Repositório RCAAP

ABSTRACT Soils with andic properties are characterized by a low apparent density, variable charges, large amounts of allophanes, imogolite, ferrihydrite, and/or organo-metallic complexes with Al, and present high phosphate retention. Soils derived from non-pyroclastic materials rich in silicates, formed under a cold and humid climate, a large amount of organic carbon, acid weathering, andic properties can manifest when a large amount of Al is present in the form of organo-metallic complexes. This study aimed to evaluate the characteristics and geographical expression of soils with such properties in areas of altitude in the extreme south of Brazil, on the escarpment edges of the Serra Geral Formation, under a cold and humid climate. The sampling points were selected based on environmental characteristics such as geomorphology, geology, the coloration of the superficial horizon of the soil, and position in the landscape, covering a linear distance of approximately 185 km at the escarpment edge between the states of Santa Catarina and Rio Grande do Sul. Soil samples were described and collected from ten soils with histic horizon O, three soils with humic horizon, and one soil with histic horizon H. The undisturbed soil samples were collected using volumetric metallic cylinder to determine the soil bulk density. Organic matter, pH(H2O), P retention, and selective dissolutions of Al, Fe, and Si analyses were performed. The Cambissolos Hísticos and Organossolos Fólicos showed andic properties, while the Cambissolos Húmicos and Organossolo Háplico did not meet one or more criteria, as required by the Brazilian Soil Classification System and the World Reference Base for Soil Resources. The horizons with andic properties were classified as aluandic, based on the predominance of Al associated with organic complexes. The cold climate and high cloudiness of the highest altitude areas in the extreme south of Brazil, occurring in a narrow strip of the escarpment of the Serra Geral Formation in the states of Santa Catarina and Rio Grande do Sul, allow the formation of a constantly humid environment. This environment favors the acid weathering of the source material, accumulation of organic matter in the soil, and its stabilization by the formation of organo-metallic complexes, mainly Al-humus. The combination of these factors gives the soils with histic horizons O a low bulk density, high phosphate retention, and Alo + ½Feo ≥2 % values, meeting the criteria required for andic properties.

ABSTRACT Throughout the Amazon region, dark-colored soils with increased fertility are identified and referred as Amazonian Dark Earths (ADE). These unique soils are characterized by an anthropic surface horizon with dark colors, presence of charcoal and artifacts, in contrast with surrounding non-ADE soils. The ADEs show extraordinary properties such as the capacity of maintaining the dark colors and high nutrient levels after years of farming, even under the highly favorable climatic conditions for oxidation of organic matter and weathering of nutrients of Amazon region. The ADE are considered islands of fertility in the Amazon biome, as well as very important models for research, in terms of agricultural and environmental sustainability, carbon sequestration, nutrient bioavailability, food security, and for anthropological studies. However, there are many unanswered questions regarding the extent of human alterations, how they were formed, and their classification in the taxonomic systems. Therefore, the objectives of this study were to identify, describe, and characterize soil profiles of ADEs, located in the Southern region of Rondônia State, Brazil, and to contribute to their classification according to the Brazilian Soil Classification System (SiBCS) and the World Reference Base (WRB). Five soil profiles were described and sampled; P1 to P3 were under grass pastures, P4 and P5 under forest and crops with no-till, respectively. The morphological, physical, and chemical attributes, as well as contents of Fe, Al, Si, and Ti oxides and extractable iron forms were characterized. The anthropic horizons exhibited dark colors, artifacts, charcoal, sandier textures, predominantly granular structures, abrupt or clear transitions, and mostly wavy and irregular boundaries. Values of pH, Ca 2+ , Mg 2+ , exchangeable bases (S), CEC, and C were high in all anthropic horizons. Compared to non-ADE soils in the Amazon region, phosphorus contents were superior in all anthropic horizons, with the highest values in surface horizons of P1, P2, and P3. According to SiBCS, P1 was classified as Cambissolo, P2 as Argissolo , and P3, P4, and P5 as Latossolos. Except for P4, where values of extractable P by Mehlich-1 are lower than 30 mg kg -1 , all soils fulfilled the requirements for the anthropic horizon in the SiBCS, and new classes at the subgroup level were proposed. In the WRB, P4 and P5 were classified as Ferralsols. The other profiles were classified as Anthrosols. The radiocarbon dates (C 14 ) of charcoal fragments, obtained using a mass accelerator, showed ages between 940 ± 40 and 1230 ± 60 years BP.

