NH3 Volatilization Research Articles

Sustainability assessment on paddy-upland crop rotations by carbon, nitrogen and water footprint integrated analysis: A field scale investigation

Nutrients of carbon, nitrogen and water of farmland ecosystem are essential foundation to guarantee crop production, but also environmental flows associated greenhouse gas (GHG), reactive nitrogen (Nr) releases, and water consumption. Their flow characteristics serve as a crucial starting point for creating efficient management practices and mitigation measures. Therefore, the objectives of this study are to quantify the carbon footprint (CF), nitrogen footprint (NF), water footprint (WF), and comprehensive environmental footprint (ComF) of six paddy-upland rotation systems, including fallow-paddy rice (FA-PR), Chinese milk vetch-paddy rice (CMV-PR), wheat-paddy rice (WH-PR), rapeseed-paddy rice (RA-PR), green forage wheat-paddy rice (WF-PR), and vicia faba bean-paddy rice (FB-PR), as well as to analysis their relationships and define driving factors. Results showed that the lowest area-scaled CF of 3.74 t CO2-eq ha−1 were observed in the CMV-PR rotation, which were 41% lower than that for WH-PR (the highest CF, 9.13 t CO2-eq ha−1) when soil carbon change was taken into account. It is of importance that soil carbon sequestration in CMV-PR rotation could offset up to around 57% of its CF, while the WH-PR rotation only offset 25%. The RA-PR rotation had the highest area-scaled NF and WF, which was 1.8 and 1.9 times greater than those of the lowest rotation in FA-PR. In terms of comprehensive environmental effects, the six rotation systems showed the order of FA-PR < CMV-PR < FB-PR < RA-PR < WF-PR < WH-PR, with NH3 volatilization accounting 60.7%–66.7% and blue-green WF for 17.5%–26.6% of the total. Therefore, priority should be given to optimizing N fertilizer application and water consumption for paddy-upland rotation systems. The study also suggested that appropriate inter-annual adjustment of rotation system could contribute to achieving GHG mitigations and Nr losses.

Optimizing nitrogen and water management for sustainable greenhouse vegetable production with less greenhouse gas emissions

Intensive greenhouse vegetable production is considered a major source of greenhouse gas emissions and ammonia volatilization in China because the overuse of nitrogen (N) fertilizers is extremely common. Therefore, the emissions of nitrous oxide (N2O), carbon dioxide (CO2), and ammonia (NH3) from five different fertilizer treatments (conventional practice (CN) and four reduced N rate treatments (synthetic fertilizer, combined without (RN1) or with a nitrification inhibitor (3,4-dimethypyrazole phosphate, DMPP) (RN1 +DMPP), and a mixed application of synthetic and organic fertilizers, combined without (RN2) or with straw (RN2 +S))) were determined during a tomato and melon rotation. The results showed that the CN treatment had high total emissions of N2O (9.81 ± 0.81 kg N ha−1 yr−1) and CO2 (6.43 ± 0.75 kg C ha−1 season−1), which were 2.1–6.5 times and 1.2–1.91 times greater than those of other reduced N treatments, respectively. The annual direct N2O emission factor of the CN treatment was 0.94 %, which was higher than that of the reducing N treatments. The RN1, RN2 and RN2 +S treatments significantly (p < 0.05) decreased NH3 volatilization. The RN1 +DMPP treatment significantly (p < 0.05) increased NH3 volatilization in comparison with the RN1 treatment; however, it reduced the net global warming potentials (GWP) due to decreasing both N2O and CO2 emissions. Reducing the N application rate did not compromise vegetable yields in comparison with the CN treatment, but it significantly decreased the yield-scaled N2O emissions (p < 0.05). The combination of synthetic fertilizer and manure significantly (p < 0.05) increased N2O emissions relative to synthetic fertilizer alone. Compared to the other treatments, the RN1 +DMPP treatment significantly reduced the net GWP. Therefore, RN1 +DMPP is a better practice to reduce greenhouse gas emissions and simultaneously maintain crop yield in intensive vegetable production.

