Exchangeable Cations Research Articles

Acacia auriculiformis agroforestry fallows of different ages improve soil physico-chemical properties and carbon stocks on the Batéké plateau, Democratic Republic of Congo

Our study evaluated the effects of Acacia auriculiformis agroforestry fallows installed on impoverished sandy soils of the Bateke Plateau in the Democratic Republic of the Congo (DRC). We compared physico-chemical properties and carbon stocks of soils under 1 to 3, 3 to 5 and 5 to 7 yr-old Acacia auriculiformis fallows and 5 yr-old savanna fallows. Soils were collected at depths of 0–10 cm, 10–40 cm and 40–100 cm and analyzed for the following parameters: soil organic carbon (SOC), nitrogen (N), available phosphorus (P), exchangeable cations (Ca2+, Na+, K+, Mg2+), cation exchange capacity (CEC), pH (H2O and CaCl2), granulometry and bulk density. In general, results obtained showed that agroforestry fallows are superior to traditional fallows for most measured parameters. The presence of A. auriculiformis improves the chemical properties of the soils compared to savanna soils; soil C and N concentrations as well as cation exchange capacity (CEC) were higher (P < 0.0001) under agroforestry soils than under savanna soils, especially between 0 and 10 cm depth. Our results also showed that A. auriculiformis agroforestry fallows stored 1.5 times more soil carbon than savanna fallows between 0 and 100 cm depth with 75, 106, 114, and 106 Mg C ha−1 respectively for savanna, 1–3 years, 3–5 years, and 5–7 years fallow soils. However, establishment of A. auriculiformis agroforestry fallows resulted in a decrease in soil pH compared to savanna soils. Differences in age and depth of the agroforestry fallow soils did not influence the physico-chemical properties evaluated. Overall, our results show that the establishment of A. auriculiformis agroforestry fallow improves the physico-chemical properties and increases soil carbon stocks compared to traditional savanna fallow. Therefore, we suggest the scaling up of the A. auriculiformis agroforestry improved fallow as a soil regenerative agrotechnology in the tropics.

From site to state – Quantifying multi-scale legacy effects of historic landforms from charcoal production on soils in Connecticut, USA

Relict charcoal hearth (RCH) landforms are relatively small (average diameters of 11 m) and circular microrelief features found in many forests of the North-Eastern USA and Central Europe. Soils on RCHs are special in that they are significantly enriched in organic- (OC) and pyrogenic carbon (PyC), caused by the admixture of charcoal. Many studies have shown that this results in changed soil chemical and physical properties, making RCHs unique soil microhabitats. However, questions about their larger impact on a soil landscape’s carbon storage have hardly been studied so far; an aspect that could become more relevant with growing RCH site location databases. Here we show that RCHs can substantially add to a landscape soil organic- and pyrogenic carbon storage. This effect is scale dependent, i.e. a larger scale of observation (1:20,000) will result in significant additions for areas with high site densities (+22.6 % OC, +128.6 % PyC), contrary to smaller scales of observation (>1:650,000) where the effect is diminished (+0.2 % OC, +1.2 % PyC). A comparison with a nationwide soil database (gSSURGO) shows that in areas with high site densities, individual soil unit OC contents are increased by up to 91.6 %. An exemplary comparison to historic terrace/lynchet systems shows that RCHs store vastly more carbon when pedons of the same size are compared. However, if the actual landform surface areas are taken into account, RCHs store a lot less. This is showcasing the spot-like distribution of RCHs on a landscape scale. Furthermore, we broaden the knowledge about RCH site specific properties in Connecticut by a first analysis of pedogenic (hydr-)oxide and exchangeable cation concentrations, with the result indicating increased weathering rates and enrichment of exchangeable Ca2+, Mg2+ and Mn2+ in RCH soils.

