Addressing challenges associated with nitrification inhibitors.

Despite global yield benefits from the use of nitrification inhibitors (NIs), the uncertainties and limitations surrounding NIs warrant more attention. Understanding the impacts of NIs on the health of organisms, people, and ecosystems is also crucial. Here we present a global budget, current challenges, and future research priorities of NIs.

Short-term effects of irrigation and nitrogen management on paddy soil carbon pools under deep placement of basal fertilizer nitrogen.

Active soil organic carbon (SOC) fractions are major driving factors of soil fertility. Understanding the effects of water and fertilizer management on changes in active SOC fractions helps improve soil quality and maintain high agricultural productivity. We conducted a 3-year field experiment in Northeast China. In this experiment, natural soil (CKT) was used as a blank, and two irrigation regimes were established: conventional flooded irrigation (FI) and controlled irrigation (CI). Four nitrogen application levels were set for both irrigation regimes under deep placement of basal fertilizer N: Nd0 (0 kg ha-1), Nd (110 kg ha-1), Nd1 (99 kg ha-1), and Nd2 (88 kg ha-1). After 3 years, at similar N fertilizer application rate, the rice yield, total organic carbon (TOC), and active SOC fraction content of CI were higher under CI than FI. The growth rate of rice yield was 3.8% - 8.63% under CI than FI. Under CI, the rice yield, active SOC fractions contents and carbon pool management index (CPMI) did not decrease with decreasing N application rate but instead reached the highest level in the CNd1 treatment. Overall, CI with Nd1 treatment appears to be the best practice for improving soil fertility and crop productivity in Northeast China.

Influence of nitrogen substitution at an equivalent total nitrogen level on bacterial and fungal communities, as well as enzyme activities of the ditch bottom soil in a rice-fish coculture system.

BACKGROUND: Rice-fish coculture system (RFS) operates through effectively utilizing water and land resources in a complementary form, but it requires more efficient utilization of fertilizer and feed without compromising rice yield. However, the knowledge of how to regulate the proportion of nitrogen (N) supplied from fertilizer and feed at an equivalent total N level to improve the benefits of RFS remains limited. Therefore, four treatments (S0: RFS with 0% N from fertilizer and 100% N from feed; S25: RFS with 25% N from fertilizer and 75% N from feed; S50: RFS with 50% N from fertilizer and 50% N from feed; S75: RFS with 75% N from fertilizer and 25% N from feed) were conducted to assess the variation of ditch bottom soil properties, microbial communities and enzyme activities, as well as to obtain the optimal ratio of N supplied from fish feed and fertilizer. RESULTS: The experiments showed that the contents of soil organic matter, total carbon and total N, and the activities of urease, N-acetyl-ß-D-glucosaminidase, protease, ß-1,4-glucosidase and catalase in the ditch bottom soil significantly reduced in S25 treatment, compared with the other three treatments. Ammonium N content decreased with increasing percentage of the basal fertilizer, whereas nitrate N content and pH value showed an adverse trend. However, the bacterial and fungal communities were unaffected by the ratio shifts between fertilizer-N and feed-N, but their dominant phyla were influenced by the ditch bottom soil N level. Moreover, the bacterial community composition was positively related to nitrate N, whereas fungal diversity was positively correlated with pH, ammonium N and nitrate N, and urease. We also found that the treatment of N input with 25% N from fertilizer and 75% N from feed can reduce N deposition in the ditch bottom soil in the rice-fish coculture system. CONCLUSION: Our findings indicate that under the equivalent total N input level, the relative higher ratio of N from fish feed increased (S0 treatment) or reduced (S25 treatment) the deposition of N in the ditch bottom soil, and improved fish production, but decreased rice yield; while the higher ratio of N from basal fertilizer increased the transportation of nutrients into the ditch bottom soil and rice yield, but reduced fish production. So when considering multi-balance and multiple benefits, we recommend that a selective substitution ratio within 50% ~ 75% from fish feed to substitute for the basal fertilizer under the equivalent total N input may achieve a good balance of rice and fish production improvement, and reduce nutrients wastage to the ditch bottom, as well as alleviate the potential of non-point source pollution. This study also provides an evidence for regulating and optimizing the ratio of N supplied from fertilizer and fish feed at an equivalent total N level through monitoring the nutrient accumulation in ditch bottom soil in the rice-fish coculture system. © 2024 Society of Chemical Industry.

