Resumo em Inglês:

ABSTRACT Soil maps are important to evaluate soil functions and support decision-making process, particularly for soil properties such as pH, carbon content (C), and cation exchange capacity (CEC), but the spatial resolution and soil depth should meet the needs of users. On another hand, the efficiency of statistical models to create soil maps, with an acceptable level of accuracy, often require a large number of samples with an appropriate distribution across the area of interest. However, accessibility for sampling can be a trouble in remote areas, such as the Itatiaia National Park (INP). The hypothesis of this work is that it is possible to obtain a viable result in soil mapping of areas with limited access by using DSM tools. The general objective of this paper was to create 2- and 3-D maps of the soil properties pH, carbon content, and CEC, with the correspondent spatial uncertainty, in the INP plateau. The sampling strategy was designed using conditioned Latin Hypercube Sample (cLHS), and different methods were tested to produce the soil properties maps. For calibration of the models: linear (MLR, multiple linear regression) and nonlinear (GAM, Generalised Additive Models). The results showed differences in predictive performance for all statistical methods and covariate selection approaches. The GAM, with covariates selection based on soil formation factors, was the best method for the limited number of soil samples. The greatest uncertainty was associated with areas with the lowest accessibility and, consequently, with low sampling density and/or noises in covariates. Even though the 2- and 3-D maps of soil properties, each associated with explicit uncertainty, can contribute to the INP decision makers/managers by providing information not available before.

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ABSTRACT The pedological studies carried out so far in Trindade Island (TI) have obtained patchy evidences of allophane, without detailed mineralogical and micromorphological studies to confirm the occurrence of Andosols in TI. Therefore, in this study, the mineralogical, micromorphological, physical and chemical characterization of four soil profiles from Vulcão do Paredão (P1) and Morro Vermelho formations (P2, P3, and P4) were carried on the latest volcanic events in Brazil from Trindade Island (TI) with the aim of to evaluate the presence of Andosols in this oceanic island. Profiles P1 and P2 are developed on pyroclastic bombs, and show, respectively, A-Bi- C and decapitated A-C horizons, whereas P3 and P4 are developed on lapillitic and bomb pyroclasts, show A-C horizons. The soil profiles have a reddish and brownish clayey matrix, are highly friable and show a plastic consistency. Their microstructures are granular, single grain and intergrain microaggregate, in which aggregates display an undifferentiated b-fabric. The mineralogical constituents of the bulk fraction are biotite, hematite, magnetite, ilmenite, pyroxene, olivine, halloysite, goethite, anatase, and rutile. The clay fraction is marked by the presence of halloysite, ferrihydrite, and little amounts of allophane. All soils presented andic properties and can be classified as non-allophanic Andosols. In addition, micromorphological features closely resemble those reported in Andosols from other volcanic islands from elsewhere. The predominance of halloysite in the clay fraction formed by alteration of sideromelane, suggests that allophane would be an intermediate phase of this rapid transformation favored by the wet climate conditions of the highest parts of TI.

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ABSTRACT Notwithstanding the importance of soil surveys, advances in digital soil mapping have mainly focused on mapping soil attributes or properties rather than developing digital maps of soil units or soil classes. The purpose of this research was to develop digital soil unit maps based on primary soil data collection in areas without previously collected soil information. The covariate variability, the random effect across the data subset and the map outputs were the focuses of this study. We used five datasets with four models (Random Forest - RF, Gradient Boosted Machine - GBM, C5.0, and multinomial log-linear model - MLR). The covariates were grouped into five datasets, where four were grouped by Region Of Interest per Class (ROIC) and one was not grouped by ROIC. To evaluate the random effect to split the dataset, we ran each model 50 times and observed the overall accuracy (OA) and kappa index, and uncertainty, majority and variety maps. The OA of Dataset01 to 04 was lower than to Dataset05 accuracy. However, map outputs of RF and GBM for Dataset01 and Dataset05 had the same majority prediction. It seems that RF and GBM produce consistent results in map outputs according to this methodology and pedologist expertise. To evaluate the uncertainty and the consistency of soil unit prediction, we used the majority maps process. Random Forest, similar to GBM, presented the best results. The increase in the number of covariates was not a guarantee of improvement in the OA or in the quality of the map output. Geographic position and distance raster did not improve the map output according to expert evaluation. Because the variance between the ROICs, when the training and validation datasets were split based on it, the subsets are quite different in relation to the covariates, and this is the reason for the worse results of this model, comparing with the Dataset05. On the other hand, when considering one complete dataset not based on ROICs, the variance of training and validation subsets is lower and produced more accurate parameters of quality.

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ABSTRACT The northwestern part of the Acre State (Brazil) possesses singular soils in Brazilian Amazonia, but have been very little studied. This study aimed to discuss the genesis and some micropedological aspects of the soils from Serra do Divisor and adjacent floodplain soils of the Moa river, to enhance the knowledge on their formation. A toposequence of soils ranging from the uppermost part of sub-Andean Serra do Divisor to the Alluvial soils of Moa river floodplain was studied, regarding chemical, physical, mineralogical, and micromorphological attributes. The parent material of the Serra do Divisor is basically quartzose sandstone, and the soils along the toposequence were classified as Typic Haplorthods (P1), Spodic Quartzipsamment (P2), Lithic Quartzipsamment (P3), and Lithic Quartzipsamment (P4). Along the Moa river floodplain, we also identified and collected, Typic Udifluvent (P5), Typic Kandiudult (P6), Typic Kandiudalf (P7), and Arenic Plinthic Kandiudult (P8). The Serra do Divisor soils have very low fertility, high acidity, and low cation exchange capacities, presenting a coarse sandy texture, even shallow pedons. The X-ray diffraction analysis of these soils indicates the predominance of kaolinite, with traces of quartz and gibbsite. The shallow mountain Podzols on sandstone have an expressive accumulation of organic material in surface horizons, with evidence of ferrihydrite and imogolite in the subsurface. At the Moa river floodplain, all soils are originated from recent sediments (Cenozoic), which have a geological source upstream. Varying sedimentary layers are key aspects influencing soil genesis. Those soils have evidence of 2:1 clays with hydroxyl-Al interlayers in subsurface horizons. The Serra do Divisor steep landforms and the coarse texture of the soils promote good drainage and favor leaching and chemical impoverishment. Kaolinite and gibbsite were formed by severe leaching and there are evidences of in situ neoformation of gibbsite by extreme Si losses. All studied soils have some peculiarities such as high accumulation of organic material or 2:1 clay minerals. Most investigated soils were affected by colluvial, reworking, mass movements or a strong variation on sedimentation.

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ABSTRACT The term Post-Barreiras is a definition for sediments above the deposits of the Barreiras Formation, and the genesis of soils in these environments must be related to sedimentary deposition. Our objective was to apply multi-technique analyses to characterize the sediments and soils to understand pedogenesis in these environments. We analysed sedimentological parameters and the geochronology of sediments. Morphological, chemical, and mineralogical analyses allowed the characterization of the soil. Also, these data supported the analysis of lithological discontinuity. We considered the contents of Ti and Zr, uniformity value, the fraction of organic material, morphology, and palynological analysis. The age of Post-Barreiras sediments is from the Pleistocene, and they have a more significant variation of sedimentological parameters concerning Barreiras Formation layers. In general, the soils are sandy, acidic, have a low level of exchangeable cations. Mineralogy has a predominance of quartz and kaolinite minerals. In the region, there are soils with low morphological variation, classified as Quartzipsamments. In other cases, there are soils with apparent spodic morphology, which is conditioned by four aspects: (i) Podzolization in Post-Barreiras sandy sediments without evidence of lithological discontinuity, forming Bs horizon (Spodosols); (ii) contact zones (Post-Barreiras/Barreiras Formation) with physical, chemical, and morphological evidence of discontinuity, forming Quartzipsamments or Ultisols; (iii) layers of the Barreiras Formation buried by Post-Barreiras sediments and the subsequent podzolization process, forming Bhm horizon (Spodosols); and (iv) destruction of Ultisols clay, forming Bs horizon (Spodosols). The sedimentary association (Post-Barreiras/Barreiras Formation) favors the development of different soils. The contact zones generate a morphological aspect similar to the Spodosols, associated or not with podzolization processes.

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ABSTRACT The assessment of spatial variability of environmental variables such as soil properties is important for site-specific management. A geostatistical index that allows quantifying and characterizing the structure of spatial variability is fundamental in this context. Thus, this study aimed to develop a new spatial dependency index, called the Spatial Dependence Measure (SDM) for the spherical, exponential, Gaussian, cubic, pentaspherical, and wave semivariogram models; and comparing it with some of the indexes available in the literature. The SDM is also dimensionless, in the same way as the Spatial Dependence Index (SDI), also considering more parameters of the semivariogram, when compared to the Spatial Dependence Degree (SPD) and Relative Nugget Effect (NE) indexes. In a simulation data study, it is observed that the SDI and SDM indexes showed an advantage over the SPD (or NE). To exemplify the application of the SDM in the proposal for the classification of soil properties, we used estimates of geostatistical parameters presented in the two studies. The results indicate that the SDM can be a measure that, analyzed together with the SDI, can help to improve the description of the spatial variability structure. Thus, this study expands the number of geostatisitcal-based measures and increases the power of decision on the description of the degree of spatial variability of agricultural and soil attributes.

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ABSTRACT Soils in alluvial plains of the lower course of the Acaraú River, Ceará State, Brazil, are weakly developed and have a complex distribution in the landscape. This study reports the pedogenic characterization of such soils in an effort to understand their formation. Soil pits were opened in four representative sites, profile morphology was described, and soil samples were collected for chemical, physical, mineralogical, and micromorphological analyses. All profiles had weak pedogenic development, as inferred from their morphological characteristics, lack of B horizon, and high silt/clay ratio. Organic carbon and particle size distributions were heterogeneous in Fluvisol, Planosol, and Solonchak, in agreement with their sedimentary nature. Intrinsic characteristics of each profile indicated variations in pedogenic processes related to depositional conditions, which, in turn, were determined by the alluvial nature of sediments and water table dynamics. Consequently, Fluvisols at higher elevations showed reduced pedogenic development. In adjacent areas, Planosols showed pores filled with clay minerals and a texture gradient, indicative of past lessivage. Vertisol was identified in small depressions and exhibited intense pedoturbation and high sodium concentration in deep layers. Solonchak had a high degree of hydromorphism, high sodium concentration, and high electrical conductivity. The distinct pedogenesis of alluvial plain soils in Northeastern Brazil is evidenced by their morphological, chemical, and physical properties.

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ABSTRACT The classification of Spodosols on the second categorical level (suborder), according to the Brazilian Soil Classification System (SiBCS), is done by observing the colors of genetic horizons in the field. The presence or absence of iron oxides is the main factor for this classification, and the color of the horizon is the criterion currently adopted. However, the simple observation of color in the field can be mistaken and cause an error in the definition of the second categorical level. This occurs when spodic horizons that do not contain iron oxides show high chroma color, or dark color due to the organic matter content, which masks the presence of iluviated Fe produced by podzolization. This can lead to errors, such as classifying Humiluvico horizons as Ferriluvico, and Ferri-humiluvico horizons as Humiluvico. These misunderstandings are currently solved through complex analyses using specific extractors and sophisticated equipment. Thus, obtaining a simple, fast, and inexpensive method to confirm the presence or absence of iron oxides in samples of spodic horizons is needed. This study tested an alternative method to assist in the determination of the second categorical level of the class of coastal plain Spodosols. The method consists of calcining samples in a muffle at 600 °C for 6 h. The calcination enabled to identify spodic horizons with and without presence of iron quickly; the result was compared with selective extraction analyses carried out using three different extractors: sodium pyrophosphate, ammonium acid oxalate, and sodium dithionite-citrate. The results obtained from these methods (calcination in muffle and selective extraction of iron oxides) enabled the identification of samples presenting colors varying from yellow to reddish, indicating the presence of iron, whereas those with the whitish color indicated absence or very low iron oxide levels. The 12 profiles of Spodosols were described and classified according to the SiBCS, and six profiles needed to be reclassified after the calcination procedure, which proved to be efficient.

