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

Harnessing the potential of ginkgo biloba extract: Boosting denitrification performance through accelerated electron transfer

Ginkgo biloba extract (GBE) had several effects on the human body as one of the widely used phytopharmaceuticals, but it had no application in microbial enhancement in the environmental field. The study focused on the impact of GBE on denitrification specifically under neutral conditions. At the identified optimal addition ratio of 2% (v/v), the system exhibited a noteworthy increase in nitrate reduction rate (NRR) by 56.34%, elevating from 0.71 to 1.11 mg-N/(L·h). Moreover, the extraction of microbial extracellular polymeric substance (EPS) at this ratio revealed changes in the composition of EPS, the electron exchange capacity (EEC) was enhanced from 87.16 to 140.4 μmol/(g C), and the transfer impedance was reduced within the EPS. The flavin, fulvic acid (FA), and humic acid (HA) provided a π-electron conjugated structure for the denitrification system, enhancing extracellular electron transfer (EET) by stimulating carbon source metabolism. GBE also improved electron transfer system activity (ETSA) from 0.025 to 0.071 μL O2/(g·min·prot) and the content of NADH enhanced by 22.90% while significantly reducing the activation energy (Ea) by 85.6% in the denitrification process. The synergy of improving both intracellular and extracellular electron transfer, along with the reduction of Ea, notably amplified the initiation and reduction rates of the denitrification process. Additionally, GBE demonstrated suitability for denitrification across various pH levels, enhancing microbial resilience in alkaline conditions and promoting survival and proliferation. Overall, these findings open the door to potential applications of GBE as a natural additive in the environmental field to improve the efficiency of denitrification processes, which are essential for nitrogen removal in various environmental contexts.

Plant growth-promoting microorganisms as biocontrol agents of plant diseases: Mechanisms, challenges and future perspectives

Plant diseases and pests are risk factors that threaten global food security. Excessive chemical pesticide applications are commonly used to reduce the effects of plant diseases caused by bacterial and fungal pathogens. A major concern, as we strive toward more sustainable agriculture, is to increase crop yields for the increasing population. Microbial biological control agents (MBCAs) have proved their efficacy to be a green strategy to manage plant diseases, stimulate plant growth and performance, and increase yield. Besides their role in growth enhancement, plant growth-promoting rhizobacteria/fungi (PGPR/PGPF) could suppress plant diseases by producing inhibitory chemicals and inducing immune responses in plants against phytopathogens. As biofertilizers and biopesticides, PGPR and PGPF are considered as feasible, attractive economic approach for sustainable agriculture; thus, resulting in a "win-win" situation. Several PGPR and PGPF strains have been identified as effective BCAs under environmentally controlled conditions. In general, any MBCA must overcome certain challenges before it can be registered or widely utilized to control diseases/pests. Successful MBCAs offer a practical solution to improve greenhouse crop performance with reduced fertilizer inputs and chemical pesticide applications. This current review aims to fill the gap in the current knowledge of plant growth-promoting microorganisms (PGPM), provide attention about the scientific basis for policy development, and recommend further research related to the applications of PGPM used for commercial purposes.

Genotoxicity assessment of amino zinc nanoparticles in wheat (Triticum aestivum L.) as cytogenetical perspective

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Using and impact of nanoparticles in agriculture.

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Genotoxicity of nanoparticles in plant.

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Effect of commercial amino zinc nanoparticles on cell division.

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The harmful effect of commercial amino zinc nanoparticles in chromosomal structure.

Nanoparticles have a positive impact in several subjects especially in agriculture, while their safety is still being debated. Numerous commercial nano pesticide, insecticides, and fertilizers products are found in the local markets without any intensely studies on the side effect of these products on plant, human as well as environmental effects. The present study aimed to evaluate the genotoxicity of commercial amino zinc nanoparticles (AZ NPs) on Triticum aestivum L. during seeds germination and root elongation using concentration ranges (50, 100, and 150 ppm) at different exposure times (8, 16 and 24 hrs). Long term exposure to AZ NPs, exhibited only slight variation in germination rates and the elongation of roots was affected by AZ NPs treatment ranged from 97.66 to 100%. Significant reduction in the mitotic index was 35.33% after 24 hrs and 150 ppm of AZ NPs, was also observed comparing with control which was 88.0%. Genotoxicity was evaluated at a cytological level in root meristems that revealed sever variations in mitotic activity, chromosomal aberrations, and micronuclei release. Results exhibited that nano amino zinc could enter effortlessly into the cells and inhibit the normal cellular function. The decrease in the emergence of chromosomal aberrations resulting from AZ NPs exposure in a dose-dependent manner was clearly indicated that AZ NPs has induced genotoxic effect on wheat root tips.