Novel annual nitrogen management strategy improves crop yield and reduces greenhouse gas emissions in wheat-maize rotation systems under limited irrigation.

Excessive irrigation and nitrogen application have long seriously undermined agricultural sustainability in the North China Plain (NCP), leading to declining groundwater tables and intensified greenhouse gas (GHG) emissions. Developing low-input management practices that meet the growing food demand while reducing environmental costs is urgently needed. Here, we developed a novel nitrogen management strategy for a typical winter wheat-summer maize rotation system in the NCP under limited irrigation (wheat sowing irrigation only (W0) or sowing and jointing irrigation (W1)) and low nitrogen input (360 kg N ha-1, about 70 % of traditional annual nitrogen input). Novel nitrogen management strategy promoted efficient nitrogen fertilizer uptake and utilization by both crops via optimization of nitrogen fertilizer allocation between the two crops, i.e., increasing nitrogen inputs to wheat (from 180 to 240 kg N ha-1) while reducing nitrogen inputs to maize (from 180 to 120 kg N ha-1). Three-year field study demonstrated that integrated management practices combining novel nitrogen management strategy with limited irrigation increased annual yields and PFPN by 1.9-5.7 %, and reduced TGE by 55-68 kg CO2-eq ha-1 and GHGI by 2.2-10.3 %, without any additional cost. Our results provide agricultural operators and policymakers with practical and easy-to-scalable integrated management strategy, and offer key initiative to promote grain production in the NCP towards agriculture sustainable intensification with high productivity and efficiency, water conservation and emission reduction.

A new perspective on anthropogenic nitrogen loss mitigation strategies: Integrated control via sustainable regional integration.

Unregulated regional integrated development disrupts the reactive nitrogen (Nr) cycle, adding complexity to anthropogenic Nr environmental losses. The objective of this study was to establish a framework for mitigating anthropogenic Nr loss through a new regional integration perspective by analyzing anthropogenic Nr loss and integrated control strategies in the Yangtze River Delta (YRD) region from 2011 to 2020. The results revealed that the total Nr loss in the YRD ranged from 1780.7 to 1972.0 Gg N yr-1. Re-linking cropland and livestock is crucial for reducing Nr loss, as they act as the main sources of Nr loss. Spatial analysis at the regional scale revealed that regional integration has led to a dispersion of Nr loss, while uneven development among cities has resulted in a westward shift of 8.6 km in the Nr loss centroid, suggesting the need for the implementation of collaborative governance and integrated environmental regulation in the YRD. At the city scale, 27 cities were clustered into six types based on the similarity of Nr loss structural characteristics, allowing for the development of targeted reduction policies based on the specific Nr structural characteristics of each city. The results of driver and mitigation potential analysis indicated the feasibility of achieving the shared goal of sustainable regional integration and the application of optimal mitigation strategies in different cities and the YRD. Overall, the new-perspective framework established in this study provides valuable references for sustainable Nr management in the context of regional integration.

Determining nitrogen topdressing rates in accordance with actual seedling density and crop nitrogen status in direct-seeded rice.

BACKGROUND: Adjusting nitrogen (N) input based on actual seedling density (ASD) and plant N status is a practical approach for improving the yield stability of direct-seeded rice. However, the adjustment of topdressing N rates has been empirical in the past. This study aimed to establish a quantitative approach for determining N topdressing rates during tillering (Ntil ) and panicle development (NPI ) based on ASD and crop N status in direct-seeded rice. Field experiments were conducted involving 12 treatments, consisting of four Ntil and three seeding rates in 2017, and eight treatments combining seeding rate, Ntil , and NPI in 2020. RESULTS: Linear regression analysis revealed that the tiller number at panicle initiation (TILPI ) was predominantly influenced by ASD and Ntil . The determination coefficients (R2 ) of the regression models ranged from 0.887 to 0.936 across the four-season experiments. The results indicated that Ntil could be determined accurately using ASD and the target maximum tiller number. Similarly, grain yield was influenced significantly by the N uptake at panicle initiation (NUPPI ) and NPI , with R2 of 0.814 and 0.783 in the early and late seasons of 2020, respectively. This suggested that NPI could be calculated based on NUPPI and the target grain yield. CONCLUSION: The findings offer a quantitative method for establishing N topdressing rates for tillering and panicle development, relying on the monitoring of actual seedling density and plant N status in direct-seeded rice production. © 2023 Society of Chemical Industry.

