Soil Solution Research Articles

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.

Sources and Sinks of N in Ecosystem Solutions Along the Water Path Through a Tropical Montane Forest in Ecuador Assessed With δ15N Values of Total Dissolved Nitrogen

AbstractThe globally increasing reactive N richness affects even remote ecosystems such as the tropical montane forests in Ecuador. We tested whether the δ15N values of total dissolved N (TDN), measured directly in solution with a TOC‐IRMS, can be used to help elucidate N sources and sinks along the water path and thus might be suitable for ecosystem monitoring. From 2013 to 2016, the δ15N values of TDN in bulk deposition showed the most pronounced temporal variation of all ecosystem solutions (δ15N values: 1.9–5.9‰). In throughfall (TF), TDN was on average 15N‐depleted (−1.8 ± s.d. 0.4‰) relative to rainfall (3.4 ± 0.9‰), resulting from net retention of isotopically heavy N, mainly as NH4+. Simultaneously, N‐isotopically light NO3−‐N and dissolved organic nitrogen (DON) with a δ15N value between NO3−‐N and NH4+‐N were leached from the canopy (leaves: −3.5 ± 0.5‰). The increasing δ15N values in the order, TF < stemflow (SF, 0.1 ± 0.6‰)< litter leachate (LL, 1.3 ± 0.7‰) concurred with an increasing DON contribution to TDN reflecting the δ15N value of the organic layer (1.9 ± 0.9‰). The lower δ15N value of the mineral soil solution at the 0.15 m soil depth (SS15, −1.5 ± 0.3‰) than in LL can be explained by the retention of DON and NH4+ and the addition of NO3− from mineralization and nitrification. The increasing δ15N values in the order, SS15 < SS30 (−0.6 ± 0.2‰) < streamflow (ST, 0.5 ± 0.6‰) suggested gaseous N losses because of increasing denitrification. There was no seasonality of the δ15N values. Our results demonstrate that the δ15N values of TDN in ecosystem solutions help identify N sources and sinks in forest ecosystems.

Bioaccumulation of Atmospherically Deposited Cadmium in Soybean: Three-Year Field Experiment Combined with Cadmium Isotopes.

Atmospheric deposition plays a significant role in introducing cadmium (Cd) into agroecological systems; however, accurately determining its accumulation in crops through foliar and root uptake presents challenges. This study investigated the bioaccumulation of atmospherically deposited Cd in soybean using a three-year fully factorial atmospheric exposure experiment incorporating Cd isotope analysis. Results shown that atmospheric deposition accounted for 1-13% of soil Cd pools, yet contributed 11-72% of Cd to soybean tissues during the growing seasons. Over the course of soil exposure to atmospheric deposition ranging from 1 to 3 years, no notable variations were observed in Cd concentrations in soil solutions and soybean tissues, nor in isotope ratios. Newly deposited Cd was a major source in soybean plants, and the bioavailability of deposited Cd rapidly aged in soils. Atmospheric Cd enriched in lighter isotopes induced negative isotope shifts in soybean plants. By employing an optimized isotope mixing model in conjunction with a mass balance approach, foliar Cd uptake contributed 13-51%, 16-45%, and 21-56% to stem, leaf, and seed, respectively. This study highlights substantial contribution of foliar uptake of atmospheric deposition to Cd levels in soybean and controlling foliar uptake as a potential strategy in agroecological systems experiencing high atmospheric Cd deposition.

Enhancing the stability of soil contaminated with fluoride through the utilization of pristine and aluminium-impregnated biochar: a comprehensive mechanistic approach.

