Synthetic Nitrogen Fertilizers Research Articles

Green Manure for Sustainable Crop Production: A Review

Green manuring is an economical and eco-friendly scientific approach to achieve more resilient and sustainable food production for agricultural systems. Incorporation of green manure improves soil condition by increasing soil physical, chemical and biological properties such as organic matter, availability of nitrogen, phosphorus and potassium and also improves soil structure by preventing soil erosion, increasing water holding capacity etc. Green manure acts as a natural fertilizer, releasing nutrients into the soil as it decomposes and increases the nutrient content in the soil and shows positive effect on plant growth and development. Addition of green manure crops contribute to greater fixation of atmospheric nitrogen, and when decomposed, makes the nitrogen availability in the soil, reducing the need for synthetic nitrogen fertilizers in crops. Furthermore, it has a significant impact on several plant growth and yield parameters, resulting in increased agricultural productivity and ecosystem health.

Tracing the contribution and fate of synthetic nitrogen fertilizer in young apple orchard agrosystems

Excessive synthetic nitrogen (N) inputs in intensive orchard agrosystems of developing countries are a growing concern regarding their adverse impacts on fruit production and the environment. Quantifying the distribution and contribution of fertilizer N is essential for increasing N use efficiency and minimizing N loss in orchards. A 15N tracer experiment was performed in a young dwarf apple orchard over two growing seasons to determine the fertilizer N transformation and fate. Fertilizer N primarily contributed to 25 % to 75 % of soil nitrate in the top 60 cm, but the contribution to soil microbial biomass N and fixed ammonium was <8 %, with the contribution to plant N ranging from 9 % to 19 %. In most growth periods, soil nitrate and fixed ammonium contents derived from native soil with N fertilization were higher than those not receiving N fertilizer. The N use efficiency of plants was only 2.6 % and 4.9 % in the first and second seasons, respectively, in contrast to 56.6 % and 54.0 % of N recovered in soil. Meanwhile, N assimilated into microbial biomass accounted for 0.8 %, and the proportion fixed by clay minerals was 3.5 %–5.2 %. One season after N fertilization, the nitrate below the 1 m soil layers accounted for 4.6 % of the applied N fertilizer, and the proportion increased to 22.5 % after two seasons. The N loss rate via N2O emission was 0.4 % over two years. The application of N fertilizer facilitated indigenous soil N mineralization, and abiotic ammonium fixation more efficiently retained synthetic N than microbial immobilization. These findings provide new insight into orchard N cycling, and attention should be given to the improvement of soil N retention and turnover capacity regulated by soil microbial and abiotic processes, as well as the potential environmental impacts of additional soil N mineralization resulting from prolonged chemical N fertilization.

Nitrogen acquisition and retention pathways in sustainable perennial bioenergy grass cropping systems

AbstractPerennial tall grasses show promise as bioenergy crops due to high productivity and efficient nutrient use. Ongoing research on bioenergy grasses seeks to reduce their reliance on synthetic nitrogen (N) fertilizer, the manufacture of which relies on fossil fuel combustion. Excessive use of fertilizers also causes adverse environmental consequences and leads to the evolutionary loss of plant traits beneficial to sustainable N cycle. Notably, perennial tall grasses have exhibited the potential to maintain high biomass yield without the need for N fertilizer or causing soil N depletion. Perennial grasses can be adept at interacting with their microbial partners to facilitate N acquisition and retention via mechanisms such as biological N fixation and nitrification inhibition. These inherent N management traits should be preserved and optimized at the this early stage of bioenergy grass breeding programs. This review examines the impact of external N on bioenergy grass production and explores the potential of leveraging advantageous N‐cycling attributes of perennial tall grasses, laying groundwork for future management and research efforts. With minimized dependency on external N input, the cultivation of perennial energy grasses will pave the way toward more resilient agricultural systems and play a significant role in addressing key global energy and environmental challenges.

