Soil Phosphorus Levels Research Articles

Unraveling the microecological mechanisms of phosphate-solubilizing Pseudomonas asiatica JP233 through metagenomics: insights into the roles of rhizosphere microbiota and predatory bacteria

The effects of phosphate-solubilizing bacteria (PSB) on plant productivity are high variable under field conditions. Soil phosphorus (P) levels are proposed to impact PSB performance. Furthermore, the effect of exogenous PSB on rhizosphere microbial community and their functions are largely unexplored. Our study examined how different P background and fertilization affected the performance of PSB Pseudomonas asiatica JP233. We further conducted metagenomic sequencing to assess its impact on rhizosphere microbiota and functions, with a focus on genes related to soil P cycling. We found that JP233 could enhance P solubilization and tomato growth to different extent in both high and low P soils, irrespective of P fertilization. It was particularly effective in high P soil without extra fertilization. JP233 altered the rhizosphere microbial community, boosting taxa known for plant growth promotion. It also changed soil gene profiling, enriching pathways related to secondary metabolite biosynthesis, amino acids, carbon metabolism, and other key processes. Particularly, JP233 increased the abundance of most P cycle genes and strengthened their interconnections. Populations of certain predatory bacteria increased after JP233 inoculation. Our findings provide valuable insights into PSB’s mechanisms for P solubilization and plant growth promotion, as well as potential adverse impacts of resident microbes on bioinoculants.

Field Application of Mycorrhizal Inoculant Influences Growth, Nutrition, and Physiological Parameters of Corn Plants and Affects Soil Microbiological Attributes

Mycorrhizal inoculants can contribute to the development of corn crops by improving crop productivity. In this sense, the objective of this study was to evaluate the effects of a mycorrhizal inoculant on the dynamics of root system growth, gas exchange, corn crop productivity, and microbial activity in the rhizospheric soil in a no-till area with different levels of available soil phosphorus. The experiment was conducted during the 2019/2020 and 2020/2021 growing seasons. At 75 days after plant emergence, root morphological parameters (total root length (cm), average root diameter (mm), root surface area (cm2), and root volume), shoot biomass production, P content in the plant shoots, gas exchange, and microbiological attributes of the rhizospheric soil of corn were evaluated. At the end of the cycle, corn grain yield was determined. A beneficial effect of AMF inoculation was observed on the root and shoot parameters regardless of soil P level. Under conditions of evenly distributed rainfall during the experiment (2019/2020 season), AMF inoculation contributed to a 90% increase in acid phosphatase activity and a 76% increase in microbial biomass carbon (C-BIO), independent of soil P level. In contrast, under water deficit conditions (2020/2021 season), AMF inoculation provided a 29% increase in grain yield. We concluded that introducing a commercial mycorrhizal inoculant in corn benefits root system morphological parameters and physiological traits, and favors the activity of enzymes related to increased P availability, contributing to increased crop productivity in a no-till system.

Ecological Restoration Enhances the Stability and Associated Organic Carbon of Soil Aggregates in a Tibetan Alpine Meadow

ABSTRACTFencing and reseeding are two widely implemented ecological restoration strategies aimed at rehabilitating degraded grasslands globally. However, their effects on soil aggregates have been insufficiently explored. Employing the space‐for‐time substitution approach, we collected intact soils from a degraded alpine meadow, a fenced alpine meadow (natural restoration), a reseeded alpine meadow (interventional restoration), and an undegraded alpine meadow on the eastern Tibetan Plateau. Our main objective was to assess how the composition, stability, and associated organic carbon content of soil water‐stable aggregates responded to a 12‐year restoration effort in degraded alpine meadows. The results revealed that both restoration measures enhanced plant biomass, the levels of soil carbon, nitrogen, and phosphorus, as well as the concentrations of microbial phospholipid fatty acids. In contrast, these measures had a minimal effect on soil bulk density and glomalin‐related soil protein, while causing a reduction in soil pH. Post‐restoration, the mass proportion of macroaggregates increased notably by 66.45%–71.18%, whereas that of microaggregates and silt‐clay particles exhibited decreasing trends. The mean weight diameter and geometric mean diameter of the aggregates also significantly enhanced following restoration, indicating improvements in soil structural health and stability. However, the restored paddocks still showed lower aggregate stability than the undegraded paddock, suggesting that a longer restoration period may be required to fully recover the degraded soil structure. The aggregate‐associated organic carbon content significantly increased after reseeding but showed a negligible response to fencing alone. Nevertheless, both restoration measures improved the organic carbon stock within macroaggregates and its contribution to soil total organic carbon. Soil pH, total nitrogen content, and plant biomass were identified as key factors influencing the composition and associated organic carbon content of aggregates during restoration. Our findings indicate that ecological restoration enhances the stability and associated organic carbon accumulation of soil aggregates, primarily by promoting the formation of macroaggregates in degraded alpine meadows on the Tibetan Plateau.

