Search Results (446)

Soybean (Glycine max [L.] Merr.) cultivation is expanding in Central Europe due to the development of early-maturing cultivars and growing demand for plant-based protein produced without the use of genetically modified organisms. However, nitrogen (N) management remains a major challenge in temperate climates, where variable weather conditions can significantly affect nodulation and yield. This study evaluated the effects of three nitrogen fertilisation doses (0, 30, and 60 kg N·ha⁻¹), applied in the form of ammonium nitrate (34% N) and two commercial rhizobial inoculants—HiStick Soy (containing Bradyrhizobium japonicum strain 532C) and Nitragina (including a Polish strain of B. japonicum)—on nodulation, nitrogen uptake, and seed yield. A three-year field experiment (2017–2019) was conducted in southwestern Poland using a two-factor randomized complete block design. Nodulation varied significantly across years, with the highest values recorded under favourable early-season moisture and reduced during drought. In the first year, inoculation with HiStick Soy significantly increased nodule number and seed yield compared to Nitragina and the uninoculated control. Nitrogen fertilisation consistently improved seed yield, although it had no significant effect on nodulation. The highest nitrogen use efficiency was observed with moderate nitrogen input (30 kg N·ha⁻¹) combined with inoculation. These findings highlight the importance of integrating effective rhizobial inoculants with optimized nitrogen fertilisation to improve soybean productivity and nitrogen efficiency under variable temperate climate conditions. Full article

Soil organic nitrogen (SON) positively influences crop productivity, greenhouse gas (GHG) emissions, and sustained nitrogen (N) supply. Herein, we observed the effect of different treatments; no fertilizers (CK), chemical fertilizers (nitrogen, phosphorus, and potassium (NPK)), organic manure, and NPK + OM (NPKOM). This study was performed in a randomized complete block design (RCBD) with three replications. The results indicated that NPKOM treatment significantly decreased the nitrous oxide (N₂O) emissions by 19.97% and 17.47% compared to NPK in both years. This was linked with improved soil nutrient availability, soil organic carbon, soil organic nitrogen (SON) storage (10.06% and 12.38%), SON sequestration (150% and 140%), increased soil particulate (44.11% and 44%), and mineral-associated organic N (26.98% and 26.47%) availability. Furthermore, NPKOM also enhanced nitrate reductase (NR: 130% and 112%), glutamine synthetase (GS: 93% and 88%), sucrose phosphate synthase (SPS: 79% and 98%), SSs (synthetic direction; 57% and 50%), and decreased SSs activity in the decomposition direction (18% and 21%). This, in turn, inhibited the decomposition of sucrase and enhanced starch conversion into carbohydrates, thus leading to an increase in rice yield and a decrease in N₂O emissions. All fertilizations, particularly NPKOM, significantly enhanced grain protein contents by increasing N uptake and its availability. Therefore, NPKOM is an effective practice to enhance rice productivity, and SON sequestration and mitigate the N₂O emissions and subsequent climate change. Full article

This study examined the effects of both nitrogen (N) rate and form on the growth, nutrient uptake, and quality parameters of hydroponically grown purslane (Portulaca oleracea L.) during a spring cultivation cycle. Purslane was cultivated in a floating hydroponic system under either adequate or limiting N conditions. More specifically, under adequate N conditions, plants were supplied with NS where ammonium nitrogen (NH₄-N) accounted for either 7% (Nr7) or 14% (Nr14) of the total-N. The limiting N conditions were achieved through the application of either an NS where 30% of N inputs were compensated with Cl (N30), or an NS where 50% of N inputs were balanced by elevating Cl and S by 30% and 20%, respectively (N50). The results demonstrated that mild N stress enhanced the quality characteristics of purslane without significant yield losses. However, further and more severe N restrictions in the NS resulted in significant yield losses without improving product quality. The highest yield reduction (20%) occurred under high NH₄-N supply (Nr14), compared to Nr7-treated plants, which was strongly associated with impaired N assimilation and reduced biomass production. Both N-limiting treatments (N30 and N50) effectively reduced nitrate accumulation in edible tissues by 10% compared to plants grown under adequate N supply (Nr7 and Nr14); however, nitrate levels remained relatively high across all treatments, even though the environmental conditions of the experiment favored nitrate reduction. All applied N regimes and compensation strategies improved the antioxidant and flavonoid content, with the highest antioxidant activity observed in plants grown under high NH₄-N application, indirectly revealing the susceptibility of purslane to NH₄-N-rich conditions. Overall, the form and rate of N supply significantly influenced both plant performance and biochemical quality. Partial replacement of N with Cl (N30) emerged as the most promising strategy, benefiting quality traits and effectively reducing nitrate content without significantly compromising yield. Full article

