Soil Copper Research Articles

Advances in viticulture via smart phenotyping: current progress and future directions in tackling soil copper accumulation

Modern viticulture faces significant challenges including climate change and increasing crop diseases, necessitating sustainable solutions to reduce fungicide use and mitigate soil health risks, particularly from copper accumulation. Advances in plant phenomics are essential for evaluating and tracking phenotypic traits under environmental stress, aiding in selecting resilient vine varieties. However, current methods are limited, hindering effective integration with genomic data for breeding purposes. Remote sensing technologies provide efficient, non-destructive methods for measuring biophysical and biochemical traits of plants, offering detailed insights into their physiological and nutritional state, surpassing traditional methods. Smart phenotyping is essential for selecting crop varieties with desired traits, such as pathogen-resilient vine varieties, tolerant to altered soil fertility including copper toxicity. Identifying plants with typical copper toxicity symptoms under high soil copper levels is straightforward, but it becomes complex with supra-optimal, already toxic, copper levels common in vineyard soils. This can induce multiple stress responses and interferes with nutrient acquisition, leading to ambiguous visual symptoms. Characterizing resilience to copper toxicity in vine plants via smart phenotyping is feasible by relating smart data with physiological assessments, supported by trained professionals who can identify primary stressors. However, complexities increase with more data sources and uncertainties in symptom interpretations. This suggests that artificial intelligence could be valuable in enhancing decision support in viticulture. While smart technologies, powered by artificial intelligence, provide significant benefits in evaluating traits and response times, the uncertainties in interpreting complex symptoms (e.g., copper toxicity) still highlight the need for human oversight in making final decisions.

Poly-γ-glutamic acid chelates chromium (III) and copper (II), alleviating their toxicity in cucumber and affecting rhizosphere bacterial community assembly.

The accumulation of chromium (Cr) and copper (Cu) in soil during industrialization and modernization poses an extreme threat to crops. Poly-γ-glutamic acid (γ-PGA) has the potential to stabilize heavy metals in soil through chelation because of the numerous carboxyl groups in its side chain. The rhizosphere microbiome contributes to plant detoxification by participating in heavy metal passivation. However, it is still unclear whether γ-PGA can alleviate the toxicity of Cr and Cu to plants and whether this effect is associated with changes in the rhizosphere microbiome assembly. Here, we found that γ-PGA application significantly reduced the content of Cr or Cu in cucumber plants by 67.45%-86.77% and 94.67%-98.21, respectively, and alleviated the oxidative stress of Cr or Cu to plants. Moreover, γ-PGA significantly increased the biomass of cucumber fruits in the plot experiment by 13.5% and 25.3% under Cr and Cu stress, respectively. The content of Cr or Cu in the cucumber fruit was below limits of detection, in contrast to the 31.23 mg/kg Cr or 9.86 mg/kg Cu detected in the no-γ-PGA treatment. γ-PGA effectively chelated Cr and Cu in vitro, and less than 30% of their chelates were degraded in 20 weeks, suggesting the strong stability of these chelates. γ-PGA significantly altered the rhizosphere bacterial community composition of cucumber by enriching phyla Gemmatimonadota, Acidobacteriota and Firmicutes, and genera Gemmatimonas and Stenotrophomonas, which potentially involved in reducing the mobility of Cr and Cu in soils. Furthermore, γ-PGA significantly enriched taxa assigned to plant growth-promoting bacteria (PGPB). Together, our results suggest that γ-PGA can reduce the Cr and Cu contents in cucumber, and this process is strongly associated with the chelation capacity of γ-PGA and its effects on rhizosphere microbiome composition. These results highlight the exciting potential to use γ-PGA for the remediation of heavy metal-contaminated soils.

Accumulation of heavy metals (Cr, Cu, As, Cd, Pb, Zn, Fe, Ni, Co) in the water, soil, and plants collected from Edayar Region, Ernakulam, Kerala, India

