Budgeting nitrogen flows and the food nitrogen footprint of Egypt during the past half century: Challenges and opportunities

Spatial-temporal differentiation and control strategies of nitrogen environmental loss in China's coastal regions based on flow analysis

Nitrogen pollution emissions from human production and living activities in coastal regions are important topics in the management of environmental pollution in coastal waters. However, to date, there has been relatively little research systematically assessing the environmental loss of nitrogen (NEL) from human activities that negatively affect marine ecosystems. This study categorised emission sources into five subsystems, namely livestock, farming, aquatic, industrial, and residential. Through flow analysis, the anthropogenic emissions of nitrogen in the gas, liquid, and solid phases from 11 coastal provinces in China in 2011, 2015, and 2020 were determined. A nitrogen cost index was constructed by combining the social indicators of each province. The effectiveness of nitrogen emission control since the land-sea coordination and the future challenges for the coastal region were discussed from various perspectives. The results of the study showed that the total NEL that poses a potential threat to marine ecosystems in coastal areas of China has decreased from 18.93 TgN to 14.66 TgN since the proposal of land-sea coordination, with livestock systems and aquatic systems emitting the most. The Bohai and Yellow Seas area were most threatened by nitrogen pollution. Among the three oceanic pathways, liquid-phase nitrogen discharge from each subsystem was effectively controlled, and the control of gas-phase nitrogen emissions is still the most numerous NEL state, although it has had a significant effect. The results of the correlation analysis suggest that NEL flow can characterize the regional management of nutrient-based organic pollutants. Past management tools and environmental investments in China have been more effective in controlling emissions from point and line sources involving artificial facilities, but less direct effect on mariculture. How to control surface source pollution from livestock and aquaculture will be an important challenge to reduce reactive nitrogen emissions in the future.

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

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

Optimization of the N footprint model and analysis of nitrogen pollution in irrigation areas: A case study of Ningxia Hui Autonomous Region, China

Water diverted from rivers for irrigation areas often contains large amounts of nitrogen (N), which is frequently overlooked and its role in contributing to N pollution is unknown. To investigate the influence of water diversion on N in different systems within irrigation areas, we developed and optimized the N footprint model, taking into account the N carried by irrigation water diversion and drainage in irrigated areas. This optimized model can serve as a reference for evaluating N pollution in other irrigated areas. By analyzing 29 years (1991-2019) of statistical data from a diverted irrigation area in Ningxia Hui Autonomous Region (Ningxia), China, the study assessed the contribution of water diversion to N in agriculture, animal husbandry, and human domestic activities. The results demonstrated that water diversion and drainage accounted for 10.3% and 13.8% in whole system, of the total N input and output in Ningxia, highlighting the potential N pollution risks associated with these activities. Additionally, the use of fertilizers in the plant subsystem, feed in the animal subsystem, and sanitary sewage in the human subsystem represented the main sources of N pollution in each subsystem. On a temporal scale, the study found that N loss increased year by year before reaching a stable level, indicating that N loss had reached its peak in Ningxia. The correlation analysis suggested that rainfall could regulate N input and output in irrigated areas by showing a negative correlation with water diversion, agricultural water consumption, and N from irrigated areas. Moreover, the study revealed that the amount of N brought by water diverted from rivers for irrigation should be taken into account when calculating the amount of fertilizer N required in the irrigation area.

Regional Analysis of Nitrogen Flow within the Chesapeake Bay Watershed Food Production Chain Inclusive of Trade

