Nutrients Nitrogen Research Articles

Interactive effect of rhizobacterium Bacillus sp. strain MRD-17 and macro-nutrients on the amelioration of drought stress in mustard (Brassica juncea L.)

ABSTRACT Drought is a major abiotic stress in mustard. In the present investigation, the interactive effects of rhizobacterium Bacillus sp. MRD-17 and nutrients nitrogen, phosphorus, and potassium (N, P, K), 100% and 50% of the recommended dose of fertiliser (RDF) on shoot-root growth and nutrient uptake by mustard under well-watered (−0.33 bar) and water deficit (−8 bar) conditions were determined. Drought stress for 30 days, reduced root growth, but rhizobacterial inoculation under drought and nutrient stress improved root viability (73%, and 39%, respectively) and architecture, nitrate reductase (20% and 12%, respectively) and glutamine synthetase activity (21% and 14%, respectively), shoot nitrogen, phosphorus, and potassium and seed K content. The protective effects of Bacillus sp. MRD-17 to mustard under drought stress was also accompanied by decreased acid phosphatase activity. However, rhizobacterial and macro-nutrient interactions had no impact on seed N and P content on drought and nutrient-stressed plants. Therefore, in terms of plant growth and nutrient uptake, the efficiency of Bacillus sp. MRD-17 was dependent on the soil nutrient status. Furthermore, rhizobacterial application might facilitate a higher uptake of water and nutrients by the plant from the soil and thus sustain crop productivity under water and nutrient stress scenarios.

Optimized liquid fertilizer management increases 2-acetyl-1-pyrroline content and grain quality in aromatic rice

This study examined the effects of liquid fertilizer management on the aroma, grain quality, nutrient status, and antioxidant response of the aromatic rice varieties Yuxiangyouzhan (YXYZ) and Xiangyaxiangzhan (XYXZ) in field trials in 2019 and 2020. The application of liquid fertilizer management treatments augmented the 2-acetyl-1-pyrroline (2AP) contents. The liquid fertilizer management treatments increased the activity of antioxidant enzymes in the leaves and the contents of nutrients (nitrogen, phosphorus, and potassium) in different plant tissues, enhanced the protein content, and reduced the chalkiness in the grains. The accumulation of 2AP responded positively to the modulation of nutrient content, antioxidant response parameters, grain quality, and attributes related to the biosynthesis of 2AP. Application of 90–45–7.5 kg N ha−1 liquid fertilizer when the basal-tillering-panicle splits was the most effective fertilization treatment in improving the contents of 2-acetyl-1-pyrroline with the highest average 2AP content of 124.34 μg kg−1, which can be attributed to the regulating of grain quality, nutrient content, antioxidant response, and attributes related to 2AP biosynthesis.

Study on the Characteristics and Mechanism of Inorganic Nitrogen Nutrients Preferential Assimilation by Phaeocystis globosa

Study on the Characteristics and Mechanism of Inorganic Nitrogen Nutrients Preferential Assimilation by Phaeocystis globosa

Environmental Effects of Using Ammonium Sulfate from Animal Manure Scrubbing Technology as Fertilizer

Processed manure products have the potential to substitute chemical fertilizers and the use of these products may increase resource efficiency in the food system and decrease emissions of ammonia (NH3) and greenhouse gasses (GHG). The yields of maize and grass, as well as emissions, have been determined from a processed manure product: liquid ammonium sulfate from nitrogen stripping animal manure (AS), in comparison to a regular mineral fertilizer, calcium ammonium nitrate (CAN), in a greenhouse experiment and a field demonstration using a sandy and a clay soil. NH3 emissions were determined by comparing AS with a dairy manure as a reference. The yield of both crops, their nitrogen nutrient use efficiency (NUE), and nitrous oxide (N2O) emissions were not significantly different, while NH3 emission was lower from AS compared to the dairy manure. As a side-effect, the sulfur (S) contents of the grass in the fields fertilized with AS were much higher than in the non-fertilized control. We conclude that AS, produced here with a pH < 5.5, can be used as an alternative for CAN in Dutch dairy systems, or similar other system, if S leaching losses do not pose a problem for the environment. Meanwhile, care should be taken not to exceed S in feed above toxic levels for ruminants.