Contributions of climate and soil properties to geographic variations of soil organic matter across the East Asian monsoon region

Soil organic matter (SOM) plays a crucial role in soil functions and the global carbon cycle. Considering the disconnection of research emphasis between soil and ecology, little is known about the large-scale edaphic controls and their interaction with climate in SOM dynamics. This study aimed to explore the geographic evolution mechanisms of SOM from the perspective of soil intrinsic properties. A wide range of soil types from quaternary sediments were sampled from three ecosystems (forest, grass, and arable lands) and at different pedogenic horizons along the mid-temperate to tropical climate gradient in the East Asian monsoon region. SOM was measured in terms of organic carbon (SOC, 0.06–4.81 %), total nitrogen (TN, 0.04–0.41 %), and their ratio (C/N ratio, 1.17–12.26), as well as a series of soil properties: porosity, soil texture, clay mineralogy, exchangeable cations and soil aggregation. The indicators of SOM were most influenced by soil horizon (F=233.2–2375.2), followed by soil type (F=84.0–924.1, p < 0.001) and land use (F=4.7–92.2, p < 0.05); SOC, TN and C/N ratio overall decreased with increasing soil depth, and exhibited decrease first and then increase from north to south. Traditional predictors of soil texture and climate variables independently contributed little to SOM (p > 0.05). In contrast, bulk density had the greatest explanatory power (R2 = 0.379, p < 0.01), followed by soil aggregation (p < 0.05), while phyllosilicate minerals and iron oxides explained significant but small variances, all of which were climate-dependent. SOM could be jointly explained by soil properties (0.665) and climate (0.220) with an interaction effect of 0.152, among which bulk density, percentage of aggregate disruption, and mean annual temperature (MAT) were the most powerful predictors with negative effects. Structural equation modeling results indicated that MAT could influence SOM through soil aggregation and exchangeable cations. This study unravels the direct and indirect effects of climate on SOM and highlights the predominant roles of soil structural properties rather than abiotic primary agents at the regional scale, which merits consideration in improving SOM modeling and land management.

Assessing the Suitability of Sediment Soil to Be Reused by Different Soil Treatments for Forest Agriculture

In order to determine the suitability of reusing the sediment deposited in the upper part of the dam as soil for growing forest products, a total of eight treatment plots were formed by mixing cultivated soil, compost, and biochar with the sediment in a volume ratio. Generally, the soil fertility of SS100 was relatively lower than that of CS, with Av. P2O5 being only 22%. SS70 and SS50 increased soil physicochemical properties including OM, exchangeable cations, CEC, and BS by 1.1–2.9 times more than SS100, thus, A. scaber Thunb. treated in SS70 and SS50 showed increased photosynthetic parameters including A, Vcmax, Jmax, and the growth characteristics, especially in the aboveground part, were 20% and 31% higher than the SS100, respectively. Furthermore, A. scaber in CS, SS50, Bc10, and Comp had higher PIabs, DFIabs, and SFIabs while maintaining lower VK/VJ after 10 days of drought stress, Comp and Bc10, in particular, had a high Y(NPQ) and a low Y(NO). Bc5 and Bc10, revealed no discernible differences in soil physicochemical properties, nonetheless, A. scaber in Bc10 demonstrated relatively high drought tolerance. Overall, CS, SS50, and Comp had relatively well-balanced plant growth, and drought tolerance was found to be higher in CS, Comp, SS50, and Bc10, which is thought to have higher water-holding capacity and soil fertility. As a result, if appropriate treatment methods are established, such as mixing sediment soil with cultivated soil at a one-to-one ratio or adding compost, increase the public value of forests by promoting activities such as watershed conservation, soil runoff prevention, and reducing the financial burden associated with sustainable forestry management and SS50 is recommended as the most cost-effective method.

Evaluation of the Influence of pH on the Release of Exchangeable Cations from a Mixed Clay Mineral Deposit for Replenishment of Soil Nutrients

Soil nutrients consist of minerals such as Ca, Mg, K and Na ions among others which are essential to plant growth. Soils can become deficient in these nutrients on account of pollution, flooding and over cultivation. The soil condition can be ameliorated by addition of clay minerals which are rich in aforementioned cations. The mineralogy of the clay mineral was investigated using X-ray Diffractometer (XRD) and the effect of pH variation on the release of exchangeable cations of the clay mineral deposit were investigated by varying the pH of the solution in which the clay mineral was immersed whereas the amount of the cations released were determined using Atomic Absorption Spectrophotometer(AAS) and Flame Emission Spectrophotometer. Three clay minerals clinochlore, kaolinite and illite were detected. The quantity of cations released from the clay mineral varied with pH; and the pH at which the maximum quantity of the cations were released were pH4 for K+ ions(4.63±0.38cmol/kg), pH7 Ca2+ (12.09±0.96 cmol/kg) and Mg2+(3.48±0.08 cmol/kg) ions and pH8 for Na+(7.81±0.58 cmol/kg) ions respectively for site 1. This trend was observed in the three sites that were studied. This study has revealed that different pH conditions are required if this mixed clay mineral is to be employed in the remediation of nutrient deficiency in any soil in respect of a particular mineral.