In the Chesapeake Bay Watershed, excess nitrogen has contributed to poor water quality, leading to nitrogen mitigation efforts to restore and protect the watershed. The food production system is a top contributor to this nitrogen pollution. While the food trade plays a vital role in distancing the environmental impacts of nitrogen use from the consumer, previous work on nitrogen pollution and management in the Bay is yet to carefully consider the effect of embedded nitrogen found in products (nitrogen mass within the product) imported and exported throughout the Bay. Our work advances understanding across this area by creating a mass flow model of nitrogen embedded in the food production chain throughout the Chesapeake Bay Watershed that separates phases of the production and consumption processes for crops, live animals, and animal products and considers commodity trade at each phase by combining aspects of both nitrogen footprint and nitrogen budget models. Also, by tracking nitrogen embedded in products imported and exported in these processes, we distinguished between direct nitrogen pollution and nitrogen pollution externalities (displaced N pollution from other regions) from outside of the Bay. We developed the model for the watershed and all its counties for major agricultural commodities and food products for 4 years 2002, 2007, 2012, and 2017 with a specific focus on 2012. Using the developed model, we determined the spatiotemporal drivers of nitrogen loss to the environment from the food chain within the watershed. Recent literature leveraging mass balance approaches has suggested that previous long-term declines in nitrogen surplus and improvements in nutrient use efficiency have stagnated or begun to reverse. Our results suggest that within the Chesapeake Bay, increased corn and wheat acreage and steadily increasing livestock/poultry production may have led to the stagnation in decreasing N loss trends from agricultural production observed over the past two decades. We also show that at the watershed scale, trade has reduced the food chain nitrogen loss by about 40 million metric tons. This model has the potential to quantify the effect of various decision scenarios, including trade, dietary choices, production patterns, and agricultural practices, on the food production chain nitrogen loss at multiple scales. In addition, the model's ability to distinguish between nitrogen loss from local and nonlocal (due to trade) sources makes it a potential tool to optimize regional domestic production and trade to meet local watershed's needs while minimizing the resulting nitrogen loss.

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.

Food Nitrogen Footprint Increased by 35% on the Third Pole During 1998-2018

The N footprint is considered as an indicator of potential environmental damage from N. Quantitative analysis of N footprint distribution, sources and drivers can help mitigate its negative impacts and promote sustainable N management. In this study, we constructed a city-scale food N footprint (FNF) framework for the Qinghai-Tibet Plateau (QTP) using a N mass balance approach. We quantitatively analyzed the FNF during food production and consumption on the QTP from 1998 to 2018. We used the logarithmic mean Divisa index decomposition method to analyze the driving forces of the FNF, and the decoupling of the FNF. The results showed that the per capita FNF of the QTP increased from 24.92 kg N cap^-1 in 1998 to 27.70 kg N cap^-1 in 2018, and the total FNF increased by 35.11% from 1998 to 2018. The spatial distribution of the FNF was uneven, with N losses from crop production and animal production being the leading contributing source to the FNF (86%). Economic development and urbanization were the main driving forces behind the FNF increase, while N consumption intensity inhibited the growth of the FNF. With the rapid growth of GDP, the FNF in the eastern part of the QTP grew relatively slowly, indicating a gradual decoupling of the FNF from economic development. To reconcile the relationship between socioeconomic drivers and the FNF, it is necessary to focus on coupling relationships between subsystems within the food production and consumption system to promote N recycling.

Bibliometric Analysis of Current Status of Circular Economy during 2012–2021: Case of Foods

Food is usually recognized as a limited resource in sustainability, recognized by the United Nations (UN) Sustainable Development Goal (SDG) 2, which aims to achieve zero hunger. It is expected that the circular economy (CE) can improve processes related to food production. The objective of the present study was to apply a bibliometric approach using VOSviewer visualization software as a research tool to analyze the relevant literature from the Scopus database in the field of circular economy and its relation to improvements in food issues throughout 2012–2021. A total of 1316 articles were analyzed. Italy was the most productive country with 313 articles, with Wageningen University & Research the organization with the most publications with 39 articles. The top 10 institutions originated from Italy, The Netherlands, France, and Denmark. Sustainability was the most productive journal with 107 articles. Bioresource Technology had the highest average citation frequency (44.68). The study helps initiate investigations to adapt the results obtained and create new strategies for increasing food circular economy efforts.

Effect of drought and nutrient availability on invaded plant communities in a semi-arid ecosystem

Ecosystem functions are heavily dependent on the functional composition of the plant community, i.e., the functional traits of plants forming the community. This, on the one hand, depends on plant occurrence, but on the other hand, depends on the intraspecific variability of functional traits of the species, which are influenced by climate and nutrient availability and affected by plant–plant interactions. To illustrate that, we studied the effects of drought and nitrogen addition (+ N), two important abiotic variables which are changing with ongoing global change, as well as their combined effect on the functional responses of grassland communities in semi‐arid environments of Northern Africa comprising of natural and invasive species. We conducted an experiment where we planted three native species and one invasive plant species in artificial communities of five individuals per species per plot. We exposed these communities to four different treatments: a drought treatment, an N‐addition treatment, the combination between drought and N‐addition, as well as a control. To assess the performance of plants within treatments, we measured selected plant functional traits (plant height, specific leaf area [SLA], leaf dry matter content [LDMC], N content of the leaves [N_mass], specific root length [SRL], and root diameter) for all individuals occurring in our plots, and additionally assessed the above and belowground biomass for each plant individual. We found that the invasive species showed a higher performance (higher biomass accumulation, taller plants, higher SLA, N_mass, SRL, and root diameter as well as lower LDMC) than the native species under drought conditions. The invasive species was especially successful with the combined impact of drought + N, which is a likely scenario in ongoing global change for our research area. Thus, plant functional traits might be a key factor for the invasion success of plant species which will be even more pronounced under ongoing global change.

