Soil Solution Research Articles

Unveiling the impact of low-molecular-weight organic acids on enrofloxacin sorption in North China agricultural soil: Insights and implications

Low-molecular-weight organic acids (LMWOAs) play a crucial role as components of dissolved organic matter in soil, influencing the sorption/desorption, degradation, and plant uptake of diverse pollutants within the agricultural soil ecosystem. This study delves into the sorption behavior and mechanism of the fluoroquinolone antibiotic enrofloxacin (ENR) on agricultural soil in North China, focusing on the impact of LMWOAs. Through batch equilibrium experiments, we explored the sorption/desorption kinetics of ENR under varying conditions such as temperature, pH, ion strength, and ion type, with the addition of acetic acid, oxalic acid, and citric acid individually. Our findings reveal that the sorption and desorption kinetics of ENR—whether with or without LMWOAs—conformed well to the pseudo-second-order kinetic model (R2 ≥ 0.997). The presence of LMWOAs notably enhanced ENR sorption while impeding desorption in soil, with oxalic acid demonstrating the highest promotion effect followed by acetic acid and citric acid. Moreover, the sorption capacity and affinity of ENR decreased with rising solution pH, dropping from 96.8%-98.5% to 30.9%–34.4%. Acidic conditions favored ENR retention in soil, with inhibition of sorption escalating alongside increasing ionic strength. LMWOAs, soil solution pH, and coexisting ions emerge as pivotal factors shaping ENR sorption behavior. Furthermore, LMWOA presence intensified desorption hysteresis of ENR on soil, with a desorption hysteresis coefficient (HI) ≤ 0.124. These results suggest that LMWOAs restrict ENR mobility in the local soil environment, heightening the risk of its accumulation in soil and crops. This study offers valuable insights into the intricate interplay among LMWOAs, ENR sorption dynamics, and environmental outcomes, underscoring the importance of understanding such complexities in agricultural soil management.

Acidity and Salinization of Soil Following the Application of Ashes from Biomass Combustion Under Different Crop Plant Species Cultivation

Ashes from biomass combustion (BAs) are a valuable source of plant nutrients, making them suitable for fertilizing crops. BAs also contain components that directly affect soil environmental conditions, leading to improved growth and development of plants. Their deacidifying properties allow BAs to serve as a substitute for calcium fertilizers. However, they contain substantial amounts of components that can increase soil salinity, which can have negative effects. The aim of this study was to assess the impact of BAs on changes in pH and salinity of haplicluvisol soil under the cultivation of various plant species. The study also analyzed the effects of BAs on the content of total forms of calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) in the soil. The BAs used in the experiment were sourced from a combined heat and power plant that combusts forest and agricultural biomass. These BAs are distributed as a product for fertilizing agricultural land. However, their application is not subjected to further monitoring. The results indicated that the application of different doses of BAs significantly affected the pH of the analyzed soil. Compared to control objects, a significant increase in pH was observed, with these changes dependent on the species of the cultivated plant. Additionally, even the smallest doses of BAs caused an increase in the electrolytic conductivity (EC) of soil solutions, which serves as a measure of soil salinity. Despite the increase in the average EC value, the application of BAs did not alter the salinity class. The use of BAs also significantly influenced other analyzed parameters. An increase in the average content of total forms of Ca, Mg, K, and Na in the soil was observed, along with a higher degree of soil saturation with alkaline cations, compared to the control and the soil condition before the experiment. The changes in the analyzed soil parameters were significantly influenced not only by the different doses of BAs but also by the species of the cultivated plant. The greatest fluctuations in the obtained values were observed in soil under winter rape cultivation, while the smallest fluctuations were noted in soil under spring barley and potato cultivation.

