Search Results (44)

Aluminum (Al) toxicity constrains plant performance in acidic volcanic soils, yet nitrogen (N) fertilization may influence Al availability and plant responses. This study evaluated the effects of N source and rate under contrasting soil liming conditions on vegetative growth, mineral nutrition, and physiological performance of non-bearing northern highbush blueberry (Vaccinium corymbosum L. cv. Blue Ribbon^®) plants. A split–split-plot experiment was conducted in southern Chile using urea or potassium nitrate applied at 0, 20, or 40 kg N ha⁻¹ to plants grown in unlimed soil or soil amended with calcium carbonate or magnesium oxide. Vegetative growth, tissue mineral composition, stomatal conductance, chlorophyll fluorescence, and leaf chlorophyll were monitored during the first season. Growth responded primarily to soil liming rather than N supply, indicating low N demand and substantial soil N mineralization under the experimental conditions. Foliar N increased from 1.36 to 1.70% with increasing N rates. Urea nutrition reduced foliar Al concentration by 12% compared with nitrate. Under unlimed conditions, representing maximal soil Al availability, urea fertilization was associated with 70% higher Al retention in roots relative to nitrate. Chlorophyll content was consistently higher under urea supply, while the maximum photochemical efficiency of photosystem II remained unaffected. These findings indicate that N form influences plant Al partitioning independently of growth responses. Although the underlying mechanisms were not directly assessed, the observed patterns suggest that urea fertilization may reduce Al translocation to shoots under conditions of high Al availability. Full article

Foliar application of fertilizers and bioactive compounds helps viticulture adapt to climate change, while biochar (BC) derived from grapevine pruning residues (GPRs) represents a versatile material that further contributes to climate change mitigation. In this study, the foliar application impact of seven different formulations on the chemical composition and quality of must and wine of Malvazija istarska (Vitis vinifera L.) was investigated. The suspensions contained various combinations of BC, urea, and amino acids. BC increased the pH of the solutions in which it was present due to its alkaline nature, thereby influencing the uptake of nutrients and other compounds. Treatments C (control) and A (amino acids) led to the highest amount of yeast-assimilable nitrogen (YAN) (170 and 172 mg N/L). The amino acid profile of the must differed from the typical composition, with glutamine identified as the predominant compound. The combination of BC with urea and amino acids was associated with a higher sugar concentration in the must compared to the application of BC alone, ranging from 208 to 223 g/L. Combining BC with other components led to wines that received superior sensory evaluation scores compared to both C and B. BC alone did not influence must or wine quality. However, its application in combination with other components makes it a suitable carrier for such compounds. Due to its benefits, easy and cheap production, foliar application of BC suspensions with fertilizers can become a standard operation in viticulture and contribute to sustainable fertilization. Full article

Understanding how supplemental nitrogen (N) interacts with biological N₂ fixation (BNF) in modern soybean cultivars is essential for designing fertilization strategies that avoid unnecessary N inputs. We investigated N partitioning among soil, fertilizer and symbiotic sources in soybean grown in a greenhouse pot experiment on a tropical Oxisol. Plants were inoculated with Bradyrhizobium and subjected to four N managements: no external N, soil-applied ¹⁵N-urea (20 kg N ha⁻¹), foliar ¹⁵N-urea (2 kg N ha⁻¹, 0.7% w/v), and the combination of soil + foliar N. Using ¹⁵N isotope dilution, we quantified N derived from the atmosphere (NDFA), fertilizer (NDFF) and soil (NDFS) at organ and whole-plant scales, and related these fractions to nodulation, nitrogenase activity and yield. In the absence of external N, NDFA exceeded 97% in all organs, indicating a strong reliance on BNF and efficient internal N remobilization during grain filling, accompanied by higher leaf nitrate reductase activity. Soil and soil + foliar N markedly increased NDFF and NDFS while suppressing nodulation (particularly at V4) and reducing nitrogenase activity, yet they did not improve grain yield or vegetative biomass. Foliar N alone had only modest effects on N partitioning and did not enhance yield. Under these tropical soil conditions, symbiotic fixation and internal N remobilization were sufficient to meet grain N demand, highlighting the limited agronomic benefit and potential ecological cost of supplemental N during reproductive growth. Full article

