The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics.

BACKGROUND: The presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1). RESULTS: The study examined the effects of nitrogen (NH4+ and NO3-) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3-). Specifically, the highest levels of oxygen significantly increased root growth in NO3--fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3- exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3--fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3--grown plants. Interestingly, the NO3--fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1. CONCLUSION: This study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3- -supplied culture media or nutrient solutions, respectively.

[Characteristics of Epiphytic Bacterial Community on Submerged Macrophytes in Water Environment Supplemented with Reclaimed Water].

Biofilms attached to submerged macrophytes play an important role in improving the water quality of the water environment supplemented with reclaimed water. In order to explore the effects of reclaimed water quality and submerged macrophyte species on the characteristics of an epiphytic bacterial community, different types of submerged macrophytes were selected as research objects in this study. 16S rRNA high-throughput sequencing technology was used on the epiphytic bacteria and the surrounding environmental samples to analyze the bacterial community structure and functional genes. The results showed that approximately 20%-35% of the nitrogen and phosphorus nutrients were absorbed and utilized in the water environment supplemented with reclaimed water. However, the COD, turbidity, and chroma of the downstream water were significantly increased. The bacterial community of the biofilms attached to submerged macrophytes was significantly different from that in the surrounding environment (soil, sediment, and water body) and in the activated sludge that was treated by reclaimed water. In terms of bacterial community diversity, the richness and diversity were significantly lower than those of soil and sediment but higher than those of plankton bacteria in water. In terms of bacterial community composition, dominant genera and corresponding abundances were also different from those of other samples. The main dominant bacterial genera were Sphingomonas, Aeromonas, Pseudomonas, and Acinetobacter, accounting for 7%-40%, respectively. Both macrophyte species and the quality of reclaimed water (BOD5, TN, NH4+-N, and TP) could affect the bacterial community. However, the effect of water quality of the bacterial community was greater than that of macrophytes species. Additionally, the quality of reclaimed water also affected the abundance of functional genes in the bacterial community, and the relative abundance of nitrogen and phosphorus cycling functional genes was higher in areas with higher nitrogen and phosphorus concentrations.

[Effects of Controlled-release Blended Fertilizer on Crop Yield and Greenhouse Gas Emissions in Wheat-maize Rotation System].

The increasing use of nitrogen fertilizers exerts extreme pressure on the environment (e.g., greenhouse gas emissions, GHGs) for winter wheat-summer maize rotation systems in the North China Plain. The application of controlled-release fertilizers is considered as an effective measure to improve crop yield and nitrogen fertilizer utilization efficiency. To explore the impact of one-time fertilization of controlled-release blended fertilizer on crop yield and GHGs of a wheat-maize rotation system, field experiments were carried out in Dezhou Modern Agricultural Science and Technology Park from 2020 to 2022. Five treatments were established for both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 5:5 and 3:7, respectively), and CRU2 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 7:3 and 5:5, respectively). The differences in yield, nitrogen fertilizer utilization efficiency, fertilization economic benefits, and GHGs among different treatments were compared and analyzed. The results showed that nitrogen application significantly increased the single season and annual crop yields of the wheat-maize rotation system (P < 0.05). Compared with those of FFP, the CRU1 and CRU2 treatments increased the yields of summer maize by 0.4% to 5.6%, winter wheat by -5.4% to 4.1%, and annual yields by -1.1% to 3.9% (P > 0.05). N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (NPFP) were increased by -8.6%-43.4%, 2.05-6.24 kg·kg-1, and 4.24-10.13 kg·kg-1, respectively. Annual net income increased by 0.2% to 6.3%. Nitrogen application significantly increased the annual emissions of soil N2O and CO2 in the rotation system (P < 0.05) but had no effect on the annual emissions of CH4 (except for in the FFP treatment in the first year). The annual total N2O emissions under the CRU1 and CRU2 treatments were significantly reduced by 23.4% to 30.2% compared to those under the FFP treatment (P < 0.05). Additionally, nitrogen application significantly increased the annual global warming potential (GWP) of the rotation system (P < 0.05), but the intensity of greenhouse gas emissions was reduced due to the increase in crop yields. Compared with that under FFP, the annual GWP under the CRU1 and CRU2 treatments decreased by 9.6% to 11.5% (P < 0.05), and the annual GHGs decreased by 11.2% to 13.8% (P > 0.05). In summary, the one-time application of controlled-release blended fertilizer had a positive role in improving crop yield and economic benefits, reducing nitrogen fertilizer input and labor costs, and GHGs, which is an effective nitrogen fertilizer management measure to promote cleaner production of food crops in the North China Plain.