Nitrogen addition increased soil particulate organic carbon via plant carbon input whereas reduced mineral−associated organic carbon through attenuating mineral protection in agroecosystem

Nitrogen (N) addition can have substantial impacts on both aboveground and belowground processes such as plant productivity, microbial activity, and soil properties, which in turn alters the fate of soil organic carbon (SOC). However, how N addition affects various SOC fractions such as particulate organic carbon (POC) and mineral−associated organic carbon (MAOC), particularly in agroecosystem, and the underlying mechanisms remain unclear. In this study, plant biomass (grain yield, straw biomass, and root biomass), soil chemical properties (pH, N availability, exchangeable cations and amorphous Al/Fe − (hydr) oxides) and microbial characteristics (biomass and functional genes) in response to a N addition experiment (0, 150, 225, 300, and 375 kg ha−1) in paddy soil were investigated to explore the predominant controls of POC and MAOC. Our results showed that POC significantly increased, while MAOC decreased under N addition (p < 0.05). Correlation analysis and PLSPM results suggested that increased C input, as indicated by root biomass, predominated the increase in POC. The declined MAOC was not mainly dominated by microbial control, but was strongly associated with the attenuated mineral protection (especially Ca2+) induced by soil acidification under N addition. Collectively, our results emphasized the importance of combining C input and soil chemistry in predicting soil C dynamics and thereby determining soil organic C storage in response to N addition in rice agroecosystem.

Comparative verification of Mehlich 3 soil analysis methods in Northern Mozambique using microwave plasma–atomic emission spectrometry

ABSTRACT Regular testing of nutrients in soil samples is important for understanding soil fertility. This study investigated a combination of the Mehlich 3 extraction method and Microwave Plasma-Atomic Emission Spectrometry (MP – AES) for testing the nutrient status in soil to establish a labor-saving and cost-effective analytical method in Northern Mozambique. Available P, exchangeable cations, and micronutrients in the Mehlich 3 extract were measured using conventional methods and compared with those quantified using MP – AES to determine its accuracy. Linear regression analysis implied a high correlation between the Available P extracted via Mehlich 3 and quantified using MP – AES and that extracted via Mehlich 3, Bray 1, Olsen, and Mehlich 1 and quantified using UV – Vis. Moreover, a high determination coefficient (R2 = 0.920) was observed between Mehlich 3 quantified using MP – AES and that quantified using UV – Vis spectroscopy with a low root mean square error (RMSE = 9.245), MP – AES may have accuracy comparable to conventional methods. Linear regression of the exchangeable cations extracted using the Mehlich 3 method and quantified using MP – AES and those extracted using the 1 M NH4OAc method and quantified using ICP – AES revealed that the coefficients of determination of Ca, Mg, and K were 0.952, 0.878, and 0.826, respectively. The coefficient of determination for Na was small at 0.101. For the micronutrients, Mehlich 3 extraction with MP – AES quantification method showed a correlation with the conventional DTPA method; specifically, a strong correlation was observed for Cu and Zn. Although the correlation for Fe and Mn was also high, it was less accurate than that for the other elements. The method used in this study is considered effective for estimating field variability. To convert to conventional methods, variation in available elemental content between sites with different local soil properties should be considered.