Efficient use of nitrogen and phosphorus is crucial for achieving sustainable wheat production. Slow-release nano-fertilizers offer a targeted strategy to minimize nutrient losses, reduce excessive fertilizer application, and improve crop yield. This study introduces urea–hydroxyapatite (n-UHA) nanohybrid as a slow-release fertilizer synthesized to enhance nitrogen (N) and phosphorus (P) delivery efficiency in wheat (Triticum aestivum L.). Physical characterization techniques, including Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Zetasizer, and Fourier Transform Infrared Spectroscopy (FTIR), confirmed the formation of spherical n-UHA with a particle size of 106 nm. FTIR results indicated the formation of physically bound urea as a coating layer on the particle surface. Foliar application of n-UHA at 2500 and 5000 ppm N significantly increased tiller intensity and grain yield compared to conventional urea. The highest biological yield, approximately 16 t ha⁻¹, was achieved with 5000 ppm n-UHA plus supplemental soil phosphorus (P), representing a 4-fold increase over the control. Conventional urea treatments, in comparison, only doubled yield. Notably, increasing conventional urea concentration from 2500 to 5000 ppm N did not significantly increase the yield even with additional P-soil supplement, while applying 5000 ppm N from n-UHA with supplemental P provided an approximate 25% yield increase compared to 2500 ppm n-UHA without P. The n-UHA’s slow-release mechanism supported prolonged tiller intensity, enhanced protein content, and higher biomass yield and chlorophyll content. This study showed that the slow-release mechanism of urea in the monohybrid due to hydrolysis resulted in localized acidity from carbonic acid production on the leaf surface area and contributed to dissociating phosphate ions from hydroxyapatite, making phosphorous more accessible. The enhanced performance of n-UHA is due to its controlled nutrient release, enabled by the physical binding of urea with hydroxyapatite nanoparticles. This binding ensures a synchronized supply of nitrogen and phosphorus aligned with plant demand. The nano-hydroxyapatite composite (N/Ca 6:1) supplies balanced nutrients via efficient stomatal absorption and gradual release. As an eco-friendly alternative to conventional fertilizers, n-UHA improves nitrogen delivery efficiency and reduces N-evaporation, supporting sustainable agriculture. Full article

Nitrogen (N) critically regulates wheat growth and grain quality, yet the molecular mechanisms underlying foliar nitrogen application remain unclear. This study evaluated the effects of foliar nitrogen application (12.25 kg ha⁻¹) on the growth, grain yield, and quality of spring wheat, as well as its molecular mechanisms. The results indicated that N was absorbed within 3 h post-application, with leaf nitrogen concentration peaking at 12 h. The N treatment increased whole-plant dry matter accumulation and grain protein content by 11.34% and 6.8%, respectively. Amino acid content peaked 24 h post-application, increasing by 25.3% compared to the control. RNA-sequencing analysis identified 4559 and 3455 differentially expressed genes at 3 h and 24 h after urea treatment, respectively, these DEGs being primarily involved in nitrogen metabolism, photosynthetic carbon fixation, amino acid biosynthesis, antioxidant systems, and nucleotide biosynthesis. Notably, the plastidic glutamine synthetase gene (GS2) is crucial in the initial phase of urea application (3 h post-treatment). The pronounced downregulation of GS2 initiates a reconfiguration of nitrogen assimilation pathways. This downregulation impedes glutamine synthesis, resulting in a transient accumulation of free ammonia. In response to ammonia toxicity, the leaves promptly activate the GDH (glutamate dehydrogenase) pathway to facilitate the temporary translocation of ammonium. This compensatory mechanism suggests that GS2 downregulation may be a key switch that redirects nitrogen metabolism from the GS/GOGAT cycle to the GDH bypass. Additionally, the upregulation of the purine and pyrimidine metabolic routes channels nitrogen resources towards nucleic acid synthesis, and thereby supporting growth. Amino acids are then transported to the seeds, culminating in enhanced seed protein content. This research elucidates the molecular mechanisms underlying the foliar response to urea application, offering significant insights for further investigation. Full article