Rewetting effects on nitrogen cycling and nutrient export from coastal peatlands to the Baltic Sea

Coastal nutrient loads from point sources such as rivers are mostly well-monitored. This is not the case for diffuse nutrient inputs from coastal catchments unconnected to rivers, despite the potential for high inputs due to intensive land use. The German Baltic Sea coastline consists of numerous peatlands that have been diked and drained. However, some of the dikes have been removed in order to re-establish the hydrological connection to the Baltic Sea, restore local biodiversity, and promote natural CO2 uptake. Since these peatlands were used for agriculture, their rewetting may release accumulated nutrients, leading to nutrient export into the Baltic Sea and intensified coastal eutrophication. Data on these potential nutrient exports are mostly lacking. Therefore, this study investigated nutrient exports from two former agricultural, coastal peatlands: Drammendorfer Wiesen, rewetted in 2019, and Karrendorfer Wiesen, rewetted in 1993. Nutrients (NO3–, NO2–, NH4+, PO43–), nitrous oxide (N2O), particulate organic matter (POM, comprising POC and PON; δ13C-POC), chlorophyll-a, and nitrification rates were analyzed in surface water and porewater sampled weekly to monthly in 2019 and 2020 to compare the effects of different time scales after rewetting on nutrient cycling and potential exports. NH4+, NO2−, and PO43− concentrations were higher in the porewater than in the overlying water at both sites, while nutrient concentrations were generally higher at the recently rewetted Drammendorfer Wiesen than at the Karrendorfer Wiesen. NO3− concentrations in porewater, however, were lower than in the overlying water, indicating NO3− retention within the peat, likely due to denitrification. Nitrification rates and N2O concentrations were generally low, except for a high N2O peak immediately after rewetting. These results suggest that denitrification was the dominant process of N2O production at the study sites. Both peatlands exported nutrients to their adjacent bays of the Baltic Sea; however, N exports were 75% lower in the longer-rewetted peatland. Compared to major Baltic Sea rivers, both sites exported larger area-normalized nutrient loads. Our study highlights the need to monitor the impact of rewetting measures over time to obtain accurate estimates of nutrient exports, better assess negative effects on coastal waters, and to improve peatland management.

Effects of Sweet and Forge Sorghum Silages Compared to Maize Silage without Additional Grain Supplement on Lactation Performance and Digestibility of Lactating Dairy Cows.

This study investigated the effects of replacing maize silage (MZS) with high-sugar sorghum silage (HSS) or forage sorghum silage (FSS) without additional grain supplement in the diets of dairy cows on nutrient digestibility, milk composition, nitrogen (N) use, and rumen fermentation. Twenty-four Chinese Holstein cows (545 ± 42.8 kg; 21.41 ± 0.62 kg milk yield; 150 ± 5.6 days in milk) were randomly assigned to three dietary treatments (n = 8 cows/treatment). The cows were fed ad libitum total mixed rations containing (dry matter basis) either 40% MZS (MZS-based diet), 40% HSS (HSS-based diet), or 40% FSS (FSS-based diet). The study lasted for 42 days, with 14 days devoted to adaptation, 21 days to daily feed intake and milk production, and 7 days to the sampling of feed, refusals, feces, urine, and rumen fluid. Milk production was measured twice daily, and digestibility was estimated using the method of acid-insoluble ash. The data were analyzed using a one-way ANOVA in SPSS 22.0 according to a completely randomized design. Dietary treatments were used as fixed effects and cows as random effects. The results indicate that MZS and HSS had greater crude protein but less neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), and a lower pH than FSS (p ≤ 0.04). High starch contents in MZS and water-soluble carbohydrate (WSC) contents in HSS were observed (p < 0.01). While the highest starch intake was observed for the MZS-based diet, the highest WSC intake was noted for the HSS-based diet, and the highest NDF, ADF, ADL intake was observed for the FSS-based diet (p ≤ 0.05). The diets, including MZS and HSS, had greater digestibility than that of FSS (p ≤ 0.03). Feeding MZS- and HSS-based diets increased the yield, fat, and protein content of the milk, as well as feed conversion efficiency (p ≤ 0.03). However, feeding the MZS- and HSS-based diets decreased the contents of milk urea N, urinary urea N, and urinary N excretion more than the FSS-based diet (p ≤ 0.05). The N use efficiency tended to increase relative to diets containing MZS and HSS compared with FSS (p = 0.06 and p = 0.09). Ruminal ammonia-N and pH were lower, but total volatile fatty acids, acetate, and propionate were higher in cows fed the HSS- and MZS-based diets compared to those fed the FSS-based diet (p ≤ 0.03). It appears as though replacing MZS with HSS in the diet of cows without additional grain supplements has no negative influence on feed intake, milk yield, N utilization, or ruminal fermentation.

