Soil Surface Area Research Articles

Surface liming combined with the use of monoammonium phosphate and elemental sulphur in a no‐till wheat–soybean cropping system

AbstractTropical and subtropical soils typically have high acidity and limited nutrient availability. Surface liming under no‐till systems ameliorates topsoil acidity in the short term, but it is generally slow to neutralize subsoil acidity. A field experiment was conducted in the period from 2016 to 2021 in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the effects of surface application of lime combined with the use of monoammonium phosphate (MAP) and elemental S on soil acidity, root growth, plant nutrition and grain yields of wheat (Triticum aestivum L.) and soybean (Glycine max. [L.] Merr.) under no‐till. Treatments consisted of a control (no amendments), surface lime (SL), SL + MAP and SL + MAP + elemental S. Applying lime to the soil surface increased soil pH, exchangeable Ca2+ and Mg2+ contents and base saturation, as well as reducing Al3+ content and Al3+ saturation throughout the soil profile. Such effects were more pronounced in the 0–10 cm layer and occurred to a lesser extent in the 10–100 cm layers. The addition of MAP or MAP + elemental S did not improve the effectiveness of surface liming in alleviating soil acidity throughout the soil profile. The root length per soil surface area to a depth of 100 cm exhibited a strong correlation with wheat yield, but not with soybean yield. Surface liming increased wheat yield by 40% and when lime application was combined with MAP + elemental S, the increase in wheat yield reached 74%. Surface liming resulted in a 36% increase in soybean yield, regardless of the use of MAP and elemental S. Thus, surface application of lime was effective in reducing soil acidity to a 100‐cm depth, regardless of fertilizer application with MAP and MAP + elemental S. The improving effects of surface liming had a more favourable impact on wheat root growth than on soybean root growth, probably because wheat was more affected than soybean by insufficient rainfall during the crop development cycle. Wheat showed a greater yield response to P and S fertilizer application than soybean.

Passive revegetation limited by seed availability in a salt marsh sediment addition site

Many approaches to restoring salt marsh habitats assume flora will naturally colonize the restoration site following the reinstatement of tidal hydrology that is appropriate for halophytes. However, this passive strategy can fail to meet restoration targets because of unfavorable site conditions and/or limited propagule dispersal. This study analyzes propagule availability in a restored southern California salt marsh that experienced slow passive revegetation following sediment addition to combat subsidence‐driven habitat loss. We performed a seedling emergence experiment to assess the quantity and species composition of viable halophyte seeds in the restoration site compared to nearby established salt marsh habitat. Additionally, we irrigated seed bank samples with freshwater or saltwater to test the effects of restoration site salinity conditions on seedling emergence and survival. Due to the proximity of the restoration site to seed sources, we expected to find ample seeds within its seed bank. However, only two seedlings emerged from restoration site seed bank samples (collected over 1.18 m2 of soil surface area), compared to an average of 44.33 seedlings from control site samples. Control site samples receiving saltwater irrigation had similar quantities of seedlings emerge, but seedlings in salt water had a reduced survival rate compared to seedlings in the freshwater treatment. Overall, these results suggest that passive restoration should be paired with techniques that retain seeds, such as increasing the topographic complexity of the restoration site. However, in scenarios where salinity or elevation may limit seedling recruitment, active planting should be considered to speed restoration trajectories.

Texture and Contamination-Level Dependent Effects of Calcium-Rich Deinking Paper Sludge Biochar on Soil Cd Availability, Enzymatic Activity, and Plant Stress Mitigation

