Resumo em Inglês:

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 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 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.

Resumo em Inglês:

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.

Resumo em Inglês:

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 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.

Resumo em Inglês:

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.

Resumo em Inglês:

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.

Resumo em Inglês:

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.

Resumo em Inglês:

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.

Resumo em Inglês:

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 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.

Resumo em Inglês:

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.