Pseudomonas putida triggers phosphorus bioavailability and P-transporters under different phosphate regimes to enhance maize growth

The decline of available phosphorus in soil due to anthropogenic activities necessitates utilizing soil microorganisms that influence soil phosphorus levels. However, the specific mechanisms governing their interaction in Zea mays under diverse phosphate regimes remain largely unknown. The present study investigated the dynamics of phosphorus solubilization and the impact of organic acid supplementation in combination with the beneficial rhizobacterium Pseudomonas putida (RA) on maize growth under phosphorus-limiting and unavailable conditions. HPLC analysis revealed gluconic acid as the primary organic acid (OA) produced by P. putida across all three conditions (P-sufficient, P-limiting, and P-unavailable), with the highest production occurring under P-limiting conditions. The study evaluates the effects of RA, OA, and OA + RA on plant growth parameters under P-limiting and insufficient conditions, revealing significant alterations in growth and biochemical parameters (P = 0.05) compared to their respective untreated controls. Additionally, plants treated with organic acids and bacterial inoculation show increased phosphorus concentrations in both roots and shoots. Gene expression analysis of key phosphorus transporter genes (PHT1, PHO1, PTF, PHF1) further supports the role of organic acids and bacterial inoculation in enhancing phosphorus uptake. In conclusion, our study affirms that the secretion of gluconic acid by RA and its plant growth-promoting properties boost phosphorus uptake and maize growth by increasing phosphorus availability and influencing the expression of phosphorus transport-related genes.

Integration of physiology, genomics and microbiomics analyses reveal the biodegradation mechanism of petroleum hydrocarbons by Medicago sativa L. and growth-promoting bacterium Rhodococcus erythropolis KB1

Despite the effectiveness of microbial-phytoremediation for remediating total petroleum hydrocarbons (TPH)-contaminated soil, the underlying mechanisms remain elusive. This study investigated the whole-genome and biological activity of Rhodococcus erythropolis KB1, revealing its plant growth promotion (PGP), TPH degradation, and stress resistance capabilities. Phytoremediation (using alfalfa) and plant-microbial remediation (using alfalfa and KB1) were employed to degrade TPH. The highest TPH degradation rate, reaching 95%, was observed with plant-microbial remediation. This is attributed to KB1′s ability to promote alfalfa growth, induce the release of signaling molecules to activate plant antioxidant enzymes, actively recruit TPH-degrading bacteria (e.g., Sphingomonas, Pseudomonas, C1-B045), and increase soil nitrogen and phosphorus levels, thereby accelerating TPH degradation by both plants and microorganisms. This study demonstrates that R. erythropolis KB1 holds great potential for enhancing the remediation of TPH-contaminated soil through its multifaceted mechanisms, particularly in plant-microbial remediation strategies, providing valuable theoretical support for the application of this technology.

Intercropping in Coconut Plantations Regulate Soil Characteristics by Microbial Communities

Intercropping is a commonly employed agricultural technique that offers numerous advantages, such as increasing land productivity, enhancing soil health, and controlling soil-borne pathogens. In this study, Artemisia argyi, Dioscorea esculenta, and Arachis pintoi were intercropped with coconuts and compared with naturally growing weeds (Bidens pilosa), respectively. The regulatory mechanism of intercropping was examined by analyzing the variability in soil properties and microbial community structure across different intercropping modes and soil depths (0–20 cm, 20–40 cm, and 40–60 cm). The results indicate that intercropping can increase the diversity of soil bacteria and fungi. Moreover, as soil depth increases, the changes in microbial communities weaken. Intercropping reduced soil SOM and increased pH, which is directly related to the changes in the abundance of Acidobacteria in the soil. In various intercropping systems, the disparities resulting from intercropping with A. pintoi are particularly pronounced. Specifically, intercropping with A. pintoi leads to an increase in soil potassium and phosphorus levels, as well as an enhancement in the abundance of Bacillus sp., which plays a crucial role in the suppression of plant pathogenic fungi within the soil ecosystem. The results of the correlation analysis and structural equation modeling (SEM) suggest that the impacts of three intercropping systems on microbial composition and soil indicators exhibit considerable variation. However, a common critical factor influencing these effects is the soil phosphorus content. Furthermore, our findings indicate that intercropping resulted in lower soil nitrogen levels, exacerbating nitrogen deficiency and masking its impact on the microbial community composition.

