Synthetic Nitrogen Fertilizers Research Articles

Genetic remodeling of soil diazotrophs enables partial replacement of synthetic nitrogen fertilizer with biological nitrogen fixation in maize.

Increasing biological nitrogen (N) fixation (BNF) in maize production could reduce the environmental impacts of N fertilizer use, but reactive N in the rhizosphere of maize limits the BNF process. Using non-transgenic methods, we developed gene-edited strains of Klebsiella variicola (Kv137-2253) and Kosakonia sacchari (Ks6-5687) bacteria optimized for root-associated BNF and ammonium excretion in N-rich conditions. The aim of this research was to elucidate the mechanism of action of these strains. We present evidence from in vitro, in planta and field experiments that confirms that our genetic remodeling strategy derepresses BNF activity in N-rich systems and increases ammonium excretion by orders of magnitude above the respective wildtype strains. BNF is demonstrated in controlled environments by the transfer of labeled 15N2 gas from the rhizosphere to the chlorophyll of inoculated maize plants. This was corroborated in several 15N isotope tracer field experiments where inoculation with the formulated, commercial-grade product derived from the gene-edited strains (PIVOT BIO PROVEN® 40) provided on average 21kg N ha-1 to the plant by the VT-R1 growth stages. Data from small-plot and on-farm trials suggest that this technology can improve crop N status pre-flowering and has potential to mitigate the risk of yield loss associated with a reduction in synthetic N fertilizer inputs.

Successful NH3 abatement policies and regulations in German agriculture

Anthropogenic ammonia (NH3) emissions, of which about 95 % are from agriculture, have led to environmental pollution, resulting in tremendous damage to human health and ecosystems. Thus, the NEC Directive 2016/2284/EU sets national reduction targets for NH3 emissions in individual EU countries. To implement the NEC Directive for NH3 emission targets, Germany amended the Fertilizer Application Ordinance in 2017 and 2020 (DüV_amended) and set the air pollution control regulation, Technical Instructions on Air Quality Control (TA_Luft). This study aimed to evaluate the impact of the DüV_amended on NH3 mitigation from applying livestock manure, digestates, synthetic nitrogen (N) fertilizers, and TA_Luft on housing and storage. This study showed that Germany reached the first national NH3 reduction target in 2020, as set by the NEC directive. The German DüV_amended, a significant policy change, has profoundly impacted NH3 emission mitigation from agriculture after 2017 by implementing measures aimed directly at NH3 reduction, reducing N surpluses, and improving N use efficiency. The reduction in NH3 emissions from synthetic N fertilizers between 2016 and 2022 contributed about 51 % to the decrease from the agricultural sector over the same period. Among the synthetic fertilizers, NH3 reduction from urea between 2016 and 2022 accounted for around 83 % of the total reduction from synthetic N, indicating that the NH3 emissions from urea fertilizer by reducing urea application and mandating urea to be incorporated immediately or to be stabilized with urease inhibitors played a crucial role in the sharp decrease in NH3 emissions over the last years in Germany. Achieving a high yield by lowering the synthetic N rate in this study strongly suggests that optimal reduction in N rate does not necessarily result in yield losses but rather in a pivotal relationship between the agronomic and environmental performance and indicates that the DüV_amended was an effective measure that can reduce the NH3 emissions.Over 80 % of Germany's annual agricultural NH3 emissions in 2021 and 2022 originated from livestock and digestates from energy crops. Mandatory close to the soil band application of slurry and digestates on cultivated cropland since 2020 reduced NH3 emissions. In addition, banning of broadcast application of slurry to grassland and manure incorporation within one hour on uncultivated soils will become mandatory in 2025 to comply with NEC 2030´s target of 29 % NH3 reduction relative to 2005. The recent German air pollution control regulation (TA_Luft) enforces abatement measures such as air purifiers in large poultry and pig housings and covered storage of slurry and digestate storages of large farms. The results of the German NH3 abatement strategy for synthetic N fertilizers may help reduce NH3 emissions worldwide, especially for countries consuming high amounts of urea fertilizers.

Tracking Carbon and Ammonia Emission Flows of China's Nitrogen Fertilizer System: Implications for Domestic and International Trade.

