Soil Physicochemical Properties Research Articles

Mechanism of stabilized sludge-driven remediation in saline-alkali soil: New insights from salt-discharge capacity and microbially mediated carbon/nitrogen cycles

Stabilized sludge products (SSP) are promising conditioners for saline-alkali soils, capable of enhancing soil physicochemical properties and stimulating microbial communities. However, there is limited knowledge regarding the effects of SSP on soil salt-discharge capacity and carbon/nitrogen cycles. Here, a six-month incubation experiment was conducted to evaluate SSP (0 % ~ 60 %) on saline-alkali soil properties, salt leaching, and microbial functions. It was found that after SSP (≥30 %) treatment, saline-alkali soils were significantly remediated (p < 0.01), with organic matter increasing by 5.3–9.8 times, nutrient levels rising to first-grade, porosity improving by 34.3 % ~ 93.3 %, and meso/macro-aggregates content increasing by 39.0 % ~ 201.3 %. The Na+ leaching rate increased from 1.1 % to 53.3 % ~ 79.3 %, indicating a substantial improvement in salt-discharge capacity. Correlation analysis revealed that SSP organics loosened pore spaces by promoting soil particle agglomeration, which in turn improved salt-discharge capacity. Further, the 30 % SSP significantly increased the microbial functions involved in nutrient cycling, such as carbon fixation (photosynthetic pathway), nitrogen fixation, dissimilatory nitrate reduction, and nitrification (p < 0.01). Contribution analysis implied that the up-regulation of gene abundance assigned to carbon/nitrogen cycle was attributed to balancing effect of SSP on dominant genera. Finally, the excellent growth of alfalfa seedlings verified the soil productivity restoration of degraded saline-alkali soils. These findings provide new insights into salt stress alleviation and nutrient cycling in degraded saline-alkali soils.

Microplastics' impact on soil health and quality: Effect of incubation time and soil properties in soil fertility and pollution extent under the circular economy concept.

The aim of the present study is to highlight the effect of two commonly used plastics, polyethylene (PE) and polyethylene terephthalate (PET), on the quality and health indices of soil. To this end, a pot experiment was carried out using two soils, one acidic and one alkaline. The soil samples were collected from rural areas of central and Northern Greece and had similar particle size composition and almost equal copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb) concentrations. PE and PET microplastics (MPs) were added into the soil samples in two ratios (2% and 4% v/v) and remained in the soils for 20, 60 and 120 days. Then, the changes in the properties, nutrients, potentially toxic elements and health indicators of the soil samples were measured. PE addition at 4% v/v caused the maximum increase in trace element availability when it remained in the soil sample for 120 days. In contrast, PET addition caused a maximum decrease in the DTPA-extractable concentration of toxic elements (Cd and Pb), after 120 days of incubation in acid and alkaline soil. The present work provides a fresh perspective evaluating MPs from unwanted waste to materials with potential positive benefits, enhancing the circular economy approach to soil systems. Knowledge of the MPs present in soils, along with physicochemical soil properties, including their nutrient and toxic element content, are critical aspects that need to be addressed to ensure that soil quality and health are not adversely affected.

Prediction and pathway models for assessing soil properties influencing soil selenium enrichment and bioavailability in Aksu Prefecture, northwest China

Selenium (Se) in soil is the primary source of human Se intake, and its content and bioavailability are influenced by soil physicochemical properties. However, the influence of soil physicochemical properties on Se enrichment and bioavailability in soil remains uncertain. Therefore, this study investigated 536 soil samples and their corresponding wheat grain samples collected from the oasis zone of Aksu Prefecture, located in northwest China. The Se content, spatial distribution, and bioaccumulation factor (BCF) in soil and wheat grains as well as soil Se fractions were examined, and the effects of soil physicochemical properties on Se enrichment and bioavailability were assessed. The results indicated that the mean Se content of soil (0.32 mg/kg) surpassed the national Se background level for Chinese soil by a factor of 1.10. The average Se content (0.13 mg/kg) in wheat grains met the national standard for Se-rich cereal products. The prediction model established using multiple linear regression showed that soil calcium carbonate (CaCO3), organic matter (OM), cation exchange capacity (CEC), and electrical conductivity (EC) were the main physicochemical factors influencing Se enrichment in soil, accounting for 29 % of the variation. The main physicochemical factors affecting Se bioavailability were CaCO3, OM, and iron, and the main Se fractions were the exchangeable and humic acid-bound Se fractions, which together explain 12 % of the variance. Additionally, a structural equation model was employed to analyze the pathways and interactions of soil factors on soil Se enrichment and bioavailability. The results indicated that soil CaCO3 and OM were the most critical factors affecting Se enrichment and bioavailability in soil. These findings can provide technical guidance for the cultivation and layout of Se-rich wheat in local and other similar regions around the world.