Effects of Seasonal Variation on some Soil Chemical Properties under Different Land Use in Santa Barbara, Bayelsa State-Nigeria

A study was carried out to examine the effect of seasonal variation on some soil chemical properties under different land-use in Nembe, Bayelsa State-Nigeria. The objective was to evaluate changes in soil nutrient contents in both wet and dry seasons. A total of eighteen soil samples were collected at 0-30 cm depths in August, 2017 (Wet Season) and March, 2018 (dry season) in natural forest, oil palm plantation and arable land-use and analyzed for pH, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), exchangeable cations (Ca, Na, K and Mg), and cation exchange capacity (CEC) using standard analytical methods. Results showed that soil pH was highest (4.2) under oil palm plantation in the wet season, while high content of N 0.52 mg/kg was recorded during the wet season in all the thee-land use. Organic carbon was highest 1.69 mg/kg in natural forest, followed by 1.39 and 1.04 mg/kg for oil palm plantation and arable land use. Maximum value of P 0.22 mg/kg was observed under natural forest during the dry season, and the minimum was recorded under arable land use during the wet season. The concentration of exchangeable Ca was highest 0.3 mg/kg in the oil palm plantation, while Na was highest 2.19 mg/kg for natural forest, 1.26 and 1.06 mg/kg for oil palm plantation and arable land use. The CEC values of the soils in the natural forest were moderately high, followed by oil palm plantation and arable land use in the wet season; whereas low CEC values were observed across the three-land use in the dry season. The study concluded that soil nutrients were more available during the wet season than in the dry season in the various land use, probably due to adequate soil moisture availability in the wet season that facilitates soil nutrient release, this implies that chemical properties of soils were influenced by seasonal changes which could in turn affect agricultural production. It is recommended that crop production is encouraged in the wet season than in the dry season so as to utilize more availability of soil nutrients.

Analysis of Farmland Soil Samples from Tirora Tehsil of Gondia District in Maharashtra, Central India for its Chemical parameters

Soil analysis is a vital step of nutrient management planning of farmlands that includes fertilizer application, rotational plans, making best use of manures etc. The present research paper investigates the physico-chemical parameters of various soil samples from different villages of Tirora tehsil of Gondia district in Maharashtra state (Central India). An in-depth exploration of the farm soils and crops grown in the area was conducted with the aim to study the morphological and chemical characteristics of the soils. For this purpose, twenty soil samples were collected in January 2020 from the study area and parameters such as pH, exchangeable cations, electrical conductivity, available nitrogen and potassium, organic carbon, CaCO3 %, base saturation %, cation exchange capacity etc.

Comparative study of bentonite and Ikwo clay for oil-based drilling mud formulation

As the demand for energy rises, drilling activities and the use of drilling mud by oil and gas industries keep increasing, leading to large consumption and high importation cost of drilling mud materials. The study is conducted to replace high cost of drilling mud materials (bentonite) which is a burden on the companies and our economy at large, with respect to foreign exchange challenge. Locally sourced drilling mud material, clay precisely, from Ebonyi State, particularly Ikwo clay, is yet to be explored as alternative to commercial bentonite. The specific objective of this study is to analyse and compare Ikwo clay in replacement to commercial bentonite as viscosifiers for formulating oil-based drilling mud. The driving motivation is to utilize local content (Ikwo clay) which is in abundance and has remained unprocessed substitute for bentonite. The clay undergoes activation using sulfuric acid (H2SO4) following conventional procedures. XRF spectrophotometers determine chemical compositions and functional groups of bentonite and clay samples. Oil-based muds are separately formulated using bentonite and Ikwo clay additives. The mud weight, pH, apparent viscosity, plastic viscosity, yield point, and gel strength of the respective muds are evaluated. The interactive effects of the process variable on viscosities of each mud sample are determined, and the viscosity of the respective muds was optimized using the Central Composite Design (CCD) tool of Design Expert software (version 12) based on RSM. Activation of the local clay improved its properties, as results of the chemical composition revealed that Ikwo clay contains exchangeable cation like potassium ion (K+)) and an essential metal (iron (iii) ion (Fe3+)), with the presence of alumina signifying its suitability in terms of plasticity and swelling ability. The Ikwo clay mud had a higher sample mud weight than the bentonite mud, which indicates that Ikwo clay can manage formation pressure and improve wellbore stability. The optimum viscosities of the oil-based muds with bentonite and Ikwo clay additives are obtained at 15.49 cP and 18.82 cP, respectively. The optimum values are realized at a bentonite/Ikwo clay dosage of 8 wt%, a temperature of 313 K and a mixing time of 35 min. The novelty of Ikwo clay compared to imported bentonite is its ability to offer structural stability to drilling mud (Rana et al., 2020). This feature is used to control wellbore instability during drilling operations. Ikwo clay is a good fit for bentonite replacement as a viscosifier in formulating drilling mud.