Inheritance of resistance against northern leaf blight of maize using conventional breeding methods

Maize (Zea mays L.) is one of the important cereal crops along with wheat and rice worldwide. The purpose of this study was to use classical genetic approaches to assess the resistance of various maize parents and hybrids to the northern corn leaf blight (NCLB) disease in two different locations in Egypt. Eight parents, 28 F1, and 2 check hybrids were evaluated. The analysis of variance showed high significant variations between maize parents and their hybrids for the studied parameters and NCLB disease, besides there are significant variations between both locations. Results of maize parents showed that Sids 63, Giza 602, and Giza 628 cultivars exhibited the highest values and were resistant to NCLB in both locations comparing with Nubaria 39 and Gemmiza 18 that were susceptible to NCLB disease. Concerning the maize hybrids, analysis of variance and mean squares of growth characters in both locations indicated high significant variations between the maize hybrids including the check hybrids. When combined between the two locations for current parameters against NCLB, the data pointed that the Sakha location values for maize hybrids were much closed to the combining data in parents and the hybrids detected high resistance to this disease comparing with Nubaria location. All tested maize lines (38 lines), including parents and hybrids were classified as follows, two lines were rated as 1 (highly resistant), three were rated as 2 (resistant), sixteen were rated as 3 (moderate resistant), eight were rated 4 (moderately susceptible) and nine were rated 5 (susceptible). The data explaining that the crossing between high resistant maize cultivars produced high levels of resistance to NCLB disease. Therefore, our results verified that classical breeding could efficiently increase the resistance levels of maize germplasm against NCLB disease by developing new cultivars with superior performance in terms of grain yield, disease resistance and grain quality.

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.

Improving growth and productivity of faba bean (Vicia faba L.) using chitosan, tryptophan, and potassium silicate anti-transpirants under different irrigation regimes

This work aims to study the effect of foliar spraying of three anti-transpirants i.e., A­₁: tryptophan (Tri), A₂: potassium silicate (KS), A₃: chitosan (Chi) as well as A₀: control (Tap water) under three irrigation regimes, I₁: 2400, I₂: 3600, and I₃: 4800 m³ha⁻¹ on the quality and production of faba bean crop and its nutrient contents. The study was carried out during two successive winter seasons of 2018/2019 and 2019/2020. Drought stress affected the average performance of all studied traits as it reduced seed yield and traits, as a result of the decrease in chlorophyll related to photosynthesis, protein, carbohydrates, total phenols, amino acids, macronutrients (N, P, and K), micronutrient contents (Fe, Mn, and Zn) and their absorption. The single foliar spraying of faba bean with tryptophan 75 ppm, potassium silicate at 100 ppm, or chitosan at 750 ppm significantly increased all studied traits and reduced the drought stress compared to control under different irrigation systems. We recommended using a foliar spray of chitosan (750 ppm) on faba bean plants under an irrigation level of 4800 m³ led to an improvement in the physiological properties of the plant, i.e., plant height, the number of branches/plants, and the number of plants, pods plant⁻¹, the number of seed pods⁻¹, the weight of 100 seeds and seed yield ha⁻¹ increased with relative increase about 42.29, 89.47, 28.85, 75.91, 24.43, and 306.48% compared to control. The quality properties also improved, as the total chlorophyll, protein, carbohydrates, total phenols, and amino acids were higher than the control with a relative increase of 63.83, 29.58, 27.72, 37.54, and 64.19%. Additionally, an increase in the contents and uptake of macronutrients (N, P, and K), and micronutrients (Fe, Mn, Zn) and their absorption. The increase was estimated with 29.41, 75.00, 16.56, 431.17, 630.48, 72.68%, 22.37, 35.69, 42.33, 397.63, 452.58, and 485.94% about the control. This was followed by potassium silicate (100 ppm), then tryptophan (75 ppm) compared to the control, which recorded the minimum values ​​in plant traits.