The effect of trivalent metal-modified biochar on the stability and mitigation of fluoride ions (F-) in contaminated soils remains largely unexplored, despite biochar's extensive application in F--contaminated soil. The mineral metal-modified biochar has the potential to serve as an efficient solution for soil contaminated with F-. In this study, pristine-pinecone biochar (P-BC) and AlCl3-modified pinecone biochar (A-BC) were synthesized and then utilized to remediate the soil that had been contaminated with F-. Both P-BC and A-BC efficiently immobilized F- within the contaminated soil. Further examinations through sequential extraction procedure and subsequent analysis using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and elemental dot mapping demonstrated a transformation of F- into a more stable state by A-BC treatment of the contaminated soil. This implies that A-BC may possess the capacity to function as an efficient ameliorant for immobilizing F- within the soil.

Insight into the effect of oxygen content on the corrosion behavior of X70 pipeline steel in a typical simulated soil solution by dissolution-diffusion-deposition model

In this work, traditional experimental methods were employed to investigate the effect of dissolved oxygen (DO) on the corrosion behavior of X70 pipeline steel in a low-temperature acidic-bentonite simulation soil solution. A novel model was utilized to describe the complex dissolution-diffusion-deposition process at the metal/solution interface. This model aims to enhance comprehension of the dynamics of the corrosion product layer of X70 pipeline steel under varying oxygen concentrations, as well as the effects of alloying elements (Fe, Cr and Cu) on the corrosion resistance. By integrating traditional experimental methods with calculation models, the results reveal a positive correlation between DO levels and the corrosion rate X70 pipeline steel. This relationship is attributed to the distinct characteristics of the corrosion product layers formed under different DO conditions. At low DO levels, the nucleation and growth rates of oxide/hydroxide are slower, leading to the formation of a denser, more protective corrosion product layer. Conversely, at high DO levels, the accelerated nucleation and growth rates produce larger oxide/hydroxide particles, resulting in a porous and less protective corrosion product layer. Furthermore, the variation in the protective qualities of the corrosion product layers under different DO conditions causes differences in corrosion morphology: X70 pipeline steel exhibits localized corrosion in low DO environments and more uniform corrosion under high DO conditions.

Interaction analysis between single pile and multilayered saturated soils under horizontal transient loading

This study employs the coupled finite element-boundary element method to investigate the dynamic response of single pile subjected to horizontal transient loading, which is a common scenario in high-rise building, transportation, and ocean engineering. Firstly, the single pile is modeled as a Timoshenko beam and then discretized with the finite element method (FEM). The transient solution for multilayered saturated soils due to a horizontal load, serving as the kernel function for the boundary element method (BEM), aids in the derivation of the flexibility matrix of the soils. Considering the pile-soil displacement coordination conditions, the coupled FEM-BEM equation is constructed and solved to characterize the pile-soil interaction. Since the pile discretization pattern is applied consistently to the soils, it is more effective than the discretization of infinite domain in the finite element analysis. The validity of the presented method is confirmed through comparison with the full FEM numerical simulations, demonstrating the correctness and enhanced computational efficiency. Finally, parametric studies are carried out to discuss the effects of pile's length-diameter ratio, soil's shear wave velocity and stratification.

An Overview of the Soil Acidity Causes in Ethiopia, Consequences, and Mitigation Strategies

Soil acidity is a serious land degradation problem and worldwide danger, impacting approximately 50% of the world's arable soils and limiting agricultural yield. Soil acidification is a complicated series of events that lead to the production of acidic soil. In its widest sense, it can be defined as the total of natural and human processes that reduce the pH of soil solutions. Soil acidity affects around 43% of agricultural land in Ethiopia's humid and sub humid highlands. The main objective of this seminar is to highlight different literatures on the concepts of soil acidity and to give a wealth of knowledge on the causes of soil acidity, the effects it has on agricultural production, and management strategies for reducing soil acidity and raising crop yield. Acid soils in western Ethiopia are mostly caused by topsoil erosion caused by heavy rains and high temperatures. This results in the loss of organic matter and the leaching of exchangeable basic cations (Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup>, and K<sup>+</sup>). Because ammonium-based fertilizers are easily converted to nitrate and hydrogen ions in the soil, they play a significant role in acidification. One of the reasons of soil acidity is inefficient nitrogen usage, which is followed by alkalinity exports in crops. Soil acidity in Ethiopian highlands is mostly caused by the clearance of crop residues, continuous crop harvest without sufficient fertilization, cation removal, and usage of acid-forming inorganic fertilizers. Acid soil reduces nutrient availability and produces Al and Mn toxicity. In addition to these effects, soil acidity may rapidly degrade soil physicochemical qualities such as organic carbon (OC), cation exchange capacity (CEC), soil structure, porosity, and texture. Liming, the use of organic materials as ISFM, and the adoption of crop types that are resistant to Al toxicity are all alternatives for correcting acid soils. Liming can minimize toxicity by lowering concentrations, improving the availability of plant nutrients like P, Ca, Mg, and K in the soil, and reducing heavy metal solubility and leaching. Application of organic matter has a liming impact because of its abundance in alkaline cations (such Ca, Mg, and K) that were released from OM during mineralization. The pH of the soil is raised by soil organic matter, which helps with soil acidity supplements.

