Low Nitrogen Availability Research Articles

Carbon and Nitrogen Stocks in Soil under Native Pastures in the Pantanal Wetland Biome, Brazil

The Pantanal has a high diversity of native pastures that provide food for many wild and domestic animals. Pantanal cattle raising is practiced in an extensive grazing-based system that varies according to the flood levels in the area. This study aimed to evaluate the fractions of soil organic matter in areas of native pastures under different uses and to quantify C and N stocks in sandy soils of the Pantanal. Soil samples from three native pastures differentiated by the predominance of Hymenachne amplexicaulis, Axonopus purpusii, and Mesosetum chaseae under different land use systems (continuous grazing and no grazing for five years) were collected and used to quantify the contents of carbon, nitrogen, and humic fractions. The dynamics of SOM are modified in grazed areas of the Pantanal, with influence on C and N, including their stocks. Native pastures of Axonopus purpusii and Hymenachne amplexicaulis showed an increase in organic matter after five years without grazing, while Mesosetum chaseae showed lower soil density and nitrogen levels. The highest C stock was observed in ungrazed areas of H. amplexicaulis (127.41 Mg ha−1 in the 0–40 cm layer). The dynamics of nitrogen in Pantanal pastures are influenced by the type of vegetation and land management, with higher nitrogen content in the surface layer (0–10 cm) and an increasing C/N ratio with soil depth, indicating lower nitrogen availability.

Breeding wheat for organic farming: Can the high grain protein gene Gpc-B1 help to tackle challenges in view of end-use quality?

Organic farming contributes to sustain healthy ecosystems, but challenges such as lower crop yields and supply of the nitrogen needs of crops remain. Wheat is the most important organic arable crop in Europe and grain protein content is the main quality trait also for grading organic wheat despite that high baking quality can be also realized at lower protein contents. Hence, breeding of organic wheat varieties that realize a stable high grain protein content even at lower nitrogen availability is of utmost importance to guarantee income of organic wheat growers. A major QTL for high grain protein content was identified in wild emmer and transferred into bread wheat. We tested six different wheat genetic backgrounds varying for the presence/absence of the functional Gpc-B1 allele in multi-location trials in Central Europe for their performance under organic growing. The increase in grain protein content caused by the functional Gpc-B1 allele was present in almost all genetic backgrounds, however, was not consistent across all tested quality traits. None the less, the functional Gpc-B1 allele may play a major role to increase the stability of organic wheat to reach minimum requirements by traders and processors with respect to grain protein content.

Alpine meadow and alpine steppe plant-soil network in Qinghai-Tibet Plateau, China

Alpine meadow and alpine steppe are crucial ecosystem types in the Qinghai-Tibet Plateau. However, due to ecosystem fragility and human disturbance, the nutrient imbalance between plant and soil leads to grassland degradation. From a systematic perspective, there needs to be a comprehensive understanding of the plant and soil traits within these two ecosystem types. This study addressed this gap by constructing plant-soil trait networks for alpine meadow and alpine steppe, identifying bridge traits, and comparing the stability and distinctions of the two trait networks. The results demonstrated a significant difference in the distribution of network structure edge weights between the alpine meadow and steppe. In the network of alpine meadow, the soil organic carbon was responsible for linking plant and soil traits, exhibiting the highest impact. Conversely, the network of alpine steppe revealed an increasing negative correlation between plant and soil traits. The results of bridge traits agreed with the optimal distribution hypothesis. The bridge traits of the alpine meadow were aboveground traits (AGB or PlantC), while those of the alpine steppe were belowground traits (BGB and RootN). Based on our findings, different management measures could be taken. The alpine meadow could be primarily restored through natural processes, and climate warming would enhance its carbon sequestration capacity. The alpine steppe ecosystem exhibits low nitrogen availability, which could be augmented through fertilisation or the return of yak manure.

