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Currently, reforestation efforts focus primarily on deciduous species replacing coniferous monocultures. Related to this are efforts to identify their interactions in the soil. Root exudation has many functions, including plant communication with soil microorganisms and the solubilisation of nutrients. Root exudates reflect the situation in the soil, as well as refer to the plant species and health/fitness. The idea here was to reveal the typical content of low-molecular-weight phenolic acids in the soil solution that occur in the early-life stages of most typical temperate deciduous trees Quercus robur, Sorbus torminalis, Fagus sylvatica and Acer pseudoplatanus, including the fast-growing invasive Robinia pseudoacacia. To compare their initial strategies and ambient, seedlings were planted in the pot experiment for one season since emergence. The following phenolic acids were detected in detectable concentrations: vanillic, 4-benzoic, syringic, p-coumaric and salicylic. Each tree species tested showed a unique fingerprint in these acids, which can be considered species-specific, i.e., their presence differed among the species. Robinia pseudoacacia (unlike the other trees tested) showed the ability to maintain high levels of p-coumaric acid in the soil solution, indicating its potential to survive in nutrient-poor soil and achieve rapid growth. On the contrary, the levels of all phenolic acids detected in the soil solution of Quercus robur and Sorbus torminalis were very low. These fingerprints should be extended to other compounds and also to older trees. [ABSTRACT FROM AUTHOR]

Agricultural activities contribute significantly to the pollution of groundwater through the incomplete absorption of nitrogen (N) and phosphorus (P). Understanding the vertical migration patterns of N and P in soil solution is crucial for controlling groundwater quality. This study is based on monitoring data of soil solution nitrogen and phosphorus at different depths (30 cm, 60 cm, 100 cm) in the Huixian Wetland Experimental Area in the Li River Basin from March to December 2021. The vertical distribution patterns of nitrogen and phosphorus in soil solution in the study area are elucidated from three aspects: seasonal variations, karst types, and land use. The results indicate that the following: (1) NO3−-N is the predominant form of nitrogen, generally decreasing with increasing soil depth, while NH4+-N concentrations show slight increases and TP concentrations remain relatively stable. Overall, NO3−-N and TN concentrations tend to accumulate at 30 cm and 60 cm depths during both irrigation and non-irrigation seasons, with no distinct distribution patterns observed for NH4+-N and TP. (2) During the irrigation season, the migration distance of NO3−-N in non-karst landforms is mainly at 60 cm, while in peak forest plains, it is mainly at 100 cm, with no clear trend observed in NO3−-N concentrations in peak cluster depressions. In non-irrigation seasons, the distribution of NO3−-N content in non-karst landforms and peak cluster depressions is mainly 30 cm > 60 cm > 100 cm. The downward migration distance of NH4+-N generally follows the order of peak cluster depressions > peak forest plains > non-karst landforms. (3) During the irrigation season, NO3−-N concentrations in paddy fields remain relatively high at 100 cm, while in drylands, NO3−-N concentrations generally follow the pattern of 30 cm > 60 cm > 100 cm but may exhibit anomalous increases or decreases at 60 cm and 100 cm depths during heavy rainfall. [ABSTRACT FROM AUTHOR]

The efficient separation of solid and liquid phases of soil under reductive conditions is of the utmost importance to study soil chemistry and to predict the mobility and bioavailability of nutrients and toxic contaminants in waterlogged reduced soils (WRSs). However, there is no established method for efficiently separating the solid and liquid phases of WRS within a short time while maintaining its reductive conditions. This study aimed to verify the applicability of a simple centrifugal filtration method (CFM) for the efficient separation of solid and liquid phases of a WRS and examine the CFM-extracted soil solution to confirm that the reductive condition was maintained during the solid–liquid separation process. Incubation experiments were performed under reductive conditions with or without ethanol/molasses used as additional organic material (OM), while the soil solution was collected by both a suction method and CFM at different centrifugation speeds (700, 2760, and 11,000 rpm) and times (1–7 min). The results showed that the soil pH increased with time while the Eh decreased, indicating that its reducing state was enhanced during the incubation experiments. The addition of OM promoted the reductive conditions in the first days of the experiments. Centrifugation speed, rather than time, was found to be the key to extract the maximum amount of soil solution, while a higher centrifugation speed (11,000 rpm), which represents the permanent wilting point, was found to be most effective for extracting the maximum amount of soil solution. The results exhibited no significant difference in solute (As, Fe(II), and Mn) concentrations when varying amounts of CFM-extracted soil solution were measured. The statistical analysis also indicated no significant (p > 0.05) difference between the solute concentrations in the CFM-extracted soil solution and the solute concentrations in the soil solution extracted by the suction method, confirming that the reductive condition was maintained during solid–liquid separation by CFM. This study suggests that CFM operating at a higher centrifugation speed could potentially be employed as a simple and highly effective technique to efficiently separate the solid and liquid phases of WRS (sandy clay loam) within a short time while maintaining its reductive conditions. [ABSTRACT FROM AUTHOR]

Abstract Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation. [ABSTRACT FROM AUTHOR]

Agricultural activities contribute significantly to the pollution of groundwater through the incomplete absorption of nitrogen (N) and phosphorus (P). Understanding the vertical migration patterns of N and P in soil solution is crucial for controlling groundwater quality. This study is based on monitoring data of soil solution nitrogen and phosphorus at different depths (30 cm, 60 cm, 100 cm) in the Huixian Wetland Experimental Area in the Li River Basin from March to December 2021. The vertical distribution patterns of nitrogen and phosphorus in soil solution in the study area are elucidated from three aspects: seasonal variations, karst types, and land use. The results indicate that the following: (1) NO3−-N is the predominant form of nitrogen, generally decreasing with increasing soil depth, while NH4+-N concentrations show slight increases and TP concentrations remain relatively stable. Overall, NO3−-N and TN concentrations tend to accumulate at 30 cm and 60 cm depths during both irrigation and non-irrigation seasons, with no distinct distribution patterns observed for NH4+-N and TP. (2) During the irrigation season, the migration distance of NO3−-N in non-karst landforms is mainly at 60 cm, while in peak forest plains, it is mainly at 100 cm, with no clear trend observed in NO3−-N concentrations in peak cluster depressions. In non-irrigation seasons, the distribution of NO3−-N content in non-karst landforms and peak cluster depressions is mainly 30 cm > 60 cm > 100 cm. The downward migration distance of NH4+-N generally follows the order of peak cluster depressions > peak forest plains > non-karst landforms. (3) During the irrigation season, NO3−-N concentrations in paddy fields remain relatively high at 100 cm, while in drylands, NO3−-N concentrations generally follow the pattern of 30 cm > 60 cm > 100 cm but may exhibit anomalous increases or decreases at 60 cm and 100 cm depths during heavy rainfall.