The study evaluated calcium-rich deinking paper sludge (DPS) biochar's capability as a viable alternative method to mitigate soil cadmium (Cd) availability. Our analysis of 68 recent studies showed that 75% of the studies focused on contamination levels below 10 mg kg-1. However, mining and smelting areas exhibit higher levels of Cd contamination (mean value of 57.5 mg kg-1 with a CV of 128%), necessitating a contamination rate-dependent approach.Clay loam (CL) and sandy loam (SL) soils were artificially contaminated with Cd to mimic polluted areas (20, 40, 80 mg kg-1). Soils were aged for six months and then treated with DPS biochar doses of 0%, 1%, and 3% (w/w) for a month. Cd extractability and toxicity were gauged using diethylenetriaminepentaacetic acid extraction and plant physiology tests. Supplementarily, machine learning algorithms were tested to predict plant physiological parameters and biomass production, leveraging variables from principal component analysis and design parameters.Biochar application (3%, w/w) reduced soil Cd availability (20.1% in SL, 8.4% in CL; p < .05), attributed to increased soil pH, enhanced microbial activity, and expanded soil surface area. The plants grown in treated soils displayed increased dry matter content, chlorophyll, relative water content, and decreased malondialdehyde levels. The impact varied, being more pronounced in SL soils with high Cd contamination.This study presents the first report on the use of DPS biochar in Cd-contaminated soils and sets expectations for its outcomes regarding plant physiology and soil microbial activity in a diversified experimental design. DPS biochar appeared as a tool for mitigating soil Cd availability and alleviating plant stress particularly in SL soils. The biochar's efficiency was influenced by its dose, the level of contamination, and the soil type, highlighting the importance of tailored application strategies.

Strategies and mechanisms for improving the detection accuracy of nonextractable residues of polycyclic aromatic hydrocarbons in soils

The methods that can accurately measure the concentrations of nonextractable residues (NERs) of hydrophobic organic contaminants (HOCs) in soil are still lacked in current studies. In this study, three methods, namely methanolic saponification treatment (MST), silylation treatment (ST), and acid deashing treatment (ADT), were investigated and then combined to extract the NERs of six types of polycyclic aromatic hydrocarbons (PAHs) from nine soil samples. The NER concentrations of PAHs obtained by ST (2.43–521.73 ng g−1) were comparable to or significantly higher than those obtained by MST (1.94–291.54 ng g−1), owing to the properties of soil and target compounds. Additionally, ADT could further release a considerable amount of PAH NERs (0.39–276.99 ng g−1) from the soils that had been treated with ST. The mechanism was that acid solution dissolved mineral components, significantly increasing the pore size of the soil matrices from 9.37–15.57 nm to 17.11–27.51 nm. The average percentage of each PAH obtained by ADT (the ratio of the amount obtained by ADT to the total NER content) exhibited a negative correlation with their ring numbers (R2 = 0.62, p < 0.05), whereas the percentage of targets recovered through ST increased linearly with their log KOW values (R2 = 0.75, p < 0.05). Moreover, there is a positive correlation (R2 = 0.73, p < 0.05) between the NER percentages of phenanthrene (obtained by ST–ADT) and the specific surface areas of soils, and the NER percentages of benzo(g,h,i)perylene is positively correlated to the content of total organic carbon (R2 = 0.62, p < 0.05). These results suggested that the amounts and locations of NERs were influenced by both the physicochemical characteristics of PAHs and soils. These findings provide some basic understandings of the entrapped mechanisms of PAH NERs, helping to establish strategies for improving their detection accuracy.

Creation of the Route of Bamboo, a Contribution to Net Zero by 2050 in Vietnam

The Phu An bamboo village, created in 1999, maintains over 200 taxa of living bamboo, collected in Viet Nam, Laos and Cambodia, and was awarded the UNDP Equatorial Prize in 2010. This ex situ conservation not only provides data for basic research and preserves biodiversity resources, but also contributes to actions on CO2 to reduce the greenhouse effect in climate change and create sustainable livelihoods for the community. From the Phu An Bamboo village, the "Bamboo Route" has been built since 2016 from the north to the south of Viet Nam, with the aim of multiplying bamboo in situ conservation sites, associated with research programs and public awareness actions on the importance and environmental benefits of bamboos. Along the bamboo route, an ex situ conservation site has been developed at Dong Thap with plants of 67 different vernacular species, another at Phan Rang, in the arid region, with 62 species, and a third at Dak Nong, where the climate is more favourable, with 12 different vernacular species from the in situ conservation site at Chieng Ban, Son La, where 19 vernacular species have been recorded. Thanks to its fast-growing characteristics and large biomass production, bamboo plays an important role in carbon sequestration. Research to mesure CO2 absorption was done in three different habitats on three different bamboo species. The CO2 absorption capacity of Bambusa blumeana Schultes in Gao Giong, Dong Thap province, indicates an important role of this thorny bamboo under climate change conditions. On the " Route of Bamboo", we studied also the surface area of bare soil from north to south, except in the Mekong Delta, we can plant more than 200,000 ha of thorny bamboo to complete the existing surface area of 1.5 million ha which could contribute 30% of Viet Nam’s CO2 absorption. This enables us to estimate how planting 50% of these areas could contribute to Viet Nam’s Net 0 2050 target.

