N2-fixing Bacteria Research Articles

Winter Cover Cropping in Sustainable Production Systems: Effects on Soybean and Synergistic Implications for Rhizosphere Microorganisms.

The aim of this study was to evaluate the effects of winter cover crops (CCs) on soybean agronomic performance and their implications for different physiological groups of rhizosphere microorganisms in two sustainable production systems. The production techniques for rye, peas, and oats are well known, but their suitability as CCs for soybean (organic and low-input) production needs to be examined. After two years of trials, soybean yields among the two tested winter CCs (peas and oats (P + O) and rye (R)) were statistically significant only for P + O. The soybean yield in succession to P + O as winter CCs was 3.0 t ha-1, whereas in succession to R, it was 2.7 t ha-1, and in the control plot, it was 2.6 t ha-1. The average soybean grain protein content was in the range of 40 to 41% dry matter (DM), while the oil content ranged from 20 to 22% DM. Protein and oil content primarily depends on the selected soybean variety and it is confirmed through this study that, in the studied system, we can obtain adequate grain nutritional quality. The results indicate an increase in the abundance of total bacteria, ammonifiers, and free N2-fixing bacteria in the rhizosphere, depending on the selected CCs, and differences between the tested production systems. According to this study, winter cover crops (CCs), including peas and oats (P + O) and rye (R), can be included in crop rotation for soybean. CCs can be the answer to agro-biodiversity empowerment in less diverse soybean cropping systems, along with other benefits that CCs can provide at the level of crop rotation. In addition, in almost all aspects of the study, organic production was ahead of low input. Low input is an adequate production system if there are no opportunities for organic certification and for producers who are aware of the advantages of sustainable systems, and it can also represent a transitional path towards regenerative agriculture or organic production.

Microbes in Agriculture: Prospects and Constraints to Their Wider Adoption and Utilization in Nutrient-Poor Environments

Microbes such as bacteria and fungi play important roles in nutrient cycling in soils, often leading to the bioavailability of metabolically important mineral elements such as nitrogen (N), phosphorus (P), iron (Fe), and zinc (Zn). Examples of microbes with beneficial traits for plant growth promotion include mycorrhizal fungi, associative diazotrophs, and the N2-fixing rhizobia belonging to the α, β and γ class of Proteobacteria. Mycorrhizal fungi generally contribute to increasing the surface area of soil-root interface for optimum nutrient uptake by plants. However, when transformed into bacteroids inside root nodules, rhizobia also convert N2 gas in air into ammonia for use by the bacteria and their host plant. Thus, nodulated legumes can meet a high proportion of their N requirements from N2 fixation. The percentage of legume N derived from atmospheric N2 fixation varies with crop species and genotype, with reported values ranging from 50–97%, 24–67%, 66–86% 27–92%, 50–92%, and 40–75% for soybean (Gycine max), groundnut (Arachis hypogea), mung bean (Vigna radiata), pigeon pea (Cajanus cajan), cowpea (Vigna unguiculata), and Kersting’s groundnut (Macrotyloma geocarpum), respectively. This suggests that N2-fixing legumes require little or no N fertilizer for growth and grain yield when grown under field conditions. Even cereals and other species obtain a substantial proportion of their N nutrition from associative and endophytic N2-fixing bacteria. For example, about 12–33% of maize N requirement can be obtained from their association with Pseudomonas, Hebaspirillum, Azospirillum, and Brevundioronas, while cucumber can obtain 12.9–20.9% from its interaction with Paenebacillus beijingensis BJ-18. Exploiting the plant growth-promoting traits of soil microbes for increased crop productivity without any negative impact on the environment is the basis of green agriculture which is done through the use of biofertilizers. Either alone or in combination with other synergistic rhizobacteria, rhizobia and arbuscular mycorrhizal (AM) fungi have been widely used in agriculture, often increasing crop yields but with occasional failures due to the use of poor-quality inoculants, and wrong application techniques. This review explores the literature regarding the plant growth-promoting traits of soil microbes, and also highlights the bottle-necks in tapping this potential for sustainable agriculture.