Global potential nitrogen recovery from anaerobic digestion of agricultural residues

Meeting the anticipated 50% increase in global food demand by 2050 requires a crucial reassessment of agricultural practices, particularly in terms of nitrogen fertilizers inputs. This study analyzes the technical potential of nitrogen recovery from livestock manure and crop residues, bringing attention to the often-overlooked resource of digestate derived from anaerobic digestion. Our analysis highlights the significant capacity of the anaerobic digestion process, yielding approximately 234 ± 5 million metric tons (Mt) of nitrogen annually, sourced 93% from livestock manure and 7% from crop residues. Additionally, we estimated that substituting synthetic nitrogen with nitrogen from anaerobic digestion has the potential to reduce greenhouse gas emissions by 70% (185 Mt CO2-eq yr−1). Lastly, 2.5 billion people could be sustained by crops grown using nitrogen from anaerobic digestion of manure and crop residues rather than synthetic nitrogen fertilizers. Although agricultural residues have double the technical potential of current synthetic nitrogen fertilizer production, 30% of croplands encounter difficulties in satisfying their nitrogen needs solely through crop residues and anaerobic digestion manure. This deficiency primarily results from inefficient reuse attributed to geographical mismatches between crop and livestock systems. This underscores the urgent need to reconnect livestock and cropping systems and facilitate the transport and reuse of manure in crop production. In conclusion, the mobilization of these large amounts of nitrogen from livestock manure and crop residues will require to overcome the nitrogen from anaerobic digestion green premium with incentives and subsidies.

Manure replacing synthetic fertilizer improves crop yield sustainability and reduces carbon footprint under winter wheat–summer maize cropping system

Manure replacing synthetic fertilizer is a viable practice to ensure crop yield and increase soil organic carbon (SOC), but its impact on greenhouse gas (GHG) emissions is inconsistent, thus remains its effect on CF unclear. In this study, a 7-year field experiment was conducted to assess the impact of replacing synthetic fertilizer with manure on crop productivity, SOC sequestration, GHG emissions and crop CF under winter wheat–summer maize cropping system. Five treatments were involved: synthetic nitrogen, phosphorus, and potassium fertilizer (NPK) and 25%, 50%, 75%, and 100% of manure replacing synthetic N (25%M, 50%M, 75%M, and 100%M). Compared with NPK treatment, 25%M and 50%M treatments maintained annual yield (winter wheat plus summer maize) and sustainable yield index (SYI), but 75%M and 100%M treatments significantly decreased annual yield, and 100%M treatment also significantly reduced annual SYI. The SOC content exhibited a significant increasing trend over years in all treatments. After 7 years, SOC storage in manure treatments increased by 3.06–11.82 Mg ha−1 relative to NPK treatment. Manure treatments reduced annual GHG emissions by 14%–60% over NPK treatment. The CF of the cropping system ranged from 0.16 to 0.39 kg CO2 eq kg−1 of grain without considering SOC sequestration, in which the CF of manure treatments lowered by 18%–58% relative to NPK treatment. When SOC sequestration was involved in, the CF varied from −0.39 to 0.37 kg CO2 eq kg−1 of grain, manure treatments significantly reduced the CF by 22%–208% over NPK treatment. It was concluded that replacing 50% of synthetic fertilizer with manure was a sound option for achieving high crop yield and SYI but low CF under the tested cropping system.

Carbon footprint of synthetic nitrogen under staple crops: Afirst cradle-to-grave analysis.

More than half of the world's population is nourished by crops fertilized with synthetic nitrogen (N) fertilizers. However, N fertilization is a major source of anthropogenic emissions, augmenting the carbon footprint (CF). To date, no global quantification of the CF induced by N fertilization of the main grain crops has been performed, and quantifications at the national scale have neglected the CO2 assimilated by plants. A first cradle-to-grave life cycle assessment was performed to quantify the CF of the N fertilizers' production, transportation, and application to the field and the uses of the produced biomass in livestock feed and human food, as well as biofuel production. We quantified the direct and indirect inventories emitted or sequestered by N fertilization of main grain crops: wheat, maize, and rice. Grain food produced with N fertilization had a net CF of 7.4 Gt CO2eq. in 2019 after excluding the assimilated C in plant biomass, which accounted for a quarter of the total CF. The cradle (fertilizer production and transportation), gate (fertilizer application, and soil and plant systems), and grave (feed, food, biofuel, and losses) stages contributed to the CF by 2%, 11%, and 87%, respectively. Although Asia was the top grain producer, North America contributed 38% of the CF due to the greatest CF of the grave stage (2.5 Gt CO2eq.). The CF of grain crops will increase to 21.2 Gt CO2eq. in 2100, driven by the rise in N fertilization to meet the growing food demand without actions to stop the decline in N use efficiency. To meet the targets of climate change, we introduced an ambitious mitigation strategy, including the improvement of N agronomic efficiency (6% average target for the three crops) and manufacturing technology, reducing food losses, and global conversion to healthy diets, whereby the CF can be reduced to 5.6 Gt CO2eq. in 2100.