[Effect of Biochar on NO3--N Transport in Loessial Soil and Its Simulation].

The objective of this study was to explore the effects of different amounts of biochar on the migration process and characteristics of NO3--N in loessial soil. In this study, six groups of mixed soil samples with biochar and loessial soil mass ratios of 0% (T0), 1% (T1), 2% (T2), 3% (T3), 4% (T4), and 5% (T5) were used as research objects. NO3--N was used as the tracer. Through the indoor soil column solute transport simulation tests, the effects of different biochar application amounts on the NO3--N transport process in loessial soil were simulated and studied. The results showed that the breakthrough curve of NO3--N in loessial soil shifted to the right with the increasing of biochar application, and the peak value gradually decreased. The initial penetration time, complete penetration time, and total penetration time increased with the increasing of biochar application amount. The total penetration time of NO3- in the T1, T2, T3, T4, and T5 treatments was 1.26, 2.31, 2.72, 3.22, and 3.57 times that of T0, respectively. The R2 was > 0.997 and RMSE was < 2.083 of the two-zone model (TRM). Compared with the convection-dispersion equation (CDE), the TRM model had higher fitting accuracy and could better simulate the NO3--N migration process in loessial soil after the application of different contents of biochar. The analysis of the fitting parameters of the TRM model showed that the average pore velocity, hydrodynamic dispersion coefficient, and water content ratio in the movable zone gradually decreased with the increasing of biochar application, whereas the dispersion and mass exchange coefficient showed an increasing trend. The results showed that biochar application could effectively enhance the ability of loessial soil to fix NO3--N, reduce the leakage of NO3--N to groundwater, and play an important role in maintaining soil fertility and preventing groundwater pollution.

[Effects of Biochar on Growth and Pollutant Accumulation of Lettuce in Soil Co-contaminated with Tetracycline and Copper].

Through lettuce potting experiments, the effects of different types of biochar (apple branch, corn straw, and modified sorghum straw biochar with phosphoric acid modification) on lettuce growth under tetracycline (TC) and copper (Cu) co-pollution were investigated. The results showed that compared with those under CK, the addition of biochar treatment significantly increased the plant height, root length, shoot fresh weight, and root fresh weight of lettuce (P < 0.05). The addition of different biochars significantly increased the nitrate nitrogen, chlorophyll, and soluble protein content in lettuce physiological indicators to varying degrees, while also significantly decreasing the levels of malondialdehyde, proline content, and catalase activity. The effects of biochar on lettuce physiological indicators were consistent during both the seedling and mature stages. Compared with those in CK, the addition of biochar resulted in varying degrees of reduction in the TC and Cu contents of both the aboveground and underground parts of lettuce. The aboveground TC and Cu levels decreased by 2.49%-92.32% and 12.79%-36.47%, respectively. The underground TC and Cu levels decreased by 12.53%-55.64% and 22.41%-42.29%, respectively. Correlation analysis showed that nitrate nitrogen, chlorophyll, and soluble protein content of lettuce were negatively correlated with TC content, whereas malondialdehyde, proline content, and catalase activity were positively correlated with TC content. The resistance genes of lettuce were positively correlated with TC content (P < 0.05). In general, modified biochar was found to be more effective in improving lettuce growth quality and reducing pollutant accumulation compared to unmodified biochar, with modified sorghum straw biochar showing the best remediation effect.

