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ABSTRACT Serra da Saudade Formation corresponds to the upper part of the stratigraphic column of the Bambuí Group. Few studies have addressed the soil properties and pedogenesis of the pelitic rocks rich in potassium minerals of this formation. This study analyzed siltstone-derived soils, some of which are glauconitic (green siltstone; “verdete”), to understand the role of the main pedogenetic factors and processes in the landscape of the Central-West region of the Minas Gerais State, covered by Cerrado vegetation. Nine soil profiles were described, and their morphological, physical, chemical and mineralogical properties were analyzed. Soils were classified as Neossolos Litólicos (P1, P3, P6, P8 and P9), Cambissolos Háplicos (P2 and P5), Argissolo Vermelho-Amarelo (P4) and Argissolo Acinzentado (P7). The main active pedogenetic processes identified in the study area are melanization, goethization, argiluviation and elutriation. These are essentially controlled by the nature of the parent material and position of the soil in the relief. Soils are typically shallow, dystrophic, highly Al-saturated and contain essentially quartz and micas in the coarse fractions (sand and silt) and illite/glauconite and kaolinite in the clay fraction. In soil environments with siltstone and green siltstone under “dry forests”, the soil water pH was higher and high levels of exchangeable calcium and magnesium, a eutrophic character and high-activity clay were observed. Barium, chromium, lead and zinc contents were high in all studied soils. Green siltstone-derived soils have peculiar physical and chemical properties, divergent from those developed from other glauconitic rocks on the Earth surface. However, greenish tones in horizons are common in all these soils.

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ABSTRACT Application of pig manure (PM) in agriculture can influence the amount and composition of soil organic matter (SOM). This study evaluated the changes in contents and stock of C in chemical fractions of SOM and the chemical and spectroscopic composition of humic substances (HS) in a Typic Hapludult (Argissolo Vermelho-Amarelo) after ten years of PM application. Experimental area received 90 and 180 kg ha-1 of N in the form of pig slurry (PS90 and PS180) and pig deep litter (DL90 and DL180), in addition to the control, without application (SA). Soil samples were prepared, and the chemical fractioning of SOM, elemental analysis, and Fourier Transform Infrared Spectroscopy of HS were performed. Applications of PM favored the accumulation of C in soil (up to 53 %), and PS180 increased humic acids (HA) (up to 185 %), while applications of DL favored the increase of hydrophilic substances extracted with HCl and humin (HU) (up to 10 times and 60 %, respectively). Applications of PS180 and DL180 promoted an increase in the aromatic and carboxylic character of the HS, increasing cationic exchange capacity. Therefore, PM applications, especially with DL, contribute positively to C fixation in the soil and the chemical composition of organic material.

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ABSTRACT Soil legacy data is past information on soils available from various sources (e.g. survey reports and maps). When compiled and organized, data obtained through historical retrieval can be used as basic input or validation data for digital soil mapping. A bibliometric analysis of this topic can reveal research patterns, evolution, and scientific contribution, thus mapping the science produced in a specific period and determining the trend in research topics based on search terms. This article presents the characterization of international scientific production on soil legacy data using a set of bibliometric indicators. The study was developed with the bibliometric analysis of scientific articles indexed in the Web of Science and Scopus data platforms regarding the use of soil legacy data published online from 1979 to 2022. The following were extracted from the articles: authors and co-authors, year and country of publication, index words used, and abstracts, which were submitted to bibliometric analysis in R. Bibliometric analysis revealed publication of 242 scientific articles in 117 journals involving 1223 authors throughout the world in the last 43 years, with an average frequency of 12.66 citations per article. Australia (10.33 %), the USA (8.68 %), and Brazil (7.85 %) were the countries with the greatest scientific contributions. The most cited studies refer to databases, demonstrating the ease of access to information contributes significantly to new local studies. Due to pedometrics importance for soil science, there is constant revision to available legacy data for new hypotheses and research in soil science. And also, for the monitoring of soil attributes for the conservation and preservation of natural resources.

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ABSTRACT Soil fauna organisms participate in a series of processes that benefit the physical and chemical soil properties; however, little is known about their spatial variability and scale. This study aimed to characterize the spatial variability of soil fauna from multifractal and joint multifractal analysis in Brazilian Savanna areas. Pitfall traps collected soil fauna in two Savanna formations (dense Savanna and typical Savanna) in two transects with 128 points. Organisms were identified and classified into functional groups (Microphages, Pollinators, Predators and Social), and then Ind trap−1 day−1 (number of individuals per day in the sample) and Richness were determined. Data were analyzed using multifractal and joint multifractal analysis, and the scale indexes f(α,β) were generated for the singularity indexes of α(q,t) and β(q,t), considering Ind trap−1 day−1 and Richness as predictive variables. A total of 3456 and 1629 individuals were collected from T1 (dense Savanna) and T2 (typical Savanna), respectively. The singularity spectrum for soil fauna showed the greatest difference in dimensions D−10–D10 for the functional group Pollinator (D−10–D10 = 0.936) in T1 and for Social (D−10–D10 = 0.620) in T2, reflecting more heterogeneous systems. The joint multifractal dimension showed a high correlation between Ind trap−1 day−1 and the functional groups (Pollinators, Predators, and Social) in T1, demonstrating how phytophysiognomy of this experimental plot (dense Savanna) favors the presence of these organisms and reflects the spatial correspondence of the measurement values along the geometric support. Abundance of organisms (Ind trap−1 day−1) and Richness were promising variables to represent the set of relationships with the functional groups of soil invertebrate fauna. In general, multifractal analysis using abundance and Richness can assist in decision-making focused on conserving Savanna areas.

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ABSTRACT Soil is an important carbon repository in terrestrial ecosystems, serving a fundamental role in the intricate cycling of this elemental component. Wetlands are crucial components of the global carbon cycle, playing a significant role in carbon sequestration due to their remarkable productivity and unique sedimentary structures. Our study focuses on the wetlands east of Marajó island, recognized as the largest fluvial-marine plain in South America. In this study, we applied a methodological framework to optimize SOC content prediction in the wetlands of Marajó island using readily available environmental covariates. We collected and analyzed 81 soil samples from the most representative geoenvironments on the island at a layer of 0.00-0.20 m. Our database included vegetation indices, morphometric maps, and covariates based on distance from water bodies and archaeological sites. We tested five machine learning algorithms - Cubist, Linear Model, Random Forest, K Nearest Neighbor, and Support Vector Machine - to obtain the best prediction performance. Cubist model demonstrated the highest performance for training (R2 = 0.483) and testing (R2 = 0.505) datasets, making it the optimal choice for SOC prediction in the topsoil. The most important covariates selected by Cubist using recursive feature elimination were digital elevation model, topographic heterogeneity index, vertical distance between the summit and base of the slope, and Euclidean distance from water bodies. Geoenvironments characterized by dense alluvial rainforest with palms on Plinthosols and Gleysols, mangroves with Gleysols, and coastal muddy plains exhibited the highest SOC content in the topsoil.