Occurrence and driving forces of different nitrogen forms in the sediments of the grass and algae-type zones of Taihu Lake

Excessive nitrogen (N) load in sediments is at risk of release resulting in the degradation of grass-type lake ecosystems. At present, the occurrence characteristics of N forms and the driving forces of organic N (ON) hydrolysis in the sediments of Taihu Lake were still unclear. Here, 52 sampling sites in 7 lake areas in Taihu Lake were investigated to compare the spatial occurrence characteristics of the sedimentary free N (FN), exchangeable N (EN), acid hydrolyzable N (HN), and residual N (RN) and their associated driving forces. The results showed that the total N contents in the dry sediment ranged from 1811.56 to 5594.06 mg kg^-1, and the contribution was in the order of RN > HN > EN > FN. Spatially, RN and total organic carbon were significantly consistently influenced by dam construction and deposition algal residue. The HN concentration was high in the estuaries affected by N inputs from the rivers. The coupling relationship of spatial distribution between ON and N forms was revealed. The factors, i.e., algal residue deposition and terrigenous N inputs, were considered as the main driving forces stimulating the ON hydrolysis in the algae-type lake zones. It can be deduced that controlling terrigenous N inputs and sediment suspension may be the key to inhibiting the transformation from grass-type to algae-type lake ecosystem.

Nitrogen-molybdenum-manganese co-fertilization reduces nitrate accumulation and enhances spinach (Spinacia oleracea L.) yield and its quality

Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO₃⁻) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha⁻¹) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL⁻¹ of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L⁻¹, respectively on growth, chemical constituents, and NO₃⁻ accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha⁻¹) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant⁻¹, number of leaves plant⁻¹, leaf area plant⁻¹, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO₃⁻ accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate –N fertilizers, and the lowest values of NO₃⁻ accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO₃⁻ accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha⁻¹ in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L⁻¹). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO₃⁻ accumulation in leaves, resulting agronomical, environmental and economic benefits.

Zinc-biochemical co-fertilization improves rice performance and reduces nutrient surplus under semi-arid environmental conditions

Biofertilizers are a promising approach to substantially improve nutrient recovery and crop production. Moreover, zinc (Zn) deficiency is one of the key abiotic factors limiting global rice production. However, the effect of Zn-biochemical co-fertilization on rice production and nutrients recovery and surplus under semi-arid environmental conditions is not fully obvious. Two years field experiment was conducted to evaluate the effect of Zn-biochemical (nitrogen “N”, phosphorus “P”, and potassium “K”) co-fertilization on yield and yield components, physico-chemical characteristics, and nutrient recovery and surplus as well as farm profitability of four rice (Oryza sativa L.) cultivars treated with two Zn levels (no Zn application, and 600 mg chelated Zn L⁻¹ as a foliar application) and six fertilization regimes (no fertilizers application, biofertilizers, 25% NPK plus biofertilizers, 50% NPK plus biofertilizers, 75% NPK plus biofertilizers, and 100% NPK). Biofertilizers mixture (cerealin, phosphorine, and potassiomage) were used. The results revealed that chemical constituents, growth attributes, yield, yield components, nutrients uptake (N, P, K, and Zn), and nutrients recovery (N, P, and K) significantly increased due to Zn foliar application. Biofertilizers replacement for 25% of inorganic NPK combined with Zn provides the highest nutrients uptake through increasing N, P, and K recovery by 57–94%, 61–128%, and 45–69%, respectively in the four rice cultivars compared with 100% NPK treatment. This improvement in nutrients uptake and recovery was attributed to decrease nutrients surplus by 64–78%, 46–53%, and 50–59%, respectively. Additionally, Zn-biochemical co-fertilization improves growth attributes, yield, and yield components of rice cultivars through producing more contents of chlorophyll a and b, carotenoids, total carbohydrates, and total amino acids than using 100% NPK alone. All previous characteristics significantly affected by the cultivated rice variety. The net return under the treatment of 75% NPK plus biofertilizers plus Zn foliar application was 21.5–27.5% higher than the treatment of 100% NPK. Therefore, our findings suggest that biofertilizers replacement for 25% of inorganic NPK combined with Zn foliar application supplies a financially attractive choice to substantially enhance nutrient recovery and production of rice, while effectively reducing nutrients loss.