Nitrospirillum viridazoti sp. nov., an Efficient Nitrogen-Fixing Species Isolated from Grasses.

A group of Gram-negative plant-associated diazotrophic bacteria belonging to the genus Nitrospirillum was investigated, including both previously characterized and newly isolated strains from diverse regions and biomes, predominantly in Brazil. Phylogenetic analysis of 16S rRNA and recA genes revealed the formation of a distinct clade consisting of thirteen strains, separate from the formally recognized species N. amazonense (the closest species) and N. iridis. Comprehensive taxonomic analyses using the whole genomes of four strains (BR 11140T = AM 18T = Y-2T = DSM 2788T = ATCC 35120T, BR 11142T = AM 14T = Y-1T = DSM 2787T = ATCC 35119T, BR 11145 = CBAmC, and BR 12005) supported the division of these strains into two species: N. amazonense (BR 11142 T and BR 12005) and a newly proposed species (BR 11140 T and BR 11145), distinct from N. iridis. The phylogenomic analysis further confirmed the presence of the new Nitrospirillum species. Additionally, MALDI-TOF MS analysis of whole-cell mass spectra provided further evidence for the differentiation of the proposed Nitrospirillum species, separate from N. amazonense. Analysis of chemotaxonomy markers (i.e., genes involved in fatty acid synthesis, metabolism and elongation, phospholipid synthesis, and quinone synthesis) revealed that the new species highlights high similarity and evolutionary convergence with other Nitrospirillum species. This new species exhibited nitrogen fixation ability in vitro, it has similar NifHDK protein phylogeny position with the closest species, lacked denitrification capability, but possessed the nosZ gene, enabling N2O reduction, distinguishing it from the closest species. Despite being isolated from diverse geographic regions, soil types, and ecological niches, no significant phenotypic or physiological differences were observed between the proposed new species and N. amazonense. Based on these findings, a new species, Nitrospirillum viridazoti sp. nov., was classified, with the strain BR 11140T (DSM 2788T, ATCC 35120T) designated as the type strain.

Overexpression of GmPAP4 Enhances Symbiotic Nitrogen Fixation and Seed Yield in Soybean under Phosphorus-Deficient Condition.

Legume crops establish symbiosis with nitrogen-fixing rhizobia for biological nitrogen fixation (BNF), a process that provides a prominent natural nitrogen source in agroecosystems; and efficient nodulation and nitrogen fixation processes require a large amount of phosphorus (P). Here, a role of GmPAP4, a nodule-localized purple acid phosphatase, in BNF and seed yield was functionally characterized in whole transgenic soybean (Glycine max) plants under a P-limited condition. GmPAP4 was specifically expressed in the infection zones of soybean nodules and its expression was greatly induced in low P stress. Altered expression of GmPAP4 significantly affected soybean nodulation, BNF, and yield under the P-deficient condition. Nodule number, nodule fresh weight, nodule nitrogenase, APase activities, and nodule total P content were significantly increased in GmPAP4 overexpression (OE) lines. Structural characteristics revealed by toluidine blue staining showed that overexpression of GmPAP4 resulted in a larger infection area than wild-type (WT) control. Moreover, the plant biomass and N and P content of shoot and root in GmPAP4 OE lines were also greatly improved, resulting in increased soybean yield in the P-deficient condition. Taken together, our results demonstrated that GmPAP4, a purple acid phosphatase, increased P utilization efficiency in nodules under a P-deficient condition and, subsequently, enhanced symbiotic BNF and seed yield of soybean.

Evaluation of internal markers in digestibility estimation for sheep and goats.