Impacts of Soil Compaction and Phosphorus Levels on the Dynamics of Phosphate-Solubilizing and Nitrogen-Fixing Bacteria in the Peanut Rhizosphere

Soil properties, including soil compaction and the nutrient content, influence the composition and functions of rhizosphere microbial communities. There is limited information on how soil compaction and phosphorus application affect phosphate-solubilizing (PSB) and nitrogen-fixing bacteria (NFB). This study aimed to examine the responses of PSB and NFB in the rhizosphere of peanut (Arachis hypogaea L.) plants under varying soil compaction and phosphorus application levels. To address this, pot experiments were conducted to assess the composition and assembly processes of rhizosphere PSB and NFB in peanut cultivar Hua Yu 22 under two soil compaction levels (T1, 1.25 g/cm3 compaction, and T2, 1.00 g/cm3 compaction) and two phosphorus (P) levels (P0, no P applied, and P1, 1.2 mM P/kg soil applied). The results showed that PSB community shifts were closely correlated with the content of soil available phosphorus, soil acid phosphatase activity, soil nitrogenase activity, and soil compaction. Additionally, the content of soil available phosphorus and soil compaction were correlated with changes in operational taxonomic units of NFB. A network analysis revealed that the complexities of PSB were significantly higher than those of NFB. A stronger negative relationship was identified among NFB communities. The assembly of PSB communities was primarily driven by drift processes, whereas NFB communities were influenced by a combination of homogenizing selection and drift. Both PSB and NFB community compositions were significantly affected by phosphorus limitations and soil compaction. These findings enhance our understanding of the impacts of soil compaction and phosphorus application on PSB and NFB communities, with implications for optimizing peanut crop production. Our results will provide reference for crop cultivation in compacted and low-phosphorus soils. The important phosphate-solubilizing and nitrogen-fixing bacteria screened in the interaction network in this study will become candidate microbial agents for alleviating soil compaction and low phosphorus levels.

Soil Fertility Dynamics and Identify the Most Limiting Nutrients Affecting Walnut Productivity in Nepal

This study aimed to assess the soil nutrient status in walnut orchards of different ages in Jajarkot district, Nepal, to understand soil fertility dynamics and identify the most limiting nutrients affecting walnut productivity. The research employed a randomized complete block design (RCBD) with three treatments representing different age groups of walnut orchards (1-5 years, 6-10 years, and 11-15 years), each replicated seven times across various municipalities. The study was conducted in Jajarkot district, Karnali Province, Nepal, encompassing municipalities including Nalgad, Junichadey, and Barekot, from March to April 2023. Soil samples were collected from multiple depths (1, 2, and 3 feet) in each orchard and analyzed for pH, soil organic matter (SOM), total nitrogen, available phosphorus, and available potassium. Data analysis included descriptive statistics, one-way analysis of variance (ANOVA), and correlation analyses to explore relationships between soil parameters and orchard age. The study showed that significant variations were observed among different age groups of walnut orchards for soil pH, SOM, nitrogen, phosphorus, and potassium levels. Soil pH decreased with orchard age, while SOM, nitrogen, and phosphorus tended to increase with orchard age. Phosphorus was identified as the most limiting nutrient across all sampled soils, followed by nitrogen and potassium. Moreover, strong correlations were found between orchard age and soil N (r = 0.894, p < 0.01) and P (r = 0.776, p < 0.01), underscoring age-dependent nutrient dynamics. The study highlights the critical role of orchard age in shaping soil nutrient dynamics in walnut orchards. Older orchards exhibited higher levels of SOM, nitrogen, and phosphorus, indicating the accumulation of organic matter and nutrients over time. Phosphorus emerged as the primary limiting nutrient, essential for root growth, flowering, and fruiting in walnut trees. These findings underscore the importance of targeted fertilization strategies to optimize soil fertility and sustain long-term walnut productivity in the region.