The efficient separation of solid and liquid phases of soil under reductive conditions is of the utmost importance to study soil chemistry and to predict the mobility and bioavailability of nutrients and toxic contaminants in waterlogged reduced soils (WRSs). However, there is no established method for efficiently separating the solid and liquid phases of WRS within a short time while maintaining its reductive conditions. This study aimed to verify the applicability of a simple centrifugal filtration method (CFM) for the efficient separation of solid and liquid phases of a WRS and examine the CFM-extracted soil solution to confirm that the reductive condition was maintained during the solid–liquid separation process. Incubation experiments were performed under reductive conditions with or without ethanol/molasses used as additional organic material (OM), while the soil solution was collected by both a suction method and CFM at different centrifugation speeds (700, 2760, and 11,000 rpm) and times (1–7 min). The results showed that the soil pH increased with time while the Eh decreased, indicating that its reducing state was enhanced during the incubation experiments. The addition of OM promoted the reductive conditions in the first days of the experiments. Centrifugation speed, rather than time, was found to be the key to extract the maximum amount of soil solution, while a higher centrifugation speed (11,000 rpm), which represents the permanent wilting point, was found to be most effective for extracting the maximum amount of soil solution. The results exhibited no significant difference in solute (As, Fe(II), and Mn) concentrations when varying amounts of CFM-extracted soil solution were measured. The statistical analysis also indicated no significant (p > 0.05) difference between the solute concentrations in the CFM-extracted soil solution and the solute concentrations in the soil solution extracted by the suction method, confirming that the reductive condition was maintained during solid–liquid separation by CFM. This study suggests that CFM operating at a higher centrifugation speed could potentially be employed as a simple and highly effective technique to efficiently separate the solid and liquid phases of WRS (sandy clay loam) within a short time while maintaining its reductive conditions.

Increasing salinization of groundwater used for irrigation is a current and growing problem for vegetable production in greenhouses in the Mediterranean Basin. Vegetable growers in this system require clear information of crop response to salinity, particularly of threshold values. For sweet pepper in Mediterranean greenhouses, this work (i) evaluated the effect of increasing salinity on various parameters of crop yield, fruit quality and plant water relations, and (ii) determined threshold and slope values for the Maas and Hoffman (M&H) model. Sweet pepper was grown with nutrient solutions (ns) with electrical conductivities (EC) of 2.5 (T1), 3.5 (T2), 4.5 (T3), 5.5 (T4), 6.5 (T5) and 7.5 (T6) dS m−1. There were substantial and statistically significant reductions in total and marketable yield, dry matter production (DMP) and average fruit weight, with increasing salinity. In treatment T4 (ns of 5.5 dS m−1), the respective reductions for these parameters, compared to T1 (ns of 2.5 dS m−1), were 37%, 37%, 47%, 52% and 30%. Applying the M&H model, soil solution EC threshold (ECsst) values for total and marketable yield were 4.8 and 5.0 dS m−1. The respective slope values were − 8.0 and − 12.0%/dS m−1. The more rapid decline in marketable yield was influenced by a large increase in the incidence of blossom end rot (BER) with increasing salinity. In treatment T1, 25% of discarded fruit had BER which increased to 70% in T6. Average fruit size was affected by salinity, but fruit number was not. Most fruit quality parameters were unaffected by increasing salinity. However, fruits were more red and more yellow. Leaf water potential (ΨW), leaf osmotic potential (ΨO), stomatal conductance (gS) and leaf turgor potential (ΨP) followed the Maas and Hoffman model, with ΨW, ΨO and gS declining and ΨP increasing after the EC threshold value. The ECsst value for ΨW was 5.0 dS m−1, and for ΨO, gS and ΨP was 5.6–5.8 dS m−1. Considering all data, an ECsst value of 5.0 dS m−1 is suggested for sweet pepper grown in Mediterranean greenhouses.

We validated a simulation model (PostPLANT-Soil) for predicting pesticide concentrations in succeeding leafy vegetables reported in our first paper in this series, which includes the pesticide sorption process into plant roots. As a result of the model validation with the measured data from a plant uptake study in a growth chamber, the model successfully simulated the concentration changes of pesticides in a plant shoot. However, the simulated shoot concentrations for several pesticides were overestimated compared to the measured values. The leafy vegetable (Brassica rapa) used in this study probably has a high metabolic ability for the fungicide flutolanil from the result of the uptake study under a hydroponic condition. [ABSTRACT FROM AUTHOR]

Soil selenium (Se) speciation characteristics and their influence on the Se enrichment pattern and physiological characteristics of oilseed rape are poorly understood. We investigated dynamic changes in rhizosphere soil physicochemical properties, Se uptake and partitioning, biomass, and physiological indices in oilseed rape under five exogenous Se condition levels (0, 1.0, 2.5, 5.0, and 10.0 mg kg−1 Se in sodium selenite) using soil cultivation experiments. The rhizosphere pH and dissolved organic carbon in the soil solution were higher than those of the non-rhizosphere soil solution. The total Se, water-soluble Se, exchangeable Se, and organic Se contents in soils, as well as rapeseed root/leaf Se contents, significantly increased with increasing exogenous Se. Under 2.5 mg kg−1 Se, the biomass of rapeseed roots and leaves increased at the sixth week (82% and 58%) and eighth week (48% and 32%), respectively, reaching the highest level. Applications of 5.0 mg kg−1 Se at 6 and 8 weeks significantly increased the glutathione peroxidase activity (49%/82%), and decreased malondialdehyde content (23%/39%). Canonical correlation and ridge regression analyses showed that Se in the rapeseed roots/leaves significantly and positively correlated with water-soluble Se, exchangeable Se, and organic Se in rhizosphere soil. Overall, moderate-concentration Se soil application benefited oilseed rape growth (optimum = 2.5 mg kg−1 Se). Our findings reveal the response of oilseed rape to soil Se application based on plant growth and physiological traits, rhizospheric soil solution properties, and Se speciation transformation. [ABSTRACT FROM AUTHOR]

Understanding trace element (TE) composition and behavior in soil solution is extremely important for assessing ecological and human health impacts. Using lysimeters to collect soil solution with minimum alteration to the in situ phase distribution and concentration of TEs will facilitate a more accurate assessment. However, different lysimeter materials and sampling conditions may lead to vastly different results, demonstrating the need for the optimal choice of lysimeter depending upon environmental conditions. There is no general agreement or overview discussing the best lysimeter type and sampling system to use under various conditions. This review provides a critical summary of various lysimeters that can be used to collect soil solutions for the analysis of TEs and thereby provides key guidance for developing the best lysimeter sampling system for conditions and research questions of interest. This includes a range of aspects related to lysimeters, such as different types and materials, the basic principles of design and operation, advantages and disadvantages, challenges and limitations, techniques for cleaning and pretreatment, correct installation procedures, the influence of soil physical and chemical properties on sampling, and existing research gaps within this field. [ABSTRACT FROM AUTHOR]

Background: Evidence of trivalent manganese (Mn3+) in the aqueous phase of soils is unknown so far although this strong oxidant has large environmental implications. Aims: We aimed to modify a spectrophotometric protocol (porphyrin method) and to discriminate between Mn2+ and Mn3+ in the aqueous phase of forest soils based on kinetic modeling. Methods: We investigated manganese speciation in 12 forest floor solutions and 41 soil solutions from an acidic forest site by adjusting pH and correcting for absorbance. Results: The solutions showed broad ranges in pH (3.4−6.3), dissolved organic carbon (DOC, 1.78−77.1 mg C L−1), and total Mn (MnT, 23.9−908 µg L−1). For acidic solutions, a pH‐buffer was added to increase the pH of the solutions to 7.5−8.0, and background absorption was corrected for colored solutions, that is, solutions high in DOC. This was done to accelerate the reaction kinetics and avoid overestimation of MnT concentrations. After the pH and color adjustments, the comparison of MnT concentrations between the porphyrin method and optical emission spectrometry showed good agreement. Trivalent Mn, which is stabilized by organic ligands, constitutes significant proportions in both forest floor solutions (10−87%) and soil solutions (0.5−74%). Conclusions: The dissolved Mn3+ is present in acidic forest soils. Thus, we revise the paradigm that this species is not stable and encourage to apply the revised method to other soils. [ABSTRACT FROM AUTHOR]