Evaluating Nitrogen Management Practices for Greenhouse Gas Emission Reduction in a Maize Farmland in the North China Plain: Adapting to Climate Change.

Quantification of the trade-offs among greenhouse gas (GHG) emissions, yield, and farmers' incomes is essential for proposing economic and environmental nitrogen (N) management strategies for optimizing agricultural production. A four-year (2017-2020) field experiment (including four treatments: basic N fertilizer treatment (BF), suitable utilization of fertilization (SU), emission reduction treatment (ER), and high fertilization (HF)) was conducted on maize (Zea mays L.) in the North China Plain. The Life Cycle Assessment (LCA) method was used in this study to quantify the GHG emissions and farmers' incomes during the whole maize production process. The total GHG emissions of BF, SU, ER, and HF treatments in the process of maize production are 10,755.2, 12,908.7, 11,950.1, and 14,274.5 kg CO2-eq ha-1, respectively, of which the direct emissions account for 84.8%, 76.8%, 74.9%, and 71.0%, respectively. Adding inhibitors significantly reduced direct GHG emissions, and the N2O and CO2 emissions from the maize fields in the ER treatment decreased by 30.0% and 7.9% compared to those in the SU treatment. Insignificant differences in yield were found between the SU and ER treatments, indicating that adding fertilizer inhibitors did not affect farmers' incomes while reducing GHG emissions. The yield for SU, ER, and HF treatments all significantly increased by 12.9-24.0%, 10.0-20.7%, and 2.1-17.4% compared to BF, respectively. In comparison with BF, both SU and ER significantly promoted agricultural net profit (ANP) by 16.6% and 12.2%, with mean ANP values of 3101.0 USD ha-1 and 2980.0 USD ha-1, respectively. Due to the high agricultural inputs, the ANP values in the HF treatment were 11.2%, 16.6%, and 12.4% lower than those in the SU treatment in 2018-2020. In conclusion, the combination of N fertilizer and inhibitors proved to be an environmentally friendly, high-profit, and low-emissions production technology while sustaining or even increasing maize yields in the North China Plain, which was conducive to achieving agricultural sustainability.

Managing nitrogen for sustainable crop production with reduced hydrological nitrogen losses under a winter wheat-summer maize rotation system: an eight-season field study.

Excessive nitrogen (N) application in wheat-maize cropping systems was adjusted towards more sustainable practices to reduce hydrological N losses while maintaining crop yield. In comprehensive quantification of N management effects on crop yield, N use efficiency (NUE), hydrological N losses, and soil nitrate residual across eight seasons, we have added to growing evidence of strategies beneficial for sustainable crop production with lower hydrological N losses. The results show that adjusted N practices enhanced crop yield and NUE, as compared to farmer's practices, but benefits varied with N rates and types. Optimized N treatment (OPT, 180 kg N ha-1 in both maize and wheat seasons) with or without straw returning produced the most crop yield. They increased maize yield by 5.5% and 7.3% and wheat yield by 6.2% and 3.2% on average, as compared to farmer's practice with huge N application (FP, 345 kg N ha-1 and 240 kg N ha-1 in maize and wheat). Regulation of N release through amendment with controlled release urea at a rate of 144 kg N ha-1 crop-1 (CRU treatment) obtained 4.4% greater maize yield than FP, and sustained a similar wheat yield with less N input, resulting in the highest crop NUE. Additionally, CRU was most effective in mitigating hydrological N loss, with 39.5% and 45.5% less leachate N and 31.9% and 35.9% less runoff N loss than FP in maize and wheat seasons. Synthetic N input correlated significantly and positively with runoff and leachate N losses, indicating it was one of the dominant factors driving hydrological N losses. Moreover, compared to OPT, additional straw returning (STR) or substituting 20% of the nutrients by duck manure (DMS) further reduced runoff N discharges due to the fact that organic matter incorporation increased resilience to rainfall. N over-application in FP caused considerable nitrate accumulation in the 0-90-cm soil profile, while the adjusted N practices, i.e., OPT, STR, CRU, and DMS treatments effectively controlled it to a range of 79.6-92.9 kg N ha-1. This study suggests that efforts using optimized N treatment integrated with CRU or straw returning should be encouraged for sustainable crop production in this region.