Soil degradation and declining fertility threaten sustainable agriculture and crop productivity. This study evaluates the effects of CFMI-8, a co-fermented microbial inoculant comprising eight bacterial strains selected through genomic and metabolic modeling, on soil health, nutrient availability, and corn performance. Conducted in a randomized complete block design at Findlay Farm, Wisconsin, the field trial assessed soil biological activity, nutrient cycling, and crop yield responses to CFMI-8 treatment. Treated soils exhibited significant increases in microbial organic carbon (+224.1%) and CO₂ respiration (+167.1%), indicating enhanced microbial activity and organic matter decomposition. Improvements in nitrate nitrogen (+20.2%), cation exchange capacity (+23.1%), and potassium (+27.3%) were also observed. Corn yield increased by 28.6%, with corresponding gains in silage yield (+9.6%) and nutritional quality. Leaf micronutrient concentrations, particularly iron, manganese, boron, and zinc, were significantly higher in treated plants. Correlation and Random Forest analyses identified microbial activity and nitrogen availability as key predictors of yield and nutrient uptake. These results demonstrate CFMI-8’s potential to enhance soil fertility, promote nutrient cycling, and improve crop productivity under field conditions. The findings support microbial inoculants as viable tools for regenerative agriculture and emphasize the need for long-term studies to assess sustainability impacts. Full article

High nitrogen use efficiency is crucial for enhancing spinach’s tolerance to low nitrogen stress and minimizing nitrate accumulation. Here, we report that SoNRT3, a NAR2 family protein, modulates nitrate uptake and plant growth under low-nitrate conditions. SoNRT3 expression was induced by low nitrate availability in roots and prolonged nitrogen deficiency in shoots. Compared to wild-type Arabidopsis thaliana, lines overexpressing SoNRT3 exhibited higher root fresh weight, activities of nitrogen reduction/assimilation-related enzymes, tap root length, and total root diameter under low-nitrate (0.25 mM) conditions. SoNRT3 silencing reduced taproot length, lateral root number, shoot/root biomass, and ¹⁵${\mathrm{N}\mathrm{O}}_3^{-}$ uptake in spinach grown under low-nitrate conditions. SoNRT3 partially compensated for ¹⁵${\mathrm{N}\mathrm{O}}_3^{-}$ uptake in atnrt2.1 and atnrt3.1 mutants. Transcriptome analysis showed that SoNRT3 may enhance nitrate uptake and root development by promoting the expression of high-affinity nitrate transporters, nitrogen assimilation, auxin signaling, and cell differentiation. Additionally, SoNRT3 can interact with a spinach NRT2 family protein (SoNRT2a), whose transcription level was also induced by low N and N deficiency. Together, this study clarifies the key roles and regulatory network of SoNRT3 in low-nitrate tolerance, which contributes to a novel understanding of nitrate utilization in spinach. Full article

Vertical farming systems offer an efficient solution for sustainable food production in urban areas. However, managing nitrate (NO₃⁻) levels remains a significant challenge for improving crop yield, quality, and safety. This study evaluated the effects of nitrate availability on growth performance, nutrient uptake, and water use efficiency in a vertical hydroponic system that intercropped lettuce (Lactuca sativa) with alfalfa (Medicago sativa). The experiment was conducted in a controlled vertical hydroponic system using Nutrient Film Technique (NFT) channels, with nitrogen levels set at 0, 33, 66, 100, and 133% of the standard concentration. The results indicated that the intercropping treatment with 66% nitrate (IC-N_66%) improved water use efficiency by 38% and slightly increased leaf area compared to the other intercropping treatments. However, the control group, which consisted of a monoculture with full nitrate supply, achieved the highest overall biomass. Ion concentrations, including nitrate, calcium, magnesium, and micronutrients, were moderately affected by the intercropping strategy and nitrate levels. These findings suggest that moderate nitrate input, combined with nitrogen-fixing legumes, can enhance resource efficiency in hydroponic systems without significantly compromising yield. These findings offer a promising framework for incorporating legumes into hydroponic systems, minimizing the need for synthetic inputs while maintaining yield. These results support the use of agroecological intensification strategies in highly efficient soilless systems. Full article