Modeling ammonia emissions and abatement potential from the rice-wheat rotation fields using the calibrated DNDC model: A case study in Shanghai, China

Abating ammonia (NH3) volatilization from intensive cropping system is of great importance for preventing the pollution of atmospheric environment and sustainable agriculture. Urea, a common nitrogen fertilizer, can convert to an unstable carbamate and further releases NH3 from the fields. However, few investigations of NH3 volatilization loss following fertilizer application to agricultural soils have been done using process-based models. In this study, a two-year field study was conducted to calibrate and evaluate the DeNitrification-DeComposition (DNDC) model for simulating NH3 volatilizations and crop production for the rice-wheat rotation system under four fertilizer regimes: control group without N fertilizer (CK), chemical fertilizer (CF), mixed application of inorganic and organic fertilizer (MF), and organic fertilizer (OF) treatments. The calibrated and modified DNDC performed effectively in simulating cumulative NH3 volatilization (coefficient of determination (R2) = 0.96 for rice and 0.92 for wheat field, relative deviation (RD) = −6.3% - 2.1% for rice and −22.5 to −4.6% for wheat) and grain yields for both crops (R2 = 0.94 for rice and 0.91 for wheat, RD of rice: 4.94%–9.59%; wheat: −1.84%–11.51%). The sensitivity analysis demonstrated that NH3 volatilization from rice-wheat rotation field was most sensitive to N application rate. Compared to CF and OF, MF treatments significantly mitigated NH3 volatilization and improved crop yield. Therefore, scenario simulation was conducted to confirm the optimal N application rate under MF. The results revealed that 250 kg N ha−1 and 112.5 kg N ha−1 in MF were recommended for rice- and wheat-growing, respectively. Compared to the current N fertilizer rate, the recommended rate saved 50 kg N ha−1 and mitigated NH3 volatilization loss by 28.31% from rice field and saved 37.5 kg N ha−1 and mitigated NH3 volatilization loss by 19.29% from wheat field. Overall, the calibrated DNDC model proved to be an effective tool to simulate NH3 volatilization from the rice-wheat rotation system and provides a promising fertilizer management strategy to decrease N input and mitigate NH3 volatilization.

The optimum economic nitrogen rate of blended controlled-release nitrogen fertilizer for rice in the Chanoyu watershed in the Yangtze River Delta, China.

The application of controlled-release nitrogen fertilizer (CRN) has become an important production method to achieve high crop yield and ecological safety. However, the rate of urea-blended CRN for rice is usually determined by conventional urea, and the actual rate is still unclear. A five-year field experiment was carried out in the Chaohu watershed in the Yangtze River Delta to study rice yield, N fertilizer utilization efficiency (NUE), ammonia (NH3) volatilization and economic benefit under the four urea-blended CRN treatments with a 4:3:3 ratio applied at one time (60, 120, 180, 240 kg/hm2, CRN60, CRN120, CRN180, CRN240), four conventional N fertilizer treatments (N60, N120, N180, N240) and a control without N fertilizer (N0). The results showed that the N released from the blended CRNs could well satisfy the N demand of rice growth. Similar to the conventional N fertilizer treatments, a quadratic equation was used to model the relationship between rice yield and N rate under the blended CRN treatments. The blended CRN treatments increased rice yield by 0.9-8.2% and NUE by 6.9-14.8%, respectively, compared with the conventional N fertilizer treatments at the same N application rate. The increase in NUE in response to applied blended CRN was related to the reduction in NH3 volatilization. Based on the quadratic equation, the five-year average NUE under the blended CRN treatment was 42.0% when rice yield reached the maximum, which was 28.9% higher than that under the conventional N fertilizer treatment. Among all treatments, CRN180 had the highest yield and net benefit in 2019. Considering the yield output, environmental loss, labor and fertilizer costs, the optimum economic N rate under the blended CRN treatment in the Chaohu watershed was 180-214 kg/hm2, compared with 212-278 kg/hm2 under the conventional N fertilizer treatment. The findings suggest that blended CRN improved rice yield, NUE and economic income while decreasing NH3 volatilization and negative environmental outcomes.