Biological silicon nanoparticles maximize the efficiency of nematicides against biotic stress induced by Meloidogyne incognita in eggplant

Nemours effective management tactics were used to reduce world crop losses caused by plant-parasitic nematodes. Nowadays the metallic nanoparticles are easily developed with desired size and shape. Nanoparticles (NPs) technology becomes a recognized need for researchers. Ecofriendly and biosafe SiNPs are developed from microorganisms. Recently, silicon nanoparticles (SiNPs) have gained novel pesticide properties against numerous agricultural pests. This study assessed the biosynthesis of SiNPs from Fusarium oxysporum SM5. The obtained SiNPs were spherical with a size of 45 nm and a negative charge of -25.65. The nematocidal effect of SiNPs against egg hatching and second-stage juveniles (J2) of root-knot nematode (RKN) (Meloidogyne incognita) was evaluated on eggplant,Solanum melongena L. plants. In vitro, all tested SiNPs concentrations significantly (p ≤ 0.05) inhibited the percentage of egg hatching at a different time of exposure than control. Meanwhile, after 72 h, the percent mortality of J2 ranged from 87.00 % to 98.50 %, with SiNPs (100 and 200 ppm). The combination between SiNPs and the half-recommended doses (0.5 RD) of commercial nematicides namely,  fenamiphos (Femax 40 % EC)R, nemathorin (Fosthiazate 10 % WG) R, and fosthiazate (krenkel 75 % EC) R confirmed the increase of egg hatching inhibition and J2 mortality after exposure to SiNPs (100 ppm) mixed with 0.5 RD of synthetic nematicides. The findings suggest that the combination between SiNPs, and 0.5 RD of nematicides reduced nematode reproduction, gall formation, egg masses on roots and final population of J2 in the soil. Therefore, improving the plant growth parameters by reducing the M. incognita population.

Impact of Exogenously Sprayed Antioxidants on Physio-Biochemical, Agronomic, and Quality Parameters of Potato in Salt-Affected Soil

Salinity is one of the harsh environmental stresses that destructively impact potato growth and production, particularly in arid regions. Exogenously applied safe-efficient materials is a vital approach for ameliorating plant growth, productivity, and quality under salinity stress. This study aimed at investigating the impact of foliar spray using folic acid (FA), ascorbic acid (AA), and salicylic acid (SA) at different concentrations (100, 150, or 200 mg/L) on plant growth, physiochemical ingredients, antioxidant defense system, tuber yield, and quality of potato (Solanum tuberosum L cv. Spunta) grown in salt-affected soil (EC = 7.14 dS/m) during two growing seasons. The exogenously applied antioxidant materials (FA, AA, and SA) significantly enhanced growth attributes (plant height, shoot fresh and dry weight, and leaves area), photosynthetic pigments (chlorophyll a and b and carotenoids), gas exchange (net photosynthetic rate, Pn; transpiration rate, Tr; and stomatal conductance, gs), nutrient content (N, P, and K), K+/ Na+ ratio, nonenzymatic antioxidant compounds (proline and soluble sugar content), enzymatic antioxidants (catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), and ascorbate peroxidase (APX)) tuber yield traits, and tuber quality (dry matter, protein, starch percentage, total carbohydrates, and sugars percentage) compared with untreated plants in both seasons. Otherwise, exogenous application significantly decreased Na+ and Cl- compared to the untreated control under salt stress conditions. Among the assessed treatments, the applied foliar of AA at a rate of 200 mg/L was more effective in promoting salt tolerance, which can be employed in reducing the losses caused by salinity stress in potato grown in salt-affected soils.

Immunological effect of Moringa Oleifera leaf extract on vaccinated and non-vaccinated Hubbard chickens experimentally infected with Newcastle virus