Drug discovery-based approach identifies new nitrification inhibitors.

Nitrogen (N) fertilization is crucial to sustain global food security, but fertilizer N production is energy-demanding and subsequent environmental N losses contribute to biodiversity loss and climate change. N losses can be mitigated be interfering with microbial nitrification, and therefore the use of nitrification inhibitors in enhanced efficiency fertilizers (EEFs) is an important N management strategy to increase N use efficiency and reduce N pollution. However, currently applied nitrification inhibitors have limitations and do not target all nitrifying microorganisms. Here, to identify broad-spectrum nitrification inhibitors, we adopted a drug discovery-based approach and screened 45,400 small molecules on different groups of nitrifying microorganisms. Although a high number of potential nitrification inhibitors were identified, none of them targeted all nitrifier groups. Moreover, a high number of new nitrification inhibitors were shown to be highly effective in culture but did not reduce ammonia consumption in soil. One archaea-targeting inhibitor was not only effective in soil, but even reduced - when co-applied with a bacteria-targeting inhibitor - ammonium consumption and greenhouse gas emissions beyond what is achieved with currently applied nitrification inhibitors. This advocates for combining different types of nitrification inhibitors in EEFs to optimize N management practices and make agriculture more sustainable.

Optimizing water and nitrogen management strategies to improve their use efficiency, eggplant yield and fruit quality.

With improvement in living standards, consumer preferences for vegetables are changing from quantity- to quality-oriented. Water and nitrogen supply, as two major determinants of vegetable crop yield and quality, can be optimally managed to improve the yield and quality. To evaluate the response in yield, fruit quality, and water and nitrogen utilization of eggplant to different water and nitrogen management strategies, a 2-year (2021 and 2022) field trial under mulched drip irrigation was conducted. The growth period was divided into seedling, flowering and fruit set, fruit development, and fruit ripening stages. Three irrigation levels were applied during the flowering and fruit set stage: W0, adequate water supply (70%-80% of field water capacity, FC); W1, mild water deficit (60%-70% FC); and W2, moderate water deficit (50%-60% FC). In addition, three nitrogen application rates were applied: N1, low nitrogen level (215 kg ha-1); N2, medium nitrogen level (270 kg ha-1); and N3, high nitrogen level (325 kg ha-1). The irrigation and nitrogen rates were applied in all combinations (i.e., nine treatments in total). Adequate water supply throughout the reproductive period in combination with no nitrogen application served as the control (CK). The yield of the W1N2 treatment was significantly increased by 32.62% and 35.06% in 2021 and 2022, respectively, compared with that of the CK. Fruit soluble protein, soluble solids, and vitamin C contents were significantly higher under W1 than W2. Fruit quality was significantly higher under the N2 rate compared with the other nitrogen rates. The W1N2 treatment showed the highest water productivity, with a significant increase of 11.27%-37.84% (2021) and 14.71%-42.48% (2022) compared with that under the other treatments. Based on the average water-deficit degree and nitrogen application rate, W0 and N1 had the highest partial factor productivity of nitrogen. Assessment of the results using the TOPSIS (technique for order preference by similarity to an ideal solution) method indicated that mild water deficit in combination with the medium nitrogen application rate (W1N2) was the optimal water and nitrogen management strategy for cultivated eggplant. The present findings contribute novel insights into the sustainable cultivation of eggplant in an oasis arid environment.

Nitrate leaching potential from arable land in Germany: Identifying most relevant factors.