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ABSTRACT Carbon flows into and out of the soil are important processes that contribute to controlling the global climate. The relationship between soil organisms and the climate is interdependent since the organisms that contribute to carbon and greenhouse gas fluxes are simultaneously affected by climate change and soil management. Temperature, soil moisture, pH, nutrient level, redox potential and organic matter quality are key elements affecting the microorganisms involved in organic carbon flows in the soil. Climate, topography (slope and position in the landscape), soil texture, soil mineralogy and land-use regulate those key elements and, thus, the C fluxes in the pedosphere. Soil microbes can increase carbon influx and storage by promoting plant growth, mycorrhizal establishment, and particle aggregation. Conversely, microorganisms contribute to carbon efflux from the soil via methanogenesis, rhizospheric activity, and organic carbon mineralization. Nevertheless, strategies and management practices could be used to balance out carbon emissions to the atmosphere. For example, carbon influx and storage in the soil can be stimulated by plant growth promoting microorganisms, greater plant diversity via crop rotation and cover crops, cultivating mycotrophic plants, avoiding or reducing the use of fungicides and adopting organic farming, no-tillage crop systems and conservative soil management strategies. Therefore, this review aimed to shed light on how soil microorganisms can contribute to increase C influxes to the soil, and its significance for climate change. Then, we also seek to gather the practical actions proposed in the scientific literature to improve carbon sequestration and storage in the soil. In summary, the review provides a comprehensive basis on soil microorganisms as key to carbon fluxes and helpers to lessen climate change by increasing carbon fixation and storage in agroecosystems via stimulation or application of beneficial microorganisms.

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ABSTRACT Theobroma cacao, the source for chocolate fabrication, is a high-value crop that faces challenges such as the impact of climate change, pathogens, and cadmium accumulation. Soil associated with T. cacao has been extensively studied, looking for bio-controllers and microorganisms capable of Cd accumulation. However, there is no information about the microbial structure and interactions occurring in soil associated with cacao wild relatives, which represent a repository for biological diversity and its potential for biotechnological applications. We performed an extracellular DNA metabarcoding on soil samples associated with Theobroma spp. and Herrania sp. plants in two localities of the Biogeographic Chocó. We found microbial high diversity indexes and no correlation with plants or sampling locations. Potential cacao pathogens and bio-controllers and unexpected differences in the physicochemical soil properties from close locations were detected. Cadmium, an important economic factor for the commercialization of cacao products, showed significant differences between locations associated with a particular Theobroma species. We discuss some important relationships with soil physicochemical properties, the urgent need to complete the missing information on the diversity of bacterial, fungal and insect groups, and the potential of comprehensive analyses for decision-making regarding land-use and vocation. Also, we did not find the only T. hylaeum tree after three years, evincing the urgent need for conservation strategies in Colombia’s Chocó region.

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ABSTRACT Physical properties of the Technosols formed by the tailings deposition may constitute a physical barrier that limits water movement and plant development due to the properties received from those sediments. This study aimed to evaluate the physical quality of the Technosols formed by the deposition of sediments displaced by the Fundão Dam failure, Mariana, Minas Gerais State, Brazil, based on the evaluation of physical properties and Load Bearing Capacity Models (LBCM). For that, three areas under different vegetation types were selected: eucalyptus (Euc), forest with human-assisted revegetation (RF), and forest with native vegetation (NF). Three sampling subareas were demarcated in each area: non-impacted areas (Ni), and Technosols formed in directly impacted areas (Di), and partially impacted areas (Pi). Undisturbed samples were collected in two layers and subjected to the uniaxial compression test after equilibration at five matric potentials. Soil compression curves and LBCM were determined. Soil bulk density (BD), total porosity (TP), organic matter (OM), granulometry, and particle density (PD) were also determined. Clay content was less significant, and the silt and very fine sand content was significantly higher in the Technosols, generating an increase in BD and reduction in TP. Technosols generally exhibited greater load-bearing capacity due to higher pre-consolidation pressure values attained by these soils due to the lower clay and OM contents. High resistance of these soils is one limitation for revegetation of the areas evaluated, being necessary management practices to improve physical properties of the Technosols.

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ABSTRACT Shaded coffee systems may offer a series of benefits, however, studies on shaded cultivation of Conilon coffee crops are still scarce in the literature. This study aimed to evaluate the soil physical, chemical, and biological properties of two Conilon coffee intercropping systems from southeastern Brazil. Two commercial coffee crops – one shaded by macadamia trees and the other by green dwarf coconut trees – were evaluated according to three treatments: coffee plants in the inter-row of the tree species; coffee plants in the same row of the trees; and unshaded coffee. The experimental design was a completely randomized with four replicates. Coffee plants intercropped with macadamia trees, both intra- and inter-row, resulted in less soil compaction than unshaded systems. As for intercropping with green dwarf coconut trees, the unshaded system presented lower soil resistance to penetration. Differences in physical properties between treatments allow no inferences about intercropping systems influence on green coconut trees. Intercropped coffee improves soil chemical properties, resulting in greater soil fertility than unshaded systems, and showed greater soil organisms. These findings indicate that Conilon coffee-macadamia intercropped with tree species represents a promising alternative for sustainable soil management.