Polymer-Modified Fertilizers for Mitigating Strawberry Root Burn

Polymer-modified fertilizers (PMFs) with prolonged nutrient release present a promising solution to address the challenges associated with conventional fertilization practices, particularly for sensitive crops such as strawberries. This study investigates the effectiveness of biodegradable PMFs in maintaining nutrient availability at optimal levels while minimizing root burn and nutrient losses. In a factorial field experiment, we obtaineda total of 3780 sets of parallel measured time series for soil EC, moisture, and temperature as well as two sets of harvest data to evaluate the impact of varying concentrations of polyvinyl alcohol (PVA) on the nutrient release rates from complex NPK fertilizer and monoammonium phosphate. Results indicate that polymer modifications significantly slow down nutrient release, leading to optimal salt levels and maximizing yield while remaining low enough to prevent the risk of root burn (EC of soil solution below 1 mS/cm). Consequently, the application of PMFs enhances strawberry yield surplus (on average 2.8 times in the second harvest) by ensuring a steady supply of nutrients throughout the growing season without inducing stress, which reduces the yield by nearly half. This research provides valuable insights into the development of more effective fertilization strategies for strawberry cultivation and other sensitive crops using PMFs.

Arsenic, cadmium, and chromium concentrations in contrasting phosphate fertilizers and their bioaccumulation by crops: Towards a green label?

Potentially toxic elements such as arsenic (As), cadmium (Cd), and chromium (Cr) are severely regulated in fertilizers and deserve continuous investigation. Phosphate-derived Cd has been a stepping-stone toward achieving sustainable and safe worldwide food production, especially after a new regulation aiming for reduced limits of Cd in P fertilizers (EU, 2019/1009). Three pot experiments were conducted to assess the variability of As, Cd, and Cr concentrations - with a particular focus on Cd - from monoammonium phosphates (MAP 1, MAP 2, and MAP 3 from different geographic origins) and their accumulation in limed and unlimed soils, and contrasting crops, representing staple food and significant sources of these elements for humans (i.e., potato, tobacco, and rice). A diverse array of sensitive techniques for trace elements determination were used to reveal the highest level of Cd of MAP 3 (20.71 mg kg−1 MAP), which loaded the highest amounts of this element to the soil matrix and solution, plant shoots, and xylem sap, contrasting with results for MAP 1 (0.87 mg kg−1 MAP), which has almost ten times less Cd than that required for low-Cd labeling of P fertilizers (≤20 mg Cd kg−1 P2O5). MAP 3 also had the highest Cr concentration (139.3 mg kg−1 MAP). Among crops, rice accumulated 16-fold less Cd than potato plants. Liming decreased Cd in tobacco and potato shoots up to 35%. Moreover, reductions of about 20% were also observed for Cd accumulation in tubers and sap. Conversely, Cd from MAP 3 was always much more accumulated in soil solution, achieving up to 20 μg L−1, while values < 5 μg L−1 (i.e., a groundwater limit) were obtained from MAP 1. Our findings may be used as a reference in developing green labels for fertilizers in scenarios where Cd accumulation represents a potential risk for soil and human health.

Determining the Soil Particle Shape by Use of Dynamic Image Analysis

In Soil Science, it is well established that the geometry of individual soil particles, including their shape and size, has a significant impact on a number of key physical properties of the soil and on the processes involved with it. The shape and size of soil particles directly impact aspects such as permeability, water retention, stability of soil aggregates and the availability of nutrients for plants. Therefore, accurate determination of these characteristics of soil particles becomes extremely important for understanding and effective soil management. Nowadays, dynamic image analysis (DIA) is emerging as an exceptionally versatile and effective technique that enables precise determination of particle characteristics, including shape and size, in a dynamic and non-invasive manner. DIA enables the automatic analysis of thousands of microscopic images, allowing rapid and accurate study of the morphology of soil particles at micro and macro scales. The use of dynamic image analysis in soil research provides insight into the complex structures of soil particles and better prediction of their impact on various soil processes. Moreover, DIA enables the examination of a large number of samples in a short time, which contributes to the efficiency and precision of soil testing. Therefore, dynamic image analysis is becoming a widely used technique for determining particles' characteristics, such as shape and size. In the context of an ever-increasing awareness of the sustainable use of natural resources and the need to optimize agricultural and engineering practices, dynamic image analysis is becoming an indispensable tool for soil scientists, environmental scientists and engineers. Its versatile use can contribute to further expanding our knowledge about soil and developing innovative solutions for sustainable soil and environmental management.