The aim is to examine the nutrient ion dynamics in a Vertisol soil undergoing waterlogging to ascertain whether soil solution concentration and/or nutrient uptake dynamics are the cause of boll shedding in cotton. Cotton was grown in pots, and the soil waterlogged after 76 days at which time injections of 33P and 86Rb were made to trace phosphorus (P) and potassium (K) dynamics. After seven days, waterlogging in the pots were drained and an injection of 32P was made to trace P dynamics during the recovery period. Redox fell rapidly during waterlogging, and soil solution concentrations of P, K, sodium (Na), and manganese (Mn) increased. Biomass accumulation was less in the waterlogged treatment than in the non-waterlogged control. In the 7-day recovery period, shoot biomass increased in the waterlogged treatment and root biomass weight continued to decline. Recovery of 33P was 10 times higher in the control than in the waterlogged treatment during the 7-day waterlogging period treatment. Uptake of 86Rb in the control treatment was more than twice that of the waterlogged treatment during this period. Uptake of both33P and 86Rb increased during recovery but remained higher in the control treatment. Uptake of 32P occurred during post-waterlogging but remained higher in the control treatment. Reduced uptake of P and K during waterlogging is most likely due to damage to the uptake mechanisms of the roots rather than a reduction in the concentration of nutrients in the soil solution under waterlogged conditions. [ABSTRACT FROM AUTHOR]

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Nutrient status of plant affects root exudates of plant. Little is known about effect of potassium status on root exudation. Objective of this study was to identify metabolites in rhizosphere soil of soybean under different potassium conditions. Two soybean cultivars (Satonohohoemi (SAT) and Tachinagaha (TAC)) were grown in soil culture under low (K0, without potassium fertilizer) and normal (K2, 0.42 g K kg−1) soil potassium status. Soil solutions were collected at 15 and 25 DAS. Metabolites in soil solution were detected by CE-TOF MS. Low potassium tolerance was higher in SAT than TAC. Shoot and root K concentration in SAT was lower in K0 than that in K2. Forty-seven metabolites were detected in rhizosphere soil solution of SAT, TAC and without plant. Low K condition increased 6 and 3 metabolites concentration in soil solution without plant and 2 and 4 metabolites concentration with SAT and 2 and 1 metabolites concentration with TAC, at 15 and 25 DAS, respectively. Low K condition decreased 1 and 1 metabolites concentration in soil solution without plant and 6 and 6 metabolites concentration with SAT and 0 and 2 metabolites concentration with TAC, at 15 and 25 DAS, respectively. Increased and decreased metabolites were different between SAT and TAC. These results suggest that K status affect metabolites in root exudate and rhizosphere microbes of soybean and there is cultivar difference in these metabolites. [ABSTRACT FROM AUTHOR]

Flexible screen-printed electrodes (SPE) were modified in a simple manner with different composite nanomaterials based on carbon allotropes, polymers, and metallic nanoparticles, for amperometric detection of nitrites in soil. Multiwalled carbon nanotubes (MWCNT), chitosan (CS), silver nanoparticles (AgNPs), 1,8-diaminonaphthalene (1,8-DAN), and a sol-gel (SG) matrix were used for modification of the carbon paste working electrodes. Sensitive and selective detection of nitrite was achieved by using a MWCNT-CS-modified sensor, in acetate buffer at pH 5, at an applied potential of 0.58 V vs. Ag/AgCl. The MWCNT-CS-based sensor displayed a specific sensitivity of 204.4 mA·M−1·cm−2, with a detection limit of 2.3 µM (S/N = 3) in a linear range up to 1.7 mM, showing good stability, reproducibility, and selectivity towards other interfering species. A miniaturized portable system using the developed flexible electrochemical MWCNT-CS-based sensors was dedicated for the detection of nitrite in different samples of soil solutions extracted by using suction lysimeters. [ABSTRACT FROM AUTHOR]

Purpose: The objectives of this study were to (1) analyze heavy metals (Cr, As, Cu, Zn, Cd, and Pb) in the rhizosphere soil and roots, leaves, stems, and grains of maize and wheat crops using different methods; (2) evaluate the advantages of diffusive gradients in thin films technology (DGT) for predicting the bioavailability of heavy metals; and (3) compare the characteristics of DGT with other methods. Materials and Methods: In this study, we collected maize and wheat samples and their rhizosphere soil over a pollution gradient in Kaifeng City, China. Six heavy metal (Cr, As, Cu, Zn, Cd, and Pb) levels in rhizosphere soil were determined using DGT, EDTA, soil solution, and total amount methods, respectively. The heavy metal content in the roots, leaves, stems, and grains of maize and wheat was also analyzed. The relationships between six heavy metal soils concentrations detected by different methods, and their contents in the different parts of wheat and maize, were analyzed using statistical methods. The characteristics and application scope of the different methods were evaluated. Results and Discussion: The accumulation of heavy metals in maize and wheat was generally higher in the roots than in the above-ground parts (i.e., stems, leaves, and grains). For the soil solution method, only soil As levels showed a significantly positive correlation with its content in different parts of wheat and corn. For the EDTA method and the soil total amount method, only As, Zn, and Pb levels were significantly correlated with their contents in different parts of wheat and corn. Six heavy metal concentrations detected by DGT were all significantly positively correlated with their contents in the different parts of wheat and maize. Furthermore, DGT was less affected by the soil pH than EDTA. Conclusions: DGT was more accurate in simultaneously predicting plant-available Cr, As, Cu, Zn, Cd, and Pb. However, other methods, like EDTA, soil solution, and total amount methods, can also be considered when predicting the bioavailability of a single heavy metal (e.g., As or Zn) in rhizosphere soil. [ABSTRACT FROM AUTHOR]

The agronomic efficiency of biochar-based fertilizers (BBFs) relies on the synthesis routes, properties, and interaction with the soil–plant system. In our study, BBFs were produced from coffee husk, low-grade acidulated phosphate rock with and without the addition of magnesium (Mg). BBFs were characterized for infrared analysis and the kinetics of phosphorus (P) release in water or citric acid (CA). The agronomic performance of BBFs was tested by growing maize and, in sequence, brachiaria grass in pots filled with two Oxisols with contrasting soil organic matter (SOM) content. Using the same chemical stoichiometric ratio, nitric acid was more effective than hydrochloric and sulfuric acids, creating BBFs with enhanced agronomic performance. The use of Mg in the BBFs synthesis reduced the P released in water. Phosphorus released in CA leachates positively correlated with the P in the shoot of both plants. BBFs produced using nitric acid had higher residual effect on brachiaria grass grown in the Oxisol with the highest SOM. Our outcomes show that the P rate for maize and brachiaria grass should be considered based on P soluble in neutral ammonium citrate plus water in BBFs. BBFs is an alternative to improve the use efficiency of P in Oxisols. [ABSTRACT FROM AUTHOR]