Smartphone-based spectroscopy as a tool to estimate soil attributes for the citizen science concept

This study explores the potential of using smartphone cameras to estimate soil attributes as a field-based alternative to traditional sampling and lab analyses that are time-consuming, expensive, and non-friendly to the environment. It aims to investigate whether the color information captured by smartphone cameras could provide spectral information that can be utilized for soil attribute estimation using regression techniques. The DN values from smartphone camera photos were transformed into reflectance using colored plastic plated marker (PPM) reference panels. The spectral information of the PPM keys, obtained using a laboratory spectrometer, was convolved into 3 RGB smartphone bands. Using the legacy soil spectral library (SSL) of Israel on the 3-reflectance calibrated RGB smartphone bands, a good agreement with the reflectance of the laboratory spectrometer was obtained. The soil properties were modeled with the converted reflectance using the multiple linear regression (MLR), partial least square regression (PLSR), and ridge regression (RR) algorithms. The models created using the smartphone data (RGB and 6 synthetic bands) predicted six soil properties: i.e., soil organic matter (OM%), CaCO3, free iron oxides (Fe-dithionite), Al2O3, soil surface area (SSA), and hygroscopic moisture with the coefficient of determination (R2) values of 0.58, 0.54, 0.60, 0.55, 0.55 and 0.64, respectively. The quality of predictions was also evaluated using root mean square error (RMSE) and the ratio of prediction to interquartile distance (RPIQ). This research provides the results of an experiment to convert a personal smartphone camera to a spectrometer with the help of SSL. Despite the low spectral resolution of smartphone cameras, the models achieved fair results in predicting six soil properties. These findings could promote the adoption of citizen science methodologies for sustainable soil management as smartphone devices that are available to all can be simply calibrated to reflectance and used for proximal sensing of soils.

Quantitative Evaluation of Suspended Solid Runoff from Large-Scale Landslide Areas Presumed to Be the Source of Turbid Water

In the uppermost stream of the Mimikawa River, in northern Miyazaki Prefecture, the contribution to river turbidity of a huge, collapsed slope alternating sandstone and mudstone layers was qualitatively shown in our previous study. In this study, the water level and turbidity were continuously observed, to obtain a quantitative estimation of this contribution. The conversion equation from the water level to the flow rate is required, but field measurements during the flooding term in the mountainous site are difficult. In this study, a high-resolution survey was conducted, and the relationship was determined via a small-scale hydraulic model shaped using a 3D printer from the survey results, to determine the relationship between the water level and the flow rate. The flow rate time series was reproduced with the distributed runoff model that is verified with the flow rate converted from the water level. The flow rate and turbidity load time series were also estimated from the long-term rainfall. The area of the bare soil surface of each small basin was obtained via satellite image analysis, and the soil yield from each surface condition was calculated. Furthermore, the amount of turbidity produced upstream of Kamishiiba Dam was calculated for each small basin. It was estimated that 24% of the turbidity was generated from the small basin covering 5.7% of the total catchment area. This study showed that it is possible to verify the hydrological model by obtaining the water-level–discharge relationship, even in the mountains, where it is difficult to observe the discharge on-site, via small-scale hydraulic model experiments.