Assessing the growth dynamics of alfalfa varieties (Medicago sativa cv. Bilensoy 80 and Nimet) response to varied carbon dioxide (CO2) concentrations

Rising atmospheric CO2 levels drive greenhouse effects, elevating temperatures, and diminishing water accessibility in semi-arid regions, affecting agriculture. Alfalfa contributes to climate change mitigation by sequestering carbon, enhancing soil fertility and carbon storage, reducing synthetic nitrogen fertilizer use, preventing soil erosion, supplying high-quality livestock feed, and serving as a bioenergy source. This research examined the effects of elevated CO2 levels in climate change scenarios (600, 800, and 1000 ppm, with control at 400 ppm) on two alfalfa varieties, Medicago sativa cv. Nimet and Bilensoy-80. The experiments were conducted in specialized Climate Change Simulation Greenhouses, allowing control of CO2, water, and temperature variables. Results revealed a positive relationship between higher CO2 concentrations and increased photosynthesis (P ≤ 0.001), promoting the plant growth leaf area (P ≤ 0.001), yields and both leaf (P ≤ 0.05) and stem dry biomass (P ≤ 0.001). At 1000 ppm CO2, a saturation point was reached, halting further photosynthesis. This down-regulation was linked to decreased intercellular CO2 levels, which expedited chlorophyll and breakdown and potentially induced leaf senescence. High CO2 levels led to greater biomass, as anticipated. However, total protein levels, a forage quality indicator, initially decreased with high CO2 concentrations (up to 1000 ppm) due to an inverse relationship with shoot yield. Surprisingly, the 1000 ppm CO2 concentration mitigated this protein reduction in both alfalfa varieties.

Nitrogen substitution practice improves soil quality of red soil (Ultisols) in South China by affecting soil properties and microbial community composition

Substituting synthetic nitrogen (N) fertilizer with organic amendments is considered an effective practice to improve soil quality. However, information on the effects of N substitution practices on soil quality in the red soil area in South China is still limited. In this study, therefore, four kinds of organic materials, including maize straw, cow manure, biochar and biogas residue, were applied to sweet maize farmland for six consecutive cropping seasons to substitute 20% synthetic N fertilizer in the Pearl River Delta Plain, which is a typical red soil area in South China. We compared the effects of different N substitution practices with conventional fertilization (CK) on the soil physical, chemical and biological properties and the microbial community structure. A minimum dataset method was utilized to calculate the soil quality index (SQI) under different treatments. The results demonstrated that the N substitution practice improved the SQI by 55%−70% compared to the CK in the red soil of South China by improving the soil physicochemical properties and biological characteristics. Meanwhile, the N substitution practice showed positive effects on changing the microbial community structure. Cow manure substitution showed the best effect due to the increased relative abundance of beneficial phyla in the soil microbiota, such as Proteobacteria, Chloroflexi and Ascomycota, and the decreased relative abundance of Basidiomycota. Finally, the structural equation model illustrated that the N substitution practice greatly improved the SQI in red soil by improving the soil bulk density, pH, β-glucosidase activity, urease activity and microbial community composition. Collectively, all four N substitution practices significantly improved soil quality, and cow manure substitution was the most effective way to improve soil microbial community composition and soil quality. This study provides a research basis for improving soil quality in the red soil region in South China and valuable information for the development of clean agricultural production in typical subtropical areas in East Asia.