The accumulation of heavy metals in the environment is a significant concern due to their potential toxicity and persistence. This study investigates the levels of heavy metal contamination in the water, soil, and plants of the Edayar region in Ernakulam, Kerala, India. The region has experienced industrialization and urbanization, leading to concerns about heavy metal pollution. The study aims to assess the concentrations of chromium (Cr), copper (Cu), arsenic (As), cadmium (Cd), lead (Pb), zinc (Zn), iron (Fe), nickel (Ni), and cobalt (Co) in water, soil, aquatic and terrestrial plants. Samples were collected from various locations within the Edayar region, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was conducted to quantify heavy metal concentrations. The findings of this study will contribute to the assessment of heavy metal pollution in the Edayar region. Plants with a high diversity index were taken for analysis from both aquatic and terrestrial habitats. Scoparia dulcis L. seems to specialize in metal accumulation, possibly for protective purposes. Synedrella nodiflora Gaertn demonstrates adaptability to metal-rich environments through robust metal uptake and tolerance mechanisms. Alternanthera philoxeroides (Mart.) Griseb, on the other hand, appears to have developed mechanisms to manage heavy metal exposure. The results indicate significant levels of heavy metal contamination across all samples, with the highest concentrations detected in soil, followed by water and plants. Chromium and lead levels in soil exceeded the permissible limits set by international standards, posing potential risks to human health and the ecosystem. The accumulation patterns in plants varied, with higher bioaccumulation factors observed for zinc and copper, suggesting their preferential uptake. This study highlights the urgent need for remediation strategies and continuous monitoring to mitigate the impact of heavy metal pollution in the Edayar region. The results will help in understanding the environmental impact of human activities.

Biochar addition enhances remediation efficiency and rapeseed yield in copper-contaminated soil.

Soil contamination with copper (Cu) threatens ecological security and human health. Rapeseed demonstrates potential in remediating copper-contaminated soil, and biochar-assisted phytoremediation is increasingly being employed to improve remediation efficiency. However, the combined application of them has not been thoroughly studied in terms of the synergistic effects and the mechanisms of their interaction. In this regard, this study conducted a pot experiment to evaluate biochar-assisted remediation under Cu-contaminated soil with varying biochar application rates; Furthermore, the plant physiological mechanism and soil physicochemical properties involved in the biocharrapeseed system was explored. Our results showed that the exchangeable pool of copper in soil decreased by 10.0% and 12.3% with adding 5% biochar (BC1) and 10% biochar (BC2) relative to control (BC0), respectively, prior to rapeseed cultivation. The rapeseed cultivation for one season further reclaimed 4.9%, 9.0%, and 13.6% of the available copper in this soil by root extraction under the BC0, BC1, and BC2 treatments, respectively. The overall copper concentration in plants decreased by 23.7% under BC2 and 13.3% under BC1 compared to BC0. However, the plant's dry biomass at BC1 and BC2 treatments increased by 1.7-fold and 2.7-fold relative to BC0, which offset the negative impact of the decreased copper concentration on phytoremediation. Physiological analysis showed adding 10% biochar decreased the MDA content by 36% in the leaf and 49% in the root, compared to BC0. The transmission electron microscopy for cell wall ultrastructure in root tips showed that biochar addition in Cu-contaminated soil increased the mechanical strength of the celL wall, explicitly increasing the thickness of the secondary cell wall. Further cell wall components analysis revealed a remarkable increment of the pectin content in BC2 relative to BC0, increased by 56% in the leaf and 99% in the root, respectively. Additionally, 10% biochar application led to a roughly 2-fold increase in seed yield via ameliorating the soil physicochemical properties and increasing the rapeseed growth. These findings offer insights into synergistic rapeseed-biochar use for Cu-contaminated soil remediation.

Prevention values for copper (low tier approach) in subtropical acidic soils.

Copper is a trace element in plants and animals whose importance can be understood due to its role in different essential metabolic processes. Anthropogenic activities such as agriculture and mining are potential sources of pollution due to the emission of copper into the environment. Brazilian legislation ties soil quality to guideline values, among which the Prevention Value indicates the critical environmental limit for trace elements. The aim of this study was to obtain PVs for copper for two subtropical soils (Cambisol and Nitisol), given that the pedological richness was not considered when deriving the PVs contained in the federal normative. Reproduction assays followed ISO guidelines with the earthworm species Eisenia andrei and Perionyx excavatus, the enchytraeids Enchytraeus crypticus and Enchytraeus bigeminusand the springtails Folsomia candida and Proisotoma minuta. Results showed that the sensitivity of the organisms was greater in Cambisol. The most sensitive species were the earthworms, especially Perionyx excavatus (EC50 = 67.83 in Cambisol; EC50 = 264.96 in Nitisol). The springtails, on the other hand, were the least sensitive to contamination. These findings reinforce the need to include organisms from different ecological groups in ecotoxicological assessments. It was also observed that the PV adopted in federal legislation (= 60mgkg-1) is in fact protective for the species and soils we evaluated, since the PVs we obtained based on the EC50 were 346.74mgkg-1 in Nitisol and 134.05mgkg-1 in Cambisol. It is important to note that our results do not exclude the need for evaluations with other subtropical soils, given the influence of their properties on the toxicity and bioavailability of copper to soil organisms.