Change in maize yield, N use efficiencies and climatic warming potential after urea combined with Nitrapyrin and NBPT during the growing season in a black soil

Increasing nitrogen (N) utilization and reducing N losses are a globally accepted strategy for N fertilizer application. However, little information has been reported on the fate of N when urea (U) and nitrification and/or urease inhibitors are used in black soils. Therefore, a two-year field experiment was conducted with three N fertilizer application treatments, including urea-only, urea combined with nitrification inhibitor (U+NI), urea combined with NI and urease inhibitor (UI) treatments. Maize (Zea mays L.) yield, N use efficiency, gas emissions, global warming potential (GWP), and apparent N loss were determined. Compared to the other treatments, the U+NI+UI treatment had the significantly (P < 0.05) highest maize yield (11.2 t ha-1), N recovery efficiency (44.5%), agronomic N efficiency (28.7 kg kg-1) and N partial factor productivity (75.8 kg kg-1). Moreover, the U+NI+UI treatment significantly (P < 0.05) reduced the peak of Ammonia (NH3) volatilization and nitrous oxide (N2O) emissions, cumulative NH3 volatilization and N2O emissions, and apparent N loss compared to the U treatment. Although there was no significant difference in cumulative N2O emissions between the U+NI+UI and U+NI treatments, the U+NI+UI treatment significantly (P < 0.05) reduced cumulative NH3 volatilization by 55.3%, GWP by 16.2%, and apparent N loss by 28.2% compared to the U+NI treatment. Overall, the combination of urea with urease and inhibitors is a good practice to improve maize yield and N use efficiency while reducing environmental impacts in black soil.

Ammonia volatilization, greenhouse gas emissions and microbiological mechanisms following the application of nitrogen fertilizers in a saline-alkali paddy ecosystem

The application of nitrogen (N) fertilizer can promote rice yield, but is accompanied by considerable quantities of ammonia (NH3) volatilization and greenhouse gas (GHG) emissions. The effect of N-fertilization to these gas emissions in saline-alkali paddy ecosystems is unclear. A 137-day mesocosm-scale experiment was carried out to clarify the effect of different N-fertilizer application strategies on NH3 volatilization and GHG emissions in saline-alkali paddy ecosystems and to determine the microbiological mechanisms. Five N-fertilizer treatments consisting of control without N-fertilizer (CK), urea (U), urea with urease-nitrification inhibitors (UI), organic–inorganic compound fertilizer (OCF) and carbon-based slow-release fertilizer (CSF) were established. During the entire rice-growing season, the cumulative NH3 emissions of UI, OCF and CSF treatments were 22.60–25.55 % significantly (p < 0.05) higher than U, respectively. The cumulative methane emissions in all N-fertilizer treatments were decreased by 9.23–28.24 % compared with CK. The cumulative carbon dioxide emissions were U > CSF > OCF > CK > UI, and the cumulative nitrous oxide (N2O) emissions were U > CSF > UI > CK > OCF. The global warming potential of UI was 5.39–32.35 % lower than all the other treatments. Compared with the other N-fertilizer treatments, the relative abundance of N-related functional bacteria (e.g., Sphingomonas and Alphaproteobacteria) in OCF treatment was increased, and the (nirS + nirK)/nosZ ratio was reduced, thereby decreasing the N2O emission. Overall, U is a better choice for controlling NH3 volatilization in saline-alkali paddy ecosystems, whereas UI and OCF are more beneficial for reducing GHG emissions.

Reutilizar purines de tambo como oportunidad para reciclar nitrógeno y reducir su impacto ambiental

Dairy cattle slurry (liquid mixture of manure and water from the milking operation) can be reused for agricultural production in replacement for synthetic fertilizers. However, its high nitrogen (N) concentration could stimulate the volatilization of ammonia (NH3) and nitrous oxide (N2O) emission, with consequences for global warming. Our objectives were: to quantify NH3 and N2O loss in maize fertilized with surface-applied dairy cattle slurry or urea, and to relate N2O emission with soil ammonium, nitrate and water contents. We performed a manipulative field experiment where we measured both gaseous losses during an agricultural campaign. Slurry enhanced NH3 volatilization the day after the application (2.7±0.25 vs. 1.1±0.25 and 0.6±0.25 kg N-NH3.ha-1.day-1 for slurry, urea and the control, respectively) and direct N2O emission during three days after the application (75±13 vs. 28±5 y 26±6 µg N-N2O.m-2.h-1 for slurry, urea and the control, respectively). Four days after application, volatilization was higher with urea and N2O emissions were similar between treatments. The loss of NH3 accumulated throughout the maize growing season was higher for urea than for slurry, and the accumulated N2O emission was similar for both fertilizers. Nitrous oxide emissions were related to soil water content, initially introduced with slurry and then with rainfall. The loss of NH3 + N2O from the fertilizers after subtracting that of the control, was higher after the application of urea than slurry (10.8±1.2 and 3.1±0.7 kg N/ha or 0.53±0.06 and 0.18±0.04 kg N/t MS), and maize yield was similar for both fertilization treatments (19.0±0.7 t MS/ha). These results show that fertilization with dairy cattle slurry is a promising practice because it has a lower environmental footprint compared to synthetic fertilizers.