Emerging nitrogen-fixing cyanobacteria for sustainable cotton cultivation

Amid growing environmental concerns and the imperative for sustainable agricultural practices, this study examines the potential of nitrogen-fixing cyanobacteria as biofertilizers, particularly in cotton cultivation. The reliance on synthetic nitrogen fertilizers (SNFs), prevalent in modern agriculture, poses significant environmental challenges, including greenhouse gas emissions and water system contamination. This research aims to shift this paradigm by exploring the capacity of cyanobacteria as a natural and sustainable alternative. Utilizing advanced metabarcoding methods to analyze the 16S rRNA gene, we conducted a comprehensive assessment of soil bacterial communities within cotton fields. This study focused on evaluating the diversity, structure, taxonomic composition, and potential functional characteristics of these communities. Emphasis was placed on the isolation of native N2-fixing cyanobacteria strains rom cotton soils, and their subsequent effects on cotton growth. Results from our study demonstrate significant plant growth-promoting (PGP) activities, measured as N2 fixation, production of Phytohormones, Fe solubilization and biofertilization potential of five isolated cyanobacterial strains, underscoring their efficacy in cotton. These findings suggest a viable pathway for replacing chemical-synthetic nitrogen fertilizers with natural, organic alternatives. The reintegration of these beneficial species into agricultural ecosystems can enhance crop growth while fostering a balanced microbial environment, thus contributing to the broader goals of global sustainable agriculture.

Annual consumption and types of synthetic nitrogen fertilizers: Ammonia emission indicators for mitigation strategies in the European Union

Anthropogenic ammonia (NH3) emissions are primarily derived from agricultural activities. NH3 emissions from synthetic nitrogen (N) fertilizers are associated with the annual consumption of various N fertilizers. In this study, the annual consumption of different types of synthetic N fertilizers in the EU countries, derived from the database of the International Fertilizer Association, was analyzed, and the implementation of mitigation measures for NH3 emissions at the national level was assessed. NH3 emissions were estimated using the emission factors of different N fertilizers in cool, temperate, and hot climates and low- and high-pH soils, as the European Environment Agency proposed. The results revealed that the annual consumption of various synthetic N fertilizers (average values from 2016 to 2020) varied markedly in different EU countries. France, Germany, Poland, Spain, and the United Kingdom had the largest annual consumption of synthetic N fertilizers. NH3 emissions from urea-based fertilizers are the highest in most EU countries. The type of synthetic N fertilizer consumed contributed to the annual NH3 emissions. For example, although the annual synthetic N fertilizer consumption in Germany was 38% and 41.5% higher than those in Spain and Italy, the annual NH3 emissions in Germany were 63% and 20% lower than those in Spain and Italy, respectively, due to the high proportion of urea-based fertilizers with the highest emission factor among the synthetic N fertilizers in Spain and Italy. Thus, mitigation strategies should be tailored to specific types of N fertilizers with high emission factors and proportions to minimize NH3 emissions. Since the NH3 emissions from urea-based fertilizers are the highest in the EU countries, especially in the top five countries, we recommend the addition of urease inhibitors to urea fertilizers as one strategy for mitigating NH3 emissions.

Sustainability analysis of irrigated and rainfed wheat production systems under varying levels of nitrogen fertilizer through coupling of emergy accounting and life cycle assessment

Most of the crop production systems have strived for improving crop productivity by increasing various resource inputs; especially water and synthetic nitrogen (N) fertilizer, without considering their environmental consequences. Yet, only few studies have evaluated the sustainability of cropping systems simultaneously using life cycle assessment (LCA) and emergy accounting (EMA) techniques. The former highlights pollutant emissions and environmental impacts, while the latter emphasizes resource consumption and system efficiency. In this three-year field study, the environmental impacts and sustainability of farming systems were estimated under rainfed and irrigated patterns at four N application rates in the Northwest China. Our result indicated that the irrigated pattern enhanced grain yield by 9%, while simultaneously increasing 8% of environmental impact and 12% of emergy input based on per hectare of wheat production. Almost similar results of environmental impact per kg basis of grain production and emergy sustainability index revealed that irrigation practice did not decrease the overall sustainability of a cropping system. Conversely, the higher N levels of 240 and 360 kg N ha−1 did not provide a proportionate yield return and were accompanied by increased environmental impacts of 20% and 69%, respectively on per kg grain production basis, when compared to an N dose of 120 kg N ha−1. Meanwhile, the gross unit emergy value revealed that the production efficiency under 120 kg N ha−1 was enhanced, in comparison with other N levels. Therefore, a moderate N dose of 120 kg N ha−1 under both irrigated and rainfed patterns is highly recommended for adoption due to its overall advantage in terms of yield returns, environmental impact and production efficiency.

Ammonia Retention in Biowaste via Low-Temperature-Plasma-Synthesized Nitrogen Oxyacids: Toward Sustainable Upcycling of Animal Waste.