A quantitative review of the effects of biochar application on the reduction of Cu concentration in plant: a meta-analysis.

Contamination and toxicity of copper (Cu) in soils are global issues, particularly in regions where Cu-based fungicides are utilized. Elevated Cu concentrations can lead to soil contamination and pose significant risks to the ecosystem, including plant life, wildlife, and human health. The application of biochar has been proposed as a viable strategy to mitigate Cu accumulation in plants. However, there is no quantitative and data-based consensus on the impact of biochar on plant Cu accumulation. In this meta-analysis, 624 data records from 65 published literature were collected and the effects of various factors, including biochar properties, experimental conditions, and soil properties on Cu accumulation in plants, were examined through meta-subgroup analysis and meta-regression models. The results obtained indicate a significant dose-dependent effect of biochar in decreasing Cu concentration in plants by an average of 23.45%. Soils with acidic pH values and medium textures were more conducive for biochar to mitigate Cu accumulation in plant tissues. In addition, manure biochar and green waste biochar were found to be more successful in decreasing Cu concentrations in plants compared to other biochar types. Biochar types with pyrolysis temperatures of > 600°C and pH values of ≥ 10 resulted in greater decreases in plant Cu concentration. Regarding biochar application, biochar minimum range of 1% in potting experiments and 20 t/ha in field experiments have been recommended to effectively decrease Cu concentration in plants. Overall, these findings provide valuable insights into Cu transfer mitigation through food chain to human bodies and for policymakers to take preventive measures.

Stable isotopes analysis combined with X-ray absorption spectroscopy reveal the fate of organic waste-borne copper and zinc in amended soils

Copper (Cu) and zinc (Zn), two potentially toxic trace elements, are commonly abundant in organic wastes (OWs) recycled in soils as fertilizer. Yet current knowledge on the long-term behavior and fate of Cu and Zn in soil following OW spreading is scant. We addressed this issue by studying the fate of OW-borne Cu and Zn in amended soils from four different long-term field experiments. By combining the stable isotope analysis and X-ray absorption spectroscopy, we identified changes in Cu and Zn concentrations, speciation and isotopic compositions in the amended soils only when OW had been applied at high rates over long periods. Under these conditions, we highlighted that: (i) all OW-derived Cu and Zn had accumulated in the topsoil layer regardless of the soil and OW type; (ii) the amended soil isotopic signatures were the result of the mixing of OW-borne and natural Cu and Zn; and (iii) Cu and Zn exhibited distinct speciation patterns in amended soils. Indeed, the unprecedented persistence of OW-borne crystallized Cu(I)-sulfide in the amended soils contrasted with the complete transformation of pig slurry-borne nanosized Zn-sulfide or household compost-derived amorphous Zn phosphate and Zn complexed by organic matter.

Effect of Organic Nutrient Sources on Economics, Soil Micro Nutrient Status and Microbial Growth of Ragi under Guni Method of Cultivation

A field experiment was conducted during the kharif-2019 at the farmers field of Mylandahalli in Chikkaballapura distict of Karnataka, to study the effect of organic nutrient sources on soil micro nutrient status, microbial count and economics of finger millet under guni method. The trial was framed out in randomized blocked design with twelve treatments reproduced thrice. The results of different organic nutrient sources were showed that supplement of sericulture waste compost (SWC) @ 50% N eq. + Enriched biodigested liquid manure (EBDLM) @ 50% N eq. ha-1 + panchagavya (PG) spray @ 3% (T9) had a significant effect on micro nutrient status in soil and their values were statistically higher than all the other treatments. The findings of study reported that supplement of sericulture waste compost (SWC) @ 50% N eq. + Enriched biodigested liquid manure (EBDLM) @ 50% N eq. ha-1 + panchagavya (PG) spray @ 3% (T9) recorded significantly higher Diethylenetriamine pentaacetic acid (DTPA) extractable iron, zinc, manganese and copper in soil. Likewise, the same treatment had recorded significantly superior in population of bacteria (49.96 colony forming units (CFU) x 106 g-1), fungi (27.36 CFU x 103 g-1) and actinomycetes (14.44 CFU x 103 g-1) were noticed compared to others and found to be highest economic returns during cropping period of kharif 2019.