Soil carbon in the boreal region under climate and land use change

AbstractCarbon cycling in boreal regions is controlled naturally by fire disturbance, climate, hydrology, snowmelt, soil heterogeneity, acidity, low nitrogen and phosphorus availability, mycorrhizal distribution, plant cover, and cryoturbation/permafrost at the northern edge. It is primarily altered by human management via and following land clearance. Each factor interacts with others in complex ways, creating a system characterized by high carbon storage and shaped by natural and anthropogenic disturbance. This paper examines boreal research to answer the question: ‘what are the primary factors controlling boreal carbon cycling?’ Though climate change threatens boreal systems, they may yet be resilient given many natural feedback loops that resist massive carbon loss. Perhaps the greatest danger is land conversion, which causes permanent losses and drastic alteration of certain carbon pools. Accordingly, it might be argued that it would be overall better to implement policies that keep these lands as forests, including managed forests, rather than convert to agriculture. Conversely, farming of marginal boreal soils might be managed to enhance carbon storage while satisfying local food security needs. However, the impact of agriculture on soil carbon storage is yet to be effectively quantified and initial results offer inconsistent assessments, reflected in the as‐yet natural sciences data‐scarce policy development. Research targeting long‐term carbon cycling, land conversion practices, agroforestry, and communication between boreal scientists and other groups (climate scientists, policymakers, public, and farmers) must be addressed through creation of long‐term experiments.

Growth and fatty acid profile of Nannochloropsis oceanica cultivated on nano-filtered whey permeate

Nano-filtered whey permeate (WP), a major by-product of dairy industry, is produced by membrane filtration of whey. The oleaginous microalga Nannochloropsis oceanica was successfully cultivated on WP without salinity and nutrient amendments. Growth, cell characteristics, and fatty acid profile of the cultures were analyzed using microscopy, flow cytometry, and GC analysis. WP was nitrogen limited, comprising primarily protein as a nitrogen source and only small amounts of free inorganic nitrogen (in the form of nitrate). Nannochloropsis oceanica (and associated bacteria) efficiently removed nitrate (100%), protein (87%), and phosphate (74%) from the whey permeate. Microscopic and flow cytometric analysis revealed diverse size distributions in whey permeate cultures, with significant cell aggregation attributed to low-salinity acclimatization and nitrogen limitation. Autofluorescence analysis revealed reduced photosynthetic activity in whey permeate-grown cells, possibly as a consequence of heightened mixotrophic activities on carbon source in the medium. Low nitrogen availability in whey permeate resulted in biomass with a fatty acid profile enriched in saturated fatty acids. Despite this, a considerable level of the omega-3 polyunsaturated fatty acid (in the form of eicosapentanoic acid or EPA) was detected at ca. 16% of total fatty acids. Whey permeate proved beneficial for the growth of N. oceanica and yielded high concentrations of eicosapentaenoic acid in the extracted lipids for potential applications in the feed/food industries.

Dendrometrical Structure and Physicochemical Analysis of Mangrove Sediments from the Nyong River Estuary (Cameroon, Atlantic Coast)

Mangrove estuaries are not immune to the threats posed by climate and anthropogenic constraints on aquatic environments. In the Nyong River estuary, mangrove ecotone has capital importance for biodiversity conservation due to its localization in the Douala-Edéa protected area. For this study, seven quadrats were delimited in aim to evaluate mangrove structure and assessed his interplay with sediment and water physicochemical characteristics. The study revealed a total of 120 individuals of 4 regularly encountered species over a distance of 14 km: <i>Rhizophora racemosa, Avicennia germinans, Rhizophora harrisonii </i>and <i>Phoenix reclinata</i> palms. The marshy soils under the mangrove have Total Nitrogen percentages varying between 0.04 and 0.68%. Total Organic Carbon (from 2.20 to 8.61%) and Total Organic Matter (from 3.66 to 14.64%) contents have a similar pattern. The ratios of Carbon and Nitrogen (C/N) reflect the presence of organic matter and plant debris over a large proportion of the estuary. The ratio of Nitrogen and Phosphate (N/P) reflects the low availability of nitrogen in relation to phosphorus. The cation elements evolve on average in the order Ca<sup>2+</sup> ˃Mg<sup>2+</sup> ˃Na<sup>+</sup> ˃K<sup>+</sup>. This study provides information that would help explore linkages for future research on biogeochemical balance in mangrove sediment and their implementation.