Nitrogen Removal Performance and Microbial Community Structure of IMTA Ponds (Apostistius japonicus-Penaeus japonicus-Ulva)

Denitrification and anaerobic ammonium oxidation (anammox) are key processes for nitrogen removal in aquaculture, reducing the accumulated nitrogen nutrients to nitrogen gas or nitrous oxide gas. Complete removal of nitrogen from aquaculture systems is an important measure to solve environmental pollution. In order to evaluate the nitrogen removal potential of marine aquaculture ponds, this study investigated the denitrification and anammox rates, the flux of nitrous oxide (N2O) at the water–air interface, the sediment microbial community structure, and the gene expression associated with the nitrogen removal process in integrated multi-trophic aquaculture (IMTA) ponds (Apostistius japonicus-Penaeus japonicus-Ulva) with different culture periods. The results showed that the denitrification and anammox rates in sediments increased with the increase of cultivation periods and depth, and there was no significant difference in nitrous oxide gas flux at the water–air interface between different cultivation periods (p > 0.05). At the genus and phylum levels, the abundance of microorganisms related to nitrogen removal reactions in sediments changed significantly with the increase of cultivation period and depth, and was most significantly affected by the concentration of particulate organic nitrogen (PON) in sediments. The expression of denitrification gene (narG, nirS, nosZ) in surface sediments was significantly higher than that in deep sediments (p < 0.05), and was negatively correlated with denitrification rate. All samples had a certain anammox capacity, but no known anammox bacteria were found in the microbial diversity detection, and the expression of gene (hzsB) related to the anammox process was extremely low, which may indicate the existence of an unknown anammox bacterium. The data of this study showed that the IMTA culture pond had a certain potential for nitrogen removal, and whether it could make a contribution to reducing the pollution of culture wastewater still needed additional practice and evaluation, and also provided a theoretical basis for the nitrogen removal research of coastal mariculture ponds.Graphical

The culture of Chlorella with livestock wastewater and the application of its oligosaccharides in promoting rice seed germination under high salinity conditions

Algal oligosaccharides, derived from polysaccharides in algal biomass, exhibit bioactive properties that enhance plant antioxidant enzyme activity and free radical scavenging. Currently, algal oligosaccharides are mainly produced from large algae, while studies on preparing algal oligosaccharides from microalgae are relatively insufficient. This study focuses on utilizing Chlorella cultivated under controlled conditions using diluted livestock wastewater to produce algal oligosaccharides and investigates their impact on rice seed germination under salt stress. Results show that culturing Chlorella with diluted livestock wastewater not only stimulated algal growth but also efficiently removed nitrogen, phosphorus, and other nutrients. Algal oligosaccharides demonstrated significant improvements in rice seed germination, vigor indices, biomass accumulation, and nitrogen absorption under salt stress. Physiological indicators revealed elevated osmotic adjustment substances, increased chlorophyll content, and alleviated oxidative damage in rice seedlings treated with algal oligosaccharides. The study introduces an innovative method of using livestock wastewater for algal oligosaccharides production, emphasizing its dual benefits including efficient resource utilization and significant cost reduction. The findings also support the theoretical application of Chlorella-derived algal oligosaccharides in enhancing rice cultivation under salt stress.