Diversity of Ectomycorrhizal Fungal Communities Associated with Tuber koreanum in Korea

Ectomycorrhizal fungi (EMF) are crucial for the formation of Tuber fruiting bodies, including the newly discovered T. koreanum, in Korea. This study explores the diversity and distribution of EMF communities associated with T. koreanum across various regions in Korea and assesses the effects of soil physicochemical properties on these communities. Soil analysis indicated that T. koreanum habitats have a lower pH compared to T. melanosporum habitats documented in other studies, with sandy loam texture being optimal for fruiting body development. Nonmetric multidimensional scaling analysis revealed significant positive correlations between the relative abundances of certain EMF genera and exchangeable potassium and calcium. These findings offer valuable insights into the ecological requirements of T. koreanum and support future conservation and cultivation strategies for truffle species in Korea.

A conceptual model explaining spatial variation in soil nitrous oxide emissions in agricultural fields

Soil emissions of nitrous oxide contribute substantially to global warming from agriculture. Spatiotemporal variation in nitrous oxide emissions within agricultural fields leads to uncertainty in the benefits of climate-smart agricultural practices. Here, we present a conceptual model explaining spatial variation in temporal patterns of soil nitrous oxide emissions developed from high spatial resolution measurements of soil nitrous oxide emissions, gross nitrous oxide fluxes, and soil physicochemical properties in two maize fields in Illinois, USA. In sub-field locations with consistently low nitrous oxide emissions, soil nitrate and dissolved organic carbon constrained nitrous oxide production irrespective of changes in soil moisture. In sub-field locations where high emissions occurred episodically, soil nitrate and dissolved organic carbon availability were higher, and increases in soil moisture stimulated nitrous oxide production. These findings form the ‘cannon model’ which conceptualizes how sub-field scale variation in soil nitrate and dissolved organic carbon determines where increases in soil moisture can trigger high soil nitrous oxide emissions within agricultural fields.

Mineralogy and physicochemical properties of soils at topounits along toposequence of shale derived soil in a tropical rainforest zone, Nigeria

Mineralogy and physicochemical properties of soils at topounits along toposequence of shale derived soil in a tropical rainforest zone, Nigeria

Soil-associated fungal and prokaryotic diversity influenced by stoniness, depth and vintage in a high-altitude vineyard

Soil microbes are increasingly recognised as key contributors to wine terroir, playing crucial roles in soil health and nutrient cycling. Fungi and prokaryotes interact with soils, influencing physical and chemical properties and mediating nutrient availability for roots. These microorganisms also impact vine performance and wine quality. Viticulture is expanding to higher elevations due to their cooler temperatures; Mendoza's mountainous regions are of particular interest being, characterised by vineyards with heterogenous soil stoniness. However, the effect of this variability on soil-associated microbial communities remains unclear. This study explores microbial populations (alpha and beta diversity, taxonomical composition, and their relationship with soil physicochemical properties) in soils of contrasting stoniness, at different depths, vintages and sample types. A Malbec vineyard with heterogenous soil stoniness was selected, with two experimental sites 30 m apart containing stony soil (SS; 77 % stoniness) and non-stony soil (NS; 0 % stoniness), respectively, and which were managed identically. Samples were collected from two depths (0.3 m and 0.6 m) during two vintages (2017 and 2018), from bulk and rhizosphere. Amplicon sequencing targeted the V3-V4 region of the 16S rRNA gene (prokaryotes) and the ITS1 region (fungi). Results showed that soil type significantly influences fungal populations, with less effect on prokaryotes. Vintage, reflecting annual changes in weather and viticultural practices, was the most significant factor affecting microbial communities. Depth was particularly important for fungi, while the sampling type (bulk or rhizosphere) had no significant impact on the microbiome within the same soil profile. Certain soil components were found to influence microbial communities: pH affected prokaryotes, while calcareous content specifically influenced the Proteobacteria phylum. Additionally, five fungal orders were more abundant in the stony soils, though some remained unidentified. These findings provide a baseline for understanding microorganisms in contrasting soils types of a high-elevation vineyard, and they highlight the role of microbial diversity in supporting unique soil-plant-environment interactions.