Soil-Microbial CNP Content and Ecological Stoichiometry Characteristics of Typical Broad-Leaved Tree Communities in Fanjing Mountain in Spring

This study aims to investigate the impact of diverse forest stand types and soil depths on soil ecological stoichiometry characteristics, shedding light on nutrient limitations and cycling patterns within the mid-subtropical forest ecosystem in southwest China during spring. The research focused on four representative forest stands situated in Fanjing Mountain: Castanopsis fargesii (C. fargesii), Cyclobalanopsis multiervis (C. multiervis), Cyclobalanopsis argyrotricha (C. argyrotricha), and Rhododendron argyrophyllum Franch (R. argyrophyllum). Sample plots were established in these forest types, and soil samples were collected from the 0–20 cm and 20–40 cm soil layers in March, spring of 2023. Various soil parameters, including pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), soil microbial biomass carbon (MBC), soil microbial nitrogen (MBN), and soil microbial phosphorus (MBP) were measured, and their stoichiometric ratios were calculated. The findings of the study were as follows: (1) In the 0–20 cm soil layer, C. argyrotricha exhibited the highest soil organic carbon, followed by C. fargesii, C. multiervis, and R. argyrophyllum with the lowest content. No significant differences in soil organic carbon were observed among the four forests in the 20–40 cm soil layer. Additionally, C. argyrotricha displayed a significantly higher soil C:N ratio compared to other forest types in different soil layers. In the typical broad-leaved forest area of Fanjing Mountain, the TP was classified as deficient. (2) In the 0–20 cm soil layer, the MBC of C. fargesii surpassed C. multiervis, C. argyrotricha, and R. argyrophyllum by 26.59%, 42.92%, and 24.67%, respectively. There were no significant differences in soil MBC:MBP ratio and MBN:MBP ratio, regardless of forest species and soil depths. The low availability of soil nitrogen in different forest stand types in Fanjing Mountain strongly limits soil microorganism biomass. (3) The correlation between SOC, TN, TP, and their stoichiometric ratios varied across different soil layers. Therefore, in managing the Fanjing Mountain forest area, attention should be paid to supplementing N and P in the soil.

OsCIPK2 mediated rice root microorganisms and metabolites to improve plant nitrogen uptake

Crop roots are colonized by large numbers of microorganisms, collectively known as the root-microbiome, which modulate plant growth, development and contribute to elemental nutrient uptake. In conditions of nitrogen limitation, the over-expressed Calcineurin B-like interacting protein kinase 2 (OsCIPK2) gene with root-specific promoter (RC) has been shown to enhance growth and nitrogen uptake in rice. Analysis of root-associated bacteria through high-throughput sequencing revealed that OsCIPK2 has a significant impact on the diversity of the root microbial community under low nitrogen stress. The quantification of nifH gene expression demonstrated a significant enhancement in nitrogen-fixing capabilities in the roots of RC transgenetic rice. Synthetic microbial communities (SynCom) consisting of six nitrogen-fixing bacterial strains were observed to be enriched in the roots of RC, leading to a substantial improvement in rice growth and nitrogen uptake in nitrogen-deficient soils. Forty and twenty-three metabolites exhibiting differential abundance were identified in the roots and rhizosphere soils of RC transgenic rice compared to wild-type (WT) rice. These findings suggest that OSCIPK2 plays a role in restructuring the microbial community in the roots through the regulation of metabolite synthesis and secretion. Further experiments involving the exogenous addition of citric acid revealed that an optimal concentration of this compound facilitated the growth of nitrogen-fixing bacteria and substantially augmented their population in the soil, highlighting the importance of citric acid in promoting nitrogen fixation under conditions of low nitrogen availability. These findings suggest that OsCIPK2 plays a role in enhancing nitrogen uptake by rice plants from the soil by influencing the assembly of root microbial communities, thereby offering valuable insights for enhancing nitrogen utilization in rice cultivation.

Heritable microbiome variation is correlated with source environment in locally adapted maize varieties.

Beneficial interactions with microorganisms are pivotal for crop performance and resilience. However, it remains unclear how heritable the microbiome is with respect to the host plant genotype and to what extent host genetic mechanisms can modulate plant-microbiota interactions in the face of environmental stresses. Here we surveyed 3,168 root and rhizosphere microbiome samples from 129 accessions of locally adapted Zea, sourced from diverse habitats and grown under control and different stress conditions. We quantified stress treatment and host genotype effects on the microbiome. Plant genotype and source environment were predictive of microbiome abundance. Genome-wide association analysis identified host genetic variants linked to both rhizosphere microbiome abundance and source environment. We identified transposon insertions in a candidate gene linked to both the abundance of a keystone bacterium Massilia in our controlled experiments and total soil nitrogen in the source environment. Isolation and controlled inoculation of Massilia alone can contribute to root development, whole-plant biomass production and adaptation to low nitrogen availability. We conclude that locally adapted maize varieties exert patterns of genetic control on their root and rhizosphere microbiomes that follow variation in their home environments, consistent with a role in tolerance to prevailing stress.