Genome-resolved metagenomics reveals the effect of nutrient availability on bacterial genomic properties across 44 European freshwater lakes.

Understanding intricate microbial interactions in the environment is crucial. This is especially true for the relationships between nutrients and bacteria, as phosphorus, nitrogen and organic carbon availability are known to influence bacterial population dynamics. It has been suggested that low nutrient conditions prompt the evolutionary process of genome streamlining. This process helps conserve scarce nutrients and allows for proliferation. Genome streamlining is associated with genomic properties such as %GC content, genes encoding sigma factors, percent coding regions, gene redundancy, and functional shifts in processes like cell motility and ATP binding cassette transporters, among others. The current study aims to unveil the impact of nutrition on the genome size, %GC content, and functional properties of pelagic freshwater bacteria. We do this at finer taxonomic resolutions for many metagenomically characterized communities. Our study confirms the interplay of trophic level and genomic properties. It also highlights that different nutrient types, particularly phosphorus and nitrogen, impact these properties differently. We observed a covariation of functional traits with genome size. Larger genomes exhibit enriched pathways for motility, environmental interaction, and regulatory genes. ABC transporter genes reflect the availability of nutrients in the environment, with small genomes presumably relying more on metabolites from other organisms. We also discuss the distinct strategies different phyla adopt to adapt to oligotrophic environments. The findings contribute to our understanding of genomic adaptations within complex microbial communities.

Contribution of emissions from the oil sands activities in Alberta, Canada to atmospheric concentration and deposition of nitrogen and sulfur species at a downwind site

Oil sands activities in the Athabasca Oil Sands Region in Alberta, Canada, are large sources of atmospheric NOx and SO2. This study investigated the impact of oil sands emissions on the atmospheric deposition of nitrogen and sulfur species at a downwind site, about 350 km from the oil sands facilities. Measurement data are from the Canadian Air and Precipitation Monitoring Network (CAPMoN) from 2015 to 2019, including ambient concentrations of HNO3, pNO3-, NO2, pNH4+, NH3, SO2, pSO42− and base cations, as well as concentrations of NO3−, SO42−, NH4+, and base cations in precipitation. Sector analysis of air mass back trajectories was conducted to distinguish measurements with different air mass origins. Median atmospheric concentrations and dry deposition fluxes of HNO3, pNO3-, NO2, pNH4+, pSO42−, and SO2 on days when the air masses came from the oil sands sector were significantly greater than those with the “Clean” sector by 34–67%, whereas the difference in NH3 concentration was not significant. Contributions of the oil sands emissions to dry deposition fluxes of these species ranged from 3.8 to 13.1%. The precipitation-weighted mean concentrations of NO3−, SO42−, and NH4+ in samples with the oil sands sector were 76 %, 65 % and 81 % greater than those with the “Clean” sector, respectively. Contributions of the oil sands emissions to wet deposition of NO3−, SO42−, and NH4+ were 12.5 ± 8.9 %, 8.7 ± 4.4 %, and 6.0 ± 3.3 %, respectively. The annual total deposition of nitrogen and sulfur were 1.9 kg-N ha−1 and 0.74 kg-S ha−1, respectively, of which 8.0 ± 3.5 % and 8.7 ± 3.6 % were from oil sands emissions. The total deposition of sulfur and nitrogen did not exceed the critical loads (CL) of acidity, but nitrogen deposition exceeded the CLs of nutrient nitrogen in the region.

Evaluation of Microbe-Enriched Organic Fertilizer on Three Hybrid Corn (Zea Mays L.) Varieties in Swamp Land