Diffuse nitrogen losses from agriculture in Germany continue to cause regionally increased nitrate concentrations in groundwater. Groundwater quality monitoring cannot be a timely indicator of the effects of mitigation measures being applied in agriculture, due to frequently long transport routes and high residence times of the leachate. Instead, nitrate leaching potential is often determined at field and farm scale by monitoring soil mineral nitrogen contents at 0-90 cm depth in autumn (SMNa), i.e. before the start of the annual leachate period. In this study, we developed an understanding of the controls on the soil mineral nitrogen content at the start of winter. In an on-farm approach, extensive data was collected from 48 farms in five nitrate-sensitive regions in Germany from 2017 to 2020. From this data set, 25 management and site factors were evaluated with regard to their significance for SMNa by means of a random forest model. With the random forest regression, we identified the role of the factors on SMNa with an acceptable model accuracy with R2 = 0.56. The results show that the cultivated crop is the most important factor influencing SMNa. Potatoes, oilseed rape and maize produced the highest SMNas, whereas SMNas were lowest after spring barley, sugar beet and winter barley. Among site factors, soil type and texture as well as precipitation in October were most decisive. The effects of N fertilisation parameters such as rate and timing were masked by these site factors. The results show that the reduction of nitrogen-intensive crops in crop sequences can be a promising measure for the reduction of nitrate loads. On the other hand, our analysis makes clear that soil-related factors controlling nitrogen release and risk of leaching, as well as weather, can significantly mask the effect of cultivation.

Potential mitigation of environmental impacts of intensive plum production in southeast China with maintenance of high yields: Evaluation using life cycle assessment.

Introduction: Intensive plum production usually involves high yields but also high environmental costs due to excessive fertilizer inputs. Quantitative analysis of the environmental effects of plum production is thereby required in the development of optimum strategies to promote sustainable fruit production. Methods: We collected survey questionnaires from 254 plum production farms in Zhao'an county, Fujian province, southeast China to assess the environmental impacts by life cycle assessment (LCA) methodology. The farms were categorized into four groups based on yield and environmental impacts, i.e., LL (low yield and low environmental impact), LH (low yield but high environmental impact), HL (high yield but low environmental impact), and HH (high yield and high environmental impact). Results: The environmental impacts, i.e., average energy depletion, global warming, acidification, and eutrophication potential in plum production were 18.17 GJ ha-1, 3.63 t CO2 eq ha-1, 42.18 kg SO2 eq ha-1, and 25.06 kg PO4 eq ha-1, respectively. Only 19.7% of farmers were in the HL group, with 13.3% in the HH group, 39.0% in LL, and 28.0% LH. Plum yields of the HL group were 109-114% higher than the mean value of all 254 farms. Additionally, the HL group had a lower environmental impact per unit area compared to the overall mean value, with a reduction ranging from 31.9% to 36.7%. Furthermore, on a per tonne of plum production basis, the energy depletion, global warming potential, acidification potential, and eutrophication potential of HL farms were lower by 75.4%, 75.0%, 75.6%, and 75.8%, respectively. Overall, the total environmental impact index of LL, LH, HL, and HH groups were 0.26, 0.42, 0.06, and 0.21, respectively. Discussion: Excessive fertilizer N application was the main source of the environmental impacts, the potential to reduce fertilizer N rate can be achieved without compromising plum yield by studying the HH group. The results provide an important foundation for enhancing the management of plum production, in order to promote 'green' agricultural development by reducing environmental impacts.

Achieving high yield and nitrogen agronomic efficiency by coupling wheat varieties with soil fertility.

Wheat breeding has progressively increased yield potential through decades of selection, markedly increased the capacity for food production. Nitrogen (N) fertilizer is essential for wheat production and N agronomic efficiency (NAE) is commonly index used for evaluate the effects of N fertilizer on crop yield, calculated as the difference of wheat yield between N fertilizer treatment and non-N fertilizer treatment divided by the total N application rate. However, the impact of variety on NAE and its interaction with soil fertility remain unknown. Here, to clarify whether and how wheat variety contributes to NAE, and to determine if soil conditions should be considered in variety selection, we conduct a large-scale analysis of data from 12,925 field trials spanning ten years and including 229 wheat varieties, 5 N fertilizer treatments, and a range of soil fertility across China's major wheat production zones. The national average NAE was 9.57 kg kg-1, but significantly differed across regions. At both the national and regional scales, variety significantly affected NAE, and different varieties showed high variability in their performance among low, moderate, and high fertility soils. Here, superior varieties with both high yield and high NAE were identified at each soil fertility fields. The comprehensive effect of selecting regionally superior varieties, optimizing N management, and improving soil fertility could potentially decrease the yield gap by 67 %. Therefore, variety selection based on soil conditions could facilitate improved food security while reducing fertilizer inputs to alleviate environmental impacts.

Regional estimates of nitrogen budgets for agricultural systems in the East African Community over the last five decades.