A geographically weighted neural network model for digital soil mapping of heavy metal copper in coastal cities

Assessing the spatial distribution of heavy metals in soil is essential for mitigating risks to human health and ensuring the sustainable use of soil resources. This study proposed a geographically weighted neural network (GWNN) model, leveraging deep learning and geographically weighted regression (GWR). The model was designed based on the GWR concept to address the spatial autocorrelation of copper (Cu) in soil and incorporated convolutional neural network (CNN) to capture the nonlinear relationships between Cu and environmental covariates. The GWNN model was compared with GWR, extreme gradient boosting (XGBoost), and artificial neural network (ANN) models. XGBoost was employed to select important environmental covariates and spatial autocorrelation of Cu concentrations was assessed using Moran’s I. The model’s performance was evaluated using 10-fold cross-validation, and prediction uncertainty was quantified with 100 bootstrap models. The results indicated that temperature covariates were the most significant predictors of soil Cu concentrations. The R2 values for Cu prediction accuracy were 0.60 for GWNN, 0.53 for ANN, 0.49 for XGBoost, and 0.32 for GWR. The spatial distribution of Cu showed a trend of higher concentrations in the north and lower concentrations in the south, consistent with spatial clusters identified by local Moran’s I. The mean uncertainty of the 90% confidence interval for GWNN was 16.49%, closely aligning with XGBoost (15.44%) and ANN (16.29%) and significantly outperforming the GWR (18.25%). Overall, the GWNN model demonstrated strong predictive accuracy and low uncertainty, offering an improved approach for digital soil mapping applications.

Organic matter mitigates biotic impact of copper in fruit orchard soil

Inorganic copper (Cu) fungicides and bactericides are widely used to control disease in fruit and vegetable crops and has led to widespread accumulation of the metal in soil beyond regulatory thresholds. We aimed to elucidate the impacts of Cu on soil health within cherry orchard soils in New Zealand, focusing on three biological indicators: earthworm behaviour, soil respiration, and plant growth. We sampled soils from four blocks of different ages within a single orchard, varying in amounts of accumulated soil Cu (7 - 263 mg kg-1) but also in Soil Organic Matter (SOM) content (3 - 10 %). Experimental work was designed to isolate the impacts of both Cu and SOM on three critical biological descriptors: earthworm behaviour, soil respiration and root growth. Soils were amended to standardise both variables in laboratory and glasshouse experiments. The results demonstrated a pronounced inhibition of soil respiration and root development, as well as adverse effects on earthworm behaviour, with increasing Cu concentrations. SOM played a mitigating role, reducing the bioavailability and toxicity of Cu to soil organisms. However, the buffering capacity of SOM is limited and long-term reliance on SOM to mitigate Cu toxicity is not sustainable. Currently Cu continues to accumulate in most orchard soils. This study highlights the importance of assessing Cu bioavailability and soil health in the context of orchard management.

Revolutionizing Food Safety and Crop Production: Harnessing Novel Biosensors

Farmers and food manufacturers are under immense pressure from consumers and food safety regulations to deliver pollutant-free, high-quality foods. The extensive use of chemicals in food production poses ecological as well as health risks. In order to meet the demand for safe, preservative-free foods, rapid sensing techniques are required. Traditional analysis methods are time consuming, laboratory bound, expensive and require highly skilled personnel. Alternative analysis systems such as biosensors, which are user-friendly and enable real-time monitoring in the field should also be used. Biosensors have been developed to detect foodborne pathogens such as Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, etc. that cause food contamination, and a large number of cases are reported annually. Mycotoxin-contaminated food presents a serious threat to food safety. Biosensors have been utilised to identify Penicillium and aflatoxin infections, which are major mycotoxins found in food. Additionally, biosensors for identifying artificially ripened fruits have also been developed. Biosensors have been developed to detect pesticide residues such as atrazine, glyphosate, 2,4-D, methyl parathion, lindane, etc. Early identification of plant pathogens, including bacteria, viruses, and fungi, is crucial because it enables farmers to take the necessary precautions to control the disease. Pathogens such as Fusarium sp., Phytophthora palmivora, tomato leaf curl virus are among some of the pathogens that have been successfully detected using novel biosensors. They can also be used for detecting heavy metals as they are cheaper, faster, more reliable and selective than traditional analysis methods. A bacterial biosensor was developed using Bacillus megaterium, which was sensitive to heavy metals like cadmium, copper and zinc in soil. Additionally, biosensors have been developed to detect heavy metal pollution in plants as well as irrigation water.