Lowland areas are characterized by poor soil fertility and low nutrient content, making them suboptimal for agriculture. However, these lands have the potential to be developed for agricultural purposes, particularly for cultivating hybrid corn plants. To enhance production, organic fertilizers enriched with Azospirilium microbes and Phosphate Solubilizing Bacteria (BPF) are utilized, along with the planting of superior varieties that are tolerant to lowland conditions. Azospirilium microbes play a crucial role in providing nitrogen (N) nutrients through the nitrogenase enzyme, while BPF contributes phosphorus (P) and potassium (K) nutrients through the phosphatase enzyme. This combination of nutrients is essential for hybrid corn plants to thrive and produce effectively. The research conducted in Pulau Semambu Village, North Inderalaya District, Ogan Ilir Regency, from January to April 2023, employed a field experiment method using a Factorial Randomized Block Design with 9 treatment combinations repeated 3 times. The study involved three varieties (Pioneer 21, Bisi 816, Pertiwi) and three organic fertilizer dosages (100 kg/ha, 300 kg/ha, 500 kg/ha). The highest yield was achieved by applying 300 kg/ha of microbe-enriched organic fertilizer in combination with the Bisi 816 variety, resulting in a yield of 4.24 kg/plot or 5.65 tonnes/ha. This result represented a 60% increase compared to the Pioneer 21 variety treated with 100 kg/ha of microbial-enriched organic fertilizer.

Improving the quality of organic fertilizer by utilizing local microorganisms (LMO) of cassava tapai

Local Micro Organism Solution (LMO Solution) is a fermentation solution made from various locally available resources, both plants and animals. The LMO solution contains micro and macronutrients and bacteria that have the potential to decompose organic matter in the soil, stimulate plant growth, and act as a pest and plant disease control agent. It is easy to obtain and makes it possible to increase farmers’ desire to process agricultural waste. This research aims to determine the quality of organic fertilizer from livestock manure by utilizing local microorganisms (LMO) in cassava. This research was carried out from March 2023 to December 2023. The research was carried out at the Soil Laboratory of Hasanuddin University and the Greenhouse of the Faculty of Agriculture and Forestry, West Sulawesi University. The experimental design used in this planting test was a Completely Randomized Design (CRD), consisting of four LMO dose treatments, with each treatment carried out three times. The results of the research showed that the planting media provided by LMO tapai cassava had a significant effect on increasing the availability of the nutrients Nitrogen (N) and Phosphorus (P). The treatment regimen involving a dose of 240 ml (M3) showed the highest average values ​​for nutrient content, specifically 0.25% for Nitrogen (N) and 13.75 ppm for Phosphorus (P2O5). Providing cassava tapai LMO in the planting medium had a significant effect on the average height of spinach plants at the observation time of 10 day after planting (DAT) and the average leaf weight. The M3 treatment showed the highest average value of plant height at 10 DAT of 7.17 cm and leaf weight of 0.73 g.

Variation in Nitrogen Utilization and Nutrient Composition across Various Organs under Different Strip Logging Management Models in Moso Bamboo (Phyllostachys edulis) Forest.

The rapid restoration and renewal of the moso bamboo logging zone after strip logging has emerged as a key research area, particularly regarding whether nutrient accumulation and utilization in reserve zones can aid in the restoration and regeneration of the logging zone. In this study, a dynamic 15N isotope tracking experiment was conducted by injecting labeled urea fertilizer into bamboo culms. Logging zones and reserve zones of 6 m, 8 m, and 10 m widths were established. The conventional selective logging treatment served as a control (Con). Measurements were taken in May and October to assess the differences in nitrogen accumulation ability, utilization rates, and nutrient content across different organs in bamboo forests at different growth stages and under different treatments. Principal component analysis was conducted to evaluate and determine the importance of each indicator and strip logging treatment comprehensively. The results showed that various bamboo organs exhibited higher nitrogen accumulation and utilization rates during the peak growth period compared to the late growth period. Leaves had the highest nitrogen accumulation and utilization rates than the other organs. The average C content in various bamboo organs under different logging treatments exhibited subtle differences, irrespective of variation in logging width treatments. Bamboo culm exhibited the highest carbon accumulation. The C content in various bamboo organs was higher during the peak growth period than in the late growth period. The nitrogen content peaked in the leaves during the two growth stages and was significantly higher compared to the other organs. Most bamboo organs in the logging zones exhibited relatively higher nitrogen content than in the reserve zone and Con group. The P content was highest in bamboo leaves compared with other organs across the different strip logging treatments. Principal component analysis revealed relatively high absolute values of the coefficients for the C content, bamboo stump C content, and culm Ndff%. Log8 and Res10 zones had the highest comprehensive evaluation scores, indicating that Log8 and Res10 had the best effect on the promotion of nitrogen utilization and nutrient accumulation in various organs of moso bamboo.