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ABSTRACT Few Brazilian rural landowners are aware of the technology available to survey the subsoil of terrains earmarked for aquaculture operations. This study evaluated subsoils of Monte Alegre (area 1) and Montenegro 3 (area 2) aquaculture zones in the geographic region of Bragança (Amazon region, northern Brazil), and the adequacy of these areas for aquaculture. Ground Penetrating Radar, electrical conductivity measurements, and sedimentological analyses were applied to evaluate the subsoil of fish farms. Apparent conductivity values recorded by the Electromagnetic Induction (EMI) in area 1 indicated possible presence of clayey soils. Excavation analysis and sedimentological samples (sand) from this site confirmed the inadequacy of the terrain. The EMI tool in area 2 indicated possible presence of clayey soils. Geophysical and sedimentological results from the site confirmed its suitability. These geophysical tools are recommended for evaluating prospective aquaculture sites, given their capacity to provide reliable data on the subsoil characteristics , which is essential to guarantee the success and sustainability of aquaculture operations.

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ABSTRACT In hydrological modeling and for the development of projects related to soil and water conservation and civil engineering, determination of water infiltration variables into the soil plays a key role. However, measuring infiltration with manual infiltrometers is work-intensive and requires several people, which casts doubts on the consistency of the process description. Our objective was to develop automated and compact systems for data acquisition by double-concentric-ring and Cornell infiltrometers. The systems are based on air differential pressure sensors and microcontrollers using open-source software and a simple construction. We developed ten sets of automatic infiltrometers for each method that were properly calibrated. The equipment was validated in the field, and the alignment of the automatically measured with the hand-measured infiltration data was considered satisfactory. The proposed systems make data records of infiltration and associated variables possible, with less operator dependence than manual measurement strategies. In addition, the enhanced resolution resulting from infiltrometer automation makes the infiltration curve more representative, especially in the initial infiltration stage.

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ABSTRACT Regosols (Neossolos) are soils with use limitations mainly related to effective depth, abundant presence of rock and saprolite fragments, and frequently high slope gradients; besides that, they represent a new agricultural frontier for grain production in southern Brazil. This study evaluated soil saturated hydraulic conductivity (Ksat) and water retention and availability in Regosols and saprolites derived from volcanic rocks in southern Brazil and the relationship of these variables with porosity in saprolithic horizons characterized by mineralogical weathering. The study was carried out on eight profiles derived from basic and acidic volcanic rocks of the Serra Geral Formation. We evaluated soil morphology, granulometry, porosity, bulk density (BD), Ksat, water retention, electronic/ optical microscopy and chemical composition of parent materials, and soil mineralogy. Soil Ksat ranged from 0.0 to 6.40 cm h-1 in the evaluated horizons, without significant difference between the A and Cr horizons. Seven soil profiles showed BD equal to or less than 1.28 Mg m-3 for the Cr samples. Total porosity in the Cr horizons was above 0.5 m3 m-3 and not significantly different from A horizons. In five of the eight soil profiles, one or more Cr horizons presented greater available water than A horizons. Electronic and optical microscopy evidenced abundant cracks and mineralogical weathering in the rock samples. X-rays diffraction data also indicated advanced degree of weathering of Cr horizons, evidencing abundant formation of pores in the saprolite. and justifying the high-water retention in Regosols profiles in southern Brazil.

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ABSTRACT Kaolinite is the main clay mineral in most soils around the world and has been widely used for industrial purposes. This research aimed to study chemical, morphological and crystallographic characteristics of kaolinite, and establish the origin of kaolinitic samples on Serra do Mar and kaolinitic layers on peatlands, located at Southern Brazil. Samples were collected on different geomorphological positions: two samples at Serra do Mar (kaolinitic saprolite – SAP, and kaolinitic layers - KL); and two cores at the peatland with Sapric Histosols from Quaternary sedimentary basin. Granulometry and total organic carbon (TOC) were determined in soil samples. Kaolinite in silt and clay fractions was studied by chemical extractions, X-ray diffraction (XRD), thermal analysis (DTA/TG), and scanning electron microscopy with energy dispersive spectroscopy – SEM/EDS. Chemical and mineralogical characteristics of kaolinite were divided into two groups, according to the particle size and the location of the deposit in the relief. Silt fraction: i) SAP – genesis mainly derived from mica weathering; ii) peatland, containing pseudomorph crystals smaller than those found in Serra do Mar; Clay fraction: i) Serra do Mar – there was a larger contribution of K-feldspar weathering in the genesis of kaolinite from KL in relation to SAP; ii) peatland – the stronger weathering and the hydromorphic conditions resulted in less neoformed crystalline kaolinites. For both environments, the substitution of Al3+ by Fe3+ into the octahedral sheet led to a reduction in the mineral thickness and also increased the occurrence of structural deformations in clay kaolinite. Kaolinite in peatland is a combination of the following genesis processes: transportation from Serra do Mar (mainly in the silt fraction) and; formation in situ through neogenesis process (dominant in the clay fraction).

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ABSTRACT Increasing the use of nitrogen (N) fertilizers will be necessary to enhance grain and pasture yields to satisfy the growing world demand for food. Organic amendments, such as farm dairy effluents (FDE), are an alternative to traditional synthetic fertilizers. However, part of the applied N could be lost as ammonia (NH3) volatilization or nitrous oxide (N2O) emission, decreasing N availability to plants. Nitrification inhibitors, such as dicyandiamide (DCD), suppress the microbial process of nitrification, decreasing soil nitrate concentration and, therefore, N2O emission. Reducing N2O losses from agricultural soils is a key subject for sustainable production. This research aimed to quantify the effect of DCD addition to the FDE on the emissions of N2O and the volatilization of NH3 from the soil. A field trial was carried out in which NH3 volatilization and N2O emission were measured over 49 days after applying FDE, FDE with DCD (DCD), and control (C, without N added) treatments. The amount of N applied as FDE was 120 kg of N ha-1. Accumulated N2O emission during the 49 days after the application was 526, 237, and 174 g N2O-N ha-1 from the soil in the FDE, DCD, and C treatments, respectively. No significant differences were observed in accumulated NH3 volatilization. Pasture yield was higher in DCD treatment, followed by C and FDE. Under low temperatures and high soil moisture conditions, adding DCD to the FDE could be considered an effective alternative to increase pasture yields, decrease N2O emissions, and maintain NH3 volatilization, reducing total N losses to the atmosphere by about 14 %. Adding DCD to the FDE is a promising alternative for the more efficient N use of farm dairy effluents as fertilizer to mitigate N losses, tending to reduce N losses as N2O emissions. More studies are necessary to verify the result of using FDE + DCD under different soils and climates.