Copper and zinc adsorption in tropical soils

Copper and zinc adsorption in tropical soils

Monitoring Soil Copper in Urban Land Using Visibale and Near-Infrared Spectroscopy with Spatially Nearby Samples.

Soil heavy metal contamination in urban land can affect biodiversity, ecosystem functions, and the health of city residents. Visible and near-infrared (Vis-NIR) spectroscopy is fast, inexpensive, non-destructive, and environmentally friendly compared to traditional methods of monitoring soil Cu, a common heavy metal found in urban soils. However, there has been limited research on using spatially nearby samples to build the Cu estimation model. Our study aims to investigate how spatially nearby samples influence the Cu estimation model. In our study, we collected 250 topsoil samples (0-20 cm) from China's third-largest city and analyzed their spectra (350-2500 nm). For each unknown validation sample, we selected its spatially nearby samples to construct the Cu estimation model. The results showed that compared to the traditional method (Rp2 = 0.75, RMSEP = 8.56, RPD = 1.73), incorporating nearby samples greatly improved the model (Rp2 = 0.93, RMSEP = 4.02, RPD = 3.89). As the number of nearby samples increased, the performance of the Cu estimation model followed an inverted U-shaped curve-initially increasing and then declining. The optimal number of nearby samples is 125 (62.5% of the total), and the mean distance between validation and calibration samples is 17 km. Therefore, we conclude that using nearby samples significantly enhances the Cu estimation model. The optimal number of nearby samples should strike a balance, covering a moderate area without there being too few or too many.

Monitoring the Soil Copper of Urban Land with Visible and Near-Infrared Spectroscopy: Comparing Spectral, Compositional, and Spatial Similarities

Heavy metal contamination in urban land has become a serious environmental problem in large cities. Visible and near-infrared spectroscopy (vis-NIR) has emerged as a promising method for monitoring copper (Cu), which is one of the heavy metals. When using vis-NIR spectroscopy, it is crucial to consider sample similarity. However, there is limited research on studying sample similarities and determining their relative importance. In this study, we compared three types of similarities: spectral, compositional, and spatial similarities. We collected 250 topsoil samples (0–20 cm) from Shenzhen City in southwest China and analyzed their vis-NIR spectroscopy data (350–2500 nm). For each type of similarity, we divided the samples into five groups and constructed Cu measurement models. The results showed that compositional similarity exhibited the best performance (Rp2 = 0.92, RPD = 3.57) and significantly outperformed the other two types of similarity. Spatial similarity (Rp2 = 0.73, RPD = 1.88) performed slightly better than spectral similarity (Rp2 = 0.71, RPD = 1.85). Therefore, we concluded that the ranking of the Cu measurement model’s performance was as follows: compositional similarity > spatial similarity > spectral similarity. Furthermore, it is challenging to maintain high levels of similarity across all three aspects simultaneously.

Decoding Phytotoxicity: The Predictive Power of Total Soil Copper Content in Long-Term Pepper Growth in Copper-Polluted Soils

Decoding Phytotoxicity: The Predictive Power of Total Soil Copper Content in Long-Term Pepper Growth in Copper-Polluted Soils

Effective and green in-situ remediation strategies based on TEMPO-nanocellulose/lignin/MIL-100(Fe) hydrogel nanocomposite adsorbent for lead and copper in agricultural soils