Soil health assessment of dressing and smelting slag field based on heavy metal pollution-buffer-fertility three aspects

The soil health of heavy metals in dressing and smelting slag field varies soil physicochemical properties. This study proposed a new soil health index based on heavy metal pollution-buffer-fertility for dressing and smelting slag field. Consequently, spatial distribution of soil physicochemical properties and heavy metals were varied, and correlated to each other. Soil buffer function and fertility played a much more important role in soil health in the dressing and smelting slag field located in Gejiu city, which can result in that soil health indexes were higher than those in Huili county, although the soil heavy metal pollution in the former was severer than that in the latter. Maximum values of soil health indexes for dressing and smelting slag field in Gejiu city were 3.84, 0.61, and 1.75 corresponding to additive, multiplicative, and maximum value composite methods, which were higher than those in Huili county with 2.25, 0.61, and 0.17. The former’s high value is concentrated in southeastern regions and low value in some western areas, the latter’s high value occurred in southeastern districts and low value in northwestern places. So this study unveils a novel perspective on the soil health consequences associated with soil heavy metal pollution-buffer-fertility three aspects.

Quantification of soil nutrient stocks and stoichiometric ratios in Eucalyptus pellita biomass plantation chronosequence in Papua New Guinea

Eucalyptus pellita biomass tree plantations have been widely established in the native grasslands of Markham Valley in Papua New Guinea for bioenergy production and carbon capture. However, the impacts of converting grasslands to energy plantations, and the ensuing soil transformations across the plantation chronosequence, remain largely unexplored. Such land use transitions are associated with depletion of C sinks, increased C emissions, and potential implications for climate change. This study aimed to evaluate dynamic changes in key soil physico-chemical properties, as well as nutrient stocks of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP), alongwith their stoichiometric ratios. A chronosequence of E. pellita plantations aged 2-, 4-, 7- and 10-years along with native grassland sites, was examined across two sampling seasons (January and June). The results indicated significant (p < 0.05) impacts of tree stand age on SOC and TP concentration and stocks, while TN remained unaffected. Soil NH4+-N concentration declined with the plantation age, contrasting with relatively steady NO3–-N levels across the chronosequence. SOC and TP stocks within the top 45 cm of soil depleted at rates of 0.19 Mg (Mega Gram) ha-1y-1 and 0.011 Mg ha−1 y-1, respectively. The broader stoichiometric ratio of C:N (> 25:1) observed in soils of 4- and 7-year-old plantations suggest potential nitrogen immobilization and mineral N deficiency to tree nutrition. Conversely, the C:P ratios across the chronosequence were < 200, favoring the net mineralization of organic P compounds. Overall, afforestation of grasslands with E. pellita for biomass production does not appear ecologically beneficial in the short-term (<10 years), when considering only the belowground SOC sequestration potential.

Analysis of Microbial Community Heterogeneity and Carbon Fixation Capabilities in Oil-Contaminated Soils in Chinese Onshore Oilfields.

This study selected 27 soil samples from four representative horizontally distributed onshore oilfields in China to explore the diversity of soil microbial communities and their carbon fixation capacity, with a focus on the potential interaction between pollution and carbon fixation under oil pollution stress. The analysis of the soil physicochemical properties and microbial community structures from these oilfield samples confirmed a clear biogeographic isolation effect, indicating spatial heterogeneity in the microbial communities. Additionally, the key factors influencing microbial community composition differed across regions. The dominant bacterial phyla of soil microorganisms under soil pollution stress were Proteobacteria, Actinobacteriota, Chloroflexi, Acidobacteriota, Firmicutes, Bacteroidota, and Gemmatimonadota. A correlation network analysis identified Immundisolibacter, Acinetobacter, Blastococcus, Truepera, and Kocuria as key players in the microbial network, with most showing positive correlations. The results of the KEGG database functional annotation showed that degradation and carbon fixation metabolic pathways coexist in soil samples and maintain a balanced relative abundance. These metabolic pathways highlight the functional diversity of microorganisms. Among them, prokaryotic and eukaryotic carbon fixation pathways, along with benzoate degradation pathways, are predominant. These findings establish a theoretical basis for further exploration of the synergistic mechanisms underlying pollution reduction and carbon sequestration by microorganisms in petroleum-contaminated soils.