Water environmental pressure assessment in agricultural systems in Central Asia based on an Integrated Excess Nitrogen Load Model

Agricultural runoff is the main source of water pollution in Central Asia. Excessive nitrogen (N) inputs from overuse of chemical fertilizers are threatening regional water resources. However, the scarcity of quantitative data and simplified empirical models limit the reliability of grey water footprint (GWF), particularly in undeveloped regions. In this study, we developed an Integrated Excess Nitrogen Load Model (IENLM) to calculate excess N load and evaluate its potential water environmental pressure in Central Asia. The model optimized the biological N fixation and atmospheric N deposition modules by involving more environmental variables and human activities. Results showed that N fertilizer application contributed over 60% to total N input and was mainly responsible for 42.9% increase of total GWF from 101.5 to 145.0 billion m³ during 1992 - 2018. Water pollution level (WPL) increased from 0.55 in 1992 to 2.41 in 2018 and the pollution assimilation capacity of water systems has been fully consumed just by N load from agriculture since 2005. GWF intensity and grey water pollution - efficiency types in all Central Asian countries have improved in recent years except for Turkmenistan. N fertilizer application and agricultural economy development were the main driving factors induced N pollution. Results were validated by riverine nitrate concentrations and the estimates from prior studies. In future, combining the N fertilizer reduction with other farm management practices were projected to effectively improve the WPL. The modeling framework is favorable for N pollution research in data-scarce regions and provides a scientific basis for decision-making for agriculture and water resource managements.

Nitrogen cascade in the agriculture-food-environment system of the Yangtze Delta, 1998-2018

The nitrogen (N) cascade in rural areas of Changshu County should be measured and evaluated due to the large increase in anthropogenic disturbances in China's Yangtze Delta. Here, we developed a village-scale N flow model using Changshu County and its towns as a case study. The model included four subsystems and was used to describe the driving forces behind the N cascade from agricultural food production and household consumption to the environment (agriculture-food-environment) system. It was found that from 1998 to 2018 the N input increased from 274.63 to 848.65 kg N ha^-1. The cropland N use efficiency (NUEc) decreased by 10.35%, whereas the livestock feed N use efficiency (NUEa) increased by 51.84%. A relatively lower NUE, with a higher N input, was found in Shajiabang Town, which was attributed to hairy crab farming. Changes in dietary patterns led to the food N cost (FNC) being in the range of 4.59-7.74 kg kg^-1. Over the past two decades, the N losses from the agriculture-food-environment system decreased by 45.40% from 12,436.60 t N yr^-1 (1998). The contribution of the croplands, livestock-breeding, and household consumption to the N losses were 32.44%, 37.78%, and 29.78%, respectively. About 62.83% of the total N losses entered the water environment. Nitrogen emissions from the croplands accounted for 63.21% of the N losses into the atmosphere. Nitrogen oxide (NO_x) emissions accounted for 38.50% of the gas emissions, followed by NH₃ (28.36%) and N₂O (2.81%). The total N losses decreased annually but losses to the water environment increased by 5.10% from 60.16% (1998). The contribution of food production to the total N loss displayed a decreasing trend, while that of food consumption exhibited an increasing trend. Population growth and increased volumes of domestic waste in the Changsu area were the main driving forces for the increased contribution of household food consumption. The significant decline in cropland area and increase in built-up and heavily trafficked areas indicated an overall increase in anthropogenic disturbances, stimulating the N cascade in the Yangtze Delta from 1998 to 2018.

Biological silicon nanoparticles improve Phaseolus vulgaris L. yield and minimize its contaminant contents on a heavy metals-contaminated saline soil