Schizolobium parahyba var. amazonicum seedling growth by Trichoderma spp. strains under nitrogen rates

This study evaluated the initial development of paricá (Schizolobium parahyba var. amazonicum) seedlings under different nitrogen rates with the application of Trichoderma spp., using a randomized complete block design in a 4x5 factorial scheme (strains and rates) with seven replications. The evaluated traits were plant height, stem diameter, leaf and stem fresh weights, leaf and stem dry weights, and aerial part dry and fresh weights. Trichoderma spp. strains did not satisfactorily promote paricá seedlings (Schizolobium parahyba var. amazonicum) under high nitrogen rates. However, the Trichoderma harzianum IBLF 006 WP strain was efficient only under low nitrogen availability.

Nitrogen Addition and Heterotroph Exclusion Affected Plant Species Diversity-Biomass Relationship by Affecting Plant Functional Traits.

(1) Background: Heterotrophs can affect plant biomass and alter species diversity-productivity relationships. However, these studies were conducted in systems with a low nitrogen (N) availability, and it is unclear how heterotroph removal affects the relationship between plant species diversity and productivity in different N habitats. (2) Methods: Three typical understory herbaceous plants were selected to assemble the plant species diversity (three plant species richness levels (1, 2, and 3) and seven plant species compositions), and the control, insecticide, fungicide, and all removal treatments were performed at each plant species diversity level in systems with or without N addition treatments. (3) Results: In systems without N addition, the insecticide treatment increased the plant aboveground biomass, total biomass, and leaf area, while the fungicide treatment reduced the plant belowground biomass, root length, and root tip number; the presence of Bidens pilosa increased the plant aboveground biomass. Similarly, the presence of Bletilla striata increased the plant belowground biomass and root diameter under each heterotroph removal treatment. In systems with N addition, all removal treatments reduced the plant belowground biomass and increased the plant leaf area; the presence of B. pilosa significantly increased the plant aboveground biomass, total biomass, and root length under each heterotroph removal treatment. The presence of B. striata significantly increased the plant belowground biomass and leaf area under insecticide and fungicide treatments. (4) Conclusions: Heterotroph removal alters the plant species diversity-biomass relationship by affecting the plant functional traits in systems with different N availabilities. The impact of biodiversity at different trophic levels on ecosystem functioning should be considered under the background of global change.

MINERAL NITROGEN DYNAMICS OVER TIME INFLUENCED BY PEANUT-WASTE BIOCHAR APPLICATION IN ALKALINE SOIL

Soil fertility in arid to semi-arid regions is constrained by extreme temperature fluctuations. Soils of such regions typically have low fertility levels, nitrogen (N) availability (due to ammonia volatilization and denitrification), and soil organic carbon (SOC) content. An incubation experiment was conducted to assess how a peanut-waste biochar (PB), produced at 300°C, influences the mineral N and chemical properties of an alkaline soil. The treatments included five PB rates (control, 5, 10, 15, and 20g PB kg−1 soil) and two fertilizer rates [no fertilization without additions of N and phosphorus (P) and fertilization with addition of 120kg N ha−1 and 90kg P ha−1]. The soil was incubated for various durations (0, 14, 28, 42, and 56days). There were significant temporal shifts in the mineral form of N in the incubated soil. Following 56days of incubation under fertilization, the treatment with 20g kg−1 PB revealed soil nitrate-N and ammonium-N levels of 15.8mg kg‒1 and 21.1mg kg‒1, respectively. With no fertilization, 20g kg−1 PB increased mineral N by 2.3-fold over the treatment without PB. This increase was 2.6-fold with fertilization. After 56days of incubation, in the presence of 20g kg−1 PB, there was a 19% increase in cation exchange capacity under fertilization and a 21% increase under no fertilization, compared to the respective treatments without PB. Immediately after the PB application, SOC was significantly increased, corresponding to PB rates. However, substantial increases were observed only in treatments with 15 and 20g PB kg−1 soil. In conclusion, the addition of 15 and 20g PB kg−1 to alkaline soil significantly increased N availability in soil, demonstrating the importance of biochar for N management in agricultural soils.

