Nitrogen, Volume 5, Issue 3 (September 2024) – 18 articles

At the optimum temperature, which is the ideal range in which seeds germinate most efficiently, seed germination may be lower than expected under favorable conditions, and this is indicative of seed dormancy. Also, germination may be enhanced by additional and interacting factors, such as nitrate and light. However, little is known about the interplay between temperature, nitrate, and seed germination. Using seeds from 22 accessions of four Plantago species that occupy distinct pedoclimates, we applied a factorial experimental design to assess the relationship between exogenously applied nitrate (KNO₃) and temperature on germination in a Petri dish experiment. The data explore the relationship between seed germination, temperatures, and seed- and maternal-source soil N content as either nitrite (NO₂⁻), nitrate (NO₃⁻), or ammonium (NH₄⁺). The interpretation also considered the total N and C contents of seeds, and the soil of the maternal plant (of the test seed) sources. Significant interspecific effects of nitrate and temperature on seed germination were observed. The capacity of nitrate to enhance final germination may be diminished substantially at supra-optimum temperatures, e.g., P. lagopus germination at 15 °C was 7% lower than that seen for water-only treatment. In contrast, at sub-optimum and alternating temperatures, nitrate enhanced final germination differentially across the species tested. This suggests a shift to enhanced germination at lower temperatures in the presence of sufficient soil nitrate, facilitating seedling establishment earlier in the growing season. The seeds of some Plantago species showed increased germination as a function of nitrate and temperature, particularly those of P. lagopus. The findings indicate that species (and genotype) responses correlated with the prevailing temperature and rainfall patterns of the locality; such local adaptation would ensure that seed germination and establishment occur during a period when environmental conditions are optimal. Full article

Crop residue decomposition is fundamental for ecosystems, influencing carbon cycling, organic matter accumulation, and promoting plant development through nutrient release. Therefore, this study aimed to ascertain the rate of decomposition of four commonly cultivated crops (alfalfa, maize, avocado, and eucalyptus) along the northern coast of Lima (Huaral) and in the Ancash Mountain range (Jangas) areas. Decomposition rates were assessed using mass loss from decomposition bags measuring 15 × 10 cm, filled with 10–15 g of material tailored to each species, and buried at a depth of approximately 5 cm. Sampling occurred every three months over a year, totaling four sampling events with three replicates each, resulting in ninety-six experimental units. The findings demonstrate that the decomposition rates and the release of nutrients were markedly greater in Huaral for maize and avocado. In contrast, these rates were notably elevated in Jangas for alfalfa and eucalyptus. The leaf litter of avocado and eucalyptus (tree) had periods of accumulation and release of heavy metals such as Cd. The initial C/N ratio was one of the main factors related to the nutrient decomposition rate; in contrast, there were no significant relationships with soil properties at the study sites. Full article

The use of cover crops (CCs) based on tropical legumes, including Crotalaria ochroleuca, Crotalaria juncea, Crotalaria spectabilis, and Cajanus cajan, represents a pivotal aspect of agricultural rotations. These crops facilitate the incorporation of nitrogen through biological nitrogen fixation (BNF), thereby reducing the necessity for synthetic nitrogen fertilizers. Nevertheless, the capacity for the BNF of these species in Uruguay is relatively modest. To address this limitation, an approach is proposed that involves the immobilization of nitrogen in the soil using a highly energetic material, such as sucrose. The objective of this study was to examine the impact of incorporating sucrose into typical Uruguayan soil on aboveground dry matter production, nitrogen accumulation, and nitrogen fixation by legumes utilized as CCs. The experiments involved the planting of C. ochroleuca, C. juncea, C. spectabilis, and C. cajan in pots containing either soil alone or soil mixed with sucrose and the subsequent maintenance of these in a plant growth chamber for a period of 90 days. The addition of sucrose had a positive impact, with nearly double the aboveground dry matter production and nitrogen content observed. The percentage of nitrogen derived from the atmosphere (%Ndfa) increased significantly in all species, rising from an average of 83% to 96% in the sucrose-amended soil compared to the control. In the case of C. juncea, there was a notable threefold increase in aboveground dry matter and nitrogen accumulation across different treatments, accompanied by a 26% rise in %Ndfa and a fourfold increase in nitrogen fixation amounts. These findings indicate that C. juncea has the potential to significantly enhance performance and ecosystem services in typical Uruguayan soil. Full article

