Laboratory Soil Research Articles

Synergizing carbon sequestration mechanisms during the remediation of Cr(VI) by nano zero-valent iron loaded biochar (nZVI-BC)

Applying nano zero-valent iron loaded biochar (nZVI-BC) to remediate soil heavy metal pollution has been frequently tested in current studies. However, little knowledge has been disclosed regarding the effect of nZVI-BC on soil organic carbon (SOC) mineralization/sequestration. In this study, the dual effect of nZVI-BC addition on Cr(VI) removal and SOC mineralization/sequestration and the underlying mechanisms were explored, based on a 90 days laboratory soil incubation. The results confirmed that nZVI-BC significantly improved the Cr(VI) removal rate while markedly reducing the cumulative CO2 emissions. Following the 90 days incubation, nZVI-BC addition notably increased the contents of Fe-oxides, Fe-bound organic carbon (Fe-OC), and SOC. Pearson correlation and PLS-SEM analyses indicated that the enhanced Fe-OC content, resulting from increased Fe-oxides, was a critical abiotic mechanism for improved SOC preservation. Additionally, the observed decrease in enzymatic activity and the shift in bacterial community from unstable carbon-dominant taxa (e.g., Proteobacteria and Actinobacteria) to stable carbon-dominant taxa (e.g., Firmicutes) in the nZVI-BC treatments suggested that SOC bio-mineralization was also inhibited. Overall, this study demonstrates that nZVI-BC not only aids in heavy metal remediation but also promotes long-term SOC preservation.

Finite element analysis of soil-nailed vertical excavation in fine-grained soils in an urban area

This paper presents analysis and discussion of an urban vertical excavation, with the soil nailing technique, in fine-grained soils with high plasticity. The excavation was numerically evaluated using finite element analysis (FEA) using a 3D finite element model (FEM). Several field and laboratory soil investigations were conducted, interpreted and used in the FEA. The FEM model was calibrated using instrumentation and monitoring results during the soil nailing construction. Analyses were conducted focusing in horizontal displacements, nail pullout strength, nail tensile load, soil stress state, and tensile load at the nail head. The results showed that the behavior of the soil nailing retaining wall in fine-grained soils differs significantly from what is typically reported in the literature for non-cohesive soils. The high apparent cohesion of the fine-grained soil resulted in good performance, with reduced horizontal displacements on the face and lower tensile loads in the nails and at their head.

Assessment of Land Damage Status Using Frequency Method on Several Land Use for Biomass Production in Payakumbuh City

Intensive use of land for agricultural businesses causes the land to become very dynamic and causes a decrease in soil quality for producing biomass. This research aims to determine environmental conditions (level of damage to land and soil for biomass production) and the factors that cause soil damage in Payahkumbuh City. Land surveys were carried out using the research method in five sub-districts. Samples taken in the field are disturbed soil samples for analysis of physical properties (texture, BV, TRP, and permeability). In contrast, disturbed soil samples are used to analyze chemical soil properties (c.organic, pH, DLH, Redok). Apart from that, he also observed environmental conditions such as rocks on the surface and the depth of the soil. Next, the soil samples are explained in the soil laboratory of the Department of Soil Science and Land Resources. Data from soil physical and chemical property variables are processed, averaged, and compared with soil health standards following PP No. 150 of 2000. The research results show that the results of land identification and verification show that the land in the five sub-districts of Payakumbuh City in the research area has a Light Damage Status (RI) covering an area of 2391.65 ha and Moderate Damage (RII) covering an area of 1856.76 ha. From 10 observation points, the land in the research area has two levels of soil damage: moderate and light. Soil damage is caused by limiting factors. In moderate damage status, the limiting factors are (RII-vpre), namely soil porosity, degree of air escape, redox reactions, and electrical conductivity. Meanwhile, the limiting factors in soil with mild damage are (RI-vre) soil porosity, redox reactions, and electrical conductivity.