China is the world's largest producer, consumer, and exporter of synthetic nitrogen (N) fertilizer. To assess the impact of domestic demand and international exports, we quantified the life-cycle CO2eq and ammonia (NH3) emissions by tracking carbon (C) and nitrogen (N) flows from coal/gas mining through ammonia production to N fertilizer production, application, and export. In 2020, China's N fertilizer system emitted 496.04 Tg of CO2eq and 3.74 Tg of NH3, with ammonia production and N fertilizer application processes contributing 36 and 85% of the life-cycle CO2eq and NH3 emissions, respectively. As the largest importers of N fertilizer, India, Myanmar, South Korea, Malaysia, and the Philippines collectively shifted 112.41 Tg of CO2eq. For every ton of N fertilizer produced and used in China, 16 t of CO2eq and 0.18 t of NH3 were emitted, compared to 9.7 t of CO2eq and 0.13 t of NH3 in Europe. By adopting currently available technologies, improving N fertilizer utilization efficiency and employing nitrification inhibitors could synergistically reduce CO2eq emissions by 20% and NH3 emissions by 75%, while energy transformation efforts would primarily reduce CO2eq emissions by 59%. The production of ammonia using green electricity or green hydrogen could significantly enhance the decarbonization of China's N fertilizer system.

Nodules of Medicago spp. Host a Diverse Community of Rhizobial Species in Natural Ecosystems

Biological nitrogen fixation by rhizobia-nodulated legumes reduces the dependence on synthetic nitrogen fertilizers. Identification of locally adapted rhizobia may uncover economically valuable strains for sustainable agriculture. This study investigated the diversity and symbiotic potential of rhizobia associated with three Medicago species from Eastern Romania’s ecosystems. Phenotypic screening ensured that only rhizobial species were retained for molecular characterization. 16S rDNA sequencing clustered the isolates into four distinct groups: Sinorhizobium meliloti, Sinorhizobium medicae, Rhizobium leguminosarum, and Mesorhizobium spp. The chromosomal genes (atpD, glnII, recA) and nifH phylogenies were congruent, while the nodA phylogeny grouped the Mesorhizobium spp. isolates with R. leguminosarum. Medicago sativa was the most sampled plant species, and only S. meliloti and R. leguminosarum were found in its nodules, while Medicago falcata nodules hosted S. meliloti and Mesorhizobium spp. Medicago lupulina was the only species that hosted all four identified rhizobial groups, including S. medicae. This study provides the first report on the Mesorhizobium spp. associated with M. falcata nodules. Additionally, R. leguminosarum and two Mesorhizobium genospecies were identified as novel symbionts for Medicago spp. Comparative analysis of Medicago-associated rhizobia from other studies revealed that differences in 16S rDNA sequence type composition were influenced by Medicago species identity rather than geographic region.

Role of Wilting Time on the Chemical Composition, Biological Profile, and Fermentative Quality of Cereal and Legume Intercropping Silage

Agricultural production in the Azores primarily focuses on the livestock sector, notably, dairy production, where cows graze year-round in a rotational system. To maintain pasture productivity, farmers often rely on synthetic nitrogen fertilizers, which have adverse environmental impacts like ammonia emissions and nitrate leaching. Alternatively, nitrogen-fixing crops like legumes are explored as green manures to enhance soil quality and reduce dependence on chemical fertilizers. The traditional practice of using mixed forages of legumes and grasses, known as “outonos” or intercrops, has been crucial but is declining over time. These mixtures include plants such as lupins, Vicia faba, oats, and vetch, noted for their adaptability and nitrogen-fixing ability. Due to the high perishability of these crops, effective conservation strategies like ensiling are essential to preserve forage nutritional quality through controlled fermentation. This study evaluates the productivity and quality of intercrop forages in the Azores, focusing on fresh samples and silage prepared with wilting times of 0, 24, 48, and 96 h, followed by comprehensive chemical analyses. Results showed significant changes in fiber components (neutral detergent fiber, acid detergent fiber, and acid detergent lignin) with increased wilting time, leading to reduced digestibility. However, wilting improved dry matter content.