Determining nutrient-release patterns of organic manures can give an estimate of the potential amount of nutrients that a given material can contribute to crops along with chemical fertiliser. Nutrients released from organic manure depend on several factors, and temperature is one of them. To evaluate how different types of conventional organic manures release nitrogen (N) under varying temperature conditions, an incubation study was conducted at the Bangladesh Agricultural Research Institute. Six organic manures—poultry manure (PM), vermicompost (VC), bio-slurry (BS), cowdung (CD), water-hyacinth compost (WHC), and rice straw compost (RSC)—were evaluated at three temperature regimes (15, 25, and 35 °C) to study the dynamics of N incubated for 330 days. The N release was significantly influenced by the interaction of organic manures and temperature regimes. Poultry manure-treated soil incubated at 35 °C had the highest mineralisation of all parameters than other manures. The mineralisation of N followed the order: PM > VC > BS > CD > WHC > RSC > control and 35 °C > 25 °C > 15 °C. Across different temperatures, the mineralisation rate of PM was 15–55% higher than that of other manures. At 35 °C, the mineralisation rate was 10% and 20% higher compared to 25 °C and 15 °C, respectively. The first-order kinetic models predicted the organic N release from manures satisfactorily. The findings of the present study enrich the understanding of N-release patterns under different temperature regimes that prevail in different crop growing seasons in Indo-Gangetic Plains, providing valuable data for researchers and policymakers interested in sustainable integrated nutrient management practices. Full article

The nitrogen/N dynamic is complex and affected by soil management (i.e., residue accumulation and correction/fertilization). In soil, most of the N is combined with organic matter (organic forms), but the N forms absorbed by plants are ammonium/NH₄⁺ and nitrate/NO₃⁻ (inorganic forms). The N recommendation for agriculture crops does not observe the N available in the soil (organic or inorganic), indicating a low efficiency in nitrogen management in soil. Based on the hypothesis that the stocks of NO₃⁻ and NH₄ can be used as indicative of N status in soil but with high variation according to soil factors (soil uses and management), the objective of the study was to (i) analyze the balance of nitrate and ammonium in tropical soil with different uses and management and (ii) use machine learning to explain the nitrogen dynamic in soil and the balance of nitrate and ammonium. The results showed that soil N stocks and pH promoted the formation of three clusters with the similarity between Cluster 1 (clay texture) and Cluster 2 (loam texture), represented by higher contents of nitrate as a result of high nitrification rate and lower contents of ammonium in soil. Cluster 3 (sand texture) was isolated with different N dynamics in the soil. In agricultural soils, the content of NO₃⁻ tends to be higher than the content of NH₄⁺. There is a high nitrification rate in clay soil explained by higher organic matter and clay content that promotes soil biology. Based on the results of machine learning, for clay and loam soil, the contents of NO₃ can be used as indicative of N status as a final result of nitrification rate and higher variation in soil. However, in sandy soil, NO₃ can not be used as indicative of N status due to N losses by leaching. Full article

Nitrogen indices could be used to evaluate organic and inorganic fertilization because they provide quantitative measures of nitrogen availability in the soil, allowing for a more accurate assessment of nutrient-management practices and optimization of crop yields. This study investigates the impact of different fertilization types and salinity on various soil parameters in fenugreek (Trigonella foenum-graecum L.) cultivation and nitrogen indices. A field experiment was established at the Agricultural University of Athens during the cropping period of 2018–2019 (CP I), 2019–2020 (CP II), and 2020–2021 (CP III) in a split-plot design with two main salinity treatments (high salinity, HS, and conventional salinity, CS) and five fertilization treatments (biocyclic–vegan humus soil (BHS), manure (FYM), compost (COMP), inorganic fertilization (11–15–15), and the control (C). The Nitrogen Balance Intensity (NBI) was statistically significantly affected by the factors of fertilization (p ≤ 0.01) and salinity (p ≤ 0.001) for CP I. The maximum NUEcrop value was recorded in the FYM treatment (0.83 ± 0.04) and the minimum in the COMP treatment (0.64 ± 0.04). Physiological efficiency (PE) was not significantly affected by any treatment for CP III. The fertilization factor significantly affected the NUEsoil index (p ≤ 0.001) for all three CPs. For CP I, the highest Nitrogen Uptake Efficiency (NUpE) value was recorded in the BHS treatment (27.08 ± 7.31) and the lowest in the C treatment (13.22 ± 7.31). There were no significant differences in CP I and CP II NUEbalance values among the NPK, BHS, and FYM treatments. These findings underscore the potential of organic fertilizers in addressing the global nitrogen challenge and promoting environmentally sustainable farming practices. Full article