Risk for nitrogen leaching after application of solid manure in autumn differs between manure types

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Impact of Land Use and Land Cover Changes on Soil Physico-Chemical Properties in Southern Tigray, Northern Ethiopia

Soil quality declines due to the conversion of natural vegetation into farmland and grazing areas. The response of soil properties to land use and land cover changes (LULC) exhibits both spatial and temporal variations. This study aimed to assess the effects of LULC changes on the physico-chemical properties of soil in the Wojic watershed. Soil samples were collected from natural forests, bushland, shrubland, and cultivated lands across three landforms of the watershed (upper, middle, and lower) to evaluate the physical and chemical properties of the soil associated with different LULC types. The LULC categories were compared using mean values and critical thresholds for selected physicochemical soil properties. Soil analysis was conducted using R software, employing one-way analysis of variance (ANOVA). A normality test was performed before the post hoc analysis, and Tukey’s honest significance difference (HSD) test was utilized for mean separation among the LULC types. Additionally, a normalized difference vegetation index (NDVI) was calculated for the years 1997 and 2017. A simple linear regression model was developed to estimate soil physico-chemical properties over the past 20 years, using laboratory soil parameters and the NDVI for 2017. The pH values showed a slight decrease in cultivated land (from 5.7 to 5.4), bushland (from 7 to 6.6), and shrubland (from 6.5 to 6.2) over the study period. The analysis indicated a declining trend in physico-chemical properties, attributed to changes in vegetation cover and management practices. Consequently, the government needs to enforce policies and regulations that promote effective land resource management and utilization, with particular emphasis on the proper management and conservation of forests, bushlands, and shrublands, as well as measures to prevent increased land resettlement.

Modified Complex Electrical Resistivity Technique: Applications to Saturated and Unsaturated Soils

Abstract Direct current (DC) electrical resistivity is a common laboratory soil characterization method to support geotechnical infrastructure design and to supplement site investigations. The complex electrical resistivity method has the potential to provide additional electrical soil properties to enhance electrical soil characterization. Both methods are conventionally performed under fully saturated soil conditions; however, many environments exist where soil is not fully saturated, such as ballast structure supporting railways. In this study, a new experimental setup featuring a current enhancing agent (agar) for complex electrical resistivity testing is evaluated by testing five different soil specimens reconstituted at saturated and unsaturated conditions. Results showed that the new experimental setup is valid and can be used to obtain repeat measurements, particularly for specimens reconstituted in the unsaturated conditions where the traditional DC electrical resistivity setup yields results that are unreliable. This is one of the very few studies where tolerances for triplicate specimens are reported to establish differences in measurements from sample preparation versus discernable variability between different geomaterials. Additionally, all results are supported by a Cole-Cole model. The results show that the additional data collected in a complex electrical resistivity test can be used to differentiate different soil types that are ambiguous with the DC electrical resistivity method. The additional data have the potential to more fully characterize the electrical properties of saturated and unsaturated soils, as well as to help distinguish unique geophysical signatures of various geomaterials to enhance a geophysical site investigation for identifying soil variability in the subsurface.

Multi-Sensor Soil Probe and Machine Learning Modeling for Predicting Soil Properties.

We present a data-driven, in situ proximal multi-sensor digital soil mapping approach to develop digital twins for multiple agricultural fields. A novel Digital Soil CoreTM (DSC) Probe was engineered that contains seven sensors, each of a distinct modality, including sleeve friction, tip force, dielectric permittivity, electrical resistivity, soil imagery, acoustics, and visible and near-infrared spectroscopy. The DSC System integrates the DSC Probe, DSC software (v2023.10), and deployment equipment components to sense soil characteristics at a high vertical spatial resolution (mm scale) along in situ soil profiles up to a depth of 120 cm in about 60 s. The DSC Probe in situ proximal data are harmonized into a data cube providing vertical high-density knowledge associated with physical-chemical-biological soil conditions. In contrast, conventional ex situ soil samples derived from soil cores, soil pits, or surface samples analyzed using laboratory and other methods are bound by a substantially coarser spatial resolution and multiple compounding errors. Our objective was to investigate the effects of the mismatched scale between high-resolution in situ proximal sensor data and coarser-resolution ex situ soil laboratory measurements to develop soil prediction models. Our study was conducted in central California soil in almond orchards. We collected DSC sensor data and spatially co-located soil cores that were sliced into narrow layers for laboratory-based soil measurements. Partial Least Squares Regression (PLSR) cross-validation was used to compare the results of testing four data integration methods. Method A reduced the high-resolution sensor data to discrete values paired with layer-based soil laboratory measurements. Method B used stochastic distributions of sensor data paired with layer-based soil laboratory measurements. Method C allocated the same soil analytical data to each one of the high-resolution multi-sensor data within a soil layer. Method D linked the high-density multi-sensor soil data directly to crop responses (crop performance and behavior metrics), bypassing costly laboratory soil analysis. Overall, the soil models derived from Method C outperformed Methods A and B. Soil predictions derived using Method D were the most cost-effective for directly assessing soil-crop relationships, making this method well suited for industrial-scale precision agriculture applications.