The objective of this study was to compare the indirect methods of obtaining digestibility with the direct method of total fecal collection to estimate the apparent digestibility of nutrients in sheep and goats supplemented with non-protein nitrogen. Five goats and five sheep with no defined racial pattern were used, distributed in two 5 × 5 Latin squares, with split plots, considering the diets as plots and the apparent digestibility determination methodologies as subplots. The diets were composed of buffelgrass hay and the addition, via ruminal infusion, of increasing amounts of nitrogen supplementation in order to gradually raise the CP level of the basal diet in intervals of 2% points, that is, + 2, +4, + 6 and + 8%. Samples of the feeds offered, and the leftovers were collected daily during the five days of collection to determine the nutrient intake, as well as the total collection of feces to determine the apparent digestibility of the nutrients. The amount of fecal dry matter excreted was estimated by the concentration of Indigestible Acid Detergent Fiber (ADFi), Indigestible Neutral Detergent Fiber (NDFi), Indigestible Dry Matter at 244 h (DMi 244 h) and Indigestible Dry Matter at 264 h (DMi 264 h). Among the evaluated markers, DMi 264 h had the lowest accuracy in estimating fecal excretion and nutrient digestibility. For the goat species, the markers ADFi and DMi 244 h proved to be able to adequately predict fecal excretion and digestibility indices, while NDFi stood out for both species. Among the evaluated markers, NDFi is the one that most accurately estimates the nutrient digestibility of the diet for goats and sheep.

Glutamate production from aerial nitrogen using the nitrogen-fixing bacterium Klebsiella oxytoca.

Glutamate is an essential biological compound produced for various therapeutic and nutritional applications. The current glutamate production process requires a large amount of ammonium, which is generated through the energy-consuming and CO2-emitting Haber-Bosch process; therefore, the development of bio-economical glutamate production processes is required. We herein developed a strategy for glutamate production from aerial nitrogen using the nitrogen-fixing bacterium Klebsiella oxytoca. We showed that a simultaneous supply of glucose and citrate as carbon sources enhanced the nitrogenase activity of K. oxytoca. In the presence of glucose and citrate, K. oxytoca strain that was genetically engineered to increase the supply of 2-oxoglutarate, a precursor of glutamate synthesis, produced glutamate extracellularly more than 1 g L-1 from aerial nitrogen. This strategy offers a sustainable and eco-friendly manufacturing process to produce various nitrogen-containing compounds using aerial nitrogen.

Impact of nitrogen fertilizer sustainability on corn crop yield: the role of beneficial microbial inoculation interactions.

BACKGROUND: Considering the challenges posed by nitrogen (N) pollution and its impact on food security and sustainability, it is crucial to develop management techniques that optimize N fertilization in croplands. Our research intended to explore the potential benefits of co-inoculation with Azospirillum brasilense and Bacillus subtilis combined with N application rates on corn plants. The study focused on evaluating corn photosynthesis-related parameters, oxidative stress assay, and physiological nutrient use parameters. Focus was placed on the eventual improved capacity of plants to recover N from applied fertilizers (AFR) and enhance N use efficiency (NUE) during photosynthesis. The two-year field trial involved four seed inoculation treatments (control, A. brasilense, B. subtilis, and A. brasilense + B. subtilis) and five N application rates (0 to 240 kg N ha-1, applied as side-dress). RESULTS: Our results suggested that the combined effects of microbial consortia and adequate N-application rates played a crucial role in N-recovery; enhanced NUE; increased N accumulation, leaf chlorophyll index (LCI), and shoot and root growth; consequently improving corn grain yield. The integration of inoculation and adequate N rates upregulated CO2 uptake and assimilation, transpiration, and water use efficiency, while downregulated oxidative stress. CONCLUSIONS: The results indicated that the optimum N application rate could be reduced from 240 to 175 kg N ha-1 while increasing corn yield by 5.2%. Furthermore, our findings suggest that replacing 240 by 175 kg N ha-1 of N fertilizer (-65 kg N ha-1) with microbial consortia would reduce CO2 emission by 682.5 kg CO2 -e ha-1. Excessive N application, mainly with the presence of beneficial bacteria, can disrupt N-balance in the plant, alter soil and bacteria levels, and ultimately affect plant growth and yield. Hence, highlighting the importance of adequate N management to maximize the benefits of inoculation in agriculture and to counteract N loss from agricultural systems intensification.

