Soil Syst., Volume 8, Issue 2 (June 2024) – 32 articles

The search for new biodegradable fertilizers to increase the productivity of agricultural plants is an urgent task. In this study, a complex microfertilizer was developed based on a chelating agent—glutamic-N,N-diacetic acid (GLDA). The evaluation encompassed assessments of biodegradability and effectiveness in fostering lettuce plant growth in hydroponic and conventional soil settings. The impact on endospheric bacteria, a sensitive indicator, was also examined. Results indicated a 59.8% degradation rate of the GLDA complex on the 28th day. The most notable positive effects were observed in above-ground plant biomass, with a 4.6-fold increase for hydroponics and 1.5 to 1.8-fold increases for root and foliar treatments in soil. In hydroponics, GLDA-treated plants showed 24 and 45 operational taxonomic units (OTUs) for leaves and 272 and 258 for roots (GLDA-treated and control plants). In soil, the OTU counts were 270 and 101, 221 and 111, and 198 and 116 in the leaves and roots of GLDA-treated and control plants (under root and foliar treatments), respectively. Non-metric multidimensional scaling (NMDS) and Indicator Species Analysis (ISA) demonstrated significant distinctions in endospheric communities between substrates (hydroponics and soil) in the presence of GLDA. Importantly, GLDA use simplified the composition of endospheric bacterial communities. Full article

Addressing within-field spatial variability for nitrogen (N) management to avoid over and under-use of nitrogen is crucial for optimizing crop productivity and ensuring environmental sustainability. In this study, we investigated the economic, environmental, and agronomic benefits of variable rate nitrogen application in potato (Solanum tuberosum L.). An online visible and near-infrared (vis-NIR) spectroscopy sensor was utilized to predict soil moisture content (MC), pH, total organic carbon (TOC), extractable phosphorus (P), potassium (K), magnesium (Mg), and cation exchange capacity (CEC) using a partial least squares regression (PLSR) models. The crop’s normalized difference vegetation index (NDVI) from Sentinel-2 satellite images was incorporated into online measured soil data to derive fertility management zones (MZs) maps after homogenous raster and clustering analyses. The MZs maps were categorized into high fertile (VR-H), medium–high fertile (VR-MH), medium–low fertile (VR-ML), and low fertile (VR-L) zones. A parallel strip experiment compared variable rate nitrogen (VR-N) with uniform rate (UR) treatments, adjusting nitrogen levels based on fertility zones as 50% less for VR-H, 25% less for VR-MH, 25% more for VR-ML, and 50% more for VR-L zones compared to the UR treatment. The results showed that the VR-H zone received a 50% reduction in N fertilizer input and demonstrated a significantly higher crop yield compared to the UR treatment. This implies a potential reduction in negative environmental impact by lowering fertilizer costs while maintaining robust crop yields. In total, the VR-N treatment received an additional 1.2 Kg/ha of nitrogen input, resulting in a crop yield increase of 1.89 tons/ha. The relative gross margin for the VR-N treatment compared to the UR treatment is 374.83 EUR/ha, indicating substantial profitability for the farmer. To further optimize environmental benefits and profitability, additional research is needed to explore site-specific applications of all farm resources through precision agricultural technologies. Full article

The Amazon Forest has a soil organic carbon stock (SOCS) potential of 126 to 141 Tg year⁻¹ and it depends on soil organic matter (SOM) accumulation factors and stabilization mechanisms. This study aimed to evaluate SOCS, soil nitrogen stocks (SNS), SOM fractions under the Amazon Forest along a topographic and vegetation gradient (Terra Firme, River Plain, and Terraces), and to evaluate the main mechanisms responsible for SOM stabilization. The study was developed using 35 study points (35 profiles) in Coari County, Amazon State, Brazil. In each profile, soil samples were collected from soil horizon for soil analysis. Of the 35 soil profiles, 10 were selected to evaluate the contribution of free light fractions (FLF) and intra-aggregate light fractions (ILF), C and N contents, and SOCS and SNS up to 1 m soil depth. SOCS and SNS are influenced by topographic and vegetation gradient, being statistically equal in the Terra Firme and River Plains areas (median of 92.5 and 92.2 Mg C ha⁻¹, respectively), but Terraces presented a greater median (157.9 Mg C ha⁻¹). There are relationships between SOCS and SNS and C, N, Al, clay content, t value, FLF, and ILF. SOCS, SNS, and SOM stabilization in Amazon soils are influenced by soil properties and landscape position. SOCS in the Terrace is mainly in FLF form. If vegetation cover loss continues, an amount of up to 98.05 Mg C ha⁻¹ of FLF can be lost, causing soil degradation and global warming. Full article