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ABSTRACT Peanuts are mainly grown in sandy soils with low boron content, which may limit the crop yield, especially runner-type cultivars that have high-yields. Boron deficiency causes hollow heart in peanut seeds, reducing yield and seed quality, but the best strategy to supply boron to peanut is still not known. This study aimed to evaluate peanuts nutrition, yield, and seed quality as a function of boron rate, source, and application form. The study was conducted for two years in sandy soils with low boron in southeastern Brazil. Treatments included application of boron via soil: control (boron unfertilized), boric acid at 1.5 kg ha-1 of B, Ulexite (1.5 and 3.0 kg ha-1 of B), and sodium tetraborate (1.5 and 3.0 kg ha-1 of B) combined with foliar fertilization (sub-plots): 0, 400, 800 and 1200 g ha-1 of B (boric acid) with four replicates. Boron fertilization via soil and foliar increased peanuts yield by 20 % (1100 kg ha-1) and 14 % (700 kg ha-1) - the average of the two crops, respectively. Combined use of soil and foliar fertilizer was justified only in years with water deficit and when the rate applied via soil was low (<3.0 kg ha-1). Boron application via soil or application of 400 g ha-1 of B via foliar fertilization increased seed germination rate by 10 to 13 %. Boron fertilization increased the percentage of normal seedlings, seedling weight, and length and reduced the germination time. Foliar and soil boron applications efficiently improved peanut seed nutrition, yield, and quality. However, soil application performed better, showing a higher percentage of yield increase.

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ABSTRACT Widespread use of soluble mineral fertilizers derived from non-renewable sources has raised concerns about environmental impacts, energy expenditures, and sustainability. Combining biosolid and mineral sources of phosphorus and potassium to produce organomineral fertilizers (OMF) can be used as an alternative nutrient source while reducing the environmental impact of sewage residues. As this approach simultaneously provides nutrients and incorporates organic matter, we hypothesized the presence of an organic source (biosolid) granulated with mineral sources of potassium (K) and phosphorus (P) would reduce leaching due to the benefits of the organic source and the slower release caused by granulation. Our goal was to evaluate the effect of different OMFs on the leaching losses of nutrients. Two forms of isolated N, P, and K sources (granulated and non-granulated), five OMFs with different NPK proportions (1-2-0, 1-4-0, 1-0-2, 1-2-2, 1-2-4), and a control (unfertilized) were evaluated over ten weeks in a leaching column experiment. Non-granulated potassium sulfate exhibited the highest K leaching and did not differ from OMFs with K in their formulation (granulated PS, 1-0-2, 1-2-2, and 1-4-2). Planned contrasts showed that granulation was particularly effective at reducing K leaching, resulting in a 70 % reduction compared to non-granulated PS. While formulation and granulation showed a trend of potential benefits in reducing N-(NO3- + NO2-) leaching, the effect was not statistically significant. Interaction between fertilizer treatments and leaching events was marginally significant for NH4+ leaching, indicating temporal variations of OMFs in nutrient dynamics may be influenced by mineralization. As granulation modulated how OMFs affected nutrient leaching dynamics, this highlights the importance of the physical characteristics of fertilizers for effective nutrient management.

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ABSTRACT One of the challenges in the peach palm production system is the interpretation of leaf analyses and the adaptation of fertilization recommendations. Tools that enhance fertilizer use efficiency are therefore needed. This study aimed to establish norms for evaluating the nutrient status of peach palms using the Diagnosis and Recommendation Integrated System (DRIS) and to determine the adequate number of palm heart samples necessary for a more accurate assessment of productivity. Production, leaf nutrient content, and soil fertility data were collected from 102 commercial stands of peach palm in the Ribeira Valley, state of São Paulo, Brazil, between 2015 and 2020. Adequate number of individual samples (palm hearts) to be collected per stand for productivity assessment was estimated. DRIS norms were established by dividing the database into high-yield (reference population) and low-yield subpopulations, using average productivity as a criterion. By assuming an acceptable error of 5 to 10 % for the assessment of peach palm productivity, taking into account total palm heart weight and/or the weight of cylinders, respectively, 16 plants per stand should be sampled. DRIS was not sensitive enough to diagnose differences in the probability of positive response to fertilization; however, the P, K, Ca, Mg, S, B, Fe, Cu, Mn and Zn contents were positively correlated with the respective nutrient indices.

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ABSTRACT Increasing soybean yield in the MATOPIBA region can be attributed to fertility management, which is crucial to achieving maximum agronomic efficiency. Therefore, the proper management begins with the assessment of plant nutrition. This study aimed to evaluate soybean nutritional status in western Bahia using the Diagnosis and Recommendation Integrated System (DRIS). Database comprised 153 samples from commercial fields located in the research area. To carry out the evaluation using the DRIS method, the database contained information on nutritional levels and leaf productivity of the sampled areas. Database was divided into high-productivity populations (reference population) and low-productivity populations, based on the inflection point value of the cumulative cubic function of yield. The DRIS method allowed for evaluating the potential response to fertilization; however, this method was inefficient in recommending fertilizer doses in both subpopulations. For the sufficiency levels proposed by DRIS, the nutrients N, K, Ca, Mg and S had their maximum and minimum limits reduced, while Cu, Fe and Zn had their ranges of sufficiency expanded, when compared with ranges proposed by other authors. In addition, Zn and Mn were more limiting due to lack for the high-yield subpopulation, and P and Mn for the low-yield subpopulation. The most limiting nutrients due to excess were P and Zn for the high-yield, while K and S were limiting for the low yield subpopulation.

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ABSTRACT The performance of colorimetric methods for P quantification has been overlooked by researchers for decades. We investigated the performance of two blue colorimetric methods for P quantification, Braga and Defelipo (B&D) and Murphy and Riley (M&R), using two commonly soil P extractants, Mehlich-1 (M1) and Mehlich-3 (M3). Specifically, we evaluated the color development time and its stability in different soil extractant solution proportions (1:1 or 1:4 v/v), the optimum wavelength, limits of detection, and element quantification. Our results indicate that M3 leads to lower limits of detection and quantification for both colorimetric methods, particularly for B&D. For M1, the volumetric ratio (1:1 or 1:4) did not influence color development and both B&D and M&R methods showed a fast color development. However, B&D showed greater color stability (from 5 to 600 min) and an optimum wavelength of 711 nm, while M&R was stable from 27 to 600 min an optimum wavelength of 889 nm. For M3 soil extractant, there are important issues, such as M&R being unstable and B&D presenting slow color development. In addition, the spectral profile obtained from soil extractant was different from the one obtained by the calibration curve without soil for both M&R and B&D. Therefore, the adoption of original methods on P quantification in M3 extracting solution represents a potential source of error, leading to wrong P fertilizer recommendations. Thus, the best option for P quantification in M3 extracts seems to be the use of Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES).