Effects of organic amendments on yield determining properties and macronutrient content of maize

The use of organic fertilization is declining in Hungary due to the sharp fall of livestock stand since the middle of the 1980s. Most farmers are forced to use solely chemical crop enhancers. A bifactorial small plot experiment was carried out between 10 May 2023 and 19 October 2023 in Keszthely, in order to examine the effects of farmyard manure (M), green manure (GM) and stem residues (SR) on the nutrient uptake and nitrogen utilization efficiencies of maize at equidistantly increasing (0–70–140–210–280 kg N ha–1) nitrogen doses. The relationship between some vegetative traits (dry biomass weight, Leaf Area Index (LAI)) and yield, furthermore leaf relative water content (RWC) was also examined. According to the results, organic fertilizer substitution significantly increased the N content both in whole plant and grain samples of NPK+M and NPK+GM+SR treatments, compared to the chemically fertilized control (NPK). In case of P and K only slight differences were observed. Whole plant K contents of NPK+M were significantly higher than in the other treatments (P = 0.045; P = 0,005), furthermore P contents in grain samples were significantly higher in NPK+M (P = 0.004) and NPK+GM+SR (P = 0.05) than in control. Harvest index (HI [%]) of NPK+M and NPK+GM+SR were 1.06 and 1.05 times higher than in NPK. Depending on the treatment, P0023 maize hybrid absorbed 58.7–74.64% of total N uptake in the grain (HIN%), and the utilization of 1 kg N fertilizer for the extra yield above the yield of the individual control was 0.39–1.38 kg (AREN). Significant positive correlations were observed between dry biomass weight and yield (NPK: r = 0.937, P = 0.019; NPK+M: r = 0.971, P = 0.006; NPK+GM+SR: r = 0.88, P = 0.049), furthermore LAI and yield (NPK: r = 0.9, P = 0.037; NPK+M: r = 0.983, P = 0.003; NPK+GM+SR: r = 0.784, P = 0.117). Highest RWC values – which may be related to better soil aggregate stability – were measured in NPK+GM+SR treatment, therefore there may be a great potential in this treatment among drought conditions. The effect of organic amendments is particularly noticeable with smaller nitrogen doses so they should be used to reduce inorganic fertilizer application and the resulting environmental risks.

Optimizing Nitrogen Nutrient Management for the Sustainable Enhancement of Secondary Metabolites and Yield in Onion Cultivation

This study investigates the impact of nitrogen (N), sulfur (S), and iron (Fe) fertilization on secondary metabolites, particularly quercetin and its forms, in onion bulbs (Allium cepa L.). Field experiments over two years examined four onion varieties with red, yellow, and white colors of bulbs: Kamal, Robin, Pueblo, and Mundo. The parameters investigated included the yield, dry matter content, and average onion weight. The phenolic and flavonoid contents were also analyzed. The free quercetin, bound quercetin, and total quercetin contents were determined using the HPLC method. The results demonstrated notable increases in yield following the application of nitrogen (NH4+) and sulfur (SO42−) fertilizers. Incorporating iron (Fe2+) alongside these fertilizers did not yield a significant impact compared to N+S variant. The phenolic and flavonoid content varied with fertilization, while the quercetin content did not yield statistically significant results. Overall, the study highlights the complex relationship between fertilization practices and secondary metabolite production in onions, emphasizing the need for sustainable intensification in modern agriculture.