The Colonization of Synthetic Microbial Communities Carried by Bio-Organic Fertilizers in Continuous Cropping Soil for Potato Plants.

Synthetic microbial communities (SynComs) play significant roles in soil health and sustainable agriculture. In this study, bacterial SynComs (SCBs) and fungal SynComs (SCFs) were constructed by selecting microbial species that could degrade the potato root exudates associated with continuous cropping obstacles. SCBs, SCFs, and SCB + SCF combinations were then inoculated into organic fertilizers (OFs, made from sheep manure) to produce three bio-organic fertilizers (BOFs), denoted by SBFs (BOFs of inoculated SCBs), SFFs (BOFs of inoculated SCFs), and SBFFs (BOFs of inoculated SCB + SCF combinations), respectively. The OF and three BOFs, with a chemical fertilizer (CK) as the control, were then used in pot experiments involving potato growth with soil from a 4-year continuous cropping field. Microbial diversity sequencing was used to investigate the colonization of SCBs and SCFs into the rhizosphere soil and the bulk soil, and their effects on soil microbial diversity were evaluated. Source Tracker analysis showed that SCBs increased bacterial colonization from the SBFs into the rhizosphere soil, but at a relatively low level of 1% of the total soil bacteria, while SCFs increased fungi colonization from the SFF into the bulk soil at a much higher level of 5-18% of the total soil fungi. In combination, SCB + SCF significantly increased fungi colonization from the SBFF into both the bulk soil and the rhizosphere soil. Overall, the soil fungi were more susceptible to the influence of the BOFs than the bacteria. In general, the application of BOFs did not significantly change the soil microbial alpha diversity. Correlation network analysis showed that key species of bacteria were stable in the soils of the different groups, especially in the rhizosphere soil, while the key species of fungi significantly changed among the different groups. LEfSe analysis showed that the application of BOFs activated some rare species, which were correlated with improvements in the function categories of the tolerance of stress, nitrogen fixation, and saprotroph functions. Mantel test analysis showed that the BOFs significantly affected soil physicochemical properties, influencing bacterial key species, and core bacteria, promoting potato growth. It was also noted that the presence of SynCom-inoculated BOFs may lead to a slight increase in plant pathogens, which needs to be considered in the optimization of SynCom applications to overcome continuous cropping obstacles in potato production.

Geostatistical modelling improves prediction of Macrophomina phaseolina abundance and distribution in soybean fields.

Charcoal rot, caused by the soilborne fungus Macrophomina phaseolina (Mp) poses a serious threat to soybean health and harvests at a global scale. Mp exhibits varying distribution patterns across fields, which complicates our ability to predict disease occurrences and outbreaks. Therefore, determining the spatial distribution of Mp abundance and its relation with soil physicochemical properties would help to inform precision management decisions for mitigating charcoal rot. To achieve this, Mp colony forming units (CFU) and edaphic properties were evaluated in 297 soybean fields located in the main soybean growing regions across 7 Departments of Paraguay. A pattern of decreasing CFU density was observed from the south-eastern to the western part of the country. While several edaphic factors are positively correlated with Mp CFU, pH showed a significant negative correlation with CFU. Both spatial and non-spatial model suggest that cation exchange capacity, percentage of clay, and pH could be potential predictors of Mp CFU abundance. Including spatial dependence of edaphic factors improved the prediction of Mp CFU more effectively than classical statistical models. We demonstrated that the occurrence of Mp shows a significant spatial clustering pattern as indicated by Moran's I. Our findings will help growers and policy-makers make informed decisions for managing Mp by improving our ability to predict which agricultural fields and soils are at greatest risk for charcoal rot.