The synthesis of biological silicon nano-particles (Bio-Si-NPs) is an eco-friendly and low-cost method. There is no study focusing on the effect of Bio-Si-NPs on the plants grown on saline soil contaminated with heavy metals. In this study, an attempt was made to synthesis Bio-Si-NPs using potassium silica florid substrate, and the identified Aspergillus tubingensis AM11 isolate that separated from distribution systems of the potable water. A two-year field trial was conducted to compare the protective effects of Bio-Si-NPs (2.5 and 5.0 mmol/L) and potassium silicate (10 mmol/L) as a foliar spray on the antioxidant defense system, physio-biochemical components, and the contaminants contents of Phaseolus vulgaris L. grown on saline soil contaminated with heavy metals. Our findings showed that all treatments of Bio-Si-NPs and potassium silicate significantly improved plant growth and production, chlorophylls, carotenoids, transpiration rate, net photosynthetic rate, stomatal conductance, membrane stability index, relative water content, free proline, total soluble sugars, N, P, K, Ca²⁺, K⁺/Na⁺, and the activities of peroxidase, catalase, ascorbic peroxidase and superoxide oxide dismutase. Application of Bio-Si-NPs and potassium silicate significantly decreased electrolyte leakage, malondialdehyde, H₂O₂, O₂^•-, Na⁺, Pb, Cd, and Ni in leaves and pods of Phaseolus vulgaris L. compared to control. Bio-Si-NPs were more effective compared to potassium silicate. Application of Bio-Si-NPs at the rate of 5 mmol/L was the recommended treatment to enhance the performance and reduce heavy metals content on plants grown on contaminated saline soils.

The Effect of Religious Dietary Cultures on Food Nitrogen and Phosphorus Footprints: A Case Study of India

The excessive consumption of nitrogen (N) and phosphorus (P), two vital nutrients for living organisms, is associated with negative environmental and health impacts. While food production contributes to a large amount of N and P loss to the environment, very little N and P is consumed as food. Food habits are affected by multiple regulations, including the dietary restrictions and dictates of various religions. In this study, religion-sensitive N-Calculator and P-Calculator approaches were used to determine the impact of religious dietary culture on the food N and P footprints of India in the major religious communities. Using 2013 data, the food N footprint of Hindus, Muslims, Christians, and Buddhists was 10.70, 11.45, 11.47, and 7.39 kg-N capita-1 year-1 (10.82 kg-N capita-1 year-1 was the national average), and the food P footprint was 1.46, 1.58, 1.04. and 1.58 kg-P capita-1 year-1 (1.48 kg-P capita-1 year-1 was the national average). The findings highlight the impact of individual choice on the N and P food footprints, and the importance of encouraging the followers of religion to follow a diet consistent with the food culture of that religion. The results of this study are a clear indication of the requirement for religion-sensitive analyses in the collecting of data pertinent to a particular country for use in making government policies designed to improve the recycling of food waste and the treatment of wastewater.

The nitrogen and phosphorus footprints of food products in Yemen over the last 57 years

Food nitrogen (N) and phosphorus (P) footprints are indicators for determining the losses of N and P over food production (FP) and food consumption (FC) chain. Yemen is an interesting case because, given the country's heavy dependence on food imports, food insecurity, and poverty, the N footprint (NF) and P footprint (PF) could affect its future development. However, NF and PF over time have not yet been studied in Yemen. Therefore, this is the first paper to compute the NF and PF in Arabian Peninsula (a case study from Yemen) by an adjusted model of N-Calculator, by computing virtual N (VNFs) and virtual P (VPFs) factors for main foodstuffs. The NF (kg N cap^-1 year^-1) and PF (kg P cap^-1 year^-1) elevated from 5.56 and 1.20 in the 1960s to 15.2 and 4.79 during 2011-2017, respectively, while the national NF (Gg [10⁹ g] N year^-1) and national PF (Gg P year^-1) increased from 27.7 and 6.77 in the 1960s to 358 and 122 during 2011-2017, respectively. Cereal was the largest contributor to the NF and PF in Yemen over the past 57 years. FP contributes approximately 80% and 86% of the total NF and PF during 2011-2017. Therefore, if possible, the best way for consumers and farmers in Yemen to decrease NF and PF is to focus efforts on increasing FP and FC of foodstuffs with less VNFs and VPFs. The consumption of vegetable-fruit, legumes, starchy, eggs, poultry, and fish should be increased as their NF and PF are low. However, people in Yemen suffer from shortage of resources and lack of awareness, and thus they do not have the opportunity to choose foodstuffs that are low in NF and PF. Accordingly, policymakers should encourage integrated approaches that introduce powerful tools for controlling crop and livestock production in conjunction with enhancements in nutrient use efficiency.