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ABSTRACT Garlic (Allium sativum) is normally grown under conventional tillage (CT) with soil being excessively mixed by plowing and harrowing operations that degrade soil structure, increase production costs, and increase environmental contamination. Alternatively, cover crops can be grown and their residues placed on soil surface, enabling garlic to be grown under no-tillage (NT) system. However, for subtropical climate there is little information on the impacts of tillage systems and cover crop species, particularly of their decomposition process and nutrients release, on garlic nutritional status and yield. This study aimed to evaluate garlic yield, and the decomposition rate and nutrient release from aboveground residues of cover crops cultivated in CT and NT methods, in a subtropical climate. Pearl millet (Pennisetum glaucum), bean (Phaseolus vulgaris) and sunn hemp (Crotalaria ochroleuca) were cultivated as cover crops previous to garlic, under CT or NT, for two consecutive years in the same area. The highest dry matter yield and nutrient release by cover crops were observed for millet and sunn hemp. The highest accumulations of P and K were observed in millet residue. Total garlic yield averaged 16.2 Mg ha-1 yr-1 and was affected neither by tillage method nor by cover crop species. The yield of marketable garlic was higher when soil was covered with bean residue in NT. Yield of non-marketable garlic was higher under CT in the first year, when high precipitation occurred shortly before harvest. The highest residue decomposition and nutrient release rates were observed under CT, in the three cover crop species. No-tillage increases marketable yield of garlic and the residence time of cover crop residues. We recommend cultivation in NT systems using cover crops, thus increasing marketable garlic yield and nutrient cycling.

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ABSTRACT Macaw palm (Acrocomia aculeata) is a widespread tree in Brazil, and the oil industry has been increasing interest in this tree due to its high oil concentrations, rusticity, and adaptability to different environments. Currently, macaw palms are being domesticated and are in an early rational cultivation process. Foliar diagnosis can contribute to managing fertilization, but there is no protocol for leaf sampling. This study aimed to evaluate the seasonal variation of leaf nutrient contents and indicate an adequate period for leaf sampling. Leaf contents of macro (N, P, K, Ca, Mg and S) and micronutrients (Cu, Mn, Fe and Zn) from composed samples of leaflets collected from the middle part of the tenth leaf were evaluated in 12 uninterrupted sampling times (January to December 2016). The data were submitted to analysis of variance. The distance from Mahalanobis and Tocher optimization methods was used to group sampling times of similar seasonal variations. Contents of N, P, K, Ca, S, Mn and Fe varied throughout the months. May and June are adequate to sample diagnostic leaves of macaw palm to analyze the nutritional status. Seasonal variation of N, S and Ca mostly contributed to the indication of leaf sampling time of macaw palm.

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ABSTRACT Diversifying pastures with forage legumes may reduce nitrogen fertilization due to biological N fixation. This study aimed to quantify forage accumulation rate and macronutrients extraction and to identify the best intercropping combination between butterfly pea (Clitoria ternatea) – a legume, and three warm-season forage grasses of different growth habits (signalgrass – Urochloa decumbunes, Guinea grass - Mega thyrsus maximus, and bermudagrass Cynodon dactylon). Treatments consisted of mixes of perennial herbaceous legume, butterfly pea (twining stem), with grasses, signalgrass (decumbent stem) and Guinea grass (erect stem), and bermudagrass (stoloniferous/rhizomatous). The experiment was arranged in a randomized complete block design, with three treatments and three replications. There was interaction between the intercropping combinations and cutting cycles for forage accumulation rate (FAR) and N, P, K, Ca, Mg, and S uptake. Phosphorus and K uptake was reduced from the second cycle onwards, except for the signalgrass-butterfly pea intercropping, whose reduction was only from the third cycle. Conversely, the signalgrass-butterfly pea and bermudagrass-butterfly pea intercropping did not differ from each other in relation to total N concentration in soil, but the signalgrass-butterfly pea intercropping showed total N concentration in soil higher than that of Guinea grass-butterfly pea intercropping. A higher predominance of the N-NH4+ form was observed in the soil. Grass-legume intercropping increased the demand for nutrients, which makes it indispensable to verify the export of macronutrients to know when to supply these nutrients removed from the soil solution.

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ABSTRACT Alternative materials can be used to reduce reliance on mining for P-based fertilizers. In this sense, the pyrolysis process of bovine bones produces the “bone char”, which can be used as a source of P. This study aimed to characterize bone char and conduct a comparative analysis with both soluble (triple superphosphate) and non-soluble (Bayóvar phosphate rock) phosphate fertilizers, specifically examining its behavior in soil and uptake by plants. Bone char characterization was performed by X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy coupled with energy-dispersive (SEM-EDS). The XRD analyses have shown the presence of hydroxyapatite in the bone char, bands assigned to P-O stretching from phosphate have been observed in ATR-FTIR, and Ca, P, C, and O elements were identified in the materials by EDS analyses. Solubility from fertilizer extractants was higher for bone char compared to Bayóvar, and both sources showed lower solubility compared to triple superphosphate. Cumulative amount of P released from bone char was higher than Bayóvar and lower than triple superphosphate. Amount of total dry matter, total shoot P uptake, and total shoot Ca uptake were higher for triple superphosphate compared to bone char and Bayóvar. Release profile of P from bone char strongly suggests this material can be used as a slow-release P source, with intermediate solubility between soluble and non-soluble commercialized sources.