The great challenge of reducing soil nutrient depletion and assuring agricultural system productivity in low-income countries caused by limited synthetic fertilizer use necessitates local and cost-effective nutrient sources. We estimated the changes of the nitrogen budget of agricultural systems in the East African Community from 1961 to 2018 to address the challenges of insufficient nitrogen inputs and serious soil nitrogen depletion in agricultural systems of the East African Community region. Results showed that total nitrogen input increased from 12.5 kg N ha-1yr-1 in the 1960s to 21.8 kg N ha-1yr-1 in the 2000s and 27 kg N ha-1yr-1 in the 2010s. Total nitrogen crop uptake increased from 12.8 kg N ha-1yr-1 in the 1960s to 18.2 kg N ha-1yr-1 in the 2000s and 21.8 kg N ha-1yr-1 in the 2010s. Soil nitrogen stock increased from -2.0 kg N ha-1yr-1 in the 1960s to -0.5 kg N ha-1yr-1 in the 2000s and 0.3 kg N ha-1yr-1 in the 2010s. Our results allow us to substantiate for the first time that soil nitrogen depletion decreases with increasing input of nitrogen in agricultural systems of the East African Community region. This suggests that increases in nitrogen inputs through biological nitrogen fixation and animal manure are the critical nitrogen management practices to curb soil nitrogen depletion and sustain agricultural production systems in the East African Community region in order to meet food demand for a growing population. Supplementary Information: The online version contains supplementary material available at 10.1007/s13593-023-00881-0.

Increasing the yield of drip-irrigated rice by improving photosynthetic performance and enhancing nitrogen metabolism through optimizing water and nitrogen management.

Drip irrigation under plastic film mulching is an important technique to achieve water-conserving and high-efficiency rice (Oryza sativa L.) production in arid areas, but the grain yield of drip-irrigated rice is much lower than the expected yield (10.9-12.05 t·hm-2) in practical production applications. Therefore, we hope to further understand the photosynthetic physiological mechanism of drip-irrigated rice yield formation by optimizing water and nitrogen management during the growth period and provide a scientific reference for improving yield and nitrogen use efficiency (NUE) of drip-irrigated rice in arid areas. In 2020 and 2021, T-43 (a drought-resistant; V1) and Liangxiang-3 (a drought-sensitive cultivar; V2) were cultivated under two water treatments (W1: limited drip irrigation, 10200 m3·hm-2; W2: deficit drip irrigation, 8670 m3·hm-2) and three nitrogen fertilization modes with different ratios of seedling fertilizer:tillering fertilizer:panicle fertilizer:grain fertilizer (N1, 30%:50%:13%:7%; N2, 20%:40%:30%:10%; and N3, 10%:30%:40%:20%). The photosynthetic characteristics, nitrogen metabolism, yield, and NUE were analysed. The results showed that compared with other treatments, the W1N2 resulted in 153.4-930.3% higher glutamate dehydrogenase (GDH) contents and 19.2-49.7% higher net photosynthetic rates (P n) in the leaves of the two cultivars at 20 days after heading, as well as higher yields and NUE. The two cultivars showed no significant difference in the physiological changes at the panicle initiation stage, but the P n, abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA3), and zeatin riboside (ZR) levels of V1 were higher than those of V2 by 53.1, 25.1, 21.1, 46.3 and 36.8%, respectively, at 20 days after heading. Hence, V1 had a higher yield and NUE than V2. Principal component analysis revealed that P n and GDH were the most important physiological factors affecting rice yield performance. In summary, the W1N2 treatment simultaneously improved the yield and NUE of the drought-resistant rice cultivar (T-43) by enhancing the photosynthetic characteristics and nitrogen transport capacity and coordinating the balance of endogenous hormones (ABA, IAA, GA3, and ZR) in the leaves.

Effect of nitrogen management in cultivation on the stability and microbial community of post-harvest Monoraphidium sp. algae biomass.