Tillage and cover cropping influence phosphorus dynamics in soil and water pools

AbstractWinter cover crops (CCs) have the potential to reduce phosphorus (P) loss by temporarily fixing P into CC biomass. A field experiment with no‐tillage (NT) and conventional tillage (CT) was used to study the ability of different CC species planted after corn (Zea mays L.) and soybean (Glycine max L.) harvests to reduce the P availability in soil solution. The effect of three crop rotations (corn–no CC–soybean–no CC [C–S], corn–cereal rye (Secale cereale)–soybean–hairy vetch (Vicia villosa) [C–R–S–HV], corn–cereal rye–soybean–oats (Avena sativa)+ radish (Raphanus sativus L.) [C–R–S–OR]) and two tillage (NT and CT) treatments was determined on soil available P and soil solution P content through pan (A horizon) and tension (100‐cm depth) cup lysimeters. The experiment was set up as a randomized complete block design with tillage as a split factor with three replicates. Over the study period, incorporating hairy vetch in C–R–S–HV rotation reduced the Mehlich‐3 P content in soil by 26%–29% compared to the C–S and C–R–S–OR rotation. Both CC rotations (C–R–S–HV and C–R–S–OR) were effective in reducing dissolved reactive P (DRP) concentration in pan and tension cup lysimeters compared to the C–S in both CT and NT systems. However, these results varied with CC species grown and seasonal variability in precipitation. A significantly lower DRP load with crop rotation and tillage treatments was observed mainly during the CC growing season. During the study period, crop rotations with reduced labile soil P content and DRP loss were ranked in an order of C–R–S–HV &gt; C–R–S–OR &gt; C–S. Overall, this study showed that CCs have the potential in both CT and NT systems to significantly reduce P in soil and soil solution, and these effects are resilient to a wide range of precipitation conditions.

Preliminary Studies on the Effect of Soil Conditioner (AMP) Application on the Chemical and Microbiological Properties of Soil under Winter Oilseed Rape Cultivation

This study analyzed the effect of the application of a soil conditioner under the trade name of the Agro Mineral Product (AMP) in the winter rapeseed cultivation on the bacterial and fungal abundance, ion concentrations, and electrolytic conductivity of the soil solution. It was demonstrated that the AMP influenced changes in the total abundance of the culturable fractions of the soil bacteria and fungi at each of the tested time points. A stimulatory effect of the preparation on the growth of the soil bacteria and an inhibitory effect on the development of the fungi was observed, particularly at doses of 4 and 8 t·ha−1. A dose of 12 t·ha−1 proved to be the least effective in relation to the development of the soil microbiome. Increasing the AMP fertilization dose above 4 t·ha−1 caused changes in the chemistry of the soil solution (pH, EC, HCO3−, K+, and PO4-P). It is worth noting that this primarily resulted in decreases in the amounts of mobile forms of potassium (from 40.4 mg·dm−3 in the control to 26.7 mg·dm−3 at the 8 t·ha−1 dose) and orthophosphate as phosphorus (from −6.00 mg·dm−3 in the control to 3.75 mg·dm−3 at the 8 t·ha−1 dose) in the soil solution, which resulted in a reduction in the yield of the winter rapeseed (from 4.76 t·ha−1 in the control to 4.61 t·ha−1 at the 8 t·ha−1 and 4.43 t·ha−1 at the 12 t·ha−1 AMP dose).