Mitigate nitrate contamination in potato tubers and increase nitrogen recovery by combining dicyandiamide, moringa oil and zeolite with nitrogen fertilizer

Potato is considered a nitrogen (N) intensive plant with a low N use efficiency (NUE). The current study introduced an excellent approach by combining dicyandiamide (DCD), moringa seed oil (MSO), or zeolite (ZE), with N fertilizer for maximizing potato tuber yields and NUE as well as minimizing tubers nitrate (NO₃^-) accumulation. The impact of these materials on soil N availability and gaseous emissions (NH₃, and N₂O) was investigated under incubation conditions. A 2-year field experiment were carried out with seven treatments [without N (control), N fertilizer (350 kg N-urea ha^-1 as a recommended dose; Urea_RD), 75% of N recommended dose with DCD (Urea_75%RD+DCD), Urea_75%RD with 2% MSO (Urea_75%RD+MSO_2%), Urea_75%RD with 4% MSO (Urea_75%RD+MSO_4%), Urea_75%RD with 0.5 Mg ZE ha^-1 (Urea_75%RD+ZE_R1), and Urea_75%RD with 1.0 Mg ZE ha^-1 (Urea _75%RD+ZE_R2)]. We also conducted a 40-days incubation trial with the same treatments; however, urea was added at the rate of 200 mg N kg^-1 soil for all treatments, excluding the control. The addition of DCD, MSO, and ZE with urea under incubation conditions delayed the nitrification process, thereby causing a rise in NH₄⁺-N content and a decrease in NO₃^--N content. Ammonia-oxidizing bacteria (AOB) was inhibited (p ≤ 0.01) in treatments Urea+DCD, Urea+MSO_4%, and Urea+ZE_R2. The highest NUE indexes were recorded in treatment Urea_75%RD+DCD. The highest NO₃^- accumulation (567 mg NO₃^- kg^-1) in potato tubers was recorded in treatment Urea_RD. Whilest, the lowest NO₃^- content (81 mg NO₃^- kg^-1) was in treatment Urea_75%RD+DCD. The lowest cumulative N₂O emissions and highest cumulative NH₃ volatilization were observed in the treatment Urea+DCD under incubation conditions. Our findings demonstrated that N fertilizer rate could be reduced by 25%, while the tuber yields increased with an acceptable limit of NO₃^- content, resulting in economical, agronomical, and environmental benefits.

The food nitrogen footprint for African countries under fertilized and unfertilized farms

Although nitrogen (N) is a limiting factor for food production (FP) in Africa, and African food security is seriously threatened by the phenomenon of soil N depletion, there is a dearth of information that shows the points to focus on throughout the chain of FP and food consumption (FC) in all African countries to minimize N loss while securing food N supply. Food N footprint (NF) is an indicator for tracing the losses of reactive N (Nr) with regard to the FP and FC chain. This is the first study to calculate the food NF for all African countries under fertilized and unfertilized farms, by calculating two sets of virtual N factors (VNFs; kg Nr released to the environment kg^-1 N in consumed product): one for unfertilized farms (the unfertilized scenario) and one for fertilized farms (the fertilized scenario). The fertilized and unfertilized VNFs were utilized to calculate a weighted average set of VNFs (the combined scenario). From the percentage of farms that utilize N fertilizer, and the N percentage in production that comes from soil depletion, the proportion used for the combined scenario was determined. Soil N depletion factors (SNDFs; kg N taken from the unfertilized soil kg^-1 N in food consumed) were also computed to identify the quantity of N extracted from the soil for food production. We have also provided the changes in N inputs, N outputs, and N use efficiency (NUE) for North Africa and Sub-Saharan Africa (SSA) during the last 57 years. The average total N input to croplands increased from 24 and 19 kg N ha^-1 yr^-1 in 1961-1965 to 100 and 42 kg N ha^-1 yr^-1 in 2010-2017 for North Africa and SSA, respectively. The NUE declined from 109% and 67% (1961-1965) to 47% and 63% (2010-2017) for North Africa and SSA, respectively. The total average per-capita food NF was 11 and 5.8 kg N cap^-1 yr^-1 in unfertilized farms; 21 and 14 kg N cap^-1 yr^-1 in fertilized farms; and 19 and 7.5 kg N cap^-1 yr^-1 under the combined scenario for North Africa and SSA, respectively. Vegetable-fruit and beef have the highest SDNFs in Africa. FP in Africa contributes approximately 70% of the total food NF. Therefore, if possible, the best way for Africans to reduce soil N depletion and N emissions is to encourage the production and consumption of livestock and crops products with less VNF and SNDF. However, African people do not have this luxury of choice because of poverty and ignorance. Therefore, African policy-makers must adopt integrated approaches that provide effective tools to control the production of animals and crops in conjunction with the improvement of NUE. Trying to completely change the African agricultural system is impossible, but strategies must be developed to reduce soil depletion in a gradual way, as well as a shift towards low-VNF foods.