Effect of soil hydrophobicity on soil-water retention curve of a silt loam soil

Soil wettability is an important property that affects the behaviour of fine-grained soils. Previous studies have shown that hydrophobicity induced by organic or silane additives may affect the soil-water retention curve (SWRC). However, current findings regarding the effect of hydrophobicity on the SWRC are controversial. Previously, organic or silane additives were assumed to change only the soil wettability. Nevertheless, this study shows that polyvinyl alcohol (PVA) can change the hydrophobicity, pore size distribution (PSD), and specific surface area (SSA) of soil, thus affecting the SWRC. PVA-treated soil is hydrophobic when cured at 20 ℃, but hydrophilic when cured at 100 ℃. No thermal degradation is indicated in the PVA at 100 ℃ based on thermogravimetric analysis and a comparison of mass loss, and the sole difference between the PVA-treated soils cured at 20 and 100 ℃ is their wettability. This study managed to make the hydrophobicity caused by PVA to become an independent variable separated from the PSD and SSA by controlling the ambient temperature. The wetting and drying curves are measured under isopiestic humidity control in the high-suction domain (2.7–298.7 MPa), whereas pressure plates are used for the drying curves in the low-suction domain (0–800 kPa). The results obtained indicate that soil hydrophobicity significantly accelerates drainage when the matric suction is between 100 and 400 kPa, and an increase in PVA content increases the water retention capacity of soil. When the matric suction exceeds 2.7 MPa, the effect of soil hydrophobicity on the SWRC of the soil weakens. At this time, the SWRC is dominated by the van der Waals force, and the SSA contributes significantly to the process. Additionally, this study enables some controversial findings from previous studies to be explained, which is of great significance in soil and agriculture sciences.

The Influence of Organic Matter on Phosphorus Fixation in Soils from the Eastern Flank of Mount Cameroon

The maximum phosphate fixation (KF) and phosphorus sorption capacity (PSC) of soil samples collected from the surface and sub-surface horizons of five volcanic soil profiles from the eastern flank of Mount Cameroon were investigated before and after organic matter removal. The aim of this research was to investigate the influence of soil organic matter (OM) on phosphorus (P) fixation. The removal of soil OM from the soil samples was accomplished by the use of sodium hypochlorite. Phosphorus fixation studies were performed on the treated and untreated soil samples using calcium chlorite as the background electrolyte. Fixation data were interpreted with Freundlich adsorption isotherm. The results indicated that the removal of OM had an influence on both KF and PSC. Removal of soil OM decreased PSC and increased KF for all soils. The inhibition of aluminium oxide and the reduction of soil surface area after the removal of OM were the justifications for the increase in P fixation.

Impacts of snow-farming on alpine soil and vegetation: A case study from the Swiss Alps

Snow-farming is one of the adaptive strategies used to face the snow deficit in ski resorts. We studied the impact of a shifting snow-farming technique on a pasture slope in Adelboden, Switzerland. Specifically, we compared plots covered by a compressed snow pile for 1.5, 2.5 or 3.5 years, which then recovered from the snow cover for three, two or one vegetation seasons, respectively, with control plots situated around the snow pile.In plots with >1.5 years of compressed snow pile, plant mortality was high, recovery of vegetation was very slow, and few plant species recolonized the bare surface. Soil biological activity decreased persistently under prolonged snow cover, as indicated by reduced soil respiration. The prolonged absence of fresh plant litter and root exudates led to carbon (C) limitation for soil microbial respiration, which resulted in a significant decrease in the ratio of total organic carbon to total nitrogen (TOC/TN) under the snow pile.Microbial C, nitrogen (N) and phosphorus (P) immobilization decreased, while dissolved N concentration increased with compressed snow cover. Longer snow cover and a subsequent shorter recovery period led to higher microbial C/P and N/P but lower microbial C/N. Nitrate and ammonium were released massively once the biological activity resumed after snow clearance and soil aeration.The soil microbial community composition persistently shifted towards oxygen-limited microbes with prolonged compressed snow cover. This shift reflected declines in the abundance of sensitive microorganisms, such as plant-associated symbionts, due to plant mortality or root die-off. In parallel, resistant taxa that benefit from environmental changes increased, including facultative anaerobic bacteria (Bacteroidota, Chloroflexota), obligate anaerobes (Euryarchaeota), and saprophytic plant degraders.We recommend keeping snow piles in the same spot year after year to minimize the area of the impacted soil surface and plan from the beginning soil and ecosystem restoration measures.

Effects of tea oil camellia (Camellia oleifera Abel.) shell-based organic fertilizers on the physicochemical property and microbial community structure of the rhizosphere soil.