Geochemical Interaction and Bioavailability of Zinc in Soil Under Long‐Term Integrated Nutrient Management in Pearl Millet–Wheat System

ABSTRACTThe degree and severity of zinc (Zn) deficiency in soil reduced the agricultural yield and quality, thus encouraging malnutrition in humans worldwide. The study was hypothesized to increase the bioavailability and release of Zn in soil and Zn biofortification in wheat grains under integrated nutrient management (INM). The long‐term (54 years) experiment laid out in a split‐plot design comprising single (W) and dual (PW) applications of farmyard manure (FYM) (0, 5, 10, and 15 Mg ha−1) and nitrogen (0, 60, and 120 kg ha−1) was studied to understand the distribution of different Zn fractions in soil and their relationship to wheat grain yield and Zn uptake. A laboratory incubation study was performed on surface soils to evaluate the release kinetics of native Zn at field capacity. The different fractions of Zn in soil increased with increasing frequency and levels of FYM application. Residual Zn constituted the maximum proportion (89.03%) of total soil Zn. A high positive correlation (p &lt; 0.01) of diethylenetriaminepentaacetic acid (DTPA)‐extractable Zn and total grain Zn content were observed with different Zn fractions. The release kinetics of native soil Zn increased up to 10 days and became almost constant, indicating the establishment of chemical equilibria between the soil solid and solution phase. Thus, long‐term INM ensured higher wheat production (6.08 Mg ha−1) and Zn biofortification (38.95 mg kg−1) to combat Zn malnutrition and achieve the United Nations’ sustainable development goals on “zero hunger” and “good health and well‐being.”

An Excessive K/Na Ratio in Soil Solutions Impairs the Seedling Establishment of Sunflower (Helianthus annuus L.) through Reducing the Leaf Mg Concentration and Photosynthesis

In saline conditions, establishing healthy seedlings is crucial for the productivity of sunflowers (Helianthus annuus L.). Excessive potassium (K+) from irrigation water or overfertilization, similar to sodium (Na+), could adversely affect sunflower growth. However, the effects of salt stress caused by varying K/Na ratios on the establishment of sunflower seedlings have not been widely studied. We conducted a pot experiment in a greenhouse, altering the K/Na ratio of a soil solution to grow sunflower seedlings. We tested three saline solutions with K/Na ratios of 0:1 (P0S1), 1:1 (P1S1), and 1:0 (P1S0) at a constant concentration of 4 dS m−1, along with a control (CK, no salt added), with five replicates. The solutions were applied to the pots via capillary rise through small holes at the bottom. The results indicate that different K/Na ratios significantly influenced ion-selective uptake and transport in crop organs. With an increasing K/Na ratio, the K+ concentration in the roots, stems, and leaves increased, while the Na+ concentration decreased in the roots and stems, with no significant differences in the leaves. Furthermore, an excessive K/Na ratio (P1S0) suppressed the absorption and transportation of Mg2+, significantly reducing the Mg2+ concentration in the stems and leaves. A lower leaf Mg2+ concentration reduced chlorophyll concentration, impairing photosynthetic performance. The lowest plant height, leaf area, dry matter, and shoot/root ratio were observed in P1S0, with reductions of 27%, 48%, 48%, and 13% compared to CK, respectively. Compared with CK, light use efficiency and CO2 use efficiency in P1S0 were significantly reduced by 13% and 10%, respectively, while water use efficiency was significantly increased by 9%. Additionally, improved crop morphological and photosynthetic performance was observed in P1S1 and P0S1 compared with P1S0. These findings underscore the critical role of optimizing ion composition in soil solutions, especially during the sensitive seedling stage, to enhance photosynthesis and ultimately to improve the plant’s establishment. We recommend that agricultural practices in saline regions incorporate tailored irrigation and fertilization strategies that prioritize optimal K/Na ratios to maximize crop performance and sustainability.