Interrelation between Nitrogen Doses and the Efficiency of Bt Genes in the Effective Control of Spodoptera frugiperda

The objective of this work was to identify the effect of nitrogen rates on Bt transgenic resistance and damage caused by Spodoptera frugiperda in corn plants at different developmental stages. The experimental design was a randomized complete block in a 3x6 factorial arrangement, with three potassium rates (0, 80, and 160 kg ha-1 kg of N) and six corn hybrids (20A55Hx, 30A77PW, AG1051, MG652PW, NS90VTPro2, and NS92VTPro), with three replicates. The data were analyzed through the analysis of canonical variables. Nitrogen doses interfere directly with the tolerance and resistance conferred by the Cry proteins of the plants in corn hybrids, altering the control of the caterpillar Spodoptera frugiperda and possibly favoring the breakdown of resistance in low availability. The corn hybrids showed divergent performance regarding proteins under low nitrogen availability (0 and 80 kg ha-1), and it was impossible to state which would be the most efficient protein. However, pyramiding has greater control under the recommended dose (160 kg ha-1 of N), with damage in the opposite direction to the transgenics.

Recent shift from dominant nitrogen to CO2 fertilization control on the growth of mature Qinghai spruce in China's Qilian Mountains

Terrestrial vegetation growth is stimulated by rising atmospheric CO2 concentration, a warmer climate, and increased soil nutrient availability. However, as plants age, progressive nutrient limitation is known to occur, especially in mature forests where soil nitrogen is deficient. Yet the long-term growth response of mature trees to rising CO2 accompanied by changing climate and nitrogen availability in semi-arid mountain regions is unclear. Here we used tree-ring widths and stable carbon (δ13C) and nitrogen (δ15N) isotopes to investigate the drivers of radial growth of mature Qinghai spruce (Picea crassifolia) in the central Qilian Mountains, northwest China, from 1840 through 2019. Tree growth benefited from improved nitrogen availability, chiefly via changes in bioavailable nitrogen pools modified by a favorable climate during 1930–1964. Enhanced intrinsic water-use efficiency (iWUE), driven by reduced stomatal conductance (gs) related to water deficit, lead to radial growth declines in 1985–2002. Recent acceleration of tree growth was largely attributed to a CO2 fertilization effect through enhanced iWUE during 2003–2019. Nitrogen availability was positively related to tree growth from the 1920s onward until greater CO2 fertilization ensued from 2000 onward. Hence, the negative effects of low nitrogen availability on growth could be mitigated or reversed by a high atmospheric CO2 concentration and warmer climate conditions. Our results suggest that mature spruce forests still harbor potential to increase ecosystem-level carbon sequestration and thereby partially mitigate climate warming. Such a nature-based solution in drought-prone forests would be achieved under warmer-wetter climate conditions in northwest China.

OsCBL1 modulates rice nitrogen use efficiency via negative regulation of OsNRT2.2 by OsCCA1

BackgroundFor cereal crop breeding, it is meaningful to improve utilization efficiency (NUE) under low nitrogen (LN) levels while maintaining crop yield. OsCBL1-knockdown (OsCBL1-KD) plants exhibited increased nitrogen accumulation and NUE in the field of low N level.ResultsOsCBL1-knockdown (OsCBL1-KD) in rice increased the expression of a nitrate transporter gene OsNRT2.2. In addition, the expression of OsNRT2.2, was suppressed by OsCCA1, a negative regulator, which could directly bind to the MYB-binding elements (EE) in the region of OsNRT2.2 promoter. The OsCCA1 expression was found to be down-regulated in OsCBL1-KD plants. At the low Nitrogen (N) level field, the OsCBL1-KD plants exhibited a substantial accumulation of content and higher NUE, and their actual biomass remained approximately as the same as that of the wild type.ConclusionThese results indicated that down-regulation of OsCBL1 expression could upregulate the expression of OsNRT2.2 by suppressing the expression of OsCCA1and then increasing the NUE of OsCBL1-KD plants under low nitrogen availability.

Pseudomonas aeruginosa LasI-dependent plant growth promotion requires the host nitrate transceptor AtNRT1.1/CHL1 and the nitrate reductases NIA1 and NIA2.