Subjectivity of visual assessments in FOCUS kinetics and acceptability of first-order fits for regulatory modelling

The degradation half-life (DegT50) of a substance in soil plays an important role in the approval process of a plant protection product and is a sensitive input parameter for regulatory models. It is usually derived through least squares optimizations of mathematical models to measured degradation data according to EU FOCUS degradation kinetics guidance. A strong consensus on degradation parameters provides a solid foundation for parts of the environmental risk assessment. The DegT50 of a substance for regulatory modeling is preferably derived from a single first-order (SFO) model as this is currently the only kinetic model implemented in EU regulatory models of the environmental fate of pesticides. However, kinetic optimisation tools do not always provide a regulatory acceptable SFO fit even though a visual inspection of the data suggests it may be possible. It was therefore hypothesized that more acceptable SFO fits might be achieved by adapting the objective function that is minimized during the optimization.Eight objective functions with varying weightings were tested on 29 laboratory soil degradation datasets. A web-based app was developed to allow experts in environmental safety of plant protection products to visually assess the goodness of fits resulting from different objective functions. The visual assessments and a quantitative metric, newly introduced in the proposed update of the FOCUS guidance, show that the acceptability of SFO fits can be increased, but no single objective function exclusively improves all fits. The assessment reveals that expert judgment is very subjective. Participants tended to change their mind when judging the acceptance of a fit, assumingly caused by a learning curve or a period of calibration.It is concluded that different objective functions could be considered in the kinetic assessment as it can improve the acceptability of SFO fits and hence endpoints for regulatory modeling. This study reveals that various qualitative factors influence the visual judgment of experts when performing a kinetic modeling assessment. The proposed quantitative metric seems to be in alignment with the visual assessment of fits to derive modeling endpoints and a promising step toward less subjective kinetic modeling assessments.

Multifactorial Analysis of the Effect of Applied Gamma-Polyglutamic Acid on Soil Infiltration Characteristics

To investigate the mechanism and influence of applying gamma-polyglutamic acid (γ-PGA) on soil water infiltration, laboratory experiments and numerical simulations were conducted using Hydrus-1D. These studies assessed the impact of various application rates of γ-PGA on soil water characteristic parameters. Orthogonal simulation experiments on soil bulk density, γ-PGA application rates, and burial depths were performed utilizing predefined soil water characteristic values (twelve groups: nine groups of numerical simulation experiments and three groups of laboratory verification tests), and the soil infiltration characteristics were analyzed. Concurrently, an empirical model was developed to elucidate the relationships between the empirical model parameters and influencing factors, as well as to examine the sensitivity of these factors to changes in soil infiltration rate. The relationship between cumulative infiltration and the distance of wetting front movement, based on the water balance equation, was refined. The results indicated that γ-PGA significantly affected soil water characteristic parameters, where the saturated water content and the reciprocal of soil intake suction increased with rising γ-PGA applications (p < 0.01), while the saturated hydraulic conductivity and the parameter n decreased (p < 0.01), with no notable changes in the retained water content (p > 0.05). The trend in cumulative infiltration influenced by various factors could be modeled by a capacitive charging model function, which yielded a superior fit. A negative correlation existed between the sensitivity index and all the influencing factors (p < 0.05), with the order of influence being soil bulk density, γ-PGA application rate, and γ-PGA burial depth, respectively. Utilizing the modified water balance equation, the ratio of cumulative infiltration to wetting front migration distance corresponded more closely with a power function. These findings provide a theoretical foundation for further studies on the effects of γ-PGA on crop growth characteristics in fields and the optimization of γ-PGA technical element combinations.