Long-term storage is necessary to mitigate for seasonal variation in algae productivity, to preserve biomass quality and to guarantee a constant biomass supply to a conversion facility. While ensiling has shown promise as a solution, biomass attributes for successful storage are poorly understood. Storage studies of Monoraphidium sp. biomass indicate a strong correlation between nitrogen management in algae cultivation and stability of post-harvest algae biomass. Algae cultivated with periodic nitrogen addition were stored poorly (>20% loss, dry basis) compared to biomass from nitrogen depleted cultivation (8% loss, dry basis). A follow-up study compared the post-harvest stability of Monoraphidium biomass cultivated in nitrogen-deplete or nitrogen-replete conditions. Replete biomass experienced the largest degradation (24%, dry basis), while deplete biomass experienced the least (10%, dry basis). Dry matter loss experienced among blends of each correlated positively with nitrogen-replete biomass content. The composition of the post-storage algae microbial community was also affected by cultivation conditions, with Clostridia species being more prevalent in stored biomass obtained from nitrogen-replete cultivations. Nitrogen management has long been known to influence algae biomass productivity and biochemical composition; here, we demonstrate that it also strongly influences the stability of post-harvest algae biomass in anaerobic storage.

Nitrogen management in farming systems under the use of agricultural wastes and circular economy.

Population growth leads to an increase in the demand for energy, water, and food as cities grow and urbanize. However, the Earth's limited resources are unable to meet these rising demands. Modern farming practices increase productivity, but waste resources and consume too much energy. Agricultural activities occupy 50 % of all habitable land. After a rise of 80 % in 2021, fertilizer prices have increased by nearly 30 % in 2022, representing a significant cost for farmers. Sustainable and organic farming has the potential to reduce the use of inorganic fertilizers and increase the utilization of organic residues as a nitrogen (N) source for plant nutrition. Agricultural management typically prioritizes nutrient cycling and supply for crop growth, whereas the mineralization of added biomass regulates crop nutrient supply and CO2 emissions. To reduce overconsumption of natural resources and environmental damage, the current economic model of "take-make-use-dispose" must be replaced by "prevention-reuse-remake-recycle". The circular economy model is promising for preserving natural resources and providing sustainable, restorative, and regenerative farming. Technosols and organic wastes can improve food security, ecosystem services, the availability of arable land, and human health. This study intends to investigate the nitrogen nutrition provided by organic wastes to agricultural systems, reviewing the current state of knowledge and demonstrating how common organic wastes can be utilized to promote sustainable farming management. Nine waste residues were selected to promote sustainability in farming based on circular economy and zero waste criteria. Using standard methods, their water content, organic matter, total organic carbon, Kjeldahl nitrogen, and ammonium levels were determined, along with their potential to improve soil fertility via N supply and technosol formulation. 10 % to 15 % of organic waste was mineralized and analysed during a six-month cultivation cycle. Through the results, the combination of organic and inorganic fertilization to increase crop yield is recommended, as is the search for realistic and practical methods of dealing with massive amounts of organic residues within the context of a circular economy.

Sustainable nitrogen management strategies based on nitrogen flow in urban human system.

Urban nitrogen discharge has become an important factor leading to urban water environment deterioration, water crisis, and frequent air pollution. Human consumption is the driving force of nitrogen flow and the core of urban nitrogen research. Based on the process of nitrogen flow in the urban human system, combined with the relevant United Nations Sustainable Development Goals (SDGs) and taking Dar es Salaam as an example, we established a generic analytical framework for sustainable nitrogen management and put forward the strategies of sustainable nitrogen management in the urban human system. The main conclusions are as follows. (1) Waste nitrogen discharge affected the environment quality. 5286 t of N (5095 t of N-NH3, 86 t of N-N2O, and 105 t of N-NOx) was emitted into the atmosphere that affected air quality. 9304 t of N was discharged into surface water and 203 t of N was leaked, which had a negative impact on the prevention and control of surface water pollution. And 8334 t of N pose a potential threat to environmental quality. (2) Nitrogen management in Dar es Salaam faced huge challenges. From the perspective of nitrogen flow of the urban human system, the diet structure and household energy structure need to be optimized, and food waste is serious. Sewage treatment and garbage treatment are seriously insufficient, and the corresponding technologies are backward. In order to solve the existing problems of nitrogen flow in the urban human system and include sustainable nitrogen management under future challenges of growing population and economy, we proposed strategies including healthy diet guidance, reducing food waste, detailed assessment of household nitrogen accumulation, transformation of household energy structure to low nitrogen emission energy, increasing nitrogen recycling ratio, and infrastructure improvement of sewage treatment and garbage treatment, hence contributing to the achievement of related SDGs.

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

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