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ABSTRACT Páramo ecosystems are of great importance because they are considered hotspots within the Tropical Andes. They are also very important for their role as producers and regulators of water processes in the Neotropic. However, the human occupation of the Colombian Páramos has generated conflict between environmental benefits and productive land uses, specifically the potato cultivation and livestock. To assess possible changes associated with potato cultivation (Solanum tuberosum L.) and livestock on the microbial communities of Páramo soils, the objective of this research was to evaluate the possible effects of potato cultivation and livestock farming on the soil microorganisms associated with different functional groups (nitrogen fixers, phosphate solubilizers and cellulolytic) in the Páramo of Nevados National Natural Park (Nevados NNP), Colombia. Samples were collected from soils under potato cultivation, livestock, and Páramo conservation areas over two climatic seasons (rainy and dry) in three farms at different elevations (3769, 3590, and 3432 m a.s.l.). The microorganisms were isolated using selective culture media for each functional group and identified using molecular markers; microbial diversity was analyzed using multivariate statistical tools. Changes were dependent on land use, elevation, and climate and were statistically significant in the rainy season on all three farms and one of the farms during the dry season. Similarly, the results indicated that climate has a greater impact on the evaluated microbial communities than land use does; the changes were significantly different between the soil under potato cultivation and in conserved Páramo sites at most of the evaluated locations and between soil subjected to livestock farming and Páramo in certain locations. However, the differences between potato cultivation and livestock farming were smaller. This study showed for the first time that the microbial structure (abundance and composition) of microorganism functional groups was different as a result of potato cultivation and livestock farming on Páramo soils, although these changes were dependent on farm elevation and climate.

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ABSTRACT The mechanized management systems used in Brazilian coffee plantations generate heavy machine traffic and lead to the application of loads on the soil that affect the soil structure and lead to widespread compaction. This study aimed to evaluate the influence of mechanized operations on coffee plantations with different deployment times on the soil structural quality of an Ultisol, based on its soil physical properties and soil load-bearing capacity. The experiment was carried out in Muzambinho, São Paulo State, Southeast Brazil, in coffee plantations (Coffee arabica L.) with 3, 16, and 32 years of service. In each area, corresponding to the coffee plantation’s establishment period, soil samples were collected in the planting row (R), under the coffee canopy (UCC), and inter-row center (IRC) at the layers of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m to evaluate soil penetration resistance, bulk density, porosity, wet aggregate stability, and preconsolidation pressure, to model soil load-bearing capacity. The deployment time of the coffee crop was a decisive factor in reducing the deterioration of the soil structure in the row, which was confirmed by better structural quality in the plantations with 16 and 32 years of establishment. Irrespective of crop deployment time, the effects of intensive machinery traffic on the coffee crop in the middle between the rows and in the area under the canopy are similar, resulting in high soil compaction, reflected in soil penetration resistance, soil bulk density, macroporosity, and load-bearing capacity. The longer the deployment time of the coffee cultivation areas (32 and 16 years), the higher the stability of the soil aggregates, and the larger the mean aggregate size.

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ABSTRACT The least limiting water range (LLWR) has been extensively determined, but evaluating if LLWR can indeed indicate soil physical stress on plant growth is still a controversial issue. In this study, we used the Hydrus-1D hydrological model to simulate root water uptake (RWU) to analyze if RWU and LLWR are correlated under stress conditions. The LLWR was determined in a sandy-loam Ultisol and a clayey Oxisol. In both soils, RWU extracted by plants (leaf area index set as 3) from a rooted layer of 0.4 m was simulated over 20 days under a potential evapotranspiration rate of 6 mm day-1. For each soil, RWU was simulated over the same range of soil compaction in which LLWR was determined. The cumulative RWU over the 20 days varied between 23 to 58 mm in the Ultisol and 20 to 48 mm in the Oxisol, indicating that plants were able to take up only a small part of the cumulative potential transpiration (93 mm) and experienced severe water stress in some soil conditions. However, RWU under water stress was poorly correlated with both bulk density and LLWR. The correlation between RWU and LLWR was 0.5 (p<0.01) for the Ultisol and 0.22 (p<0.19) for the Oxisol, suggesting that LLRW has little (for Ultisol) or almost no (for Oxisol) ability to indicate soil quality related to plant water availability. Our simulations suggest that RWU in the water availability range (between field capacity and wilting point) may be little affected or even improved by light soil compaction. Studies to elucidate this phenomenon would contribute to the understanding of the compaction effect on RWU and the weak correlation between RWU and LLWR.

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ABSTRACT Regularly spaced earth mounds called “murundus” are scattered in several landscapes in the semi-arid region of Brazil. Although recent evidence indicates that termites are involved in the building of murundus, the contribution of these insects to soil-forming processes in those structures remains poorly understood. In this study, we tested a set of hypotheses to examine whether there are consistent evidence for suggesting the participation of termites in the formation of murundus soils. Morphological and physicochemical features of murundus were compared with adjacent soil profiles in the inter-mounds surface and one epigeic nest built by one species of Syntermes Holmgren. The murundus soils had a more clayey texture, higher contents of nutrients (C, N, P, K, Ca, and Mg) and organic matter compared with adjacent soils. We identified a set of recent and ancient traces inside the murundus that reveals the intense building activity of termite colonies (e.g., galleries, tunnels, and royal chambers), confirming that these structures are not only occupied by these insects but also built-up by them. Taken together, our results provide hard evidence that the long-term activity of mound-building termites was the hierarchically dominant process in producing murundus structures in the semi-arid region of Brazil. Based on available empirical data, we propose an explanatory model on how that construction process may have taken place.

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ABSTRACT Simulation models are efficient tools to predict the fate of different solutes in agricultural soils. This work aimed to compare measured and predicted glyphosate and AMPA (aminomethyl phosphonic acid; its main metabolite) contents in a soil under no-tillage (NT), and conventional tillage (CT); and to compare the predictions considering constant and time-variable hydraulic properties. Additionally, we evaluated the ability of the model to predict glyphosate and AMPA accumulation during the crop cycle. Hydrus 1-D code was used to predict the glyphosate and AMPA dynamics, considering constant and time-variable hydraulic properties during the studied crop cycle. In general, the prediction of glyphosate and AMPA distribution along the soil profile using HYDRUS 1-D was satisfactory; however, an overestimation of both compounds was observed in the first 0.20 m of the soil probably because of the preferential flow. Additionally, the accumulation process of glyphosate and AMPA in the soil during the crop cycle was underestimated by HYDRUS 1-D, as compared with the observed field data. Simulated data show that higher values of K0 increase the risk of glyphosate and AMPA vertical transport. The inclusion of temporal variation of hydraulic properties in glyphosate and AMPA simulation did not improve the simulation performance, showing that the model is more sensitive to the parameters related to the solutes. From the obtained results, HYDRUS 1-D code allowed to predict glyphosate and AMPA dynamics reasonably well in agricultural soils of the Argentinean Pampas region and is a potential model to give support in the analysis of the environmental risk of leaching and soil contamination.

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ABSTRACT Given the influence of edaphic macrofauna in the physical, chemical, and biological processes that sustain the organic matter cycle in the soil of tropical ecosystems, this study aimed to evaluate the effect of the sequence: Secondary Forest – Pasture – Eucalyptus monoculture on the macrofauna structure in Southeast of Pará State, Brazil. In each land use system, two 350 m transect were taken. The data was collected in 8 sampling sites, which were 50 m apart in each transect at 0.10 and 0.20 m depths. Correlations between the community structure Family Richness (S), Shannon-Wiener diversity index (H’), Pielou equitability (J), and macrofauna density (ind. m-2) were tested with soil pH(H2O), Al3+, Ca2+, Mg2+, K+, P, SOC, N, Fe, Zn, and Mn and the litter dry matter total content of Ca, Mg, K, P, TOC., N, Fe, Zn. The land use has affected the macrofauna community parameters S, H’, and J (p<0.05). The macrofauna density did not differ between land use systems Pasture and Secondary Forest (p>0.05). The evaluated indexes were highly correlated with the disturbance level, increasing gradually from the Pasture, where the lowest levels were found, to the Secondary Forest with the best indexes in this study, with 29 families exclusive to this land use system. Correlations between the community structure and soil and litter chemical parameters were not detected.

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ABSTRACT Soil beetles’ communities are responsible for many ecosystem services, and are very sensitive to environmental changes. Thus, this study aimed to evaluate the abundance and diversity of the soil coleoptera fauna under uses and management and also to identify relationships of the beetle community with soil’s physical and chemical properties. The experiment had six experimental plots set up an Oxisol (Latossolo): corn (CO), soybean (SO), 7-year-old eucalyptus (EI), 4-year-old eucalyptus (EII), preserved Cerrado (PC), and disturbed Cerrado (DC). Soil beetles were sampled at 128 points for each experimental plot, where the soil physical and chemical properties were analyzed. The Coleoptera fauna organisms were identified at the family, subfamily, and gender level, and then, the number of individuals per day, richness, Shannon diversity indexes, and Pielou evenness were determined. The data were analyzed using multivariate techniques (hierarchical grouping and factor analysis). On total, 750 specimens of beetles were collected, distributed into 9 families, 14 subfamilies, and 27 genera. The most abundant family was Scarabaeidae (11 genera) with the highest occurrence in the PC (143 specimens) and DC (81 specimens). Cultivation with SO presented the greatest number of trap day individuals (ind trap-1 day-1 = 0.548); however, the highest diversity was found in the PC. (20 taxonomic groups) and CO (16 taxonomic groups). Shannon diversity was higher for the CO (H’ = 3.107), followed by the PC (H’ = 2.699), and the lowest value was found for the SO (H’ = 1.530). The similarity dendrogram grouped the plots into two extracts, demonstrating how the intensity of land use influences the abundance and diversity of beetle fauna. The factor analysis grouped the Coleoptera and the physical and chemical soil properties in two factors: elements related to the state of aggregation and porous system’s elements. The Coleoptera community was influenced by the intensity of land use and the portion with anthropized natural vegetation showed the highest richness, demonstrating that the Coleoptera fauna responds to environmental changes. Edaphic beetles in the different use and management systems were primarily related to soil physical properties, which explain the state of aggregation (pH, altitude, Ca2+, BD, clay, macroporosity, silt, K+, and microporosity) and the porous soil system (sand and total porosity).

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ABSTRACT Nitrous oxide (N2O) is a greenhouse gas that contributes substantially to global climate change. The N2O soil emissions have a large uncertainty because of its low atmospheric concentration levels and enormous spatial and temporal variability, which hinders its correct field measurement. For this reason, there are many papers focused on improving the N2O measurements in the field, which focus on different parts of the measurement process. However, no studies have focused on determining the appropriate method, in terms of simplicity and precision, for the sample extraction from inside of the chambers and its transfer to the storage vials, although this step is key in the sampling process. This study aimed to assess and compare the accuracies of three simple and economical methods in transfer soil emitted N2O from inside of the chambers to the vials. For this, a highly accepted method (vacuum by manual pump) and two simpler alternative methods (gas exchange by displacement and vacuum by syringe) were compared. Thirty static chambers were assessed with the quantified N2O emission values varied from 0 to 450 µg m-2 h-1 of N-N2O. Out of the three assessed methods, the vacuum method through the use of a manual vacuum pump was the best to quantifying N2O soil emissions (capturing 57 % of the highest emission values), followed by the gas exchange method by displacement (30 %), and finally by the vacuum method by syringe extraction (13%).