Unveiling the hidden world: How arbuscular mycorrhizal fungi and its regulated core fungi modify the composition and metabolism of soybean rhizosphere microbiome

BackgroundThe symbiosis between arbuscular mycorrhizal fungi (AMF) and plants often stimulates plant growth, increases agricultural yield, reduces costs, thereby providing significant economic benefits. AMF can also benefit plants through affecting the rhizosphere microbial community, but the underlying mechanisms remain unclear. Using Rhizophagus intraradices as a model AMF species, we assessed how AMF influences the bacterial composition and functional diversity through 16 S rRNA gene sequencing and non-targeted metabolomics analysis in the rhizosphere of aluminum-sensitive soybean that were inoculated with pathogenic fungus Nigrospora oryzae and phosphorus-solubilizing fungus Talaromyces verruculosus in an acidic soil.ResultsThe inoculation of R. intraradices, N. oryzae and T. verruculosus didn’t have a significant influence on the levels of soil C, N, and P, or various plant characteristics such as seed weight, crude fat and protein content. However, their inoculation affected the structure, function and nutrient dynamics of the resident bacterial community. The co-inoculation of T. verruculosus and R. intraradices increased the relative abundance of Pseudomonas psychrotolerans, which was capable of N-fixing and was related to cry-for-help theory (plants signal for beneficial microbes when under stress), within the rhizosphere. R. intraradices increased the expression of metabolic pathways associated with the synthesis of unsaturated fatty acids, which was known to enhance plant resistance under adverse environmental conditions. The inoculation of N. oryzae stimulated the stress response inside the soil environment by enriching the polyene macrolide antifungal antibiotic-producing bacterial genus Streptomyces in the root endosphere and upregulating two antibacterial activity metabolic pathways associated with steroid biosynthesis pathways in the rhizosphere. Although inoculation of pathogenic fungus N. oryzae enriched Bradyrhizobium and increased soil urease activity, it had no significant effects on biomass and N content of soybean. Lastly, the host niches exhibited differences in the composition of the bacterial community, with most N-fixing bacteria accumulating in the endosphere and Rhizobium vallis only detected in the endosphere.ConclusionsOur findings demonstrate that intricate interactions between AMF, associated core fungi, and the soybean root-associated ecological niches co-mediate the regulation of soybean growth, the dynamics of rhizosphere soil nutrients, and the composition, function, and metabolisms of the root-associated microbiome in an acidic soil.

Growth, Photosynthesis and Yield Responses of Common Wheat to Foliar Application of Methylobacterium symbioticum under Decreasing Chemical Nitrogen Fertilization

Current agriculture intensifies crop cultivation to meet food demand, leading to unsustainable use of chemical fertilizers. This study investigates a few physiological and agronomic responses of common wheat following the inoculation with plant growth-promoting bacteria to reduce nitrogen inputs. A field trial was conducted in 2022–2023, in Legnago (Verona, Italy) on Triticum aestivum var. LG-Auriga comparing full (180 kg ha−1) and reduced (130 kg ha−1) N doses, both with and without foliar application at end tillering of the N-fixing bacterium Methylobacterium symbioticum. Biofertilization did not improve shoot growth, while it seldom increased the root length density in the arable layer. It delayed leaf senescence, prolonged photosynthetic activity, and amplified stomatal conductance and PSII efficiency under the reduced N dose. Appreciable ACC-deaminase activity of such bacterium disclosed augmented nitrogen retrieval and reduced ethylene production, explaining the ameliorated stay-green. Yield and test weight were unaffected by biofertilization, while both glutenin-to-gliadin and HMW-to-LMW ratios increased together with dough tenacity. It is concluded that Methylobacterium symbioticum can amplify nitrogen metabolism at a reduced nitrogen dose, offering a viable approach to reduce chemical fertilization under suboptimal growing conditions for achieving a more sustainable agriculture. Further research over multiple growing seasons and soil types is necessary to corroborate these preliminary observations.

Co-composting of tail vegetable with flue-cured tobacco leaves: analysis of nitrogen transformation and estimation as a seed germination agent for halophyte.