Transforming waste to wealth: Impact of food waste‐derived soil amendments and synthetic nitrogen fertilizer on soil dynamics

AbstractApproximately one‐third of all food produced globally goes to waste, highlighting the need for sustainable waste management technologies like composting and anaerobic digestion. These technologies convert food waste into soil amendment products such as compost, liquid digestate (LD) and solid digestate (SD). However, these food waste‐derived soil amendments have relatively low nutrient contents compared with synthetic nitrogen (N) fertilizers such as urea, making their agricultural use challenging. Despite this, food waste‐derived soil amendments can enhance the physical and biological properties of soil, potentially creating synergistic effects when combined with synthetic N fertilizers. This study aimed to investigate effects of food waste‐derived amendments in soil applied at 50 kg ha−1 total N (compost, LD or SD) and synthetic N fertilizer [urea ammonium nitrate (UAN)] at 50 and 100 kg ha−1 total N. Over 56 days of soil incubation, greenhouse gases (CO2, N2O), soil chemistry (–N, –N, pH) and microbial biomass C (MBC) were measured. Results showed that LD + UAN 50 reduced cumulative N2O emissions by 23% compared with UAN 100, despite having the same total N and similar available N rate applied to soil. Replacing UAN with LD in farming practices can supply equivalent available N while lowering N2O emissions, offering a sustainable nutrient strategy. Moreover, applying food waste‐derived soil amendments can enhance N retention in soils, reducing the need for increased applications of synthetic N fertilizers to compensate for N deficits in farming. Food waste‐derived soil amendments can also act as a slower N release compared with UAN, reducing nitrogen run‐off. SD had the highest CO2 emissions, followed by LD and compost. SD + UAN 50 increased MBC levels because of higher carbon content and labile carbon, and available N because of the application of UAN. The major drawback of using SD compared with LD is that the process of evaporating LD to form SD causes high ammonia volatilization (ammonium in solution into ammonia gas) rates, reducing the available N in SD. Therefore, future studies should explore strategies to reduce ammonia volatilization of LD.

Analysis of promoter region and regulatory elements of Rhizobium giardinii DNA-binding response regulator A3AY_RS01 genes

BackgroundRhizobium giardinii has been demonstrated to colonize the roots of a variety of legume species, including common beans, and to increase nitrogen fixation. This suggests that Rhizobium giardinii might be a beneficial tool for sustainable agriculture by lowering dependency on synthetic nitrogen fertilizers and enhancing soil fertility. Understanding the regulatory components in the R. giardinii A3AY_RS01 genes might also lead to the creation of innovative ways for increasing the effectiveness of nitrogen fixation in other agriculturally important bacteria. Therefore, this study was aimed to predict regulatory element of R. giardinii DNA-binding response regulator A3AY_RS01 genes. ResultsThe locations for 19 % of the Transcriptional start site (TSSs) were within −300 bp relative to the start codon and ten candidate motifs were identified that are shared by at least 50 % of the R. giardinii A3AY_RS01 promoter input sequences from both strands. Motif 1 was revealed as the common promoter motif for all of R. giardinii A3AY_RS01 genes that serves as binding sites for TFs involved in the expression regulation of these genes. Hence, it was revealed that Motif 1 may serve as the binding site chiefly for Ferric uptake regulator (Fur) transcription factor family to regulate expression of A3AY_RS01 genes. High CpG density in the promoter than body regions were observed for most of the genes except for A3AY_RS0102950, A3AY_RS0120195 and A3AY_RS0131150 genes. Nonetheless, promoter areas were richer than body regions in both techniques. ConclusionsMV1 motif can serve as a binding site for the Fur transcription factor gene family in R. giardinii to regulate the expression of R. giardinii A3AY_RS01 genes. R. giardinii A3AY_RS01 genes are rich in CpG Islands, and play an important role in the regulation of the gene expression of nitrogen fixing in this bacterium.

Inoculation of nitrogen-fixing bacteria to mitigate the negative effect of brackish water on peanuts

The use of nitrogen-fixing bacteria reduces the use of synthetic nitrogen fertilizers. However, salt stress can negatively affect the establishment of biological nitrogen fixation (BNF). In this context, the aim was to evaluate the use of brackish water at different phenological stages on the gas exchange and mineral composition of inoculated and non-inoculated peanut crops. The experimental design used was completely randomized, following a 5x2 factorial arrangement, with four replications, using five irrigation strategies with brackish water with an electrical conductivity of 5.0 dS m-1 applied at different phenological stages of the crop: E1 - at 14 days after sowing - DAS (vegetative stage); E2 - at 25 DAS (flowering stage); E3 - at 36 DAS (gynophore emergence stage); E4 - at 46 DAS (pod formation stage); and E5 - control, and inoculated and non-inoculated plants. The earlier the salt stress is applied, the lower the gas exchange in the peanut crop, with more significant effects up to 36 DAS, the phase of gynophore emergence and elongation, so plants inoculated with rhizobia show greater efficiency in the use of brackish water. Similarly, from 36 DAS onwards, leaf mineral content decreases, with the exception of sodium, which increases. It is recommended to use brackish water associated with the use of Bradyrhizobium spp. in the pod formation stage of the peanut crop.

