-infrared (UV-IR) double resonance, we record excited state IR spectra as a function of time delay between UV and IR pulses. We identify unique Tyr OH stretch transitions due to the S1 state and the vibrationally excited triplet state(s) formed by intersystem crossing, Tn(v). Photofragment mass spectra are recorded out of the S1 origin and following UV-IR double resonance. Several competing site-specific fragmentation pathways are discovered involving peptide backbone cleavage, Tyr side chain loss, and N-terminal NH3 loss mediated by electron transfer. In YGGFL, IR excitation in the S1 state promotes electron transfer (ET) from the aromatic ring to the N-terminal R-NH3+ group leading to loss of neutral NH3. This product channel is missing in FGGYL due to the larger distance for ET from Y(4) to NH3+. Selective loss of the Tyr side chain occurs out of an excited state process following UV excitation and is further enhanced by IR excitation in S1 and Tn(v) states of both YGGFL and FGGYL. Finally, IR excitation in the S1 or Tn(v) states fragments the peptide backbone exclusively at amide(4), producing the b4 cation. We postulate that this selective fragmentation results from intersystem crossing to produce vibrationally excited triplets with enough energy to launch the proton along a proton conduit present in the known starting structure.

Urine-enriched biochar: Coupling sustainability in sanitation and agriculture

Linear models of fertilizer production and application are environmentally harmful. Predominant approaches to waste management treat human excreta as a pollutant rather than a source of nutrients for agriculture. Container-based sanitation (CBS) systems safely contain and transport excreta for treatment and reuse, though urine is often contained but not treated. A major challenge of urine-nutrient recovery is the shift in nitrogenous species in urine during storage, from urea to ammonia (NH3) and ammonium (NH4+), due to urease activity. This can lead to gaseous NH3 losses from urine that depletes its fertilizer potential. Urine-enriched biochar (UEBC) may act as a slow-release fertilizer of urine nutrients. We quantified the adsorption of nitrogen in fresh, stored, and CBS-style urine to wood waste, sewage sludge, and walnut shell biochars. These UEBCs were compared to urine-only treatments and fertilized and unfertilized controls in a greenhouse growth experiment. We found that the <500-µm biochar size fraction retained significantly more nitrogen than larger particles across biochars. Urine-nitrogen adsorption to biochar and uptake into plant tissue varied across biochar type and urine condition. The quantity of urine applied in urine-only treatments, regardless of type, was positively correlated with plant nitrogen uptake. Plant biomass did not differ significantly across treatments. These findings emphasize the need to optimize UEBC application for different urine and biochar conditions, particularly for CBS and other urine-diverting operations.

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.

Stover mulching in no-tillage farming reduces ammonia volatilization in the Mollisol of Northeast China: Insights from gross N transformation dynamics

Ammonia (NH3) volatilization, a critical pathway of nitrogen (N) loss in agroecosystems, is closely regulated by ammonium (NH4+-N) availability and associated NH4+-N transformation dynamics in soil. To determine the effect of no-tillage and crop stover retention on soil internal gross N transformation and further NH3 volatilization in the long-term conservation tillage (CT) agroecosystem, a combination of 15N-tracing field monitoring and paired 15N-labeled incubation experiments was simultaneously conducted on a 9-year maize cropping system in the Mollisol of Northeast China. Three treatments were set up: traditional ridge tillage (RT), no-tillage with maize stover removal (NT0), and no-tillage with full harvest (ca. 7500 kg ha−1 yr−1) maize stover mulching (NTS). It was found that NH3 volatilization in the experimental Mollisol primarily occurred within 7 days after fertilization. Given that the paired gross NH4+-N transformation dynamics were considered in terms of the mutual production-consumption processes, the low fertilizer-derived NH3 volatilization was mainly attributed to a high gross N transformation rate combined with a low net N transformation rate for all treated plots, indicating that there was a rapid internal NH4+-N turnover in the studied Mollisols. Additionally, no-tillage with maize stover mulching considerably reduced NH3 emissions by 17% compared with RT treatment, and the inhibitory effect was primarily owing to the synchronized stimulation of biotic mineralization-immobilization and abiotic adsorption-release turnover in the CT agroecosystem. These findings suggest that long-term no-tillage with maize stover mulching could be a sustainable management strategy for improving soil NH4+-N retention and mitigating NH3 losses in the Mollisol of Northeast China.

False-positive MDA findings in HRMS-based screening of putrefied postmortem blood samples-Identification of the interference as N-acetyltyramine.