Sustainable fertilizer production is a pressing challenge due to a growing human population. The manufacture of synthetic nitrogen fertilizer involves intensive emissions of greenhouse gases. The synthetic nitrogen that ends up in biowaste such as animal waste perturbs the nitrogen cycle through significant nitrogen losses in the form of ammonia volatilization, a major human health and environmental hazard. Low-temperature air-plasma treatment of animal waste holds promise for sustainable fertilizer production on farmlands by enabling nitrogen fixation via ionization, forming nitrogen oxyacids. Although the formation of nitrogen oxyacids in plasma treatment of water is well-established, the extent of nitrogen oxyanion enrichment in animal waste and its downstream effects on acidifying the waste remain elusive because many compounds found in complex biowaste media may interfere with absorbed NOx species. This work aims to establish that plasma treatment of dairy manure can suppress ammonia loss by volatilization via acidification of animal waste while enriching the waste in total nitrogen due to nitrogen retained in ammonia as well as adding nitrogen oxyacids by reacting NOx with the aqueous slurry. To this end, air-plasma effluent containing NOx is bubbled through dairy manure, which is then analyzed for changes in the nitrogen oxyanion content and pH. Increasing the plasma treatment time results in more acidic manure, reduced ammonium content in the downstream acid trap, and increased nitrogen oxyanion content, where the yield of nitrogen oxyanion from absorbed NOx species is approximately 100%. Increased plasma treatment also led to an increase in the total Kjeldahl nitrogen and the total nitrogen. These results indicate that plasma treatment of animal waste can significantly suppress ammonia pollution from animal husbandry facilities such as dairy farms while upcycling animal waste as a rich organic source of nitrogen.

Balancing Non‐CO2 GHG Emissions and Soil Carbon Change in U.S. Rice Paddies: A Retrospective Meta‐Analysis and Agricultural Modeling Study

AbstractU.S. rice paddies, critical for food security, are increasingly contributing to non‐CO2 greenhouse gas (GHG) emissions like methane (CH4) and nitrous oxide (N2O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO2 GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO2eq yr−1 in the 1960s to 8.9 ± 2.7 Tg CO2eq yr−1 in the 2010s. CH4, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO2eq yr−1 in the 2010s, alongside a notable rise in N2O emissions by 0.21 ± 0.03 Tg CO2eq yr−1. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO2eq yr−1) of the climate‐warming effects of soil non‐CO2 GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO2, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO2 GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO2eq ha−1 emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation.

Introduction of soybean into maize field reduces N2O emission intensity via optimizing nitrogen source utilization

The application of synthetic nitrogen (N) fertilizer has increased anthropogenic N2O emission in global croplands. Due to the advantage of biological nitrogen fixation (BNF), the introduction of legume may lessen N2O emission intensity (emission/yield) in cereal field. Yet, this speculation lacks strong evidences and the relevant mechanistic explanations. A two-year field study was conducted using static chamber method (15N isotope labeling in fertilizer) in the mono- and inter-cropping fields with soybean introduced in maize field in semiarid rainfed Loess Plateau. The results indicated that maize-soybean intercropping showed 13 % lower N2O emission intensity than monocropping, attributed to 14 % and 20 % lower annually N2O emissions in intercropped zone than that of sole maize and soybean zones respectively. Also, a 15 % higher grain yield was observed in intercropped maize relative to that in sole maize. Particularly, during the peak time of emission following N fertilization and BNF within growing season, soybean introduction reduced 25 % and 24 % of N2O emissions in intercropped zone than sole maize and soybean zone respectively. It also favored maize plant with an additional 17 % more fertilizer-derived N, 21 % less soil-derived N and 30 kg N ha−1 soybean transferred-N from BNF. The contributions of N fertilization, BNF and soil initial organic N to N2O production were lessened in intercropping. In this case, the capacity of substrates N transformation into N2O emissions was lowered. Critically, soybean introduction reduced soil ammonia oxidation (as evidenced from amoA AOA and AOB gene abundance) in intercrops’ rhizosphere, and increased soil nitrite reduction (nirS and nirK gene abundance) in maize rhizosphere, and improved soil N2O reduction to N2 (nosZ gene abundance) in soybean rhizosphere. Therefore, soybean introduction optimized N source use for lower N2O emission intensity, via reducing the transformation of substrate N into N2O, and modifying the expression of nitrification and denitrification functional genes.