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ABSTRACT Cultivated soils, when submitted to agricultural practices, tend to compact due to the pressure exerted by agricultural machines and implements, a process that compromises soil quality and system sustainability. Specific properties of each soil, such as particle size and organic matter content, interfere with the process and degree of compaction and, consequently, plant growth. This study aimed to analyze the effect of different degrees of compaction (DC) on soil physical properties and black oat (Avena strigosa Schreb) growth. For this purpose, four soils were collected: Latossolo Vermelho distrófico retrático (Ferralsol LVCN), Cambissolo Húmico alumínico típico (Cambisol CHLG), Nitossolo Bruno distrófico típico (Nitisol NBPA), and Nitossolo Bruno distrófico húmico (Nitisol NBSJ). They were submitted to five degrees of compaction (bulk densities corresponding to 80, 85, 90, 95, and 100 % DC), defined by their relation to the maximum density obtained by the Normal Proctor Test. For each DC, porosity, soil water retention curve, penetration resistance, hydraulic conductivity, and aeration capacity were determined. In a greenhouse, the oats were cultivated in the four soils with five different degrees of compaction. The experiment was carried out in a completely randomized design, factorial scheme, and five replications. Crop measurements included the growth rate, shoot dry matter, and forage quality analysis. Soil compaction changed the physical properties of soils. In all tested soils, macroporosity and total porosity decreased, more intensely at LVCN. It had macroporosity below the critical level (0.10 m3 m-3) from DC 85. Hydraulic conductivity also decreased in all soils, which is evidence of significant environmental degradation from DC 90 onwards. Microporosity increased in the four soils due to compaction effect, and it is one of the reasons why permanent wilting point has increased. It resulted in a problem at NBSJ, mainly because it reduced the available water volume at DC 90, 95, and 100. Penetration resistance has also increased from DC 80 to 100 at all soils, exceeding the limit of 2 MPa in DC 80 for NBSJ, DC 85 for NBPA and LVCN, and DC 95 for CHLG, representing a risk to root development. Regarding black oat crop, there was a reduction in shoot dry matter only in Cambisol and in the higher DC, fiber content keeps within a satisfactory amount, without affecting forage quality in all soils and DC, thus showing that black oat is tolerant to compaction.

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ABSTRACT Most of the forensic comparison of soils has focused on the clay and silt fractions at the expense of the coarser particles. This study aimed to test the potential of elemental and physical analyses in the sand fraction from subtropical soils to discriminate samples collected in areas under different parent material (claystone and marble) and in areas with the same parent material at a simulated crime scene. Scanning electron microscopy coupled to an energy dispersive X-ray spectrometer (SEM-EDS) analysis was used on the finer sized sand particles (0.05-0.25 mm). X-ray diffraction (XRD) and particle size distribution (PSD) analyses were performed on the whole sand fraction. These methods did not provide clear discrimination of the sand of the soils sampled in the subtropical environment. This can be explained by the large homogenization observed in the sand fraction related to its chemical (EDS), physical (particle size distribution), morphological (SEM), and mineralogical (XRD). Under tropical and subtropical conditions, the chemical weathering processes dissolve most of the primary minerals, such as the feldspars, biotite, and Fe-bearing particles, and concentrates quartz in the sand fraction. In these environments, we recommend the prioritization of the finer soil fractions for forensic studies, both inorganic and organic.

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ABSTRACT One of the challenges in rice areas is the sustainable post-harvest system, which involves using rice straw management and cover crop species. In this context, this study aimed to evaluate the emission of methane (CH4) and nitrous oxide (N2O) with the use of different post-harvest management of rice straw as well as with the combined use of ryegrass. A field experiment was conducted during the 2016 off-season and 2016/17 rice crop season with different post-harvest rice straw management: maintaining rice straw on the soil surface (No-tillage); incorporating straw into dry soil with a disc (Disc); incorporating straw into flooded soil with a roller crimper (Roller Crimper); maintaining rice straw on the soil surface with subsequent rolling of the soil with a roller (Roller). In each straw management, treatments with and without ryegrass were established. The results demonstrate that incorporating rice straw in flooded soil with a roller crimper increases CH4 emissions in the off-season, and used in combination with ryegrass, proved to be the most significant contributor to partial global warming potential. Most annual N2O emissions occur in the off-season for all management treatments, especially for the no-tillage treatment, which showed increased emissions when combined with the use of ryegrass. However, as global warming potential is influenced mainly by emissions of CH4, the no-tillage system showed the best mitigation potential on greenhouse gas emissions.

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ABSTRACT Soils originating from the Caiuá sandstone formation have low soil organic matter (SOM), clay content, and cation exchange capacity (CEC). The predominance of one component over the other might decisively influence the CEC of these soils. Particle size distribution and selective dissolution procedures associated to a suit of methods to determine the exchangeable capacity properties might clarify the relative importance of each soil component. The objective of this work was to evaluate the contribution of the different components of the solid fraction and their intrinsic attributes to the CEC of sandy-loam soils and their relation to the total organic carbon (TOC), C:N ratio, and soil mineralogy. For this purpose, 34 soil samples were selected from the Caiuá sandstone formation with significant variation in the carbon content. Clay size fraction was characterized by X-ray diffraction, routine chemical analysis, and total specific surface area-SSA T using EGME, before and after the removal of SOM with sodium hypochlorite solution. Different values of CEC and effective cation exchange capacity (ECEC) were determined following standard procedures. The soils presented high sand content (82.9 ± 5.9 %) and the mineralogy of the clay fraction is dominated by kaolinite (>80 %) with the presence of illite, 2:1 clay minerals, and small amounts of iron and aluminum oxides. The CEC and ECEC values at pH 7.0 and ~5.6, respectively due to the SOM are 408.6 and 148.7 cmol c kg -1 of carbon, respectively. The SOM was responsible for 32 to 84 % (average 52 %) and 24 to 67 % (average of 46 %) of the CEC and ECEC of the soils, respectively. The CEC and ECEC of the inorganic fraction are 2.32 and 0.78 cmol c kg -1 of minerals, respectively. The CEC of the clay fraction increased with the TOC but decreased exponentially with the clay content. The total carbon content increased linearly with the C/N ratio. The SSA T showed a significant (p<0.05) and positive correlation with the TOC and with the CEC of the soils.

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ABSTRACT In sandy areas of Northern Shaanxi, after potato harvest, there are large areas of soil exposed to wind erosion from winter to spring, leading to degradation of soil quality. Planting cover crops in fallow fields is considered effective to improve soil biological properties; however, there is scarce study on the effect of winter cover crops on fallow soils in this region. In the study lasting from 2017 to 2019, four winter cover crops, i.e., alfalfa (AC), sweetclover (SC), winter wheat (WC), and ryegrass (RC), as well as bare land (CK), were used to study the effect of winter cover crops on soil microbial characteristics. The experiment showed that the soils in AC treatment had the highest values of microbial biomass N (MBN) content, dehydrogenase and urease activities, bacteria colonies, and Shannon and Richness indices. The soils in SC treatment had the maximum values of microbial biomass C (MBC) content, protease activity, fungi colonies, and Simpson index. Under AC and SC treatments, microbial communities in soil showed the highest percentage of carbon source utilization for amino acids, carbohydrates, and amines. Alfalfa and sweetclover as cover crops were helpful to improve the activity and diversity of soil microorganisms, exerting a positive effect on soil quality. This finding is of great significance for improving the methods of mitigating soil degradation in winter fallow fields of Northern Shaanxi, China.

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ABSTRACT Corn and garlic are important crops to Curitibanos region (state of Santa Catarina – Brazil), often planted in alternate cropping seasons. Production costs are high, especially due to N fertilizer, since they are highly demanding in N. In addition to reducing economic costs, the search for environmentally sustainable technologies has stimulated the study of interactions between plants and growth-promoting microorganisms. Rhizobacteria, e.g., Bacillus sp., have been presenting as growth-promoting microorganisms. Five isolates of garlic rhizosphere from 27 individuals of the Plant Growth Promoting Microorganisms group collection were tested on corn under field conditions, comparing to two levels of nitrogen fertilization: 120 and 60 kg ha-1. The Bacillus collection was also evaluated in vitro for phosphate solubilization, production of IAA (Indole Acetic Acid), extracellular enzymes, and inhibition of Sclerotium cepivorum. For plant height and stalk diameter, the inoculation of the EB16 isolate showed similar results to the fertilization with 120 and 60 kg ha-1 of N in corn. Both EB16 and EB02 isolates increased corn ear diameter and the yield was similar to that observed in the treatment with 60 kg ha-1 of N, indicating their potential as growth-promoters. All strains of the collection produced IAA, and most of them solubilized calcium phosphate and produced lipases and urease. Forty-eight percent of the isolates inhibited S. cepivorum. The EB01, EB15, EB17, and EB27 were positive for three of the four mechanisms analyzed. During these evaluations, it was observed that EB02 and EB16 produced equivalent amounts of IAA, suggesting that more than one growth-promoting mechanism is involved in the efficiency of corn development induction.

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ABSTRACT Soil microbiota is an important component of the forest biomes, playing important roles in the soil aggregation and cycling of nutrients. Among the soil microorganisms stand out the yeasts, which are unicellular fungi involved in important soil ecological processes. The Brazilian Atlantic Forest is one of the main biodiversity hotspots in the world, and the effect of altitudinal gradient on the distribution patterns of yeast species across this ecosystem has not yet been addressed. Thus, this study aimed to investigate the occurrence and distribution of yeast species in soils along an altitude gradient (404; 1,016; 1,658; and 2,124 m above the sea level) of Serra dos Órgãos National Park located at Rio de Janeiro State, Brazil. Yeast species were described using a culture-based method. Species identification was performed using the fungal barcode locus, the D1/D2 region of 26S rRNA, and the gene genealogy was used to access the intraspecific distribution of strains along the altitudinal gradient. We isolated and identified a total of 76 yeasts including ten species belonging to eight genera. Basidiomycetes predominated over ascomycetes. Saitozyma podzolica and Meyerozyma guilliermondii were isolated at all altitudes. The principal component analysis showed that 88 % of sample distribution is explained by soil properties. For S. podzolica, the genetic genealogy suggested that intraspecific distribution is likely related to similar altitudes. Overall, the species composition and soil properties were modified as altitude was increasing, being more heterogeneous and richness in high altitudes.

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ABSTRACT Soil physical properties can be changed after vehicle traffic, especially by heavy military tracked vehicles. The Santa Maria military Instruction Field, where the experiment was carried out, is currently the most used area for armored tracked vehicles training in Brazil, with the M113 BR being the main equipment. The aim of this study was to determine the effect of the straight line and pivoted traffic intensity of the M113 BR on the physical properties and advancement of the compaction state of an Abruptic Alisol (Argissolo Vermelho-Amarelo Ta Distrófico abrúptico) with military vehicle traffic history. The study was conducted in a completely randomized design, independently evaluating the effect of straight and pivoting traffic in three soil layers (0.00-0.04, 0.10-0.14, and 0.20-0.24 m). For the straight-line traffic, traffic intensities (TI) with one (TI1), two (TI2), and five (TI5) passes on the same trail were evaluated. For the pivoting traffic, TI with one (TI1P) and two (TI2P) pivots was evaluated. Both studies had two non-traffic treatments (NT). The soil bulk density, total porosity, macroporosity, microporosity, saturated soil hydraulic conductivity, soil penetration resistance, soil bearing capacity, preconsolidation pressure, and gravimetric water content were analyzed in this study. In the straight-line traffic, cases with no significant differences in TP, Ma, Mi, and Ks prevailed. The highest TP, smallest Bd and largest Mi were observed in the 0.10-0.14 m layer. In the pivoting traffic, one pass was sufficient to increase Bd and decrease TP, Ma, Mi, and Ks in the 0.00-0.04 m layer and the increase from one to two pivotings had a significant difference only in Mi in this same layer. Both types of traffic intensity did not affect the PR in any layer. The Abruptic Alisol, pre-compacted from long-term military training, supported the loads applied by the M113 BR when additional traffic occurred in straight line mode, but not when in pivoting mode. The preconsolidation pressure parameter was not appropriate to assess the ability of the soil to support loads applied by pivoting traffic.

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ABSTRACT Sorption of selenate (SeO 4 2- ) and selenite (SeO 3 2- ) is poorly understood in Brazilian agroecosystems, especially in soils from agricultural areas containing different contents of competing anions, such as sulfate (SO 4 2- ). This study aimed to assess the sorption behavior of selenate and selenite at different soil layers of a tropical soil treated with different rates of agricultural gypsum (thus, containing different contents of sulfate), collected under a coffee plantation. Soil samples from an experimental area where phosphogypsum has been previously applied at different rates (0, 7, 14, and 56 t ha -1 ) were taken at the following soil layers: 0.15-0.25, 0.35-0.45, and 1.25-1.35 m. Adsorption experiments were carried out adding 20 mL of solutions containing 100 and 500 μg L -1 of selenate and 10 and 15 mg L -1 of selenite to 2 grams of soil. Desorption experiments were also performed using a soil:solution ratio of 1:10. Adsorption of selenate increased with soil depth and decreased upon increasing sulfate contents in the soil, by contrast, selenite was consistently adsorbed at higher contents - when compared with selenate - at any soil depth and its sorptive behavior was not affected by the presence of sulfate. Furthermore, selenite was less desorbed than selenate under all conditions. In conclusion, selenite is much more retained in tropical soils and less available to plants than selenate. Also, although sulfate has shown to be able to hinder selenate retention, it has no substantial effect on the sorption behavior of selenite in tropical agroecosystems.