This study represents the first investigation of soil ciliate diversity and community structure in the Marche region, Italy, encompassing both natural sites and agro-ecosystems. The main aims were (i) to assess the ability of ciliates to discriminate between different types of land uses, i.e., arable lands and possible farming management practices [organic (ORG) vs. conventional (CON)], and forest (FOR) sites; and (ii) to investigate the relationships among ciliate communities and abiotic parameters at the studied sites. Soil samples were collected twice from 10 sites (5 forest (FOR) (natural soils) and 5 arable lands under different agricultural management systems (3 ORG (minimum tillage) and 2 CON (sod seeding)). Ciliate communities were studied using qualitative (non-flooded Petri dish) and quantitative methods (ciliate counts from permanent slides). Soil chemical–physical (texture, CEC, N, OM, C/N) parameters were also measured. Qualitative ciliate analysis allowed us to identify a total of 59 species representing 33 genera, 20 families, 13 orders, and 7 classes. ORG sites were the richest in species followed by CON and FOR. Multivariate analysis showed statistically significant differences between natural sites (FOR) and agricultural sites, and between ORG and CON management farming systems. CCA analysis revealed a positive correlation between the ciliate species and silt, clay, and pH in ORG sites, and sand, organic carbon, organic matter, total nitrogen, C/N ratio, and CEC (cation exchange capacity) in FOR sites, suggesting the significance of these parameters in shaping the ciliate communities. Altogether, these results showed the bioindicative potential of ciliate communities in discriminating between natural sites (FOR) and arable lands, and their capacity to discriminate, at least preliminarily, between different soil management systems (ORG vs. CON). Furthermore, this study highlights the high diversity of soil ciliates and their response to habitat variability. Full article

Potentiometric titration in a fast and simultaneously high-resolution modality was proposed for the identification and quantification of protolytic groups of variable strength at the surface of primary soil particles. The method is implemented by titrimetric data processing as multicomponent spectra (pK_a spectrotitrimetry). Due to the high resolution, the error of acidity-constant assessment (3–5%) is lower, compared to existing approaches; due to the fast titration, the effect of soil hydrolysis is minimized. The soil profiles for acidic Retisols (podzolic soils)—under a spruce crown and in the intercrown space—were studied. These soils, which have similar bulk properties and genesis but developed under different plant covers, were distinguished by pK_a spectral features at 4–5; 5.5–6.5; 6.5–8.5; 7.5–8.5; and 9–10, as well as total group concentrations. Differences in acidic and basic-group distribution (carboxyl groups, amorphous aluminosilicates, carbonate species, amino groups, soluble (poly)phenolic compounds, phospholipids) and Al and Fe complex compounds within the same soil profiles and between two Retisols were found and quantified. The acidity constants and group concentrations found by pK_a spectrotitrimetry were compared with conventional soil-composition indicators (total organic carbon, oxalate-soluble Fe and Al, and phosphorus), using principal component analysis. The main correlations are between the concentrations of oxalate-soluble Al and groups with pK_a values of 5.0–6.5 and 8.5; oxalate-soluble Fe and pK_a values of 9.0–10.0; and P₂O₅ and pK_a values of 4.0–6.0 and 6.5–8.5. The method provides a set of major acidity values without a priori information on a soil sample and can be used for screening and identifying similar soils. Full article

Worldwide zinc deficiency in the soil under cereal production is a common problem affecting the yield and nutritional value of several crops. Bioaugmentation of soil zinc with zinc-solubilizing bacteria can be a promising option for increasing the zinc nutrition to crops. The objectives of the study were to evaluate Bacillus paramycoides for improving yield, zinc nutrition, and zinc availability in rice grown under sodicity stress caused by alkali water irrigation. Treatments included T₁: control, T₂: substrate, T₃: Bacillus paramycoides, T₄: control (T₁) + zinc sulphate, T₅: substrate (T₂) + zinc sulphate, and T₆: Bacillus paramycoides (T₃) + zinc sulphate. Rice yield, zinc content, and uptake, and apparent zinc recovery were not altered by Bacillus paramycoides. The different fractions of zinc measured after 30 and 60 days after transplanting of the rice remain unaffected by the inoculation of Bacillus paramycoides. Further, an equal number of zinc-solubilizing bacteria present in the rice rhizosphere of control plots after 30 days of transplanting suggests the importance of the native rhizospheric microbiome in zinc nutrition. It is concluded that the application of Bacillus paramycoides in sodicity-stressed rice did not provided additional benefits in terms of zinc nutrition and yield. Further investigation will be required to improve the apparent zinc recovery of crops in those areas, where alkali water is continuously utilized for irrigation. Full article