Exploring a sustainable rice-cropping system to balance grain yield, environmental footprint and economic benefits in the middle and lower reaches of the Yangtze River in China

Environmental degradation and resource scarcity are serious challenges faced by global rice production. Although rice production is crucial to ensure global food security, it is also one of the principal sources of greenhouse gas (GHG) and reactive nitrogen (Nr) emissions. Exploring rice-cropping systems with a low environmental footprint and high grain yield and economic benefits is a crucial strategy to improve the sustainability of rice production. Here, life cycle assessment was used to compare the performance of middle-season rice (MR), double-season rice (DR) and ratoon rice systems (RR) based on farmer-reported data in the middle and lower reaches of the Yangtze River of China. The average annual grain yields of DR, MR, and RR were 13.68, 8.96 and 11.97 t ha−1, respectively. Although RR produced 12.5% lower grain yield, it had 41.2% lower global warming potential (GWP) and 33.8% smaller eutrophication potential (EP) than DR, which resulted in lower greenhouse gas intensity (GHGI) and reactive nitrogen intensity (NrI). The lower GWP and EP in RR were mainly attributed to lower agricultural inputs, smaller CH4 and N2O emissions and less Nr losses. Compared with MR, RR had higher GWP and EP, but significantly higher grain yield (33.6%) in RR contributed to lower GHGI and similar NrI. In all three cropping systems, CH4 emissions and NH3 volatilization had the highest contributions to GWP and EP, respectively. Compared with the other two cropping systems, RR exhibited the highest net economic income (NEI), benefit-cost ratio and eco-efficiency. Overall, our results suggested that RR is a sustainable rice-cropping system that can coordinate grain yield, environmental footprint and economic benefits.

Side-Deep Fertilization Stabilizes Double-Cropping Rice Yield, Increases N and P Utilization, and Reduces N and P Losses

(1) Background: the broadcast is an outdated fertilization method with a low fertilizer-utilization rate and environmental problems, which seriously restricts the development of agriculture. (2) Methods: Under a machine-transplanted rice with side-deep fertilization (MRSF) mode, five treatments were applied: 0 cm (D0), 5 cm (D5), 7.5 cm (D7.5), and 10 cm (D10), comprising four different depths of fertilization, and no fertilization (CK). The yield, the accumulation of N and P in the straw and in grains of rice, concentrations of N and P in the surface water, ammonia (NH3) volatilization, and soil nutrients were measured in rice fields. (3) Results: In rice yields, compared with the D0 treatment, only the D7.5 treatment significantly increased by 7.84% in late rice, while the other treatments showed no significant difference between early and late rice. The N- and P-use efficiency of D10 increased by 5.30–24.73% and 0.84–17.75%, respectively, compared with the D0-D7.5 treatments. In surface water, compared with the D0 treatment, D5, D7.5, and D10, the total N (TN), total P (TP) concentration, and NH3 volatilization decreased by 10.24–60.76%, 16.30–31.01%, and 34.78–86.08%, respectively; the D10 treatment had the best inhibition effect on the TN, TP concentration, and NH3 volatilization, which were 58.48–60.76%, 22.04–31.01%, and 77.21–86.08%, respectively. (4) Conclusions: The optimized depth for side-deep fertilization was 10 cm. We would like to emphasize the impact of the paddy on various deep fertilizations and provide an important reference for developing precise fertilization in rice fields in this area.