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ABSTRACT Drought and soil salinity are the main abiotic stresses in semiarid regions of the world. This study aims to evaluate the effect of water tensions generated by the reduction of soil moisture and salt on the leaf water potential of cowpea (Vigna unguiculata L. Walp). The experiments were conducted in a randomized complete block design, with a 6 × 2 factorial arrangement consisted of six soil water tensions (0.025, 0.265, 0.485, 0.705, 0.925, and 1.145 MPa) and two tension sources (water deficit and salt), with four replications. Two experiments were performed with the same environmental conditions to evaluate the influence of the tensions on vegetative and reproductive stages. Water and osmotic potentials, relative water content, leaf succulence, and shoot biomass yield were evaluated. Soil water tension was not the main factor of changes on water and osmotic potentials of V. unguiculata plants; the water deficit treatments at soil water tensions of up to 1.145 MPa did not reduce the water and osmotic potentials either at the vegetative or flowering phenological stages; high correlations were found between shoot biomass yield and the leaf water potential at seven days after stress. The osmotic potential was the main indicator of stress in plants at the vegetative and flowering stages subjected to water deficit by the presence of salts in the soil solution.

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ABSTRACT Fungi are ubiquitous components of soil microbial communities, generally comprise the largest proportion of soil biomass. They can occur as filamentous forms or unicellular yeasts, in both, as free-living or symbionts. Next generation sequencing has allowed greater depth of the access to soil fungal diversity complementing culture-dependent results. In Brazil, the state of Minas Gerais is recognized for its mining activity, which modifies the vegetation cover and consequently the soil microbial communities. To describe the fungal community (total fungi and yeast) in a post-mining area, comparing natural and modified ecosystems, we used environmental metabarcoding of ITS2 region. We assessed four ecosystems, with different vegetation and levels of impact, ranging from none to high impact (Atlantic forest, Iron outcrops, Eucalyptus, and Grass). Sequence data were compared with culture data obtained from previous studies. The fungal communities (total fungi and yeast) were more similar between Eucalyptus and Atlantic Forest, while Grass and Iron outcrops ecosystems showed greater dissimilarity. Despite its modified state, Grass ecosystem presented the highest alpha diversity values. Yeasts represented a proportion of fungal communities ranging from 1.7 to 17 % of fungal sequences in soil. The Ascomycota:Basidiomycota ratio was higher for the total fungi analysis, while a greater proportion of Basidiomycota was observed with the yeast analysis. Grass ecosystem was the only exception, where a higher proportion of ascomycetous yeasts was detected. The yeast communities responded to the environmental stress caused by the mining activity, resulting in changes in the composition, mainly increasing the abundance of black yeasts. Saitozyma podzolica relative abundance obtained with ITS sequencing was coherent with the findings obtained with culture data. Despite greater diversity depth obtained by metabarcoding, sequence and culture data were complementary tools in describing the fungal soil community. This study contributes significantly to the inventory of yeast species in tropical and subtropical soils.

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ABSTRACT Expansive clay soils are a problem for agriculture and engineering because they are susceptible to change in volume due to seasonal variation in water content and temperature. One of its morphological properties is slickensides, which result from the ability to contract and crack when dry and expand by wetting. The objective of this study was to evaluate the processes of expansion and formation and propagation of cracks due to the change in water content over time. The expansion process was evaluated through simple edometric tests with different external stress values applied to undisturbed soil samples. To evaluate the shrinking process, a device was developed to monitor the process of crack propagation. The mechanisms through which cracks begin and develop were studied using molded soil samples at the liquidity limit and at 1.25 times the liquidity limit with a drying and wetting cycle. Crack initiation conditions and development of geometric crack indices were measured with the water content and drying time. The soil presented medium to high expansion that depends on the overburden and suction applied, and the swelling stress was found to increase as suction increases. The changes in volume due to wetting and the propagation of cracks due to drying developed in three stages: initial, primary, and secondary. In the initial stage, few cracks or swelling occur with gradual variation in water content. As the water content approaches the limit of soil contraction (in the drying process) or the limit of soil saturation (in the wetting process), cracks and expansion developed slowly and approach a secondary stage. In the primary stage, cracks and expansion occurred rapidly with drying or wetting, respectively. Drying and wetting cycles showed similar crack patterns with the appearance of new micro-cracks during each new drying cycle.

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ABSTRACT Soil respiration represents the largest flux of CO2 emission from terrestrial ecosystems, being affected by land-use changes and soil properties. There are few studies investigating the response of soil respiration to land-use changes in the Caatinga biome. This study aimed to measure soil respiration from Caatinga vegetation and degraded pasture, to verify the effect of land-use changes on soil respiration. Measurements of soil respiration were performed using the infrared gas analyzer method over nine months (in rainy and dry seasons), in Caatinga and degraded pasture in the semi-arid region of Pernambuco. The soil moisture, soil temperature, soil organic carbon (SOC), Normalized Difference Vegetation Index (NDVI), and climatic variables were also measured. Soil organic carbon and NDVI were higher in Caatinga than in degraded pasture, while the inverse occurred with soil temperature. The soil respiration showed a clear seasonal variation, with the highest values occurring in the wet season, being positively correlated with soil moisture and negatively with soil temperature. Soil respiration was significantly higher in the Caatinga (8.0 ton ha-1 yr-1 of C) than in degraded pasture (3.7 ton ha-1 yr-1 of C). These higher values of soil respiration in Caatinga were due to lower soil temperature and higher SOC, and can be seen as indicators of good environmental quality.

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ABSTRACT The massive adoption of no-tillage (NT), along with the simplification of the cropping sequences has led to physical and chemical degradation of soils. To recover degraded soils, cover crops have been proposed as an alternative to increase soil organic carbon (SOC) and to improve soil physical quality (SPQ). This study aimed (i) to determine the content of SOC and its physical and chemical fractions at different layers and positions, in a soil with a soybean crop under NT with and without winter cover crops, and (ii) to determine SPQ indicators in a soybean crop under NT with and without winter cover crops. Measures and samples were made on a field experiment in a typical Argiudoll of the Argentinean Pampas. Soil organic carbon, coarse and fine particulate organic carbon (POCc and POCf), mineral associated organic carbon (MOC), fulvic acids (FA), humic acids (HA), and humins (H) were determined. Soil physical quality indicators determined were: soil bulk density and total porosity from field samples, and saturated hydraulic conductivity, water-conducting macro and mesoporosity, and total porosity connectivity from field water infiltration data. After eight years, cover crops did not cause any observable change in whole SOC content, but significant differences were observed for some SOC fractions. Humic acids and POCc had 40 and 25 % increases, respectively, in the cover crop treatment. Mineral associated organic carbon and H decreased by 9 and 7 % in cover crop treatment. Soil physical quality did not improve after eight years of cover crops. This can be related to degradation processes after 20 years of soybean monoculture under NT, and to the low ability of Argiudolls to recover from physical degradation.

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ABSTRACT Chemical soil analysis data can be expressed by weight (i.e., gravimetric basis) or volume (i.e., volumetric basis) of the fine earth (sieved ≥2 mm), resulting in different units, cmolc kg-1 and cmolc dm-3, respectively. The research problem is that the difference between methods to express the same soil properties hinders the comparison of results and database or dataset standardization. This paper aims to develop pedotransfer functions (PTF) to obtain the density of fine earth, which will then be used for conversion data expressed in volumetric to gravimetric basis, or vice versa, that will be applied to compare results and to standardize databases with different units. Soils samples, including profiles of the main soil orders in Brazil such as Latossolos (Ferralsols or Oxisols) and Argissolos (Acrisols or Ultisols), from the states of Rondônia, Roraima, and Mato Grosso do Sul (132 horizons) were selected and weighed (in triplicate) to obtain the fine earth mass contained in a volume of 10 cm3. The mass values were used to calculate the fine earth density. Spearman’s correlation analysis was used between the density and nine soil properties (coarse sand, fine sand, total sand, silt, clay, clay dispersed in water, clay dispersion, particle density, and organic carbon). The total sand, clay, and organic carbon showed the best correlations, therefore they were selected to construct the pedotransfer functions. Nonlinear regression techniques were used to obtain the models (PTFs) to predict density, which was used for unit conversion. As a result, the residual standard error (RSE) statistics of the models were: 0.0920, 0.1231, and 0.1633 g cm-3, respectively for PTF1 (using total sand as a predictor), PTF2 (using clay), and PTF3 (using organic carbon). Independent data was used to evaluate the accuracy of the models by residue analysis and the RSE. For the validation, the lowest RSE obtained was from the PTF1, so the best performance. Thus, to convert values of the chemical properties from a volumetric to gravimetric basis, the value must be divided by the predicted density. While, the conversion from gravimetric to volumetric basis requires that the value be multiplied by the predicted density. The PTFs using the properties total sand, clay, and organic carbon as predictor variables, allowed conversion of analytical data of soil samples expressed in the volumetric basis to gravimetric and vice versa, which can be used for dataset or database standardization.

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ABSTRACT The incorporation of nitrogen (N) fertilizers in the soil and the use of enzyme inhibitors (EI) can improve the efficiency of N fertilization by reducing losses by ammonia volatilization and nitrate leaching. This study aimed to evaluate the efficiency of EI addition and fertilizer incorporation on both grain and dry mass yields of corn as well as on some soil chemical properties, with focus on N availability. A field experiment was carried out for three years in randomized blocks with four replications. The treatments consisted of a 2 × 5 factorial, including two forms of fertilizers application: superficial (SUP) and incorporated (INC), allocated in the plots; and five fertilizations: mineral fertilizer (NPK); NPK + EI; pig slurry (PS); PS+EI; and control (TEST), allocated in the subplots. The soil mineral N content was determined at 30, 60, and 90 days after fertilizer application (DAA) and these times were considered as sub-subplots. All fertilizers increased the dry corn matter and grain yields and the soil availability of N, P, and K, mainly in the upper layer (0.00-0.05 m). However, only the PS promoted higher productivity when incorporated into the soil relative to the soil superficial application. The incorporation of fertilizers increases soil available P but has little effect on soil mineral N. The EI addition to the fertilizers promotes higher soil mineral N contents in the soil until 30 and 60 DAA respectively when superficially applied and soil incorporated, although this does not increase the corn productivity.

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ABSTRACT Soil erosion in tropical areas is a major problem for sustainability in agriculture and soil stability. In the Northwest of Paraná, cassava crop is produced using a conventional tillage system along a catena consisting of different soil classes: Ferralsols (near the summit), Lixisols (mid-slope), and Arenosols (foot-slope). Therefore, differential soil erosion rate and soil degradation are expected along the catena. Here, we test the erodibility of the three sandy soil classes in a representative catena of the Caiuá Sandstone Formation. Disturbed soil samples were collected from a depth of 0.20 m. The soil erodibility test was performed in the laboratory through a multi-drop rainfall simulator. A rainfall intensity of 55 mm h-1 with an energy of 453 Jm2 h-1 was applied for the rainsplash tests (splash pan), whereas a rainfall intensity of 65 mm h-1 with an energy of 534 Jm2 h-1 was applied for the soil erodibility tests (using a small flume). The three soils showed differences in soil particles detached by raindrop on very fine sand class <0.15 mm as follows: Ferralsols 10 %, Arenosol 12 %, and Lixisol 15 %. The maximum soil erodibility increased gradually according to the soil position on the catena: Ferralsols (1.81 × 106 kg s m-4), Lixisols (2.83 × 106 kg s m-4), and Arenosols (3.41 × 106 kg s m-4). Finally, the position of the soil along the catena and total sand were the best in explaining soil interrill erodibility. Therefore, farmers and stakeholders should be cautious about applying a homogeneous tillage system from the summit to the foot-slope along a catena with different sandy soils.