The efficient separation of solid and liquid phases of soil under reductive conditions is of the utmost importance to study soil chemistry and to predict the mobility and bioavailability of nutrients and toxic contaminants in waterlogged reduced soils (WRSs). However, there is no established method for efficiently separating the solid and liquid phases of WRS within a short time while maintaining its reductive conditions. This study aimed to verify the applicability of a simple centrifugal filtration method (CFM) for the efficient separation of solid and liquid phases of a WRS and examine the CFM-extracted soil solution to confirm that the reductive condition was maintained during the solid–liquid separation process. Incubation experiments were performed under reductive conditions with or without ethanol/molasses used as additional organic material (OM), while the soil solution was collected by both a suction method and CFM at different centrifugation speeds (700, 2760, and 11,000 rpm) and times (1–7 min). The results showed that the soil pH increased with time while the Eh decreased, indicating that its reducing state was enhanced during the incubation experiments. The addition of OM promoted the reductive conditions in the first days of the experiments. Centrifugation speed, rather than time, was found to be the key to extract the maximum amount of soil solution, while a higher centrifugation speed (11,000 rpm), which represents the permanent wilting point, was found to be most effective for extracting the maximum amount of soil solution. The results exhibited no significant difference in solute (As, Fe(II), and Mn) concentrations when varying amounts of CFM-extracted soil solution were measured. The statistical analysis also indicated no significant (p > 0.05) difference between the solute concentrations in the CFM-extracted soil solution and the solute concentrations in the soil solution extracted by the suction method, confirming that the reductive condition was maintained during solid–liquid separation by CFM. This study suggests that CFM operating at a higher centrifugation speed could potentially be employed as a simple and highly effective technique to efficiently separate the solid and liquid phases of WRS (sandy clay loam) within a short time while maintaining its reductive conditions. Full article

In the Pistoia Nursery-Ornamental Rural District (Italy), a leader in Europe in ornamental nurseries covering over 5200 hectares with over 2500 different species of plant, plant-parasitic nematodes represent a serious concern. The potential efficacy of a pot cultivation system using commercial substrates to control plant-parasitic nematodes was assessed. On two different plant species, two different pot cultivation managements, potted plants, and potted plants previously cultivated in natural soil were compared to plants only cultivated in natural soil. The entire soil nematode structure with and without plants was evaluated. The relationship between soil properties and soil nematode community was investigated. All the studied substrates were free from plant-parasitic nematodes. Regarding free-living nematodes, Peat–Pumice showed nematode assemblage established by colonizer and extreme colonizer bacterial feeders, whereas Peat–Perlite included both bacterial and fungal feeders, and, finally, coconut fiber also included omnivores and predators. In farming, the substrates rich in organic matter such as coconut fiber could still play an important role in suppressing plant-parasitic nematodes because of the abundance of free-living nematodes. In fact, they are of crucial importance in both the mineralization of organic matter and the antagonistic control of plant-parasitic nematodes. Potting systems equally reduce virus-vector nematodes and improve the prey/predator ratio favoring natural control. Full article

Garlic (Allium sativum L.) is an important crop cultivated in arid and semi-arid climates. To quantify the tolerance of garlic to drought and salinity stresses in terms of parameter values of the stress response function, we conducted pot experiments in a greenhouse for two years. Nine 1/5000a Wagner pots were used for three treatments, namely drought-treated, salinity-treated, and control pots, for estimating the relative transpiration. Daily transpiration rates were observed by weighing pots, and the soil surface of each pot was covered. The soil water contents were measured hourly using two soil moisture probes for drought-treated pots, and two salinity probes for both soil water content and bulk electrical conductivity were monitored for salinity-treated pots. When the ratio of actual to potential transpiration fell below 50%, the root length distributions were obtained by dismantling the pots. The parameter values for both drought-stress and salinity-stress functions were estimated using inverse-analysis and bulk-analysis methods. The parameter values of drought-stress and salinity-stress functions obtained by the simpler and cheaper bulk method gave similar results to the inverse method when the root length distributions were relatively uniform. Full article

Due to the falling water level in the Aral Sea and Muynak Lake, the content of salts dissolved in the water has gradually increased, and toxic elements have been deposited at the lake’s bottom and subsequently washed into the Aral region by the river. Bacteria, archaea and fungi are crucial for the cycling of several important inorganic nutrients in soils. From 15 genera and 31 species of recovered microscopic filamentous fungi, a big group was melanized, of which most of them were also phytopathogenic. The second group consisted of keratinophilic species. Isolated bacteria mainly included members of the genera Arthrobacter, Bacillus, Massilia, Rhodococcus and Nocardiopsis. High-throughput sequencing analysis permitted a better view of the mycobiome and prokaryotic communities (comprising archaea). The cultivation and sequencing approaches were shown to be complementary. The aim of the work was to identify soil microorganisms, including the order Halobacteriales, and to discover the differences in species diversity depending on soil salinity and the presence of PTEs in soil. Full article