The effects of the foliar spraying of carbon and nitrogen on the yield and quality of fragrant rice (Oryza sativa L.) remain unknown. A two-year field experiment was conducted by using two fragrant rice varieties, Meixiangzhan 2 and Xiangyaxiangzhan, as experimental materials. Three carbon treatments (C0: 0 mg L⁻¹ glucose, C1: 150 mg L⁻¹ glucose, and C2: 300 mg L⁻¹ glucose, recorded as C0, C1, and C2, respectively) and three nitrogen treatments (N0: 0 mg L⁻¹ urea, N1: 50 mg L⁻¹ urea, and N2: 100 mg L⁻¹ urea) were employed as experimental treatments, and there were a total of nine treatments (C0N0, C0N1, C0N2, C1N0, C1N1, C1N2, C2N0, C2N1, and C2N2). The yield and quality of fragrant rice were investigated. The results show that carbon and nitrogen treatments significantly affected the yield and grain number per panicle in fragrant rice. The yields of the two cultivars under C1N2 and C2N1 were maintained at high levels. This was mainly because the C1N2 and C2N1 treatments resulted in higher grain number per panicle and grain filling percentage. Carbon and nitrogen treatments significantly increased the dry weight and photosynthesis parameters of fragrant rice. The carbon and nitrogen treatments significantly increased the protein content. The improved grain yield was related to improvements in photosynthesis and antioxidant defense as well as osmoregulation. In summary, optimized spraying of 150 mg L⁻¹ glucose and 100 mg L⁻¹ urea at the booting stage benefits yield and grain quality by regulating photosynthesis, antioxidant defense, and osmoregulation. Full article

Increasing wheat (Triticum aestivum L.) grain protein concentration (GPC) without excessive nitrogen (N) inputs requires understanding the interactions between N source characteristics and application technology parameters. This study evaluated the effects of foliar N applications at anthesis on wheat grain yield and GPC across three locations over three growing seasons in Oklahoma. Treatments consisted of two N sources (urea-ammonium nitrate [UAN] and aqueous urea [Aq. urea]), three nozzle types (flat fan [FF], 3D, and twin [TW]), and two droplet types (fine and coarse). Late foliar applications increased GPC by 12% without affecting grain yield (0.5–5.8 Mg ha⁻¹). During the 2020–21 growing season, a late season freeze during anthesis resulted in no significant differences in GPC across locations. UAN produced significantly higher GPC (13.7%) than Aq. urea (13.1%). Among nozzle types, the 3D nozzle consistently produced the highest GPC (13.8%), compared to FF (13.1%) and TW nozzles (13.2%). Two-way interactions revealed UAN with fine droplets achieved consistently high GPC (14.6%), as did Aq. urea with coarse droplets (14.5%) at Lake Carl Blackwell in 2021–22 as compared to Aq. Urea_Fine (13.8%). At Chickasha 2021–22 and Perkins 2020–21, a significant three-way interaction was observed, with the UAN_3D_Fine (13.2%) and UAN_3D_Coarse (12.2%) treatments producing the highest GPC, with 8% and 15% greater than the Aq. Urea_TW_Fine, respectively, which is lowest. These findings provide a foundation for precision agriculture approaches that optimize foliar N application parameters to enhance wheat quality while maintaining sustainable production practices. Full article