The critical nitrogen (N) dilution curve is widely used to diagnose crop N status, but no such model has been developed for sugar beet. This study evaluated the effects of irrigation amount and N rate on sugar yield, N use efficiency, and soil nitrate-N (NO₃-N) residue of drip-fertigated sugar beet in the arid southern Xinjiang of China. A reliable N nutrition index (NNI) for sugar yield was also established based on a critical N dilution curve derived from the dry matter of sugar beet. A three-year field experiment was established with six N rates (25–480 kg N ha⁻¹) and three irrigation levels based on crop evapotranspiration (ET_c) (0.6, 0.8, and 1.0 ET_c in 2019 and 2020, and 0.4, 0.6, and 0.8 ET_c in 2021). Results showed that sugar yield and N uptake increased and then generally stabilized with increasing N rate, while N use efficiency decreased. Most soil NO₃-N was mainly distributed in the 0–60 cm soil layer, but increasing irrigation amount reduced residual NO₃-N in the 0–80 cm soil layer. Additionally, the established critical N dilution curve of sugar beet was considered stable (Normalized RMSE = 16.6%), and can be used to calculate plant N requirements and further N rates during sugar beet growth. The results indicated that the optimal NNI was 0.97 under 0.6 ET_c for sugar yield production of sugar beet in this study. This study provides a basis for efficient water and N management in sugar beet production in arid and semi-arid regions globally. Full article

Nitrogen fertilization plays a crucial role in optimizing plant growth, but excessive application can lead to nutrient leaching, environmental pollution, and soil degradation. This study investigates the impact of nitrogen application rates (0–400 kg·ha⁻¹) on the growth, biomass allocation, and carbon sequestration capacity of Pennisetum hydridum (Imperial Bamboo, PHY), a fast-growing tropical grass increasingly used for forage and bioenergy production in subtropical regions. Despite its agronomic potential, nutrient management strategies for P. hydridum remain poorly understood. We hypothesized that moderate nitrogen application (100–200 kg·ha⁻¹) would enhance growth and nutrient use efficiency, while maintaining environmental sustainability. Results show that moderate nitrogen levels (100–200 kg·ha⁻¹) significantly enhanced biomass production, with the highest aboveground biomass observed at 180 days under T2 (100 kg·ha⁻¹) and T3 (200 kg·ha⁻¹), reaching 166.5 g/plant and 140.6 g/plant, respectively. In contrast, excessive nitrogen application (400 kg·ha⁻¹) led to a decline in biomass (T4, 76.8 g/plant) and impaired carbon sequestration efficiency. In addition, it was found that nitrogen uptake increased with moderate fertilization, with T2 and T3 showing optimal nitrogen use efficiency. Soil analysis revealed that soil organic matter and total nitrogen content were positively correlated with root biomass, with significant linear relationships between soil nitrogen, carbon/nitrogen ratios, and PHY biomass. Specifically, the total nitrogen content in rhizomes and fibrous roots showed coefficients of determination (R²) of 0.65 and 0.67, indicating a strong correlation with soil nitrogen levels. Furthermore, nitrogen application increased soil nitrate (NO₃⁻-N) and ammonium (NH₄⁺-N) concentrations, with T4 showing the highest levels at 90 days (41.35 mg/kg for NO₃⁻-N and 15.6 mg/kg for NH₄⁺-N), signaling potential nutrient loss to the environment. These findings underscore the importance of sustainable nitrogen management for maximizing the growth potential of P. hydridum, while minimizing environmental risks in subtropical agricultural systems. Full article

In the absence of fully effective therapies and preventive strategies against the development of urosepsis, a deeper understanding of the virulence mechanisms of Uropathogenic Escherichia coli (UPEC) strains is needed. UPEC strains employ a wide range of virulence factors (VFs) to persist in the urinary tract and bloodstream. UPEC strains were isolated from patients with sepsis and a control group without sepsis. PCR was used to detect 36 genes encoding various groups of virulence and fitness factors. Profiling of both intracellular and extracellular bacterial proteins was also included in our approach. Bacterial metabolites were identified and quantified using GC-MS and LC-MS techniques. The UpaG autotransporter, a trimeric E. coli AT adhesin, was significantly more prevalent in urosepsis strains (p = 0.00001). Iron uptake via aerobactin and the Iha protein also appeared to be predictive of urosepsis (p = 0.03 and p = 0.002, respectively). While some studies suggest an association between S fimbriae and the risk of urosepsis, we observed no such correlation (p = 0.0001). Proteomic and metabolomic analyses indicated that elevated levels of bacterial citrate, malate, coenzyme Q10, pectinesterase (YbhC), and glutamate transport proteins, as well as the regulators PhoP two-component system, CpxR two-component system, Nitrate/nitrite response regulator protein NarL, and the Ferrienterobactin receptor FepA, may play a role in sepsis. These genetic biomarkers, proteins, and metabolites derived from UPEC could potentially serve as indicators for assessing the risk of developing sepsis. Full article