The practical value of portable hand-held ion selective electrode sensors (ISE) for on-farm [NO3−] measurement to assist with crop N management of vegetable crops has been demonstrated in numerous previous studies. They provide rapid, in-situ measurement of the nitrate concentration ([NO3−]) in nutrient and soil solutions, and in petiole sap. Sample temperatures, for on-farm measurements, vary appreciably. This study evaluated the effects of sample temperature on [NO3−] measurement using two different models of a commonly used, commercially available, portable ISE meter. The temperatures (5, 10, 15, 20, and 25 °C) examined were in the range likely to be encountered in practical on-farm work. Aqueous solutions of 6, 12, and 18 mmol NO3− L−1 were prepared from KNO3, Ca(NO3)2 and NaNO3. [NO3−] was measured in three replicate samples of each of the three concentrations, made from each NO3− compound, at each temperature. The results consistently and clearly demonstrated a strong negative linear relationship between temperature-induced errors and sample temperatures. The temperature-induced error was considerable for cooled samples, being +50% at 5 °C and +31% at 10 °C. At sample temperatures of 17–20 °C, the temperature effects were minimal. Above this range, the temperature effect caused underestimation. At 25 °C, the temperature-induced error was −24%. These results show that care must be taken to ensure that sample temperatures do not erroneously affect the measurement of [NO3−] with ISE meters. Particular care needs to be taken with both refrigerated and warmer samples. [ABSTRACT FROM AUTHOR]

Transfer of trace elements, such as toxic metals, from soil to plant is a corner stone for risk assessment. Rare earth elements (REE) are frequently used as environmental tracers to understand biogeochemical processes in the soil–plant system. In this study, we combined trace element and REE measurements in the soil–plant continuum to evaluate the element transfer between different compartments. We specifically aimed at: (1) assessing the geochemical relevance and representativeness of intermediate compartments (soil solution and soil water-extract as a proxy of the bioavailable soil fraction) by comparing the REE normalized patterns; and (2) characterizing the environmental conditions that control the trace element transfer by quantifying the REE indices. For that purpose, we compared geochemical signatures in an intercropping cover crop (bean, Persian clover, and spelt) in Belgium, including soil, root, shoot, soil solution, soil water-extract, earthworm, and snow samples. Evaluation of the element mobility was performed using both soil extractability and transfer factors. The main result showed dissimilar REE patterns between soil/plant samples and soil solution/soil water-extract samples, indicating that the intermediate compartments (i.e., soil solutions or soil water-extracts) do not chemically represent the bioavailable fraction of elements without obvious propensity to biological accumulation (unlike Cd, Cu, or Zn). Compared to light REE, heavy REE were more extractable and thus transferred to plants unlike what is observed in the literature. According to their different extractabilities, Ce and Eu allowed to highlight distinct transfer from soil to plant due to possible adsorption or organic matter complexation that should be further confirmed by studying contrasted soils. [ABSTRACT FROM AUTHOR]

This article provides an overview of the results of long-term studies of the migration of radionuclides in the composition of lysimetric waters (leachates). It considers peculiarities of lysimeter-based studies at various stages of advancement in radioecology. It is noted that, for a long time, the use of lysimeters was limited to a low level of radionuclides in soil solutions; the studies gained momentum after the Chernobyl deposition (1986). Release of radionuclides to leachates is shown to be the greatest in the forest and coniferous phytocenoses, in particular, and the least in meadows and agrophytocenoses. The intensity of radionuclide migration in the leachates is the maximum during the initial period after atmospheric deposition in the long-term dynamics and during summer in the seasonal dynamics. Gravity flow was assessed in redistribution of radionuclides across the soil profile. The annual flux with vertical subsurface flow varies depending on edaphic and climatic conditions; time elapsed after the deposition; and thickness and depth of the layer. The annual flux ranges from tenths of a percent to a low percentage of the forest floor and from hundredths to tenths of a percent from a 0- to 20-cm layer of the total radionuclide inventory in these layers. The relative flux of 90Sr significantly surpasses that of 137Cs. From 70 to 90% of radionuclides (90Sr, 137Сs, 238Pu, 239+240Pu, and 241Am) are present in soil solution in the form of radionuclide–organic compounds of various molecular weights. [ABSTRACT FROM AUTHOR]

• The Caspian Sea retreat strongly affected the geochemistry of soils. • The properties of geomorphic surfaces play important roles in soil formation. • Distribution patterns of soil characteristics are strongly affected by landforms and seawater. The objectives of this study are: 1- Determining geochemical characteristics and soil formation processes that lead to soil salinity. 2- To investigate the variability of soil properties across different geomorphic units. The coastal landforms of the Caspian Sea have experienced several seawater retreat and progress in recent decades, which has caused changes in terms of pedology and geomorphology. Routine soil properties, including soil cations and anions (Ca2+, Mg2+, Na+, K+, Cl-, SO 4 2-, CO 3 2–, and HCO 3 –), and total and available forms of some micro-elements (Fe, Mn, Zn, and Cu) of 136 samples collected from 0-20 cm of soils were analyzed according to standard methods. Mapping of the obtained results was done using inverse distance weighting (IDW) in ArcGIS 10.8. The results showed that although the main source of cations and anions in the soil solution is seawater, their concentration and changes in the soil solution are different depending on the processes carried out in soil. Mg2+, Na+, and Cl- were highly enriched in saturated soil extracts compared to seawater (261 %, 153 %, and 149 % respectively). While, K+ and Ca2+, increased by 81 % and 47 % accordingly, and HCO 3 – and SO 4 2-, decreased by −56 % and −25 % due to precipitation of carbonate and gypsum in the soil. Total and available forms of micro-nutrients were high across the study area. The distribution pattern of the total micro-nutrients follows the type of landforms (affecting drainage condition) and their clay contents (mineralogical composition and abundance), however, the available form of micro-nutrients depends on soil moisture conditions and proximity or distance to the coastline. The results showed that the chemistry of seawater is the main factor controlling the chemical and physical properties of soils and their distribution patterns. The geochemical processes of soil formation cause special interactions between the components of soil solution, which leads to the removal of carbonate, bicarbonate, and sulfate from the soil solution and precipitation with calcium as calcium carbonate and calcium sulfate. [ABSTRACT FROM AUTHOR]

Soil selenium (Se) speciation characteristics and their influence on the Se enrichment pattern and physiological characteristics of oilseed rape are poorly understood. We investigated dynamic changes in rhizosphere soil physicochemical properties, Se uptake and partitioning, biomass, and physiological indices in oilseed rape under five exogenous Se condition levels (0, 1.0, 2.5, 5.0, and 10.0 mg kg−1 Se in sodium selenite) using soil cultivation experiments. The rhizosphere pH and dissolved organic carbon in the soil solution were higher than those of the non-rhizosphere soil solution. The total Se, water-soluble Se, exchangeable Se, and organic Se contents in soils, as well as rapeseed root/leaf Se contents, significantly increased with increasing exogenous Se. Under 2.5 mg kg−1 Se, the biomass of rapeseed roots and leaves increased at the sixth week (82% and 58%) and eighth week (48% and 32%), respectively, reaching the highest level. Applications of 5.0 mg kg−1 Se at 6 and 8 weeks significantly increased the glutathione peroxidase activity (49%/82%), and decreased malondialdehyde content (23%/39%). Canonical correlation and ridge regression analyses showed that Se in the rapeseed roots/leaves significantly and positively correlated with water-soluble Se, exchangeable Se, and organic Se in rhizosphere soil. Overall, moderate-concentration Se soil application benefited oilseed rape growth (optimum = 2.5 mg kg−1 Se). Our findings reveal the response of oilseed rape to soil Se application based on plant growth and physiological traits, rhizospheric soil solution properties, and Se speciation transformation.