Nitrogen is a very important nutrient in grass maintenance fertilization and therefore must be applied at the appropriate moment. The objective of this study was to identify the most responsive moment to nitrogen fertilization and to verify if root mass and the content of carbohydrates and nitrogen in roots influence the moment of fertilization in cultivars of Megathyrsus maximus (syn. Panicum maximum). This study was carried out simultaneously in a greenhouse using a completely randomized design, with sixteen treatments and five replications, in a 4×4 factorial design. The treatments consisted of four intervals between cultivar defoliation and nitrogen fertilization (0, 3, 6 and 9 days) and four Megathyrsus maximus cultivars, Mombasa, BRS Zuri, BRS Quenia and BRS Tamani, which were evaluated in five regrowth cycles. No difference in forage mass was observed among cultivars when fertilization was performed on days zero, three and nine after harvesting. On day nine, Mombasa showed a higher forage mass compared to BRS Tamani. Nitrogen content in the roots of Zuri decreased when fertilization was performed on the third day after defoliation, remaining constant in the other fertilization intervals. A linear reduction in root starch in BRS Zuri was observed, while in Mombasa cultivars, a linear increase was observed when fertilization was performed nine days after harvesting. Thus, nitrogen fertilization of BRS Tamani should be carried out closer to defoliation, while Mombasa, BRS Zuri and BRS Quenia can be fertilized up to nine days after harvesting, which results in greater flexibility regarding the moment of nitrogen fertilization. Full article

Global warming driven by climate change has profound impacts on nitrogen dynamics in terrestrial and aquatic ecosystems. The increased emissions of greenhouse gases alter the distribution and availability of nitrogen, which is a critical nutrient for all living organisms. This review examines the connections between climate change and nitrogen cycling, highlighting the adverse effects on ecosystem health and productivity. The proliferation of nitrogen pollution due to agricultural runoff, industrial effluents, and urban wastewater aggravates eutrophication, leading to significant environmental and economic consequences. The imbalance in nitrogen availability not only affects plant growth and soil fertility but also disrupts aquatic ecosystems, resulting in harmful algal blooms and hypoxic conditions. Effective mitigation and adaptation strategies are essential to addressing these challenges. Sustainable agricultural practices, such as precision farming and the use of slow-release fertilizers, along with robust policies and innovative technologies, like biochar application and nitrification inhibitors, are essential in managing nitrogen levels. This review underscores the importance of interdisciplinary approaches that involve integrating insights from ecology, agronomy, and the social sciences to develop comprehensive solutions. Future research should focus on long-term studies to assess the cumulative impacts of climatic changes on nitrogen availability and ecosystem health to guide policies and management practices for sustainable development. Full article

Most crops are fertilized with high amounts of nitrogen, and have an alarmingly low utilization efficiency. For this reason, the coordination between the fertilizer contribution and the nitrogen requirements of the crop is very important. Therefore, the objective of the present study was to establish new indices to determine nitrogen use efficiency (NUE), and to define the amount of assimilated nitrogen, which is used for the formation of green bean plant organs, fertilized with molybdenum nanofertilizer applied foliarly, and combined with edaphic fertilization of ammonium nitrate. The plants were grown in a greenhouse covered with anti-aphid mesh and irrigated with nutrient solution. Three sources of foliar molybdenum (Nanofertilizer, molybdenum Chelate and Sodium Molybdate) were applied in four doses of 0, 5, 10 and 20 ppm Mo, complemented with edaphic fertilization of NH₄NO₃ (0, 3, 6 and 12 mM of N). As results, the NUE indices showed that with the application of the nanofertilizer, the total biomass production increased 41.65% more than with the application of the chelate, and 36.84% more than with the application of molybdate. In summary, the dose that presented the highest efficiency was 6 mM-N with 10 ppm-Mo. Finally, it is concluded that the use of NUE indices is an important approach that evaluates the fate of nitrogen and accurately estimates plant yield. Full article