Phosphorus-Enriched Organomineral Fertilizers Affect the Cation Exchange Algorithm of the Soil: A Comparative Evaluation

The aim of this study is to determine the effects of phosphorus-enriched cattle manure applications on the exchangeable cations content, cation exchange capacity (CEC), and base saturation rate (BSR) of the lime soil. The research was carried out with four different levels (except control) of dairy cattle manure (M1: 10; M2: 20; M3: 30; M4: 40 t ha-1) and with four different levels (except control) of phosphorus dose (P1: 10; P2: 20; P3: 30; P4: 40 kg P ha-1) in the ecological conditions of Southwest Türkiye during the wheat vegetation period of 2019-2021. The study was carried out in medium calcareous soil (14.8%) with three replications randomized blocks experimental by composing organomineral fertilizer combinations. According to the results of the study, the highest change in exchangeable Ca and K content in soils was obtained from organomineral fertilizer applications by 11.2% and 29.7% respectively, and the highest change in exchangeable Mg and Na content was obtained from dairy cattle manure applications by 25.1% and 18.2%, respectively for M4P2 (40 t ha-1 dairy cattle manure + 20 kg P ha-1). Among the fertilization systems, the highest increase in total exchangeable cations was 13.1% and the increase in CEC was 21.3% in organomineral fertilizer applications. The fastest decrease in the BSR was also obtained from the organomineral fertilization system. As a result, it has been determined that M4P2 application is the most economical and the most effective combination in the cation exchange capacity among organomineral fertilizer combinations.

ECOLOGICAL MONITORING OF THE RECLAMATION PROCESSES OF THE QUARRY COMPLEXES OF CRIMEA

The aim of the work was to study the temporal stages of primary syngenesis in a comparative assessment of the intensity of vegetation demutational processes and soil cover formation on the waste quarry-dump complexes in the steppe and foothill Crimea.&#x0D; Methods and materials. The studies were conducted in two quarries. The first one is located in the steppe part of the peninsula. It was producing limestone, the quarry is located near the city of Evpatoria. The second quarry is located in the foothill zone near Bakhchisaray. The study of the vegetation was conducted by geobotanical methods. The floristic composition, structure of composition and productivity of the corresponding communities were identified. When assessing the physical indicators of the underlying rocks and emerging soils were taken into account: the aggregate and microaggregate composition of soils, porosity and well of their structure by volume and specific weight of the solid phase. At chemical researches of soils the following parameters were defined: the maintenance of humus, composition of exchangeable cations, active acidity of aqueous extract, general alkalinity, ions Ca2+ and Mg2+.&#x0D; Results. Regional features of vegetation composition and soil-forming processes have been established. The process of regenerating biogeocenoses in the plain part of the peninsula was found to proceed faster than in the foothills. The processes of soil and vegetation syngenesis at the dumps during the biological recultivation are strongly stretched on the time scale and are still very far from the natural ecosystems even after 35-40 years.&#x0D; Conclusions. Focusing on optimizing these areas through biological reclamation alone is problematic. It is necessary to plan mining-technical reclamation to return these territories to economic use.

Soil amendment and rhizobacterial inoculation improved Cu phytostabilization, plant growth and microbial activity in a bench-scale experiment.