Impact of gradient zero-valent iron pollution from steel works on soil microaggregate geochemical processes and dissipative structures

Abstract: Zero-valent iron (ZVI) contamination from steel works poses significant threats to soil quality and ecosystem health, particularly affecting soil microaggregates, which are fundamental to soil structure and function. In this study, we systematically investigated the impact of gradient ZVI pollution on the organic geochemical environment of soil microaggregates around steel works located in the core water source area of the Middle Route of the South-to-North Water Diversion Project in China. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), were employed to comprehensively characterize the geochemical processes, mineralogy, and organic matter environment of soil microaggregates. The findings revealed that soils near the steel works were acidified and strongly oxidized, with heavy metal contents, particularly Fe, significantly decreasing with increasing distance from the steel works (Fe content decreased from 27,516.2 mg/kg to 23,492.6 mg/kg). The pH of soils near the steel works was lower, while oxidation-reduction potential (ORP) and electrical conductivity were higher. XPS analysis indicated a higher content of reactive oxygen species (ROS) near the steel works and significantly lower soil organic matter content. The iron valence distribution showed spatial differences, with higher Fe2⁺ content on the surface of soil microaggregates near the steel works and Fe³⁺ dominating in areas farther away. These results suggest an evolutionary sequence of ZVI from Fe (0) oxidation to Fe(II) and then to Fe(III). The formation of dissipative structures in soil microaggregates due to ZVI contamination significantly affects soil physicochemical properties and the organic environment. This study provides valuable insights into the multifaceted impacts of industrial activities on soil ecosystems and offers a scientific basis for soil conservation and remediation strategies.

Effects of different straw return methods on soil properties and yield potential of maize

Long-term continual straw return can enhance soil quality and increase crop yields by perpetually altering the soil environment. However, little is known about how different straw return methods affect soil physicochemical properties, enzymatic processes, and crop yields. The study aims to determine how different straw return practices improve soil structure, nutrients, enzyme activities, and maize yields. In this experiment, a field trial was conducted in 2021–2022 in the irrigated area of the Tumochuan Plain Irrigation District to determine the effects of four different straw returns on soil structure, nutrients, enzyme activities, soil quality, and maize yields. The four types of straw return included straw incorporation with deep tillage (DPR), straw incorporation with subsoiling (SSR), no-tillage mulching straw return, and farmer’s shallow rotation (CK). Our results showed that DPR and SSR enhanced water retention capacity by reducing the bulk weight of the 0–45 cm soil layer. DPR and SSR significantly increased soil organic C (12.76%), total nitrogen (25.32%), and available nutrients (i.e. AP, NO3−–N) in the 0–45 cm soil layer compared to CK, whereas there were no differences between straw-returned treatments in the 0–15 cm soil layer. Finally, maize yield was significantly increased by 13.14% and 11.41% in the second year of DPR and SSR, respectively, compared to CK. This study demonstrated that DPR and SSR are effective at enhancing the agricultural utilization of crop residues and represent feasible strategies for improving physical, chemical, and biological processes in continuous maize cropping systems, leading to increased crop productivity.

Aliphatic carbon regulates soil water repellency in a chronosequence of grassland enclosure in the Loess Hilly Region

Considering the potential enhancement of soil water repellency (SWR) due to the increased accumulation of soil organic matter (SOM) under grassland enclosure, there may be an increased risk of soil erosion and degradation as it can reduce water infiltration and penetration into the soil. There remains a knowledge gap pertaining to the relationship between SWR and plant growth, soil physicochemical properties, SOM composition, and particle size in enclosed grassland. The main objective is to investigate the impact of different grassland enclosure years (14a, 23a, 32a, 40a, and 51a) on SWR in temperate grasslands of the Loess Hilly Region using the water drop penetration time (WDPT) method. Results showed that, at the early stage of enclosure (<32 years), in-situ grassland soils mainly showed slight water repellent and hydrophilic characteristics. In contrast, grassland soils at the late stage of enclosure (>32 years) exhibited a transition towards strong water repellency, accompanied by the emergence of severe hydrophobicity. The potential SWR also exhibited a significantly higher trend in the 40a and 51a grassland compared to the previous 32 years of enclosed grassland. Moreover, the SWR increased as the soil particle size decreased, and exhibited an upward trend with increasing years of grassland enclosure. Notably, in the 40a and 51a grasslands, SWR for sieve size of soils <0.05 mm was significantly higher than that observed in the initial 32a grasslands, reaching a strong water repellent level. These findings highlight that grassland enclosure significantly promoted the development of the SWR. Correlation analysis and random forest models showed that NO3--N, litter biomass, plant height, TN, CO, C–H, bulk density and plant richness were identified as the primary factors controlling SWR. The structural equation model (SEM) analyses further suggested that grassland enclosure indirectly affected SWR through aliphatic C–H groups, which was influenced by plant properties. Consequently, the consideration of SWR formation mechanism is imperative in order to mitigate the risk of soil erosion and degradation in enclosed grassland ecosystems.