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ABSTRACT From 1913 onwards, the global situation changed from a scenario of nitrogen (N) scarcity to an abundance of ammonia (NH3) produced synthetically via the Haber-Bosch process. Several N compounds have been synthesized since then, with urea becoming the main source of N, accounting for 55 % of current N consumption. However, N efficiency in agroecosystems is low and, normally, N recovery in cultivated plants is less than 50 %. This occurs because a large amount of reactive N is lost to the environment, inducing various forms of pollution, threatening human and environmental health, in addition to causing a negative economic impact on the farmer. The main processes responsible for low N efficiency are NH3 volatilization, leaching, and N denitrification. Considering global NH3 volatilization losses of 14 %, it can be assumed that up to 8.6 million Mg of urea are lost every year in the form of NH3. For each ton of NH3 produced, 1.9 to 3.8 Mg of CO2 is emitted into the atmosphere. Therefore, increasing N use efficiency (NUE) without compromising yield is a necessity and a challenge for crop improvement programs and current management systems, in addition to reducing greenhouse gas emissions. In this context, enhanced efficiency fertilizers (EEFs), which contain technologies that minimize the potential for nutrient losses compared to conventional sources, are an alternative to increasing the efficiency of nitrogen fertilization. Currently, EEFs are classified into three categories: stabilized, slow-release, and controlled-release. This study aims to understand the technologies used to produce EEFs and the factors that govern their availability to plants. This review covers the following topics: the discovery of N, N dynamics in the soil-atmosphere system, N assimilation in plants, strategies to increase NUE in agrosystems, NH3 synthesis, NH3 volatilization losses, N fertilizer technologies, the importance of characterization of EEFs, conventional nitrate or ammonium-based fertilizers to reduce gaseous losses of NH3 and future prospects for the use of N fertilizers in agriculture.

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ABSTRACT Land-use changes from native pastures to forest plantations in humid temperate areas have raised concerns about their potential impact on the environment. This study aimed to assess the effects of such changes on soil water properties, focusing on the impact of the forest species planted and their relationship with changes in soil C content. Specifically, we aimed to identify the development of surficial soil hydrophobicity and changes in soil water holding capacity. A long-term forest experiment with variable planting densities (816, 1111, and 2066 trees ha-1) of Eucalyptus grandis Hill ex Maiden and Pinus taeda L. was established in 2004 on native pasture vegetation. Undisturbed soil samples (0.00-0.03 m soil layer) were extracted from the experiment and surrounding pastures and soil water repellency was determined by the water drop penetration time (WDPT) method at three soil matric potential levels (SMP). Bootstrapping was used to test if the sample size was sufficient to obtain robust results. Replacing native pastures with forest plantations significantly increased surficial soil hydrophobicity, which was more pronounced under Eucalyptus grandis than under Pinus taeda. Soil water repellency increased with decreasing SMP, particularly in land-uses that generated higher initial hydrophobicity. Additionally, the soils under forest cover had less water retention capacity than those under pastures at each SMP, with larger differences when the soil was dried to more negative SMP. More research is necessary to determine if soil alterations from converting native pastures to forest plantations in temperate climates will lead to a significant decrease in soil water holding capacity and an increase in hydrophobicity at deeper depths.

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ABSTRACT Although Selenium (Se) plays a role as a micronutrient for humans through vegetable consumption, it is also recognized as toxic when present in excessive quantities. Therefore, quantifying Se contents in soils can prevent diseases influenced by crop Se deficiency or excess. We aimed to measure background contents, establish quality reference values (QRV) for Se in soils from two Brazilian biomes (Cerrado and Caatinga), and assess how geopedological factors affect Se content and spatial variability. Two hundred and eight composite topsoil samples were analyzed for Se content, covering an area of about 251,578 km². Sampling sites were under the minimal anthropogenic influence to represent Se background contents. Selenium contents were determined by hydride generation atomic absorption spectroscopy (HGAAS), ranging from 0.002 to 4.78 mg kg-1. Most soils had contents below the world average of 0.44 mg kg-1 but still above the soil content that causes human Se deficiency (0.125 mg kg-1). Soils from Cerrado and Caatinga biomes showed similar average contents of Se, 0.41 and 0.47 mg kg-1, respectively. Organic carbon content and soil particle size (clay fraction) were the main factors governing Se content in the soils. Our results contribute to understanding the Se content and spatial distribution in tropical soils and the factors governing them. They also provide a tool for agriculture and environmental decision-makers to plan public policies regarding the management of Se levels in these and similar tropical soils in the world.

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ABSTRACT Since the industrial revolution, human activities have emitted approximately 2,500 Gt of CO2, increasing the concentration of atmospheric CO2 by 50 % compared to pre-industrial levels. To better understand the potential for mitigating greenhouse gas (GHG) emissions through proper management of degraded pasture areas, we conducted a systematic literature review and identified 23 publications reporting carbon sequestration values for pastures managed under different conditions in the south and southeast regions of Brazil. From this dataset, 17 publications considered to be in line with the research premises were selected to estimate the potential for soil carbon sequestration (SEQ) through pasture recovery in the southern region of Brazil, using conservative and regenerative agricultural management practices. Results show that managed pastures can sustain carbon sequestration rates of around 2.50 Mg C ha-1 yr-1 over approximately 20 years. However, due to the numerous variables influencing SEQ rates, the limited number of publications, and the lack of data for some variables among them, a more extensive analysis of publications and data is needed to establish causal and preponderance relationships regarding the effect of each variable on the found SEQ rates. Under current pasture occupation conditions in Brazil’s south region, it is estimated these areas could sequester between 0.433 and 1.273 Gt CO2 at the end of 20 years if managed under appropriate practices. These numbers are not representative to reduce atmospheric CO2 concentration from legacy emissions and significantly mitigate physical impacts of climate change, reinforcing the importance of prioritizing the reduction of global GHG emissions as the primary mitigation strategy. On the other hand, from the perspective of mitigating the national agricultural sector’s annual GHG emissions, this potential cannot be considered negligible. Carbon sequestration by soils under agricultural management can play a vital role in mitigating climate change, integrating the set of necessary solutions and actions for a Paris Agreement goals compatible trajectory of limiting global warming to between 1.5 and 2 °C by the end of the century.

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ABSTRACT Identifying sediment sources is fundamental for protecting and improving soil and water quality. Conventional fingerprinting studies have often collected sediments at the overall watershed outlet only, resulting in an important spatial scale dependency. This study aimed to identify and to assess the delivery patterns of sediment sources within three priority sub-catchments (Sapocaji, Piedade and Minas) located in the downstream portion of the Ipojuca River watershed in Brazil. This research would build on understanding sediment sources in the studied watershed by elucidating source type contributions on a sub-catchment basis. Both bed and suspended sediment samples were collected in these sub-catchments, and two types of sources were sampled: surface and subsurface sources. A total of 21 geochemical tracers were measured. The tracers were evaluated for their conservation and discriminatory ability (Kruskal-Wallis test and linear discriminant analysis), and the best set of tracers was selected for source apportionment modeling using MixSIAR. Surface (i.e., sugarcane croplands) sources contributed the highest to suspended sediments in the Piedade and Minas sub-catchments. There was a difference in the quality of riverbank management, which helped explain contrasts in the importance of this source. Overall, sub-catchment-specific sediment control management measures, such as the revegetation of riparian forests, need to be implemented, mainly in the Sapocaji sub-catchment. These results underscore the importance of connectivity for surface source contributions.