A dynamic ammonia emission model and the online coupling with WRF–Chem (WRF–SoilN–Chem v1.0): development and regional evaluation in China

Abstract. The volatilization of ammonia (NH3) from fertilizer application and livestock wastes is an overwhelmingly important pathway of nitrogen losses in agricultural ecosystems and constitutes the largest source of atmospheric NH3. The volatilization of NH3 highly depends on environmental and meteorological conditions, however, this phenomenon is poorly described in current emission inventory and atmospheric models. Here, we develop a dynamic NH3 emission model capable of calculating the NH3 emission rate interactively with temporal- and spatial-varying meteorological and soil conditions. The NH3 flux parameterization relies on several meteorological factors and anthropogenic activity including fertilizer application, livestock waste, traffic, residential, and industrial sectors. The model is then embedded into a regional WRF–Chem model and is evaluated against field measurements of NH3 concentrations, emission flux, and satellite retrievals of column loading. The evaluation shows a substantial improvement in the model performance of NH3 flux and ambient concentration in China. The model represents the spatial and temporal variations of ambient NH3 concentration well, indicating the highest emission in the North China Plain (NCP) and Sichuan Basin, especially during summertime. Compared with normal simulations using fixed emission inventory input, this model features superior capability in simulating NH3 emission flux and concentration during drastic weather changes like frontal activities and precipitation. Such advances in emission quantification also improve the model performance of secondary inorganic aerosol on synoptic scales. While more laboratory and field measurements are still needed for better parameterization of NH3 volatilization, the seamless coupling of soil emission with meteorology provides a better understanding of NH3 emission evolution and its contribution to atmospheric chemistry.

How much can changes in the agro-food system reduce agricultural nitrogen losses to the environment? Example of a temperate-Mediterranean gradient

Ammonia (NH3) volatilization, nitrous oxide (N2O) emissions, and nitrate (NO3−) leaching from agriculture cause severe environmental hazards. Research studies and mitigation strategies have mostly focused on one of these nitrogen (N) losses at a time, often without an integrated view of the agro-food system. Yet, at the regional scale, N2O, NH3, and NO3− loss patterns reflect the structure of the whole agro-food system. Here, we analyzed at the resolution of NUTS2 administrative European Union (EU) regions, N fluxes through the agro-food systems of a Temperate-Mediterranean gradient (France, Spain, and Portugal) experiencing contrasting climate and soil conditions. We assessed the atmospheric and hydrological N emissions from soils and livestock systems. Expressed per ha agricultural land, NH3 volatilization varied in the range 6.2–44.4 kg N ha−1 yr−1, N2O emission and NO3 leaching 0.3–4.9 kg N ha−1 yr−1 and 5.4–154 kg N ha−1 yr−1 respectively. Overall, lowest N2O emission was found in the Mediterranean regions, where NO3− leaching was greater. NH3 volatilization in both temperate and Mediterranean regions roughly follows the distribution of livestock density. We showed that these losses are also closely correlated with the level of fertilization intensity and agriculture system specialization into either stockless crop farming or intensive livestock farming in each region. Moreover, we explored two possible future scenarios at the 2050 horizon: (1) a scenario based on the prescriptions of the EU-Farm-to-Fork (F2F) strategy, with 25% of organic farming, 10% of land set aside for biodiversity, 20% reduction in N fertilizers, and no diet change; and (2) a hypothetical agro-ecological (AE) scenario with generalized organic farming, reconnection of crop and livestock farming, and a healthier human diet with an increase in the share of vegetal protein to 65% (i.e., the Mediterranean diet). Results showed that the AE scenario, owing to its profound reconfiguration of the entire agro-food system would have the potential for much greater reductions in NH3, N2O, and NO3− emissions, namely, 60–81% reduction, while the F2F scenario would only reach 24–35% reduction of N losses.

Greenhouse gas emissions and ammonia loss of maize fertigation with a centre pivot system in the North China Plain

AbstractWhether sprinkler fertigation stimulates greenhouse gas emissions and ammonia loss is an indispensable consideration for nitrogen management. To assess the effect of sprinkler fertigation on N2O, CH4, CO2 and NH3 emissions, three N recommendation methods for summer maize, including the local empirical value, mineral nitrogen method and modified mineral nitrogen method, and three topdressing methods, including no topdressing, one topdressing and two topdressings following intermittent rainfall events, were tested in the 2020 and 2021 seasons. Surface irrigation with fertilizer broadcasting was used as the control treatment. The results indicated that nitrogen topdressing and rainfall promoted soil N2O, CO2 and NH3 emissions but had no obvious effect on CH4 emissions. The increasing nitrogen application rate increased gaseous nitrogen losses of N2O and NH3. Sprinkler fertigation with the modified mineral nitrogen method and two topdressings obtained the greatest yield and nitrogen use efficiency. Compared to the control treatment, the yield and nitrogen use efficiency in the sprinkler fertigation treatments was maximally increased by 20%, and the cumulative NH3 volatilization losses and gaseous nitrogen loss rate were both reduced by 16%, while the cumulative N2O emissions increased by 4%. No significant difference in global warming potential was obtained among all treatments.