Unveiling unique microbial nitrogen cycling and nitrification driver in coastal Antarctica.

Largely removed from anthropogenic delivery of nitrogen (N), Antarctica has notably low levels of nitrogen. Though our understanding of biological sources of ammonia have been elucidated, the microbial drivers of nitrate (NO3-) cycling in coastal Antarctica remains poorly understood. Here, we explore microbial N cycling in coastal Antarctica, unraveling the biological origin of NO3- via oxygen isotopes in soil and lake sediment, and through the reconstruction of 1968 metagenome-assembled genomes from 29 microbial phyla. Our analysis reveals the metabolic potential for microbial N2 fixation, nitrification, and denitrification, but not for anaerobic ammonium oxidation, signifying a unique microbial N-cycling dynamic. We identify the predominance of complete ammonia oxidizing (comammox) Nitrospira, capable of performing the entire nitrification process. Their adaptive strategies to the Antarctic environment likely include synthesis of trehalose for cold stress, high substrate affinity for resource utilization, and alternate metabolic pathways for nutrient-scarce conditions. We confirm the significant role of comammox Nitrospira in the autotrophic, nitrification process via 13C-DNA-based stable isotope probing. This research highlights the crucial contribution of nitrification to the N budget in coastal Antarctica, identifying comammox Nitrospira clade B as a nitrification driver.

Potential Role of the Anammoxosome in the Adaptation of Anammox Bacteria to Salinity Stress.

The underlying adaptative mechanisms of anammox bacteria to salt stress are still unclear. The potential role of the anammoxosome in modulating material and energy metabolism in response to salinity stress was investigated in this study. The results showed that anammox bacteria increased membrane fluidity and decreased mechanical properties by shortening the ladderane fatty acid chain length of anammoxosome in response to salinity shock, which led to the breakdown of the proton motive force driving ATP synthesis and retarded energy metabolism activity. Afterward, the fatty acid chain length and membrane properties were recovered to enhance the energy metabolic activity. The relative transmission electron microscopy (TEM) area proportion of anammoxosome decreased from 55.9 to 38.9% under salinity stress. The 3D imaging of the anammox bacteria based on Synchrotron soft X-ray tomography showed that the reduction in the relative volume proportion of the anammoxosome and the concave surfaces was induced by salinity stress, which led to the lower energy expenditure of the material transportation and provided more binding sites for enzymes. Therefore, anammox bacteria can modulate nitrogen and energy metabolism by changing the membrane properties and morphology of the anammoxosome in response to salinity stress. This study broadens the response mechanism of anammox bacteria to salinity stress.

Unveiling Microbial Nitrogen Metabolism in Rivers using a Machine Learning Approach.

Microbial nitrogen metabolism is a complicated and key process in mediating environmental pollution and greenhouse gas emissions in rivers. However, the interactive drivers of microbial nitrogen metabolism in rivers have not been identified. Here, we analyze the microbial nitrogen metabolism patterns in 105 rivers in China driven by 26 environmental and socioeconomic factors using an interpretable causal machine learning (ICML) framework. ICML better recognizes the complex relationships between factors and microbial nitrogen metabolism than traditional linear regression models. Furthermore, tipping points and concentration windows were proposed to precisely regulate microbial nitrogen metabolism. For example, concentrations of dissolved organic carbon (DOC) below tipping points of 6.2 and 4.2 mg/L easily reduce bacterial denitrification and nitrification, respectively. The concentration windows for NO3--N (15.9-18.0 mg/L) and DOC (9.1-10.8 mg/L) enabled the highest abundance of denitrifying bacteria on a national scale. The integration of ICML models and field data clarifies the important drivers of microbial nitrogen metabolism, supporting the precise regulation of nitrogen pollution and river ecological management.

Climate, litter quality and radiation duration jointly regulate the net effect of UV radiation on litter decomposition.