Influence of micro- and nano-plastics on phenanthrene adsorption at the root-water interface

The adsorption of organic pollutants onto plant root surfaces is an initial crucial stage in the transfer of these pollutants from aqueous or soil solutions to plant systems. This study explored the potential influence of micro- and nano-plastics (MNPs) (0.1–100 μm) on the process of phenanthrene (Phe) adsorption at the root–water interface. The findings indicate that MNPs can exhibit either promotional or inhibitory effects on the root adsorption of organic pollutants, depending on both their particle size and content. Specifically, both the sorption capability of MNPs for Phe and their tendency to accumulate on or within root tissues increase with decreasing particle size. These dual effects facilitate the accumulation of nanoscale MNPs (0.1–6 μm in this work) within roots, which function as efficient carriers for Phe and increase Phe accumulation in root tissues. In contrast, MNPs with larger particle sizes (1–100 μm in this work) exhibit reduced affinity for roots and are more prone to remain in solution, thereby exerting more pronounced competitive inhibition against the adsorption of Phe by roots. However, when the concentration of nano-plastics in the rootwater system exceeded the retention capacity of the roots, the excess nano-plastics could compete with the roots for Phe, potentially reducing overall Phe sorption by the roots. These conditional effects of MNPs as either competitors or facilitators (vectors) in the root adsorption processes of organic pollutants may account for the different roles observed in previous studies where MNPs exhibited varying effects on the plant accumulation of organic pollutants.

Glyphosate application may influence the transfer of trace elements from soils to both soil solutions and plants

Trace elements dynamics in the soil-plant system depends on multiple parameters, including chelating organic compounds from natural or synthetic organic matters. In this study, we evaluated the influence of one of the most common pesticides—glyphosate—on the mobility of trace elements considering contrasted soils (uncontaminated, anthropogenically contaminated, and naturally-enriched) in a greenhouse experiment. Four modalities have been tested: one control without any application, two with different glyphosate doses (1 and 3 times the authorised field dose), and one with compost addition to evaluate its potential ability to mitigate the impact of glyphosate on trace element mobility. Both, trace element and glyphosate concentrations were measured in the soil solutions and trace element contents were determined in plants at the end of the experiment. The results showed that, although glyphosate concentrations rapidly decreased in soil solutions, glyphosate application still influenced the transfer of trace elements to both soil solution (up to 12-times higher) and plant (up to 5.2-times higher). This influence was highly dependent on both the specific elements and the type of soils considered. For instance, in uncontaminated soils, glyphosate especially increased the mobilization of Mn, Co, Zn, Mo, and Pb to soil solution. This effect diminished of 2.5 times on average with increasing soil contamination. A similar trend was observed for the transfer of trace elements from soil to plant (i.e., on average 2.2-times lower in the most contaminated compared to the uncontaminated soil). However, in the naturally-enriched soil, opposing trends were noted between soil solutions and plants. The impact of compost addition on the transfer of trace elements to plants remains unclear: compost enhanced the transfer of trace elements to soil solution in uncontaminated and naturally-enriched soils likely due to trace element input through the compost, but decreased the transfer in anthropogenically-contaminated soils likely due to adsorption processes. Therefore, glyphosate could potentially increase the exposure of trace elements through food consumption and their transfer to the ecosystem, particularly in uncontaminated and weakly contaminated soils. In highly contaminated soils, compost could mitigate the glyphosate-induced enhancement of trace element mobility to soil solutions.

How Pharmaceutical Residues Occur, Behave, and Affect the Soil Environment.