Sub-Saharan Africa's food nitrogen and phosphorus footprints: A scenario analysis for 2050

The current study presents the first nitrogen (N) and phosphorus (P) footprints calculator for Sub-Saharan Africa during 1961-2017 using an adjusted N-Calculator model, by calculating two sets of virtual N factors (VNFs) or virtual P factors (VPFs): one for fertilized farms and one for unfertilized farms. We furthermore calculated the future food footprints of N (NF) and P (PF) under five scenarios include: 1) business as usual [BAU], 2) achieve an equitable diet (EqD) while the plant N and P uptake and all other food losses would be constant at 2017 level [S1], 3) follow the EqD without any changes in plant N and P uptake, but the current ratio of other food losses would increase by 50% [S2], 4) follow the EqD with a 5% less in plant N and P uptake than the current ratio, and the current ratio of other food losses would increase by 50% [S3], and 5) follow the EqD with a 10% greater in plant N and P uptake than the current ratio, while the current ratio of other food losses would decrease by 50% [S4]. NF (kg N cap^-1 yr^-1) and PF (kg P cap^-1 yr^-1) increased from 6.7 and 1.1 to 8.3 and 1.5 during 1961-2017, respectively. The national NF (Tg N yr^-1) and PF (Tg P yr^-1) increased from 1.6 and 0.26 to 7.7 and 1.4, respectively. In 2050, NF would be 9.7, 21.7, 24.1, 27.7, and 15.5 kg N cap^-1 yr^-1 for the BAU, S1, S2, S3, and S4 scenarios, respectively. While, PF would be 1.8, 5.1, 5.6, 7.3, and 3.0 kg P cap^-1 yr^-1, respectively. S4 scenario results in much less NF and PF. We suggest applying the S4 scenario with a change of dietary style by reducing the foods consumption with high VNFs and VPFs by 2050.

Bacillus subtilis biofertilizer mitigating agricultural ammonia emission and shifting soil nitrogen cycling microbiomes

Excessive ammonia (NH₃) emitted from nitrogen fertilizer application in farmland have caused serious disturbance to global environment, including reduction of visibility, formation of regional haze, and increase of nitrogen deposition. Application of biofertilizer has been considered as an effective approach for soil improvement and agriculture sustainability. In this study, a field experiment was conducted to evaluate the potential of B. subtilis biofertilizer on mitigating NH₃ volatilization and to investigate the underlying mechanisms. Compared with organic fertilizer, the incorporation of B. subtilis biofertilizer reduced NH₃ volatilization by up to 44%. Moreover, the application of B. subtilis biofertilizer reduced the abundance of ureC gene, and increased the abundance of functional genes (bacterial amoA and comammox amoA) and ammonia-oxidizing bacteria (AOB). This indicated that the conversion of fertilizer nitrogen to NH₄⁺-N was decreased and the nitrification process was increased. In brief, the application of B. subtilis biofertilizer reduced the "source" and increased the "sink" of NH₄⁺-N, thus reducing the retention of NH₄⁺-N in alkaline soil, and mitigating NH₃ volatilization. These results indicated that B. subtilis biofertilizer is an effective control strategy for agricultural NH₃ emission, maintaining high crop yield and mitigating environmental disturbance.

How much nitrogen does Africa need to feed itself by 2050?

Nitrogen (N) fertilizers are very important for global food self-sufficiency (FSS), particularly for Africa, where the N input in agriculture is very low. This is the first work which studies and calculates the amount of N fertilizer that each country in Africa needs to feed itself by 2050. In this study, we used five different scenarios of inorganic fertilizer N (IFN) use and human diets to calculate the amount of N fertilizer needed to achieve FSS in Africa by 2050 and analyze the changes in N budget; N losses and N use efficiency (NUE). These scenarios include 1) business as usual (BAU), 2) equitable diet (EqD; self-sufficiency), 3) an IFN input 20% less than the EqD (S1), 4) an IFN input 40% less than the EqD (S2), and 5) a 20% increase in IFN input relative to the EqD (S3). Under the BAU scenario, production trends continue as they have over the past five decades, including an unhealthy human diet. In the EqD scenario, the priority is to meet the local demand for both animal and plant proteins with a healthy human diet. Under the EqD scenario, increasing the total N input from 35 kg N ha^-1 yr^-1 to 181 kg N ha^-1 yr^-1 during 2016-2050 is needed to achieve FSS in Africa. This increase in N fertilizer use represents unprecedented N inputs to African terrestrial ecosystems - at least 52 Tg N yr^-1 - which would lead to inevitable increases in N losses. We also found that the NUE would decrease from 63% during 2010-2016 to 50% by 2050, whereas the total N surplus would increase from 13 kg N ha^-1 yr^-1 to 90 kg N ha^-1 yr^-1 by 2050. The estimated gaseous emissions would increase from 8 kg N ha^-1 yr^-1 to 61 kg N ha^-1 yr^-1 by 2050. Our findings conclude that, it is very important to consider the high N losses in Africa if the EqD scenario is applied. The S1 and S2 scenarios result in much less environmental N loss, and better NUE compared with the EqD scenario. Therefore, based on these findings we can recommend the implementation of the S2 scenario with an IFN dose of 77 kg N ha^-1 yr^-1, in parallel with the use of modern agricultural techniques and the increased use of organic inputs.