Comprehending the anaerobic nitrogen transformations, including denitrification, anaerobic ammonium oxidation (anammox), and anaerobic ammonium oxidation linked with iron reduction (Feammox) in soil, is essential for improving soil fertility and minimizing the environmental impacts of nitrogen loss. Despite this, research on anaerobic nitrogen transformations, particularly Feammox in paddy soil, is sparse. This study examined soil denitrification, anammox, and Feammox, along with their respective contributions to nitrogen loss in paddy soil at various depths, under different fertilization and irrigation treatments. It utilized 15N isotope labeling to investigate the limiting factors of these anaerobic nitrogen transformations and their interactions. The findings showed that denitrification rates ranged from 0.41 to 2.12 mg N kg⁻¹ d⁻¹, while anammox rates ranged from 0.062 to 0.394 mg N kg⁻¹ d⁻¹, contributing 84.3% to 88.1% and 11.8% to 15.7% of total soil nitrogen loss, respectively. Denitrification was identified as the predominant pathway for nitrogen loss across different soil depths. Fertilization and irrigation had more pronounced impacts on anaerobic nitrogen transformations than did soil depth, potentially affecting these processes through both abiotic and biotic pathways. This study identified significant correlations among the three types of anaerobic nitrogen transformations. These findings offer a theoretical foundation for optimizing nitrogen management strategies to mitigate losses in agricultural systems. Full article

Hemp (Cannabis sativa L.), renowned for its applications in environmental, industrial, and medicinal fields, is critically evaluated in this comprehensive review focusing on the impacts of chemical and organic fertilizers on its cultivation. As hemp re-emerges as a crop of economic significance, the choice between chemical and organic fertilization methods plays a crucial role in determining not only yield but also the quality and sustainability of production. This article examines the botanical characteristics of hemp, optimal growth conditions, and the essential biochemical processes for its cultivation. A detailed comparative analysis is provided, revealing that chemical fertilizers, while increasing yield by up to 20% compared to organic options, may compromise the concentration of key phytochemicals such as cannabidiol by approximately 10%, highlighting a trade-off between yield and product quality. The review presents quantitative assessments of nitrogen (N), phosphorus (P), and potassium (K) from both fertilizer types, noting that K significantly influences the synthesis of terpenes and cannabinoids, making it the most impactful element in the context of medicinal and aromatic hemp varieties. Optimal rates and timing of application for these nutrients are discussed, with a focus on maximizing efficiency during the flowering stage, where nutrient uptake directly correlates with cannabinoid production. Furthermore, the challenges associated with the U.S. industrial hemp market are addressed, noting that reducing production costs and improving processing infrastructure is essential for sustaining industry growth, especially given the slow expansion in fiber and cannabidiol markets due to processing bottlenecks. The review concludes that while chemical fertilizers may offer immediate agronomic benefits, transitioning towards organic practices is essential for long-term environmental sustainability and market viability. The future of the hemp industry, while promising, will depend heavily on advancements in genetic engineering, crop management strategies, and regulatory frameworks that better support sustainable cultivation practices. This nuanced approach is vital for the industry to navigate the complex trade-offs between productivity, environmental health, and economic viability in the global market. Full article

In this paper, the degradation of nitric oxide (NO) in an annular laboratory reactor is presented. Preliminary experiments were performed in an annular reactor (AR) under simulated solar irradiation. Titanium dioxide (TiO₂ P25) was used as a photocatalyst and immobilized on glass fibers mesh (GM) by the sol–gel method prepared from commercially available materials. The aim of the experiments was to remove NO from the air stream. The initial rate constant of the NO photocatalytic degradation was recognized to follow mass-transfer-controlled first-order kinetics. The results confirmed the photocatalytic reduction of NO to molecular nitrogen (N₂) and oxidation to nitrate. Therefore, the preliminary results obtained in this work are used for the development of a computational fluid dynamics (CFD) model (COMSOL Multiphysics v6.2). CFD calculations provide a good basis for sizing reactors at the semi-pilot and pilot levels for both indoor and outdoor air purification systems. Full article