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ABSTRACT The recommendations of nitrogen (N) fertilization in garlic are still based on different varieties of the current types that are infected with phytopathogenic virus. There are several methods for recommendation of nitrogen (N) fertilization in garlic, but there are no enough methods for N diagnosis in garlic obtained by meristem culture. The objective of this work was to evaluate methods for diagnosing the nutritional status of virus-free garlic subjected to N doses through the use of a specific NO3- meter in soil solution and foliar sap, portable chlorophyll meter, N content in the leaf, and its relationship with yield and quality of the bulbs. The experiments were conducted with the use of virus-free seed bulbs from the meristem culture from three sites in the 2015 growing season and two locations in the 2016 growing season in South Brazil. The treatments consisted of the application of five nitrogen doses (0, 100, 200, 300, and 400 kg ha-1) distributed in three applications during the crop cycle: 1/3 in planting, 1/3 between 30 and 40 days after planting, and 1/3 after visual bulb differentiation. The highest commercial yield was associated with doses between 269 and 307 kg ha-1 of N and the content of 26 g kg-1 of N, in the diagnostic leaf. The relative chlorophyll content was the only diagnostic technology that showed a significant correlation with commercial yield in all experimental conditions. The evaluation of the N status in the virus-free garlic crop by a portable chlorophyll meter can be a quick strategy for recommending N fertilization and ensuring high yields.

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ABSTRACT In the tropics, water erosion is one of the most important factors leading to the degradation and deterioration of agricultural land. Olive orchards have a low canopy coverage, especially during the first years after planting, due to the low density of olive trees. Given the fast expansion of olive orchards in Brazil, this study aimed to evaluate the effect of cover vegetation on soil and water losses under natural rainfall. In addition, it was assessed the crop performance and the vegetation cover index in different management systems in olive orchards. The study was carried out in soil erosion plots, where water and sediment were sampled and measured over two crops season, under the following treatments: in the first season, bare soil with olive cultivation (OBS); olive trees intercropped with spontaneous vegetation (OSV); olive trees intercropped with jack beans (OJB); olive trees intercropped with millet (OM) and, as a control, only bare soil (BS). In the second season, the OM treatment was replaced by olive trees intercropped with sunn hemp (OSH). On bare soils, soil loss was the highest reaching 303.9 Mg ha-1 yr-1 and where the surface runoff amounted to 484.8 mm yr-1. However, in the absence of competition for resources with other crops, olive trees performed best under this system. The olive orchards planted in shallow and sloping soils without cover crops showed unsustainable soil loss, crusting, and sealing in the superficial soil layer, which can progress quickly for soil degradation in the future. The efficiency in the reduction of loss in relation to bare soil was 4.11 and 12.93 % for the soil loss and 12.15 and 25.17 % for water loss, respectively, for olive with spontaneous vegetation and olive with jack beans. Cover crops combined with olive trees, and reconciled with the crop performance aspects of cultivation in tropical regions, is of great relevance for improving sustainability, especially regarding the reduction of soil and water losses due to water erosion.

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ABSTRACT Increasingly rational use of phosphate fertilizers by agriculture is important, especially in Brazil, due to its importance for global food security and its high dependence on phosphate fertilizers for crop production. Thus, correlation and calibration researches with soil available phosphorus (P) extractants to improve the recommendation and the use of P are extremely important. Our objectives were (i) to determine soil P recovery rates and critical levels by the extractants Mehlich-1 (M1), Mehlich-3 (M3), and Ion Exchange Resin (RTI); (ii) to adjust predictive models of P recovery rates and critical levels for each extractant, as a function of soil properties related to the soil P buffer capacity, and (iii) to adjust the an interpretation table of soil P availability by M3 taking into account soil P buffer capacity indices. A pot experiment under greenhouse condition was conducted, in which the treatments were generated by the combination of a factorial 12 × 6, being 12 soil samples collected at a layer of 0.00-0.20 m, and six doses of P. The experimental units were constituted by plastic pots with capacity for 2.0 dm3 of soil, in which four hybrid corn plants (Zea mays L.) were cultivated for 45 d. The experimental design was a randomized complete block with four replicates. After cultivation, soil samples were collected from each experimental unit, and the determination of soil available P was performed by the extractants. The remaining P and the clay content were the soil properties that best correlated with the P recovery rates and P critical levels in the soil by the M1 and M3. The IER did not show sensitivity to soil P buffer capacity. The M3 had a discontinuous loss of extraction capacity with increasing soil P buffer capacity. Therefore, it is recommended the use of M3 as P extractant in soils with different characteristics, but a measure of soil P buffer capacity such as remaining P or clay content have to be used.

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ABSTRACT Considerable attention has been given to the development of new nutritional management strategies that can contribute to banana production be overestimated. The present study was motivated by the possibility that fertilizer application in front of the daughter plant might be more effective than application to the total banana production area. This study aimed to determine the most suitable site for soil collection to evaluate the chemical properties when fertilizer is applied in front of the daughter plant; to evaluate the efficacy of organic-mineral fertilizer in terms of soil nutrient availability, and to evaluate the effect on banana production. The experiment was conducted in three consolidated areas of banana plantation in Santa Catarina State. The effects of the combination of two main factors were evaluated: three fertilizer sources (mineral, mineral + organic compost or organic-mineral) and two application management (total area or in front of the plants), together with time (three years) and location (three municipalities). Each treatment was evaluated using a grid containing 20 banana plants (spaced at 2.5 × 2.5 m), with three replications of two plants in the central part. The experiment was arranged in a completely randomized design with three replicates. The use of a mineral source reduced the pH over the years, regardless of the application technique. Application of fertilizers in front of the daughter plant increased available P and K in the soil, compared to the application of fertilizers to the total area “uniformly distributed between banana planting lines and between plants”. In addition, the increase in soil P content was higher using organic-mineral sources. The nutrient contents in the banana leaves did not differ according to the fertilization source. The application of fertilizers in front of the daughter plant optimized banana fertilization and increased fruit production. Under these fertilization conditions, soil for chemical analyses should be collected at around 0.70 m from the site of fertilizer application.

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ABSTRACT Although agriculture and livestock systems represent important sources of N2O from the soil, they may also aid in emissions mitigation, mainly when integrated systems are taken into account, such as crop-livestock-forest, for food production. This work assessed the soil N2O emissions from a tropical Oxisol under row-crop, livestock, forest monocultures, and an integrated crop-livestock-forest system in the Southern Amazon - Brazil. Soil N2O emissions were measured using static chambers from November 2014 to October 2016 in four soil use systems [row-crop, livestock, forest, and integrated crop-livestock-forest (CLF)], and in a reference area under native forest fragment. For the whole period, the average of soil N2O fluxes was 16.9, 12.2, and 15.4 µg N2O-N m-2 h-1, to row-crop, livestock, and CLF systems, respectively, all with a similar average among them. The lowest fluxes were observed in the forest system and native forest fragment, with average fluxes of 4.0 and 6.3 µg N2O-N m-2 h-1, respectively, both lower than the agricultural systems. The largest soil N2O fluxes were observed throughout the rainy seasons in the row-crop, livestock, and CLF, mostly after N-fertilizer application to the soil surface or in the planted row. As a consequence, the cumulative emissions were greater in row-crop, livestock, and CLF systems, which in the averages of two cycles emitted respectively 1.40, 1.15, and 1.27 kg N2O-N ha-1 yr-1, all different of the forest system and native forest fragment (0.33 and 0.52 kg N2O-N ha-1 yr-1, respectively). Nitrogen fertilization and soil moisture influenced soil N2O emissions of all systems assessed in the Southern Amazon. The N2O emissions took place after both factors were met, corroborating the hole-in-the-pipe model. Even with more soil use intensification, once in the same area there were three cultures in succession during a year and perennial trees, CLF did not lead to greater N2O emissions from the soil than row-crop and livestock. Thus, CLF represents a good option for N2O mitigation for the edaphic and climatic conditions of the Southern Amazon.

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ABSTRACT The development of new fertilizer technologies to reduce nitrogen (N) losses from an agricultural system and to increase nitrogen use efficiency (NUE) is a global research objective. Controlled-release nitrogen fertilizers have shown great potential for reducing N losses and synchronizing N release according to crop demand, thereby improving the NUE. The objective of this study was to characterize controlled-release nitrogen fertilizers and compare them with conventional nitrogen sources in terms of N release, N loss via NH3 volatilization, and fertilizer effects on second-season corn. The field experiment was performed on an Ultisol in a randomized block design. The treatments consisted of two conventional nitrogen sources (urea and ammonium sulfate) and three brands of polymer-coated urea (PCU; Agrocote®, FortBlen®, and Kimcoat®). The variables N release and N loss by NH3 volatilization were subjected to nonlinear regression analysis using a logistic model and the Korsmeyer-Peppas model, respectively. Leaf N content and dry matter yield were subjected to the Tukey test, and the morphologies of the PCUs were observed by scanning electron microscopy (SEM). Electron micrographs revealed differences in the number of layers and the thickness of the coatings of the studied PCUs. FortBlen®, containing granules with single- or double-layer coatings with thicknesses ranging from 34.53 to 50.34 µm, promoted more gradual N release and reduced N-NH3 losses by 36.4 % compared with those observed with uncoated urea. Kimcoat® released approximately 98 % of the applied N within 24 hours, resulting in N-NH3 volatilization, and the responses in second-season corn were similar to those with uncoated urea. Although no benefits were observed in second-season corn for PCUs over uncoated nitrogen sources, some PCUs promoted more gradual N release and reduced N-NH3 volatilization, providing a promising alternative for environments prone to N loss.

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ABSTRACT Sweet potato crops take up large amounts of nutrients, especially nitrogen. In low-fertility soils, the addition of nitrogen (N) increases the sweet potato yield. Green manure may be an alternative method for improving soil quality and supplying nutrients to this crop. This study aimed to evaluate the plant’s nutritional status and the amount of nutrients taken up and removed by sweet potato plants subjected to green manure and mineral N fertilization. The experiment was carried out in the field for two growing seasons using a randomized block design in a split-plot scheme with four replications. The plots consisted of a control treatment (spontaneous weeds) and the previous cultivation of Crotalaria spectabilis and Mucuna aterrima. The subplots consisted of four N rates (0, 50, 100, and 200 kg ha-1) that were applied to the sweet potato. The species M. aterrima is more suitable for use as green manure in the sweet potato than C. spectabilis. Nitrogen application rates promoted a greater increase in the biomass of the storage root, nutrient uptake, and removal in the sweet potatoes unfertilized with green manure. In the sweet potato fertilized with M. aterrima, mineral N supply in excess (above 50 kg ha-1) increases the nutrient uptake and removal without a significant increase in the biomass of the storage root. In the sweet potatoes unfertilized with green manure, high rates of N (greater than 120 kg ha-1) must be applied to obtain the utmost biomass of the storage root, nutrient uptake and removal.

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ABSTRACT The adoption of more productive and nutrient-demanding genotypes, in addition soils with low availability of nutrients of soils under forest plantations, lead high fertilizer demand and justify research that seeks to rationalize the use of these inputs. Therefore, we aimed with this research to determine classes of interpretation of soil fertility using boundary line (BL) and estimate macronutrient sufficiency ranges for eucalyptus. Fertility classes and sufficiency ranges were obtained using a database of areas cultivated with eucalyptus in the Central-East region of Minas Gerais, Brazil, totaling 689 plots, containing information on yield, leaf contents, and soil chemical properties. Scatter plots were drawn relating the mean annual increment (MAI) in trunk volume (relative) with soil organic matter (OM), phosphorus (P), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) of the 0.00-0.20 m layer. Those graphs and equations were used to estimate soil fertility classes. Leaf contents of N, P, K, Ca, and Mg were plotted with soil contents of OM, P, K+, Ca2+, and Mg2+. Using the Quadrant Diagram of the plant-soil Relationship (QDpsR) method, horizontal and vertical lines were drawn separating the cloud of points in four quadrants. With the points at the quadrants III and I, regression equations were fitted. To obtain foliar sufficiency ranges, soil values of critical and optimal levels of OM, P, K+, Ca2+, and Mg2+, obtained by BL, were substituted in the equations generated by the QDpsR method. The appropriate soil content ranges determined by BL for productivity of 47.7 m3 ha-1 yr-1 were: 24.75-38.28 g kg-1 of OM, 8.5-14.6 mg dm-3 of P, 100.0-150.35 mg dm-3 of K+, 0.77-1.47 cmolc dm-3 of Ca2+, and 0.25-0.43 cmolc dm-3 of Mg2+. Leaf content ranges determined by QDpsR are: 19.4-21.3 g kg-1 of N, 1.0-1.2 g kg-1 of P, 8.5-10.6 g kg-1 of K, 4.8-6.1 g kg-1 of Ca, and 1.9-2.4 g kg-1 of Mg. The critical levels of nutrients in the soil, obtained by the BL method, and the leaf sufficiency ranges, obtained using the QDpsR method, are similar to those existing in the literature. This indicates that this methodology is reliable in establishing standards and that the critical levels obtained can be used to improve the recommendation of fertilizers for eucalyptus.