Sustainable Development in the Agri-Food Sector in Terms of the Carbon Footprint: A Review

The concept of sustainable development is increasingly important in the agri-food sector and global economy. International activities are undertaken to improve the efficiency of industry by reducing its negative impact on the environment. To help determine harmful human activity, the environmental footprints of products and services are calculated using the LCA (life cycle assessment) method. The purpose of this article was to explain topics of sustainable development and environmental footprints, especially the carbon footprint in the agri-food sector, based on the latest literature. The agri-food industry consumes around 30% of global energy demand. It is also a source of emissions of a significant part of greenhouse gases released into the environment. The carbon footprint of food products is determined by many factors associated with their production. Food of animal origin is more harmful and has higher carbon footprints than plant-based products. GHG emission reduction is possible due to the use of renewable energy sources and the abandonment of the use of artificial fertilizers and plant protection products.

Can secondary metabolites extracted from Moringa seeds suppress ammonia oxidizers to increase nitrogen use efficiency and reduce nitrate contamination in potato tubers?

Nitrification inhibition as an alleviation tool to decrease nitrogen (N) losses and increase N use efficiency (NUE) as well as reducing NO₃^- accumulation in plants is a promising technology. No study thus far has directly or indirectly to use the secondary metabolites extracted from Moringa (Moringa oleifera Lam) seeds as nitrification inhibitors. Moringa seed extract (MSE) was studied based on its content of phenolic compounds (PC) and for its antioxidant characteristic. A 2-year field experiment and 30-day incubation experiment were conducted with three treatments of control (CK), N fertilizer (300 kg N ha^-1 and 200 mg N kg^-1 soil for the field and incubation experiment, respectively), and N fertilizer with MSE (500 ppm as a TPC) to investigate the responses of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to MSE and the consequences for NUE and NO₃^- accumulation in potato tubers. Total phenolics amount was 144 mg gallic acid equivalent g^-1 MSE, while flavonoid contents were 76.6 quercetin equivalent g^-1 MSE. MSE showed antioxidant activity that was comparable to the standard antioxidants TBHQ and gallic acid. MSE application with N fertilizer retarded the nitrification process, as indicated by a higher NH₄⁺-N and lower NO₃^--N content, compared with N fertilizer application alone. NH₄⁺-N content reduced to initial CK level on Day 20 under N fertilizer application alone. However, NH₄⁺-N content decreased to initial control level on Day 30 when MSE was applied. The mechanisms resulted from curbing AOB growth by phenolic compounds (TPC, TF, TAC), leading to a delay in nitrification process. AOB increased significantly when N fertilizer was applied alone; on the contrary, AOA was not sensitive to N fertilizer (with and without MSE). Increase in NUE from 37.5% to 66.3% in potato plants under MSE application with N fertilizer was also observed compared with N fertilizer application alone. The highest NO₃^- accumulation (569 mg NO₃^- kg^-1) in tubers was recorded under N fertilizer application without MSE. MSE application significantly decreased NO₃^- accumulation (92 mg NO₃^- kg^-1) in tubers which is lower than the maximum value of accepting tubers (200 mg NO₃^- kg^-1). The highest average of N uptake, fresh and dry weight, carotenoids, chlorophyll a, chlorophyll b and nitrate reductase activity was recorded when MSE was applied with N fertilizer. Accordingly, using of Moringa extracted secondary metabolites to suppress AOB growth in the soil is a significant strategy to reduce nitrification rate and N loss from soils, and therefore increase NUE as well as reducing NO₃^- accumulation in potato tubers.