Mine driven trace elements' pollution entails environmental risks and causes soil infertility. In the last decades, in situ techniques such as phytostabilization have become increasingly important as ways to tackle these negative impacts. The aim of this study was to test the individual and combined effects of different aided phytostabilization techniques using substrate from barren tailings of a Cu mine, characterized by extreme infertility (high acidity and deficiency of organic matter and nutrients). The experiment analyzed the growth of Populus nigra L. planted alone (P) or in co-cropping with Trifolium repens L. (PT), in pots containing mine soil amended with compost (1, 10, compost, soil, w/w) non inoculated (NI) or inoculated with plant growth promoting rhizobacteria (PGP), mycorrhizae (MYC) or a combination of bacterial and fungal inocula (PGPMYC). Non-amended, non-planted and non-inoculated reference ports were also prepared. Plants were harvested after 110 days of plant development and several biometric and phytopathological parameters (stem height, aerial biomass, root biomass, wilting, chlorosis, pest and death) and macro and micronutrient composition were determined. The growth substrate was analyzed for several physicochemical (pH, CECe, and exchangeable cations, total C and N, P Olsen and availability of trace elements) and microbiological (community level physiological profiles: activity, richness and diversity) parameters. The use of the amendment, P. nigra plantation, and inoculation with rhizobacteria were the best techniques to reduce toxicity and improve soil fertility, as well as to increase the plant survival and growth. Soil bacterial functional diversity was markedly influenced by the presence of plants and the inoculation with bacteria, which suggests that the presence of plant regulated the configuration of a microbial community in which the inoculated bacteria thrive comparatively better. The results of this study support the use of organic amendments, tolerant plants, and plant growth promoting rhizobacteria to reduce environmental risk and improve fertility of soils impacted by mining.

Exploración de los cationes intercambiables del suelo y auditoría del potencial de Phoenix dactylifera y Mangifera indica en el secuestro de CO2 en la biomasa del suelo en una parcela arbóroles de origen natural

Antecedentes: El experimento investigó los cationes intercambiables (EC) del suelo y auditó el potencial de Phoenix dactylifera y Mangifera indica en el secuestro de CO2 en la biomasa del suelo y en otros actos como factor de remediación para la sostenibilidad de la agricultura. Metodología: El estudio utilizó un diseño de investigación de muestreo estratificado en el que se utilizó el analizador de gas infrarrojo (IRGA) para muestrear ubicaciones estandarizadas dentro de la masa terrestre experimental para detectar el CO2 capturado en la biomasa del suelo en un período de cinco (5) meses. El índice de similitud de especies de Sorensen se aplicó en el estudio para obtener una radiografía y validar el rendimiento de las dos especies de árboles para el rendimiento de similitud potencial de secuestro de CO2. Resultados: Los resultados indicaron que existe un potencial de las dos especies de árboles para secuestrar CO2 atmosférico en un valor de 1.25± 0.13 y 0.47±0.19 para Phoenix dactylifera y Mangifera indica respectivamente en un intervalo de cinco (5) meses. Conclusiones: La distribución de cationes intercambiables de Ca2+, Mg2+, K+, Na+ indicó que existe incremento de los cationes intercambiables en la solución del suelo al final de los cinco (5) meses con un Coeficiente de Variación (CV=101%). Se observó un aumento en la capacidad de intercambio de cationes (CEC) del suelo de 7,3 cmolkg-1 al comienzo del experimento a 7,47 cmolkg-1 al final del experimento, lo que indicó un aumento en el estado de fertilidad de los suelos.

Thermodynamic behavior of water vapor adsorption in shale and its dependence on organic matter and clay minerals

Isothermal adsorption experiments of water vapor in shale samples with differing TOC (total organic carbon content) and differing clay content were conducted at three set temperatures to reveal the adsorption mechanism, and to determine the thermodynamic dependence of primary and secondary adsorption processes on the content of organic matter and clay minerals. The adsorption of water vapor in shale is spontaneous with the Gibbs free energy change is minus ranging from −0.28 - −5.15 KJ/mol, the adsorption changes from entropy driven to enthalpy driven as the adsorption amount increases (enthalpy change turns from plus to minus ranging from −1.25–––6.72 KJ/mol, and the entropy change is opposite ranging from −0.0031–––0.035 KJ/mol), and the primary adsorption amount increases with higher experimental temperature but secondary adsorption amount decreases. Fitting results and their relying theories indicate that micropore filling and monolayer adsorption occur in primary adsorption mainly though strong hydrogen bonding and electrostatic forces between water vapor and the pore surface, and multilayer adsorption and capillary condensation dominate secondary adsorption mainly through weak hydrogen bonding among water vapor. There are positive correlations of adsorption amount versus both clay content and TOC. Clay minerals are strongly hydrophilic because of their exchangeable cations and polar groups, providing primary and secondary adsorption sites, and enhancing the spontaneity of adsorption. OFGs (oxygen functional groups) in organic matter are hydrophilic, other pore surfaces are hydrophobic or weak hydrophilic, which also develop many adsorption sites. Results from this work provide new insights about the influence of organic matter and clay minerals on the adsorption thermodynamic behavior of water vapor in shale.