In veterinary medicine plant based medicine is achieving a huge importance worldwide. This research was subjected to rectify the hydrophilic Moringa Oleifera alcoholic leaves extract could improve the immune system in vaccinated and non-vaccinated broiler Hubbard chickens experimentally exposed to Newcastle disease (ND) virus. Seventy five chicks with age one day old were splitted randomly into five groups equally in distribution with fifteen chick in each group. Group I was untreated unvaccinated (control negative group) while group IV was infected group with NDV (control positive group). The experimental Groups II and V were given daily oral treatment of hydrophilic alcoholic leaves extract of M. oleifera at 200 mg/kg body weight until day 21 of age while groups III and V were ND vaccinated with La Sota strain of ND vaccines. The four groups (II, III, IV, V) were infected with ND virus velogenic strain (VNDV) on day 21. Following to infection, Monitoring of birds were done daily for clinical signs, postmortem examination, morbidity and mortality. Cellular, humeral immune response and phagocytic activity were evaluated and the data were statistically analyzed using (SPSS). Total and differential cell numbers as well as Haemagglutination inhibition (HI) titre increased in the extract treated and vaccinated group which give total protection against NDV much more than treated and unvaccinated group. As a result it could be recommended to use M. Olifera extract from the first day of rearing in Hubbard chicken with ND vaccination program as a prophylactic treatment in protection of birds against ND infection.

Enhancement of drought tolerance in diverse Vicia faba cultivars by inoculation with plant growth-promoting rhizobacteria under newly reclaimed soil conditions

Water deficit has devastating impacts on legume production, particularly with the current abrupt climate changes in arid environments. The application of plant growth-promoting rhizobacteria (PGPR) is an effective approach for producing natural nitrogen and attenuating the detrimental effects of drought stress. This study investigated the influence of inoculation with the PGPR Rhizobium leguminosarum biovar viciae (USDA 2435) and Pseudomonas putida (RA MTCC5279) solely or in combination on the physio-biochemical and agronomic traits of five diverse Vicia faba cultivars under well-watered (100% crop evapotranspiration [ETc]), moderate drought (75% ETc), and severe drought (50% ETc) conditions in newly reclaimed poor-fertility sandy soil. Drought stress substantially reduced the expression of photosynthetic pigments and water relation parameters. In contrast, antioxidant enzyme activities and osmoprotectants were considerably increased in plants under drought stress compared with those in well-watered plants. These adverse effects of drought stress reduced crop water productivity (CWP) and seed yield‐related traits. However, the application of PGPR, particularly a consortium of both strains, improved these parameters and increased seed yield and CWP. The evaluated cultivars displayed varied tolerance to drought stress: Giza-843 and Giza-716 had the highest tolerance under well-watered and moderate drought conditions, whereas Giza-843 and Sakha-4 were more tolerant under severe drought conditions. Thus, co-inoculation of drought-tolerant cultivars with R. leguminosarum and P. putida enhanced their tolerance and increased their yield and CWP under water-deficit stress conditions. This study showed for the first time that the combined use of R. leguminosarum and P. putida is a promising and ecofriendly strategy for increasing drought tolerance in legume crops.

Impact of wastewater discharge on the plant diversity, community structure and heavy metal pollution of range plants in eastern Saudi Arabia

The main objectives of this study were to determine the floristic composition of the vegetation cover and to find the effects of wastewater pollution on the plant community structure in eastern Saudi Arabia. 28 stands which were distributed among polluted and unpolluted sites, were chosen for this study. A total of 42 plant species were recorded (14 in the polluted and 28 in the unpolluted sites). The recorded plants comprised of 13 perennial plant species and 29 annual plant species. Seven vegetation communities were determined using TWINSPAN and DCA classification and ordination techniques. Three in the polluted sites, two in the unpolluted sites and the remaining two were mixed communities. The (Sarcopoterium spinosum – Pistacia len‐tiscus) community in the polluted sites, had the highest values of soil moisture, salinity, sulphate, calcium and potassium. On the other hand, Juniperus phoenicea – Olea europaea community in the unpolluted site, had the lowest value of organic matter, salinity and magnesium. In respect of genetic diversity, the community of Foeniculum vulgare - Nicotiana glauca in the unpolluted site, was the most diverse, while Ricinus communis - Chrysanthemum coronarium in the polluted sites was the least one. Both soil and wastewater heavy metal analysis indicated that Pb, Cd, Cr, Cu and Ni concentrations in the polluted sites were significantly higher than those in the unpolluted ones. The impact of wastewater discharge led to the appearance of new invasive plant species that may significantly affect plant diversity and community structure in eastern Saudi Arabia. Finally wastewater discharge in open rangelands could adversely affect the growth of plant species in the rangelands and thus adversely affect plant community structure and diversity.