Effects of optimized nitrogen fertilizer management on the yield, nitrogen uptake, and ammonia volatilization of direct-seeded rice.

Direct-seeded rice has been developed rapidly because of labor savings. Changes in rice cultivation methods put forward new requirements for nitrogen (N) fertilizer management practices. Field experiments with five different fertilizer ratios of basal, tillering and panicle fertilizer, namely N1 (10:0:0), N2 (6:2:2), N3 (4:3:3), N4 (2:4:4) and N5 (0:5:5), were conducted to investigate the effects of different N fertilizer management practices on yield formation, N uptakes, and ammonia (NH3 ) volatilization from paddy fields in direct-seeded rice. The results showed that the N4 treatment improved grain yield by 5.1% while decreasing NH3 volatilization by 20.4% compared with that of conventional fertilizer treatment (N2). The panicle number per unit area was the key factor to determine the yield of direct-seeded rice (72%). Excessive N application of basal fertilizer (N1) reduced seedling emergence, N use efficiency, and yield by 45.3%, 160.6%, and 6.9% respectively and increased NH3 volatilization by 28.1% compared with that of the N4 treatment. Removal of basal N fertilizer (N5) N reduced spike number and yield by 13.0% and 6.9% respectively, minimizing NH3 volatilization while affecting the construction of high-yielding populations compared with that of the N4 treatment. Optimized N fertilizer management achieved delayed senescence (maintenance of higher leaf Soil Plant Analysis Development meter values in late reproduction), higher canopy photoassimilation (suitable leaf area), higher N fertilizer use efficiency, and less N loss (lower cumulative NH3 volatilization). © 2023 Society of Chemical Industry.

Unraveling Binding Mechanism and Stability of Urease Inhibitors: A QM/MM MD Study

Soil bacteria can produce urease, which catalyzes the hydrolysis of urea to ammonia (NH3) and carbamate. A variety of urease inhibitors have been proposed to reduce NH3 volatilization by interfering with the urease activity. We report a quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) study on the mechanism employed for the inhibition of urease by three representative competitive inhibitors; namely, acetohydroxamic acid (AHA), hydroxyurea (HU), and N-(n-butyl)phosphorictriamide (NBPTO). The possible connections between the structural and thermodynamical properties and the experimentally observed inhibition efficiency were evaluated and characterized. We demonstrate that the binding affinity decreases in the order NBPTO >> AHA > HU in terms of the computed activation and reaction free energies. This trend also indicates that NBPTO shows the highest inhibitory activity and the lowest IC50 value of 2.1 nM, followed by AHA (42 μM) and HU (100 μM). It was also found that the X=O moiety (X = carbon or phosphorous) plays a crucial role in the inhibitor binding process. These findings not only elucidate why the potent urease inhibitors are effective but also have implications for the design of new inhibitors.

Effects of Long-Term Organic–Inorganic Nitrogen Application on Maize Yield and Nitrogen-Containing Gas Emission

A sustainable model of combined organic–inorganic fertilizer application for high maize yields and environmental health is important for food security. The short-term combined application of organic and inorganic fertilizers can improve crop yields; however, the effect of different proportions of organic and inorganic fertilizers on the maize yield and nitrogen gas emissions in a long time series has not been reported. In this study, field experiments and DeNitrification-DeComposition (DNDC) model simulations were used to study the long-term effects of substituting inorganic fertilizers with organic fertilizers on crop yields and nitrogen-containing gas emissions. Six treatments were included: no nitrogen (CK); urea (U1); and 25%, 50%, 75%, and 100% of the urea N substituted by organic fertilizers (U3O1, U1O1, U1O3, and O1, respectively). The DNDC model was calibrated using the field data from the U1 treatment from 2018 to 2020 and was validated for the other treatments. The results showed that this model could effectively simulate crop yields (e.g., nRMSE &lt; 5%), soil NH3 volatilization, and N2O emissions (nRMSE &lt; 25%). In addition, long-term (26 years) simulation studies found that the U1O1 treatment could considerably increase maize yields and ensure yield stability, which was 15.69–55.31% higher than that of the U1 treatment. The N2O, NH3, and NO emissions were in the descending order of U1 &gt; U3O1 &gt; O1 &gt; U1O3 &gt; U1O1, and the total nitrogen-containing gas emissions from the U1O1 treatment decreased by 53.72% compared with the U1 treatment (26 years). Overall, substituting 50% of inorganic nitrogen with organic nitrogen could maintain the high yield of maize and reduce emissions of nitrogen-containing gases, constituting a good mode for the combined application of organic–inorganic nitrogen in this area.