An unidentified compound in putrefied postmortem blood samples showed identical accurate mass and chromatographic behavior as 3,4-methylenedioxyamphetamine (MDA) and led to false-positive preliminary screening results. The aim of the study was to identify this unknown interference. Postmortem blood samples were analyzed after protein precipitation on a QExactive Focus high-resolution mass spectrometer (Thermo Fisher, Germany) coupled to a RP C18 column (Macherey-Nagel, Germany). Based on the analysis of mass spectrometry (MS) adducts and isotope ratios using fullscan (m/z 134-330) information, the empiric formula of the protonated molecule [M + H]+ of the unknown compound was found to be C10H14O2N (+ 0.6 ppm). Product ion spectra recorded using normalized collision energy 22% showed a base peak of C8H9O1 (+ 1.5 ppm) and a low-abundant water loss to C7H9 (+ 1.9 ppm), neutral losses of C2H2O and NH3 were found. Based on fullscan and MS-MS information and under consideration of the observed order of neutral losses, the compound was presumptively identified as N-acetyltyramine. This assumption was supported by SIRIUS software showing a SIRIUS score of 99.43% for N-acetyltyramine. Finally, the putative structure annotation was confirmed by a reference compound. The described false-positive MDA findings could be attributed to the presence of N-acetyltyramine in putrefied blood samples. Being an isomer of MDA, N-acetyltyramine could not be distinguished by high-resolution data of the protonated molecules. The presented results once again highlight that false-positive findings may occur even in hyphenatedhigh-resolution mass spectrometry (HRMS) when using full-scan information only.

Co-application of straw incorporation and biochar addition stimulated soil N2O and NH3 productions.

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.

Influence of Different Agro-Food Waste on Ammonia and Greenhouse Gas Emissions during Composting

Composting is one of the best organic waste management techniques, with zero waste; however, it generates environmental impacts. The objective of this study was to evaluate the emission of NH3, N2O, CO2, and CH4 from the composting of olive, elderberry, and grape agro-food waste. The experiment was carried out using reactors receiving straw as control and three treatments receiving mixtures of straw and olive, elderberry, or grape wastes. The gas emissions were measured for 150 days, and the composition of the mixtures and composts was determined. The results showed NH3 and CH4 emissions were reduced by 48% and 29% by the Olive and Elderberry treatments, while only NH3 loss was reduced by 24% by the Grape treatment. Nitrous oxide, CO2, and GWP emissions were reduced by 46%, 32%, and 34% by the Olive treatment, while these losses were not reduced by the Elderberry or Grape treatments. It can be concluded olive waste can effectively reduce NH3 and GWP, while elderberry and grape wastes are also effective in reducing NH3, but not GWP. Thus, the addition of agro-food waste appears to be a promising mitigation strategy to reduce gaseous losses from the composting process.

Mapping crop-specific emission factors highlights hotspots of ammonia mitigation in China

Mapping gridded emission factors (EFs) of crops is vital for estimating ammonia (NH3) emissions in China using the bottom-up methods. However, there is still a lack of high-resolution gridded EFs of NH3 by crops in China, which are affected by climate, soil, and human management. Here, we established a data-driven approach for mapping crop-specific EFs of NH3 in China based on ground-based data and multiple geospatial data. We found that rice exhibited the highest EFs at 13.35 %, followed by wheat at 5.50 %, and maize at 5.15 %. This underscores the significance of utilizing EFs specific to each crop for predicting NH3 emission estimations. Furthermore, our results reveal substantial spatial variations in NH3 EFs across China, with notably higher values observed in South China for rice and elevated EFs in North China for wheat and maize. According to our model, the deep fertilization method emerges as the most effective method for reducing NH3 emissions, offering a remarkable 64 % reduction. Ongoing urbanization in China will lead to a rapid decline in the rural labor force in the coming years, which requires agricultural mechanization with less labor input. This shift in turn could support the implementation of deep fertilization techniques and reduce NH3 emissions by half in 2050. Our findings offer valuable insights for shaping the future trajectory of Chinese agriculture in overcoming agricultural NH3 loss.

Reduction of Gaseous Nitrogen Loss from Soil Applied with Beneficial Bacteria Under Different Levels of N

ABSTRACT Currently, there is an abundance of interest in the methods to reduce ammonia (NH3) volatilization and nitrous oxide (N2O) emissions from cultivated soils. Nitrogen use efficiency (NUE) of applied urea is decreased due to gaseous loss, which also lowers soil N (Nitrogen) content. The purpose of this study was to investigate the potential of microbial-based inoculants to decrease NH3 loss and N2O emissions under controlled conditions. Bacillus subtilis ;(UPMB10), and Bacillus tequilensis ;(UPMRB9) in combination with five different nitrogen (N) fertilizer levels 0%, 25%, 50%, 75%, and 100% were used in this study. Results showed that NH3 cumulative volatilization loss was greater in uninoculated soil treated with a full dose of fertilizer-N (507.27 mg/kg) compared with bacterial-inoculated soil (491.20 mg/kg and 500.71 mg/kg for UPMRB9 and UPMB10, respectively). Emission of N2O increased to a greater level (15.11 mg/kg for B0N100) in uninoculated soil compared to inoculated soil (14.65 mg/kg for UPMRB9N100 and 14.93 mg/kg for UPMB10N100-treated soil) and emission of N2O increases as N application increases. Initially, the emission of N2O was greater which decreased from the sixth day until it became zero. In B0N100-treated soil, emissions of N2O increased and after 30 days of incubation, the inoculated soil had a greater N concentration than the uninoculated soil. The total N loss from applied urea was higher in uninoculated soil than in inoculated soil. According to the findings, microbial inoculants have the potential to reduce the loss of N through NH3 volatilization and N2O emissions.