Radiocesium (r-Cs) and radiostrontium (r-Sr) released from nuclear accidents (e.g., Chornobyl, Fukushima) and routine operations (reactors, reprocessing) pose environmental and health concerns. Their primary pathway to humans is through plant uptake and subsequent bioaccumulation within the food chain. While soil amendments with potassium (K) and calcium (Ca) are known to mitigate r-Cs and r-Sr uptake, respectively, the impact on plant growth remains unclear. This study investigates the effects of Cs and Sr on the growth of Holcus lanatus L. seedlings under hydroponic and soil conditions with varying Cs and Sr concentrations. Stable isotopes of Cs and Sr served as non-radioactive analogs. Seedling growth was assessed across a range of Cs and Sr concentrations (≤1 and ≥4 mg L⁻¹). The impact of the addition of K and Ca on Cs/Sr uptake in amended soils was also evaluated. Additionally, this study examined how Cs and Sr amendments affected the influx rates of other nutrients in H. lanatus. Higher Cs and Sr concentrations (≥4 mg L⁻¹) significantly inhibited seedling growth, while lower concentrations had no effect. Notably, H. lanatus exhibited moderate Cs tolerance and strong Sr tolerance. Furthermore, K and Ca supplementation in Cs/Sr-amended soils demonstrably reduced plant uptake of these elements. This study also observed alterations in the uptake rates of other nutrients within H. lanatus due to Cs/Sr addition. This study suggests that H. lanatus exhibits moderate tolerance to Cs and Sr contamination, potentially making it suitable for revegetation efforts in contaminated grasslands. Additionally, K and Ca amendments show promise as a strategy to mitigate plant uptake of these radioisotopes further. These findings contribute to the development of safer revitalization strategies for areas impacted by nuclear accidents. Full article

X-ray fluorescence (XRF) core scanners are commonly used for fine-scale geochemical analysis in sediment studies, but data are semi-quantitative and require calibration to convert geochemical element counts to concentrations. Application of XRF core scanning in soil science remains largely untapped. This study employed an ITRAX core scanner to scan grassland soil cores and developed a novel calibration method based on a chemometric approach to characterise soil geochemistry. As soil samples are collected based on depth sampling, this study investigated whether higher resolution element concentrations could be inferred from lower resolution reference samples and if regression models from multiple cores could apply to a new core at the same resolution. Reference concentrations were obtained for all cores at 10 cm intervals, with validation conducted at 1 cm for a single core. Two calibration curve types were proposed: one based on the single core’s 10 cm data to validate references at 1 cm intervals; and another using all cores, with each core serving as a test item after exclusion from the training set. Various preprocessing measures and feature selection techniques were tested. Results showed successful calibration for elements Ca, P, Zn, Sr, and S, with high $R^2$ values of 0.94, 0.93, 0.93, 0.92 and 0.91, respectively. The study presents a novel method for calibrating XRF core scanning element counts, demonstrating its potential for high-resolution soil analysis. Full article

Texture, soil organic matter (SOM), and soil depth (SoD) are crucial properties in forest management because they can supply spatial information on forest site productivity and guide fertilizer applications. However, soil properties possess an inherent uncertainty that must be mapped to enhance decision making in management applications. Most digital soil mapping predictions primarily concentrate on the mean of the distribution, often neglecting the estimation of local uncertainty in soil properties. Additionally, there is a noticeable scarcity of practical soil examples to demonstrate the prediction uncertainty for the benefit of forest managers. In this study, following a digital soil mapping (DSM) approach, a Quantile Regression Forest (QRF) model was developed to generate high-resolution maps and their uncertainty regarding the texture, SoD, and SOM, which were expressed as standard deviation (Sd) values. The results showed that the SOM (R² = 0.61, RMSE = 2.03% and with an average Sd = 50%), SoD (R² = 0.74 and RMSE = 19.4 cm), clay (R² = 0.63, RMSE = 10.5% and average Sd = 29%), silt (R² = 0.59, RMSE = 6.26% and average Sd = 33%), and sand content (R² = 0.55, RMSE = 9.49% and average Sd = 35%) were accurately estimated for forest plantations in central south Chile. A practical demonstration of precision fertilizer application, utilizing the predictive distribution of SOM, effectively showcased how uncertainty in soil attributes can be leveraged to benefit forest managers. This approach holds potential for optimizing resource allocation and maximizing economic benefits. Full article

Biochar (Bc) and liquid vermicompost extracts (LVEs) are increasingly being used as biofertilizers in agriculture to promote soil-microbe-crop interactions. However, although both these products can potentially act synergistically due to their complementary characteristics, their co-application in different soils has not yet been investigated. Therefore, firstly, an LVE-activated biochar (B_LVE) was experimentally formulated and the persistence of LVE bacteria over a 60-day storage period was determined. The total number of LVE bacteria increased by 10-fold after 7 days and was stable throughout the entire biochar storage period. In addition, changes in the composition of the bacterial community were observed after 30 days of storage, indicating that taxa less represented in pure LVE may be advantaged upon biochar colonization. Secondly, a microcosm experiment was performed to evaluate whether the biological fertility and enzyme activities of two soils, differing in organic matter content, could be enhanced by the addition of LVE-activated biochar. In this experiment, three different doses of Bc, LVE, and B_LVE against the carbon-related biological fertility index (i.e., biological fertility index, BFI) and three enzyme activities over a 21-day incubation period were tested. The B_LVE treatment yielded the best results (i.e., BFI +32%, enzyme activities +38%). This indicates that Bc and LVEs can act synergistically to promote soil fertility, quality, and microbial activity. By integrating LVE-activated biochar into their soil management practices, farmers could achieve higher crop yields and healthier products. Full article