ABSTRACT Soil properties and classes can influence the occurrence of plants and the production of Brazil nut fruits and may have a different distribution between sites. This study aimed to evaluate the relationship of plants’ occurrence, production of Brazil nut fruits, and spatial variability of the properties in different soil classes in two Brazil nut stand in the state of Acre, Brazil. The study was conducted in two plots in two native Brazil nut stand, Cachoeira (CP01 and CP02 - plots 1 and 2) and Filipinas (FP01 and FP02 - plots 1 and 2). The soil profiles were described morphologically. Sixty soil samples were collected in each plot. The chemical properties, granulometry, soil density, particle density, and estimated total porosity were determined. The average fruit production was calculated by counting the fruits in a sample of Brazil nut trees. Subsequently, the trees were divided into three classes of production: low (≤1.5 can; the can unit has 18-L, which is able to hold 59 and 77 fruits, respectively, for Cachoeira and Filipinas), medium (1.6 to 3.9 cans), and high (≥4.0 cans). The can unit is the traditional measure of volume in the region and varies according to the locality. Cluster analysis was performed to determine whether there was a difference between Brazil nut stands and soil profiles, and geostatistics was used to evaluate the spatial dependence of soil properties. The highest occurrence of Brazil nut trees with high fruit production (≥4.0 cans) was found in the Latossolo Vermelho Distrófico argissólico (Oxisol) and Argissolo Vermelho-Amarelo Distrófico típico (Ultisol). However, the Argisol also hosted the plants with the lowest productions (≤1.5 can). The pH, total organic carbon, sum of bases, P, N, granulometry, and porosity showed a greater spatial variability, and FP02 showed a greater number of properties with high spatial variability compared to the other areas. Although the occurrence of plants and the production of Brazil nut fruits ( Bertholletia excelsa ) were associated with the classes and the physical and chemical properties of the soil, pyxidium production differed between areas. In general, soil physical properties were limiting factors for Brazil nut production and/or higher tree occurrence. Filipinas environment showed a low fruit production and a greater spatial variability of soil properties compared to Cachoeira.

ABSTRACT Soil invertebrate fauna plays a major role in several environmental processes, and its absence can negatively impact ecosystem health. This study aimed to assess the recovery of epigeal and edaphic invertebrate faunal communities following an environmental disaster, with landslides, mudflow, and river floods, in sites under different management systems, the effects of cover crops on invertebrate fauna, and their relationship with soil physical and chemical properties in the mountainous region of Rio de Janeiro State, Brazil. The following sites were evaluated: CF, a site under conventional farming without any record of natural hazard events; LS, a site impacted by an intense landslide event that left the area buried by mudflow; RO1, a site affected by river overflow and treated with NPK fertilizer and poultry litter; RO2, a site affected by river overflow and subjected to liming and heavy fertilization with NPK; and RO3, a site affected by a less intense river overflow and subjected to fertilization with poultry litter and NPK fertilizer. At each site, epigeal and edaphic fauna were sampled using pitfall traps and a monolith sampler, respectively. Physical (soil temperature, moisture, aggregate stability, and density) and chemical (pH in water, Ca2+, Mg2+, Al3+, K+, P, cation-exchange capacity, and total organic carbon) properties were determined in the 0.00-0.05 and 0.00-0.10 m layers. The predominant epigeal faunal groups were Entomobryomorpha, Poduromorpha, Diptera, and Coleoptera; and the predominant edaphic faunal groups, Coleoptera and Oligochaeta. There was a positive correlation between Coleoptera larvae, Hymenoptera, and species richness with total organic carbon. Coleoptera larvae were positively associated with biogenic aggregate stability, whereas Coleoptera was positively associated with physicogenic aggregate stability. Oligochaeta showed a positive correlation with soil moisture. Cover crops favored the development of epigeal and edaphic faunal groups that enhance soil properties through organic matter fragmentation and decomposition, and structural engineering. The strong correlation between soil chemical, physical, and biological properties demonstrate the importance of monitoring these components to assess the recovery of disaster-affected areas.