Resource utilization of tail vegetables has raised increasing concerns in the modern agriculture. However, the effect and related mechanisms of flue-cured tobacco leaves on the product quality, phytotoxicity and bacterially-mediated nitrogen (N) transformation process of tail vegetable composting were poorly understood. Amendments of high-dosed (5% and 10% w/w) tobacco leaves into the compost accelerated the heating process, prolonged the time of thermophilic stage, increased the peak temperature, thereby improving maturity and shortening composting duration. The tobacco leaf amendments at the 10% (w/w) increased the N conservation (TN and NH4-N content) of compost, due to the supply of N-containing nutrient and promotion of organic matter degradation by tobacco leaves. Besides, tobacco leaf amendments promoted the seed germination and root development of wild soybean, exhibiting the feasibility of composting product for promoting the growth of salt-tolerant plants, but no dose-dependent effect was found for tobacco leaf amendments. Addition of high dosed (5% and 10% w/w) tobacco leaves shifted the bacterial community towards lignocellulosic and N-fixing bacteria, contributing to increasing the compost maturity and N retention. PICRUSt 2 functional prediction revealed that N-related bacterial metabolism (i.e., hydroxylamine oxidation and denitrifying process) was enhanced in the tobacco leaf treatments, which contributed to N retention and elevated nutrient quality of composting. To the best knowledge, this was the first study to explore the effect of tobacco waste additives on the nutrient transformation and halophyte growth promotion of organic waste composting. These findings will deepen the understanding of microbially-mediated N transformation and composting processes involving flue-cured tobacco leaves.

Metal ions steer the duality in microbial community recovery from nitrogen enrichment by shaping functional groups.

Atmospheric nitrogen (N) deposition has been substantially reduced due to declines in the reactive N emission in major regions of the world. Nevertheless, the impact of reduced N deposition on soil microbial communities and the mechanisms by which they are regulated remain largely unknown. Here, we examined the effects of N addition and cessation of N addition on plant and soil microbial communities through a 17-year field experiment in a temperate grassland. We found that extreme N input did not irreversibly disrupt the ecosystem, but ceasing high levels of N addition led to greater resilience in bacterial and fungal communities. Fungi exhibited diminished resilience compared to bacteria due to their heightened reliance on changes in plant communities. Neither bacterial nor fungal diversity fully recovered to their original states. Their sensitivity and resilience were mainly steered by toxic metal ions and soil pH differentially regulating on functional taxa. Specifically, beneficial symbiotic microbes such as N-fixing bacteria and arbuscular mycorrhizal fungi experienced detrimental effects from toxic metal ions and lower pH, hindering their recovery. The bacterial functional groups involved in carbon decomposition, and ericoid mycorrhizal and saprotrophic fungi were positively influenced by soil metals, and demonstrated gradual recovery. These findings could advance our mechanistic understanding of microbial community dynamics under ongoing global changes, thereby informing management strategies to mitigate the adverse effects of N enrichment on soil function.

Isolation and Bioassay of N-fixing Bacteria from Mercury-Contaminated Tailing and Soil of Artisanal and Small-Scale Gold Mining

This study aims to isolate Nitrogen-fixing bacteria from tailing and heavy metal (HM) polluted soils and examine their effectiveness as a plant growth-promoting rhizobacteria (PGPR) to increase foxtail millet plant growth. We analyzed artisanal and small-scale gold mining (ASGM) sites in Pongkor Village, West Java, Indonesia, and identified nine areas with significant contamination of Mercury (Hg), Lead (Pb), Cadmium (Cd), Chromium (Cr), and Arsenic (As). We isolated sixteen strains of nitrogen-fixing bacteria different carbon sources. We identified three strains (3.2.h, 4.2.b, and 9.2.a) that the most robust nitrogenase activity and indole acetic acid (IAA) production. They were identified based on their molecular characteristics (16S rRNA) as Ralstonia pickettii strain LMQOTU12, Azotobacter chroococcum subsp. isscasi strain P205, and Azotobacter chroococcum subsp. isscasi strain P205. The three isolates were inoculated to foxtail millet plant grown under Andosol slightly acidic (pH 5.8), moderate nitrogen content (0.26%). The three strains isolates demonstrated significant enhancement to foxtail millet plants’ growth. Improvements (compared to control) in shoot dry weight: 8% (3.2.h), 32% (4.2.b), 88% (9.2.a); longest root length: 88.71% (3.2.h), 108.90% (4.2.b), 140.16%; root dry weight: 350% (3.2.h), 450% (4.2.b), 250% (9.2.a); and root-shoot ratio 312% (3.2.h), 312% (4.2.b), 75% (9.2.a). This study demonstrates that the three strains are potential PGPRs for increasing plant growth of foxtail millet.