Diagnostic study of nitrogen nutrition in cotton based on unmanned aerial vehicle RGB images

Nitrogen fertilizer levels significantly affect crop growth and development, necessitating precision management. Most studies focus on nitrogen nutrient estimation using vegetation indices and textural features, overlooking the diagnostic potential of color features. Hence, we investigated cotton nitrogen nutrition status using unmanned aerial vehicle (UAV) image features and the nitrogen nutrient index (NNI). Random frog algorithm - and random forest-screened image feature sets significantly correlated with the NNI, which were substituted into four machine learning algorithms for NNI estimation modeling. The composite scores (F) of optimal image feature sets were calculated using the coefficient of variation method for comprehensive cotton nitrogen nutrient diagnosis. Validation of the model for determining the critical nitrogen concentration in cotton yielded a coefficient of determination R2 = 0.89, root mean square error RMSE = 0.50 g (100 g)-1, and mean absolute error MAE = 0.44, demonstrating improved performance. Additionally, our novel NNI estimation model constructed based on the optimal image feature sets exhibited R2c = 0.97, RMSEc = 0.02, MAEc = 0.02, R2v = 0.85, RMSEv = 0.05, and MAEv = 0.04. Polynomial fitting of the composite index with NNI indicated that the model was reliable and yielded the following diagnostic criterion: 0.48 &lt; F2 &lt; 0.67 indicated nitrogen overapplication, whereas F2 &lt; 0.48 or F2 &gt; 0.67 indicated nitrogen deficiency. This study demonstrates the superior effectiveness of using UAV RGB image feature sets for NNI estimation and the quick, accurate diagnosis of cotton nitrogen levels, which will help guide nitrogen fertilizer application.

Nutrient optimization in bioleaching: are we overdosing?

The general trend in biomining (i.e., bioleaching and biooxidation) is the use of media with high concentrations of the nutrients (nitrogen as ammonium, phosphorous as phosphate, and K), which are considered to be essential for microbial growth. The depletion of any of the nutrients would affect negatively the bioleaching (and biooxidation) capacity of the microorganisms, so the formulation of the different media ensures that there is a surplus of nutrients. However, some of these nutrients (e.g., phosphate, K) may be already present in the ore and are made available to the microorganisms when the ore is exposed to the low-pH media used during bioleaching. The effect of phosphate addition (109 mg/L) and depletion on the bioleaching of low-grade sulfidic ore alongside the determination of ammonium (i.e., 25 mg/L, 50 mg/L, 109 mg/L, 409 mg/L, and 874 g/L) requirements were studied. The results of the experiments presented showed that the addition of phosphate did not have any effect on the bioleaching of the low-grade sulfidic ore while the addition of ammonium was necessary to obtain higher redox potentials (>650 mV vs. Ag/AgCl) and higher metal (Co, Cu, Ni, and Zn) dissolutions. Temperature was the factor that shaped the microbial communities, at 30°C, the microbial community at the end of all the experiments was dominated by Acidithiobacillus sp. as well as at 42°C, except when nutrients were not added and Sulfobacillus sp. was the dominant microorganism. At 55°C, DNA recovery was unsuccessful, and at 60°C, the microbial communities were dominated by Sulfolobus sp. In conclusion, the amount of nutrients in bioleaching could be reduced significantly to achieve the redox potentials and metal dissolution desired in bioleaching without affecting the microbial communities and bioleaching efficiencies.

Temporal variations of biological nitrogen fixation and diazotrophic communities associated with artificial seaweed farms