Understanding trace element (TE) composition and behavior in soil solution is extremely important for assessing ecological and human health impacts. Using lysimeters to collect soil solution with minimum alteration to the in situ phase distribution and concentration of TEs will facilitate a more accurate assessment. However, different lysimeter materials and sampling conditions may lead to vastly different results, demonstrating the need for the optimal choice of lysimeter depending upon environmental conditions. There is no general agreement or overview discussing the best lysimeter type and sampling system to use under various conditions. This review provides a critical summary of various lysimeters that can be used to collect soil solutions for the analysis of TEs and thereby provides key guidance for developing the best lysimeter sampling system for conditions and research questions of interest. This includes a range of aspects related to lysimeters, such as different types and materials, the basic principles of design and operation, advantages and disadvantages, challenges and limitations, techniques for cleaning and pretreatment, correct installation procedures, the influence of soil physical and chemical properties on sampling, and existing research gaps within this field.

ABSTRACT Lisianthus (Eustoma grandiflorum) has been attracting great interest due to the beauty of the colors of flowers, the firmness of stems, and postharvest durability. However, knowledge of lisianthus irrigation and fertigation has generally been based on recommendations from other countries. This study aimed to establish parameters for the rational management of lisianthus fertigation under a protected environment by determining the best lower limit of soil moisture, associated with the determination of the optimal potassium concentration to be maintained in the soil solution. The treatments consisted of five soil moisture limits for the start of irrigation and maintenance of five potassium concentrations in the soil solution, with four replications. Plots of 0.7 by 0.5 m were arranged in a completely randomized block design in a factorial scheme. The soil solution was monitored by measuring moisture as well as potassium (K+) concentrations using a TDR100 reflectometer and solution extractors, respectively, during two cycles. The evaluated variables were the leaf area index, shoot fresh and dry matter, commercial yield, and average stem diameter. Lisianthus cultivation under the lower limit of soil moisture equal to 0.20 cm3 cm−3 ensured the best results for all variables of commercial interest. No effect of potassium concentrations was observed on variables of commercial interest.

Purpose: Douglas-fir occupies a growing role in the European timber industries but its effects on soils and the environment are still not well understood. We monitored the biogeochemical cycle of major elements in 11 representative mature stands throughout France over the 2013 to 2020 period to better understand repercussions on soil processes. Methods: The present study is focused on throughfall and soil solution chemistry: concentrations were measured monthly at 15 cm and 60 cm depth and fluxes of major anions and cations were computed. Results: Our results show that nitrate strongly dominated the soil solution chemistry: concentrations were elevated (>20 mg L−1) for 8 out of 11 sites with mean annual NO3− values ranging from 2 to 253 mg L−1. Fluxes of nitrate at 60 cm of depth, ranging from 23 to 309 kg ha−1 yr−1, were much higher than those in throughfall for nine studied sites. Nitrate, which was the dominant anion in soil solution, associated either to Ca2+, Mg2+ and K+, or to Al3+ was lost out of the soil-plant system through leaching. Conclusions: These results suggest a production of NO3− in the soil exceeding tree uptake and microbial immobilization resulting in strong ongoing soil acidification at many sites and potential degradation of water quality. Significant negative correlations were found between nitrate concentration in soil solution and sandy texture, soil C and N, site elevation and, annual rainfall, but further research is necessary to clarify the role of these factors in reducing the negative impacts on terrestrial and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Iron (Fe) colloids dominate the soil solution Fe and these colloids potentially act as vectors for nutrients and contaminants in soil. The question remains which factors, that is, gradients in soil chemical characteristics with depth or physical processes, cause vertical mobilisation and immobilisation of Fe colloids in soils. This question was addressed by characterising the change in concentration, size and composition of Fe colloids in a podzol profile and by relating these changes to soil properties along the profile. Pore waters were analysed with Flow Field Flow Fractionation (FlFFF‐UV‐ICP‐MS) to overcome the artefacts typically obtained when using filtration for fractionation. Pore water was obtained by centrifugation of field moist samples taken from an Albic Podzol. The samples were taken within a depth of 110 cm, at eight depths corresponding to different horizons. The pore water Fe concentration increased with depth and peaked at 66 μM in the E horizon just above the Bh horizon, beyond which, it sharply decreased to only 9 μM. The pore water Fe concentration correlated strongly with dissolved organic carbon (DOC). The high‐resolution size fractionation analysis with FlFFF suggested that the Fe colloids (<100 nm) in the pore water not only consisted of Fe‐organic carbon (OC) complexes, but also of mineral Fe colloids associated with organic matter (OM), as indicated by the colloid size (>5 nm) and by the relatively large Fe/OC ratio that exceeds the complexation capacity of natural OM. The smallest mineral Fe colloids dominated in the Ah1 horizon, while the larger mineral colloids increased with increasing depth, explaining the rise in total Fe towards the Bh horizon. This suggests that Fe complexation with OM and stabilisation of mineral Fe colloids with OM explain colloidal Fe in the pore water. The adsorption of the OM at the top of the Bs horizons is likely the primary mechanism of DOC retention in the Bh horizon. Below this depth, the concentration of DOC was very low, resulting in low Fe concentration in the pore water. The colloids (<100 nm) are considerably smaller than the soil pore size distribution and increase in size with depth, which suggests that straining was not a significant mechanism for colloid retention. This study demonstrates that OM plays a key role in the transport of Fe colloids in acid sandy soil. Highlights: Depth profile of pore water Fe in a podzol is studied to investigate colloid migration processesPore water colloids are characterised by Flow Field Flow FractionationFe colloids consist of complexes with OM and mainly larger mineral colloidsNatural OM plays a key role in the transport of Fe colloids in acid sandy soil [ABSTRACT FROM AUTHOR]

【Background and objective】 Concentration of mobile phosphorus (P) in soil affects not only plant growth but also water quality because of its potential leaching. Most studies on soil P focused on topsoil while overlooking subsoil which is equally important. The objective of this paper is to study the dynamics of mobile P at different soil depths and its driving forces in attempts to help improve P uptake by plants while in the meantime reducing its leaching. 【Method】 Column experiments filled with soil taken from Sanjiang plain in China were conducted with average volumetric soil water content controlled at 50% (M1), 75% (M2) and 100% (M3) respectively. In each treatment, we measured the changes in mobile phosphorus in the depths of 0~10 cm (topsoil) 10~20 cm (middle soil) and 20~30 cm (subsoil). We also analyzed its relationship with total organic carbon (TOC), total Fe, total Al and total Ca in soil solution; the experiments lasted 84 days. 【Result】 When soil water content was 50%, soil solution was not extractable from the topsoil and the middle soil, and only was limited water extracted from the subsoil. When soil water content exceeded 75%, soil solution was more mobile for extraction in which the P concentration in the middle soil was found to be the highest, 1.3~1.7 times that in the topsoil and 5.2~8.2 times that in the subsoil. The impact of soil water on P concentration varied with soil depth and was ranked in the following order: In the topsoil, M3 (1.27 mg/L) > M2 (0.82 mg/L), in the middle soil M3 (1.60 mg/L) > M2 (1.40 mg/L), and in the subsoil M3 (0.31 mg/L) > M2 (0.17 mg/L) >M1 (0.13 mg/L). A stepwise regression analysis indicated that P concentration in the soil solution was related to TOC, total Fe, total Al, and total Ca in soil solution, with the correlations varying with soil water and soil depth. These suggested that improving soil water management could shift dissolution and/or decomposition of P in different forms in the soil, and can thus bed used to manage soil P. Regardless of soil water content, P concentration in the soil was much higher than the critical P concentration, 0.1 mg/L, which could trigger eutrophication in surface water. 【Conclusion】 Increasing soil water could result in a quick release of P from soil to the overlying surface water, triggering eutrophication as a result. Care thus must be taken when temporally returning dry farmland to wetland.