A modelled quantification of reduced nitrogen fertiliser requirement and associated trade-offs from inclusion of legumes and fallows in wheat-based crop sequences

ContextGlobally there is a need to increase crop production and maintain soil fertility while reducing environmental impact. Intensive wheat production is dependent on synthetic nitrogen (N) fertilisers which represent ∼38% of total on-farm greenhouse gas emissions in Australia and contribute to N pollution. There are four major sources of N available for crop production 1) N mineralised from native soil organic matter (SOM) 2) N derived from biological fixation by legume-associated rhizobial bacteria 3) synthetic N fertiliser 4) N-rich manures, composts, biosolids and other organic wastes. Farmers can emphasise use of these different sources through their management. ObjectivesIn this study we use crop simulation to predict the minimum amount of N fertiliser required for semi-arid wheat crops to achieve economic yield (EY – defined as 80% of water limited potential yield, PYw) when grown in long-term (1991–2020) sequences and at different rotational intensities with either; grain legumes (GL, source 2), legume winter cover crops (CC, source 2) and winter fallow (WF, source 1) compared to continuous wheat (CW, source 3). Results and conclusionsLegume and fallow phases at 25–67% intensity (e.g. one out of four to two out of three crops) reduced the long-term mean fertiliser N application required to achieve EY. For every % area increase of GL and CC, the mean N applied to achieve EY was reduced by 1.3 kg N kg ha-1 (0.43–1.9 N kg ha-1). For every % area increase of WF the mean N applied to achieve EY was reduced by 1.1 kg N kg ha-1 (0.4–1.6 N kg ha-1). Global warming potential emissions from soil (CO2 and N2O) increased compared to CW when legume intensity increased in high rainfall environments with high SOM but decreased at increasing intensity in low rainfall environments with low SOM. Food energy production (kJ ha-1yr-1) was reduced relative to CW by inclusion of CC and WF and to a lesser extent GL in sequences due to reduced total grain production over the study period. However, protein yield increased as GL intensity increased relative to CW. The most profitable sequences over a 30-year period were CW, or GL at different intensities depending on environment. ImplicationsDiversification of wheat-based cropping systems with legumes reduces N fertiliser requirement, but depending on farming system context this benefit can trade off against production, profitability and environmental outcomes. Evaluation and exploitation of appropriate farming system contexts to achieve mutually beneficial outcomes is required to allow farmers and policy makers to make informed decisions on how to increase food production whilst minimising environmental impacts.

Costs and benefits of synthetic nitrogen for global cereal production in 2015 and in 2050 under contrasting scenarios

Cereals are the most important global staple crop and use more than half of global cropland and synthetic nitrogen (N) fertilizer. While this synthetic N may feed half of the current global population, it has led to a massive increase in reactive N loss to the environment, causing a suite of impacts, offsetting the benefits of N fertilizers for food security and agricultural economy. To address these complex issues, the NBCalCer model was developed to quantify the global effects of N input on crop yields, N budgets and environmental impacts and to assess the associated social benefits and costs. Three Shared Socioeconomic Pathway scenarios (SSPs) were considered with decreasing N agri-environmental ambitions, through contrasting climate and N policy ambitions: sustainability (SSP1H), middle-of-the-road (SSP2M) and fossil-fueled development (SSP5L). In the base year the contribution of synthetic N fertilizer to global cereal production was 44 %. Global modelled grain yield was projected to increase under all scenarios while the use of synthetic N fertilizer decreases under all scenarios except SSP5L. The total N surplus was projected to be reduced up to 20 % under SSP1H but to increase under SSP5L. The Benefit-Cost-Ratio (BCR) was calculated as the ratio between the market benefit of increased grain production by synthetic N and the summed cost of fertilizer purchase and the external cost of the N losses. In base year the BCR was well above one in all regions, but in 2050 under SSP1H and SSP5L decreased to below one in most regions. Given the concerns about food security, environmental quality and its interaction with biodiversity loss, human health and climate change, the new paradigm for global cereal production is producing sufficient food with minimum N pollution. Our results indicate that achieving this goal would require a massive change in global volume and distribution of synthetic N.