Soil microorganisms play important roles in promoting soil ecosystem restoration, but much of the current research has been limited to changes in microbial community structure in general, and little is known regarding the soil physicochemical property and microbial community structure. In this study, four organic fertilizers were first prepared based on tea oil camellia shell (TOCS). Our findings indicate that the application of BOFvo increased both total pore volume and BET surface area of the rhizosphere soils, as well there was a remarkable enhancement in total organic matter (TOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), total potassium (TK), and available potassium (AK) contents of the rhizosphere soils. Meanwhile, in comparison to the CK and CF groups, the utilization of BOFvo led to a substantial increase in both average yield and fruiting rate per plant at maturity, as well resulted in a significant increase in TN and TP contents of tea oil camellia leaves. Furthermore, our findings suggest that the application of TOCS-based organic fertilizers significantly enhances the microbial diversity in the rhizosphere soils with Proteobacteria and Ascomycota being the dominant bacterial and fungal phyla, respectively, and Rhodanobacter and Fusarium being the dominant bacterial and fungal genus, respectively. Redundancy analysis (RDA) indicates that the physicochemical characteristics of TOCS-based organic fertilizers had a significant impact on the composition and distribution of microbial communities in the rhizosphere soils. This study will facilitate the promotion and application of TOCS-based organic fertilizers, thereby establishing a foundation for the reuse of tea oil camellia waste resources.

Specific surface area of soils with different clay mineralogy can be estimated from a single hygroscopic water content

The soil specific surface area (SSA) is an important variable for soil science and geoenvironmental engineering applications, but traditional measurement methods are difficult and time-consuming. Regression models or pedotransfer functions are often used to estimate SSA from other soil properties (e.g., clay content and cation exchange capacity), but these models do not consider the impact of clay mineralogy. Hygroscopic water content (wh) is intimately linked to these soil properties, which suggests that wh may be a better parameter for SSA estimation. This study (i) proposes regression models that estimate SSA from wh at different relative humidity values (5 to 90%) for kaolinite-rich samples (KA), illite-rich or mixed clay samples (IL/MC), montmorillonite-rich samples (ML), and a combination of all samples (ALL) and (ii) compares the performance of the wh models to other published models that comprise clay, silt and soil organic carbon contents and cation exchange capacity. We found that the sample-specific wh regression models accurately estimated SSA for KA, IL/MC and ML samples. For KA and IL/MC samples, the performance of the KA model (e.g., for adsorption, average RMSE = 10.5 m2/g) and IL/MC model (average RMSE = 21.3 m2/g) were better than the ALL-calibration model (KA: average RMSE = 18.7 m2/g; ML: average RMSE = 22.4 m2/g). For ML samples, similar model performance between the ML-calibration model (average RMSE = 41.4 m2/g) and the ALL-calibration model (average RMSE = 41.1 m2/g) was observed. In addition, the model performance of regression models based on wh was superior to models published in the literature that are based on clay, silt and soil organic carbon contents and cation exchange capacity. Overall, this study confirms that a single measure of wh can provide reliable estimates of the SSA while revealing a significant impact of clay mineralogy on model performance.

Hydrological setting controls 137Cs and 90Sr concentrations in a headwater catchment in the Chornobyl Exclusion Zone

Concentration-discharge relationships are widely used to understand the hydrological processes controlling river water chemistry. This study investigates how hydrological processes affect radionuclide (137Cs and 90Sr) concentrations in surface water in headwater catchments within the Chornobyl Exclusion Zone (ChEZ) in Ukraine. In the flat wetland catchments, the depth of the saturated soil layer changes little throughout the year, but changes in the saturated soil surface area during snowmelt and immediately after rainfall affect water chemistry by changing the opportunities for contact between the surface water and the soil surface. On the other hand, in the slope catchments where there are few wetlands, the water chemistry of river water is governed by changes in the relative contributions of “shallow water” and “deep water” due to changes in the catchment water supply pathways feeding the rivers. In this study, no correlations were observed between dissolved or suspended 137Cs concentrations and either discharge rates or competitive cations, but the solid-liquid ratio of 137Cs was found to be significantly and negatively correlated with water temperature. However, 90Sr concentrations in surface water were found to be strongly related to the water pathways for each of the catchments. Moreover, contact between the surface water and the soil surface and changes in the relative contributions of shallow and deep waters to stream water were correlated with changes in 90Sr concentrations in surface water in wetland and slope catchments, respectively. The study concludes that 90Sr in rivers inside the ChEZ are strongly affected by the water pathways in headwater catchments. Additional studies will be necessary to clarify the details of sorption/desorption reactions.