The objective of the present work was to study the soil solution throughout time in pots under greenhouse conditions. The work consisted of monitoring the solution of calcareous soil and forest soil in the absence of plants, with different types of fertilization: treatment 1: absolute control (irrigation water); treatment 2: Steiner nutrient solution; treatment 3: solid fertilizers; and treatment 4: vermicompost tea (aqueous extract). The samples were collected weekly using lysimeters for 14 weeks. They were analyzed to determine the nitrate content, total nitrogen, calcium, potassium, magnesium, sodium, sulfur, zinc, boron, pH, electrical conductivity, and oxide-reduction potential. To understand the interactions between treatments, soil type, and time over ion behavior and availability, linear and polynomial models were used, selected by a cross-validation method, which resulted in robust models, where it was found that the pH behavior is associated with the type of fertilization and soil type, with the elapsed time being a nonsignificant factor. On the other hand, time influenced the dynamics of the remaining ions and their availability. It was found that the multiple polynomial model fit better for the variables: potassium, calcium, sodium (square degree), electrical conductivity, nitrates, sulfur (cubic degree), zinc, oxidation-reduction potential, nitrogen, magnesium, and boron (quartic degree). [ABSTRACT FROM AUTHOR]

The paper presents data on the chemical composition of lysimetric waters of the northern part of the Valday Hills and on natural geochemical and anthropogenic factors that control the composition of the lysimetric water. The influence of the type of elementary landscape and soil characteristics (mineral, granulometric, and chemical composition) on the formation of soil water on a seasonal basis is considered. Features of the accumulation and transport of elements during the passage of atmospheric precipitation through the soil horizon are estimated. Statistical methods are applied to identify factors that determine the migration activity of elements during different seasons of the year, and the effects of soil mineral composition, biogeochemical processes, and anthropogenic precipitation on the chemical composition of water in the aeration zone are estimated. [ABSTRACT FROM AUTHOR]

This study aimed to establish ecotoxicologically acceptable Cu concentrations for soil-residing species by integrating the biotic ligand model and the species sensitivity distribution. Statistical analyses were performed on 35 soil solution samples collected from four distinct land use sites: residential, agricultural, forested, and industrial regions. The environmental parameters of these samples, including pH, dissolved organic carbon (DOC), Ca2⁺, Mg2⁺, K⁺, and Na⁺ concentrations, exhibited wide variations across the four regions. Specifically, pH and the concentrations of Mg2⁺, K⁺, and Na⁺ showed significant variability. Additionally, a strong correlation was observed between pH and Ca2⁺, as well as between the DOC concentration and Mg2⁺ and Na⁺. Using the biotic ligand model, we derived the half-maximal effective activities of Cu (EC 50 {Cu 2+ }) for 10 soil organisms based on the chemical compositions of the soil solution samples. Additionally, a species sensitivity distribution approach was employed to determine the 5% hazardous concentration (HC5) for soil biota, which was closely associated with DOC and Na⁺ concentrations, with Mg2⁺ playing a secondary role. We attributed these relationships to the formation of DOC complexes that mitigate Cu toxicity, along with competitive interactions with cations. Notably, HC5 values did not differ significantly across sampling sites (p = 0.523). Clustering based on environmental factors grouped the samples into four clusters, each containing soils from different land use types. However, the third cluster included an outlier from agricultural soil due to its unusually high pH and DOC levels. These findings suggest that it is crucial to consider site-specific soil characteristics when determining ecotoxicologically acceptable Cu concentrations, and soil solution characteristics do not always align with specific land use patterns. [Display omitted] • Biotic ligand model and species sensitivity distribution were integrated. • From 35 soil samples, ecotoxicologically acceptable Cu concentrations were derived. • Soil solution characteristics do not consistently align with specific land uses. • Site-specific soil solution characteristics are good indicators of bioavailability. [ABSTRACT FROM AUTHOR]

The created forest plantations of 9424 hectares in the area of nutrition of mineral springs and around the resort towns of the Caucasian Mineral Waters excluded the pollution of ground and surface waters with fertilizers, created conditions for the growth of edible fungi, transferred the surface runoff to the soil, and prevented soil deflation. Soil solution from soils around Mashuk mountain, reaching hot mineral water, increases the formation of hydrogen sulfide by 6 times. The stands created conditions for the accumulation of iron, its migration to Lake Tambukan, which is necessary for the formation of healing mud. To normalize the natural conditions for the formation of healing waters, it is necessary to restore and preserve the native types of vegetation. It is revealed that native and preserved forests grew and grow on the slopes of the hydrographic system. The destroyed forests led to the formation of dangerous geological processes on the slopes and reduced the permeability of soils in the feeding area of the Tithonian stage. Protected are the indigenous subalpine meadows that covered and cover the watershed plateau-like surfaces in the upper reaches of the Berezovaya, Alikonovka and Dzhinalskiy ridge rivers. The Pasture Ridge is a barrier for broad-leaved species, and the upper (southern) climatic boundary of the oak Quercus L. does not exceed 940 m. To the south of the ridge, pine-small-leaved forests naturally grow. To normalize the nutritional conditions of the Tithonian stage it is necessary to restore planted and destroyed stands on the southern slope of the Kabardinsky ridge. Here, the flow (draining the underground waters of the Tithonian and Valanginian) should be directed outside the local underground drainage basin along one of the terraces created earlier for water infiltration by the rocks of the Tithonian. The absence of forest on three diapir mountains is explained by weakly expressed magmatogenic folds and the other forms of relief, as well as by the phytocenotic isolation of meadow and steppe vegetation.

Analysis of trace level metals in environmental samples (e.g., soil, water, and plant samples) is important for assessing environmental quality and food safety. This paper reports a non-toxic, eco-friendly, and cost-effective sensing method, capable of in-situ detection of microgram per liter (µg/L) levels of heavy metal ions in plant and soil solutions using carbon fiber electrodes (CFEs) produced without using any microfabrication. The electrochemical behaviors of the CFEs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. As proof of principle, the CFEs were validated for sensing selected heavy metals in buffer solutions as well as in extracted plant and soil solutions using differential pulse anodic stripping voltammetry (DP-ASV). Experimental results confirm that the CFEs were able to simultaneously measure cadmium (Cd), lead (Pb), and mercury (Hg) with a detection limit of 2.10, 0.93, and 1.85 µg/L respectively in buffer solution, showcasing good selectivity and sensitivity. The ideal pH range for heavy metal detection was also extensively investigated and was found to be between pH 4.0 and pH 5.0. These findings lay a better foundation towards long-term and stable electrochemical analysis for plant and soil solution matrices. [Display omitted] • Carbon fiber electrode fabricated without using any microfabrication facility. • The sensor can detect Cadmium, Lead, and Mercury in a wide range between 10 and 1600 μg/L. • This sensor can detect heavy metals in a wide variety of solutions including buffer, plant, and soil solutions. • This sensor provides repeatability over 100 measurements. [ABSTRACT FROM AUTHOR]