Quantitative Study on Salinity Estimation of Salt-Affected Soils by Combining Different Types of Crack Characteristics Using Ground-Based Remote Sensing Observation

Soil salinity is one of the parameters used for determining the extent of soil salinization. During water evaporation, the surface of salt-affected soils in the Songnen Plain, China, exhibits obvious shrinkage and cracking phenomena due to the high salt content. The aim of this current study is to quantify the influence of the salt content on the surface shrinkage–cracking process and to achieve quantitative extraction of soil salinity parameters based on different crack parameter types. In order to achieve the above objectives, a controlled shrinkage–cracking experiment was conducted. Subsequently, three kinds of crack characteristics such as crack length, box-counting dimension, and 12 gray-level co-occurrence matrix (GLCM) texture features were quantitatively extracted from the standard binary crack patterns. In order to predict the soil physical–chemical properties of salt-affected soils in the Songnen Plain, three models such as multiple linear regression (MLR), multiple stepwise regression (MSR), and artificial neural network (ANN) were developed and compared based on the crack length, box-counting dimension, and the first two principal components of GLCM texture features. The results show that the extent of desiccation cracks was determined by soil salinity since the water film caused by exchangeable cations and the thickness of DDL determined by soil salinity can promote desiccation cracking. Although the three methods have high prediction accuracy for Na+, electrical conductivity (EC), and total soil salinity, the ANN-based method showed the best prediction with R2 values for Na+, EC, and soil salinity as high as 0.91, 0.91, and 0.89, and ratio of performance to deviation (RPD) values for Na+, EC, and soil salinity corresponding to 2.96, 3.47, and 2.95.

Evaluation of a miniaturized portable NIR spectrometer for the prediction of soil properties in Mediterranean central Chile

Near-infrared (NIR) spectrometry to estimate soil properties has been evolving toward more portable and accessible equipment in recent years for the prediction of indicators of soil fertility in agroecosystems. There were two objectives of this study. First, to calibrate and validate a miniaturized portable NIR spectrometer NeoSpectra-Module 2.5 with a limited spectral range (1350–2500 nm) for the prediction of total nitrogen (TN), soil organic carbon (SOC), soil pH, clay content and exchangeable cations (Ca2+, Mg2+, K+ and Na+) in dry conditions. And second, to evaluate the use of an external orthogonalization parameter (EPO) to reduce the effect of soil moisture in samples with field moisture conditions collected from Mediterranean central Chile (33° SL to 36° SL). Soil classified as Mollisols, Alfisols and Inceptisols was sampled (n = 170) from 0 to 30 cm depth and scanned with the NeoSpectra spectrometer. The spectrometer showed good performance (R2 > 0.5 and/or RPIQ>1.4) for predictions of SOC and exchangeable cations. When the spectra data without transformation was used (raw spectra) versus transformed spectra, better performance in the predictions was obtained for TN, SOC, pH, clay content and Ca2+. The cubist model (CM) showed better performance than partial least squares (PLSR) for most assessed soil properties. The EPO procedure allowed us to decrease the error due to soil moisture in the prediction of some soil properties. Although the use of a miniaturized portable NIR spectrometer showed promising results for prediction of soil properties, future testing should increase the number of soil samples, vary the spectral data processing, and/or test new miniaturized portable NIR spectrometers with a wider spectral range.