In this work, environmentally sound technologies for converting organic wastes into fertilizers to improve soil sustainability and crop yield have been identified and assessed. Wet wastes were combined with 50% wood sawdust and 50% wet wastes (Compost 1) or (10% Straw + 90% wet wastes) (Compost 2) to produce soil improvers with a balanced level of nutrients, and their effectiveness on soil ecosystem functioning have been tested and compared to horse manure (HM) and nitrogen–phosphorous–potassium (NPK) fertilizers. Unfertilized soil was used as a control. Soil chemical and biological properties have been detected after the harvesting of broccoli and red cabbage (90 days from the initial treatments). Three independent experiments have been conducted in an open field in a randomized complete block design with three replications (n = 9). The results showed that Compost 1 had the highest C/N ratio and cation exchange capacity (CEC), indicating a better humification of the wet material. Compost 1, even if it contained a minor amount of organic carbon, as well as less activity of fluorescein diacetate (FDA) and dehydrogenase (DHA) than Compost 2, was the most effective in improving soil quality, significantly increasing the labile fraction of organic matter, the oxidative enzyme (DHA), microbial biomass, and crop yield. Both composts increased crop productivity. Full article

Comprehension of the long-term effects of irrigation on basic soil characteristics and quality is essential for sustainable land management and agricultural production, particularly in arid regions where water availability is limited. This study aimed to investigate long-term irrigation effects on soil quality, soil organic carbon (SOC), and nitrogen (N) stocks in the arid lands of Egypt. Seventy soil samples were collected and analyzed to determine various soil properties. A soil quality index (SQI), SOC, and N stocks were computed. ANOVA and PCA analyses were used to identify significant differences between alluvial soils in the southwest part of the investigated area and coastal marine soils in the northeast of the study area. The results demonstrated that most of the studied soil parameters had significantly greater values in alluvial compared to coastal marine soils. Long-term irrigation led to an 8.00% increase in SOC and 7.22% increase in N stocks compared to coastal marine soils production. Furthermore, a 39.53% increase was found in the SQI upon long-term irrigation practice. These results suggest that shifting from rain-fed in coastal marine areas to irrigated production systems in alluvial fields can improve soil quality, SOC, and N stocks. Therefore, further studies are required to investigate the impact of additional factors, such as irrigation method and salinity status of sub-surface soil layers, to enhance agricultural productivity and sustainable land use. Full article

Hulls and shells are an abundant by-product from almond production with potential as an organic matter amendment (OMA). A combination of incubation study and field research was conducted in 2019–2021 to evaluate the impacts of three practices in combination on orchard soils’ C and N cycling, including a 210-day period of laboratory incubation with hulls and shells, and field sampling of orchard soils with and without historic applications of green waste compost as an OMA; with hulls and shells and with and without off-ground harvest where orchard soils remain undisturbed year round. Hulls and shells increased microbial biomass carbon in the field study by 248 μg g⁻¹ dry soil after one year (p < 0.001) and during incubation, and increased cumulative respiration in soils with and without historic OMA (p < 0.001). Historic OMA resulted in double the total soil organic carbon (SOC) and total nitrogen (TN) compared to soil without resulting in significantly higher respiration and N mineralization when amended with hulls and shells. The decomposition of hull and shell biomass following surface application progressed at similar rates in the laboratory and field (1.7 g kg⁻¹ d⁻¹ during incubation (R² = 0.84) and 1.3 g kg⁻¹ d⁻¹ in the field trial (R² = 0.91). Our results highlight the suitability of hulls and shells as a by-product source of OMA for improving soil health in orchards with historic OMA and transitioning to organic matter management. Full article

The Somma–Vesuvius volcanic complex emitted huge quantities of volcanic materials over a period from before 18,300 years BP to 1944. The activity during the last period, from post-AD 1631 to 1944, primarily produced lava and pyroclastics via effusive and strombolian eruptions. We investigated the pedogenesis on rocks formed from post-AD 1631 to 1944, occurring on the slopes of Mt. Vesuvius up to Gran Cono Vesuviano and in the northern valley separating Vesuvius from the older Mt. Somma edifice. Pertinent morphological, physical, chemical, and mineralogical (XRD and FT-IR) soil properties were studied. The results indicated the existence of thin and deep stratified soils on lava, as well as the presence of loose detritic covers formed via pyroclastic emplacement and redistribution. The soils showed minimal profile differentiation, frequently with layering recording the episodic addition of sediments. We found that the dominant coarse size of primary mineral particles was preserved, and there was a low level of clay production. The main mineralogical assemblage present in sands also persisted in clays, indicating the physical breaking of the parent material. Chemical weathering produced mineral modifications towards the active forms of Al and Fe and was also attested in selected soils by glass alteration, allophane production, and the presence of analcime in clay as a secondary product from leucite. The differences in glass alteration and analcime production found in the selected soils on lava were related to soil particle size and soil thickness. Concerning the youngest soil present on Gran Cono Vesuviano, other factors, such as the substratum’s age and site elevation, appeared to be implicated. Full article