In P. aeruginosa, mutation of the gene encoding N-acyl-L-homoserine lactone synthase LasI drives defense and plant growth promotion, and this latter trait requires adequate nitrate nutrition. Cross-kingdom communication with bacteria is crucial for plant growth and productivity. Here, we show a strong induction of genes for nitrate uptake and assimilation in Arabidopsis seedlings co-cultivated with P. aeruginosa WT (PAO1) or ΔlasI mutants defective on the synthesis of the quorum-sensing signaling molecule N-(3-oxododecanoyl)-L-homoserine lactone. Along with differential induction of defense-related genes, the change from plant growth repression to growth promotion upon bacterial QS disruption, correlated with upregulation of the dual-affinity nitrate transceptor CHL1/AtNRT1/NPF6.3 and the nitrate reductases NIA1 and NIA2. CHL1-GUS was induced in Arabidopsis primary root tips after transfer onto P. aeruginosa ΔlasI streaks at low and high N availability, whereas this bacterium required high concentrations of nitrogen to potentiate root and shoot biomass production and to improve root branching. Arabidopsis chl1-5 and chl1-12 mutants and double mutants in NIA1 and NIA2 nitrate reductases showed compromised growth under low nitrogen availability and failed to mount an effective growth promotion and root branching response even at high NH4NO3. WT P. aeruginosa PAO1 and P. aeruginosa ΔlasI mutant promoted the accumulation of nitric oxide (NO) in roots of both the WT and nia1nia2 double mutants, whereas NO donors SNP or SNAP did not improve growth or root branching in nia1nia2 double mutants with or without bacterial cocultivation. Thus, inoculation of Arabidopsis roots with P. aeruginosa drives gene expression for improved nitrogen acquisition and this macronutrient is critical for the plant growth-promoting effects upon disruption of the LasI quorum-sensing system.

Nitrogen addition enhances tree radial growth but weakens its recovery from drought impact in a temperate forest in northern China

Forest growth in the majority of northern China is currently limited by drought and low nitrogen (N) availability. Drought events with increasing intensity have threatened multiple ecosystem services provided by forests. Whether N addition will have a detrimental or beneficial moderation effect on forest resistance and recovery to drought events was unclear. Here, our study focuses on Pinus tabulaeformis, which is the main plantation forest species in northern China. We investigated the role of climate change and N addition in driving multi-year tree growth with an 8-year soil nitrogen fertilization experiment and analyzing 184 tree ring series. A moderate drought event occurred during the experiment, providing an opportunity for us to explore the effects of drought and N addition on tree resistance and recovery. We found that N addition was beneficial for increasing the resistance of middle-aged trees, but had no effect on mature trees. The recovery of trees weakened significantly with increasing N addition, and the reduction in fine root biomass caused by multiyear N addition was a key influencing factor limiting recovery after moderate drought. Our study implies that the combined effect of increasing drought and N deposition might increase the risk of pine forest mortality in northern China.

Effects of arbuscular mycorrhizal fungi on plant invasion success driven by nitrogen fluctuations

Abstract Both enemies and mutualists play crucial roles in shaping plant invasion processes. Recent studies have suggested that resource fluctuations could indirectly promote plant invasion through higher trophic levels, such as enemies. However, the influence of mutualists like arbuscular mycorrhizal fungi (AMF) on plant invasion under nitrogen fluctuations remains untested. We conducted a pot mesocosm experiment using a three‐factorial experimental design to assess the individual and interactive effects of nitrogen availability, nitrogen fluctuation and AMF on invasive success of alien plants. We grew nine invasive alien species alongside five different native communities in pot mesocosms. These were then subjected to varied nitrogen availabilities (low vs. high), nitrogen fluctuations (constant vs. pulsed) and AMF presence or absence within a sterile substrate. We found that pulsed nitrogen supply increased the dominance of invasive alien species in low nitrogen availability, regardless of the presence or absence of AMF inoculation. However, in high nitrogen availability, pulsed nitrogen supply only enhanced this dominance in pots without AMF inoculation. This was tentatively evidenced by the three‐way interaction among nitrogen‐availability, nitrogen‐fluctuation and AMF‐inoculation treatments. Furthermore, the dominance promotion by nitrogen addition was greater than that by AMF inoculation. Synthesis and applications. Our findings present, for the first time, evidence that AMF may play a crucial role in mediating the promotion effects of nitrogen fluctuations on alien plant invasion. To better understand the invasion process of alien plants and evaluate their impact on native communities, future research should integrate abiotic and biotic drivers into a single framework. Furthermore, our findings underscore the importance of prioritizing habitats with higher nutrient availability and variability for protection against alien plant invasions.