Exploring the Organic Acid Secretion Pathway and Potassium Solubilization Ability of Pantoea vagans ZHS-1 for Enhanced Rice Growth.

Soil potassium deficiency is a common issue limiting agricultural productivity. Potassium-solubilizing bacteria (KSB) show significant potential in mitigating soil potassium deficiency, improving soil quality, and enhancing plant growth. However, different KSB strains exhibit diverse solubilization mechanisms, environmental adaptability, and growth-promoting abilities. In this study, we isolated a multifunctional KSB strain ZHS-1, which also has phosphate-solubilizing and IAA-producing capabilities. 16S rDNA sequencing identified it as Pantoea vagans. Scanning electron microscopy (SEM) showed that strain ZHS-1 severely corroded the smooth, compact surface of potassium feldspar into a rough and loose state. The potassium solubilization reached 20.3 mg/L under conditions where maltose was the carbon source, sodium nitrate was the nitrogen source, and the pH was 7. Organic acid metabolism profiling revealed that strain ZHS-1 primarily utilized the EMP-TCA cycle, supplemented by pathways involving pantothenic acid, glyoxylic acid, and dicarboxylic acids, to produce large amounts of organic acids and energy. This solubilization was achieved through direct solubilization mechanisms. The strain also secreted IAA through a tryptophan-dependent metabolic pathway. When strain ZHS-1 was inoculated into the rhizosphere of rice, it demonstrated significant growth-promoting effects. The rice plants exhibited improved growth and root development, with increased accumulation of potassium and phosphorus. The levels of available phosphorus and potassium in the rhizosphere soil also increased significantly. Additionally, we observed a decrease in the relative abundance of Actinobacteria and Proteobacteria in the rice rhizosphere soil, while the relative abundance of genera associated with acid production and potassium solubilization, such as Gemmatimonadota, Acidobacteria, and Chloroflexi, as well as Cyanobacteria, which are beneficial to plant growth, increased. These findings contribute to a deeper understanding of the potassium solubilization mechanisms of strain ZHS-1 and highlight its potential as a plant growth-promoting rhizobacteria.

Exploring the Effectiveness of Human Waste Compost in Improving Agricultural Soil: A Comparative Study with Poultry Manure, Cow Dung, and Vermicompost

The heightened application of chemical fertilizers to enhance agricultural output jeopardizes agricultural and environmental sustainability. The present study assessed the influence of various organic amendments on soil properties. The experimental design encompassed a Randomized Complete Block Design, with treatments that included a control group along with vermicompost, human waste compost, poultry manure, and cow dung. The primary focus of the experiment was to evaluate multiple soil attributes, such as soil texture, pH, electrical conductivity (EC), organic matter (OM), total nitrogen (N), available phosphorus (P), exchangeable potassium (K), available sulfur (S), and exchangeable sodium (Na), to determine the impact of different manure applications. The findings of the study confirmed significant alterations in soil physicochemical parameters due to the application of these treatments. Notably, poultry manure and vermicompost exhibited the most substantial positive effects on total nitrogen, resulting in increases of 0.16% and 0.14%, respectively. In cases of phosphorus deficiency, both poultry manure and human waste compost were found to be effective in increasing soil phosphorus levels. Moreover, vermicompost and poultry manure were found to enhance the exchangeable potassium levels, with values of 0.467 and 0.432 meq/100 g soil, respectively. Sulfur content was notably higher in plots treated with poultry manure (20.5 ppm), followed by vermicompost (17.87 ppm) and human waste compost (17.21 ppm). Additionally, the treatment with human waste compost exhibited the highest electrical conductivity (243 µs/cm), while poultry manure had the most significant impact on increasing organic matter, showing a substantial 2.76% increment. The study's findings advocate for a transition from chemical fertilizers to compost fertilizers, which would enhance agricultural soil and promote sustainability in both agriculture and the environment.