More exact information on soil nutrient management is crucial due to environmental protection, nature conservation, decreasing sources for mining, general precaution, etc. Soil magnesium (Mg) analytical methods of potassium chloride (KCl), Mehlich 3 (M3), water (WA) and cobalt hexamine (CoHex) extractions are compared with an elemental analysis and X-ray fluorescence (XRF) analysis. The ratio of the available to the total Mg content was calculated and compared on the whole dataset. The results showed that the linear regressions between all the pairs of Mg content measurement methods were significant. The linear relationship between the KCl and CoHex methods has the highest determination coefficient (R² = 0.96), followed by WA–M3 (R² = 0.68), M3–CoHex (R² = 0.66) and M3–KCl (R² = 0.60). The M3 solution demonstrated a greater capacity for extracting Mg from the soil. The second part is the analysis of the influence of CaCO₃, pH, soil texture and clay content on the measurable magnesium content of soils. It was established that the extraction methods, the soil and the classification method of the soil properties affect the evaluation. These results may help through the nutrient replenishment and the melioration of soils. These results can help the examination of mineral nutrients, especially the Mg uptake. Full article

Estimating soil erodible fraction based on basic soil properties in arid lands is a valuable research topic in the field of soil science and land management. The Proximal Sensing (PS) technique offers a non-destructive and efficient method to assess wind erosion potential in arid regions. By using Partial Least Squares Regression (PLSR) and Support Vector Machine (SVM) models and combining soil texture and chemical properties, determined through Visible-Near Infrared (vis-NIR) spectroscopy in 96 soil samples, this study aims to predict soil erodibility, soil organic matter (SOM), and calcium carbonate equivalent (CaCO₃) in arid lands located in Elkobaneyya Valley, Aswan Governorate, Egypt. Results showed that the soil erodibility fraction (EF-Factor) had the highest values and possessed a strong relationship between slope and SOM of 0.01% in determining soil erodibility. The PLSR model performed better than SVM for estimating SOM, CaCO₃, and EF-Factor. Furthermore, the results showed that the spectral responses of CaCO₃ were observed in separate places in the wavelengths of 570, 649, 802, 1161, 1421, 1854, and 2362 nm, and the wavelengths with SOM parameter were 496, 658, 779, 1089, 1417, 1871, and 2423 nm. The EF-factor shows the highest significant correlation with spectral reflectance values at 526, 688, 744, 1418, 1442, 2292, and 2374 nm. The accuracy and performance of the PLSR model in estimating the EF-Factor using spectral reflectance data and the distribution of data points for both the calibration and validation data-sets indicate a good accuracy of the PLSR model, with RMSE values of 0.0921 and 0.0836 Mg h MJ⁻¹ mm⁻¹, coefficient of determination (R²) values of 0.931 and 0.76, and RPD values of 2.168 and 2.147, respectively. Full article

For large infrastructure projects, such as high-voltage underground cables or for evaluating the very shallow geothermal potential (vSGP) of small-scale horizontal geothermal systems, large-scale geothermal collector systems (LSCs), and fifth generation low temperature district heating and cooling networks (5GDHC), the thermal conductivity (λ) of the subsurface is a decisive soil parameter in terms of dimensioning and design. In the planning phase, when direct measurements of the thermal conductivity are not yet available or possible, λ must therefore often be estimated. Various empirical literature models can be used for this purpose, based on the knowledge of bulk density, moisture content, and grain size distribution. In this study, selected models were validated using 59 series of thermal conductivity measurements performed on soil samples taken from different sites in Germany. By considering different soil texture and moisture categories, a practicable guideline in the form of a decision tree, employed by empirical models to calculate the thermal conductivity of unconsolidated soils, was developed. The Hu et al. (2001) model showed the smallest deviations from the measured values for clayey and silty soils, with an RMSE value of 0.20 W/(m∙K). The Markert et al. (2017) model was determined to be the best-fitting model for sandy soils, with an RMSE value of 0.29 W/(m∙K). Full article