Bioaccessibility by perspiration uptake of minerals from two different sulfurous peloids

The risks associated with the use of peloids in thermal centers, spas, or at home, must be tested to develop appropriate safety guidelines for peloids formulations and the release of substances of high concern. Additionally, the beneficial effects of some elements on human health should be assessed to aid in interpreting the therapeutic action and effectiveness of pelotherapy on dermatological or osteomuscular disorders. Therefore, a methodology was developed to better understand the biogeochemical behavior of the elements in formulated peloids. Two peloids were formulated with the same clay and two different sulfurous mineral-medicinal waters for 90 days, with light stirring every 15 days. Bentonite clay, with a high content of smectite and Ca and Mg as the main exchangeable cations, and high heat capacity, was used. The selected mineral-medicinal waters were collected from two Portuguese thermal centers with recognized therapeutic efficacy for rheumatic, respiratory and dermatological pathologies. The peloids were used without drying and withdrawn directly from the maturation tank, and a mixture of bentonite and demineralized water was prepared as a reference sample. A stabilized, ready-to-use, artificial perspiration test was used to simulate the peloids’ interaction with skin. Thirty-one elements extracted from the two prepared peloids were analyzed using ICP-MS. The data were analyzed and related to the mineralogical composition of the original clay and supernatant composition of the maturation tanks. The content of some potentially toxic elements and metals’ bioaccessibility by perspiration showed very low solubility and undetectable amounts extracted from the studied samples. This analytical method provided reliable information on dermal exposure and the identification of some elements that may enter the systemic circulation, requiring implementation of surveillance and control measures.Graphical abstract

Short-Term Effects of Bokashi Fertilizer with Reduced NPK Fertilization on Soil Fertility, Growth, and Yield of Rubber Trees

Rubber is currently the second major industrial crop in Malaysia after oil palm. The use of bokashi fertilizer (BF) on industrial crops is still not popular, and farmers rely mostly on chemical fertilizers (CFs) that are costly and hazardous to the environment. This research was conducted at Hevea plantation, Universiti Putra Malaysia, between August 2020–October 2021. The study was to assess the short-term effects of BF with reduced NPK fertilization on soil fertility, growth, and yield of rubber. Seven treatments (T) were involved. T1, T2, and T3 denote 4, 8, and 12 kg BF per pit. T4 was 1 kg NPK as control, whereas T5, T6, and T7 denote 4, 8, and 12 kg BF + 500 g NPK per pit, respectively. The variables observed included total nitrogen (TN%), total phosphorus (TP%), organic carbon (OC%), organic matter (OM%), exchangeable cations, microbial counts, tree girth, and dry rubber yield. The major findings indicated that applying 12 kg BF has raised the soil’s TN%, OC%, and OM% by 165, 171.4, and 172.0%, respectively, compared to NPK control. Also, adding 4 kg BF + 500 g NPK has increased the soil’s cation exchange capacity and TP% values by 107.8 and 42.9%, respectively, compared to the control. Adding sole bokashi increased the bacterial population by 22.2–133.3%. Rubber yield was better on trees treated with 12 kg BF, though this did not differ significantly from other treatments. Therefore, applying 12 kg BF or 4 kg BF + 500 g NPK can improve soil fertility and save costs from using inorganic fertilizer by at least 50%.

Effect of Mulching on Soil Quality in an Agroforestry System Irrigated with Reused Water

In this study, a special rice-energy willow/poplar agroforestry system was used to analyze the effects of reused water irrigation and mulching on soil salinity, earthworm biomass and abundance, soil organic matter (SOM) content and weed coverage in treerow-dependent habitats. After three-year-irrigation, we investigated the woody line (WL), the buffer zone (BZ) and the crop line habitats (CL). Between 2019 and 2021, we collected data on the distribution of soil-specific electrical conductivity (EC), ammonium-lactate soluble sodium (AL-Na) and exchangeable cations (Na+, K+, Ca2+, Mg2+) and soil NO2− + NO3−-N contents from CL habitats irrigated with effluent water from an intensive catfish farm. Based on our results, significantly greater earthworm abundance (274 pc m−2) and earthworm biomass (54.0 g m−2) values were measured in WL than in BZ or CL habitats. There was no significant difference in weed coverage between the CL (0.61%) and BZ (1.91%), but weeds were significantly denser on the WL (12.3%). In the third year, the EC, AL-Na and ESP values were lower, but the SOM was higher in mulched soil (183.1 mS cm−1, 253.1 mg kg−1, 4.4 ESP% and 4.597%, respectively) than in un-mulched soil.