Soil solution pH and dissolved organic carbon (DOC) influence cadmium (Cd) uptake by hyperaccumulators but their tradeoff in calcareous soils is unclear. This study investigated the mechanisms of Solanum nigrum L. and Solanum alatum Moench in calcareous soil using a combination of concentration gradient experiments (0.6–100 mg Cd kg−1) and soil solution composition analysis. The results showed that the soil solution pH of S. nigrum remained stable despite Cd stress. On average, the soil solution pH of S. alatum was 0.23 units higher than that of S. nigrum , although pH decreased significantly under high Cd stress. In addition, the concentrations of potassium (K) and calcium (Ca) in the soil solution of S. nigrum increased and decreased under low and high levels of Cd stress, respectively. In S. alatum , the K and Ca concentrations in the soil solution generally increased with increasing Cd stress levels. Moreover, the level of DOC in the soil solution of both plants was higher under Cd stress compared to the control, and a gradually increasing trend with Cd stress level was observed in S. alatum. Consequently, the bioconcentration factors of the roots (2.62–19.35) and shoots (1.20–9.59) of both plants were >1, while the translocation factors were <1, showing an obstacle of Solanum hyperaccumulators in transferring Cd into their aboveground parts. Redundancy analysis revealed that the Cd concentration in S. nigrum roots was significantly negatively correlated with the soil solutions of K and Ca. In contrast, Cd concentrations in S. alatum roots and shoots were significantly positively correlated with soil solution DOC, K, and Ca but negatively correlated with pH. Our results suggest that calcareous soil neutralizes the acidity of released protons but does not affect cation exchange, inhibiting DOC in assisting the translocation of Cd within plants. [Display omitted] • Proton release did occur but did not break the soil's acid-buffering capacity. • The concentration of K and Ca in the soil solution significantly changed. • The level of DOC in the soil solution significantly increased under Cd stress. • Mineral ions hindered DOC to assist the translocation of Cd within plants. [ABSTRACT FROM AUTHOR]

Flexible screen-printed electrodes (SPE) were modified in a simple manner with different composite nanomaterials based on carbon allotropes, polymers, and metallic nanoparticles, for amperometric detection of nitrites in soil. Multiwalled carbon nanotubes (MWCNT), chitosan (CS), silver nanoparticles (AgNPs), 1,8-diaminonaphthalene (1,8-DAN), and a sol-gel (SG) matrix were used for modification of the carbon paste working electrodes. Sensitive and selective detection of nitrite was achieved by using a MWCNT-CS-modified sensor, in acetate buffer at pH 5, at an applied potential of 0.58 V vs. Ag/AgCl. The MWCNT-CS-based sensor displayed a specific sensitivity of 204.4 mA·M−1·cm−2, with a detection limit of 2.3 µM (S/N = 3) in a linear range up to 1.7 mM, showing good stability, reproducibility, and selectivity towards other interfering species. A miniaturized portable system using the developed flexible electrochemical MWCNT-CS-based sensors was dedicated for the detection of nitrite in different samples of soil solutions extracted by using suction lysimeters.

This study aimed to compare the effects of whole-tree and stem-only harvesting in hemiboreal forests in Latvia. Chemistry of soil solution, precipitation, litter and needles, as well as tree parameters in regenerated stands were measured from 2012 to 2021 in oligotrophic and mesotrophic Scots pine sites with mineral soils and a eutrophic Norway spruce site with drained peat soil. Compared to the undisturbed control, the soil solution pH was significantly lower and N-NO3− and K+ concentrations were significantly higher after stem-only harvesting at the oligotrophic site, stem-only and whole-tree harvesting at the mesotrophic site and whole-tree harvesting at the eutrophic site. The height growth of the regenerated stands in all sites was similar for both harvesting methods six years after planting. More slender trees were observed after whole-tree harvesting than after stem-only harvesting at the eutrophic site. Whole-tree harvesting produced significant negative short-term effects on height growth in the oligotrophic site four to six years after harvest. The nutrient levels of needles differed with harvest intensity but did not indicate insufficient nutrient availability with any type of harvesting.

Amelioration and remediation technology was developed for phosphogypsum utilization in Haplic Chernozem of South-European facies (Rostov Region). The technology comprises phosphogypsum dispersed application into the soil layer of 20–45 cm during intra-soil milling. In the model experiment, the phosphogypsum doses 0 (control), 10, 20, and 40 t ha−1 were studied. The Cd thermodynamic forms in soil solution were calculated via the developed mathematical chemical-thermodynamic model and program ION–3. The form of ion in soil solution (or water extract) was considered accounting the calcium-carbonate equilibrium (CCE) and association of ion pairs CaCO30; CaSO40, MgCO30, MgSO40, CaHCO3+, MgHCO3+, NaCO3−, NaSO4−, CaOH+, MgOH+. For calculation of the equilibrium of microelements concentration in soil solution ion including heavy metals (HMs), the coefficient of microelement association kas was proposed. According to calculations, Cd2+ ion in soil solution was mostly bounded to associates CdOH+, partly to associates CdCO30 and CdHCO3+. The calculated kas of Cd was 1.24 units in the control option of experiment and decreased to 0.95 units at phosphogypsum dose 40 t ha−1. The ratio of "active [Cd2+] to total Cd" reduced from 33.5% in control option to 28.0% in the option of phosphogypsum dose 40 t ha−1. The biogeochemical barrier for penetration of HMs from soil to plant roots was high after application of phosphogypsum. According to calculation by ION–3, the standard soil environmental limitations overestimate the toxicity of Cd in soil solution. New decision for intra-soil milling and simultaneous application of phosphogypsum was developed to provide the environmentally safe waste recycling. [ABSTRACT FROM AUTHOR]

This paper examines the composition and properties of water-soluble organic substances in relation to their localization in different parts of soil pore space, which determines the organic matter's susceptibility to biodegradation. Water-soluble organic substances contained in the sod and humus horizons of a Mollic Gleysol were extracted from pores more and less than 30 μm in diameter using sequential centrifugation of soil samples saturated to the full moisture capacity. The obtained solutions do not differ statistically significantly in the total concentration of carbon and phenolic compounds or in their absorption and fluorescence spectra; however, a strong variation in parameter values (the maximum and minimum values differ by 4–15 times) indicates that the composition of extracted substances is heterogeneous. Concentrations of simple phenolcarboxylic acids (PCAs) in solutions extracted from large pores in the humus horizon are 4–8 times higher in comparison with those extracted from smaller pores. Salicylic, benzoic, and cinnamic acids predominate in large pores (75% of the total amount); while p-hydroxybenzoic and benzoic acids predominate in small pores (67% of the total amount). Dissolved organic matter present in the ELBTg horizon of a podzolic soil was isolated from pores more and less than 14.7 μm in diameter at a soil moisture level of 22% using tension lysimeters. Dissolved organic matter extracted from large pores contains more C, N, and phenolic compounds; based on the absorption spectra, it has a larger molecular weight and a higher aromaticity degree. Organic matter contained in small pores is more hydrophobic, and its C : N ratio varies in a wider range (i.e., it is more resistant to decomposition). Phenolic compounds are predominantly confined to large pores; this ensures their preservation in soil due to the transportation to lower horizons with water flows and subsequent chemical stabilization in the form of organomineral compounds. [ABSTRACT FROM AUTHOR]

Soil salinity has been a limiting barrier for the production of vegetables in protected environments. Thus, the understanding of the sensitivity of species to this stress factor must be explored, seeking better growing conditions. Under the hypothesis that beet and radish crops are sensitive to variations in soil salinity, even at low levels, the objective of this work was to evaluate the development and productivity of these two species in soils with different salinities in a protected environment. The experimental design was completely randomized and treatments were formed by the soil salinity levels, obtained with the application of saline solution (NaCl in water), considering the soil electrical conductivity of 0.36 dS m-1 as low salinity, of 1.05 dS m-1 as moderate salinity and 2.43 dS m-1 as elevated. For all variables analyzed, except for the relative chlorophyll index in beet plants, it was found that the increase in soil salinity resulted in significant development losses of beet and radish plants. Therefore, we concluded that beet and radish crops are sensitive to the variation in soil salinity, even in relatively low concentrations, making these species an unattractive choice for cultivation in systems that present this problem.