Unique worldwide, nitrate/iodine deposits (NIDs) are located along a 700 km geological belt in the Atacama Desert, Chile. They serve as the primary source of mineral ores for the extraction of iodine, sodium, and potassium nitrates. NIDs have been relatively underexplored from a biological perspective. To address this, we collected sixteen soil samples from abandoned mines in Oficinas Pissis and Savona for chemical, mineralogical, and metagenomic analyses. The soils primarily consisted of halite and darapskite, with only one sample being predominantly composed of thenardite. Deliquescence and water activity measurements yielded values ranging from 0.02% to 0.40% and 0.47 to 0.62, respectively. To investigate the presence, identification, relative abundance, and diversity of microbial life in NID soils, we employed MiSeq high-throughput sequencing and bioinformatic tools. The dominant phyla observed were Firmicutes and Proteobacteria, with Actinobacteria and Cyanobacteria being predominant in two soil samples. Furthermore, we detected nitrate/perchlorate-reducing bacterial activity in enriched cultures from the soil samples. This study sheds light on the resilience of microbial life in the Atacama Desert NIDs, providing compelling evidence for its existence and offering insight into factors that could facilitate it within this unique environment. Full article

There is an urgent demand to change our intensive crop production systems, replacing them with soil use and management systems that recover, preserve, or improve soil health and are environmentally sustainable, producing healthy and good-quality food. In this work, we compile and present strategies and public policies aimed toward soil and water conservation and food production in Brazil. The results presented may help Brazilian farmers adopt practices to recover, maintain, or improve soil health and politicians to create or modify public policies for healthy soil and food, without the necessity of increasing agricultural areas. Food insecurity was also addressed, with family farming playing an important role in food production and decreasing food insecurity. But these challenges need the combined efforts and engagement of the whole society. Full article

Integrated production systems composed of trees, crops and pastures have shown good results in improving soil quality and the capacity to store carbon in the soil, being efficient in mitigating greenhouse gas emissions. Despite this, changes in carbon stocks and soil organic matter fractions in the initial stages of implementing an agroforestry system remain unclear. This study evaluated the carbon balance and the dynamics of soil organic matter fractions in an agroforestry system conducted over a decade. Total carbon, labile carbon, carbon from particulate organic matter, organic carbon associated with minerals and inert carbon were determined at depths 0–10 cm, 10–20 cm and 20–40 cm. Soil carbon stocks were also estimated for the 0–40 cm depth. Total carbon increased in the agroforestry system compared with a low-productivity pasture. The total carbon stock in the last growing season (68.57 Mg ha⁻¹) was close to the original soil stocks under native Cerrado vegetation (76.5 Mg ha⁻¹). After 10 years, there was a positive balance in the soil carbon stock of both the total carbon and the soil organic matter fractions. The successional agroforestry system is a good alternative to increasing soil total carbon stocks and labile and non-labile fractions of soil organic matter. Full article

Soil parent material is a fundamental natural resource for the generation of new soils. Through weathering processes, soil parent materials provide many of the basic building blocks for soils and have a significant bearing on the physico-chemical makeup of the soil profile. Parent materials are critical for governing the stock, quality, and functionality of the soil they form. Most research on soil parent materials to date has aimed to establish and measure the processes by which soil is generated from them. Comparatively little work has been performed to assess the rates at which soil parent materials erode if they are exposed at the land surface. This is despite the threat that the erosion of soil parent materials poses to the process of soil formation and the loss of the essential ecosystem services those soils would have provided. A salient but unanswered question is whether the erosion of soil parent materials, when exposed at the land surface, outpaces the rates at which soils form from them. This study represents one of the first to detect and measure the loss of soil parent material. We applied Uncrewed Aerial Vehicle Structure-From-Motion (UAV-SfM) photogrammetry to detect, map, and quantify the erosion rates of an exposed saprolitic (i.e., weathered bedrock) surface on an agricultural hillslope in Brazil. We then utilized a global inventory of soil formation to compare these erosion rates with the rates at which soils form in equivalent lithologies and climatic contexts. We found that the measured saprolite erosion rates were between 14 and 3766 times faster than those of soil formation in similar climatic and lithological conditions. While these findings demonstrate that saprolite erosion can inhibit soil formation, our observations of above-ground vegetation on the exposed saprolitic surface suggests that weathered bedrock has the potential to sustain some biomass production even in the absence of traditional soils. This opens up a new avenue of enquiry within soil science: to what extent can saprolite and, by extension, soil parent materials deliver soil ecosystem services? Full article

Interest in improving the long-term sustainability of agricultural production systems has focused on identifying management practices that promote soil health. No tillage, cover cropping, and amending soils with broiler (Gallus gallus domesticus L.) litter are commonly adopted conservation practices that have been shown to improve soil fertility and crop yield. However, the overall influence of these conservation practices on soil health in the southeastern US are not well understood. Thus, a study was conducted to evaluate the influence of tillage, broiler litter (BL) applications, and cropping systems on soil biochemical properties. Soils were collected from field research plots under long-term management (>than 25 years of tillage, 15 years of broiler litter application, and 15 years of cropping system). Soil microbial biomass, C, N, and P, amidohydrolases, and dissolved organic matter (DOM) were evaluated as indicators of soil health. Adopting tillage and BL into the agricultural management system modified the biochemical parameters of the soils evaluated. Most of these modifications occurred in the 0–5 cm depth. Higher microbial biomass carbon (MBC; 85%) and nitrogen (MBN; 10%) and enzyme activities of asparaginase (65%) and glutaminase (70%) were observed in the 0–5 cm depth under no tillage (NT) compared to conventional tillage (CT), indicating greater biological activities were established in these soil ecosystems. Broiler litter applications increased microbial biomass N and activities of asparaginase and glutaminase in both soil depths. In addition, microbial biomass phosphorus (MBP) was increased following BL application in the 0–5 cm depth. The results suggest that long-term management of NT and BL additions can improve the health of eroded southeastern US soils by altering the soil biochemical parameters. Full article