Nitrogen-fixing bacteria boost floral attractiveness in a tropical legume species during nutrient limitation.

Legumes establish mutualistic interactions with pollinators and nitrogen (N)-fixing bacteria that are critical for plant reproduction and ecosystem functioning. However, we know little about how N-fixing bacteria and soil nutrient availability affect plant attractiveness to pollinators. In a two-factorial greenhouse experiment to assess the impact of N-fixing bacteria and soil types on floral traits and attractiveness to pollinators in Chamaecrista latistipula (Fabaceae), plants were inoculated with N-fixing bacteria (NF+) or not (NF-) and grown in N-rich organic soil (+N organic soil) or N-poor sand soil (-N sand soil). We counted buds and flowers and measured plant size during the experiment. We also measured leaf, petal, and anther reflectance with a spectrophotometer and analyzed reflectance curves. Using the bee hexagon model, we estimated chromatic contrasts, a crucial visual cues for attracting bees that are nearby and more distant. NF+ plants in -N sand soil had a high floral display and color contrasts. On the other hand, NF- plants and/or plants in +N organic soil had severely reduced floral display and color contrasts, decreasing floral attractiveness to bee pollinators. Our findings indicate that the N-fixing bacteria positively impact pollination, particularly when nutrients are limited. This study provides insights into the dynamics of plant-pollinator interactions and underscores the significant influence of root symbionts on key floral traits within tropical ecosystems. These results contribute to understanding the mechanisms governing mutualisms and their consequences for plant fitness and ecological dynamics.

Effects of Azotobacter spp., mycorrhizal fungi and shade treatments on plant growth and chlorophyll content in boxwoods plants

In this study, two important commercial species, Buxus microphilla and B. herlandii, were evaluated. People do not want polluting and toxic fertilizers used to cultivate the plants they use for nutrition, and they do not want the plants they use as ornamental plants. The study investigated the effects of mycorrhizal and bacterial applications on plant growth and chlorophyll content. As a result of the study, it was concluded that bacterial applications on the development of boxwoods are more effective than mycorrhizal applications. Shading further increased the effect of the applications. In B. microphilla, in a 70% shade, plant height increased by 18.5% with mycorrhizal application, and plant width increased by 29.7% with bacterial application. In B. herlandii, bacterial application increased plant height by 13.3% and plant width by 20.4%. In shadowless application, the amount of chlorophyll in B. herlandii leaves was found to increase by 47.20% with bacteria and in B. microphilla, it increased by 65.86. In shadow application in B. herlandii, leaves were found to increase by 76.70% with bacteria; in B. microphilla, it increased by 94.93%. It was concluded that the bacteria application is more effective than others because Azotobacters fix the free nitrogen in the air to the boxwood soil, which needs continuous nitrogen for growth and development. For this reason, N-fixing bacteria applications to the soil can be used as an alternative to chemical fertilizer applications in boxwood cultivation or hedge formation.