Estimating food nitrogen and phosphorus footprints and budgeting nitrogen and phosphorus flows of Rwanda's agricultural food system during 1961–2020

Nitrogen (N) and phosphorus (P) are limiting factors for crop production in Rwanda where food security is susceptible to inadequate agricultural techniques, especially fertilization. Understanding N and P footprints for food and their budgets under different fertilized scenarios may help to improve the nutrient use efficiency and crop yield in Rwanda, however, with little information available yet. Here, we estimated food N and P footprints and their budgets for agri-food system in Rwanda using adjusted N-P-Calculator model under fertilized, unfertilized and combined scenarios during 1961–2020. The total food N footprint per capita increased from 4.2, 3.8 and 6.4 (1960s) to 6.8, 4.9 and 9.9 kg N cap−1 yr−1 under combined, unfertilized and fertilized scenarios, respectively (2011−2020). The total food P footprint per capita increased from 0.19, 0.18 and 0.23 (1960s) to 0.31, 0.25 and 0.40 kg P cap−1 yr−1 under combined, unfertilized and fertilized scenarios, respectively (2011–2020). The total N input to croplands increased from 13.9 (1960s) to 37.0 kg N ha−1 yr−1 (2011–2020), while the total crop N uptake increased from 18.1 (1960s) to 32.5 kg N ha−1 yr−1 (2011–2020), resulting in N use efficiency decline from 99.1% (1960s) to 74.6% (2011–2020). Gaseous N losses of NH3, N2O, and NO increased from 0.9, 0.1 and 0.0 (1960s) to 7.5, 0.8 and 0.1 kg N ha−1 yr−1, respectively (2011–2020). The total P removal in harvested crops increased from 2.9 (1960s) to 5.1 kg P ha−1 yr−1 (2011–2020). The results revealed large room for crop yield expansion; and low N and P inputs are major agricultural production limitations. We suggest N and P fertilizer improvement by focusing on better management of organic animal manure and ensuring high biologically N fixed through crop rotation of legumes and cereals; lastly to increase in moderation the use of synthetic N and P fertilizers in Rwanda.

Controlled-release urea for use in sugarcane ratoons

Urea is the main solid N fertilizer used worldwide. Among its advantages are the high nutrient content, ease of handling and application, and low cost. Urea is subject to high losses through NH3 volatilization if surface-applied on soils. Therefore, ammonium nitrate is the preferred N source, especially in the ratoon cycles. Urea treated with the urease inhibitor NBPT and controlled-release fertilizers are options to replace ammonium nitrate. Controlled-release urea (CRU) is produced by coating the urea granules with resin or synthetic polymers so that the urea in the nucleus is not in contact with soil moisture. This study aimed to test CRU in sugarcane ratoons compared with ammonium nitrate (AN) and urea treated with urease inhibitor (UR-NBPT) at three rates: 60, 120 and 180 kg ha–1. Efficiency was also compared with two control treatments, the N control and the NPK control. Two field experiments were established and conducted in 2020 and 2021 in Sao Paulo state, Brazil. Sugarcane yield was evaluated in both experiments. N losses as NH3 volatilized were measured in the first experiment. All sources were equally efficient in promoting increases in sugarcane ratoon yield in both experiments. The relative yield obtained with N fertilizers and the control without N showed yield increases in the first experiment of 40, 54 and 68% for 60, 120 and 180 kg N ha–1 as AN, respectively; 29, 61 and 61% for 60, 120 and 180 kg N ha–1 as urea-NBPT, respectively; and 32, 62 and 67% for 60, 120 and 180 kg N ha–1 as CRU, respectively. Yields were higher in the second experiment, but increases in yield were lower compared to the first. Increases of 7, 10 and 16% for AN in three doses, 5, 12, 15% for UR-NBPT and 7, 9 and 14% for CRU were observed, respectively. N losses as NH3 volatilized were relatively low; CRU fertilizer showed good protection against NH3 losses by volatilization, protecting urea for about 30 days. This protection, however, did not affect yield. NH3 losses reached 13% of the N applied in the treatment with urea (about 16 kg N ha–1), 11% for Urea-NBPT (about 13 kg N ha–1) and 9% for CRU (about 11 kg N ha–1). Analyzing the results of both experiments CRU did not show an advantage in efficiency compared to AN and Urea-NBPT.