Microplastics stimulated soil bacterial alpha diversity and nitrogen cycle: A global hierarchical meta-analysis

Microplastics (MPs) pollution is recognized as a global emerging threat with serious potential impacts on ecosystems. Our meta-analysis was conducted based on 117 carefully selected publications, from which 2160 datasets were extracted. These publications described experiments in which MPs were added to soil (in laboratory or greenhouse experiments or in the field) after which the soil microbial community was analyzed and compared to a control group. From these publications, we extracted 1315 observations on soil bacterial alpha diversity and richness indices and 845 datasets on gene abundance of bacterial genes related to the soil nitrogen cycle. These data were analyzed using a multiple hierarchical mixed effects meta-analysis. The mean effect of microplastic exposure was a significant decrease of soil bacterial community diversity and richness. We explored these responses for different regulators, namely MPs addition rates, particle size and plastic type, soil texture and land use, and study type. Of the bacterial processes involved in the soil nitrogen cycle, MPs addition significantly promoted assimilation of ammonium, nitrogen fixation and urea decomposition, but significantly inhibited nitrification. These results suggest that MPs contamination may have considerable impacts on soil bacterial community structure and function as well as on the soil nitrogen cycle.

Exploring soil erodibility: integrating field surveys, laboratory analysis, and geospatial techniques in sloping agricultural terrains

The escalating trend of land degradation poses a significant challenge, especially in sloping agricultural terrains, driven by the increasing global demand for food and the limited availability of flat arable land. In response to these challenges, farmers are compelled to shift their focus towards cultivating sloping terrains. This research aimed to employ a comprehensive methodology that integrates on-site field surveys, meticulous laboratory soil analyses, and geospatial data for mapping soil erodibility. The parameters under scrutiny encompass various crucial aspects, including soil texture (ranging from coarse sand to very fine sand, silt, and clay), soil structure, organic matter content, and permeability. The meticulous examination of these factors serves as the foundation for calculating soil erodibility, utilizing the well-established Wischmeir and Smith formula developed in 1978. The research findings present a nuanced understanding of soil erodibility in the study location, revealing a spectrum spanning low to very high erodibility. Specific units, such as Unit 1, Unit 2, Unit 3, Unit 7, Unit 9, Unit 10, Unit 13, and Unit 16, exhibit very low to low erodibility. In contrast, Unit 4, Unit 6, Unit 14, and Unit 15 showcase moderate erodibility, while units like Unit 5, Unit 8, Unit 11, Unit 12, Unit 17, and Unit 18 are characterized by moderately high to very high erodibility. These insightful results shed light on the diverse erodibility levels within the studied locations and provide valuable guidance for formulating sustainable land management practices.

Physical and Chemical Properties of Volcanic Ejecta Produced During the Eruption of Shinmoe-Dake, Mt. Kirishima: Explosive Eruption on March 25, 2018

The objective of this study was to clarify the actual physical and chemical properties of volcanic ejecta immediately after the explosive eruption of Shinmoe-dake, Mt. Kirishima, in Japan. The day after the explosive eruption occurred on March 25, 2018, permeability tests using a cylindrical frame were conducted, and samples collected in the test site were subjected to laboratory soil tests. The real infiltration capacity of the volcanic ejecta showed that the final values were lower (38–92 mm/h) in the talus inside the forest than in the plain outside the forest. This was attributed to the small particle size distribution above 1 mm, regardless of the particle size of the silt/clay particle size segment. The rainfall after the explosive eruption was at most 20–22 mm/h, indicating that the real infiltration capacity value at the end of the eruption was higher than the rainfall value. This was consistent with the fact that no debris-flow was observed at the foot of Shinmoe-dake after the recent eruption. On the other hand, examination of the chemical properties of the volcanic ejecta collected revealed high values of Ca and SO4. These compounds form gypsums by reaction with water, could reduce the infiltration capacity of deposit, possibly contributing generation of mudslide.