ABSTRACT Soils in the Depressão Central and Campanha Gaúcha in Rio Grande do Sul State, Brazil, developed from sedimentary rocks are mainly Alfisols (Luvissolos, Planossolos and Plintossolos) and Ultisols (Argissolos) with high textural contrast between A and/or E horizons and clayey B horizons. Red Ultisols dominate in well-drained areas in the summit. But many soils present redoximorphic features on the backslope and footslope, with mottled and/or nodules similar to plinthite due to the oscillating of the water table above the rock or poorly permeable saprolite. Identifying morphological features, mineralogical and chemical properties, and parent material differences are essential to identify the main processes responsible for their genesis. Knowledge of the relative distribution of different forms of iron in the soil is also of particular interest when interpreting pedogenesis. This study aimed to evaluated the main process responsible for the high textural contrast in soils developed from different sedimentary lithologies, and how the redoximorphic features observed in some soils may be related to genesis of plinthites and ferrolysis processes. The study area is located in the hydrographic basin of Rio Santa Maria, in the city of Rosário do Sul – RS, Brazil (30° 15’ 28” S and 54° 54’ 50” W), average altitude of 132 m and Cfa-type climate. Topolithosequences were defined based on soils developed from lithogies of Piramboia and Sanga-do-Cabral geological formations, by choosing soil profiles according to the source material, variations in relief, altitude and hydrological conditions. Morphological descriptions, particle size determinations, chemical analysis, mineralogy of the clay fraction by XRD analysis, determination of the main forms of iron, tests to identify plinthite were performed. Argiluviation, ferrolysis and plinthization were the most active processes identified in the genesis of most studied soils. The high textural contrast on these soils was not solely due to clay illuviation processes but also ferrolysis and lithological discontinuities in some soils, indicating polygenetic origin. Redoximorphic features in most soil revealed that iron segregation in most soils occurs like mottles and not plinthite, since they did not remain aggregated after the various wetting and drying cycles.

ABSTRACT The concept of attitude toward soil is emerging, with a slim choice of scales available to collect hard data. There is also a dearth of standard scales to acquire precise data on students’ knowledge of soil. Therefore, the objectives of the present study were: (1) to devise appropriate scales to quantify theoretical soil knowledge and attitude toward soil, and (2) to quantify the effect of laboratory studies and fieldwork on students’ theoretical soil knowledge and attitude toward soil. The study is based on data collected from undergraduate students of the introductory soil science course. Participating students were randomly divided into two groups. Teaching of the control group (n = 38) was classroom-based, while teaching of the intervention group (n = 43) was complemented with laboratory studies and fieldwork. Our test design included a pre-test and post-test. It appears that theoretical soil knowledge and students’ attitude toward soil can be improved using classroom-based education alone, without any need for laboratory or field components. However, future studies would be needed to develop questionnaires covering hands-on soil knowledge to better gauge the impact of lab work and field classes on student learning. The present study is an important step to elaborate reliable scales suitable for quantifying students’ knowledge and attitude toward the soil. It is impossible to test academic assumptions or create theoretical foundations for soil science education without a reliable device to weigh analytical concepts.

ABSTRACT Multitemporal collections of satellite images and their products have recently been explored in digital soil mapping. This study aimed to produce a bare soil image (BSI) for the São Paulo State (Brazil) to perform a pedometric analysis for different geographical levels. First, we assessed the potential of the BSI for predicting the surface (0.00-0.20 m) and subsurface (0.80-1.00 m) clay, iron oxides (Fe 2 O 3 ), aluminum (m%) and bases saturation (V%) contents at the state level, which are important properties for soil classification. In this task, legacy soil samples, the BSI and terrain attributes were employed in machine learning. In a second moment, we evaluated the capacity of the BSI for clustering the landscape at the regional level, comparing the predicted patterns with a legacy semi-detailed soil map from a smaller reference site. In the final stage, the predicted soil maps from the state level were investigated at the farm level considering several sites distributed across the São Paulo state. Our results demonstrated that clay and Fe 2 O 3 reached the best prediction performance for both depths at the state level, reaching a RMSE of less than 10 %, RPIQ higher than 1.6 and R 2 of at least 0.41. Additionally, the predicted landscape clusters had a significant association with the main pedological classes, subsurface color, soil mineralogy and texture from the legacy semi-detailed soil map. Illustrative examples at the farm level indicated great capacity of BSI in detecting the variations of soils, which were linked to several soil properties, such as texture, iron content, drainage network, among others. Therefore, this study demonstrates that BSI is valuable information derived from optical Earth Observation data that can contribute to the future of soil survey and mapping in Brazil (PronaSolos).