Mitigation of reactive nitrogen loss from arable soils through microbial inoculant application: A meta-analysis

Excessive N fertilizer application contributes to a surge in reactive N (Nr) emissions from agroecosystems, consequently threatening global ecosystems’ quality and security. Adding functional microorganisms to agricultural soils, namely microbial inoculants (MI), is a promising method for ensuring sustainable agriculture, but general assessment of microorganism-driven N losses and mediating factors (such as climate conditions, soil properties, and field management practices) remains unclear. Therefore, a comprehensive meta-analysis on the effect of MI addition on NH3 volatilization, N2O emissions, and N leaching in soil-crop systems was conducted by integrating 50 published articles (188 paired observations). The MI application significantly reduced N2O emissions and NH3 volatilization by 29.8% and 24.9%, respectively. The boosted regression tree model showed that the soil organic carbon (SOC) and soil pH significantly affected the efficacy of MI application on both NH3 and N2O loss mitigation. The effects of MI application on N leaching were not clear due to limited data points. Additionally, MI addition significantly increased the abundance of denitrification functional genes (nirK, nirS, and nosZ). In conclusion, MI application presented a high potential to reduce Nr from croplands, future adoption of MI techniques should consider the effects of soil properties and field practices on its efficacy in order to achieving sustainable N management in crop production systems.

The increasing risk of ammonia volatilization in farmland from the recovery product of magnesium-modified biochar after nitrogen and phosphorus adsorption

Many studies have shown that magnesium modified biochar (MgBC) can recover nutrients from wastewater and be applied as an excellent slow-release fertilizer in farmland. However, the recovery products (NP-loaden MgBC), represented by struvite or magnesium phosphate, have a high degree of self-alkalinity, which may significantly increase the ammonia (NH3) volatilization in farmland. In this study, the optimal adsorption parameters, self-alkaline regulation process and co-adsorption mechanism of MgBC for ammonium ion (NH4+) and phosphate ion (PO43−) were studied through batch experiments. A field experiment was conducted with three treatments, including local conventional fertilization (N1B0) and the application of 5 t·ha−1 or 10 t·ha−1 NP-loaden MgBC in combination with local conventional fertilization (N1B1 and N1B2, respectively), to determine the impact of NP-loaden MgBC on NH3 volatilization, surface water c(NH4+-N) and pH. The results indicated that the maximum NH4+ and PO43− synergistic recovery of MgBC under the optimal adsorption parameters (dosage of 0.6 g·L−1; initial NH4+ and PO43− concentrations of 120 and 60 mg·L−1 and pH of 8) were 59.96 and 98.60 mg·g−1, respectively. Self-regulating alkaline MgBC maintained pH suitable for struvite, and precipitation mechanism controlled the adsorption. The presence of NP-loaden MgBC raised the pH levels in surface water during the basal fertilization stage and increased c(NH4+-N) in surface water during the topdressing stages. This, in turn, led to a significant increase in NH3 volatilization loss during the entire rice-growing period, with N1B1 and N1B2 experiencing a 23.87 % and 48.91 % increase respectively, compared to N1B0. Therefore, it is imperative to take into account the adverse impact of NP-laden MgBC on NH3 loss in paddy fields when considering its application in future field studies.

Artefacts in Field Trial Research—Lateral Ammonia Fluxes Confound Fertiliser Plot Experiments

Agricultural ammonia (NH3) emissions can have serious environmental impacts, lower fertiliser nitrogen-use efficiencies, and cause economic losses. NH3 losses may not only occur directly from organic fertilisers such as biogas digestates when applied to crops, the crops themselves may also be a source of ammonia emissions. Wheat yields from 14 years of an organic small plot fertiliser trial fertilised with biogas digestate were analysed to determine if there was significant lateral N transfer between plots. A simple NH3 loss/gain model was developed to calculate possible N gains and losses via NH3 volatilisation from the applied digestate. This model was tested using NH3 volatilisation measurements. In addition, 15N isotope measurements of crop biomass were used to analyse plant N uptake. While digestate fertilisation increased wheat yields, yield patterns indicated that NH3 emissions from plots fertilised with biogas digestate affected yields in neighbouring unfertilised plots. Measurements of ammonia losses and gains in the field validated our modelling results, showing that 55% of digestate NH4+-N was volatilised. 15N isotope analysis indicated that crops took up as much as 30 kg ha−1 NH3-N volatilised from digestate, and that plots closer to fertilised plots took up more of this NH3-N than crops further away from fertilised plots. Our results imply that neither the results from the fertilised plots nor from the unfertilised plots are without bias. To avoid inadvertently introducing artefacts into fertiliser field trials, plot sizes need to be increased and treatments situated further apart.