Arsenic and cadmium in the hydrological cycle and soil in a maquis broadleaved evergreen forest stand in Greece. Sources of some uncertainties

ABSTRACT The concentrations and fluxes of arsenic (As) and cadmium (Cd) were examined in the hydrological cycle, litterfall and soils in a maquis broadleaved evergreen forest stand in western Greece. The concentrations of the metals in the hydrological cycle ranged from 0.076 to 0.306 μg L−1 and 0.040–0.050 μg L−1 for As and Cd, respectively. It was found that the enrichment of As in the atmosphere was both due to suspended geogenic material and long range transfer, whereas for Cd the long range transfer was the predominant way for deposition. Two models were assessed to find the volumes of percolation water to compare the fluxes with the estimated ones derived from soil solution measurements. The daily deterministic forest-hydrological model (WBS3) was found to perform better than the physically based 1D semi-distributed soil-plant-atmosphere model (BROOK90). When calculating the total amounts of the heavy metals in soils, the statistical uncertainty derived from every soil layer has to be taken into account. The residence time of Cd in the forest floor (L + FH) of the soils was found 6.4 years, whereas that of As 36.3 years. This difference shows the mobility of Cd in comparison to As in the soils of the area.

Experimental evaluation of expansive soil stabilised with sustainable binder incorporating blast furnace slag and bagasse ash

ABSTRACT Civil engineering structures made upon expansive soils known in India as Black Cotton (BC) soils are susceptible to structural damages due to their seasonal swell-and-shrink behaviour. This study focuses on assessing the mechanical performance of BC soil stabilised using unconventional binders, specifically Sugarcane Bagasse Ash (SCBA) and Ground Granulated Blast Furnace Slag (GGBS) with different proportions. The experimental evaluation included Compaction tests, Unconfined Compressive Strength (UCS) tests, Triaxial tests, and Atterberg’s limits tests. Additionally, mineralogical and morphological studies were carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and chemical analysis using x-ray fluorescence spectroscopy analysis (XRF). The results showed that the mixture containing 21% SCBA and 9% GGBS produced cementitious-siliceous-hydrate (C-S-H) molecule, which improved the strength. Based on the soil-binder percentage ratio obtained from UCS tests, a regression equation was developed to estimate consolidated soil strength. The regression model, exhibiting an impressive R2 value of 93.69%, was analysed within the framework of existing empirical correlations by other researchers. This statistical model, with its good fit, is a useful tool for evaluating the compressive strength of stabilised expansive soil. The findings provide insights into successful stabilisation solutions for expansive soils found locally and globally.