ABSTRACT Soil maps provide a method for graphically communicating what is known about the spatial distribution of soil properties in nature. We proposed an optimized pipeline, named dino-soil toolbox, programmed in the R software for mapping quantitative and categorical properties of legacy soil data. The pipeline, composed of four main modules (data preprocessing, covariates selection, exploratory data analysis and modeling), was tested across a study area of 14,537 km 2 located between the departments of Cesar and Magdalena, Colombia. We assessed the feasibility of the toolbox to model three soil properties: pH at two depth intervals (0.00-0.30 and 0.30-1.00 m), soil taxonomy (great group) and taxonomic family by particle-size, according to a set of 25 environmental factors derived from auxiliary layers of climate, land cover and terrain. As a result, we successfully deployed the proposed semi-automatic and sequential pipeline, yielding rapid digital soil mapping (DSM) outputs across the study area. By providing multiple outputs such as tables, charts, maps, and geospatial data in four main modules, the pipeline offers considerable robustness to support outcomes and analysis of a DSM project. Future studies might be interesting to expand on further machine learning frameworks for predictive modeling of soil properties such as ensembles and deep learning models, which have shown a high performance for DSM.

ABSTRACT Evidence of arbuscular mycorrhizal fungal colonization of mat litter in various ecosystems plus previous reports of external mycelium of those fungi and mycorrhizal roots in litter from coffee plants and shade trees on coffee plantations suggest that they have a relationship with closed direct nutrient cycling between organic matter and living roots. This relationship was first proposed more than 50 years ago. Mycorrhizal symbiosis in tropical crops is affected by agricultural management practices. This study aimed to assess the occurrence of arbuscular mycorrhizal fungi in leaf litter from three shaded Colombian coffee agroecosystems under organic and conventional management. One is managed chemically, one organically, and one with a combined use of organic and chemical inputs. Leaf litter and roots were collected from the three coffee plots at three decomposition stages. Each plot represented a distinct fertilization and tree dominance pattern different from the other two plots. Arbuscular mycorrhizal fungi were found in decomposing leaves. The chemically managed plot showed statistical differences (p<0.05) with respect to the other plots, it had the greatest amounts of arbuscular mycorrhizal fungal root colonization (48.76–70.51 %), litter colonization (36.2–69.91 %), external mycelium length (28.66–48.33 m g-1), and spore number (451.27–681.2 spores in 20 g of dry soil). In contrast, conditions on the combined management coffee plot results in smaller means of the variables evaluated. Arbuscular mycorrhizal fungal root colonization and nitrogen content of leaf litter varied among the decomposition stages (p<0.05). Litter quality of different tree species may have influenced colonization of plant matter within each plot. We found evidence of typical structures of arbuscular mycorrhizal fungi within and among decomposing leaf litter and roots growing into the mat litter in tropical agroecosystems. This supports the thought that these fungi have a role in carbon and nutrient recycling, which are influenced by agricultural management practices and plant population composition.