A combination of biochemical fertilizers enhances plant nutrient absorption, water deficit tolerance, and yield of chickpea (Cicer arietinum L.) plants under irrigation regimes

Water shortage is the most critical abiotic stress and adversely impacts crop growth and productivity. Biofertilizers are an environmentally friendly method for sustainable agricultural development and improving plant water deficit tolerance. The effects of biological and chemical fertilizers on yield, yield components, and nutrient absorption of chickpea plants were studied in 2018 and 2019. The main plots were assigned to the irrigation levels [80% (I80) and 50% (I50)] and the subplot was assigned to 13 fertilizer combinations including free-living N-fixing bacteria (NB), potassium solubilizing bacteria (KB), phosphate solubilizing bacteria (PB), common chickpea nutrition program (F; NPK chemical fertilizer), and their combination. The results showed that shoot phosphorus content was increased by 80% when F + NPB (NPK chemical fertilizer and N + P biofertilizers) was applied at I80 compared with the control at I50. Furthermore, I80 and the application of PKB (P + K biofertilizers) and NPKB (N + P + K biofertilizers) obtained the highest shoot K and N concentrations, respectively. The NPKF + B-treated plants (N + P + K chemical fertilizer and N + P + K biofertilizers) demonstrated superior growth attributes such as plant height and the number of sub-branches at I80. The highest grain yield was obtained from the NPKF + B treatment at I80, which was 7.1-fold higher compared with the control at I50. In general, the combined application of biochemical fertilizers mitigated the adverse effect of water deficit and improved nutrient absorption and chickpea yield. The use of biochemical fertilizers can be efficient in reducing the consumption of chemical fertilizers and achieving sustainable agricultural goals.

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.

The Effect Of Dosage And Vermicast Types With Different Ingredients As An Organic Fertilizer Of Shallot (Alium Ascolonicum L.)

Vermicast is a used soil from worm maintenance that is product composting from its maintenance in the form of organic fertilizer and it is very suitable for plants. Vermicast contains various ingredients needed by plants that is hormones such as gibberellins, cytokinins, and auxins, and contains of nutrients (N, P, K, Mg and Ca) and Azotobacter sp. which is a non-symbiotic N-fixing bacterium which can help enrich the N element for plants. In the use of vermicast can be solid or liquid. The purpose of this research is to determine the effect of dosage and vermicast with different ingredients of feed as organic fertilizer for shallot. This research was conducted at the FPP Experiment Garden UMM in Tegalgondo Village with a height of ± 560 m above sea level. The study used a Randomized Block Design with two factors. The first factor: worm feed ingredients (K) consist of (K1); Blotong waste (K2); rumen waste (K3); combination of blotong and rumen waste. The second factor: the dosage of administration (U) consists of (U1); 4 Ton / ha (U2); 5 Tons / ha (U3); 6 Tons / ha (U4); 7 tons / ha. This research included nutrient content in vermicast and on the growth of shallot including: Length of plant, number of leaves, number of tubers, weight of fresh plant, weight of dry plant. The results of this research showed that the dosage and feed ingredients given had no significant effect on plant height parameters, number of leaves, weight of fresh plant, and weight of dry plant of shallot (Alium asconolicum L.) for However it was given significant effect for the height parameters of the plant at the age of 13 HST and the number of leaves at the age of 13 HST. And the best is the combination of K3U3 (Vermicast which is given a combination of blotong and rumen waste feed ingredients) with a dosage of 54 grams / plant.

Harnessing the power of microbes: Enhancing soybean growth in an acidic soil through AMF inoculation rather than P-fertilization

Abstract The low phosphorus (P) availability of acidic soils severely limits leguminous plant growth and productivity. Improving the soil P nutritional status can be achieved by increasing the P-content through P-fertilization or stimulating the mineralization of organic P via arbuscular mycorrhizal fungi (AMF) application; however, their corresponding impacts on plant and soil microbiome still remain to be explored. Here, we examined the effects of AMF-inoculation and P-fertilization on the growth of soybean with different P-efficiencies, as well as the composition of rhizo-microbiome in an acidic soil. The growth of recipient soybean NY-1001, which has a lower P-efficiency, was not significantly enhanced by AMF-inoculation or P-fertilization. However, the plant biomass of higher P-efficiency transgenic soybean PT6 was significantly increased by 46.74%–65.22% through AMF-inoculation. Although there was no discernible difference in plant biomass between PT6 and NY-1001 in the absence of AMF-inoculation and P-fertilization, PT6 had approximately 1.9–2.5 times the plant biomass of NY-1001 after AMF-inoculation. Therefore, the growth advantage of higher P-efficiency soybean was achieved through the assistance of AMF rather than P-fertilization in available P-deficient acidic soil. Most nitrogen (N)-fixing bacteria and some functional genes related to N-fixation were abundant in endospheric layer, as were the P-solubilizing Pseudomonas plecoglossicida, and annotated P-metabolism genes. These N-fixing and P-solubilizing bacteria were positive correlated with each other. Lastly, the two most abundant phytopathogenic fungi species accumulated in endospheric layer, they exhibited positive correlations with N-fixing bacteria, but displayed negative interactions with the majority of the other dominant non-pathogenic genera with potential antagonistic activity.