Earthworm-invaded boreal forest soils harbour distinct microbial communities

Abstract. Earthworm invasion in North American forests has the potential to greatly impact soil microbial communities by altering soil physicochemical properties, including structure, pH, nutrient availability, and soil organic matter (SOM) dynamics. While most research on the topic has been carried out in northern temperate forests, little is known about the impact of invasive earthworms on soil microbial communities in hemiboreal and boreal forests, characterized by a slower decay of organic matter (OM). Earthworm activities can increase OM mineralization, altering nutrient cycling and biological activity in a biome where low carbon (C) and nitrogen (N) availability typically limits microbial and plant growth. Here, we characterized and compared microbial communities of earthworm-invaded and non-invaded soils in previously described sites across three major soil types found in the Canadian (hemi)boreal forest using a space-for-time approach. Microbial communities of forest floors and surface mineral soils were characterized using phospholipid fatty acid (PLFA) analysis and metabarcoding of the 16S rRNA gene for bacteria and archaea and of the internal-transcriber-spacer-2 (ITS2) region for fungi. In forest floors, the effects of earthworm invasion were minor. In mineral soil horizons, earthworm invasion was associated with higher fungal biomass and greater relative abundance of ectomycorrhizal fungi. Oligotrophic bacteria (Acidobacteriota and Chloroflexi) were less abundant in invaded mineral soils, where Gram(+) : Gram(−) ratios were also lower, while the opposite was observed for the copiotrophic Bacteroidota. Additionally, earthworm-invaded mineral soils harboured higher fungal and bacterial species diversity and richness. Considering the important role of soil microbial communities for ecosystem functioning, such earthworm-induced shifts in their community composition are likely to impact nutrient cycling, as well as vegetation development and forest productivity at a large scale, as the invasion progresses in these (hemi)boreal systems.

Influence of Vermicompost and Foliar Applications on Growth, Physiological and Yield Parameters of Irrigated Blackgram (Vigna mungo L. Hepper)

Field experiments were conducted at the South farm in Karunya Institute of Technology and Sciences, Division of Agronomy, Coimbatore, during the Rabi season of 2022. The experimental site is situated in the western agro-climatic zone of Tamil Nadu, at a latitude of 10°56'N and longitude of 76°44'E, with an elevation of 474 meters above mean sea level. The soil composition of the experimental field was identified as clay loam, moderately drained, and exhibited low availability of nitrogen (202 kg/ha), high availability of phosphorus (12.3 kg/ha), medium availability of potassium (415 kg/ha), and organic carbon content of 0.51%. The experiment followed a randomized block design (RBD) with 10 treatment groups, each replicated three times viz.,T1 - Control, T2 - Vermicompost 100% (on N Equivalent basis)+ Cowdung slurry, T3 -Vermicompost100% (on N Equivalent basis)+TNAU Biomineralizer,T4 -Vermicompost100% (on N Equivalent basis) + (Effective microorganism),T5 - Vermicompost 100% (on N Equivalent basis) + Pleurotus sp + Urea, T6- Vermicompost (50%) +RDF (50%) + Cowdung slurry, T7- Vermicompost (50%) +RDF (50%) + TNAU Biomineralizer, T8 -Vermicompost (50%) + RDF (50%) + EM (Effective Microorganism),T9 -Vermicompost (50%) + RDF (50%) + Pleurotus sp ,T10 - RDF alone. The objective of the study was to investigate the impact of vermicompost and other foliar applications on the growth, physiological characteristics, and yield parameters of an irrigated Black gram (VBN8 variety). The promotion of yield can be attributed to the increased vegetative growth and the balanced carbon-to-nitrogen (C: N) ratio, which likely stimulated the synthesis of carbohydrates. This, in turn, facilitated the overall improvement in seed yield. The application of RDF played a significant role in enhancing growth, leading to various positive changes in yield-related characteristics. Ultimately, the increased seed yield observed can be largely attributed to the improved plant growth and subsequent positive effects on yield-related attributes resulting from the RDF application. Thus, From this Experiment it was Concluded that the RDF (T10) Shows a highest range in growth, physiological and yield parameters of irrigated Blackgram due.