Hydrogel adsorbents are promising tools for reducing heavy metals' bioavailability in contaminated soil. However, their practical feasibility remains limited by the low stability, inefficient removal efficiency, and potential secondary pollution. Optimizing the adsorption operation and the functional properties of hydrogel adsorbents could eliminate this method's drawbacks. Herein, three innovative in-situ remediation strategies for Pb/Cu-contaminated soil were adopted based on the concept of novel TEMPO-cellulose (TO-NFCs)/lignin/acrylamide@MIL-100(Fe) nanocomposite hydrogel adsorbent (NCLMH). Characteristic analyses revealed ideal Pb/Cu adsorption mechanisms by swelling, complexation, electrical attraction, and ion exchange via carboxyl/hydroxyl/carbonyl groups and unsaturated Fe(III) sites on ANCMH besides FeOOH formation. The highest maximum theoretical adsorption capacities of Pb(II) and Cu(II) on ANCMH were 416.39 and 133.98 mg/g, under pH 6.5, governed by pseudo-second-order/Freundlich models. Greenhouse pot experiments with contaminated soils amended with two-depth layers of 0.5% NCLMHs (SA@NCLMH) displayed a decline in Pb and Cu bioavailability up to 85.9% and 74.5% within 45 d. Soil column studies simulating continuous water soil flushing coupled with NCLMH layers, instead of conventional extractant fluids, and connected to NCLMH-sand column as purification unit (CF@NCLMH) achieved higher removal rates for Pb, and Cu of 89.5% and 77.2% within 24 h. Alternatively, conducting multiple-pulse soil flushing mode (MF@NCLMH) gained the highest Pb and Cu removal of 96.5% and 85.4%, as the water flushing-stop flux events allowed adequate water movement/residence period, promoting Pb/Cu desorption-adsorption from soil to NCLMH. Also, the NCLMH-sand column conducting and easy separation of the stable/reusable NCLMHs prevented the potential secondary pollution. Interestingly, the three remediated soils reached the corresponding regulation of the permissible limits for Pb and Cu residential scenarios in medium-to-heavily agricultural polluted soils, alleviating the Pb/Cu bioaccumulation and phytotoxicity symptoms in cultivated wheat, especially after MF@NCLMH treatment. This study introduces promising alternative remediation strategies with high sustainability and feasibility in acidic-to-neutral heavy metal-contaminated agricultural soil.

Heavy Metal Accumulation in Soil and Plants Using Municipal Solid Waste Compost in Variable pH Conditions

ABSTRACT Municipal solid waste composts (MSWC) are extensively utilized as organic soil conditioners and fertilizers in agricultural fields across many countries. However, the use of MSWC can lead to heavy metal pollution in soil and plants, which may adversely affect plant growth. This study examined the impact of MSWC on the heavy metal content in plants and soil across various pH levels. The experiment was conducted in a pot setting with three replications. The research findings indicated that MSWC application increased the levels of copper (Cu) and zinc (Zn) in soils but had no significant effect on lead (Pb), nickel (Ni), manganese (Mn), and iron (Fe) levels. Additionally, increases were observed in the Cu, Zn, and Fe content in plants, while Pb and Ni content remained unchanged. Cu, Zn, and Fe are essential for plant growth, and their enhancement in both soil and plants is a direct result of their relatively high presence in the MSWC used. The soil-plant transfer coefficients show that the transfer of heavy metals from soil to plants is highest under acidic conditions, indicating that the heavy metal content in MSWC can vary depending on soil pH and application rate. Therefore, it is crucial to carefully analyze and evaluate the heavy metal contents of soil and compost samples before employing MSWC in agricultural fields.

Effects of exogenous copper on microbial metabolic function and carbon use efficiency of Panax notoginseng planting soil.

Soil copper (Cu) pollution is a serious environmental risk in the Panax notoginseng planting area. However, the effect of Cu on soil microbial metabolism and nutrient cycling in this area remains unknown. Therefore, Biolog ECO-plate and enzyme stoichiometry methods were utilized in this study to investigate the impact of exogenous Cu (control: 0 mg·kg-1; Cu100: 100 mg·kg-1; Cu400: 400 mg·kg-1; and Cu600: 600 mg·kg-1) on the metabolic function of soil microbial and nutrient limitation in the P. notoginseng soil. The results indicated that Cu100 significantly increased soil organic carbon (SOC), total phosphorus (TP), soil C:N, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) 9.89%, 15.65%, 17.91%, 61.87%, and 90.56% higher than the control, respectively. Moreover, the carbon source utilization ratio of carbohydrates, amino acids, and amphiphilic compounds of Cu100 also increased by 7.16%, 25.47%, and 84.68%, respectively, compared with the control. The activities of β-1,4-glucosidase, cellobiohyrolase, leucine amino peptidase, β-1,4-N-acetylglucosaminidase, and phosphatase significantly decreased with increasing Cu concentration. Soil enzyme stoichiometry showed that all treatments were limited by nitrogen (vector angle < 45°; 19.045-22.081). Cu600 led to the lowest carbon limitation (1.798) and highest carbon use efficiency (CUE:0.267). The PLS-SEM model also showed that MBC, MBN, MBP, and microbial diversity positively affected carbon and nitrogen limitation (0.654 and 0.424). Soil carbon, nitrogen, phosphorus, stoichiometric ratio, MBC, MBN, and MBP positively affected CUE (0.527 and 0.589). The microbial diversity index significantly negatively affected CUE (-1.490). Multiple linear stepwise regression analyses showed that CUE was mainly influenced by MBC, AP, C:P, and LAP. Thus, P. notoginseng soil can benefit soil microbial carbon and nitrogen limitations at low Cu concentrations. Clarifying the metabolic activity and nutritional status of microorganisms under Cu stress can provide some theoretical basis for realizing China's comprehensive and effective management and control policies for environmental risks from metals by 2035.