Assessment of the Modifying Effect of Zinc and Copper on Toxic Stress of Barley Plants Caused by Cadmium

In a vegetation experiment on sod-podzolic sandy loam soil with Cd2+ addition at doses of 25 and 45 mg/kg, we studied how the response of barley plants to the toxic effects of cadmium changes if various amounts of heavy metals (HM) with the functions of trace elements were introduced together with it, using the example of zinc and copper. In addition, several variants were laid, in which copper and zinc were also introduced along with cadmium. Thus, doses and combinations of metals were used in the experiment: Cd45, Cd25Cu50, Cd25Cu100, Cd25Cu100, Cd25Cu200, Cd45Cu50, Cd45Cu100, Cd45Cu200, Cd45Zn50, Cd45Zn100, Cd45Zn150. Morphometric parameters (appearance, height of plants, their biomass and leaf area), biochemical parameters (accumulation of MDA, total antioxidants and crude protein), crop structure (straw weight, grain weight, 1000 grain weight) were evaluated in experimental plants. In addition, the gross content of HM and other elements in the soil and their transition to the soil solution were analyzed. It is shown that the introduction of cadmium alone led to a significant inhibition of the growth and development of barley plants. At the same time, the combined addition of HM trace elements with cadmium significantly modified the effect of cadmium. Zinc contributed to a decrease in the toxic effects of cadmium, and the intensity of this effect increased as the concentration of zinc increased, and the toxic effects of this HM at the doses considered had not yet manifested themselves. Copper, as a more toxic element, showed its stimulating effect at lower doses than zinc, and at higher doses, the development of acute stress caused by the combined toxic effects of 2 HM was observed. This is true for a dose of cadmium of 45 mg/kg, with a lower dose of cadmium (25 mg/kg), copper had a greater stimulating effect. The considered effects were primarily noted when evaluating morphometric indicators and productivity. Based on the biochemical parameters, it was not possible to draw clear conclusions about how the addition of zinc and copper changed the effects of cadmium. Apparently, it was more appropriate to use other biochemical parameters to assess stress effects. It was noted that the introduction of trace elements generally contributed to a reduction in the accumulation of cadmium in the aboveground biomass of barley plants, however, the addition of zinc led to an increased transition of cadmium into straw, but not into grain.

33P‐isotope labelling ammonium phosphate fertilizers reveals majority of early growth maize phosphorus is soil‐derived

AbstractIn soils managed to have adequate to high Mehlich‐3 phosphorus (P) concentrations throughout the US Maize Belt, the majority of crop P is soil‐derived. Struvite, a low water solubility ammonium phosphate fertilizer, may be therefore substituted for relatively high water‐soluble monoammonium phosphate (MAP) without adversely impacting maize (Zea mays L.) P uptake and growth, while minimizing fertilizer P loss risk. We determined the relative contribution of struvite and MAP to maize P uptake and soil solution P in soils representative of the US Maize Belt by radiolabelling fertilizers with 33P. We found 8% (struvite) to 22% (MAP) of early‐to‐mid vegetative growth stage (V7) maize P was fertilizer‐derived, and thus, 78%–92% was soil‐derived. Despite similar aboveground P uptake and maize growth, maize P use efficiency (PUE) determined directly by 33P was <5% for MAP (4.9%) and struvite (1.9%) indicating that in soils with adequate to high crop‐available P, early season fertilizer PUE is relatively low. If prorated to harvest stage, in‐season PUE was estimated to be 8% for struvite and 20% for MAP. MAP and struvite did not differ in relative contributions to water‐extractable P, a proxy for P loss risk, potentially reflecting lag effects in struvite P dissolution and/or the relatively fine particle size of synthesized fertilizers (<0.1 mm diameter). Since maize aboveground biomass and P uptake were similar for both struvite and MAP, struvite could be an effective P fertilizer for soils with adequate to high Mehlich‐3 P concentrations common across the US Maize Belt.

Bioassessment of Cd and Pb at Multiple Growth Stages of Wheat Grown in Texturally Different Soils Using Diffusive Gradients in Thin Films and Traditional Extractants: A Comparative Study.