TOTAL NITROGEN CONTENT IN SEDIMENTS IN THE MANGROVE AND CRAB CONSERVATION AREA OF TARAKAN CITY

Nitrogen in sediments is an essential element for plants that play a role in the process of photosynthesis and stimulate growth. This study aims to examine the total Nitrogen (N) content in sediments based on differences in depth in the Mangrove and Crab Conservation Area of Pamusian Village, Tarakan City. The method used in the research is quantitative descriptive method by describing the content of Nitrogen (N) in sediments based on differences in depth at each research station and determining the location of sampling points for sampling using purposive sampling method. Sediment sampling was carried out at 3 station points, namely the Pamusian River flow area, the watchtower area and the area near residential areas. Sediment sample testing was carried out at the Soil Laboratory of the Faculty of Agriculture, Borneo University of Tarakan. The results of this study showed that the Nitrogen (N) content in sediments in the Mangrove and Crab Conservation Area of Pamusian Village at a depth of 10 cm ranged from 0.25 - 0.32%, a depth of 20 cm ranged from 0.19 - 0.24%, and a depth of 30 cm ranged from 0.14 - 0.20%. The highest total nitrogen content is at a depth of 10 cm and the station that has the highest total nitrogen content is station 3.

Model multifactor analysis of soil heavy metal pollution on plant germination in Southeast Chengdu, China: Based on redundancy analysis, factor detector, and XGBoost-SHAP

This study assessed the levels of soil heavy metal pollution in agricultural land in southeastern Chengdu and its effects on the germination stage of higher plants. Through extensive soil sampling and laboratory analyses, 15 soil environmental factors were measured, including soil density, porosity, pH, field moisture capacity (FMC), calcium carbonate (CaCO3), and heavy metals such as arsenic (As) and cadmium (Cd). Acute toxicity tests were performed on sorghum (Sorghum bicolor) and Brassica napus (Brassica napus var. napus). The results of the geo-accumulation index (Igeo) and enrichment factor (EF) analyses indicate a higher risk of pollution and enrichment of As and Cd in the study area, with relatively lower risks for other heavy metals. Additionally, the current soil heavy metal concentrations inhibited the growth of sorghum and Brassica napus shoots and roots during the germination stage. Redundancy analysis (RDA), factor detector, and XGBoost-SHAP models identified the As, Cd, FMC, and CaCO3 contents, soil density, and porosity as the primary factors influencing plant growth. Among these factors, FMC, porosity, and Cd were found to promote plant growth, whereas soil density and As demonstrated inhibitory effects. CaCO3 had a dual effect, initially promoting growth but later inhibiting it as its concentration increased. Further analysis revealed that Brassica napus is more sensitive to soil environmental factors than sorghum, particularly to Cd and As, while sorghum has greater tolerance. Moreover, roots were found to be more sensitive than shoots to soil environmental factors, with roots being influenced primarily by physical factors such as FMC and soil density, whereas shoots were affected primarily by chemical factors such as As and Cd.This study addresses the significant lack of data regarding the impact of soil heavy metal concentrations on plant growth in southeastern Chengdu, providing a scientific basis for regional environmental monitoring, soil remediation, and plant cultivation optimization.

A Holistic Irrigation Advisory Policy Scheme by the Hellenic Agricultural Organization: An Example of a Successful Implementation in Crete, Greece

The aim of this communication article is to present a successful irrigation advisory scheme on the island of Crete (Greece) provided by the Hellenic Agricultural Organization (ELGO DIMITRA), which is well adapted to the different needs of farmers and water management agencies. The motivation to create this advisory scheme stems from the need to save water resources while ensuring optimal production in a region like Crete where droughts seem to occur more and more frequently in recent years. This scheme/approach has three different levels of implementation (components) depending on the spatial level and end-users’ needs. The first level concerns the weekly irrigation bulletins in the main agricultural areas of the island with the aim of informing farmers and local water managers about crop irrigation needs. The second level concerns an innovative digital web-based platform for the precise determination of the irrigation needs of Crete’s crops at a parcel level as well as optimal adaptation strategies in the context of climate change. In this platform, important features such as real-time meteorological information, spatial data on the cultivation type of parcels, validated algorithms for calculating crop irrigation needs, an accurate soil texture map derived from satellite images, and appropriate agronomic practices to conserve water based on cultivation and the geomorphology of a farm are considered. The third level of the proposed management approach includes an open-source Internet of Things (IoT) intelligent irrigation system for optimal individual parcel irrigation scheduling. This IoT system includes soil moisture and atmospheric sensors installed on the field, as well as the corresponding laboratory soil hydraulic characterization service. This third-level advisory approach provides farmers with specialized information on the automated irrigation system and optimization of irrigation water use. All the above irrigation advisory approaches have been implemented and evaluated by end-users with a very high degree of satisfaction in terms of effectiveness and usability.