The Effect of Deep Placement of Basal Nitrogen Fertilizer on Gaseous Nitrogen Losses and Nitrogen Use Efficiency of Paddy Fields under Water-Saving Irrigation in Northeast China

As a widely implemented irrigation regime for paddy fields, water-saving irrigation (WSI) is capable of ensuring water resource security and improving nitrogen use efficiency (NUE). Higher gaseous nitrogen losses (GNL) lead to a low recovery rate of basal nitrogen, and this is the primary reason that restricts further improvements in the NUE under WSI. The deep placement of nitrogen fertilizer (DPN) is considered an efficient agricultural management measure to reduce GNL. However, the effects of WSI combined with the deep placement of basal nitrogen fertilizer on NUE, GNL, and rice yield in paddy fields remain largely unknown. In this study, a 2-year field experiment was conducted to measure GNL (N2O emissions and NH3 volatilization), NUE, and rice yield. Four treatments were utilized: (i) conventional flooding irrigation + broadcast of nitrogen fertilizer (110 kg N hm−2, CFN); (ii) water-saving irrigation + deep placement of basal nitrogen fertilizer (110 kg N hm−2, WSN); (iii) water-saving irrigation + deep placement of basal nitrogen fertilizer (99 kg N hm−2, WSN1); (iv) water-saving irrigation + deep placement of basal nitrogen fertilizer (88 kg N hm−2, WSN2). The results showed that the GNL in paddy fields under treatment ranged from 5.29 to 10.67 kg hm−2. Deep placement of basal nitrogen fertilizer mitigated the GNL of the paddy fields under WSI. The GNL of CFN was significantly higher than those of WSN1 and WSN2 by 26.9% and 54.0% in 2021 and 14.4% and 23.3% in 2022, respectively (p &lt; 0.05). Under WSI, the deep placement of basal nitrogen fertilizer reduced the GNL primarily via the reduction of NH3 volatilization. NH3-N of CFN was higher than those treatments under WSI. The rice yield of CFN was significantly lower than those of WSN and WSN1 by 22.4% and 21.6% in 2021 and 4.6% and 1.5% in 2022, respectively. (p &lt; 0.05). Moreover, the NUE of each treatment under WSI was higher than that of CFN. These changes exhibited similar trends in 2021 and 2022. These results demonstrated that deep placement of basal nitrogen fertilizer is an effective practice to ensure food and environmental security under WSI.

Tofu by-product soy whey substitutes urea: Reduced ammonia volatilization, enhanced soil fertility and improved fruit quality in cherry tomato production

Soy whey is an abundant, nutrient-rich and safe wastewater produced in tofu processing, so it is necessary to valorize it instead of discarding it as sewage. Whether soy whey can be used as a fertilizer substitute for agricultural production is unclear. In this study, the effects of soy whey serving as a nitrogen source to substitute urea on soil NH3 volatilization, dissolved organic matter (DOM) components and cherry tomato qualities were investigated by soil column experiment. Results showed that the soil NH4+-N concentrations and pH values of the 50% soy whey fertilizer combined with 50% urea (50%-SW) and 100% soy whey fertilizer (100%-SW) treatments were lower than those of 100% urea treatment (CKU). Compared with CKU, 50%-SW and 100%-SW treatments increased the abundance of ammonia oxidizing bacteria (AOB) by 6.52–100.89%, protease activity by 66.22–83.78%, the contents of total organic carbon (TOC) by 16.97–35.64%, humification index (HIX) of soil DOM by 13.57–17.99%, and average weight per fruit of cherry tomato by 13.46–18.56%, respectively. Moreover, soy whey as liquid organic fertilizer reduced the soil NH3 volatilization by 18.65–25.27% and the fertilization cost by 25.94–51.87% compared with CKU. This study provides a promising option with economic and environmental benefits for soy whey utilization and cherry tomato production, which contributes to the win-win effectiveness of sustainable production for both the soy products industry and agriculture.