Soil salinity has been a limiting barrier for the production of vegetables in protected environments. Thus, the understanding of the sensitivity of species to this stress factor must be explored, seeking better growing conditions. Under the hypothesis that beet and radish crops are sensitive to variations in soil salinity, even at low levels, the objective of this work was to evaluate the development and productivity of these two species in soils with different salinities in a protected environment. The experimental design was completely randomized and treatments were formed by the soil salinity levels, obtained with the application of saline solution (NaCl in water), considering the soil electrical conductivity of 0.36 dS m-1 as low salinity, of 1.05 dS m-1 as moderate salinity and 2.43 dS m-1 as elevated. For all variables analyzed, except for the relative chlorophyll index in beet plants, it was found that the increase in soil salinity resulted in significant development losses of beet and radish plants. Therefore, we concluded that beet and radish crops are sensitive to the variation in soil salinity, even in relatively low concentrations, making these species an unattractive choice for cultivation in systems that present this problem. [ABSTRACT FROM AUTHOR]

All forms of potassium in the soil are in a dynamic equilibrium with K in the soil solution, which affects K availability to the plants and it is affected by the soil pH. The objective of this study was to evaluate the effect of the soil pH and K application on the distribution of soil K forms in five Brazilian soils. The experiment was conducted in laboratory, using five soils. Treatments consisted of a factorial combination including rates of limestone (0, 0.25, 0.5, 1.0 and 1.5 times the amount of lime indicated by the SMP method to raise soil pH to 6.0) and two rates of K (0 and 1000 mg kg-1). Addition of KCl, together with limestone, promoted lower values of soil pH relatively to limestone alone. Solution K was the most sensitive K form affected by liming rates, which decreased in all soils with increases on K rate, regardless of K addition. Exchangeable K also decreased in all soils with the increase on lime applied, except on the Argisol. The non-exchangeable K levels were the least affected by liming. Addition of lime affects the distribution of K among all K forms and this may affect the availability of K to the plants. [ABSTRACT FROM AUTHOR]

Abstract Dissolved carbon (C) leaching in and from soils plays an important role in C transport along the terrestrial-aquatic continuum. However, a global overview and analysis of dissolved carbon in soil solutions, covering a wide range of vegetation types and climates, is lacking. We compiled a global database on annual average dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in soil solutions, including potential governing factors, with 762 entries from 351 different sites covering a range of climate zones, land cover types and soil classes. Using this database we develop regression models to calculate topsoil concentrations, and concentrations versus depth in the subsoil at the global scale. For DIC, the lack of a proportional globally distributed cover inhibits analysis on a global scale. For DOC, annual average concentrations range from 1.7 to 88.3 (median = 25.27) mg C/L for topsoils (n = 255) and from 0.42 to 372.1 (median = 5.50) mg C/L for subsoils (n = 285, excluding lab incubations). Highest topsoil values occur in forests of cooler, humid zones. In topsoils, multiple regression showed that precipitation is the most significant factor. Our global topsoil DOC model ( $${\mathrm{R}}^{2}=0.36$$ R 2 = 0.36 ) uses precipitation, soil class, climate zone and land cover type as model factors. Our global subsoil model describes DOC concentrations vs. depth for different USDA soil classes (overall ( $${\mathrm{R}}^{2}=0.45$$ R 2 = 0.45 ). Highest subsoil DOC concentrations are calculated for Histosols.

In this work, corrosion of an abandoned X52 pipeline steel containing artificial pits with varied depths was investigated in a simulated soil solution containing sulfate-reducing bacteria (SRB). Bio-testing, electrochemical measurements and surface analysis techniques were used to study the SRB-induced corrosion outside and inside the pits. Results show that the SRB tend to accumulate on the specimen surface (i.e., outside the pits), rather than inside the pits, resulting in accelerated corrosion of the steel. As the depth of the pit increases, there are fewer SRB adherent to the steel of the pit wall. Thus, compared to the specimen surface, the pits experience a reduced MIC. A galvanic effect exists between the outside and inside the pits, with the former serving as the anode and the latter as the cathode, further enhancing the corrosion of the steel outside the pits.

The agronomic efficiency of biochar-based fertilizers (BBFs) relies on the synthesis routes, properties, and interaction with the soil–plant system. In our study, BBFs were produced from coffee husk, low-grade acidulated phosphate rock with and without the addition of magnesium (Mg). BBFs were characterized for infrared analysis and the kinetics of phosphorus (P) release in water or citric acid (CA). The agronomic performance of BBFs was tested by growing maize and, in sequence, brachiaria grass in pots filled with two Oxisols with contrasting soil organic matter (SOM) content. Using the same chemical stoichiometric ratio, nitric acid was more effective than hydrochloric and sulfuric acids, creating BBFs with enhanced agronomic performance. The use of Mg in the BBFs synthesis reduced the P released in water. Phosphorus released in CA leachates positively correlated with the P in the shoot of both plants. BBFs produced using nitric acid had higher residual effect on brachiaria grass grown in the Oxisol with the highest SOM. Our outcomes show that the P rate for maize and brachiaria grass should be considered based on P soluble in neutral ammonium citrate plus water in BBFs. BBFs is an alternative to improve the use efficiency of P in Oxisols.

Soil pollution by multiple metal(loid)s is a common problem, and it is not easy to synchronously reduce their uptake in crops. Compounds containing iron (Fe) are often used to efficiently remediate soil metal(loid) pollution; however, its associated risks did not receive much attention especially under unsuitable soil water conditions. Pot experiments were set up using an antimony (Sb) and cadmium (Cd) co-contaminated soil treated with a continued submergence condition plus 5, 10, or 20 mg kg−1 FeCl3 (Experiment I), or treated with different water management including submergence, intermittent irrigation, and dry farming (Experiment II). Our results showed that the continued submergence resulted in excessive accumulation of arsenic (As) in different tissues of rice plants even if the soil As background concentration is low. High soil moisture content increased the available concentrations of Sb and As, but reduced that of Cd in rhizosphere soils, which was in line with their concentrations in different tissues of rice plants (Experiment II). Under a continued submergence condition, FeCl3 significantly stimulated As concentration in the shoots, roots (excluded Fe20 treatment), and husks, but reduced it in the grains. FeCl3 reduced Sb concentration only in the roots and grains, and reduced Cd concentration only in the husks, suggesting a limited efficiency of FeCl3 to reduce Cd uptake under a submergence condition. In this study, the dynamic changes of As, Sb, and Cd concentrations in soil solution, their available concentrations in rhizosphere soils, their accumulation in root iron/manganese plaques, and the relationships among the above parameters were also discussed. We suggested that if FeCl3 would be used to remediate the contaminated soils by Sb and Cd, dry farming for a short time is needed to avoid As accumulation, and intermittent irrigation is a potential choice to avoid the excessive accumulation of As, Sb, and Cd in the edible parts of rice plants.