Seagrass-mediated rhizosphere redox gradients are linked with ammonium accumulation driven by diazotrophs.

Seagrasses are important marine habitats providing several ecosystem services in coastal waters worldwide, such as enhancing marine biodiversity and mitigating climate change through efficient carbon sequestration. Notably, the fitness of seagrasses is affected by plant-microbe interactions. However, these microscale interactions are challenging to study and large knowledge gaps prevail. Our study shows that redox microgradients in the rhizosphere of seagrass select for a unique microbial community that can enhance the ammonium availability for seagrass. We provide first experimental evidence that Rhizobia, including the symbiotic N2-fixing bacteria Bradyrhizobium, can contribute to the bacterial ammonium production in the seagrass rhizosphere. The release of O2 from rhizomes and roots also caused gradients of sulfide in rhizosphere areas with enhanced nifH transcription by sulfate-reducing bacteria. O2 release from seagrass root systems thus seems crucial for ammonium production in the rhizosphere via stimulation of multiple diazotrophic associations.

The potential of N-fixing bacteria consortium inoculation and NPK application in increasing soil N-total, plant N uptake and tomato (Lycopersicum esculentum Mill.) yields in Andisol

Nitrogen is an essential nutrient for growing tomato plants (Lycopersicum esculentum Mill.) on Andisol soil order. However, many farmers tend to use an excessive amount of inorganic fertilizers, which can have adverse effects on both the environment and tomato yield. To combat this problem, an alternative solution is to replace the inorganic fertilizer through inoculation of Azotobacter as an N-fixing bacteria. An experiment was conducted to examine the combined effects of the N-fixing consortium with NPK on total soil N, N uptake, Azotobacter spp. population, growth and the tomato plants yield. The experiment was performed on Andisols, located roughly 1250 m above sea level in West Java Province. The experimental design used was a Randomized Block Design, in three replications, consisting of A (Control), B (N-fixing inoculation), C (N-fixing + ¼ NPK), D (N-fixing + ½ NPK), E (N-fixing + ¾ NPK), F (N-fixing + 1 NPK), and G (1 NPK). The experiment revealed that the Lembang Andisol had an acidic pH, moderate available N, and high P retention. Applying Azotobacter sp. and Azotobacter vinelandii (N-fixing consortium) combined with one dose of NPK increased plant height and the total soil N content. N-fixing inoculation combined with 1/4 NPK, ½ NP, and ¾ NPK increased plant N uptake. The inoculation of N-fixing + ¼ NPK increased fruit weight, the number of fruits, and the yield per hectare of tomatoes. Inoculating Azotobacter sp. and Azotobacter vinelandii in mixed culture can reduce NPK usage by 75%, resulting in higher tomato yield.

Populasi Bakteri Penambat N2 Atmosfer pada Tanah Sawah yang Diberikan Herbisida dengan Berbagai Kandungan Bahan Aktif

Supporting the increase in agricultural production today cannot be separated from the use of herbicides in land preparation activities. Most of the herbicides applied to plants will eventually fall to the ground, then undergo changes and in a certain time will be absorbed by the clay fraction and organic matter in the soil, which is generally known as herbicide residue. Toxic herbicide residues in the soil can kill soil microbes, which are not actually the target (non-target microorganisms) so that they interfere with the activity of soil microorganisms which in turn can affect the nutrient cycle in the soil.This research was conducted with the aim of knowing the effect of giving herbicides with various types of active ingredients in paddy fields on the viability of N-fixing bacteria and their relationship to soil chemical properties.The research and analysis was carried out from November 2021 to January 2022. The method used in this study was the Completely Randomized Design (CRD) environmental design method with a single factor treatment design, namely the type of herbicide active ingredient. Based on the results of research that has been carried out, it is known that the herbicide Glyphosate can increase the population of atmospheric N2-fixing bacteria in the soil, while the herbicide Paraquat and Methyl Metsulfuron can suppress the population growth of atmospheric N2-fixing bacteria