THE IMPACT OF SOIL HEAVY METAL ACCUMULATION ON THE GROWTH OF SUNN HEMP (Crotalaria juncea L.)

Sunn Hemp plants, specifically Crotalaria juncea, are effective in absorbing and reducing the accumulation of heavy metals like cadmium, zinc, lead, and copper in soil. This plant species belongs to the Fabaceae family and is not only important for its phytoremediation capabilities but also for its agricultural value as a fiber and manure crop. Overall, Sunn hemp plants are crucial in mitigating the harmful effects of heavy metal contamination. The experiment was conducted in a greenhouse using a Completed Randomized Design (CRD) with 5 treatments and 6 replications to assess the impact of varying concentrations of heavy metals on Sunn hemp growth. The heavy metals were created by combining Cadmium (Cd), Copper (Cu), Lead (Pb), and Nickel (Ni). Each treatment of heavy metal contamination using 200ml of solution: T0 is the negative control. T1 containing 0.9 (Cd) + 4.0 (Cu) + 0.18 (Pb) + 0.7 (Ni). T2 containing 11.90 (Cd) + 19.80 (Cu) + 36.00 (Pb) + 28.90 (Ni). T3 containing 23.80 (Cd) + 39.60 (Cu) + 72.00 (Pb) + 57.80 (Ni). T4 containing 35.70 (Cd) + 59.40 (Cu) + 108.0 (Pb) + 115.60 (Ni). The study analyzed the impact of heavy metal concentrations on the growth of sunn hemp. Data included soil pH, plant height, flower count, pod count, root and shoot length, fresh and dry weight. Results showed that T4 showed excellent growth performance in terms of height, number of flowers, and dry weight. Sunn hemp has the ability to store heavy metals to a greater extent in its roots and has a remarkable capacity for long-term survival.

Total and Extractable Micronutrients in Tropical Acid Soils of Lampung, Indonesia

ABSTRACT The study aimed to determine the total and available amounts of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in the humid tropical acid soils of Lampung, Indonesia, and to identify the key factors affecting them. Topsoil samples were taken from 10 agricultural fields and 6 natural fields in 16 sub-districts of Lampung, Indonesia. The average total contents of Fe (26.36 g kg−1), Cu (8.97 mg kg−1), and Zn (53.24 mg kg−1) are generally below the world-soil average contents and those in other acid soils, which may be due to eluviation of Fe, Cu, and Zn into subsoil induced by high rainfall and the low natural contents of especially Cu and Zn in the parent rocks (acid volcanic rocks and sandstone). In contrast, the average total Mn content (1.20 g kg−1) is 2 to 8 times higher than that commonly found in acid soils and the world-soil average content, indicating that the parent materials may contain high Mn-bearing minerals. The total Fe, Mn, and Zn are positively correlated to the clay content, exchangeable-Ca and -Mg, and exchangeable-Mg, respectively, whereas the total Cu has no correlation to any soil properties. The amounts of available Fe, Mn, Cu, and Zn account for on average 0.38%, 6.20%, 21.50%, and 4.40% of the total contents, respectively. Around 6%, 12.5%, and 56% of the soil samples exhibit Mn, Cu, and Zn deficiency, respectively, and 25% face Fe toxicity. Total Fe and Mn are the main factors determining available Fe and Mn, respectively, whereas exchangeable-Mg and organic-C content mainly control available Cu and Zn, respectively.