Many pharmaceuticals (PhMs), compounds for the treatment or prevention of diseases in humans and animals, have been identified as pollutants of emerging concern (PECs) due to their wide environmental distribution and potential adverse impact on nontarget organisms and populations. They are often found at significant levels in soils due to the continuous release of effluent and sludge from wastewater treatment plants (WWTPs), the release of which occurs much faster than the removal of PhMs. Although they are generally present at low environmental concentrations, conventional wastewater treatment cannot successfully remove PhMs from influent streams or biosolids. In addition, the soil application of animal manure can result in the pollution of soil, surface water, and groundwater with PhMs through surface runoff and leaching. In arid and semiarid regions, irrigation with reclaimed wastewater and the soil application of biosolids are usual agricultural practices, resulting in the distribution of a wide number of PhMs in agricultural soils. The ability to accurately study the fate of PhMs in soils is critical for careful risk evaluation associated with wastewater reuse or biosolid return to the environment. The behavior and fate of PhMs in soils are determined by a number of processes, including adsorption/desorption (accumulation) to soil colloids, biotic (biodegradation) and abiotic (chemical and photochemical degradation) degradation, and transfer (movement) through the soil profile. The sorption/desorption of PhMs in soils is the main determinant of the amount of organic chemicals taken up by plant roots. The magnitude of this process depends on several factors, such as crop type, the physicochemical properties of the compound, environmental properties, and soil-plant characteristics. PhMs are assumed to be readily bioavailable in soil solutions for uptake by plants, and such solutions act as carriers to transport PhMs into plants. Determining microbial responses under exposure conditions can assist in elucidating the impact of PhMs on soil microbial activity and community size. For all of the above reasons, soil remediation is critical when soil pollutants threaten the environment.

Fundamental study on measurement of soil pH and electrical conductivity in batch tests for the determination of soil-soil solution distribution coefficient

Soil-soil solution distribution coefficient, Kd, is used to understand the mobility of radionuclides in the soil environment. Soil pH and electrical conductivity (EC) are the important factors affecting soil Kd, but existing methods for Kd employed different conditions, as well, standard soil pH and EC methods varied in the test conditions. It would be desirable to measure both pH and EC using the same soil solution for Kd with portable meters (non-glass electrode type) that need only a small liquid volume. In this study, at first, we utilized portable pH and EC meters to examine effects of different conditions on measurements, i.e., the water/soil ratios, contact time and standing time. The results showed that portable meter measurements of soil supernatant after 1 h shaking and 1 h standing could provide comparable pH and EC values with other standard soil tests. Then measurements of pH, and EC up to 168 h were carried out, considering the Kd methods for radiocesium (Cs); only slight differences in these values were observed compared to the standard test method. Considering these results, further analysis was carried out on the correlation between soil Kd-Cs and pH and found a clear decrease of Kd-Cs at pH<5.

Water holding capacity, aggregation, respiration, and chemical character of acid soil amended rice straw biochar enriched with different volumes of liquid extract (sap) of Kappapychus alvarezii

The quality of acidic soil is determined by organic C content produced from rice straw biochar in agriculture. In this context, liquid extract from Kappapychus alvarezii (K-sap) is used as a biochar enrichment agent. Therefore, this research aimed to (i) analyze the character of K-sap enriched rice straw biochar with different volumes, as well as (ii) evaluate the impact on soil water holding capacity, size class distribution, aggregate stability index, respiration rate, and acidic soil chemical characters. The treatment tested was the volume of K-sap kg-1 biochar, namely (i) without biochar, (ii) 0 mL, (iii) 500 mL, (iv) 1,000 mL, and (v) 1,500 mL. Each treatment was repeated three times and placed according to a randomized block design procedure. The area covered by K-sap, pore size, and amorphous degree increased while the pore volume of the biochar surface decreased. The addition of 1,000 mL of K-sap kg-1 biochar released a new peak number associated with the aliphatic and aromatic groups. The K-sap enriched biochar increased the proportion of soil aggregate size of 1-2 mm, water holding capacity, carbon storage, pH, total N, available P and K, exchangeable base cations as well as base saturation. Meanwhile, the concentration of Al3+ and H+ were decreased in the acidic soil solution. The results showed that the performance of rice straw biochar, K-sap volumes, soil chemical quality, water holding capacity, and ability to store carbon of the acidic soil was improved by adding K-sap volume.