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ABSTRACT Discussions on desertification frequently highlight soil erosion as a striking feature of this phenomenon. In particular, the high spatial density of gullies represents a strong indication of the formation of desertification hotspots. In this study, through field activities and Monte Carlo simulations, we estimated the volume of soil loss by linear erosion on the slopes of the middle course of the Salitre river in the North of Bahia State. This estimative contributes to the recognition of a desertification process in the studied local. The lengths of the gullies and rills, visible through high-spatial-resolution satellite images, were vectorized. The width and depth of the Linear Erosion Features (LEFs) were measured through field study and recorded via geoprocessing. Statistical treatment was applied to the data to indicate the probability of occurrence of the width and depth classes. Subsequently, the Monte Carlo simulation was used to indicate the volume of soil removed from the slopes by the linear erosion process. Several ramified systems of LEFs are identified and mapped. Monte Carlo simulation fits the measured data well. Estimates indicate that linear erosion event eroded approximately 450,000 m3 of soil in an area of 2,000 hectares, which indicates extreme land degradation.

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ABSTRACT Soils with a long-term history of animal manure application exhibit higher residual effects of nitrogen (N) in soil and can affect the efficiency with which N will be used. This study aimed to evaluate how the immediate and residual effect of 16 applications of animal manure reflects on yields of black oat and corn rotation system, as well as N use efficiency. The study was carried out in no-tillage from 2004 to 2016 in Brazil. The treatments were pig slurry (PS), dairy slurry (DS), pig deep-litter (PL), mineral fertilizer (MF), and control (C). Prior to the sowing of black oat, in which 16 animal manure applications had already been made, an area of the soil was delimited where the treatments were not applied. This area was referred to as unfertilized (U) soil. Applications were carried out in the remaining area and were referred to as fertilized (F) soil. The highest dry matter yield and N accumulation in black oat and corn were found in F soils treated with DS and PL, respectively. In corn, the highest grain yield and N accumulation in grains were found with DS and PS. In U soil, the 16 applications (of DS especially) resulted in yields and N accumulation greater than the control and MF, but lower than those in F. The highest N use efficiency was found with DS. The history of animal manure applications was not enough to rule out additional applications in the following years.

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ABSTRACT In Brazil, empirical models are traditionally used to determine lime requirement (LR), but their reliability is doubtful in most cases, since they can lead to under- or overestimation of LR for different soil types. In this study, the most critical characteristics influencing LR were selected to develop reliable models for predicting LR that raise soil pH to optimum values for crop production in Brazil. Soil samples (n = 22) with varying proportions of clay (5-88 %) and organic matter (OM) levels (3.78-79.35 g kg-1) were used to develop the models. Organic matter and potential acidity (HAl) combined with ΔpH [target pH(H2O) - initial pH(H2O)] were the best predictor variables for estimating LR. Four models were developed (OMpH5.8, OMpH6.0, HAlpH5.8, and HAlpH6.0) for estimating LR to attain target pH values of 5.8 or 6.0 with reasonably high prediction performance (0.758≤ R2 ≤0.886). An algorithm was further developed for selecting the LR to be recommended among those estimated by the models. The proposed algorithm enables to select the minimum LR that ensure the adequate supply of Ca and Mg to plants and does not exceed the levels of soil HAl, thus preventing excessive pH increase. The new predictive models were less sensitive to predict LR high enough to meet Ca2+ and Mg2+ requirements of plants in soils containing levels of HAl lower than 5 cmolc dm-3 and OM lower than 40 g kg-1. However, they ensured an adequate supply of Ca2+ and Mg2+ to plants and avoided the overestimation of LR for most soils used in this research. Validation via an independent dataset (n = 100 samples) confirmed the good predictive performance of the models across a wide range of soil types. In summary, the proposed models can be used as good alternatives to traditional methods for predicting LR for a great variety of Brazilian soils. Further, they are versatile and may be easily deployed in soil testing laboratories, since soil pH, OM, and HAl are characteristics determined in routine analysis.

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ABSTRACT Wind erosion is the main problem that arid lands in northern Mexico are facing. Quantification of this phenomenon is crucial for planning purposes and to scale its impact. The challenge is to assess the problem under limited availability of climatic information. This study aimed to identify potential areas of dust emissions in an arid zone of Northern Mexico. Wind direction and intensity were characterized through a robust index that involves rainfall and evaporation as well as the climatic factor of the general wind erosion equation. A method for assessing the likelihood of dust emission associated with wind erosion was applied. Data from twelve weather stations within the region of the study was analyzed. The variables considered were wind velocity and direction, temperature, and precipitation. A wind rose of wind direction and intensity was obtained. Results showed that the Thornthwaite’s method for computing the Soil Moisture Index (SMI) is a good approach when computing the climatic factor C of the general function of the potential average annual soil loss. Given the lack of local evaporation data, the precipitation-evaporation ratio PE for each weather station was computed as an intermediate step towards the computation of C. Three of the analyzed climatic stations had intermediate C values (36-71 %) in the scale of wind erosion climatic factor. The wind velocities registered in these climatic stations ranged from 15 to 30 km h -1 . The magnitude-frequency analysis of the PE parameter for the stations showed the differences in rainfall and evaporation regimes. Dust pollution prone areas were identified, showing areas where conservation strategies should be directed.

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ABSTRACT Establishing sufficiency ranges and critical levels of nutrients are important for a correct evaluation of plant nutrition through leaf diagnosis. This study aimed to propose critical levels and sufficiency ranges of macro and micronutrients based on leaf diagnosis of soybean plants. The database used was generated from 86 samples of the third trifoliate leaf without petiole, collected during the flowering stage from soybean plants of the main cultivars used in the states of Piauí and Maranhão, Northeast region of Brazil. The results of macro and micronutrients and grain yield were used to calculate the critical level by the reduced normal distribution and boundary line methods, the latter was also used to generate the sufficiency ranges. Nutrient levels for 90 % maximum grain yield were considered for the critical level by the reduced normal distribution, and nutrient levels at the upper line of a dispersion diagram were considered for the boundary line method, using the relation between grain yield and nutrient concentration to generate sufficiency ranges for 95 and 99 % maximum grain yields. The critical levels generated by the boundary line method presented a larger number of deficient samples than the reduced normal distribution method, except for boron. The sufficiency ranges generated by the boundary line with 95 % of the maximum grain yield could not diagnose nutrient deficiency, except for copper. The critical levels by the reduced normal distribution and boundary line methods for leaf diagnosis of soybean were 40.2 and 42.1 g kg-1, 3.2 and 3.4 g kg-1, 17.6 and 19.5 g kg-1, 8.7 and 10.3 g kg-1, 4.7 and 4.9 g kg-1, 2.1 and 2.4 g kg-1, 44 and 44 mg kg-1, 5 and 12 mg kg-1, 125 and 145 mg kg-1, 33 and 34 mg kg-1, and 48 and 63 mg kg-1 for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn, respectively. The critical levels by boundary line showed better distribution for leaf diagnosis for excess, deficiency, and adequate nutrient levels. The sufficiency ranges by the boundary line method for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn were 38.6-45.7 g kg-1, 3.1-3.7 g kg-1, 18.3-20.7 g kg-1, 9.4-11.3 g kg-1, 4.4-5.3 g kg-1, 2.1-2.7 g kg-1, 35-53 mg kg-1, 10-14 mg kg-1, 131-159 mg kg-1, 23-46 mg kg-1, and 58-68 mg kg-1, respectively. The reduced normal distribution and boundary line methods allowed the generation of critical levels and sufficiency ranges for leaf diagnosis of soybean. The sufficiency range generated by the boundary line with 95 % maximum grain yield showed no prevalence of diagnosis of nutrient deficiency, except for copper.

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ABSTRACT Vegetation cover and soil management influence the magnitude of soil losses. In the Universal Soil Loss Equation (USLE), cover and management are represented by the C factor, as it is the easiest factor to manage to reduce loss of soil and water in agricultural areas. This study aimed to determine the C factor of a succession of wheat (Triticum aestivum L.) followed by soybean (Glycine max) under conventional tillage, reduced tillage, and no-tillage. For this, data of soil losses obtained in the field, under natural rainfall conditions, in a long-term experiment that lasted for 13 years were used. The cycle of both crops was divided into five stages with different time intervals between winter and summer, which resulted in ten periods per year constituting the succession. The C factor values varied widely among the treatments and the stages during the crop cycle, and they were influenced mainly by the rainfall distribution of the region, growth of the vegetation and soil disturbance level. By the end of the 13 years of experimentation, the C factor of the wheat-soybean succession under conventional tillage was 0.1576, 0.0407 under reduced tillage, and 0.0368 under no-tillage.

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ABSTRACT The overloading of soil with manure or mineral fertilizers enhances phosphorus (P) availability, promoting its loss to water bodies and increasing the risk of eutrophication. In this sense, the establishment of an environmental P threshold is a simple and useful tool to classify soils regards its risk of P losses. Here we propose a P-threshold for soils from the state of Rio Grande do Sul (RS) in Brazil, with the soil clay content as the principal variable of the model. Samples from 20 representative soils of Rio Grande do Sul State were collected in the 0.00-0.10 and 0.10-0.20 m layers. Samples were physically and chemically characterized and incubated with P rates varying from 0 to 100 % of its maximum adsorption capacity. After 20 days of incubation, the P availability was determined in water and Mehlich-1 extractant. We assessed trough segmented linear functions the value of P-Mehlich in which the levels of P water enhance abruptly (i.e., breaking point) to determine the P limit for each soil. Subsequently, the P limit values were linked to the clay content in the sample, adopting the linear equation arising from it as the P-threshold. Adding a safety margin of 20 % to the P-threshold equation, we propose a simplified one “P-threshold = 20 + clay”. Based on the current critical level of P adopted by the regional recommendation in RG, the equation proposed does not limit the production of the most crop species.

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ABSTRACT Through the lack or non-use of conservationist criteria for adequate land use and management, the scarcity of natural resources becomes ever more evident. This study aimed to analyze the origin of the sediments in the Posses catchment, municipality of Extrema, state of Minas Gerais, Brazil, throughout the fingerprinting technique and portable X-ray fluorescence. Samples from soils under agriculture, pasture, and roads; and from the subsoil of theses land uses were taken in a widespread and representative manner from the entire Posses catchment. Lag deposits and river bed sediment samples were collected downstream from the catchment outlet. A total of 45 geochemical elements were analyzed in the samples by a portable X-ray fluorescence device (pXRF). The outlier test, Kruskal-Wallis test, multivariate discriminant analysis, and a mixing model were used to estimate the contribution of each source in relation to the sediments that arrive at the mouth of the catchment. The elements selected as geochemical tracers were Sr, Al2O3, Ba, Rb, Ti, Fe, and Zn, which combined correctly discriminated 81 % of the sediment sources. The largest and smallest proportion of sediment from the Posses catchment outlet comes from rural roads and agriculture, respectively. The contribution of the subsoil was higher for lag deposits or lower for river bed sediments, than the pasture. There was a low degree of uncertainty (<8 %) for predictions made by the model employed. The types of use, selected as potential sediment sources in the Posses catchment, are adequately discriminated through the geochemical tracers quantified through the pXRF. The fingerprinting technique estimates that the contributions to outlet sediments are dominated by rural roads, following by subsoil or pasture (depending on the type of sediment evaluated) and by agriculture. The sediment sampling strategies used in this study provided similar results for the period studied. Our results showed the potential of the fingerprinting technique and the pXRF for use as tools by the program of Payment for Environmental Services in the monitoring of catchment areas.