Enhancing phosphorus transformation in typical reddish paddy soil from China: Insights on long-term straw return and pig manure application via microbial mechanisms

Effective utilization of organic resources to activate residual phosphorus (P) in soil and enhance its availability is crucial for mitigating P resource scarcity and assessing the sustainable use of P in agricultural practices. However, the mechanisms through which organic resources affect soil P conversion via microorganisms and functional genes remain unknown, particularly in long-term organic-inorganic agricultural systems. In this study, we examined the impact of combined organic-inorganic fertilizer application on P availability, carbon (C) and P cycling genes, and microbial communities (bacterial and fungal) in reddish paddy soil based on a 42-year field experiment. The results indicated that long-term straw returning and pig manure application significantly augmented soil organic carbon (SOC), Olsen-P, microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), enzyme-P, and CaCl2-P levels in paddy soils. Furthermore, these practices increased the abundance of soil C degradation genes, reduced the abundance of soil P cycling genes, and altered microbial community structure and network complexity. Notably, Module #3 ecological clusters in the fungal ecological co-occurrence network were significantly correlated with P cycling genes. Finally, our study demonstrated that long-term straw returning and pig manure application in paddy fields facilitated two robust and contrasting predictive relationships between C degradation (negative relationship) and P cycling (positive relationship) genes, respectively, and enzyme-P and HCl-P changes to improve soil P availability. This study can enhance our understanding of the role of soil microbial communities and functional genes in mediating P transformation to decipher the enhancement in P application efficiency driven by organic resources in reddish paddy soils.

Soil fertility in mixed crop-livestock farming systems of Punjab, Pakistan: The role of institutional factors and sustainable land management practices

CONTEXTSoil salinization is a significant environmental challenge prevalent in arid and semi-arid regions, causing adverse effects on crop yields and jeopardizing household food security. Previous research has examined the influence of institutional dynamics and the adoption of sustainable land management practices in bolstering agricultural output, and some have investigated the interplay among socioeconomic determinants, institutional frameworks, and the uptake of climate-resilient and sustainable methodologies, or the association between soil health and agricultural productivity. Yet, there has been a lack of studies that considered this relationship altogether and their role in enhancing soil fertility. OBJECTIVEWe investigate the relationship among socioeconomic and institutional factors, adoption of sustainable land management practices, and the resulting changes in soil fertility between 2016 and 2019 within the context of mixed crop-livestock farms in the three irrigated agroecological zones of Punjab, Pakistan. A household survey was conducted in 2019 to complement soil attributes data collected by the Government of Punjab in 2016. Households that implemented sustainable land management practices between 2016 and 2019 were analysed to investigate the effect of various factors on soil fertility, including the adoption of sustainable land management practices and their influence on soil fertility dynamics. METHODSA structural equation model was employed to examine the relationship among exogenous variables, moderating variables, and endogenous variables, to explain their collective influence on soil fertility between the two periods. RESULTS AND CONCLUSIONSThe key findings highlight the significant role of institutional factors, including access to formal information channels such as extension services, demonstration trials, and credit facilities, alongside secure land rights, in predicting the adoption of sustainable land management practices such as gypsum application, laser land leveling, farmyard manuring, and agroforestry. Furthermore, specific SLM practices, particularly agroforestry featuring intercropping with Acacia spp. and farmyard manure application, exhibited positive impacts on change in soil organic matter, albeit with agroforestry showing a negative influence on soil phosphorus levels. The adoption of gypsum and LLL displayed positive effects on soil phosphorus levels over time, contrasting with LLL's adverse impact on soil organic matter. SIGNIFICANCEOur findings suggest that soil fertility benefits from policies enacted through public-private partnerships that lead to improved access to sustainable land management information, reduced credit barriers, establishment of local soil testing facilities, and expedited land entitlement processes. These findings highlight the critical role of collaborative partnerships and institutional arrangements in enhancing agricultural productivity and environmental sustainability.

Implications of current soil phosphorus levels for manureshed analysis in North Carolina

AbstractManure relocation strategies are needed to mitigate excessive phosphorus (P) application to agricultural land in areas of intensive animal agricultural production. This requires conceptual frameworks such as the manureshed, which categorizes agricultural areas according to the potential to export or receive manure for P fertilization. To further understand how the manureshed concept could be utilized, assessments of the potential implementation and necessity of the manureshed model are needed. With North Carolina at the center of the largest manureshed in the United States, North Carolina is an ideal test case to identify areas of concern for manure relocation under the manureshed framework. Swine and poultry dominate North Carolina's agricultural production, and because the vast majority of North Carolina producers are not required to limit manure applications to a P‐based rate, P accumulates. Therefore, soil test data from samples submitted to the North Carolina Department of Agriculture and Consumer Services (NCDA&CS) from 2017 to 2019 were used to determine how manureshed classes defined by Spiegal et al. correspond to current soil test P levels. It was determined that 36% of counties experience very high (>100 mg P kg−1; N = 36) median P concentrations in soil. Furthermore, fields cultivated with warm‐season forages had the highest mean P concentration (188 mg kg−1) and high median P trended toward counties with high animal production. Lastly, while mean soil P for all manureshed classifications fell into the very high category, manure source counties had the highest mean soil P concentrations (188 mg kg−1), which was 39%–52% higher than the other classifications. This suggests that, in addition to manuresheds classification, soil test data are needed to design and promote manure redistribution strategies.

Management strategies for reducing phosphorus levels in saltwater-intruded agricultural fields

As sea levels continue to rise and high tide flooding events increase in frequency, researchers and farmers alike are looking for solutions to adapt to and mitigate the effects of saltwater intrusion (SWI). Some landowners on the Lower Eastern Shore of Maryland respond to SWI by taking land out of agriculture. For example, they (1) attempt to remediate salt-damaged soils (e.g., planting switchgrass, Panicum virgatum), (2) restore native marsh grasses (e.g., planting saltmarsh hay, Spartina patens), or (3) abandon fields altogether (e.g., allow for natural recruitment). This work examines the ability of each of these land management practices to reduce phosphorus (P) levels in soils and porewater, with the overall goal to benefit both the farming community and water quality in the Chesapeake Bay. We show that remediation and restoration practices are efficient at taking up soil P and reducing porewater P concentrations through biomass P uptake. After three years of growth, we observed an increase in P uptake in biomass of Panicum virgatum (remediation species; 11–30 kg ha−1) and Spartina patens (restoration species; 4–18 kg ha−1) and a decline in available soil P pools (M3P; 30–50 % kg M3P ha−1). At all farms, under all three management strategies, the P fertility index value (FIV) in the topsoil was 33–50 % lower than baseline conditions, likely reducing the potential release of P to nearby waterways. Results from this work will help inform state-level coastal management policies and determine optimal strategies for climate resilience.

Nutrient Balance and Nutrient Use Efficiency of Irrigated Pigeon Pea [Cajanus cajan (L.) Millsp.] under Various Integrated Nutrient Management Practices

Aims: To evaluate the nutrient balance and nutrient use efficiency of irrigated pigeon peas under various integrated fertilizers Place and Duration of Study: The field trial was conducted at Instructional Farm (North), Karunya Institute of Technology and Sciences, Coimbatore. Methodology: During the growth phase of the pigeon pea crop, the soil's nitrogen, phosphorus, and potassium levels were monitored to assess their essential nutrient balance. This evaluation was conducted for each treatment, considering the specific nutrient application given to the crop. Additionally, the total quantity of nutrient uptake and the efficiency of nitrogen, phosphorus, and potassium utilization were calculated. Results: Higher availability of nutrients and nutrient uptake at harvest and the maximum values of computed balance and gain values in the nutrient balance studies and agronomic efficiency were observed in the integrated application of 75% RDF + 25% N eq as vermicompost (T2) Conclusion: The integrated application of 75% RDF + 25% N eq as vermicompost (T2) resulted in maximum available nutrients, plant uptake, agronomic efficiency and computed balance nutrient gain.

Influence of bamboo - soybean agroforestry system on soil chemical characteristics in northern transitional zone of Karnataka

A prospective avenue for sustainable land management in India involves the utilization of a bamboo-centered agroforestry system. A scientific research was conducted during the kharif season of 2022 at the Main Agricultural Research Station in Dharwad to investigate the soil chemical characteristics within an agroforestry framework centered around bamboo and soybean. The composite samples were analyzed for several chemical attributes including pH, electrical conductivity (EC), soil organic carbon (SOC), available nitrogen, available phosphorus, and available potassium. The experiment featured five distinct treatments denoted as T1 (Bambusa balcooa + Soybean), T2 (Dendrocalamus stocksii + Soybean), T3 (Dendrocalamus asper + Soybean), T4 (Bambusa vulgaris + Soybean), and T5 (Sole soybean). Notably, the soil pH exhibited a decline under the bamboo-based agroforestry system when compared to the exclusive soybean cultivation. However, there was no statistically significant variance observed in soil electrical conductivity (EC) between the control and the agroforestry systems. Moreover, the levels of soil organic carbon (SOC), available nitrogen (N), phosphorus (P), and potassium (K) were notably higher in the bamboo-centric agroforestry system compared to the sole soybean cropping. Consequently, the sustained adoption of a bamboo-focused agroforestry system has the potential to enhance soil chemical attributes and enrich nutrient status over the long term.

Soil fertility as a mediator of interactions between an introduced specialist beetle and a native generalist nematode on an exotic invasive plant and its native congener

Abstract Invasive plants are often attacked by both introduced specialist and native generalist natural enemies in new ranges. Soil fertility can potentially alter the interactions of these natural enemies with native versus invasive plants in ways that have largely unexplored implications for biological invasions and biological control. A common garden experiment was conducted to compare the performance of an introduced specialist flea beetle, Agasicles hygrophila, and/or a native generalist nematode, Meloidogyne incognita, on invasive alligator weed, Alternanthera philoxeroides, and its native congener sessile joyweed, Alternanthera sessilis, under different levels of soil nitrogen (N) and phosphorus (P). At a relatively low or moderate N and P levels, the flea beetle and the nematodes were not significantly affected by each other. Under these conditions, alligator weed responded plastically by producing more branches and biomass, as well as longer stolons, in response to attack by the flea beetle and/or the nematode, compared to sessile joyweed responses to similar levels of damage. However, under a relatively high N and P levels, nematode infestations significantly reduced flea beetle damage on alligator weed, resulting in significantly greater above‐ and below‐ground biomass and longer stolons than plants without herbivory. In contrast, beetle herbivory significantly increased the level of nematode infestations on sessile joyweed, resulting in significantly fewer fine and coarse roots, and lower above‐ and below‐ground biomass compared to plants without herbivory. Synthesis and applications. Our findings illustrate the importance of soil fertility in mediating interactions between specialist biocontrol agents and native generalists on native versus invasive plants. High phenotypic plasticity seems to be an important attribute that contributes to the success of invasive plants like alligator weed in relatively nutrient‐poor environments. However, nutrient‐rich environments could potentially confer greater growth benefits on invasive plants than on native ones by changing herbivore–herbivore interactions on plants differently. There is a great need to fully investigate the direct and indirect interactions between biocontrol agents and generalists across food webs following classical biocontrol releases. Nutrient measurements of both soil and water bodies should also be incorporated into all stages of biocontrol programmes.

Green manure incorporation enhanced soil labile phosphorus and fruit tree growth.

The incorporation of green manures substantially enhances the conversion of external phosphorus (P) fertilizers and soil-reserved P into forms readily available to plants. The study aims to evaluate the influence of green manure additions on soil phosphorus dynamics and citrus growth, considering different green manure species and initial soil phosphorus levels. Additionally, the research seeks to elucidate the microbiological mechanisms underlying the observed effects. A citrus pot experiment was conducted under both P-surplus (1.50 g·P·kg-1) and P-deficient (0.17 g·P·kg-1) soils with incorporating legume (Leg), non-legume (Non-Leg) or no green manure residues (CK), and 18O-P labeled KH2PO4 (0.5 g, containing 80‰ δ18Op) was additionally introduced to trace the turnover characteristics of chemical P fertilizer mediated by soil microorganisms. In P-surplus soil, compared with the CK treatment, the Leg treatment significantly increased soil H2O-Pi (13.6%), NaHCO3-Po (8.9%), NaOH-Pi (9.5%) and NaOH-Po (30.0%) content. It also promoted rapid turnover of P sources into H2O-Pi and NaHCO3-Pi pools by enhancing the phoC (576.6%) gene abundance. In contrast, the Non-Leg treatment significantly augmented soil H2O-Pi (9.2%) and NaHCO3-Po (8.5%) content, facilitating the turnover of P sources into NaHCO3-Pi pools. Under P-deficient soil conditions, compared with the CK treatment, the Leg treatment notably raised soil H2O-Pi (150.0%), NaHCO3-Pi (66.3%), NaHCO3-Po (34.8%) and NaOH-Pi (59.0%) content, contributing to the transfer of P sources into NaHCO3-Pi and NaOH-Pi pools. This effect was achieved through elevated ALP (33.8%) and ACP (12.9%) activities and increased pqqC (48.1%), phoC (42.9%), phoD (21.7%), and bpp (27.4%) gene abundances. The Non-Leg treatment, on the other hand, led to significant increases in soil NaHCO3-Pi (299.0%) and NaHCO3-Po (132.6%) content, thereby facilitating the turnover of P sources into NaHCO3-Pi and NaOH-Pi pools, except for the phoC gene abundance. Both Leg and Non-Leg treatments significantly improved citrus growth (7.3-20.0%) and P uptake (15.4-42.1%) in P-deficient soil but yielded no substantial effects in P-surplus soil. In summary, introducing green manure crops, particularly legume green manure, emerges as a valuable approach to enhance soil P availability and foster fruit tree growth in orchard production.

Soil properties and quinoa yield as affected by irrigation and vermicompost application under a drip-tape irrigation system

IntroductionQuinoa a crop with high nutritional value has the widespread adaptability to different climates and there is an increased demand for this product in the world. Characterized by roots with extensive penetration capabilities and wide, alternate leaves giving rise to diverse inflorescences, quinoa plants exhibit variable heights ranging from 20 to 300 cm. The duration of their growth phase spans 95 to 125 days’ contingent upon cultivar selection and prevailing climatic conditions.Materials and methodsIn order to reduce chemical fertilizers consumption through using organic fertilizers a two-year study was conducted at the Research Farm of the University of Kurdistan, Iran, during the 2021–2022 growing seasons. In this study the effects of varying levels of irrigation and vermicompost application on soil characteristics and quinoa (Chenopodium quinoa) yield were investigated. The experiments were arranged as split plots within a randomized complete block design. The main factor consisted of four irrigation levels (50%, 75%, 100%, and 125% of quinoa’s water requirement), while the sub-factor encompassed four vermicompost application rates (0, 5, 10, and 15 tons per hectare). The irrigation method employed was a drip-tape irrigation system with a seven-day interval between irrigations, and water quantities were measured using a volumetric meter on the main pipeline.ResultsThe results demonstrated that the highest levels of available soil phosphorus (21.83 mg kg−1) and soil ammonium (36.08 mg kg−1) were observed in the treatment receiving 50% of quinoa’s water requirement combined with 15 tons per hectare of vermicompost. Additionally, the application of 15 tons per hectare of vermicompost led to the highest concentrations of soil nitrate (14.16 mg kg−1), available potassium (144.62 mg kg−1), and quinoa seed yield (1784.01 kg ha−1)). Over both years, the greatest activity of alkaline and acid phosphatase enzymes was noted in the treatment receiving 125% of quinoa’s water requirement in combination with 15 tons per hectare of vermicompost. Vermicompost application was found to enhance yield and ameliorate drought stress by enhancing soil physical and chemical properties and improving soil moisture retention.

Metagenomic insights into the response of soil microbial communities to pathogenic Ralstonia solanacearum.

Understanding the response of soil microbial communities to pathogenic Ralstonia solanacearum is crucial for preventing bacterial wilt outbreaks. In this study, we investigated the soil physicochemical and microbial community to assess their impact on the pathogenic R.solanacearum through metagenomics. Our results revealed that certain archaeal taxa were the main contributors influencing the health of plants. Additionally, the presence of the pathogen showed a strong negative correlation with soil phosphorus levels, while soil phosphorus was significantly correlated with bacterial and archaeal communities. We found that the network of microbial interactions in healthy plant rhizosphere soils was more complex compared to diseased soils. The diseased soil network had more linkages, particularly related to the pathogen occurrence. Within the network, the family Comamonadaceae, specifically Ramlibacter_tataouinensis, was enriched in healthy samples and showed a significantly negative correlation with the pathogen. In terms of archaea, Halorubrum, Halorussus_halophilus (family: Halobacteriaceae), and Natronomonas_pharaonis (family: Haloarculaceae) were enriched in healthy plant rhizosphere soils and showed negative correlations with R.solanacearum. These findings suggested that the presence of these archaea may potentially reduce the occurrence of bacterial wilt disease. On the other hand, Halostagnicola_larseniia and Haloterrigena_sp._BND6 (family: Natrialbaceae) had higher relative abundance in diseased plants and exhibited significantly positive correlations with R.solanacearum, indicating their potential contribution to the pathogen's occurrence. Moreover, we explored the possibility of functional gene sharing among the correlating bacterial pairs within the Molecular Ecological Network. Our analysis revealed 468 entries of horizontal gene transfer (HGT) events, emphasizing the significance of HGT in shaping the adaptive traits of plant-associated bacteria, particularly in relation to host colonization and pathogenicity. Overall, this work revealed key factors, patterns and response mechanisms underlying the rhizosphere soil microbial populations. The findings offer valuable guidance for effectively controlling soil-borne bacterial diseases and developing sustainable agriculture practices.