Callus induction and regeneration in sugarcane under drought stress

Tissue culture methods are useful in assessing the tolerance of various stresses due to the ease of controlling stress under in vitro conditions. This study aimed to investigate the response of sugarcane genotyps to drought stress using calli as a model system. For inducing sugarcane callus, the medium of Murashige and Skoog (MS) was used with different mannitol concentrations (100, 200, and 300 mM) to measure their effects on callus frequency, the day of callus initiation, embryogenic potential, relative growth rate (RGR), water and proline contents, K+ and Na+ contents, as well as the formation of shoot and roots for three sugarcane genotypes (e.g., GT 54-9, G 84-47, and pH 8013). The RAPD-PCR analysis was carried out using five oligonucleotide primers to identify the genetic variation among sugarcane genotypes. The results indicated that the degree of callus proliferation varied from 70 - 86%. The highest value of callus proliferation, PGR, shoot formation was recorded for the genotype GT 54-9 compared to the other two genotypes (G 84-47 and pH 8013). Calli treated with 100 mM mannitol showed the highest RGR, proline and waer contents for the genotype GT 54-9, while, those treated with 300 mM recorded the lowest values of these parameters for the genotype pH 8013. The genotype G 84-47 collected highest Na+ content, while the genotype pH 8013 collected highest K+ content. The results of this study recommend preference for GT 54-9 genotype, which is considered the most promising genotype, showing more tolerance to drought stress based on all studied traits.

Intensive vegetable production results in high nitrate accumulation in deep soil profiles in China

A comprehensive understanding of the patterns and controlling factors of nitrate accumulation in intensive vegetable production is essential to solve this problem. For the first time, the national patterns and controlling factors of nitrate accumulation in soil of vegetable systems in China were analysed by compiling 1262 observations from 117 published articles. The results revealed that the nitrate accumulation at 0-100 cm, 100-200 cm, 200-300 cm, and >300 cm were 504, 390, 349, and 244 kg N ha^-1, with accumulation rates of 62, 54, 19, and 16 kg N ha^-1 yr^-1 for plastic greenhouse vegetables (PG); for open field vegetables (OF), they were 264, 217, 228, and 242 kg N ha^-1 with accumulation rates of 26, 24, 18, and 10 kg N ha^-1 yr^-1, respectively. Nitrate accumulation at 0-100 cm, 0-200 cm, and 0-400 cm accounted for 5%, 11%, and 17% of accumulated nitrogen (N) inputs for PG, and represented 4%, 9%, and 13% of accumulated N inputs for OF. Nitrogen input rates and soil pH had positive effects and soil organic carbon, water input rate, and carbon to nitrogen ratio (C/N) had negative effects on nitrate accumulation in root zone (0-100 cm soil). Nitrate accumulation in deep vadose zone (>100 cm soil) was positively correlated with N and water input rates, and was negatively correlated with soil organic carbon, C/N, and the clay content. Thus, for a given vegetable soil with relatively stable soil pH and soil clay content, reducing N and water inputs, and increasing soil organic carbon and C/N are effective measures to control nitrate accumulation.

Effects of biological nitrification inhibitors on nitrogen use efficiency and greenhouse gas emissions in agricultural soils: A review

To maintain and increase crop yields, large amounts of nitrogen fertilizers have been applied to farmland. However, the nitrogen use efficiency (NUE) of chemical fertilizer remains very low, which may lead to serious environmental problems, including nitrate pollution, air quality degradation and greenhouse gas (GHG) emissions. Nitrification inhibitors can alleviate nitrogen loss by inhibiting nitrification; thus, biological nitrification inhibition by plants has gradually attracted increasing attention due to its low cost and environmental friendliness. Research progress on BNI is reviewed in this article, including the source, mechanisms, influencing factors and application of BNIs. In addition, the impact of BNI on agriculture and GHG emissions is summarized from the perspective of agricultural production and environmental protection, and the key future research prospects of BNIs are also noted.