Effects of microplastics on the water characteristic curve of soils with different textures

Microplastic (MP) pollution in the soil severely damages the soil structure and affects the soil water-holding property, thereby affecting the soil water characteristic curve (SWCC). After polyethylene MP (PE-MP) addition at three concentrations (0.5%, 1%, and 2%) under three particle sizes (150 μm, 550 μm, and 950 μm) and two soil textures (sandy soil and loamy soil), SWCCs were measured and fitted with the van Genuchten model. The soil pore structure characteristics were obtained based on CT scanning combined with soil pore three-dimensional reconstruction to quantitatively analyze the relationships between MP properties and soil structure and the SWCC. Low concentrations (0.5%) of PE-MPs did not significantly affect the soil water content, while the accumulation of PE-MPs at a high concentration (2%) strongly affected the soil water-holding property, with small PE-MPs (150 μm) exerting significantly positive effects on the water-holding capacity of loamy soil and 950-μm MPs reducing the soil water content more strongly in sandy soil. The contributions of MP properties and soil textures to the SWCCs differed, and the impact of soil texture on the SWCCs was significantly higher than those of MP concentrations and particle sizes. Differences in MP occurrence characteristics and soil textures also led to variations in the fitted hydraulic parameters of the SWCCs. The addition of 2% 150-μm PE-MPs to loamy soil increased the soil porosity and surface area, while the addition of a higher concentration of large PE-MPs (2%, 950 μm) to sandy soil reduced soil porosity and circularity. This is related to the addition of a large number of small MPs, which may adsorb and bind many smaller soil particles to form larger, water-stable agglomerated structures, while the addition of high concentrations of large MPs in sandy soils may be related to the destruction of the original capillary pore structure of sandy soils and the weakening of soil capillarity. This study provides a theoretical basis for agroecological risk assessments.

Antarctic permafrost degassing in Taylor Valley by extensive soil gas investigation

Ongoing studies conducted in northern polar regions reveal that permafrost stability plays a key role in the modern carbon cycle as it potentially stores considerable quantities of greenhouse gases. Rapid and recent warming of the Arctic permafrost is resulting in significant greenhouse gas emissions, both from physical and microbial processes. The potential impact of greenhouse gas release from the Antarctic region has not, to date, been investigated. In Antarctica, the McMurdo Dry Valleys comprise 10 % of the ice-free soil surface areas in Antarctica and like the northern polar regions are also warming albeit at a slower rate.The work presented herein examines a comprehensive sample suite of soil gas (e.g., CO2, CH4 and He) concentrations and CO2 flux measurements conducted in Taylor Valley during austral summer 2019/2020. Analytical results reveal the presence of significant concentrations of CO2, CH4 and He (up to 3.44 vol%, 18,447 ppmv and 6.49 ppmv, respectively) at the base of the active layer. When compared with the few previously obtained measurements, we observe increased CO2 flux rates (estimated CO2 emissions in the study area of 21.6 km2 ≈ 15 tons day−1). We suggest that the gas source is connected with the deep brines migrating from inland (potentially from beneath the Antarctic Ice Sheet) towards the coast beneath the permafrost layer. These data provide a baseline for future investigations aimed at monitoring the changing rate of greenhouse gas emissions from Antarctic permafrost, and the potential origin of gases, as the southern polar region warms.