Nitrogen is one of the most important macronutrients for crops, and, in conjunction with artificial intelligence algorithms, it is possible to estimate it with the aid of vegetation indices through remote sensing. Various indices were calculated and those with a correlation of ≥0.7 were selected for subsequent use in random forest, gradient boosting, and artificial neural networks to determine their relationship with nitrogen levels measured in the laboratory. Random forest showed no relationship, yielding an R² of zero; and gradient boosting and the classical method were similar with 0.7; whereas artificial neural networks yielded the best results with an R² of 0.93. Thus, estimating nitrogen levels using this algorithm is reliable, by feeding it with data from the Modified Chlorophyll Absorption Ratio Index, Transformed Chlorophyll Absorption Reflectance Index, Modified Chlorophyll Absorption Ratio Index/Optimized Soil Adjusted Vegetation Index, and Transformed Chlorophyll Absorption Ratio Index/Optimized Soil Adjusted Vegetation Index Full article

Reducing fertilizer-N rate, applying a nitrification inhibitor (NI), and incorporating straw are widely recommended to improve N use efficiency of crops and decrease N losses. A field ¹⁵N tracer study was conducted to compare their effectiveness on fertilizer-N fates during the maize growing season in Northeast China. The following six treatments were used: (1) no N fertilization (control); (2) 200 kg urea-N ha⁻¹ (100%N); (3) 200 kg urea-N ha⁻¹ and straw (100%N + S); (4) 160 kg urea-N ha⁻¹ (80%N); (5) 160 kg urea-N ha⁻¹ and NI (Nitrapyrin in this study) (80%N + NI); and (6) 160 kg urea-N ha⁻¹, NI, and straw (80%N + NI + S). The results showed that the five N fertilization treatments yielded 16–25% more grain and 39–60% more crop N uptake than the control, but the differences among the five treatments were not statistically significant. Compared with the 100%N, 20% fertilizer-N reduction (80%N) decreased the ¹⁵N concentration in topsoil and plant pools but increased the proportion of plant ¹⁵N recovery at harvesting (NUE_15N, 60% vs. 50%). Compared with the 80%N, NI co-application (80%N + NI) delayed soil nitrification and increased soil ¹⁵N retention at harvesting (52% vs. 36%), thereby decreasing NUE_15N significantly. Straw incorporation decreased fertilizer-N retention in soil compared with NI co-application because it promoted NUE_15N significantly. In conclusion, the results demonstrate that NI and straw additions are efficient strategies for stabilizing fertilizer-N in soils and potentially minimizing N loss; however, their effects on NUE_15N vary and the related mechanism must be further clarified in long-term trials. Full article

Urban sprawl poses a significant threat to urban stream water quality due to impermeabilization, reduced vegetation cover, and the release of diffuse pollutants. This study evaluates water quality in seven catchments in Santo André, SP, considering seasonality. Nutrient concentrations and in situ measurements were taken during both dry and rainy seasons. Comparisons were made using Kruskal–Wallis and Mann–Whitney tests. Streams showed significant differences in relation to water quality parameters. The Carapetuba, Jundiaí, and Apiaí streams were most adversely affected, underscoring the need for urgent water quality intervention (water conductivity above 500 μS/cm, dissolved oxygen below 2 mg/L, total dissolved carbon above 50 mg/L, and total dissolved nitrogen above 25 mg/L). Significant differences were observed across seasons. The dry season showed elevated temperatures (above 25 °C) and increased total dissolved carbon (above 50 mg/L) and nitrogen concentrations (above 30 mg/L), indicating reduced dilution effects from rainfall and heightened organic contamination. Conversely, the wet season demonstrated lower nutrient concentrations, emphasizing seasonal dynamics. Sustained, long-term monitoring of urban streams in Santo André and the implementation of sewage collection and treatment in irregular settlements are recommended. These measures are essential to mitigate the adverse impacts of urban expansion on water quality. Full article