Diazotrophic communities contribute inorganic nitrogen for the primary productivity of the marine environment by biological nitrogen fixation (BNF). They play a vital role in the biogeochemical cycle of nitrogen in the marine ecological environment. However, there is still an incomplete understanding of BNF and diazotrophs in artificial seaweed farms. Therefore, this study comprehensively investigated the temporal variations of BNF associated with Gracilariopsis lemaneiformis, as well as the diazotrophic communities associated with macroalgae and its surrounding seawater. Our results revealed that a total of 13 strains belonging to Proteobacteria and Bacteroidetes were identified as N2-fixing bacteria using azotobacter selective solid medium and nifH gene cloning. Subsequently, BNF and diazotrophic communities were characterized using the acetylene reduction method and high-throughput sequencing of the nifH gene, respectively. The results showed that nitrogenase activity and nifH gene abundance of epiphytic bacteria on G. lemaneiformis varied significantly among four different cultivation periods, i.e., Cultivation Jan. (CJ), Cultivation Feb. (CF), Cultivation Mar. (CM), Cultivation Apr. (CA). Among them, the nitrogenase activity and nifH gene abundance of epiphytic bacteria on G. lemaneiformis in CM were significantly higher than those in CJ, CF, and CA, indicating that the BNF of eiphytic bacteria on G. lemaneiformis was markedly enhanced. Combined with the data on environmental factors, it was found that the low concentration of nitrogen and phosphorus in CM might considerably boost the BNF of epiphytic bacteria in G. lemaneiformis. The sequencing results of the nifH gene showed that the α-diversity of diazotrophic communities associated with G. lemaneiformis and seawater in CM was higher than that in other cultivation periods. In addition, the diazotrophic communities on G. lemaneiformis were significantly different in CJ, CF, CM, and CA, and they were significantly diverse from diazotrophic communities in seawater. LEfSe analysis indicated that Rhodobacterales, Hyphomonadaceae, Robiginitomaculum, and Robiginitomaculum antarcticum within α-proteobacteria played a remarkable role in BNF in response to nitrogen nutrient deficiency. Taken together, these results provide a unique insight into the interaction between macroalgae and its epiphytic bacteria and lay a foundation for further research on the mechanism of action of nitrogen-cycling microorganisms associated with macroalgae.

Preliminary tests on carbon and nitrogen emissions and nutrients availability upon application of algal-bacterial granules to arid and low fertility soil

To remediate arid and low fertility soil and explore the feasibility of controlling its carbon (C) and nitrogen (N) emissions, algal-bacterial aerobic granular sludge (AGS) was applied as soil additives and compared with bacterial AGS and cyanobacteria during 14 days’ incubation. Results show that algal-bacterial AGS as additives possesses a higher potential in terms of fertility recovery and soil physicochemical properties conservation. The additives may change the soil characteristics by decreasing soil pH (within 0.6) and water content (0.8–2.5 %) with increased electrical conductivity during the 14 days’ incubation. As for soil fertility, due to the high available phosphorus (P) content in algal-bacterial AGS, the soil available P content was significantly increased from 50 % to 170 % after incubation under different application rates or gaseous environments. N was also accumulated in the soil matrix with increased inorganic forms and less or acceptable N emission. The contents of soluble organic substances and extracellular polymeric substances (EPS) were significantly increased after incubation. Under ambient air and moderately elevated CO2 like 10 % conditions, carbon mineralization in the soil samples was lower than 15 % at low additives dosages; while under an elevated CO2 content (25 %) condition, a higher additives dosage may cause a rapid CO2 accumulation within 2 days with a substantial O2 consumption, leading to an anaerobic/anoxic environment corresponding to a higher C mineralization and/or N loss.

Rock Phosphate and Biochar Effects on Greenhouse Gas Emissions and Soil Fertility in Southern Alberta Potato Field

The application of biochar soil amendment and rock phosphate fertilizer to the soil could lead to achieving net zero emissions and food security; however, the effectiveness of using biochar and rock phosphate in southern Alberta brown chernozemic soil is not yet assessed. In the first trial of this study, varying levels of urea (N), with varying levels of biochar (B) were applied. The same level of rock phosphate (RP) and triple super phosphate (TSP) were applied to compare efficiency of the two fertilizers. The second trial involved applying the same nutrients, but with higher levels than the first trial. The results indicated that the fertilizer application rates did not affect the growth and yield of potatoes because of the application rates of the fertilizer and fertility status of the soil, whereas in the second trial, TSP and RP treatments had the same growth and yield. Furthermore, the high application rate of nitrogen fertilizer and RP with or without biochar in the potato plot emitted high nitrous oxide gas emissions while the low application rate of nitrogen fertilizer and RP kept the carbon dioxide in the soil. Nevertheless, in the second experiment, the application of biochar and rock phosphate reduced nitrous oxide and carbon dioxide emissions. We observed high residual nitrogen and manganese nutrients after harvest in the plot treated to rock phosphate and biochar. Therefore, rock phosphate and biochar have the potential to increase food production and mitigate climate change.