This study aimed to investigate the impact of biosolids-derived biochar on the remediation of Australian soil contaminated with diesel while investigating the role of biochar in the remediation. To achieve the latter aim, sodium azide (NaN₃) was added to a separate biochar treatment (BN) to alter the bacterial community structure. Biochar (B) reduced detectable hydrocarbons by 2353 mg/kg compared to the control (C) treatment at week 24. However, the BN treatment reduced the hydrocarbon concentration by 3827 and 6180 mg/kg, relative to B and C, respectively. Soil toxicity significantly decreased at week 24 compared to the start of the remediation in B, but not in the control. Biochar and control treatments generally showed a similar bacterial community structure throughout the incubation, while the bacterial community structure in BN differed significantly. Biodegradation was found to play a significant role in hydrocarbon removal, as the variation in the bacteria community coincided with differences in hydrocarbon removal between B and BN. The increased removal of hydrocarbons in the BN treatment relative to B coincided with increased and reduced relative abundances of Gordonia and JG30-KF-CM45 genera, respectively. This study showed that NaN₃ led to a transient and selective inhibition of bacteria. This study makes an important contribution towards understanding the use of NaN₃ in examining the role of biochar in the remediation of diesel-contaminated soil. Overall, we conclude that biochar has the potential to enhance the remediation of diesel-contaminated soil and that biodegradation is the dominant mechanism. Full article

The use of plant growth-promoting rhizobacteria (PGPR) inoculated on plants has shown that it can increase the success of reforestation and accelerate soil recovery by improving soil microbial diversity. Three PGPR isolated from natural pine populations were selected for their metabolic capabilities and taxonomic affiliation (Z4.3; Bacillus sp., Z5.4; Arthobacter sp., and Z7.15; and Pseudomonas sp.) when inoculated alone or in combination (consortium) on stone pine seedlings before transplanting to the field. Before transplanting and after nine months, rhizospheric soil samples were collected for structural and functional metagenomic studies. First, the data were analyzed using EasyMAP. Neither alpha nor beta diversity showed significant differences between the samples, although unique taxa representative of each sample were detected. The predominant phylum in all cases was Proteobacteria, followed by Bacteroidetes and Acidobacteria. The linear discriminant analysis (LDA) effect size (LEfSe) found significantly over-represented taxa in some samples, highlighting different representatives of the order Sphingomonadales in several of them. Functional inference performed with PICRUSt also showed significantly over-represented functions in some samples. The study demonstrates that PGPR have a positive effect on plants and cause detectable changes in microbial communities in terms of both structure and function. Full article

The soils of the high-elevation mountains along the East African Rift Valley are poorly understood. Assessing the potential of soils for agriculture, climate change mitigation, and environmental functioning requires insight into how they relate to the factors influencing soil formation. Between 3000 and 4120 m a.s.l., 85 soil profiles of Mount Guna were described and sampled. Standard physicochemical analyses were done on all pedons. Additionally, X-ray diffraction, Al_ox and Fe_ox content, and P fixation were performed on six selected profiles. Soils on Mount Guna included Andosols, Phaeozems, Leptosols, Regosols, Cambisols, Luvisols, and Vertisols. With increasing elevation, clay content, bulk density, and pH decreased while the C:N ratio remained constant. In contrast, sand, silt, silt-to-clay ratio, SOC, Ntotal, and SOCS increased. With a factor analysis, the soil-forming factors’ elevation/climate could be disentangled from the factor’s parent material as these affect topsoil and subsoil differently. In the ordination based on climate/elevation and parent material, Andosols and Vertisols stood out while other Reference Soil Groups (RSG) showed indistinct patterns. Soil erosion appeared as an additional soil-forming factor not accounted for by the factor analysis. The distribution of the RSG was significantly associated with elevation belts (p < 0.001), lithology (p < 0.001), and landcover (p < 0.003). On the summital ridge, the Andosols were crucial for groundwater storage due to high precipitation. Shallow and stony soils in the mid-elevation belt contributed to runoff generation. Average soil carbon stock ranged from 8.1 to 11 kg C m⁻² in the topsoil and from 29.2 to 31.9 kg C m⁻² in the upper meter, emphasizing the global importance of high-elevation areas for carbon sequestration. Full article