Contribution of organic carbon to the total specific surface area of soils with varying clay mineralogy

Soil specific surface area (SA) reflects the quantity and quality of the soil mineral and organic fractions. For soil samples that have similar clay mineral types, clay content and or organic carbon (OC) contents are good predictors of SA. However, the magnitude of the OC contribution to SA for different soil types is unclear, particularly since SA varies depending on which method or probe molecule is used to measure it. Consequently, we set out to (i) quantify the contribution of soil OC to total SA for soils with varying clay mineralogy, and (ii) assess the effect of probe molecule (EGME or H2O) and water sorption direction on the contribution of OC to the total SA. We utilized 330 soil samples (clay = 1 to 89 %; silt = 2 to 78 %; OC = 0.03 to 34.9 %) that were grouped according to clay mineralogy and OC content. The total SA was measured using EGME adsorption (SAE) and water adsorption and desorption (SAH2O). The contribution of OC to SA was examined using regression and partial correlation analyses that combined clay, silt, and OC as explanatory variables. Results showed that SAE values were strongly correlated to SAH2O, except for OC-rich soils where SAE was significantly lower than SAH2O. Apart from montmorillonite-rich samples, OC contribution to SAE was smaller than for SAH2O. Organic carbon had a positive contribution to desorption SAH2O for all sample groups, except for montmorillonite-rich samples; OC contribution was 7.5, 10.7, and 13.9 m2/g per %C for illite-rich, kaolinite-rich and OC-rich samples, respectively. There was no significant effect of water sorption direction on the OC contribution to SAH2O. Partial correlation analyses that accounted for clay and silt contents confirmed a negative contribution of OC to SAE or SAH2O for soil samples dominated by montmorillonite clay minerals. We can conclude that for the soil types investigated here (except montmorillonitic soils), OC has a positive contribution to total SA, and the magnitude of the contribution depends on the clay type.

Characterization of polycyclic aromatic hydrocarbons in soil in a coal mining area, East China: Spatial distribution, sources, and carcinogenic risk assessment

The polycyclic aromatic hydrocarbon (PAH) pollution process in mining areas, particularly coal mining areas, has accelerated because of coal chemical production and gangue accumulation. In this study, PHAs concentrations in surface soil was determined via gas chromatography–mass spectrometry. The composition, spatial distribution and sources of PAHs were analyzed, and their potential carcinogenic risks were evaluated.Results showed a wide PAH concentration range (218–1548 ng g−1). The high molecular weight proportion in contaminated areas was significantly higher than in uncontaminated areas. Clear differences in PAH distribution were detected in contaminated areas, with higher concentrations in the soils near an industrial park and coal gangue piles. The results of positive matrix factorization (PMF) in contaminated area revealed that coking, oil and biomass combustion, and vehicle emissions and coal combustion, contributed 31%, 26%, 24%, and 19%, respectively, to the detected PAHs. In contrast with the 10% contribution rate of the coking source in uncontaminated areas. The Monte Carlo method was used to assess the cancer risk to residents in the study areas. The carcinogenic health risk values for adults in the contaminated areas was higher than the safety standard (2.92 × 10−6) prescribed by the United States Environmental Protection Agency at 95% confidence level. Sensitivity analysis showed that the relative exposure duration (ED) and soil surface area of skin exposure were the most significant parameters for adults, and ED and body weight for children. The cancer risk for both adults and children in contaminated areas was five times than that in uncontaminated areas.

Modelling Water Consumption Efficiency Based on Perlis State Soil Series

Water is a limited resource for Perlis state. Domestically, meeting the water supply in the state requires improving the current supply facility and repairing water leakages in the supply system. However, an even more important aspect of water resources management is the water consumption from agricultural activities such as the over-irrigation in the crop field. This study identifies the soil series of Perlis state, determines its soil textures, estimates the field capacity, permanent wilting point, and plant available water. Additionally, the water infiltration studies were carried out. Results showed there were ten soil series present in the state, and this soil can be categorized by four soil textures that the clay soil texture dominates in seven soil series. Fully saturated soil in the Perlis state potentially losses 27-56% of its soil moisture content drains by gravity, which is unavailable to crop consumption, hence, wastage. An estimated 1.7 x 10-4 to 2.1 x 10-3 m/s water infiltration rate over the soil depths from 0.15-1.5 m. Knowing the soil surface area for the crop field allows the estimate of water volume needed in a unit time needed for storage tank estimation and distribution system designs. The water requirement increases by including the water evaporation rate into the water infiltration rate.