ABSTRACT For decades, researchers around the world search for strategies aiming at higher sustainability in agriculture. The microbial inoculants or biofertilizers are biotechnological products used for different purposes, the main one being to totally or partially replace chemical fertilizers, with an emphasis on N-fertilizers, reducing costs of production and decreasing the contamination of the soil, water, and atmosphere. Depending on the microorganism and the inoculated crop, inoculants can also induce plant protection to abiotic and biotic stresses and positively modify their physiology. Although inoculation studies and the use of inoculants by farmers date more than a century ago, they have gained more notoriety in the past decade. Brazil has a long tradition in the use of rhizobial inoculants, especially for the soybean crop, but it was only in 2009 that the first commercial inoculant carrying the plant-growth-promoting Azospirillum brasilense strains Ab-V5 (=CNPSo 2083) and Ab-V6 (=CNPSo 2084), identified by our research group, reached the market. One decade after the release of these two strains, 10.5 million doses were commercialized for grasses, including corn, wheat, rice, and pastures of brachiarias, and co-inoculation of legumes, such as soybean and common bean. Several research groups in Brazil presented impressive results of increases in root growth, biomass production, grain yield, uptake of nutrients and water, and increased tolerance to abiotic stresses due to the inoculation with Ab-V5 and Ab-V6. In this review, we gathered the results obtained so far in one decade with these two strains in several grasses and legume crops, confirming their versatility and indicating that with convincing, reliable, and consistent results, the Brazilian farmers are receptive to the adoption of new sustainable technologies based on microorganisms.

ABSTRACT The relation between water content and water potential is a key soil hydraulic property. The presence of rock fragments in soils can affect this property in bulk soil. In this study, we focused on the relation property determined with a WP4 dew point potentiometer. The objective was to evaluate the hypothesis that breaking large gravel-size particles into smaller fragments is a suitable strategy for accurate WP4 measurements in coarse materials without affecting the retention properties. Ten initial samples of basalt rock fragments with different weathering degrees were collected from the A horizon of an Entisol (Neossolo). Rock fragments initially sized between 38 to 4 mm were successively fractured into smaller fragments (size classes of 4-2, 1-0.25, and <0.25 mm). For each size class, the retention properties (water content versus water potential) were determined with WP4 equipment. No significant effect of fragment size was detected on the determined retention properties. Using supplementary water retention data from a previous study, we found an overestimation of water retention at -1.5 MPa ranging from 0.08 to 0.12 g g-1 when rock fragments were removed, which is of the order of magnitude to the available water capacity of several soils. This study showed that fragments larger than the diameter of the WP4 sample cup could be broken to sizes smaller between 4 and 0.25 mm without affecting the retention properties. This is a suitable strategy to allow accurate WP4 measurements in coarse materials while considering the effect of such coarse material on retention properties.

ABSTRACT The combination of pillarization and charge neutralization with Li+ can make montmorillonite an important support material for industry and decontamination of pollutants in soil and water. Montmorillonite characterization techniques were described in detail, and pillarization procedures were used, after Li+ saturation, to modify and manipulate the chemical and mineralogical surface properties of this montmorillonite. Eight samples were produced: 1) natural montmorillonite (Chisholm Mine - MMT); 2) Li+ saturated montmorillonite (MMTLi); 3) polyethylene glycol (PEG) Al-pillared montmorillonite (AlPEG); 4) PEG Al-pillared montmorillonite saturated with Li (AlPEGLi); 5) Al-pillared montmorillonite with 14 h contact time (Al14h); 6) Al-pillared montmorillonite Al14h saturated with Li (Al14hLi); 7) Al-pillared montmorillonite with 0 h contact time (Al0h); and 8) Al-pillared montmorillonite Al0h saturated with Li (Al0hLi). The natural sample was identified as interlayered montmorillonite composed of chlorite layers or with a high degree of Al-hydroxy filling. Concerning the total permanent charges, 70 % occurred by isomorphic substitution of Al3+ by Mg2+ in octahedral layer and 30 % of Si4+ by Al3+ in tetrahedral layer. The pillarization method using the PEG produced a small number of stable pillars. The new milder pillarization method (Al0h) did not cause damage in the formation of Al-hydroxy. In this method, the resulting pillars were more homogeneous in size. Thereby, the Al0h Li method has been shown to produce a supporting material with a constant interlayer spacing, increased of the specific surface area (SSA), and drastic reduction of the cation exchange capacity (CEC) as compared to MMT. This modified mineral can be used in, for example, decontamination of polluted water with nonionic organic pollutants.