The effects of organic fertilizer on loss risk of nitrogen and phosphorus in paddy ponded water.

There is a great challenge globally for both achieving high crop yields via fertilization and minimizing environmental pollution from nutrient losses. Organic fertilizer (OF) application has been extensively reported to effectively improve arable soil fertility and mitigate nutrient losses. However, few studies are available that accurately quantified the substitution rates of OF for chemical fertilizers (CF) that affect rice yield, the nitrogen/phosphorus in ponded water, and its loss potential in paddy field. Here, an experiment with 5 levels of CF nitrogen substituted by OF nitrogen was performed during the early stage of rice growth in paddy field of Southern China. The results showed that the first 6days and 3days following fertilization generally were risky period for N losses and for P losses, respectively, due to corresponding high concentrations in ponded water. Compared to CF treatment, over 30% of OF substitution rates significantly decreased the daily mean TN concentrations by 24.5-32.4%, while TP concentrations unaffected and rice yield maintained comparative levels. OF substitution also improved acidic paddy soils, with the increment of 0.33-0.90 unit for ponded water pH compared to CF treatment. Conclusively, the 30-40% of CF substituted by OF based on N amounts can be considered an ecological fertilization practice for rice production to mitigate environmental pollution due to lower N losses and without significant effect of grain yield. However, the attention also must be paid concerning the rise of environmental pollution risk from NH3 volatilization and P runoff after long-term OF application.

Crop-specific ammonia volatilization rates and key influencing factors in the upland of China - A data synthesis

Ammonia (NH3) is an important alkaline reactive nitrogen (Nr) species which is involved in global nitrogen (N) biogeochemical cycling, but which has negative impacts on the environment and human health. In order to better understand and control the NH3 loss potential in soil-upland crop systems in China, an integrated data analysis including 1302 observations from 236 published articles between 1980 and 2021 was conducted. The typical NH3 volatilization rate (AVR) and the main factors influencing AVR in the major Chinese upland crops (maize, wheat, openfield vegetables and greenhouse vegetables and others) were estimated and analyzed. The mean AVR for maize, wheat, openfield vegetables and greenhouse vegetables were 7.8%, 5.3%, 8.4% and 1.8%. The most important influencing factors were fertilizer placement, meteorological conditions (especially temperature and rainfall) and soil properties (especially SOM). Subsurface N application produced a significantly lower AVR compared to surface application. High N recovery efficiency and N agronomic efficiency were generally associated with low AVRs. In conclusion, high N application rates, inefficient application methods and the use of loss-prone N fertilizer types are the main factors responsible for high AVRs in major Chinese croplands.

Reducing options of ammonia volatilization and improving nitrogen use efficiency via organic and inorganic amendments in wheat (Triticum aestivum L.).

This study investigates the effect of organic and inorganic supplements on the reduction of ammonia (NH3) volatilization, improvement in nitrogen use efficiency (NUE), and wheat yield. A field experiment was conducted following a randomized block design with 10 treatments i.e., T1-without nitrogen (control), T2-recommended dose of nitrogen (RDN), T3-(N-(n-butyl) thiophosphoric triamide) (NBPT @ 0.5% w/w of RDN), T4-hydroquinone (HQ @ 0.3% w/w of RDN), T5-calcium carbide (CaC2 @ 1% w/w of RDN), T6-vesicular arbuscular mycorrhiza (VAM @ 10 kg ha-1), T7-(azotobacter @ 50 g kg-1 seeds), T8-(garlic powder @ 0.8% w/w of RDN), T9-(linseed oil @ 0.06% w/w of RDN), T10-(pongamia oil @ 0.06% w/w of RDN). The highest NH3 volatilization losses were observed in T2 at about 20.4 kg ha-1 per season. Significant reduction in NH3 volatilization losses were observed in T3 by 40%, T4 by 27%, and T8 by 17% when compared to the control treatment. Soil urease activity was found to be decreased in plots receiving amendments, T3, T4, and T5. The highest grain yield was observed in the T7 treated plot with 5.09 t ha-1, and straw yield of 9.44 t ha-1 in T4. The shifting towards organic amendments is a feasible option to reduce NH3 volatilization from wheat cultivation and improves NUE.