Protective Effects of Systiva® Seed Treatment Fungicide for the Control of Winter Wheat Foliar Diseases Caused at Early Stages Due to Climate Change

Foliar fungal diseases are a serious threat to winter wheat production and climate change appears to favor pathogens associated with leaf blotch and tan spot symptoms in the Mediterranean area. The present work aimed to highlight these risks and propose appropriate disease management strategies by evaluating the seed treatment with the Systiva® (BASF) fungicide as a means to protect the crop against foliar fungal infections during the early growing stages. Towards that aim, plant tissue symptoms affected by the pathogens Pyrenophora tritici-repentis and Septoria spp. were systematically recorded in a study field in the region of Larissa, central Greece for three years (2016–2018), and the findings were associated with the monthly weather anomalies. Consequently, for the growing period of 2021–2022, a field experiment was established in the same disease prone field, comparing different doses of the seed treatment with Systiva® fungicide against leaf blotch and tan spot diseases. The evaluation was made by visual disease assessments, remote sensing with an unmanned aerial vehicle (UAV) and metagenomics analysis. Parallel measurements on straw residues were also made to characterize the plant residues perithecia (pseudothecia). Visual leaf disease assessments and UAV remote sensing data showed that Systiva® treatments at doses of 125 cc and 150 cc per 100 kg of wheat seed can reduce the percentage of infected wheat plants caused by foliar fungal pathogens at wheat growth stages GS23-25 and GS30-31. Moreover, the metagenomics analyses performed on the microbial communities revealed that Systiva® can decrease the degree of infection by P. tritici-repentis and Z. tritici but do not provide sufficient protection against P. nodorum. Foliar diseases were influenced by the soil surface area covered with straw residue with a high proportion of natural inoculum (pseudothecia/ascospores).

ROOT DISTRIBUTION OF MATURE OIL PALMS IN MINERAL AND PEAT SOILS AND ITS IMPLICATION ON FERTILISER PLACEMENT

The correct placement of fertilisers is critical, as losses can be very significant especially in regions of high and frequent rainfall, non-terraced slopes, sandy textured soils and peat. To maximise uptake efficiency, fertilisers should be evenly broadcast over the soil surface area that contains the highest density of feeder roots. In order to determine the latter, an investigation was undertaken to ascertain the biomass and distribution of roots of various ages of mature oil palms planted in both mineral and second generation peat soils. Results of the study indicate that if site factors are not limiting, palm age and past fertiliser placement history are two major factors influencing oil palm root development and distribution. In mature well decomposed peat, although roots could be found growing 4 m from palm bole, actual root biomass per unit volume of soil was low. Only 21 per cent of the feeder roots of 8-year-old palms were found growing outside the weeded palm circles (WPC). Even within the latter, approximately 50 per cent were concentrated within a radius of 1 m from the palm bole. The low bulk density and high porosity of peat appears to discourage roots from growing beyond this distance. In mineral soils, there was a consistent and gradual increase in root spread beyond the WPC, with palm age. Feeder root distribution beyond a 2 m radius ranged from as low as 26 per cent in 6-year-old palms planted on terraces to 41 per cent for 8-year-old palms established in non-terraced soils. Only palms older than 10 years of age had root biomass greater than 50 per cent beyond this radius. In all sites, there was an increase in primary and secondary root biomass with soil depth and a linear decrease in feeder root biomass down the soil profile. Soil chemical analysis indicated that apart from palm age, the horizontal and vertical distribution of feeder roots was strongly influenced by soil fertility gradients created by past fertiliser placement history. As fertilisers were previously applied entirely in the WPC for younger palms (&lt;8 years), there was a significant decline in soil fertility with increasing distance from the palm bole and increasing soil depth. The majority of feeder roots were concentrated within the 2 m radius from the palm bole and in the top 20 cm of soil, where nutrient levels were the highest. In older palms (&gt;10 years) where fertilisers had been broadcast over frond heaps in the interpalm spaces and interrows, feeder root biomass was higher outside the WPC, as soil fertility gradients were less apparent. Taking into account the root distribution patterns of oil palm in relation to palm age, specific recommendations on fertiliser placement for oil palm grown on mineral and peat soils are made, so as to improve fertiliser uptake and utilisation.