The bioavailability of heavy metals in soil is a crucial factor in determining their potential uptake by plants and their subsequent entry into the food chain. Various methods, including traditional chemical extractants and the diffusive gradients in thin films (DGT) technique, are employed to assess this bioavailability. The bioavailability of heavy metals, particularly cadmium (Cd) and lead (Pb), is also influenced by soil texture and their concentrations in the soil solution. The primary objectives of this experiment were to compare and correlate the assessment of the Cd and Pb bioavailability using the DGT technique and traditional extractants across two soil textural classes: sandy clay loam (SCL) and clay loam (CL) at two contamination levels: aged contaminated (NC) and artificially contaminated (AC). The specific objectives included assessing the bioavailability of Cd and Pb at different growth stages of the wheat plant and correlating the DGT-based bioassessments of Cd and Pb with their concentrations in various plant parts at different growth stages. This study also compared the effectiveness of the DGT method and traditional extraction techniques in assessing the bioavailable fractions of Cd and Pb in soil. The regression analysis demonstrated strong positive correlations between the DGT method and various extraction methods. The results showed that the wheat plants grown in the AC soils exhibited lower root, shoot, and grain weights compared to those grown in the NC soils, indicating that metal contamination negatively impacts plant performance. The concentrations of Cd and Pb in the wheat tissues varied across different growth stages, with the highest levels observed during the grain filling (S3) and maturity (S4) stages. It is concluded that the in situ assessment of Cd and Pb though DGT was strongly and positively correlated with the Cd and Pb concentration in wheat plant parts at the maturity stage. A correlation and regression analysis of the DGT assessment and traditional extractants showed that the DGT method provides a reliable tool for assessing the bioavailability of Cd and Pb in soils and helped in developing sustainable soil management strategies to ensure the safety of agricultural products for human consumption.

Divergent responses of aggregate breakdown by slaking to nitrogen forms in solution for contrasting soil types

Aggregate stability strongly affects many soil processes and is critical to maintain sustainable agriculture. Aggregate breakdown is controlled by the interaction between soil intrinsic properties and solution characteristics. Nitrogen fertilization including different forms is well known to influence aggregate stability; however, relative to their long-term effects, there is little recognition on the rapid response of aggregate breakdown to nitrogen solutions. This study aimed to examine the effects of nitrogen form and concentration on aggregate stability for different types of soils. Aggregate breakdown against slaking of three soil types (Phaeozem, Luvisol, and Acrisol) and three horizons (organo-mineral (A), illuvium (B), and parent material horizons (C)) was determined subjected to nitrogen solutions of three forms (CO(NH2)2, NH4+, NO3–) and five concentrations (0.05 ∼ 1.0 mol/L). Among nitrogen forms, urea solution almost had non-significant effect irrespective of soil type and horizon (p > 0.05); for NH4+ and NO3– solutions, aggregate stability showed little variations (MWD of 0.19 ∼ 0.26 mm) with electrolyte concentration for Phaeozem in B and C horizons, overall increased for Luvisol and Phaeozem in A horizon, and decreased first and then reached a steady state for Acrisol. The effects of nitrogen forms on aggregate breakdown were dependent on soil aggregation status or cementing agents (mainly organic matter, clay mineralogy). Electrolyte nitrogen solutions (NH4+ and NO3–) inhibited aggregate breakdown mainly through reducing electrostatic repulsive forces for moderately developed soils rich in swelling clays, and promoted aggregate breakdown by both weakening particle cohesion and enhancing compression pressure of entrapped air for highly developed soils rich in non-swelling clays and Fe/Al oxides. These results facilitate an improvement of fertilizer management and irrigation to improve soil quality on different soil types.