Basil (Ocimum basilicum L.) is a prominent medicinal and aromatic plant, widely recognized for its bioactive compounds and substantial economic value across the pharmaceutical, culinary, and industrial sectors. In light of increasing global demand and environmental challenges, this study explores novel approaches to enhance its sustainable production and improve its quality. Urea is the most common form of nitrogen (N) for foliar application due to its quick absorption, affordability, high solubility, as well as relatively low cost per N unit. Amino acids are an organic form of N and play a role in plant protein structure, stress tolerance, and the biosynthesis of secondary metabolites. This research aimed to evaluate the effects of urea (0, 1, and 2 g L⁻¹) and an amino acid-based biostimulant (AAB) (0, 4, and 8 mg L⁻¹), applied foliarly, on the growth, photosynthesis, pigments, antioxidant activity, and essential oil production of basil (Ocimum basilicum L.). The best results in terms of leaf number, area, and fresh and dry weight were observed with the combination of 2 g L⁻¹ urea and 8 mg L⁻¹ AAB. The growth enhancement due to this treatment may be attributed to stimulatory effects on photosynthesis and N content. Chlorophyll, carotenoids, anthocyanins, photosynthesis, stomatal conductance, total phenols, and total flavonoids increased with urea application up to 1 g L⁻¹. Additionally, AAB application up to 8 mg L⁻¹ increased total chlorophyll, carotenoid, total phenols, and total flavonoids, while photosynthesis and anthocyanin content increased with 4 mg L⁻¹ AAB. Although urea did not significantly affect essential oil content and yield, AAB application increased both. Finally, the combination of 1 g L⁻¹ urea and 8 mg L⁻¹ AAB had the most effective impact on improving content and yield of essential oil, total phenol, flavonoid, anthocyanin, and antioxidant activity, with a relatively high percentage of estragole. Full article

Increasing the recovery of N fertilizer (RNf) is the main challenge in managing nitrogen fertilization in sugarcane. This study aimed to evaluate the efficiency of complementary foliar fertilization in managing nitrogen nutrition in sugarcane. Four fertilization managements, combining soil (5.0 and 4.5 g plot⁻¹ of N) and foliar (1.0 and 1.5 g plot⁻¹ of N) fertilization in up to two application events (0.5 + 0.5 and 0.75 + 0.75 g plot⁻¹ of N), were compared with conventional fertilization (6.0 g plot⁻¹ of N in soil). The change from 6.0 g plot⁻¹ to 4.5 g plot⁻¹ of N reduced the RNf by 46% before the first foliar fertilization. The RNf (26%) was similar between managements after the first foliar fertilization. After the second foliar fertilization, the RNf was 38% higher than that for conventional management. The accumulation of N in the aerial part of sugarcane was similar between managements until the first foliar fertilization. After the second foliar fertilization, the accumulation of N increased by 3.5% with foliar fertilization. The biomass accumulated by the managements was similar before and after the first and second foliar fertilization. The splitting of foliar fertilization increased the accumulation of N and RNf by 22% and 24%, respectively. The fertilization management with 4.5 g plot⁻¹ of N applied to the soil, with two applications of 0.75 g plot⁻¹ of N on the leaf, obtained greater accumulations of N and RNf. Foliar fertilization increases the efficiency of fertilization and improves the N nutrition of sugarcane. Full article

Nickel (Ni) is an essential micronutrient for plants, responsible for metabolizing urea nitrogen (urea-N) by urease and mitigating abiotic and oxidative stresses through the glyoxalase (Gly) and glutathione (GSH) cycles. However, excess Ni is toxic to flora at >100 mg kg⁻¹, except for hyperaccumulators that tolerate >1000 mg kg⁻¹ Ni. This review discusses the benefits of Ni nutrient management for soil fertility, improving food security, and minimizing adverse environmental impacts from urea overapplication. Many farming soils are Ni deficient, suggesting that applying 0.05–5 kg ha⁻¹ of Ni improves yield and urea-N use efficiency. Applied foliar and soil Ni fertilizers decrease biotic stresses primarily by control of fungal diseases. The bioavailability of Ni is the limiting factor for urease synthesis in plants, animal guts, and the soil microbiome. Improved urease activity in plants and subsequently through feed in livestock guts reduces the release of nitrous oxide and nitrite pollutants. Fertilizer Ni applied to crops is dispersed in vegetative tissue since Ni is highly mobile in plants and is not accumulated in fruit or leafy tissues to cause health concerns for consumers. New methods for micronutrient delivery, including rhizophagy, recycled struvite, and nanoparticle fertilizers, can improve Ni bioavailability in farming systems. Full article