RESEARCH & DEVELOPMENT OF P2O5 DETERMINATION METHOD IN PHOSPHATE FERTILIZERS AND ITS VALIDATION

The validation of chemical measurement for Phosphorus determination in fertilizers followed a chain of experimental procedures to ascertain the performance characteristic (PC), connecting Precision, accuracy, reproducibility, recovery, linearity, limit of detection and of quantification. Performance characteristics are accomplished to ensure that analytical method fits the purpose of particular testing. This method was conducted in three stages those were preparation, testing and data processing. The standard test method for determination of P2O5 content in fertilizers used for regulatory purpose is somewhat lengthy and time taking. A modification was done to the standard method to create a more efficient approach that meets validation criteria and is suitable for analyzing advisory fertilizer samples. During the year 2023-24, comprehensive research and development activity were carried out at Soil and Water Testing Laboratory (SWTL) for Research, Faisalabad and analytical data was generated. The obtained results were processed statistically and compared with the acceptance requirements. The coefficient of determination (R2), precision and accuracy/recovery percentage respectively were 0.9996, 0.3-1.10% and 98.01-102.34%, while LOD and LOQ were 0.84 and 2.25%. Based on the results the study concluded that the modified test method applied to determine P2O5was appropriate for its intended use based on the acceptance criteria of performance characteristics set forth in the validation protocol and can be applied as routine method at laboratory.

Determination of soil organic carbon by conventional and spectral methods, including assessment of the use of biostimulants, N-fertilisers, and economic benefits

Soil organic carbon (SOC) is a very important indicator of soil quality, where even small changes can have large effects on the global carbon cycle, climate change, soil fertility and plant growth conditions. The aims of this study were to investigate changes in soil SOC using two types of biostimulants, to confirm the quality of different SOC determination methods, and to estimate fertiliser requirements and winter crop income and costs. Two methods were used to determine the concentration of SOC: the first was conventional sampling of two soil layers and laboratory analysis. The second method measured SOC using a mounted proximal soil sensor with an integrated visible and near-infrared (VIS-NIR) spectroscopic system. Experimental studies were carried out in three scenarios, of which SC1 used a biostimulant consisting of two components: one for soil (humus) and one for plants (leaf-special), SC2 used a biostimulant consisting of many bacterial species and SC3 was a control without biostimulant. The results of the 3-year experimental studies showed that the use of VIS-NIR spectroscopy in the field allows the prediction of soil SOC concentrations with sufficient accuracy. The coefficient of determination R2 ranged from 0.819 to 0.959 compared to the conventional laboratory SOC test. In the SC1 and SC2 scenarios with biostimulants, R2 was higher than in the SC3 control. The use of biostimulants significantly increased the yield of winter wheat and winter oilseed rape and reduced the need for nitrogen fertiliser per tonne of grain yield for both winter wheat (23.0–37.3 %) and winter oilseed rape (6.3–32.1 %). The economic analysis showed that the application of biostimulants increased the relative profit in all years from EUR 54 ha−1 (for winter oilseed rape) to EUR 143 ha−1 (for winter wheat) compared to the control scenario.