Lead (Pb) pollution poses a long-term threat to forest ecosystems, particularly in mountainous areas affected by atmospheric deposition. This study examined the physiological and biochemical responses of juvenile Pinus sylvestris L. and Picea abies (L.) H. Karst seedlings to low concentrations of lead nitrate during early development. Treatments simulated environmentally relevant Pb exposure and focused on pigment composition, oxidative stress markers, soluble protein and proline levels, and elemental content. Both species exhibited hormetic stimulation of photosynthetic pigments at lower Pb concentrations. In P. sylvestris, this effect declined at the highest dose, whereas P. abies maintained pigment levels, suggesting stronger regulatory control. Pb exposure reduced soluble proteins and induced species-specific alterations in MDA and proline levels. Correlation analysis revealed a well-integrated stress response in P. abies, while P. sylvestris showed a more fragmented pattern. Elemental analysis confirmed Pb accumulation primarily in roots, with higher levels in P. sylvestris. Both species experienced reduced root Mg, K, and Mn, indicating ionic imbalance due to Pb²⁺ interference. Zn content increased in P. sylvestris but decreased in P. abies, possibly reflecting differences in uptake regulation. These species-specific responses support the hypothesis that P. abies activates more effective defense mechanisms against Pb toxicity, while P. sylvestris exhibits a stronger physiological stress response. Full article

The co-incorporation of green manure and rice straw is commonly used to increase rice yield and improve soil fertility in paddy fields. However, the effects on nutrient uptake and utilization of rice under the synergistic interaction mechanism in the Taihu Plain of the Yangtze River Delta remain unclear. Based on field experiments, this study investigated the effects of green manure with rice straw return (GMS) under different nitrogen (N) fertilization rates on rice yield, nutrient use efficiency, and soil fertility. The results revealed that green manuring significantly increased rice yield while improving the uptakes and use efficiencies of N, phosphorus (P) and potassium (K). Green manure (GM) with 40% N fertilizer reduction (GM_N60) maintained the grain and straw yields and nutrient uptakes compared to winter fallow with 100% conventional N application (WF_N100). The N recovery efficiency in GM_N60 reached 45.52%, increasing by 41.26% compared to WF_N100. Rice yield and K uptake in the GMS with 40% N fertilizer reduction treatment (GMS_N60) was 10,058 and 15.41 kg/hm², increasing by 14.43% and 9.43% compared to winter fallow with rice straw return and 100% conventional N (WFS_N100). The N, P and K agronomic efficiencies in GMS_N60 increased by 77.04%, 50.22%, and 50.22% compared to WFS_N100, respectively. These findings indicate that rice straw return enhances the fertilizer-saving and yield-increasing effects of GM, promotes rice K uptake and improves P and K use efficiencies. The GM treatment increased the soil organic matter (SOM), total potassium (TK), ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) contents. Among the soil fertility indicators, TK and SOM were the most important factors influencing rice yield and N uptake. In conclusion, GMS can maintain or increase rice yield with 40% N fertilizer reduction, improve nutrient use efficiencies, and increase the reuse of rice straw, thereby supporting green and efficient rice production in the southern Jiangsu paddy area. Full article

Molybdenum (Mo) is a vital micronutrient for nearly all living organisms, serving as a cofactor for molybdoenzymes that catalyze essential redox reactions in nitrogen metabolism. Among these enzymes, nitrate reductase plays a crucial role in nitrate assimilation. Maintaining Mo homeostasis—including uptake, storage, and utilization—is critical to avoid both deficiency and toxicity. Our research focuses on uncovering novel molecular components involved in Mo homeostasis, particularly in connection with nitrate assimilation, using Chlamydomonas reinhardtii, a model green microalga. To achieve this, we generated more than 5000 Chlamydomonas transformants through insertional mutagenesis using a paromomycin resistance cassette (AphVIII) and screened them for altered growth on nitrate and under different Mo concentrations. We identified four strains showing altered growth patterns when using nitrate as a nitrogen source or exhibiting increased sensitivity or resistance to Mo. The genomic alterations in these strains were identified. Notably, both a Mo-resistant and a Mo-sensitive transformant had disruptions in the genes that encoded ABC-type transport proteins, indicating a potential role for these proteins in Mo transport. Additionally, two strains were unable to grow on nitrate. One of them had a mutation in the CNX7, a gene involved in Mo cofactor biosynthesis, while the other had a mutation in BAT1, an amino acid transporter. The BAT1 mutant represents an interesting case study, as this gene has not previously been associated with nitrate metabolism. These findings enhance our understanding of Mo and nitrate homeostasis mechanisms and open new paths for engineering microalgae with improved nitrogen assimilation. Full article