The co-application of N and Fe can improve wine grape composition and promote the formation of flavor compounds. To understand the effects of foliar co-application of N and Fe on wine grape quality and flavonoid content, urea and EDTA-FE were sprayed at three different developmental stages. Urea and EDTA-Fe were sprayed during the early stage of the expansion period, at the end of the early stage of the expansion period to the late stage of the veraison period, and during the late stage of the veraison period. The results demonstrated that the co-application of urea and EDTA-Fe, particularly N application during the late stage of the veraison period and Fe application during the early stage of the berry expansion period (N3Fe1), significantly improved grape quality. Specifically, the soluble solid content of berries increased by 2.78–19.13%, titratable acidity decreased by 6.67–18.84%, the sugar-acid ratio became more balanced, and yield increased by 13.08–40.71%. Further, there was a significant increase in the relative content of amino acids and flavonoids. In conclusion, the application of Fe and N fertilizers at the pre-expansion and late veraison stages of grapes can significantly improve the quality and yield of berries; ultimately, this establishes a foundation for future improvement in the nutritional value of grapes and wine. Full article

Waterlogging increasingly challenges crop production, affecting 10% of global arable land, necessitating the development of pragmatic strategies for mitigating the downside risk of yield penalty. Here, we conducted experiments under controlled (tank) and field conditions to evaluate the efficacy of nitrogenous fertiliser in alleviating waterlogging stress. Without intervention, we found that waterlogging reduced grain yields, spike numbers and shoot biomass, but had a de minimus impact on grain number per spike and increased grain weight. Soil fertiliser mitigated waterlogging damage, enhancing yields via increased spike numbers, with crop recovery post-waterlogging catalysed via improved tiller numbers, plant height and canopy greenness. Foliar nitrogen spray has little impact on crop recovery, possibly due to stomatal closure, while modest urea application during and after waterlogging yielded similar results to greater N application at the end of waterlogging. Waterlogging-tolerant genotypes (P-17 and P-52) showed superior growth and recovery during and after waterlogging compared to the waterlogging-sensitive genotypes (Planet and P-79). A comparison of fertiliser timing revealed that field fertilizer treatment two (F2: 90 kg·ha⁻¹ at 28 DWL, 45 kg·ha⁻¹ at sowing and 45 kg·ha⁻¹ at 30 DR) yielded the highest and fertilizer treatment three (F3: 45 kg·ha⁻¹ at sowing and 45 kg·ha⁻¹ at 30 DR) recovered the lowest yield and spike number, while fertilizer treatment one (F1: 45 kg·ha⁻¹ at 28 DWL, 45 kg·ha⁻¹ at 0 DR, 45 kg·ha⁻¹ at sowing and 45 kg·ha⁻¹ at 30 DR) and four (F4: 90 kg·ha⁻¹ at 0 DR, 45 kg·ha⁻¹ at sowing and 45 kg·ha⁻¹ at 30 DR) had the highest shoot biomass in the field. Treatment five (T5: 180 kg·ha⁻¹ at 0 DR, 30 kg·ha⁻¹ at sowing and 90 kg·ha⁻¹ at 30 DR) presented the most favourable results in the tank. Our results provide rigorous evidence that long periods of waterlogging caused significant yield penalty, mainly due to decreased spike numbers. We contend that increasing fertiliser rates during waterlogging up to 90 kg·ha⁻¹ can provoke crop growth and mitigate waterlogging-induced grain yield losses, and is more beneficial than applying nitrogen post-waterlogging. Full article