Photodegradation via ultraviolet (UV) radiation is an important factor driving plant litter decomposition. Despite increasing attention to the role of UV photodegradation in litter decomposition, the specific impact of UV radiation on the plant litter decomposition stage within biogeochemical cycles remains unclear at regional and global scales. To clarify the variation rules of magnitude of UV effect on plant litter decomposition and their regulatory factors, we conducted a meta-analysis based on 54 published papers. Our results indicated that UV significantly promoted the mass loss of litter by facilitating decay of carbonaceous fractions and release of nitrogen and phosphorus. The promotion effect varied linearly or non-linearly with the time that litter exposed to UV, and with climatic factors. The UV effect on litter decomposition decreased first than increased on precipitation and temperature gradients, reaching its minimum in the area with a precipitation of 400-600 mm, and a temperature of 15-20 °C. This trend might be attributed to a potential equilibrium between the photofacilitation and photo-inhibition effects of UV under this condition. This variation in UV effect on precipitation gradient was in agreement with the fact that UV photodegradation effect was weakest in grassland ecosystems compared to that in forest and desert ecosystems. In addition, initial litter quality significantly influenced the magnitude of UV effect, but had no influence on the correlation between UV effect and climate gradient. Litter with lower initial nitrogen and lignin content shown a greater photodegradation effect, whereas those with higher hemicellulose and cellulose content had a greater photodegradation effect. Our study provides a comprehensive understanding of photodegradation effect on plant litter decomposition, indicates potentially substantial impacts of global enhancements of litter decomposition by UV, and highlights the necessity to quantify the contribution of photochemical minerallization pathway and microbial degradation pathway in litter decomposition.

Synthesis of struvite-enriched slow-release fertilizer using magnesium-modified biochar: Desorption and leaching mechanisms.

To improve the retention and slow-release abilities of nitrogen (N) and phosphorus (P), an 82 %-purity struvite fertilizer (MAP-BC) was synthesized using magnesium-modified biochar and a solution with a 2:1 concentration ratio of NH4+ to PO43- at a pH of 8. Batch microscopic characterizations and soil column leaching experiments were conducted to study the retention and slow-release mechanisms and desorption kinetics of MAP-BC. The slow-release mechanism revealed that the dissolution rate of high-purity struvite was the dominant factor of NP slow release. The re-adsorption of NH4+ and PO43- by biochar and unconsumed MgO prolonged slow release. Mg2+ ionized by MgO could react with PO43- released from struvite to form Mg3(PO4)2. The internal biochar exhibited electrostatic attraction and pore restriction towards NH4+, while magnesium modification and nutrient loading formed a physical antioxidant barrier that ensured long-term release. The water diffusion experiment showed a higher cumulative release rate for PO43- compared to NH4+, whereas in soil column leaching, the trend was reversed, suggesting that soil's competitive adsorption facilitated the desorption of NH4+ from MAP-BC. During soil leaching, cumulative release rates of NH4+ and PO43- from chemical fertilizers were 3.55-3.62 times faster than those from MAP-BC. The dynamic test data for NH4+ and PO43- in MAP-BC fitted the Ritger-Peppas model best, predicting release periods of 163 days and 166 days, respectively. The leaching performances showed that MAP-BC reduced leaching solution volume by 5.58 % and significantly increased soil large aggregates content larger than 0.25 mm by 24.25 %. The soil nutrients retention and pH regulation by MAP-BC reduced leaching concentrations of NP. Furthermore, MAP-BC significantly enhanced plant growth, and it is more suitable as a NP source for long-term crops. Therefore, MAP-BC is expected to function as a long-term and slow-release fertilizer with the potential to minimize NP nutrient loss and replace part of quick-acting fertilizer.

Risks posed by invasive species to the provision of ecosystem services in Europe.