Resumo em Inglês:

ABSTRACT Plantation forests can be efficient C sinks in biomass and soil organic carbon (SOC), but the latter depends on many factors, including climate. Tropical humid, mountain areas have cooler temperatures, slowing microbial decomposition, and thus can store considerable SOC. However, the effects of forest plantations on SOC of these montane areas are still poorly studied. Here, we aimed to assess changes in SOC, and related soil properties, after conversion of native rainforest to plantations of five tree species, with rotation cycles varying from 7 to 30 years, on the Mantiqueira Range, Minas Gerais, Brazil. We measured SOC contents and stocks (0.00-0.40 m layer) under a native montane rainforest (control) and plantations of Eucalyptus, Pinus, Cunninghamia, Cupressus and Araucaria, all planted in 3 × 3 m spacing, at an altitude of ca. 1,300 m, marked by humid and cool climate, where SOC contents are naturally high. Soil organic carbon varied from 55 g kg-1 under Eucalyptus to 105 g kg-1 under Araucaria (0.00-0.05 m layer), decreasing in depth (0.20-0.40 m) to the still high values of 20-40 g kg-1. Soil organic carbon stocks for the top 0.20 m were also high, reaching ca. 140 Mg ha-1 under Araucaria, significantly higher value than the native forest (ca. 90 Mg ha-1, p<0.05), which did not differ from the other species. Soil organic carbon stocks were not affected in the 0.20-0.40 m soil layer, whereas soil structure patterns changed under some species, without however resulting in bulk density changes, and pH decreased under Araucaria. Such data showed large SOC stocks under montane native forests can not only be preserved upon conversion to forest plantations, but considerable SOC sequestration can be achieved in 30-years rotation cycles plantations of indigenous Araucaria angustifolia, marked by more open canopies and greater understory biomass.

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ABSTRACT The “campos” of the Pampa are unique Brazilian ecosystems, which provide key environmental services, including C storage. These grassy ecosystems have been rapidly converted to intensive land-uses, mainly intensive grain crops (soybeans) and Eucalyptus silviculture. These new land-uses could decrease soil C stocks, depending on soil management. This study aimed to assess soil organic carbon (SOC) changes after the conversion of native grasslands to cropland (soybeans/cover crops under no-tillage) and forestry (Eucalyptus). Eight representative sites in this biome were selected for soil sampling (Alegrete-ALE, Aceguá-ACE, Jari-JAR, Jaguarão-JAG, Pinheiro Machado-PIM, Lavras-LAV, Santo Antônio das Missões-SAM, São Gabriel-SAG). Soil sampling was conducted in dug pits (0.30 m wide × 0.30 m long × 0.40 m depth) spaced by 50 m at each site, to 0.30 m depth. Soil bulk density and SOC were obtained by samples obtained with volumetric rings. Soil organic C was analyzed by dry combustion. Soil C stocks were calculated per layer and cumulatively (0.00-0.20 and 0.00-0.30 m). Soil C content was higher under grasslands in soils from sites with finer, clayey texture (ACE, JAG), and lower in soils at sites with sandier topsoil. Land-use conversion to silviculture and cropland minimally affected SOC stocks. The same pattern was observed with soil N, because of the tight connection between C and N cycles. Soil bulk density was similar across sites and layers, but higher values were measured in sites with coarser texture. Mean SOC stock of the grassland sites was 62 ± 24.6 Mg ha-1, similar to 66 Mg ha-1 reported for grasslands soils of Rio Grande do Sul State, and higher than that reported by IPCC for this region (55 ± 4.4 Mg ha-1). Adopting these default values would lead to underestimation of baseline SOC stocks in the region. Land-use conversion to cropland did not affect SOC stocks significantly, probably because of the adoption of no-tillage system with winter cover crops. Soil C stocks were lower in Eucalyptus stands in the 0.00-0.30 m soil layer, which could be attributed to intensive soil management at planting and lower soil fertility in some sites. This lack of effect of conversion on soil C was attributed to the short time since conversion and adoption of soil conservation practices (no-tillage) in cropland. The study contributed to reduce existing soil data gaps in the region and supports Brazilian public initiatives like the ABC Program and National Greenhouse Gas Inventories.

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ABSTRACT Most Brazilian municipalities do not have regulated areas for solid waste disposal in civil construction. Usually, residues are disposed of vacant lots and dumps, posing risks to the population health and the environment. Soils are the primary means for the disposal or recycling of waste, highlighting the importance of well-characterized soils and their respective landscape. This study aimed to establish a land suitability system for solid residues in civil construction and apply such information in a case study in Southeastern Brazil. An unprecedented digital soil map with a resolution of 30 m was created using the random forest classifier algorithm and soil field prospection information. A guide listing favorable soil-landscape attributes that most prevent soil erosion, water bodies or water table contamination was elaborated and discussed. Thus, such information was linked through a suitability system to classify areas with potential for receiving waste on a daily volume basis as follows: large size: >500 m³ day-1, medium size: >100 m³ day-1 and <300 m³ day-1, and small size <100 m³ day-1. Topography and soil depth were the most limiting factors of the areas in the case study. The proposed attributes as criteria for the suitability system complement the current state legislation. A total of 236 ha closer to the urban perimeter connected by roads in good condition were classified as suitable for managing medium- and small-scale daily volume, whose destination might reduce transportation and installation costs in the study area.

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ABSTRACT Land-use effectiveness can be ensured by utilizing GIS and geostatistical tools in conjunction with land assessment methods to prevent soil erosion and salinization. This study employs a GIS-based LESA methodology, combined with geostatistics, to evaluate the land’s capacity to produce agricultural crops on calcareous soils. Land Evaluation for Agricultural Uses (LESA) key components are site assessment and land evaluation, with the former being non-soil-dependent and the latter being soil-dependent. Geostatical kriging was used to interpolate and generalize a GIS map of land capability. The study found that 27.88, 47.94, 18.76, and 5.41 % of the study area were unsuitable for crop farming, marginally suitable, moderately suitable, and highly suitable, respectively. Our research demonstrates that a flexible GIS framework can assist decision-makers in more accurately assessing land resources, including unsuitable, marginally-suitable, and reforested lands.