ABSTRACT The steady infiltration rate of soil profiles is commonly determined for irrigation and soil conservation planning, but the divergence of methods reduces the reliability of measurements. In this study, the steady infiltration rate measured with a double ring infiltrometer (isr-dri) in different layers of a soil profile was compared between layers and with the steady vertical saturated flow rate estimated by the Richards equation (isr-hy). The measurements of isr-dri at the top of the A, E, and Bt horizons were compared to each other and also compared with the isr-hy to detect the occurrence of lateral flow in double ring infiltrometer measurements. The isr-dri in the A horizon (236 mm h-1) was around 10 times higher than in the Bt horizon (20 mm h-1), which implies in a lateral flow of almost 90 % in the surface horizon. The occurrence of lateral flow in double ring infiltrometer measurements was also shown by comparing isr-dri with the vertical saturated flow rate estimated with the Richards equation, isr-hy. The main conclusion is that isr-dri measured at the soil surface overestimates the steady infiltration rate of soil profiles when underlying horizons are less permeable and more restrictive to water flow. In these cases, the use of an effective saturated hydraulic conductivity of the soil profile would imply inaccurate planning of drainage, irrigation, and soil conservation designs.

ABSTRACT Film mulching is an effective water-saving and yield-increasing measure for potato production in Northwest China. However, the response mechanism of microbial communities to mulching films in the soil is still unclear. In this study, polyethylene film mulching (PM), biodegradable film mulching (BM), liquid film mulching (LM), and non-mulching (NM) were applied on the drip-irrigated soil to investigate the effects of mulching films on soil bacterial and fungal communities through DNA sequencing, Pearson correlation analysis, and redundancy analysis. The results showed that LM treatment significantly increased the contents of soil mineral N (SMN), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) (p<0.05) in comparison with NM. The soil treated with LM presented high bacterial OTUs (operational taxonomic units), Chao1, ACE, and Shannon indices; however, the same indexes of fungi were low in LM and BM treatments. At the phylum level, Proteobacteria, Actinobacteria, and Chloroflexi were dominant bacterial communities. The LM treatment increased the OTUs of Proteobacteria ; PM treatment increased the OTUs of Actinobacteria and Chloroflexi. Ascomycota was the dominant fungal community, which were decreased in soil under mulching films. In terms of soil properties, DON was closely correlated (p<0.05) with the microbial OTUs, Chao1, and ACE indices. The DOC and SWC (soil water content) contributed 51.2 % to the change of bacterial structure; however, the fungal structure was less sensitive to the variation of soil properties. Our results indicate that liquid film mulching favors increasing the diversity and abundance of dominant bacterial species, which were associated with the variation of soil properties.

ABSTRACT Restoration of degraded sites by using native plants like Plathymenia reticulata Benth. and Melanoxylon brauna Schot. is advisable. However, seedlings of both species, when raised on commercial substrates, may present low survival. This study aimed to evaluate the growth of seedlings under inoculation with arbuscular mycorrhizal fungi (AMF). The seedlings were raised on soil sampled from near an adult plant of the same species. The P. reticulata and M. brauna seedlings were grown with or without the inoculation of a mix of three species of AMF (Rhizophagus clarus, Claroideoglomus etunicatum, and Gigaspora albida), and five doses of P (0, 50, 150, 300, and 450 mg dm-3 of P). All seedlings were inoculated with Bradyrhizobium sp., isolated from each species. After 90 days, P. reticulata inoculated with AMF showed higher growth and nutrient content than those uninoculated, and the maximum plant growth was obtained when received 160 to 280 mg dm-3 of P. On the other hand, no effects of AMF inoculation or phosphate fertilization were observed on M. brauna. For both species, no effect of inoculation was observed on mycorrhizal colonization, and M. brauna, unlike P. reticulata presented a considerable number of nodules. We conclude that inoculation with AMF and P fertilization improves the growth of P. reticulata seedlings but does not promote the growth of M. brauna; presenting the necessity to investigate each species.