Carbon Farming: A Promising Approach to Climate Mitigation and Adaptation in India

This article addresses India's role in the reduction of GHG emissions, the impact of renewable energy and the application of solar energy. In response to the climatic challenges, India is meticulously stepping towards offsetting or the onset of carbon farming such as organic cultivation and solar energy interventions. Offset carbon farming area of 5. 387 Mha organic farming could sequester carbon annually of 6.567 mt, simultaneously; it has the advantage of reducing synthetic nitrogen fertilizer application doses ranging from a minimum of 0.27 mt and a maximum of 1.08 mt per hectare. Furthermore, solar energy can indirectly be used as SWH suitable for average family households contributing carbon credits of 771 kg-824 kg in addition to saving an annual electricity burden of around 1365 kWh to 1459 kWh and directly utilized for solar PV electricity generation of 1 MW will offset approximately 730 tons of CO2 emissions, which is equivalent to 33, 183 carbon-absorbing trees (22 kg of CO2 absorbed/ tree/year). Carbon farming has challenges encompassing economic, technological, policy, and knowledge-based barriers that require innovative solutions and concerted stakeholder efforts.

Long‐term fertilization regulates dissimilatory nitrate reduction processes by altering paddy soil organic carbon components

AbstractTo enhance rice yields, synthetic nitrogen (N) fertilizers are often applied in rice paddy fields. Under waterlogged conditions, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) are the main N transformation processes. However, the effects of long‐term fertilization on the dissimilatory nitrate reduction processes remain largely unclear. Here, we investigated rates of denitrification, anammox and DNRA and the abundance of bacterial and nitrate reduction‐related genes (16S rRNA, narG, nirK, nirS, nosZ and hzsB) in rice paddy fields under different fertilization regimes [i.e., non‐fertilization (CK), NPK fertilization (NPK) and NPK fertilization plus straw returning (NPKS)]. The rates of denitrification, anammox and DNRA in the CK treatment were 46.18, 0.35 and 1.29 nmoL N g−1 h−1, respectively, which were significantly (p &lt; .05) increased by 7.32%–27.78%, 2.45–4.12 folds and 1.01–13.23 folds by NPK and NPKS treatments. This was largely consistent with the increased bacterial and nitrate reduction‐related gene abundances in the NPK and NPKS treatments. In addition, NPKS also significantly increased the relative contribution of DNRA to the total nitrate reduction relative to NPK and CK treatments, indicating that NPKS was more beneficial to N retention in the paddy field. Changes in rates of dissimilatory nitrate reduction processes in response to NPK and NPKS treatments were correlated to variations of soil total N, ammonium contents, pH, soil organic carbon (SOC) contents and nitrate reduction‐related genes, among which SOC contents had the highest explanation. Specifically, fulvic‐like compounds, alkyl C and methoxyl and nitrogen‐alkyl C were the key components determining denitrification, anammox and DNRA rates, respectively. Overall, our study suggests that long‐term NPK and NPKS fertilization stimulate rates of dissimilatory nitrate reduction processes mainly by altering soil C components and NPKS is more effective in maintaining soil fertility in the paddy field.

Optimizing Renewable Ammonia Production for a Sustainable Fertilizer Supply Chain Transition.

Local renewable ammonia production using electrolytic hydrogen is an emerging approach to alleviate emissions attributed to synthetic nitrogen fertilizer production while also insulating against fluctuations in fertilizer prices and mitigating transportation costs and emissions. However, replacing ammonia currently produced using fossil fuels will not be immediate. To this end, we develop a supply chain transition model, which first optimizes the design and hourly operation of new renewable ammonia facilities to minimize production costs and then optimizes the annual installation timing, production scale, and location of these new renewable facilities along with ammonia transportation to meet county resolution demands. The objective is to augment and eventually replace conventional ammonia market imports in an economically competitive manner. We performed a case study for Minnesota's ammonia supply chain and found that a full transition to in-state renewable production by 2032 is optimal. This is incentivized by the U.S. federal government's clean hydrogen production credits. This transition results in 99 % reduction in carbon intensity along with stable supply costs below $475 per metric tonne. New renewable production facilities are an order of magnitude smaller than existing conventional plants. They use both wind and solar resources and operate dynamically to minimize expensive battery and hydrogen storage capacities.

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer