Soil Treatment Research Articles

Salt stress affects the bacterial communities in rhizosphere soil of rice

Salt is a primary factor limiting the utilization of saline lands in coastal beach areas, with rhizosphere microorganisms playing a crucial role in enhancing crop stress resistance and exhibiting high sensitivity to environmental changes. Rice (Oryza sativa L.) is the preferred crop for reclaiming salinized soils. This study determined the microbial communities in rhizosphere soil of rice under different salt stress treatments by high-throughput sequencing. We found that salt stress changed the bacterial community diversity, structure and function in rhizosphere soil of rice. Salt stress significantly reduced the richness and diversity of bacterial communities in rhizosphere soil of rice. The bacterial community was characterized by higher abundance of the phyla Chloroflexi, Proteobacteria and Actinobacteria; the relative abundances of Firmicutes, Acidobacteriota and Myxococcota were decreased, while Bacteroidota and Cyanobacteria were increased under salt stress. The functions of bacterial communities in rhizosphere soil of rice mainly include chemoheterotrophy, aerobic_chemoheterotrophy, phototrophy etc., chemoheterotrophy and aerobic_chemoheterotrophy were significantly higher NS3 (adding 3‰ NaCl solution to the base soil) treatment than NS6 (adding 6‰ NaCl solution to the base soil) treatment. These findings provide a theoretical foundation for the development of specialized salt-tolerant microbial agents for rice cultivation and offer a viable strategy for improving the soil environment of saline coastal lands through the application of beneficial microorganisms.

Bio-cementations: A Review on Enzyme and Microbially Induced Calcite Precipitation Mechanisms and Applications in Geotechnical Engineering

Modern methods to improve soil must deal with sustainable and green building purposes, and precipitated calcite is the most modern bio-cementation method to improve soil sustainably. Enzyme-induced calcite precipitation and microbially-induced calcite precipitation are precipitated calcite's best branches in bio-cemented soil improvement. EICP and MICP contain calcium chloride, urea, water, urease enzyme and other chemical materials (for MICP As nutrients for bacteria) that are mixed together to precipitate calcium carbonate in the soil. The precipitated calcium carbonate was worked as a binder between soil particles, filling the void and improving the soil's properties. By utilizing this technique in the field, several researchers were able to achieve favorable outcomes in the areas of soil improvement and other engineering applications, including concrete repair and other applications, while also taking into consideration the objectives of sustainability. treatment carried out on soils with one or many cycles of the treatment solution. The treatment revealed a significant improvement in the value of unconfined compression strength, compared to untreated soils. During certain experiments, the unconfined compression strength revealed that soils treated with the enzyme approach exhibited higher values compared to soils treated with a mixture containing a certain proportion of regular Portland cement. The encouraging outcomes that were achieved through the utilization of this test in both the laboratory and the field can be utilized in large-scale operations. Till now, this method has been considered under study. In Iraq there are no any research in term of EICP treatment while there are several research about using MICP in soil treatment.

Nanoparticles for treatment of cadmium-contaminated cocoa-growing soils and beans: Performance on metal immobilization and removal.

Some areas of tropical soils where cocoa grows contain high cadmium (Cd) concentrations. The cocoa plant's need for nutrition causes the reticular system to uptake the toxic metal, translocate it, and accumulate it in roots, stems, and other edible parts such as cocoa beans and shells, threatening the health of cocoa consumers. To cope with this difficulty, different treatments have been applied to cadmium-contaminated soils, but they showed limited success. In this study, we prepared multicomponent nanoparticles (MCNPs) to treat cocoa soils in fixed-bed columns and field tests. Also, MCNPs were mixed with two varieties of cocoa beans, CNN51 and Fino de Aromain, during the fermentation, aiming to capture the cadmium. Our field investigations began by collecting soil samples from three Ecuadorian cocoa-producing farms to determine their physicochemical properties, cadmium, and iron contents. A few weeks later, a home-built prototype was installed in a cocoa plantation to fabricate the nanomaterials using commercial-grade chemicals and rainwater. Scanning Electron Microscope (SEM) images showed MCNPs with an average size of 65.21 nm and the formation of chain-like aggregates. In contrast, MCNPs size was 76.6 nm, measured with Dispersed Light Scattering (DLS). The chemical composition of MCNPs was 90.7% Fe0 and 1.81% sulfur (S), analyzed by energy dispersal X-ray (EDX) and confirmed by X-ray diffraction (XRD) spectrometer measurements. Regarding the treatments, for the fixed-bed column tests, 0.28-1.08 L/kg was dosed into the soil, while for field treatments, 250, 500, and 835 mL/min MCNPs were injected in soil areas of 5 m2 surrounding each cocoa tree (0.5-4.5 mg MCNPs/kg soil) at depths between 0 and 5 cm. Test results revealed that the procedure applied in the field did not reproduce the metal’s immobilization (∼22%) as in the fixed-bed columns (∼80%). Moreover, cadmium removal was ∼ 20% and ∼75% after treating CCN51 and Fino de Aroma cocoa beans with 0.112 kg MCNPs/kg in the fermentation on-site and 0.034 kg MCNPs/kg in the laboratory. In this study, the size and chain-like aggregates of MCNPs notably influenced the field treatments as they precluded the filtration of MCNPs downwards. However, immobilizing cadmium could be more effective in soils with higher concentrations of the metal and multicomponent nanoparticles of smaller size, expanding our research scope and offering a practical solution to pollution issues in cocoa-growing regions.

The effect of applied micronutrients (Cu, Zn, Mn, and B) and chloride on annual canarygrass

Annual canarygrass is highly responsive to chloride (Cl−) fertilizer for increasing grain yield. This responsiveness to Cl− raises the question of whether annual canarygrass is similarly responsive to other micronutrients. The effect of micronutrients, Cu, Zn, B, and Mn with the basal rate of N, P, K, S, and Cl−, on annual canarygrass was studied using two application methods, soil (sideband at seeding) and foliar (3–6 leaf and flag-leaf emergence). Over 4 years, field research was conducted at two Saskatchewan locations, Indian Head and Melfort using a randomize complete block design (RCBD). A foliar application after flagleaf emergence of either Cu, Zn, or Mn provided the best method to increase the concentration of that micronutrient in the leaf tissue during seed filling. Boron concentrations in the leaf were increased during seed filling by soil or foliar treatments containing B at different site-years. Zinc, Cu, and B application had no impact on grain yield. A foliar application of Mn affected grain yield at one of six site-years and requires further investigation. As expected, soil application of macronutrients + Cl− increased grain yield between 29% and 187% compared to unfertilized treatment in five of six site-years. Melfort in 2015 and 2016 had low levels of tissue Cl− in control treatment. The largest grain yield increases occurred at these sites, suggesting the potential of early season tissue testing in identifying Cl− responsive fields of annual canarygrass. Annual canarygrass is not responsive to Cu, Zn, and B but may be responsive to Mn.

Accumulation of secondary metabolites in the family Lamiaceae as influenced by foliar micronutrients

The Lamiaceae family is rich in secondary metabolites, such as essential oils comprising flavonoids, phenolic compounds, and terpenoids. Micronutrients play a crucial role in plant metabolism and secondary metabolites production. This review summarizes and emphasizes the significance of foliar micronutrient nutrition in facilitating the accumulation of secondary metabolites in the Lamiaceae family, based on research literature from 2010 to 2023 using dependable databases like Scopus, Google Scholar, PubMed, and Science Direct. Spraying micronutrients notably enhanced the biosynthesis of various secondary metabolites in Lamiaceae species, especially for nutrients that do not move easily (Fe, Zn, Mn, Cu, B, and Si). Using nano-micronutrients as foliar application on Lamiaceae medicinal plants was more effective than traditional soil treatment. This review highlighted the importance of additional investigation on Cerium, Titanium, and Boron. Genera such as Lavandula, Satureja, Origanum, Lippia, and Hyssopus require more research in the future.

137Cs distribution in the system “agrochernozem clayey-illuvial – potato” in the area of radioactive contamination of the Tula region

The features of vertical distribution of 137Cs in the profile of clayeyilluvial agrochernozem, as well as biogenic migration of the radionuclide in the system “soil–plant” of potato agrocenosis have been studied. The research was conducted on the field, occupied by potato variety “Gala”, located in the central part of Plavsky radioactive hotspot of Tula region. It is shown that 35 years after the Chernobyl accident the density of surface radioactive contamination of arable soils in the region exceeds the permissible level by ≈5 times. The depth of 137Cs penetration down the soil profile is mainly determined by methods of agrotechnical soil treatment, and the main part of its inventories is concentrated in the upper 30-cm arable layer. This results in the direct contact of the radionuclide with underground organs of potato (roots, stolons and tubers). However, no more than 0.02% of the total 137Cs inventories contained in the system “agrochernozem–potato” is transferred to potato plants. It was also established that potato plants are characterized by contrasting distribution of 137Cs specific activity values wich varies with organs and tissues. Stolons and thin roots accumulate the radionuclide to the greatest extent per biomass, while tubers, on the contrary, – to the least extent. In general, the levels of 137Cs accumulation in the raw and dry weight of potato tubers, as well as in the products that have undergone culinary processing (boiling the unpeeled and peeled potatoes), correspond to sanitaryhygienic norms, which substantiates the low ecological risks of including potatoes in crop rotations on agricultural land in the area of the Plavsky radioactive hotspot of the Tula region.

A comparative assesment of biostimulants in microbiome-based ecorestoration of polycyclic aromatic hydrocarbon polluted soil.

Polycyclic aromatic hydrocarbons (PAHs) pose severe environmental and public health risks due to their harmful and persistent nature. Therefore, developing sustainable and effective methods for PAH remediation is crucial. This study explores the biostimulation potential of various nutrient supplements in enhancing the metabolic activities of indigenous oleophilic bacteria to PAH degradation and removal. The physicochemical and microbiological characterization of the soil sample obtained from the aged crude oil spill site prior to bioremediation revealed the presence of PAH and other hydrocarbons, reduced nutrient availability as well as an appreciable population of PAH degrading bacteria such as strains of Pseudomonas, Enterobacter, Kosakonia and Staphylococcus. The polluted soil treatment was conducted in six microcosms representing each nutrient supplement: casmes-CM, cocodust-CCD and osmocote-OSM slow-release fertilizers, NPK 20:10:10, casmes + cow dung - CM + CD and a control (unamended soil). Each pot contained 4kg of soil spiked with 4% Escravos crude oil to a final concentration of 989mg/kg of PAH, respectively. All treatments enhanced the activity of the indigenous bacteria to promote PAH removal (> 50%) after 35days although CM + CD had the highest biostimulation effect (B. E.) of 56% with 71.77% PAH attenuation followed by NPK treatment with B. E. of 54.9% and 70.4% PAH removal, respectively. The order of degradation of PAHs from lowest to highest is: control > casmes > osmocote > cocodust > NPK > CM + CD. First-order kinetic model revealed soil microcosm amended with CM + CD had a higher k value (0.0342day-1) and lower t½ (18.48day) and this was relatively followed by NPK treated soil. Biostimulation is an effective bioremediation approach to PAH degradation, however, a combined nutrient regimen in the presence of PAH-degrading microbes is more potent and eco-friendly in driving this process.

PGPR-Induced Biochemical Defense Mechanisms for Leafhopper (Amrasca devastans) Management in Okra Cultivation

Okra (Abelmoschus esculentus L. Moench) is a widely grown vegetable in Asia, valued for its nutritional properties and culinary uses. Nevertheless, it is significantly threatened by leafhoppers (Cicadellidae), which can transmit various plant viruses. To promote sustainable production and protect the crop from pest damage, a field study was conducted on a microplot in Kasilingapuram, Karungulam block, Thoothukudi district, during the Rabi season of 2020 and the Summer of 2021. Different Plant Growth-Promoting Rhizobacteria (PGPRs) were applied to the hybrid COBh 4 okra cultivars via soil, seed, and foliar treatments, and their effects on leafhopper populations were evaluated. The results indicated a notable reduction in leafhopper population in Bacillus subtilis Bbv57 treated okra plants than untreated plants during both Rabi 2020 and Summer 2021 seasons. Likewise, the biochemical parameters were also observed in elevated levels in Bacillus subtilis Bbv57 treated plants in both the seasons. These findings suggest that the use of PGPRs may be an effective approach for managing leafhopper populations in okra cultivation.

Effect of Water Retainer® During Seedling Period on Bioactive Components of Tomato (Solanum lycopersicum)

As a result of climate change, drought and the unequal distribution of rainfall is a worldwide problem. Drought stress on plants affects not only the yield, but also the amount and ratio of bioactive components in tomato fruit. The aim of the present work was to investigate the effect of a new soil biodegradable water-retention agent (Water and Soil’s Water Retainer®, Water and Soil Ltd., Budapest, Hungary) containing natural ingredients during the seedling period and under different irrigation conditions on the product volume, dry matter content and on some characteristic secondary metabolites in tomato fruits. The study was conducted to screen four different irrigation and soil treatment combination treatments for production and quality characteristics (polyphenols, tocopherols, carotenoids, vitamin C) to check the effect of seedling-stage stress on the tomato yield and bioactive components. Significant differences were found among the treatment and the cultivation seasons for the phytochemical content of fruits. The average yield and BRIX value did not change as a result of the Water Retainer® compared to the irrigated samples, but the amount of lycopene, Vitamin C, antioxidant capacity, and total polyphenol content increased significantly with the use of the Water Retainer®. In the two cultivation seasons, the highest concentration of lycopene and Vitamin C (114.30 ± 3.18 μg.g−1 and 338.10 ± 13.70 μg.g−1 fwt, respectively) was determined in fruits of 50% irrigation + 1.5 mL/m2 WR®-treated plants. The highest measured antioxidant capacity and total polyphenol content were 21.54 ± 0.17 mMTr/kg and 504 ± 44 mg GAE/kg, respectively, in the same treated samples. We found that seedlings exposed to drought stress, and after planting, when grown under ideal conditions in the field, can be distinguished from each other, despite the fact that there was only a difference between their cultivation during the seedling period. This may prove that rehydration is not sufficient to completely restore the metabolomic processes of stressed plants.

Seismic fragility analysis of geosynthetic-encased stone column composite foundation

The geosynthetic-encased stone column (GESC) is a cost-effective and efficient soil treatment method widely adopted in seismic regions. Its pivotal role in fortifying foundations enhances the safety of the supported structures. This study focuses on the fragility analysis of GESC composite foundations under seismic loads. The application of Logistic regression, a machine learning technique, derives parameterized fragility functions. These parameterized fragility functions elucidate the effects of GESC diameter, encasement tensile strength, column friction angle and soil variability on the GESC composite foundation's failure probability. The results demonstrated the efficiency of Logistic regression in predicting GESC foundation failure probability, boasting an impressive determination coefficient of up to 99.8 when compared with the Monte Carlo Simulations (MCS). Enhancing the tensile strength of the encasement and the column's friction angle reduces the failure probability in GESC foundations. Also, increasing the replacement ratio reduces the failure probability of the GESC foundation. However, for a constant replacement ratio and the same geosynthetic encasement, the seismic bearing capacity of a composite foundation reinforced by GESCs with small diameter is superior to that reinforced by GESCs with large diameter. Notably, inherent soil variability escalates the failure probability of GESC foundations, emphasizing the importance of selecting high-performance GESCs, especially when treating soil with strength that is characterized with a higher coefficient of variation (COV).

Consolidation characteristics of compacted clayey soils treated with various biomass ashes

The increasing volume of surplus soil generated from excavation works in infrastructure projects such as roads, railroads, and subway facilities poses significant environmental and logistical challenges, particularly in terms of its disposal. Therefore, the development of engineering technologies that promote the effective use of surplus soil has intensified. Among surplus soils, clay is soft and must be treated when used as a backfill or fill material. Cement-based stabilizers are commonly used for soil treatment; however, the production of cement involves high carbon-dioxide emissions, which conflicts with Japan's carbon-neutrality goals. This study investigates the use of alternative stabilizers derived from biomass waste, specifically palm kernel shell ash (PKSA) and rice husk ash (RHA), to treat clayey soils intended for use as a backfill material in road construction. Experiments are conducted to evaluate the compaction and consolidation properties of clayey soils treated with PKSA and RHA. The results indicate that both stabilizers reduced the maximum dry density and increased the optimum water content of the treated soils. PKSA and RHA treatments enhanced compaction control, particularly on the wet side above the optimum water content, thus facilitating the achievement of a high compaction degree of 95 % under high initial water contents. Consolidation test results indicate that treatment with PKSA and RHA increases the consolidation yielding stress and reduces the volume compressibility, and that these effects are more pronounced at higher compaction levels. These results suggest that adding PKSA or RHA can expand the load range that exhibits elastic settlement and may reduce the consolidation settlement. At the same addition rate, PKSA treatment increases the consolidation yielding stress more significantly than RHA treatment. Additionally, PKSA treatment improves the stiffness and reduces the hydraulic conductivity at lower consolidation pressures compared with RHA treatment, thus indicating the greater effect of PKSA. Based on results of scanning electron microscopy, the enhancement in the stiffness and permeability afforded by PKSA is attributed to the formation of needle-like ettringite crystals, which strengthened the soil structure. By contrast, RHA treatment results in densely packed particles, which is attributable to limited hydration reactions caused by low CaO and high SiO₂ contents. Thus, different mechanisms can result in different consolidation parameters of PKSA- and RHA-treated clays. However, both the PKSA- and RHA-treated clays indicate reduced coefficients of volume compressibility and permeability at a compaction degree of 95 %, with a stabilizer-to-clay ratio of up to 15 % by dry mass. Because neither PKSA nor RHA require high addition rates to improve the properties of surplus soft clays, these results suggest that PKSA and RHA can effectively enhance the compaction and consolidation properties of clayey soils. PKSA and RHA treatments are sustainable alternatives to the conventional cement-based treatments and support the environmental goals of construction projects.

Intercropping improves the yield by increasing nutrient metabolism capacity and crucial microbial abundance in root of Camellia oleifera in purple soil

Intercropping system influences the endophytic microbial abundance, hormone balance, nutrient metabolism and yield, but the molecular mechanism of yield advantage in Camellia oleifera intercropping with peanut is not clear. In this study, the C. oleifera monoculture (CK) and C. oleifera-peanut intercropping (CP) treatments in purple soil were conducted, and the physicochemical properties, gene expressions, signal pathways and crucial microbial abundances were investigated to reveal the molecular mechanism of the yield advantage of intercropped C. oleifera. The results showed that the intercropping system increased in contents of pigment, carbohydrate, available nitrogen and phosphorus in leaf and root, as well as the abundances of Burkholderia, Ralstonia, Delftia, Pseudoalteromonas and Caulobacter, enhanced the relative expression levels of CoSPS, CoGBE, CoGlgP, CoGBSS/GlgA genes to promote sugar metabolism, decreased the relative expression levels of CoASA, CoTSB, CoPAI, CoTDC and CoCYP71A13 genes for inhibiting IAA biosynthesis and signal transduction, as well as microbial diversity, Fusarium, Albifimbria and Coniosporium abundances in root, ultimately improved the fruit yield of C. oleifera. These findings indicate that intercropping system improves the fruit yield by enhancing the nutrient metabolism capability and crucial microbial abundances in root of C. oleifera in purple soil.

Effect of Fertilizers on Productivity and the Quality of Oilseed Flax Products

A review of domestic and foreign literature on the effect of fertilizers on the yield and quality of oilseed flax products (Linum usitatissimum L. ssp. intermedium) is given. It is shown that the use of fertilizers is an effective way to increase the seed productivity of flax. The effectiveness of fertilizers on the yield and oil content of seeds depends on many reasons: meteorological conditions during plant vegetation, fertilizer dosage, timing and methods of their application, methods of soil treatment, varietal characteristics, etc. In the first minimum, nitrogen acts to form an increase in the yield of oilseed flax seeds. Its optimal doses depend on environmental conditions and correspond to N30–60. At the same time, the best payback of 1 kg of applied nitrogen is achieved at a dose of no more than 30 kg of a.s./ha. The use of fertilizers is ambiguous, depending on the specific growing conditions: it affects the content of vegetable fat in seeds, reducing or increasing its concentration. At the same time, the use of fertilizers in most cases leads to an increase in oil collection per unit area. The database of removal of the main elements of nutrition (N, P2O5, K2O) by oilseed flax is presented. The average values and approximate intervals of the cost of nutrients per unit of basic production were calculated: for nitrogen they amounted to 34.8 kg/t (30.5–39.2 kg/t), phosphorus – 13.0 (11.4–14.5), and potassium – 29.9 kg/t (25.8–33.9 kg/t). They can be used as normative indicators when calculating fertilizer doses for the planned harvest.

Description of the first marine-isolated member of the under-represented phylum Gemmatimonadota, and the environmental distribution and ecogenomics of Gaopeijiales ord. nov.

The phylum Gemmatimonadota is widespread but rarely cultured and, in fact, there are only six described species isolated from soil, freshwater, and wastewater treatment. However, no isolates of Gemmatimonadota from marine environment have been described; thus, little is known about the physiology and metabolism of members of the marine lineages. In this study, four novel facultatively anaerobic bacterial strains belonging to Gemmatimonadota were isolated from marine sediments collected from Xiaoshi Island in Weihai, China, using an aerobic enrichment method. The integrated results of phylogenetic and phenotypic characteristics supported that these four strains represent one novel species in a novel genus, for which the name Gaopeijia maritima gen. nov., sp. nov. is proposed, as the first representative of novel taxa, Gaopeijiales ord. nov., Gaopeijiaceae fam. nov. in the class Longimicrobiia. Gaopeijiales was detected in 22,884 out of 95,549 amplicon data sets, mainly from soil. However, the highest mean relative abundances were in sponge (0.7%) and marine sediment (0.35%), showing salt-related character. Most of the Gaopeijiales subgroups potentially belong to the rare bacterial biosphere. The aerobic enrichment in this study could significantly increase the relative abundance of Gaopeijiales (from 0.37% to 2.6%). Furthermore, the metabolic capabilities inferred from high-quality representative Gaopeijiales genomes/MAGs suggest that this group primarily performs chemoorganoheterotrophic metabolism with facultatively anaerobic characteristics and possesses various secondary metabolite biosynthesis gene clusters (BGCs), mirroring those observed in the four novel strains.IMPORTANCEDespite rapid advances in molecular and sequencing technologies, obtaining pure cultures remains a crucial research goal in microbiology, as it is essential for a deeper understanding of microbial metabolism. Gemmatimonadota is a widespread but rarely cultured bacterial phylum. Currently, there are only six cultured strains of this interesting group, all isolated from non-marine environments. Little is known about the physiology and metabolism of members of the marine lineages. Here we isolated and characterized four novel marine strains, and proposed a new order Gaopeijiales within Gemmatimonadota. Furthermore, the global distribution, environmental preference, and metabolic potential of Gaopeijiales are analyzed using public data. Our work enriches the resources available for the under-represented phylum Gemmatimonadota and provides insights into the physiological and metabolic characteristics of the marine lineage (Gaopeijiales) through culturology and omics.

Trade-offs and adaptation to metalliferous soils: The role of soil microbiome in metal tolerance and uptake in Arabidopsis halleri ecotypes from a reciprocal transplant experiment

Soil contamination with trace metal elements is a worldwide issue, prompting research on plant species capable of hyperaccumulating metals to reduce soil toxicity. Previous research suggests that both plant species and their populations can affect soil microbial communities, yet little is known about how different populations of hyperaccumulator species influence these microbial communities to enhance metal-uptake and tolerance. This study evaluated the effect of soil origin, soil microbiome, and plant population on phytoextraction efficiencies of Cd and Zn among four A. halleri populations: two each from metalliferous and non-metalliferous sites. In a controlled transplant experiment, clonal replicates of A. halleri were grown in native and three non-native soils for six months. Biogeochemical analyses of plants and soils were conducted, alongside sequencing of root-associated soil bacterial/archaeal and fungal DNA. Soil treatments primarily differed in pH, total Cd, Pb, and Zn, as well as acid and alkaline phosphatase enzyme activities. A combined effect of soil origin and population was noted for arylsulfatase and β-glucosidase activities, as well as ammonium and nitrate concentrations. Both non-metallicolous and metallicolous populations accumulated high levels of Cd and Zn in metalliferous soils with the non-metallicolous population NM_PL14 outperforming the metallicolous populations in Zn hyperaccumulation. Interestingly, non-metallicolous populations grown in metalliferous soils exhibited no trade-offs in plant performance despite higher Cd and Zn accumulation. Soil origin had a stronger effect on the bacterial/archaeal and fungal community composition than plant ecotype. Partial least square regression models explained 66 % and 79 % of the variability in A. halleri Cd and Zn hyperaccumulation. There was a positive association between Zn-uptake and specific microbial taxa (e.g., Cornebacteriales, Microbacteriaceae, Propionibacteriales, Rhizobiaceae, Basidiomycota, Oidiodendron, Phallaceae) and functional activity (e.g., arylsulfatase, S oxidation) in metalliferous soils. Taken together, our findings suggest that non-metallicolous A. halleri populations may be better suited for Zn phytoextraction applications.

Effects of Fresh and Composted Azolla on Soil Chemical Properties

The rise in chemical fertilizer use in Malaysia raises concerns about soil degradation and potential long-term yield reductions, highlighting the importance of using organic matter for soil restoration. Azolla has been extensively studied as an alternative soil amendment due to its high nitrogen and nutrient content, as well as its rapid growth. However, the effects of fresh and composted Azolla amendments on soil chemical properties are not yet fully understood. A soil incubation study was thus conducted to determine the effects of fresh and composted Azolla on soil chemical properties over a 3-month incubation period. The soil treatments consisted of non-amended soil (control); fresh Azolla at 3, 6, and 9% w/w; and composted Azolla at 1, 2, and 3% w/w, with soil water holding capacity maintained at 55% throughout the incubation period. The collected soil samples were analyzed for soil pH and electrical conductivity (EC), total carbon (C) and nitrogen (N), available phosphorus, exchangeable bases—potassium (K), calcium, and magnesium, using inductively coupled plasma optical emission spectrometry, and cation exchange capacity (CEC). All data were subjected to variance analysis for statistical analysis. The study revealed significant effects of interaction between soil treatments and incubation periods for all soil parameters. At the end of the incubation period, the soil treated with 3% composted Azolla exhibited higher soil EC, total C and N, exchangeable K, and CEC compared to other soil treatments. The 3% fresh Azolla treatments were also observed to improve the soil’s exchangeable calcium by the end of the incubation period. In conclusion, 3% composted Azolla is best to help restore soil nutrient levels for crop uptake.

How do malfunctioning onsite wastewater systems influence water quality? Assessing treatment of nutrient and Escherichia coli in central North Carolina

Onsite wastewater systems (OWSs) can be significant sources of nutrients and E. coli to water resources, potentially resulting in water quality degradation especially during times of malfunction. An OWS is considered malfunctioning when septic tank effluent is discharged into drainfield trenches during periods when there is insufficient separation to groundwater (<30 cm), when wastewater upwells to the surface, or when backup of wastewater into the tank or home occurs. Few studies have quantified groundwater and surface water quality downgradient from malfunctioning OWSs. Thus, the goal of this study was to quantify nutrients and Escherichia coli in shallow groundwater and adjacent streams downgradient from malfunctioning OWSs. Three residences served by conventional-style OWSs were instrumented with piezometers near the drainfields for groundwater sample collection. Streams near two of the OWS were also monitored. Sites were sampled 10 times between Feb 2022 and Apr 2023. Samples were analyzed for nutrients, E. coli, and other water quality parameters. Results indicated that groundwater was typically within 30 cm of the trench bottom at 2 sites (Sites 100 and 200), thus these OWSs were malfunctioning for insufficient vertical separation distance. Groundwater beneath the 2 malfunctioning drainfields contained median concentrations of TDN (17.98 mg L−1), TDP (0.34 mg L−1), and E. coli (2419.6 MPN 100 mL−1) that were approximately 19, 34, and 576 times greater than concentrations in background groundwater. Groundwater near a functioning OWS (Site 300) had lower median concentrations of TDN (1.26 mg L−1), TDP (0.10 mg L−1), and E. coli (248.1 MPN 100 mL−1) compared to the malfunctioning sites. Drainfield groundwater regardless of functionality contained elevated pollutant concentrations relative to background groundwater, which had median concentrations of 0.95 mg-N L−1, 0.01 mg-P L−1, 4.2 MPN 100 mL−1 for TDN, TDP, and E. coli, respectively. Streams adjacent to the malfunctioning OWSs also contained elevated concentrations and exports of nutrients and E. coli relative to background. Thus, OWS malfunctions inhibited soil treatment processes contributing to elevated nutrient and E. coli pollution in receiving waters.

Management of carrot root-knot disease using Pochonia chlamydosporia nano- formulation

In vitro bio-assays were conducted to investigate the impact of a newly developed nano-formulation of Pochonia chlamydosporia, a fungus parasitic to the eggs and females of the root-knot nematode Meloidogyne incognita, which infects carrots. Second-stage juveniles (J2) and eggs of M. incognita were exposed to varying concentrations of the P. chlamydosporia nano-formulation (PCNF) ranging from 0.025 to 0.5% (0.25, 0.50, 1.0, 2.5 and 5.0 mL/L). Results demonstrated that PCNF exhibited antagonistic effects against M. incognita J2, with its activity increasing in proportion to both concentration and exposure time. Complete mortality of J2 was observed at a concentration of 5.0 mL/L after 96 h of exposure. At the same dose, PCNF parasitized 100% of M. incognita eggs. Subsequently, glasshouse bioassays were conducted to assess the effectiveness of different PCNF concentrations as a soil treatment in tomato plants challenged with M. incognita. Soil drenching with PCNF significantly reduced J2 density in soil (60.0–67.9%) and female density in roots (58.7–73.4%), along with reduced root-gall indices (2.1–3.1). Additionally, 61.0–87% eggs and 57.7–77.8% females were parasitized by P. chlamydosporia in carrot plants. Across concentrations from 0.25 to 5.0 mL/L, PCNF showed significant effectiveness in controlling M. incongnita pathogenesis in carrot. Further studies are recommended to evaluate the stability, shelf life and toxicity of PCNF before validating its use against natural M. incognita populations in field conditions.

Achieving synergistic benefits through integrated governance of cultivated cadmium contamination via multistakeholder collaboration

Rice serves as a vital staple food, but its accumulation of cadmium (Cd) has sparked widespread concerns regarding food safety and ecosystem security. Here, we conducted a seven-year systematic field experiment in the Xiangjiang River Basin of China, where an integrated governance framework (IGF) was established to ensure rice safety. The IGF, tailored to geographical zoning and pollution gradation, includes targeted soil treatments, crop management strategies, and stakeholder engagement. The quality of both the soil and the crop was improved, with a reduction in soil Cd availability of 36%, and a decrease in Cd in rice grain of 57-78%. This framework not only addresses multiple challenges but also supports sustainable development goals (SDGs 2, 3, 6, 9) by fostering comprehensive synergies among science, policy, and local community participation. Our findings provide empirical guidance for safe rice production in Cd-contaminated areas and provide solid scientific-driven decision support globally.

Alternative substrates for the production of container-grown Mexican marigold

ABSTRACT Objective: To evaluate substrate mixtures for the production of Mexican marigolds grown in containers in the community of Santa Cruz Itundujia, Oaxaca. Methods: Four soil mixtures were tested: 1) 70% ocote pine needles + 30% soil, 2) 70% leaf mold + 30% soil, 3) 70% river sand + 30% soil, and 4) 70% sawdust + 30% soil. Mexican marigold (Tagetes erecta) var. Inca II Deep Orange plants were established in pots under open field conditions. Height, number of leaves, plant width, branching, leaf area, and number of buds were evaluated in the different phenological stages of the plant; the last measurement was made at the flowering stage. Soil fertility parameters were analyzed, and physical analysis of the substrates was performed. Results: The treatments produced differential results; ocote pine needles + soil and leaf mold + soil were the best for producing container-grown marigolds. The lowest results in yield variables were found with the river sand + soil mixture. Implications: Using local and inexpensive substrates will impact production costs for marigold farmers. Currently, a variety of commercial mixes and substrates of foreign origin are available and used for the production of container-grown plants. Conclusions: The best results were obtained with organic substrates, specifically with ocote pine needles and leaf mold. The mixture with sawdust did not show good results in the tested variables, possibly due to this material’s high carbon/nitrogen ratio. The lowest results were obtained with the sand + soil treatment. Keywords: Asteraceae, yield, sawdust, needle, Tagetes erecta