The amendment value of pulp and paper mill sludges in Finnish coarse-textured soil

As a source of exogenous organic matter, pulp and/or paper mill sludges (PPMS) may have beneficial effects on crop productivity and soil chemical and physical properties. This study's aim was to assess the impacts of two different PPMS materials on crop yields, the quality of percolation water, and soil chemical and hydraulic properties in a three-year field experiment on a silt loam soil in East Central Finland. Fresh (FPMS) and lime-stabilized (LPMS) sludges were applied once at rates of 21–28 fresh-Mg ha−1 in the spring prior to the sowing of grass ley under barley as a cover crop and incorporated into the upper 7 cm soil layer. Supplemental nitrogen (N) was applied at levels of 40 and 80 kg ha−1. A decrease of barley grain yield due to N immobilization was observed at the N level 40 kg ha−1, but the standard N application rate (80 kg ha−1) connected with a moderate C:N ratio (FPMS 27:1, LPMS 24:1) was adequate to avoid significant yield losses. In the second and third year following the PPMS applications, there was a tendency for positive residual effects on the total dry matter yield of grass ley, which could be attributed to slow mineralization of sludge-N. The application of LPMS increased the pH in surface soil by 0.5–0.7-units and Ca concentration by 240–660 mg L−1 of soil relative to the non-amended control over the study period. In the year of PPMS applications, the amendments produced a significant increase (about 2.0 g kg−1) in the total carbon (C) concentrations in the uppermost 10 cm soil layer relative to the non-amended soil. During the following years, the change in soil C was no longer measurable, indicating relatively fast decomposition of sludge-C. Saturated hydraulic conductivity tended to be 1.4 to 2.3 times higher in the PPMS-treated soils than in the non-amended soil. Except for the decline in readily plant-available water, the other common water retention parameters were not significantly affected by the PPMS amendments. There were significant positive treatment effects on the amount of water retained between −13 and − 316 kPa matric potentials, suggesting an increase in medium-sized pores contributing to water storage in the soil. To maintain or enhance the beneficial direct and indirect effects of PPMS on crop yields and soil physico-chemical properties, repeated applications of PPMS are required, possibly combined with the use of organic fertilizers, especially during grass ley years.

Simulated erosion of A horizon influences the dissolved organic matter chemodiversity and carbon sequestration of B horizon in Mollisols

Erosion of the A horizon of Mollisols is expected to change the dissolved organic matter (DOM) chemodiversity in the underlying B horizon. Three simulated erosion treatments, which had an A horizon of 30, 20, and 10 cm depth, were established for 9 years under a corn-soybean rotation on Mollisols. Compared to the A horizon that was 30 cm deep, the 20 cm treatment had 24–63% more dissolved lignin-like compounds, a significant increase, in the 0–10, 10–20, and 20–30 cm layers of the B horizon. When the A horizon was 10 cm deep, 41% more lignin-like compounds accumulated in the 10–20 cm layer of the B horizon and 22% more lignin-like compounds were detected in the 20–30 cm layer of the B horizon. Relative to the A horizon of 30 cm depth, the 20 and 10 cm treatments reduced the lipid- and protein-like compounds by 69–87% in 10–20 and 20–30 cm layers of the B horizon layers. Labile compounds increased in the 0–10 cm layer of the B horizon but decreased in the 10–20 and 20–30 cm layers of the B horizon. The DOM degradation degree, expressed in terms of the degradation index and Gibbs free energy, were related to the lignin accumulation, indicating that lignin, a recalcitrant compound, was degraded. Notably, variations in DOM chemodiversity in eroded Mollisols were primarily controlled by soil physicochemical properties and not microbial traits. Therefore, eroded Mollisols have less carbon sequestration potential in the B horizon. To prevent soil deterioration in corn-soybean rotations, we recommend to incorporate a combination of organic and mineral fertiliser to a 20–30 cm soil depth in erosion-susceptible Mollisols.