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ABSTRACT Soil salinity is a major abiotic stress on plant growth in coastal saline soil. The objective of this study was to screen the optimal combination of organic materials with beneficial bacteria for application under real field conditions to improve coastal saline soil. A two-factor pot experiment was carried out with corn in coastal saline soil for 26 days. In the naturally aerobic environment, a split-plot experiment was conducted with different rates of organic materials (organic fertilizer and mushroom residue) and beneficial bacteria (phosphate - and potassium-solubilizing bacteria). The 10 treatments consisted of a control (inactivated bacteria cells and no organic material), and combinations of organic materials (2, 4, and 6 % of the total soil dry weight), respectively, with beneficial bacteria [at 1 × 108, 2 × 108, and 3 × 108 colony-forming units (cfu) plant-1]. The application of 6 % organic material and beneficial bacteria at 3 × 108 cfu plant-1 (F6B3) promoted the highest seedling height, stem diameter, and dry biomass of corn seedlings, which increased by 0.30~26.78 %, 8.70~27.23 %, and 22.13~156.90 %, respectively, compared with the other FB (organic fertilizers and beneficial bacteria) treatments. Compared with all other FB treatments, soil total nitrogen, available phosphorus, and available potassium were increased by 4.78~18.04 %, 8.99~25.59 %, and 0.96~36.25 %, respectively, in F6B3. This treatment decreased soil total salt content by 0.79~12.72 %, compared with the other FB treatments. Based on the comprehensive improvement scores, F6B3 was identified as the best treatment for coastal saline soil. Organic materials combined with beneficial bacteria could improve nutrient availability and reduce salinity of coastal saline soil and promote corn seedling growth. The combined application of 6 % of organic materials with 3×108 cfu plant-1 of beneficial bacteria proved the most effective for coastal saline soil, and is recommended for field application.

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ABSTRACT Waste resulted from the distillation of kayu putih leaves is a problem in almost all kayu putih refineries throughout Indonesia due to its enormous availability and un-utilization. It has potential to be used as an organic fertilizer source due to its nutrient content (macro and micro) which is higher than organic fertilizer from animals. The use of kayu putih waste is useful to complement and increase the efficiency of nitrogen fertilizer in soybean intercropping with kayu putih . This study aimed to determine the optimum values of kayu putih waste and nitrogen fertilizer based on three scenarios: economic, environmental, and eco-environmental. A two-year experiment (2018-2019) was carried out in a central composite design (CCD) with two replications as the response surface methodology (RSM) at the Menggoran Forest Resort, Playen District, Yogyakarta Forest Management, Indonesia. The treatments consist of biochar and compost levels made from kayu putih waste (0, 2.5, and 5.0 t ha-1) and nitrogen fertilizer levels supplied by ammonium sulfate (0, 50, and 100 kg ha-1) as independent variables. The observations conducted on nitrate reductase activity (NRA), total chlorophyll (TC), leaf photosynthesis rate (LPR), nitrogen loss (NL), nitrogen use efficiency (NUE), and seed yield (SY). The response variables were fitted in a full quadratic polynomial model. The results showed that the resource-based on the eco-environmental scenarios was the most favorable cropping strategy for the soybean production intercropping with kayu putih with the optimum value of 2.890 t ha-1 of biochar, 2.27 t ha-1 of compost, and 67.85 kg ha-1 of ammonium sulfate. This recommendation can reduce the use of ammonium sulfate by 32.15 % and increase of NRA, TC, LPR, NL, NUE, and SY by 12.96, 2.80, 17.18, 21.66, 7.23, and 17.29 %, respectively, compared to the single application of ammonium sulfate fertilizer.

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ABSTRACT Sugarcane is one of the first activities of economic importance in Brazil. The understanding of the nutritional dynamics at different phenological stages of the sugarcane crop with the use of nitrogen-fixing bacteria has been one of the alternatives to decrease fertilizer consumption and increasing plant production. This study aimed to assess the morphophysiological attributes in the initial growth and nutrition of two sugarcane varieties inoculated with strains of diazotrophic bacteria, individually and in an association, in a greenhouse. The experimental design was a randomized block design in a 2 × 8 factorial arrangement with two cultivars (Co 1341-76 and RB 867515) and eight treatments consisting of bacteria inoculated individually with BR 11140T (Azospirillum amazonense), BR 11175T (Herbaspirillum seropedicae), BR 11192T (Herbaspirillum rubrisubalbicans), BR 11281T (Gluconacetobacter diazotrophicus), and BR 11366T (Burkholderia tropica), inoculation associated with the studied bacteria, N fertilization with 120 kg ha-1 of N, and absolute control without inoculation and nitrogen fertilization. Plants were conducted for 75 days after germination, and biometric variables and nutrient accumulation were measured. The sprouting rate index and root fresh matter were significant for inoculation (p<0.01). Inoculation with the strains BR 11192T (H. rubrisubalbicans), BR 11281T (G. diazotrophicus), and RB 11366T (B. tropica) showed the best results for root fresh matter regardless of the cultivar. The strains RB 11366T (B. tropica), BR 11192T (H. rubrisubalbicans), and BR 11175T (H. seropedicae) stood out regarding the sprouting rate index. Inoculation showed a significant effect for stem diameter (p<0.01), especially the strains BR 11140T (A. amazonense) and RB 11366T (B. tropica). All inoculations were efficient for the biometric variable related to leaf length. Nitrogen, Fe, and Zn contents showed a significant effect of the interaction between cultivars and inoculation. The inoculation with the strain RB 11366T (B. tropica), total N fertilization, followed by the other inoculations and the control stood out compared to the cultivar Co 1341-76 within the factor inoculation, indicating that the association of this strain with the cultivar Co 1341-76 is more efficient regarding the recommended commercial N dose for sugarcane. The cultivars Co 1341-76 and RB 867515 responded positively to the individual inoculation of strains of diazotrophic bacteria. The strains promoted improvements in some morphological and/or nutritional attributes of sugarcane plants. The strain B. tropica showed the best interaction with the tested cultivars for the biological N fixation, resulting in gains of biomass productivity and nutrient contents when not inoculated.

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ABSTRACT Histosols provide several ecosystem services, related mainly to their reserves of carbon and nitrogen. Management practices in these soils can increase the mineralization of organic matter and contribute to the emission of greenhouse gases. This study aimed to investigate the effect of tillage with plowing and drainage on Histosol properties in three land use systems located in the municipality of Rio de Janeiro, Brazil. Three areas subjected to different land use systems over the last twenty years were chosen: Area 1, secondary forest with natural regeneration; Area 2, conventional tillage of cassava with plowing; and Area 3, intercropped coconut + cassava with an artificial drainage system. The chemical characterization, von Post scale of organic matter decomposition, percentage of rubbed fiber, organic matter, percentage of mineral material, bulk density, electrical conductivity, soluble phosphate, total organic carbon (TOC) and nitrogen (NT), organic carbon fractions, and C and N stocks were analyzed. Our results showed the critical, nearly irreversible effects of agricultural practices comprising drainage and plowing of the soil. Over twenty years, in Area 2, the TOC and NT values decreased by 33 and 20 %, respectively in the histic horizon, and by about 17 and 8 %, respectively in the gley horizon. In Area 3, the TOC and NT values decreased by 31 and 18 %, respectively, in the histic horizon, and by 27 and 21 % in the gley horizon. Our findings also showed that the loss of C is related to the labile organic carbon, which is more sensitive to environmental changes, even at deeper depths. The plowing of the soil decreases the organic matter content due to the accelerated oxidation of organic matter, increasing the bulk density. Drainage, besides the loss of organic matter by subsidence, promotes the sulfidization of the soil with a high content of SO42-, due to the oxidation of soil materials containing sulfides.

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ABSTRACT The two main bottlenecks for a successful phytoremediation program are the metal availability in soil and the metal uptake and transfer to shoots of high biomass plants. Several agronomical practices have been tested to boost the bioavailability of metals in soils and accumulation in plants. Here we assessed the feasibility of plant-growth-promoting bacteria (PGPB) isolated from a site contaminated by gold ore processing activities to assist the phytoremediation of As, Cd, and Pb by Sorghum bicolor and mitigate the metal toxicity in plants. The bacteria Kluyvera intermedia, Klebsiella oxytoca, and Citrobacter murliniae were evaluated in single, double, and triple inoculations. They are regarded as metal resistant and were isolated from the rhizosphere of species naturally growing on the metal contaminated site. The treatments comprised two soils (contaminated and non-contaminated) and single (K. intermedia, K. oxytoca, or C. murliniae) or multiple inoculations (K. intermedia + K. oxytoca; K. intermedia + C. murliniae; K. oxytoca + C. murliniae; K. intermedia + K. oxytoca + C. murliniae). Plants were grown for 42 days after inoculation. The results showed that the PGPB K. oxytoca and the combination of K. intermedia + K. oxytoca and K. intermedia + C. murliniae were able to mitigate the metal toxicity in the contaminated soil and hence increase the shoot biomass, with implications to the effectiveness of phytoextraction. The sorghum ability to translocate Cd to shoots in the contaminated soil was enhanced through the single inoculation with K. oxytoca, C. murliniae, and K. oxytoca, as well as by the joint-inoculation with K. oxytoca + C. murliniae, and K. intermedia + K. oxytoca + C. murliniae. Higher accumulation of metals in shoots is a crucial factor in successful phytoextraction. Arsenic and Pb, on the other hand, had their uptake and concentration in roots stimulated by the inoculation. Therefore, regarding these two metals, phytostabilization programs could benefit from the use of the bacteria studied here.

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ABSTRACT Foliar fertilization can be recommended to treat boron (B) deficiency in coffee and cotton. Considering that B foliar fertilizers with polyol-boron complexes can affect B uptake and mobility differently within the plant, and coffee and cotton have different cuticles and stomata density, a differential response would be expected. We aimed to study the foliar application of boric acid combined with sorbitol on B uptake and translocation in cotton and coffee. Green-house grown plants received B as boric acid and a sorbitol-monoethanolamine complex and were sampled up to 96 h after application. Boron absorption was fast, reaching 60 and 80 % in cotton and coffee 96 h after application, respectively. Uptake rates and total B absorption were similar for the fertilizers. The proportion of B taken up by coffee is greater than by cotton likely because of the greater stomata density in coffee and less likely due to the higher amount of wax in cotton cuticle. Boron remobilization is higher in coffee as compared with cotton. Sorbitol seems to increase B transport in the transpiratory stream of cotton, but impairs remobilization in the phloem since B translocation to roots is decreased in both cotton and coffee.

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ABSTRACT Hydrosedimentological modeling is a useful tool to predict the water dynamic in a basin and for water resources management. This study aimed to i) evaluate the ability of Soil and Water Assessment Tool (SWAT) to model sediment load and continuous monthly streamflow in the Mortes River Basin (MRB) in Southeastern Brazil; ii) estimate the sediment yield spatially distributed by sub-basins; iii) estimate the sediment load export to the Funil Hydroelectric Power Plant reservoir (FHPP), located in the MRB outlet. For the sensitivity analysis, calibration, and uncertainty analysis of the model, a semi-automatic calibration in SWAT-CUP version 5.1.6 software with the “Sequential Uncertainty Fitting” algorithm was used. To evaluate the ability of SWAT to reproduce the continuous MRB monthly streamflow and sediment load, statistical indexes, and graphical analyses were used to compare the simulated and observed data. For the sediment evaluation, a spatial and temporal comparison of sediment yield maps was used as well as the sediment yield observed in sub-basins, aiming to identify the areas with a more significant contribution to the sediment generation in the basin. The results demonstrated that SWAT performed satisfactorily in simulating both monthly sediment load and streamflow. For discharge calibration, 99 % of the measured data were bracketed by the 95 % prediction uncertainty (95PPU), and for validation, 97 % of the data were bracketed by the 95PPU, which indicates proper bracketing of the measured data within model prediction uncertainty. Uncertainty analysis indicated that 95PPU could capture 78 % of the sediment loads measured during the calibration and 72 % of the measured data during the validation period at MRB. The hydrologic response unit with pasture and Argissolos (Ultisols), Neossolos Litólicos (Entisols), and Cambissolos (Inceptisols) combined with undulated relief were the main areas responsible for the highest sediment contributions. The sediment load delivered to the reservoir from its filling 2002 to 2015 was estimated in 6,682,704 m3 (16,706,761 Mg) (density of 2.5-Mg m-3) which value corresponded to 2.6 % of storage capacity (water plus sediment) in 14 years. These results are strategic since to become feasible identifying priority areas for soil and water conservation practices as well as useful information for water resources planning and management in the studied basin.