The inhibition effect of tea polyphenols on soil nitrification is greater than denitrification in tea garden soil

Tea polyphenols are the most widely distributed class of secondary metabolites (Camellia sinensis) and account for a considerable proportion of the pruning residues of tea. A large amount of tea polyphenols have fallen down over soil with prunning residues every year. However, the effect of tea polyphenols on soil nitrogen cycle, especially the denitrification process and its related microbial communities, remains unclear. Epigallocatechin gallate (EGCG), the most abundant component of tea polyphenols, was selected to simulate the effects of tea polyphenols on soil nitrification, denitrification, related functional genes and microbial community. The results indicated that addition of EGCG can significantly (p < 0.05) inhibit soil nitrification. Copy numbers of bacterial and archaeal ammonia monooxygenase genes (amoA) decreased as EGCG concentration increased. Further, the ammonia oxidisers exhibited a significantly (p < 0.05) greater niche differentiation under the effect of EGCG compared with the control treatment (no EGCG addition). However, the inhibition effect of EGCG over soil denitrification was most significant at 34 and 36 day of incubation period, and such inhibitory effect was more apparent on nitrification compared with denitrification. EGCG addition increased the diversity of bacterial community. The composition of bacterial community was significantly altered and community variation was primary explained by EGCG, NH₄⁺-N, NO₃^--N, soil organic carbon contents and potential denitrification rates. EGCG addition significantly increased relative abundance of Proteobacteria and Bacteroidetes phyla whereas decreased Actinobacteria. Overall, tea polyphenols can inhibit soil nitrification to a larger extent than denitrification by reducing the abundance of microorganisms carrying the related functional genes. Our results can serve as important basis of reducing the nitrogen pollution risk in tea orchards and could be considered as a powerful natural nitrification inhibitor to reduce the environmental risks caused by unreasonable nitrogen fertiliser adaptation.

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.

Do soil property variations affect dicyandiamide efficiency in inhibiting nitrification and minimizing carbon dioxide emissions?

Nitrification inhibitors (NIs) are used to retard the nitrification process and reduce nitrogen (N) losses. However, the effects of soil properties on NI efficacy are less clear. Moreover, the direct and indirect effects of soil property variations on NI efficiency in minimizing carbon dioxide (CO₂) emissions have not been previously studied. An incubation experiment was conducted for 40 days with two treatments, N (200 mg N-urea kg^-1) and N + dicyandiamide (DCD) (20 mg DCD kg^-1), and a control group (without the N) to investigate the response of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to DCD application and the consequences for CO₂, nitrous oxide (N₂O) and ammonia (NH₃) emissions from six soils from the Loess Plateau with different properties. The nitrification process completed within 6-18 days for the N treatment and within 30->40 days for the N + DCD treatment. AOB increased significantly with N fertilizer application, while this effect was inhibited in soils when DCD was applied. AOA was not sensitive to N fertilizer and DCD application. The nitrification rate was positively correlated with the clay (p < 0.05) and SOM contents (p < 0.01); DCD was more effective in loam soil with low SOM and high soil pH. Soil pH significantly was decreased with N fertilizer application, while it increased when DCD was applied. Moreover, DCD application decreased CO₂ emissions from soils by 22%-172%; CO₂ emissions were negatively correlated with the clay and SOM contents. DCD application decreased N₂O emissions in each soil by 1.0- to 94-fold compared with those after N fertilizer application. In contrast, DCD application increased NH₃ release from soils by 59-278%. NH₃ volatilization was negatively correlated with clay (p < 0.05) and SOM (p < 0.01) contents and positively correlated with soil pH (p < 0.01). Therefore, soil texture, SOM and soil pH have significant effects on the DCD performance, nitrification process and gaseous emissions.

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.

The Structure and Diversity of Nitrogen Functional Groups from Different Cropping Systems in Yellow River Delta

The Yellow River Delta (YRD) region is an important production base in Shandong Province. It encompasses an array of diversified crop systems, including the corn-wheat rotation system (Wheat-Corn), soybean-corn rotation system (Soybean-Corn), fruits or vegetables system (Fruit), cotton system (Cotton) and rice system (Rice). In this study, the communities of ammonia oxidizer-, denitrifier- and nitrogen (N)-fixing bacteria in those cropping systems were investigated by Illumina Miseq sequencing. We found that Rice soil exhibited significantly higher diversity indices of investigated N-cycling microbial communities than other crop soils, possibly due to its high soil water content. Wheat-Corn soils had higher abundances of nitrification gene amoA and denitrification genes nirK and nirS, and exhibited higher soil potential nitrification rate (PNR), compared with Soybean-Corn, Cotton and Fruit soils. Consistently, redundancy analysis (RDA) showed that soil water content (SWC), electrical conductivity (EC), and total nitrogen (TN) were the most important influencing factors of the diversity and structure of the investigated N-cycling microbial.