Exploring Photophysical Properties of Organic Doped Polymeric Aggregates for Detecting Relevant Inorganic Pyrophosphate: A Pathway to Sustainable Development

Pyrophosphate (PPi) is an important environmentally and biologically relevant analyte and its easy and efficient detection is crucial for sustainable development. So, here we designed and synthesized organic-doped polymeric aggregates varying the signaling units (pyrene and anthracene) and examined their photophysical properties. By altering the signaling unit while keeping the polymeric backbone intact, we observed aggregate changes and studied their optical response with inorganic pyrophosphate (PPi). Among these probes, PYR-PEI exhibited a superior turn-off response(~6.1-fold) towards PPi in aqueous media whereas the other two probes ANH-PEI and PYR-PAH showed less response. The distinct response to PPi was primarily determined by electrostatic interaction and aggregate nature. The limit of detection (LOD) for PPi using the PYR-PEI probe was found to be 4.2 ppm, which is below the maximum allowable concentration of phosphate in surface water set by the World Health Organization (WHO) at 5mg/l. The quantification limit (LOQ) for PPi sensing was observed to be 14.27 ppm. Additionally, the PYR-PEI probe showed different fluorogenic responses (ratio-metric change) in the presence of anionic surfactant sodium dodecyl sulfate (SDS), and this resultant adduct was used for the PPi detection. The formation of premicellar aggregates between them drove the difference in the fluorogenic response with PYR-PEI and surfactant. Then the PYR-PEI composite was employed to detect PPi in spiked soil solution. Finally, chemically modified paper strips were prepared for the easy, fast, and on-location detection of PPi present in real-life samples.

ORGANIC FERTILIZER: NEED OF INDIA

Organic fertilizers are naturally available mineral sources that contain moderate amount of plant essential nutrients. They are capable of mitigating problems associated with synthetic fertilizers. They reduce the necessity of repeated application of synthetic fertilizers to maintain soil fertility. They gradually release nutrients into the soil solution and maintain nutrient balance for healthy growth of crop plants. They also act as an effective energy source of soil microbes which in turn improve soil structure and crop growth. Organic fertilizers are generally thought to be slow releasing fertilizers and they contain many trace elements. They are safer alternatives to chemical fertilizers. However, the improper use of organic fertilizers leads to overfertilization or nutrient deficiency in the soil. Hence, controlled release of organic fertilizers is an effective and advanced way to overcome these impacts and maintain sustainable agriculture yield.[a]

Различные формы Sr в агротемногумусовых подбелах юга Приморского края

To assess the concentration level and identify the main phase-carriers of various forms of strontium (Sr), the total content, distribution and concentration of water-soluble forms of the element in Albic Stagnosoils, which composed the bulk of the arable fund of the region under study, were studied. Full-profile soil pits were dug at the long-term fallow, phytoreclamative, and fertilized with mineral and organic fertilizer variants of the experience. The study of the different Sr forms contents was carried out by energy dispersive X-ray fluorescence spectroscopy and atomic absorption spectrometry. The main Sr volume was immobilized in the composition of soil mineral phase in soils of all variants of the experience. The addition of mineral fertilizers to soil was accompanied by an increase in the total content (by 6.4 %) and concentration of water-soluble (by 5,7 times) Sr forms, compared to the soil of fallow, and intensification of Sr sorption by Mn-containing soil compounds. The long-term addition of different types of organic fertilizers contributed to the activation of stable Sr-organic complexes formation. Under a green manure application in conditions of soil solution acidity decrease, the increase in the influence of Ca-containing soil compounds on the distribution of Sr has been shown. The soils of all variants of the experience were characterized by the absence of factors and conditions that contributed to the Sr accumulation in profiles, it was suggested by the lower total Sr content compared to the mean background content for surface soils around the world and to the mean content in agricultural soils in Japan.