Sulfur fertilization plays a crucial role in wheat (Triticum aestivum L.) production, influencing both protein concentration and grain yield. Wheat, being one of the most important food crops globally, requires efficient management of essential nutrients, including sulfur and nitrogen, to achieve optimal production. This study aimed to quantify the effect of sulfur fertilization on wheat protein concentration and grain yield and the relationship with nitrogen through two complementary methods: a comprehensive meta-analysis and a controlled greenhouse experiment. The meta-analysis, encompassing 55 studies from 20 countries with 545 comparisons, quantified the overall response of wheat to sulfur fertilization in diverse field environments, examining the effects based on soil texture and organic matter content. The greenhouse study investigated the effects of varying sulfur application rates and sources on protein concentration and grain yield and analyzed the relationship between sulfur and nitrogen concentrations in the grain. The meta-analysis showed overall positive effects of sulfur application on both protein concentration (2.1%) and grain yield (4.2%), with the magnitude of these effects varying based on soil texture and organic matter content. Sandy soils and soils with low organic matter content exhibited the most pronounced responses to sulfur fertilization. The greenhouse experiment revealed responses of both protein concentration and grain yield to increasing sulfur application rates, indicating an optimal rate beyond which additional sulfur may not provide further benefits. A strong positive correlation between sulfur and nitrogen concentrations in the grain highlighted their interdependence in wheat nutrition. These findings emphasize the importance of considering soil properties and the sulfur–nitrogen interaction when developing site-specific sulfur fertilization strategies for wheat. The results provide valuable insights for optimizing grain yield and protein concentration, contributing to more sustainable and efficient wheat production systems. Full article

The aim of this study was to economically estimate the effect of inoculation with Azospirillum brasilense (A. brasilense) associated with enhanced efficiency nitrogen fertilizers on corn yield cultivated in the Brazilian Amazon. The experimental design used was completely randomized, in a 2 × 3 × 5 factorial scheme, resulting from the combination of the presence and absence of seeds inoculated with A. brasilense, three sources of N (conventional urea, urea with NBPT, N-(n-butyl)thiophosphoric triamide, and polymer-coated urea), and five doses of N (0; 50; 100; 150; and 200 kg ha⁻¹ of N), with six replications. Inoculation with A. brasilense promoted profit in corn, regardless of dose and the source of N applied. The urea with NBPT provided better economic return compared to polymer-coated urea and conventional urea sources, and doses of N applied in topdressing that promoted the highest economic return were 100 and 150 kg ha⁻¹ of N, with an estimated increase of 62.33 and 135.53 bags ha⁻¹ and increase of BRL 3253.76 and BRL 7074.88 respectively, compared to the control treatment. Full article

Faidherbia albida can enhance the bio-physicochemical fertility of inherently infertile Arenosols. Changes in the soil ammonium (NH₄⁺)-to-nitrate (NO₃⁻) ratio have agricultural, environmental, and ecological implications. Thus, the present study mainly examined the changes in Arenosol NH₄⁺/NO₃⁻ ratios, as influenced by varying Faidherbia albida tree age classes. We collected 40 composite soil samples (4 tree age classes^×2 soil depths^×5 replications) from 0 to 15 and 15 to 30 cm soil depths following core and auger sampling techniques. Analyses of variance have shown that the highest NH₄⁺/NO₃⁻ ratios for soil under the old tree canopies are followed by the medium age. In contrast, the significantly lowest NH₄⁺/NO₃⁻ ratios were recorded for soil out-of-canopy. Pearson correlation analysis revealed that the NH₄⁺/NO₃⁻ ratio was strongly and positively correlated with clay content, total nematode abundance, the fungi/bacterial biomass ratio, cation exchange capacity, microbial biomass carbon, total nitrogen, and soil organic carbon but negative for sand content, bulk density, and pH. The increment in the plant-available forms of nitrogen might be attributed to the accumulation of biologically fixed nitrogen by the Faidherbia albida tree–Rhizobium bacteria symbiosis. The NH₄⁺/NO₃⁻ ratio approached one in soil under the old Faidherbia albida trees. The findings suggest that (1) the ability of soil to retain NH₄⁺ increased and (2) the rate of nitrification might be decreased due to inhibition of nitrification by direct and indirect effects of the tree on the nitrifying group of bacteria. The increment in the NH₄⁺/NO₃⁻ ratio could also be due to the lowering of the soil’s pH in the older Faidherbia albida trees because lower pH is known to inhibit the activities of nitrifying bacteria. Moreover, maintaining older Faidherbia albida trees in farmlands could contribute to retaining nitrogen and trigger below- and above-ground communities’ successions and ultimately surpass the productivity of arid and semi-arid Arenosols. Full article