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ABSTRACT Peach rootstock and scion cultivars are selected in breeding programs considering resistance to pests and diseases, salt tolerance, drought tolerance, and vigor. However, rootstock tolerance to aluminum (Al), which is markedly present in tropical and subtropical soils of the world, is not considered. Thus, it is essential to define potential markers that can contribute to the selection of Al-resistant or Al-tolerant peach rootstocks. The objective of this study was to identify Al-tolerant peach tree rootstock cultivars and clonal selections using physiological and oxidative stress variables. A completely randomized experimental design was used in a 13 (rootstock cultivars and clonal selections) × 2 (with and without Al) factorial arrangement, with three replications. Nursery peach trees of own-rooted ‘BRS Mandinho’ (without rootstock) and nursery trees of ‘BRS Mandinho’ grafted on different rootstock cultivars and clonal selections were grown in a hydroponic system, consisting of two treatments, with and without 100 mg L-1 of Al. Dry biomass, photosynthetic variables, pigment concentration, hydrogen peroxide content, membrane lipid peroxidation, and activity of the antioxidant enzymes were evaluated. The total dry matter production of the own-rooted ‘BRS Mandinho’ trees and the SS-CHI-09-39 and SS-CHI-09-40 selections is affected by the Al presence, representing a decline of 35.4, 37.2, and 24.4 %, respectively, compared to the treatment with Al. The highest total dry matter production in Al presence was observed for the ‘Sharpe’ rootstock. ‘Capdeboscq’, DB-SEN-09-23, FB-ESM-09-43, JB-ESM-09-13, JAH-MAC-09-77, SAS-SAU-09-71, and VEH-GRA-09-55 rootstock selections are tolerant to Al. The use of physiological and biochemical variables shows potential for the selection of clonal rootstocks tolerant or resistant to Al.

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ABSTRACT Tropical forests have the highest rates of net primary productivity (NPP) in terrestrial ecosystems and, therefore, may contribute significantly to the mitigation of global climate change. Although NPP is influenced by soil fertility, and recently, in some regions, mining activity in forest ecosystems has intensified. Little is known about how soils determine the restoration of NPP in forests degraded by mining. We evaluated the influence of soil nutrients on wood NPP of post-mining forests in the biogeographic Chocó region (Colombia), with emphasis on the effects of nitrogen (N) and phosphorus (P) limitations in post-mining forests under successional stages of 12-15 or 30-35 years. For this, permanent plots were established in secondary post-mining forests in Jigualito (Colombian Pacific), the wood NPP (accumulated and current) was evaluated, and it was related to soil properties such as organic matter (OM), acidity, Al, total N, available P, magnesium (Mg), potassium (K), calcium (Ca), and texture. An accumulated wood NPP of 0.72 t ha-1 yr-1 was recorded in post-mining forests 12-15 years old. Meanwhile, in post-mining forests of 30-35 years, the accumulated wood NPP was 6.52 t ha-1 yr-1. The current wood NPP was 4.25 t ha-1 yr-1 in post-mining forests with 30-35 years of recovery. Accumulated NPP positively correlated with soil OM, total N, Ca, Mg, and effective cation exchange capacity–ECEC in post-mining forests. In post-mining forests, a slow recovery of the wood NPP was denoted in the first years. Soil nutrients determined the wood NPP, and a multiple limitation of nutrients with the succession was observed, which corroborates the need to restore the degraded ecosystem in the region.

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ABSTRACT Soil education plays an important role in preventing soil degradation processes by raising awareness among the population about the importance of this non-renewable resource. Using new educational technologies in teaching, such as educational videos and social media, can speed up communication and information. This article aimed to develop educational videos on the topic of erosion, posted on social networks, as a way of popularizing science. Four videos of a maximum of 7 minutes were produced, which were shown in the classroom and on Instagram (@saberessobresolos). In-class promotion reached nine undergraduate and postgraduate classes, totaling an average of 255 students. Metrics used for evaluation were polls and video engagement on the social network. Instagram metrics results indicated, in a period of 49 days, 1615 profiles had accessed the video. There was a reduction in this engagement in other publications, probably due to the variation in time, day of the week, and frequency of posts. The results of the surveys were positive for all the characteristics evaluated, with little disparity among the videos. On a smaller scale, negative feedback was observed, such as: the narration, running time, the translation into Brazilian Sign Language (Libras), and video captions. Approximately 81 % of individuals reported experiencing soil erosion effects, and 59 % had encountered issues as a direct consequence. The evaluation also indicated the videos’ ability to enhance knowledge is above 90 %, largely due to the dynamic and inclusive nature of this pedagogical approach, fostering genuine comprehension of the content, satisfaction in learning, and the ability to engage in meaningful discussions on the subject. Disseminating educational videos through social media ensured the democratization and widespread access to soil education, as it expanded reach and facilitated the exchange of knowledge between universities and society. The project fulfills its mission of producing and popularizing knowledge on soils, expanding scientific dissemination, making it more accessible, and contributing to recognizing the importance of conserving this resource.

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ABSTRACT The term toposequence, proposed to designate a lateral succession of soils on a slope due to the influence of topography, began to be used differently over time, distancing itself from its original concept. Here, we discuss how this concept has been used since its inception. We carried out bibliometric analyses of publications in the database available on the Web of Science since 1900. Three main approaches and related concepts, explicit or not, one at a regional scale and two others at a local scale were identified. From this analysis, we suggest: a) when the approach is regional, the term geomorphic surface or position in the landscape should be used to address the spatial distribution and genetic implications of soils at this scale; b) when dealing with series/sequences of soils on slopes for mapping purposes or discontinuous profiles that emphasize taxonomic classification, the term catena should be used; c) when the determining factor of the soil sequence is climatic, biotic, lithological, chronological, the corresponding term climo-, bio-, litho- or chronosequence should be used; d) when dealing with a lateral succession of horizons in the continuum on slopes, resulting from the influence of topography on soil formation, which may reflect the soil contribution to the model evolution, only in this case should the term toposequence be used, returning to its original concept.