Опыт изучения трансформации подзолистых почв в условиях городской среды Севера

The results of soil studies of one of the medium-sized cities of the Russian European Northeast – Syktyvkar (Russia, Komi Republic, middle taiga subzone) are presented in the article. The series from a podzolic soil with a microprofile of podzol (Albic Retisol (Loamic, Protospodic)) typical for the region to various variants of its human transformation in urban conditions – cultivated agrodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Aric, Humic)), represented on the site of the Botanical Garden, to urbodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Humic, Transporti-Novic, Thaptoaric)) and urbostratozem (Urbic Technosol (Loamic, Eutric, Humic Transport)) described in the central part of the city, included in the urban development in the first half of the XX century is considered. In urbo-soil and urbanostratozem the thickness of urbogenic horizons is approximately 40 and 70 cm. It is shown the first stages of the development of the territory of Syktyvkar city are associated with the agricultural impact. Subsequently, the arable horizons overlap with the horizons of the urban cultural layer. In the considered series of soils, weak alkalinization, an increase in the absorbed bases and the total mineralization of the soil solution were found. A noticeable increase in the concentration of organic carbon in modern arable and urban horizons, as well as the thickness of horizons with the organic carbon content of more than 0.6% was revealed. An indirect evidences of changes in the composition of iron and manganese minerals (due to an increase in the pH) with partial preservation of zonal soil formation trends has been found. The revealed direction of soil evolution is consistent with the one previously described in the cities of the European part of Russia.

Interactions between arsenic and nitrogen regulate nitrogen availability and arsenic mobility in flooded paddy soils

In paddy soils, arsenic (As) stress influences nitrogen (N) transformation while application of N fertilizers during rice cropping affects As transformation. However, specific interactive effects between As and N in flooded paddy soils on As mobility and N availability were unclear. Here, we examined N and As dynamics in flooded paddy soils treated with four As levels (0, 30, 80 and 150 mg kg−1) and three urea additions (0, 4 and 8 mmol N kg−1). Arsenic contamination inhibited diazotrophs (nifH) and fungi but promoted AOA and denitrification genes (narG, nirK, nirS), decreasing dissolved organic N, NH4+-N and NO3–-N. Besides, urea application stimulated As- and Fe-reducing bacteria (arrA and Geo) coupled with anammox. On Day 28, the addition of 8 mmol N kg–1 increased total As concentrations in solutions of soils treated with 30 and 80 mg As kg−1 by 2.4 and 1.8 times compared with the nil-N control. In contrast, at 150 mg As kg−1, it decreased the total As concentration in soil solution by 63 % through facilitating As(III) oxidation coupled with NO3–-N reduction. These results indicate that As contamination decreases N availability, but urea application affects As mobility, depending on As contamination level.

Cylindrical cavity expansion-contraction solutions in undrained MCC soils with the auxiliary variable approach

Cylindrical cavity exhibits non-self-similarity during contraction process following expansion. Previous studies solve this problem with total strain approach and simple constitutive models, but the approach is not applicable when using an advanced constitutive model. This paper presents a semi-analytical solution for a cylindrical cavity undergoing expansion-contraction in undrained soils with auxiliary variable approach, incorporating the Modified Cam-Clay (MCC) model. The stress states around the cavity are formed by the superposition of initial and superimposed stress states. By treating superimposed effective stresses as self-similar, a semi-analytical solution is derived for solving the cavity expansion-contraction problem. The elastoplastic stress-strain relationship is formulated as a set of first-order differential equations, which can be solved as an initial value problem though Runge-Kutta (RK) method. Then the stress distribution around the cavity during expansion-contraction process can be determined. To validate the proposed approach, a series of well-conduced self-boring pressuremeter (SBP) tests are used to verify the proposed approach, which shows good agreements. Additionally, a FEM simulation incorporating the MCC model is performed, and the simulation results are presented to carry out parametric studies on soil parameters. A significant influence on the range of the plastic and reverse plastic zones is shown for overconsolidation ratio, while the in-situ coefficient of the earth pressure only quantitatively affects the stress distribution.