This study investigates the potential of a biostimulant derived from the invasive brown alga Rugulopteryx okamurae (RoB) to enhance lettuce growth and improve its phytochemical profile. The extraction of the biostimulant was optimized through the implementation of a Box–Behnken design, and the resulting extract was then compared with a commercial Ascophyllum nodosum-based product (AnB). This comparison was made under both optimal and suboptimal fertigation conditions in a controlled, soilless culture. Lettuce plants were monitored for water and nutrient uptake, growth parameters, and accumulation of key phytochemicals such as carotenoids, tocols, sterols, and squalene. RoB significantly increased fresh and dry biomass, with enhanced nitrate and potassium uptake, in comparison to standard nutrient solution controls (p < 0.05). Treatments incorporating RoB consistently resulted in higher concentrations of lutein, β-sitosterol, and squalene, particularly under suboptimal conditions (p < 0.05), thus suggesting a strong biostimulant effect that mitigates nutrient stress. Furthermore, principal component analysis demonstrated that biostimulant application induces distinct metabolic profiles, highlighting the coordinated regulation of antioxidant pigments and sterol compounds. The findings support the dual benefits of algae-derived biostimulants in promoting sustainable crop production by improving yield quality and increasing health-promoting phytochemicals, paving the way for innovative, eco-friendly fertilization practices in modern agriculture. Full article

Understanding plant nitrogen (N) uptake strategies during vegetation recovery is essential for restoring and rehabilitating degraded ecosystems. However, there are few studies on plant N uptake strategies in karst regions. In this study, space-for-time substitution was used to investigate the dynamic changes in plant N uptake strategies during vegetation restoration. Grassland, shrub–grassland, shrubland, and woodland naturally recovering in karst ecosystems were chosen as the research objects. The dominant species at each stage were investigated. Dominant plant N uptake rates were measured using the ¹⁵N labeling technique, and plant root functional traits and available soil N were determined. Our results showed that soil inorganic N content and composition varied significantly with vegetation recovery. In early vegetation recovery stages, the soil inorganic N content was low and dominated by ammonium (NH₄⁺), while in the late stages, soil inorganic N content increased, and nitrate (NO₃⁻) became the dominant form. In early vegetation recovery stages, dominant plants preferentially absorbed NH₄⁺, contributing to 90.3%–98.5% of the total N uptake. With vegetation recovery, plants increased the NO₃⁻ uptake ratio from 1.48%–9.42% to 30.1%–42.6%. Additionally, the root functional traits of dominant plants changed significantly during vegetation recovery. With vegetation recovery, specific root lengths and specific root areas decreased, while root N content and plant N uptake rates increased. In summary, plants developed N uptake strategies coordinated with soil N supply by modifying root functional traits following vegetation recovery in karst regions. Full article

Nitrogen fertilizers play a critical role in enhancing crop yields; however, excessive application has resulted in significant environmental challenges, including water contamination and increased greenhouse gas emissions. Therefore, improving nitrogen use efficiency is essential for sustainable agriculture. This review based on a systematic search of Web of Science and CNKI for peer-reviewed studies on maize nitrogen efficiency published between 1945 and 2024 (excluding conference abstracts), this review presents the first multiscale synthesis demonstrating how balanced nitrate–ammonium nutrition coordinates N–C metabolism and phytohormone signaling to boost nitrogen use efficiency and stimulate maize growth, with supporting evidence from other crops. By integrating results from hydroponic and field experiments, the review evaluates the influence of mixed nitrogen sources on nitrogen uptake, root morphology, photosynthesis, carbon metabolism, and hormone signaling. Findings indicate that optimal NO₃⁻:NH_4⁺ ratios improve nitrogen absorption through enhanced root development and activation of specific nitrogen transporters. Additionally, mixed nitrogen nutrition increases photosynthetic efficiency, promotes carbon assimilation, reduces energy expenditure, and stimulates auxin-mediated growth. This review shows that balanced nitrate–ammonium co-application synergistically enhances crop nitrogen-use efficiency and yield, provides a theoretical basis for high-efficiency nitrogen-fertilizer development, and helps alleviate environmental pressures, advance sustainable agriculture, and secure food and ecosystem safety. Its efficacy, however, is modulated by soil type, climate, and genotypic variation, necessitating systematic validation and application optimization in future research. Full article