Mineralized nitrogen uptake by plants of the use of synthetic nitrogen fertilization in agriculture

The underground transfer of nitrogen from non-food crop residues to cash crops is an important tool to ensure decent crop yields and balance N use in agroecosystems. Laboratory experiments were performed to determine nitrogen migration in spring wheat at different growth stages using labelled nitrogen. In the first stage of the experiment, Artemisia dubia was grown in climate chambers (Climacell CLC-707-TV), with air temperature cycles of 8 h at 15 °C and 16 h at 20 °C, and fertiliz using 15N isotope enriched ammonia nitrate. In the second stage of the experiment, spring wheat was sown and grown to full maturity in two soils of differing soil acidity (pH 3.93 ± 0,04 and pH 7.07 ± 0,08) and mixed with the chopped pieces (3–5 cm mean length) of Artemisia dubia above-ground biomass obtained in the first stage of the experiment. Each soil had four experimental treatments: non-enriched biomass; non-enriched biomass and fertilizer (170 N kg h−1); biomass enriched by 15N and no fertilizer, and 15N enriched biomass and fertilizer (170 N kg h−1). Spring wheat and soil were sampled every two weeks for dry matter (DM), total N and 15N content measurements during the experiment (13 weeks). The results showed that improved crop nitrogen utilization from Artemisia dubia residues were achieved when additional crop fertilizers was not used. It implies that adding additional nitrogen might increase the degradation of plant biomass, but at the same time cause environmental pollution by leaching as plants use it slightly for their growth.

Innovation Policy Beyond Patents: A Case Study on the Development of Climate-Friendly Fertilizers

Abstract Nitrogen fertilizers have revolutionized agriculture since the early 20th century and made a decisive contribution to combating world hunger. Nevertheless, the technology is controversial today because production is energy-intensive and contributes significantly to climate change. In addition, conventional fertilizers pollute groundwater, rivers and coastal waters. Synthetic nitrogen fertilizer is made from ammonia (NH3) produced by the Haber-Bosch process, for which a patent was filed with the German Imperial Patent Office in 1908 (DE235421). For the urgently needed development of modern climate-friendly fertilizers, patent law seems to have played a minor role so far. The large and patent-active agrochemical corporations in the industrialized countries are focusing on other technologies, leaving fertilizer production to companies with direct access to energy below the global market price. Another reason is the very generous regulation of nitrogen fertilizers. For farmers, the use of less climate-damaging fertilizers is not worthwhile. However, the disruption of supply chains in the wake of Russia’s aggression in Ukraine and the aggravation of climate change could lead to a rethink. In the US, the first support programs for the development of climate-friendly, innovative ‘next-generation’ fertilizers have been launched. This paper examines the interplay of patent law in concert with regulatory law and government funding tools in the area of innovative fertilizers. It starts from the hypothesis that other legal frameworks have a stronger influence on innovation activity than patent law at the moment. But this could change if the regulatory framework were to impose stricter requirements for the use of fertilizers.

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.

Policy and law: the case of synthetic nitrogen fertilizer

Agriculture occupies more than a third of the world’s land with many, large-scale impacts on the environment and human health. This article investigates the failure of policy to manage these impacts, asks whether private law can fill the gap, and what this means for policymakers. The investigation takes the form of a case study of synthetic nitrogen fertilizer (SNF) in English policy and law. The SNF industry has been chosen because, by its own account, it underpins the modern food system, which is recognized as needing urgent transformation. The article first assesses the damage caused by SNF to health and the environment and the potential legal remedies. It then assesses industry claims that SNF (a) provides food security, (b) is beneficial to soil and water, and (c) reduces greenhouse gas emissions. If misleading, these representations could amount to unlawful ‘greenwashing’. While private law can never replace good policy and regulation, the article concludes that there is evidence to enable private law to supplement policy, and that this role is made possible as well as necessary by the absence of effective regulation and enforcement. Private litigation could catalyze policymakers to implement the robust regulatory regime that agriculture demands. As the law must focus on scientific evidence and causation, it can also help elucidate and publicize the science on which policy is based. Finally, because of the strict constraints within which private litigation must operate, it can direct policymakers towards strategic interventions (or tipping points) that could catalyze systemic change.

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.