Invasive species significantly impact biodiversity and ecosystem services, yet understanding these effects at large spatial scales remains a challenge. Our study addresses this gap by assessing the current and potential future risks posed by 94 invasive species to seven key ecosystem services in Europe. We demonstrate widespread potential impacts, particularly on outdoor recreation, habitat maintenance, crop provisioning, and soil and nitrogen retention. Exposure to invasive species was higher in areas with lower provision of ecosystem services, particularly for regulating and cultural services. Exposure was also high in areas where ecosystem contributions to crop provision and nitrogen retention were at their highest. Notably, regions vital for ecosystem services currently have low invasion suitability, but face an average 77% increase in potential invasion area. Here we show that, while high-value ecosystem service areas at the highest risk represent a small fraction of Europe (0-13%), they are disproportionally important for service conservation. Our study underscores the importance of monitoring and protecting these hotspots to align management strategies with international biodiversity targets, considering both invasion vulnerability and ecosystem service sustainability.

Evaluating the agronomic efficiency of alternative phosphorus sources applied in Brazilian tropical soils.

Understanding the efficacy of alternative phosphorus (P) sources in tropical soils is crucial for sustainable farming, addressing resource constraints, mitigating environmental impact, improving crop productivity, and optimizing soil-specific solutions. While the topic holds great importance, current literature falls short in providing thorough, region-specific studies on the effectiveness of alternative P sources in Brazilian tropical soils for maize cultivation. Our aim was to assess the agronomic efficiency of alternative P sources concerning maize crop (Zea mays L.) attributes, including height, shoot dry weight, stem diameter, and nutrient accumulation, across five Brazilian tropical soils. In greenhouse conditions, we carried out a randomized complete block design, investigating two factors (soil type and P sources), evaluating five tropical soils with varying clay contents and three alternative sources of P, as well as a commercial source and a control group. We evaluated maize crop attributes such as height, dry weight biomass, and nutrient accumulation, P availability and agronomic efficiency. Our results showed that, although triple superphosphate (TSP) exhibited greater values than alternative P sources (precipitated phosphorus 1, precipitated phosphorus 2 and reactive phosphate) for maize crop attributes (e.g., height, stem diameter, shoot dry weight and phosphorus, nitrogen, sulfur, calcium and magnesium accumulation). For instance, PP1 source increased nutrient accumulation for phosphorus (P), nitrogen (N), and sulfur (S) by 37.05% and 75.98% (P), 34.39% and 72.07% (N), and 41.94% and 72.69% (S) in comparison to PP2 and RP, respectively. Additionally, PP1 substantially increased P availability in soils with high clay contents 15 days after planting (DAP), showing increases of 61.90%, 99.04%, and 38.09% greater than PP2, RP, and TSP. For Ca and Mg accumulation, the highest values were found in the COxisol2 soil when PP2 was applied, Ca = 44.31% and 69.48%; and Mg = 46.23 and 75.79%, greater than PP1 and RP, respectively. Finally, the highest values for relative agronomic efficiency were observed in COxisol2 when PP1 was applied. The precipitated phosphate sources (PP1 and PP2) exhibited a similar behavior to that of the commercial source (TSP), suggesting their potential use to reduce reliance on TSP fertilization, especially in soils with low clay contents. This study emphasized strategies for soil P management, aimed at assisting farmers in enhancing maize crop productivity while simultaneously addressing the effectiveness of alternative P sources of reduced costs.

Effects of Lactobacillus-fermented low-protein diets on the growth performance, nitrogen excretion, fecal microbiota and metabolomic profiles of finishing pigs.

This study investigated the effects of Lactobacillus-fermented low-protein diet on the growth performance, nitrogen balance, fecal microbiota, and metabolomic profiles of finishing pigs. A total of 90 finishing pigs were assigned to one of three dietary treatments including a normal protein diet (CON) as well as two experimental diets in which a low-protein diet supplemented with 0 (LP) or 1% Lactobacillus-fermented low-protein feed (FLP). In comparison with CON, the LP and FLP significantly increased average daily gain (P = 0.044), significantly decreased feed to gain ratio (P = 0.021), fecal nitrogen (P < 0.01), urine nitrogen (P < 0.01), and total nitrogen (P < 0.01), respectively. The LP group exhibited increased abundances of unclassified_f_Selenomonadaceae, Coprococcus, Faecalibacterium, and Butyricicoccus, while the abundances of Verrucomicrobiae, Verrucomicrobiales, Akkermansiaceae, and Akkermansia were enriched in the FLP group. Low-protein diet-induced metabolic changes were enriched in sesquiterpenoid and triterpenoid biosynthesis and Lactobacillus-fermented low-protein feed-induced metabolic changes were enriched in phenylpropanoid biosynthesis and arginine biosynthesis. Overall, low-protein diet and Lactobacillus-fermented low-protein diet improved the growth performance and reduce nitrogen excretion, possibly via altering the fecal microbiota and metabolites in the finishing pigs. The present study provides novel ideas regarding the application of the low-protein diet and Lactobacillus-fermented low-protein diet in swine production.