Precipitation Patterns and Their Role in Modulating Nitrous Oxide Emissions from Arid Desert Soil

Nitrous oxide (N2O) ranks as the third most significant greenhouse gas, capable of depleting the ozone layer and posing threats to terrestrial ecosystems. Climate change alters precipitation variability, notably in terms of frequency and magnitude. However, the implications of precipitation variability on N2O emissions and the underlying mechanisms remain inadequately understood. In this study, employing laboratory incubation methods on three representative sandy soil types (sandy soil, shrub soil, and crust soil), we examined the impacts of diverse precipitation levels (5 mm and 10 mm) and frequencies (7 days and 14 days) on N2O emissions from these soil types. This study aims to clarify the complex connections between soil N2O emission fluxes and soil physicochemical properties in the soil environment. Our findings reveal that the N2O emission flux exhibits heightened responsiveness to 5 mm precipitation events and a 14-day precipitation frequency, and compared to other treatments, the 5 mm precipitation and 14-day precipitation frequency treatment resulted in a 20% increase in cumulative nitrous oxide emissions. Consequently, cumulative N2O emissions were notably elevated under the 5 mm precipitation and 14-day precipitation frequency treatments compared to the other experimental conditions. The N2O emission flux in sandy soil displayed a positive correlation with available phosphorus (AP) and a negative correlation with pH, primarily attributed to the exceedingly low AP content in sandy soil. In shrub soil, the soil N2O emission flux exhibited a significant positive correlation with NH4+-N and a negative correlation with NO3−-N. Conversely, no significant correlations were observed between soil N2O emission flux and soil physicochemical properties in crust soil, underscoring the importance of considering plant–soil microbial interactions. Our findings suggest that soil nitrous oxide emissions in arid and semi-arid regions will be particularly responsive to small and frequent rainfall events as precipitation patterns change in the future, primarily due to their soil physicochemical characteristics.

Assessment of Soil Physico-Chemical Properties after Conversion of Sand Dunes into Arable Land in Hot Semi-Arid Climatic Conditions of Punjab

Assessment of Soil Physico-Chemical Properties after Conversion of Sand Dunes into Arable Land in Hot Semi-Arid Climatic Conditions of Punjab

Research on heavy metal enrichment and transportation in tea plant-soil systems of different varieties.

This study aimed to investigate heavy metal enrichment in different tea plant varieties and their distribution within different plant parts and to clarify the behavioral characteristics of heavy metals in the tea tree-soil system and their influencing factors. In this study, soil samples were collected from the root zones of 13 tea tree varieties in Guizhou, which had been planted for 10years. The aim was to compare the physicochemical properties of tea plantation soils under soil-forming matrixes and consistent management. Additionally, the study investigated the enrichment and transportation patterns of Cd, Cr, Cu, Pb, Zn, and Ni in the tea tree-soil systems of different tea tree varieties. The results showed that the planting of tea trees decreased the soil pH by 0.5; soil nutrients decreased; soil Pb, Cr, Ni, Cu, and Zn contents in the root zone increased; and Cd content decreased. Heavy metals were mainly enriched in the roots, and Zn, Cu, Ni, and other elements related to the protein and enzyme synthesis of tea trees could be mostly transported to the stems and leaves. There were significant differences in the enrichment and transportation of heavy metals among the different tea tree varieties. Under consistent soil-forming parent material, soil pH, organic matter, nutrients, and other indices only had a significant effect on heavy metal enrichment in the tea tree roots. Therefore, in areas with high background soil heavy metal contents, the construction of tea plantations should be based on regional soil environmental conditions to choose tea tree varieties with low heavy metal enrichment capacities to avoid the risk of high background soil heavy metals on the safe production of tea for consumers.