Methods for Measuring Organic Carbon Content in Carbonate Soils (Review)

In world practice, the measurement of the mass fraction of carbon of organic compounds (Corg) in soils containing carbonates is carried out in various ways. An analysis of methods that allow solving this problem was carried out, including the latest approaches: thermogravimetry, differential scanning calorimetry, spectroscopy. It has been shown that the presence of CaCO3 does not prevent the use of the dichromatometric method (Tyurin, Walkley-Black) for determining Corg. The disadvantages of the method boil down to the laboriousness of the analysis, the need for constant presence of the operator, incomplete oxidation of organic compounds and environmental pollution. The method of measuring soil mass loss-on-ignition (LOI) is economical and rapid, but it gives an overestimated Corg content, which is associated with the inadequacy of the conversion factor of 1.724, the presence of adsorbed and chemically bound water, as well as mineral components decomposing at T = 105–550°С. The most relevant solution for finding Corg in carbonate soils is to use an analyzer and a calcimeter, although the accuracy of Corg measurements in the presence of carbonates is significantly reduced due to the quadratic summation of the errors of the two methods. The high cost of the device, maintenance, verification and repair limit its widespread use in soil laboratories. To measure the content of soil carbonates, it is possible to use both gravimetric (LOI) and volumetric (calcimeter) methods. The use of the latter is preferable for soils with a predominance of CaCO3 in carbonate composition. Preliminary removal of carbonates from soil samples is labor-intensive and can lead to partial loss of Corg due to acid extraction. The high cost of instruments and the lack of libraries of soil spectra hinder the development of vis-NIR and MIR spectroscopy as an alternative to “wet” chemistry methods. Continuing comparative studies will improve the understanding of the spatial patterns of distribution of carbon in soil organic compounds.

High-accuracy and low-disturbance approach for identifying surface water and groundwater interactions in wetlands

Comprehending the hydrological conditions in wetlands is a critical aspect of successfully enhancing wetland conservation. The interaction between wetland surface water and groundwater is a complex process, requiring detailed onsite hydrological and soil surveys, laboratory experiments, and modeling to clarify this relationship. However, conventional investigation methods often cause significant disruptions and thus may affect the natural environment and compromise data reliability. In this study, a high-accuracy and low-environmental-disturbance (LED) approach was proposed involving modified falling head permeability and modified seepage meter tests to elucidate the groundwater characteristics in an ecological reserve. A water balance (WB) calculation method was employed to examine the performance of the proposed LED approach. The results revealed that the LED performed better than conventional methods in hydraulic conductivity and seepage velocity exploration, thereby improving the accuracy of quantifying groundwater flow. Moreover, the experimental findings and ecohydrological observations were used to assess the groundwater flow regime, and the data were consistent with the field survey results. The contradiction between conducting research and protecting ecological reserves can pose difficulties in the sustainable and effective management of wetlands. The LED approach can be applied broadly, especially in areas where significant disturbance should be avoided. The water budget model can thus be developed to help deduce the interaction between groundwater and surface water. We suggest that these innovative methods are effective tools and can assist both scientists and authorities in formulating corresponding habitat management strategies.

Modified biochar affects CO2 and N2O emissions from coastal saline soil by altering soil pH and elemental stoichiometry

The application of biochar in degraded farmland improves soil productivity while achieving the recycling of agricultural waste. The collapse of the physical structure of coastal saline soils will greatly reduce the carbon sequestration potential of biochar. Phosphorus- and magnesium-modified biochar greatly improve the stability of biochar, which endows them with the potential to greatly improve the organic carbon pool of coastal saline soil. However, changes in the properties of modified biochar increase the uncertainty of microbial driven CO2 and N2O release by affecting soil chemistry properties. In this study, through laboratory soil microcosmic experiment, we investigated the effects of magnesium-modified biochar (BCMg) and phosphorus-modified biochar (BCP) on CO2 and N2O releases from coastal saline soils, and further uncovered their potential mechanisms. Compared with unapplied biochar (CK) and unmodified biochar (BC) treatment, BCMg reduced both the releases of CO2 and N2O, and BCP decreased N2O release but enhanced CO2 release. pH is the medium through which BCMg affects the release of CO2 and N2O. Specifically, BCMg increased soil pH above 8.5, which reduced the metabolic activity of the microbial community, and the abundance of bacteria directly or indirectly involved in N2O production, thereby decreasing the releases of CO2 and N2O. The amendment of BCP changed soil elemental stoichiometry causing microbial N-limitation. Increasing CO2 release and decreasing N2O release were strategies for microorganisms to cope with N-limitation. These findings suggested that BCMg is superior to BCP in mitigating greenhouse gas emissions, providing a basis for the application of modified biochar to improve the carbon pool and reduce greenhouse gas emissions of coastal saline soil.