Algal-bacterial shortcut nitrogen removal model with seasonal light variations.

The algal-bacterial shortcut nitrogen removal (ABSNR) process can be used to treat high ammonia strength wastewaters without external aeration. However, prior algal-bacterial SNR studies have been conducted under fixed light/dark periods that were not representative of natural light conditions. In this study, laboratory-scale photo-sequencing batch reactors (PSBRs) were used to treat anaerobic digester sidestream under varying light intensities that mimicked summer and winter conditions in Tampa, FL, USA. A dynamic mathematical model was developed for the ABSNR process, which was calibrated and validated using data sets from the laboratory PSBRs. The model elucidated the dynamics of algal and bacterial biomass growth under natural illumination conditions as well as transformation processes for nitrogen species, oxygen, organic and inorganic carbon. A full-scale PSBR with a 1.2 m depth, a 6-day hydraulic retention time (HRT) and a 10-day solids retention time (SRT) was simulated for treatment of anaerobic digester sidestream. The full-scale PSBR could achieve >90% ammonia removal, significantly reducing the nitrogen load to the mainstream wastewater treatment plant (WWTP). The dynamic simulation showed that ABSNR process can help wastewater treatment facilities meet stringent nitrogen removal standards with low energy inputs.

The fundamental role of pH in CH4 bioconversion into polyhydroxybutyrate in mixed methanotrophic cultures.

Climate change and plastic pollution are likely the most relevant challenges for the environment in the 21st century. Developing cost-effective technologies for the bioconversion of methane (CH4) into polyhydroxyalkanoates (PHAs) could simultaneously mitigate CH4 emissions and boost the commercialization of biodegradable polymers. Despite the fact that the role of temperature, nitrogen deprivation, CH4:O2 ratio or micronutrients availability on the PHA accumulation capacity of methanotrophs has been carefully explored, there is still a need for optimization of the CH4-to-PHA bioconversion process prior to becoming a feasible platform in future biorefineries. In this study, the influence of different cultivation broth pH values (5.5, 7, 8.5 and 10) on bacterial biomass growth, CH4 bioconversion rate, PHA accumulation capacity and bacterial community structure was investigated in a stirred tank bioreactor under nitrogen deprivation conditions. Higher CH4 elimination rates were obtained at increasing pH, with a maximum value of 50.4 ± 2.7 g CH4·m-3·h-1 observed at pH 8.5. This was likely mediated by an increased ionic strength in the mineral medium, which enhanced the gas-liquid mass transfer. Interestingly, higher PHB accumulations were observed at decreasing pH, with the highest PHB contents recorded at a pH 5.5 (43.7 ± 3.4 %w·w-1). The strong selective pressure of low pH towards the growth of Type II methanotrophic bacteria could explain this finding. The genus Methylocystis increased its abundance from 34 % up to 85 and 90 % at pH 5.5 and 7, respectively. On the contrary, Methylocystis was less abundant in the community enriched at pH 8.5 (14 %). The accumulation of intracellular PHB as energy and carbon storage material allowed the maintenance of high CH4 biodegradation rates during 48 h after complete nitrogen deprivation. The results here obtained demonstrated for the first time a crucial and multifactorial role of pH on the bioconversion performance of CH4 into PHA.