Silver nanoparticles and silver/silica nanocomposites: Impacts on Z. mays L. growth, nutrient uptake and soil health

Although silver nanoparticles (Ag NPs) are widely employed in diverse industries, including agriculture, concerns about their adverse effects on plants at higher concentrations prompt exploration of alternatives, such as Ag/SiO2 NCs. Adding nano SiO2 is anticipated to create a complex with Ag+ ions, potentially decreasing their release into the environment and mitigating toxicity. The potential of Ag/SiO2 NCs as plant growth stimulants remains understudied to date. In this context, the study evaluates the impact of Ag/SiO2 NCs on 30-day-old Z. mays plants compared to Ag NPs at 100 and 200 ppm concentrations and on soil health. Soil health analysis revealed that both Ag NPs and Ag/SiO2 NCs supported the proliferation of P-solubilizing and N-fixing bacteria. Bioaccumulation analysis reveals higher Ag content in plants treated with Ag/SiO2 NCs, attributed to reduced agglomeration. Ag NPs exhibited concentration-dependent toxicity as 200 ppm hindered Z. mays growth, chlorophyll levels and absorption of P, Mg and K, whereas 100 ppm was found to be stimulatory. In stark contrast, Ag/SiO2 NCs demonstrated a remarkable capacity to mitigate Ag toxicity. The beneficial impact of Ag/SiO2 NCs on growth metrics, chlorophyll levels, lipid peroxidation, antioxidant enzyme activity and nutrient absorption was observed at both 100 and 200 ppm. However, it was more pronounced at 100 ppm concentration. This suggests that incorporating SiO2 in NCs may counteract the toxic effects of Ag, possibly through the complexation of Ag+ and a slower release mechanism.

The color of biodegradable mulch films is associated with differences in peanut yield and bacterial communities

Biodegradable mulch films (BDMs) are increasingly used in agricultural production as desirable alternatives to the current widespread use of polyethylene (PE) mulch films in China. However, potential effects of different colors of BDMs on field crop production and microbiomes remain unexplored. Here, the differences in bacterial communities of peanut rhizosphere soil (RS) and bulk soil (BS) under non-mulching (CK), PE, and three different colors of BDMs were studied. The results indicated that all treatments could increase the soil temperature, which positively affected the growth of the peanut plants. Moreover, mulching affected the bacterial community structure in RS and BS compared to CK. Furthermore, certain BDM treatments significantly enriched N-fixing bacteria (Bradyrhizobium and Mesorhizobium) and functional groups, increased the closeness of bacterial networks, and harbored more beneficial bacteria as keystone taxa in the RS. This in turn facilitated the growth and development of the peanut plants under field conditions. Our study provides new insights into the micro-ecological effects of mulch films, which can be affected by both the mulch type and color. The observed effects are likely caused by temperature and prevalence of specific microbial functions under the employed films and could guide the development of optimized mulching materials.

Ecological Restoration in Eastern Canada Using Four Early-Successional Species on Severely Degraded Sites Using a Factorial of Site-Preparation Treatments: Growth and Biomass over Two Years