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ABSTRACT The drawing of maps of soil quality at a large scale is increasingly being more useful to land planners and stakeholders. Nevertheless, it involves different methodological steps from the description of soil profiles in the field until the regional mapping of integrative soil quality index (IQI) values. The development of proper scoring functions is a paramount task for the calculation of these IQI values since every parameter needs to be standardized accordingly and weighting factors are usually estimated by multivariate techniques. The main goal of this study was to map soil quality in the Spanish region of Extremadura (commonly known by its rangelands called dehesas). To do that, i) we gathered information from 194 soil profiles described throughout the region, ii) we calculated the weighting factors of ten meaningful parameters used as indicators by using multivariate techniques (Principal Component Analysis, PCA; and Analytic Hierarchy Process, AHP), and iii) we developed standard scoring functions (SSFs) that represent the singularity of every variable (less is better, more is better). We established upper and lower limits for standardizing the values of each indicator properly. Regarding weighting factors, soil texture was highlighted by the PCA and nutrients by the AHP. Once IQI values were calculated, two regional maps of soil quality were drawn by using interpolation methods (ordinary kriging). The IQI maps showed remarkable spatial differences in soil quality presumably induced by land management. We conclude this methodology could be useful and we encourage other colleagues to test its effectiveness in places where soil data are available.

Resumo em Inglês:

ABSTRACT Gully erosion is a severe way of land degradation. Gullies threaten the sustainability of agro-ecosystems, causing quantitative and qualitative reduction of groundwater, farmland productivity, and waterways sedimentation. Since the gully development on the surface begins with water flow and sheet erosion, accurate monitoring of the erosive processes in a gully system and its quantification is key for the development of effective strategies to control soil erosion in gullies. Here, we demonstrate the first use of unmanned aerial vehicle (UAV) and structure-from-motion/multiview-stereo photogrammetry to evaluate the relative contribution of the different types of erosion (sheet, rill, and gully sidewall) in the gully development. A gully located at Lavras, Brazil, was surveyed using a UAV equipped with a RGB camera. The Precision Maps (PM) variant of the Multiscale Model to Model Cloud Compare (M3C2) algorithm was used to calculate spatial changes in the soil surface topography and to quantify the volumes of sediments lost and gained in the gully system. The point clouds showed root mean square errors of order ~ 3 mm on xyz on check points. The spatial variation of precision along the gully ranged from 0.006 to 0.276 m, considering the M3C2-PM uncertainty values. The results revealed that the main source of sediment in the gully studied was due to the mass movement processes. Rills and laminar erosions contributed 8 and 3 %, respectively, to the total sediment yield, while the mass movements corresponded with most of the sediment generation in the gully. Of the total sediment produced in the system, only 24 % was stored in the gully, indicating its high activity and instability. For the first time, the sediment sources of a gully were quantified remotely and with millimetric precision. The UAV photogrammetry generated high-resolution measurements, allowing evaluation of the contribution of sheet erosion in the generation of sediment of the gully. This opens up new possibilities in the studies involving the dynamics of gullies, since the understanding of the spatial and temporal behaviour of the erosive processes are important in the development of control strategies and monitoring of the evolution of a gullies complex.

Resumo em Inglês:

ABSTRACT The optimal soil pH for most annual crops in Brazil varies between 5.7 and 6.0. Numerous methods have been developed for estimating lime requirement (LR), but they vary widely in their predictions and fail to raise pH to desired values for optimum crop production in the highly weathered soils of Brazil. The objectives of this study were to (i) compare seven traditional methods for estimating LR in Brazilian soils; (ii) assess the effects of LR predicted by these methods on soil-acidity related properties, and (iii) determine if these methods are predicting LR to attain target pH values of 5.8 and 6.0, which are within the pH range recommended to optimize crop yields. The traditional LR methods evaluated in this study are based on the following criteria: exchangeable acidity (EA), base saturation (BSAT), exchangeable acidity along with Ca2+ and Mg2+ as proposed by the 4th (MG4A) and 5th (MG5A) Approximations to the Minas Gerais State, SMP soil-buffer pH (SMP), potential acidity (PA), and soil pH along with organic matter (pHOM). These methods were compared with the standard incubation method using correlation-regression analysis and, alternatively, the identity test designed for assessing equivalence between methods. Representative agricultural soils (n = 22) were incubated for 60 days with incremental amounts of lime determined by the tested methods. On average, LR predictions differed among methods, and increased in the following order: EA < BSAT ≈ MG5A ≤ MG4A ≈ SMP ≤ PA < pHOM. Suitable changes in soil pH, exchangeable acidity, potential acidity, base saturation, and Ca2+ and Mg2+ were achieved upon application of LR estimated by all methods except the EA and pHMO, which resulted in undesirable soil acidity characteristics. All methods evaluated in this study were unable to predict LR for attaining target pH values of 5.8 and 6.0 as revealed by the identity test, even though they were moderate to strongly correlated with the standard incubation method as indicated by the correlation-regression analysis. Further research should focus on the development of reliable methods for predicting LR to attain desired pH values and consequently maximize crop production on Brazilian soils.

Resumo em Inglês:

ABSTRACT Soil management and crop rotation are key factors in controlling the accumulation of C and N in the soil profile, but their long-term effect remains poorly understood for deep soil layers, especially in subtropical conditions. Using a long-term experiment (26-years), this study aimed to evaluate the effect of different soil management systems associated with different winter cover crops on C and N accumulation in a very clayey (72 % clay) soil up to 1 m deep. Two tillage systems [conventional tillage (CT) and no-tillage (NT)] were cultivated with eight winter cover crops (black oat, rye, common vetch, hairy vetch, oilseed radish, wheat, blue lupine, and fallow) in a subtropical Oxisol from Southern Brazil. Soil samples were taken in eight soil layers up to 1.00 m soil depth after 26 years of experiment and, also from an adjacent native forest. After forest clearing, the C stock in the 0.00-0.20 m soil layer was reduced by 45 % in only 10 years (from 1976 to 1986) of soil tillage. Twenty-six years after the beginning of the experiment, C and N stock in 0.00-0.20 m soil layer were 13 and 20 % higher in NT compared to CT, with the greatest differences in C and N content observed in the 0.00-0.05 m layer. When associated with winter cover crops, NT accumulated 0.6 and 0.06 Mg ha-1 yr-1 more C and N than CT with winter fallow in the 0.00-0.20 m soil layer. No-tillage and CT recovered 95 and 83 %, respectively, of the C stock found in the 0.00-0.20 m layer from the native forest. However, in the 0.00-1.00 m soil layer, the positive effect of NT on soil C accumulation compared to CT was diluted, and no clear effect of NT was verified. Moreover, no difference in winter cover crops on soil C and N stocks were observed in all soil layers, possibly due to their similar residues input (3.3-4.9 Mg ha-1 yr-1). No-tillage associated with high biomass input through winter cover crops promoted a faster recovery of soil C and N stock than in CT and, therefore, is an efficient tool to improve soil C and N accumulation even in Oxisols with high clay content.

Resumo em Inglês:

ABSTRACT The application of organic composts derived from animal husbandry or agro-industry is a promising option to improve nutrient cycling and supply of soils and, consequently, forage production. The objective of this study was to evaluate the soil chemical properties and the nutritional state of elephant grass in response to rates of organic fertilizer composted from the waste of small ruminant production and slaughter systems. The experiment was conducted on a Fluvisol of a forage field with elephant grass var. Cameroon, and was arranged in a randomized block design with split-plots with repeated measures over time. Six rates of organic compost (0, 13.3, 26.6, 39.9, 52.3, and 79.8 t ha-1, in plots) and an additional treatment with mineral fertilizers were evaluated in four growth periods (60, 120, 180, and 240 days, in subplots) with four replications, resulting in a total of 28 plots. Soil fertility was evaluated after the fourth growth period, while leaf analysis was determined in every 60-day period. The increasing rates of organic compost increased the concentrations of OM, NH4+, NO3–, NH4+ + NO3–, P and base saturation, while the H+Al values decreased and the N and P contents increased in the plants. Compared with mineral fertilization, soil inorganic nitrogen and phosphorus increased by 34 and 97 % in response to the application of organic compost. In response to the application of organic compost, the leaf contents of all studied nutrients remained adequate in all studied periods, except for the macronutrient N and micronutrient Mn.

Resumo em Inglês:

ABSTRACT Rational management of spontaneous plants is an alternative for increasing productivity in tree crops. This study aimed to evaluate the impact of management systems between rows and under the canopy of early dwarf cashew trees on the soil chemical properties and light-fraction organic matter and cashew root systems; we also evaluated the nutrient inputs from the spontaneous plants phytomass and cashew leaves deposited on an Arenic Kandiustults. The management systems under study were disc harrowing (DH) and mechanical mowing (MM) between rows, both with clearing under the cashew canopy (crowning), and herbicide (HERB) between the rows and under the canopy (without crowning). Soil and plant samples (leaves, stems, and roots) were collected at three points: under the canopy, at the canopy projected limit, and between the rows of cashew plants, all after seven years of conducting the experiment. Soil samples collected at the layers of 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m were evaluated for total organic carbon, light-fraction organic matter, and chemical attributes. Dry matter, Na, Ca, Mg, N, P, and K were determined in the spontaneous-plant phytomass from under the canopy, at the canopy projected limit, and between the rows. Results showed that between rows of cashew trees there are higher phytomass input and increases in the light fraction of organic matter, pH and Mg2+ in the soil in the treatment MM. Not removing crop residues or spontaneous plants by crowning promoted accumulation of organic material and higher contents of nutrients under the canopy. The management of spontaneous plants and also soil surface under the canopy of the cashew plants had a great influence on productivity. The crowning, used in MM and DH, led to lower productivity, 1,171.87 and 594.97 kg ha-1, respectively, when compared with the absence of crowning (HERB), which resulted in productivity of 1,363.80 kg ha-1. The practice of crowning is not recommended for soil management systems in dwarf cashew crops.

Resumo em Inglês:

ABSTRACT The use of new technologies, the development of new software, and the advances in the machines ability to process data have brought a new perspective to soil science and especially to pedology, with the advent of digital soil mapping (DSM). To meet the demand for soil surveys in Brazil, it will be necessary to popularize the techniques used in DSM. To identify and map the soil to generate maps of land use capability, we proposed a theoretical and practical course focused on the training in DSM for professionals involved in the management of land resources. The methodology was divided into five modules: I. Introduction to pedology, soil-landscape relationship, soil survey and soil classification (theory); II. Identification of soils in the field and study of the soil-landscape relationship (practice); III. Digital soil mapping and geographic information system (theory) and obtaining environmental covariates (practice); IV. Statistical learners and quality measures of spatial predictions (theory) and spatial pseudo-sampling (practice); V. Database organization, calibration, and validation of predictive models (practice). Results such as the average level of confidence of the participants in the soil classification, as well as the number of pseudo-sampling classified by the participants, chosen statistical apprentice, environmental covariables used, and overall accuracy, were influenced by the participants level of knowledge regarding DSM soils and techniques. The structure, focus, and time of each module should be based on the participants needs. It is suggested that a survey should be carried out to consider the level of knowledge in relation to the topics addressed in DSM before the preparation and execution of the course. The contribution of individual experiences showed the importance of multidisciplinarity in the teaching-learning process because it is a technique that involves soil knowledge, statistics, and mathematics applied to geoinformation science to understand soil variability in the landscape. The practical classes were fundamental, enabling an approximation of the content studied with the participants’ reality and consolidation of the acquired knowledge. In general, the course was well evaluated by the participants regarding the contents covered and practical field training and laboratory geoprocessing, who reported that the practical classes were fundamental for the appropriation of knowledge in DSM. This course could be a model for the PronaSolos, which tend to have heterogeneous groups of participants, being necessary to plan specific protocols to tend the particularity.