Optimal organic fertilization enhances the phytoavailability of phosphorus in the root zone of rice

AbstractOrganic fertilization is considered an effective approach in promoting agricultural green development, dramatically affecting soil phosphorus (P) availability. Nonetheless, limited information is available on the comprehensive impact of full substitution of organic fertilizer for chemical fertilizer on P speciation, phytoavailability, and apparent balance throughout different rice‐growth stages. To address this gap, a 5‐year field experiment was conducted, implementing five organic P gradients ranging from 0 (P0), 70 (P70), 140 (P140), 210 (P210) to 280 (P280) kg P2O5 ha−1 of organic fertilizer. To assess P phytoavailability in the root zone with submillimetre spatial resolutions, this study employed techniques such as the one‐ and two‐dimensional diffusive gradients in thin films (DGT) technique and the high‐resolution soil solution sampling technology (HR‐Peeper). The findings revealed that increasing P rates enhanced soil Olsen‐P and biological‐based P fractions across rice‐growth stages, primarily driven by variation in mineral‐associated P. Notably, the P140 treatment demonstrated the highest P uptake efficiency among the different rice‐growth stages, with a significant increase in soil DGT‐P, particularly in the 0–60 mm soil layer (p <0.05), providing tangible evidence for enhanced P uptake. Moreover, compared with higher P treatments (P210 and P280), the P140 treatment markedly increased P use efficiency by 31.7% and 99.0%, respectively (p <0.05). Further, with a high ratio of DGT‐P to Peeper‐P and a low apparent balance of P, organic fertilization at the rate of 140 kg P2O5 ha−1 effectively struck a balance between ensuring adequate P supply for yield stability and mitigating potential P loss risks. These results underscore the significance of optimal organic fertilization in enhancing agronomic benefits while reducing environmental risks. They offer valuable insights to support field P management strategies and government decision‐making processes.

Initial pedogenic processes, mineral and chemical transformations and mobility of trace elements in Technosols on dumps of the former copper mines in Miedziana Góra and Miedzianka, the Świętokrzyskie Mts., south-central Poland

Technosols develop, among others, on dumps of former copper mines which became overgrown in spontaneous plant succession. The aim of the study was to determine the effect of pedogenesis on soil properties, mineral and geochemical composition, as well as operationally defined forms of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in Technosols developed on former mine dumps of the Miedziana Góra and Miedzianka former mining areas in south-central Poland. The studied Technosols were weakly developed soils with a simple soil profile comprising (1) C horizons in the subsoil and (2) O and A (or AC) horizons in the topsoil. The pHH2O of soils was 5.5–8.1. High soil pHH2O values were due to occurrence of carbonates (up to 25 %). The highest content of total organic carbon (TOC) and total nitrogen (TN) was found in O horizons as well as in A and AC horizons including buried A horizon. Soil magnetic susceptibility (χ) was 6.0–171.3 × 10–8 m3 kg−1. In each profile, the highest χ values were typical of A horizons including the buried A horizon. The most common minerals present in all profiles were quartz, kaolinite and mica. There were also admixtures of carbonates (dolomite, calcite), feldspars (orthoclase and albite), jarosite, goethite and traces of Fe sulphides. SEM-EDS analyses showed that soil substrate was subject to transformations of sulphides into Fe oxides. Moreover, pedogenic Cu carbonates were found in pores and on coarse materials. Technosols were enriched in Ag, As, Cd, Co, Cu, Hg, Mo, Ni, Pb, Sb, Zn, U and Th. The most mobile trace elements in the studied Technosols were Cd, Cu and Zn. Topsoil horizons of the studied soils contained a considerable share of Pb, Cu, Zn and Ni bound with soil organic matter. Arsenic was mostly bound with Fe oxides. First indicators of pedogenesis in the studied Technosols are (1) accumulation of soil organic matter in the topsoil followed by the decrease of soil pH and leaching of carbonates, (2) mineral transformations in the soil substrate (alteration of sulphides into Fe oxides and jarosite; origin of pedogenic Cu carbonates due to crystallization from soil solutions), (3) increase of magnetic susceptibility in the topsoil which may be an effect of atmospheric dust fall out or pedogenic transformation of Fe oxides into the phases with higher magnetic susceptibility and (4) the effect of soil properties, mineral composition and soil organic matter on geochemical forms of potentially toxic trace elements. The novelty value of the study lies in the identification of pedogenic Cu carbonates and the potential effect of soil-forming processes on the increase of topsoil magnetic susceptibility.