Barren sites that lack soil are exposed to some of the harshest elements, which include high temperatures, solar radiation, wind, extreme temperature changes, and low soil moisture and nutrient conditions. An ecological restoration experiment was conducted using three site-preparation treatments, straw (S), Meri-Crusher (MC), and coarse woody debris (CWD), in a site-/no site-preparation 2 × 2 × 2 factorial on sites that had been barren for 25 years. In addition, four early successional deciduous species, white birch (WB, Betula papyrifera Marshall), gray birch (GB, Betula populifolia Marshall), green alder (GA, Alnus viridis Vill. subsp. crispa Ait), and speckled alder (SA, Alnus incana L. subsp. rugosa Du Roi), were examined. The two- and three-way interactions were almost all magnitude effects and not rank changes. Gray birch had the greatest overall first-year height growth, followed by GA, SA, and WB, with 12.1, 9.7, 9.6, and 5.6 cm, respectively. Straw doubled first-year growth, while CWD and MC increased first-year height growth by 43 and 31%, respectively. Straw’s ability to retain moisture in the dry summer provided the greatest benefit. In the second year, GA had the greatest height growth, followed by SA, GB, and WB, with 42.5, 30.5, 13.4, and 13.0 cm, respectively. Alders form symbiotic relationships with N-fixing bacteria and, although this was observed in some first-year roots, they did not fully express this advantage at these severely degraded sites until the second year, which allowed them to surpass birches in growth. Site-preparation treatments furthered their height growth affect, with S, and CWD doubling second-year height growth and MC, with an increase of 25%. Alders and birches had, on average, three and one stems, respectively, and the mean stem number of alders increased under S and CWD. After two years, overall stem dry mass had very large genus and species differences with GA, SA, GB, and WB, with 58.4, 30.3, 5.4, and 4.0 g, respectively. The N-fixing ability of alders under these conditions resulted in a 13-fold stem dry mass production increase compared with birches. Straw tripled, CWD doubled, and MC increased stem dry mass by 40%. For WB, site-preparation combinations had an additive effect, whereas GB, GA, and SA had several combined site-preparation treatments showing synergistic results, which were greater than the additive effects of single treatments. Under the control (no site prep.), second-year stem dry masses for WB, GB, GA, and SA were 0.7, 1.4, 17.8, and 0.5 g, respectively. Under the three combined treatments, MC × S × CWD, WB, GB, GA, and SA had 6.6, 12.3, 115.7, and 70.6 g stem dry masses, respectively. SA is ecologically a lowland species, hence the low 0.5 g under the control; however, the result under the three combined treatments demonstrates their combined effectiveness on these barren sites. Green alder seems to be the best adapted to the sites, having the greatest stem dry mass under control, although that was considerably magnified under the site-preparation treatments. This study using combinations of treatments with these early successional species introduces a novel research concept, and similar studies in the literature are currently lacking, creating an opportunity for future exploration.

Combined effect of cover crops and bio-fertilizer on sustainable popcorn maize production.

Cover crops play an important role in low-input cropping systems, increasing the use of agro-ecosystem services. Due to the lack of information about the impact of cover crops and bio-fertilizers on popcorn maize (Zea mays everta Sturt.) growth and yield quality, especially the popping volume and nutritive quality, such as concentrations of protein and mineral elements, this research aimed to provide essential information. The interrelation between popcorn maize productivity and quality with important groups of soil microorganisms presents additional novelty. The results demonstrated that field pea is a beneficial cover crop, especially when combined with a bio-fertilizer, supporting the accumulation of maize biomass, chlorophyll, yield potential, and the concentrations of protein, Ca, Mg, Fe, and Zn. In addition, field pea residues promoted N-fixing bacteria, and the number of total microorganisms, especially actinomycetes and decomposing bacteria, which could promote nutrient uptake and grain quality. Residues of cover crop mixtures, common vetch + winter oats and field pea + winter oats, promoted the total number of microorganisms in the soil, and up to the end of vegetation, a greater number of decomposition and ammonification microorganisms were found, especially when the bio-fertilizer was applied, which consequently could support greater maize biomass. Popping volume, as a main trait of popcorn maize, had the highest value in the common vetch + winter oats variant, supporting again the statement that quality traits could be enhanced in sustainable production. Unlike living cover crops, mulch mainly affected soil microbial communities and promoted the development of actinomycetes and cellulolytic microorganisms during the growing season. The results of this research could contribute to the development of sustainable popcorn maize production for improved grain quality. They could also serve as a basis for isolating beneficial soil microorganisms to develop new bio-fertilizers that could improve maize production in synergy with cover crops.