ABSTRACT Several management practices can increase soil water storage capacity, but their effectiveness to minimize the adverse effects of drought depends on their potential to increase the soil available water to plants. Terracing is an effective option to increase soil water storage, but its effect on available water to plants in no-tillage system is still a knowledge gap. In this study, we monitored soil water content at eight layers down to 1.6 m in two zero-order paired catchments for 16 months. Presence of five broad-based terraces in one of the catchments was the main difference between the two. Water availability to plants over time was expressed as a fraction of available water capacity (FAW). Positive differences of FAW between the terraced and non-terraced catchments were noticed over periods of rainfall shortage, but they were barely perceptible in periods of abundant rainfall. Over the 16 months, the frequency of FAW higher than 0.75 was between 46 and 50 % in the non-terraced catchment, and between 67 and 75 % in the terraced catchment. This benefit of terracing is more noticeable in thicker upper-section of the soil profile evaluated and with greater number of terraces upstream from the point of observation. We concluded that terracing in no-tillage turn excess rainfall into noticeable positive increases in available water to plants in the following periods of rainfall shortage.

ABSTRACT Finding the proper shaking setting to ensure total particle dispersion without altering the content of sand, silt and clay in soils composed of fragile particles such as saprolite fragments is still a research gap. This study aimed to identify the best shaking setting to optimize particle dispersion and minimize particle change in samples of Entisol (Neossolos). Samples were dispersed using an electric mixer at 12,000 rpm for 5, 15, 30 and 60 min, a horizontal shaker at 150 cycles min-1 for 1, 2, 4, 8 and 16 h with and without the use of nylon spheres, and an ultrasonic shaker at 70 and 110 J mL-1 for approximately 20 and 30 min, respectively. All the treatments affected particle distribution. Coarse sand reduced up to 14 % and clay content increased up to 18 % with the horizontal shaker with nylon spheres and the electric mixer. These changes were attributed to the breakdown of saprolite fragments, which represented around 1/3 of the coarse sand. Our results showed that the best setting was the horizontal shaker at 150 cycles min-1 for 1 to 2 h without using nylon spheres. This option allowed optimizing particle dispersion and minimizing changes in particle size distribution.

ABSTRACT This review presents the basic research and some applications of the gamma-ray attenuation, neutron gauges, and 137Cs fallout techniques for studying soil physical processes and properties. The selected studies aimed to give the readers a general idea of the use of these nuclear techniques carried out by Brazilian researchers in the past decades. It is expected to assist future researchers by identifying knowledge gaps and opportunities for applying the methods presented here. Around 100 studies were selected for this review. The papers dealing with gamma-ray attenuation are mostly related to the analysis of soil radiation interactions, the measurement of basic soil physical properties, the evaluation of hydraulic conductivity, water retention curve, and soil mechanical analysis. Neutron gauge applications are related to monitoring the water distribution and balance at the field scale, procedures for calibrating the existing gauge for the Brazilian soils, and analyzing the spatial and temporal variability of the soil water content. The 137Cs methodology involves studies about the erosion and sediment deposition in small watersheds and riparian zones, the spatial variability of 137Cs inventories at reference sites, and the measurement of sediment spatial distributions. Future studies with the gamma-ray attenuation methodology should focus on a better comprehension of the photon interaction with the soil and a correct selection of photon energies to investigate contrasting soils. This is mandatory for adopting it as a reliable tool for soil characterization. This review also revealed that the challenges for the future use of the 137Cs fallout technique involve the continuous decrease of the 137Cs activity worldwide, including in Brazil. Advances in detection systems (gamma spectrometers) will be required to overcome this issue. Future studies should focus on the use of correction factors related to the enrichment of fine particles during the transport of sediments to improve the estimates obtained through the conversion models. The use of neutron gauges to detect soil water content at the field scale depends on the adoption of reliable calibration curves. Then, comprehending how soil properties alter this curve and how it affects the water balance is a study of great interest. Motivated by strict regulations on the use of radioactive materials, the adoption of gauges with less activity is becoming a new goal. Thus, the development of more effective systems of neutron detection is crucial.

We report a case in which the Amplatzer device for percutaneous occlusion of ductus arteriosus was successfully used for occluding a large systemic-pulmonary collateral vessel in a patient who had previously undergone surgery for correction of pulmonary atresia and ventricular septal defect (Rastelli technique), and was awaiting the change of a cardiac tube. In the first attempt, the device embolized to the distal pulmonary bed and, after being rescued with a Bitome, it was appropriately repositioned with no complications and with total occlusion of the vessel.

No summary/description provided