In viticulture, the main target is to achieve high yield and good fruit quality without compromising vine growth. Methods to achieve this balance will vary with regard to climate and cultivar. A two-year study was conducted on five-year-old ‘Prime Seedless’ grapevines to evaluate the effect of leaf defoliation and the foliar application of low-biuret urea (LBU) and cyanocobalamin (CCA) on berry set percentage, the compactness coefficient of the clusters and the overall quality of clusters and berries. The removal of the first four basal leaves was conducted at the full-bloom (FB) stage, while LBU (5 g·L⁻¹) and CCA (40 mg·L⁻¹) were sprayed at three phenological stages: (1) when the cluster length reached ~10 cm long, (2) at FB and (3) one week after the fruit set. The results demonstrated that the sole application of basal leaf removal (BLR) or in combination with LBU and/or CCA improved the vegetative growth, total yield and physiochemical characteristics of clusters and berries, whereas the same treatments decreased berry set and shot berry percentages and the compactness coefficient of the clusters, which in turn led to looser clusters compared to the control. The most pronounced effect was recorded for the combined application of BLR, LBU and CCA, which revealed the highest values of shoot length, leaf area and the contents of chlorophyll, proline, N, P, K, Ca, Mg, Fe and Zn. The same treatment recorded the lowest berry set and shot berry percentages, compactness coefficient of clusters and decay percentage. Overall, this treatment was the best in terms of total yield, cluster weight, berry firmness, soluble solid content (SSC), the SSC/acid ratio, total sugars, total carotenoids, total phenols, phenylalanine ammonialyase and polyphenol oxidase. Full article

The study aimed to compare the effect of urea fatty fraction (UFF) and Pulrea^® (urea fertilizer) on plant yield and selected plant and soil parameters determined after the plants were harvested. UFF is a by-product of essential unsaturated fatty acids (UFAs) extraction from fish oil using urea, and Pulrea^® is a commercial urea fertilizer. Both products were applied to the soil and the leaves (foliar application). The effect of Pulrea^® on plant yield was generally stronger than that of UFF but depended on soil properties and plant species. Both fertilizers, but especially UFF, increased the total N content in the plant and effected nitrate accumulation. The plants used 45–90% of fertilizer nitrogen, with the plants generally using more N from Pulrea^® than from UFF. Higher nitrogen production efficiency was achieved using Pulrea^® than UFF and when plants were cultivated on medium soil than on light soil. Fertilizers increased the acidity and electrolytic conductivity of both soils but did not induce soil salinization. They increased the content of mineral nitrogen forms in soils, which was generally the case more in soil with Pulrea^® application than with UFF application. As a rule, the soil dehydrogenases activity did not change significantly or even decrease after fertilizer application. It was visibly higher in medium soil and after foliar Pulrea^® application than after foliar UFF application. This may be due to the content of accompanying substances in UFF that affect nitrogen absorption from this fertilizer. Based on the results, it cannot be clearly stated that one of the tested fertilizers had a better effect on the studied parameters. Generally, the less favorable effects of UFF compared to Pulrea^® may indicate the necessity of removing from UFF the accompanying substances that may adversely affect plants and soil microorganisms. This aspect needs to be investigated under controlled conditions in field experiments. Full article

Nitrogen (N) is the essential plant nutrient needed by turfgrass in the greatest quantity. Urea and urea-based liquids are arguably the safest, least expensive, and subsequently most popular soluble N fertilizers. Unfortunately, urea fertilizer application to turfgrass is often subject to NH₃ volatilization: a deleterious phenomenon from both environmental and agronomic perspectives. The objective of this research was to quantify the efficacy of creeping bentgrass (Agrostis stolonifera L.) golf course fairway foliar fertilization by urea-based N fertilizers as influenced by a petroleum-derived spray oil (PDSO) containing Cu II phthalocyanine colorant (Civitas Turf Defense^TM Pre-M1xed, Intelligro LLC, Mississauga, ON, Canada). In 2019 and 2020, a maintained creeping bentgrass fairway received semimonthly 9.76 kg ha^–1 soluble N treatment either alone or in combination with Civitas at a rate of 27 L ha^–1. In the 48 h following foliar application, fertilizer N loss as NH₃ ranged from 1.3 to 5.5% and corresponded directly to fertilizer urea content but not Civitas inclusion. In the 1 to 14 d following semimonthly treatment, Civitas had either a beneficial (methylol urea and UAN) or negligible (urea) effect on canopy mean dark green color index. Once cumulative N inputs exceeded 47 kg ha^–1, creeping bentgrass fairway shoot growth and N nutrition were consistently increased by Civitas complementation of commercial liquid N fertilizer. Over the 2-yr study, absolute mean percent fertilizer N recovery from plots treated by Civitas-complemented foliar liquid N treatment exceeded their ’N only’ counterparts by 8.7%. Full article